Add notification platform setup guides to README

Made-with: Cursor

.dockerignore

@@ -0,0 +1,3 @@
+.git
+node_modules
+.DS_Store

.editorconfig

@@ -0,0 +1,15 @@
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[Makefile]
+indent_style = tab
+
+[*.go]
+indent_style = tab

.gitea/workflows/check.yml

@@ -0,0 +1,9 @@
+name: check
+on: [push]
+jobs:
+    check:
+        runs-on: ubuntu-latest
+        steps:
+            # actions/checkout v4.2.2, 2026-02-22
+            - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+            - run: docker build .

.gitignore

@@ -0,0 +1,45 @@
+# OS
+.DS_Store
+Thumbs.db
+
+# Editors
+*.swp
+*.swo
+*~
+*.bak
+.idea/
+.vscode/
+*.sublime-*
+
+# Node
+node_modules/
+
+# Environment / secrets
+.env
+.env.*
+*.pem
+*.key
+
+# Go build artifacts
+backend-go/bin/
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+*.test
+*.out
+vendor/
+tmp/
+
+# Frontend build output
+frontend/dist/
+frontend/build/
+frontend/.vite/
+
+# Prompts directory (local tooling, not part of the project)
+Prompts/
+
+# Logs
+*.log
+.claude

.prettierignore

@@ -0,0 +1,7 @@
+node_modules/
+frontend/dist/
+frontend/build/
+backend-go/bin/
+*.lock
+Prompts/
+.claude/

.prettierrc

@@ -0,0 +1,4 @@
+{
+    "tabWidth": 4,
+    "proseWrap": "always"
+}

Dockerfile

@@ -0,0 +1,22 @@
+# syntax=docker/dockerfile:1
+
+# golang:1.24-alpine, 2025-02-28
+FROM golang:1.24-alpine@sha256:8bee1901f1e530bfb4a7850aa7a479d17ae3a18beb6e09064ed54cfd245b7191
+
+# Install system dependencies: Node.js, npm, make, git
+RUN apk add --no-cache nodejs npm make git
+
+# Install golangci-lint at a pinned commit hash
+# golangci-lint v2.10.1 (2025-02-17), commit 5d1e709b7be35cb2025444e19de266b056b7b7ee
+RUN GOBIN=/usr/local/bin go install \
+    github.com/golangci/golangci-lint/cmd/golangci-lint@5d1e709b7be35cb2025444e19de266b056b7b7ee
+
+WORKDIR /app
+
+COPY . .
+
+# Install frontend dependencies
+RUN cd frontend && npm ci
+
+# Run all checks — build fails if the branch is not green
+RUN make check

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Steven Jannette
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Makefile

@@ -0,0 +1,90 @@
+.PHONY: test lint fmt fmt-check check docker hooks build run dev clean \
+        test-go test-js lint-go lint-js fmt-go fmt-js fmt-check-go fmt-check-js \
+        build-go build-js
+
+GODIR    := backend-go
+JSDIR    := frontend
+PRETTIER := $(JSDIR)/node_modules/.bin/prettier
+
+# ── required targets ────────────────────────────────────────────
+
+all: check
+
+check: test lint fmt-check
+
+test: test-go test-js
+
+lint: lint-go lint-js
+
+fmt: fmt-go fmt-js
+
+fmt-check: fmt-check-go fmt-check-js
+
+# ── go ──────────────────────────────────────────────────────────
+
+test-go:
+	cd $(GODIR) && go test -timeout 30s ./...
+
+lint-go:
+	cd $(GODIR) && golangci-lint run ./...
+
+fmt-go:
+	cd $(GODIR) && gofmt -w .
+
+fmt-check-go:
+	@diff=$$(cd $(GODIR) && gofmt -l .); \
+	if [ -n "$$diff" ]; then \
+		echo "Go files need formatting:"; \
+		echo "$$diff"; \
+		exit 1; \
+	fi
+
+# ── js / frontend ───────────────────────────────────────────────
+
+test-js:
+	cd $(JSDIR) && npm test
+
+lint-js:
+	$(PRETTIER) --check '**/*.{js,jsx,ts,tsx,css,md,json}'
+
+fmt-js:
+	$(PRETTIER) --write '**/*.{js,jsx,ts,tsx,css,md,json}'
+
+fmt-check-js:
+	$(PRETTIER) --check '**/*.{js,jsx,ts,tsx,css,md,json}'
+
+# ── build ───────────────────────────────────────────────────────
+
+build: build-go build-js
+
+build-go:
+	cd $(GODIR) && go build -o bin/api ./cmd/api
+	cd $(GODIR) && go build -o bin/poller ./cmd/poller
+
+build-js:
+	cd $(JSDIR) && npm run build
+
+# ── dev / run ───────────────────────────────────────────────────
+
+run:
+	cd $(GODIR) && go run ./cmd/api
+
+dev:
+	cd $(GODIR) && go run ./cmd/api
+
+# ── docker ──────────────────────────────────────────────────────
+
+docker:
+	docker build -t koin-ping .
+
+# ── hooks ───────────────────────────────────────────────────────
+
+hooks:
+	printf '#!/bin/sh\nmake check\n' > .git/hooks/pre-commit
+	chmod +x .git/hooks/pre-commit
+
+# ── clean ───────────────────────────────────────────────────────
+
+clean:
+	rm -rf $(GODIR)/bin/
+	rm -rf $(JSDIR)/dist/

README.md

@@ -1,95 +1,230 @@
 # Koin Ping
-
 A lightweight on-chain monitoring and alerting system designed to give users situational awareness over blockchain addresses they care about.
 
-## Overview
+# Overview
 
-Koin Ping is designed to reliably observe on-chain activity and notify users when predefined conditions are met. It does not execute transactions, manage wallets, or speculate on prices.
+Koin Ping observes on-chain activity and notifies users when predefined conditions are met. It does not execute transactions, manage wallets, or speculate on prices.
 
-## Project Structure
-
-```
-koin_ping/
-├── backend/                  # Node.js + Express + PostgreSQL backend
-│   ├── api/                 # API endpoints and server configuration
-│   ├── poller/              # Blockchain polling logic
-│   ├── alerts/              # Alert evaluation and management
-│   ├── notifications/       # Notification delivery system
-│   ├── domain/              # Domain models and business logic
-│   ├── infra/               # Infrastructure (database, external services)
-│   └── shared/              # Shared utilities and helpers
-│
-└── frontend/                 # React + Vite frontend
-    ├── public/              # Static assets
-    └── src/
-        ├── api/             # Frontend API calls to backend
-        ├── components/      # Reusable UI components
-        ├── pages/           # Top-level pages (views)
-        └── utils/           # Utility functions
-
-```
-
-## Tech Stack
-
-### Backend
-- **Runtime:** Node.js
-- **Framework:** Express
-- **Database:** PostgreSQL
-- **Key Dependencies:** 
-  - `pg` - PostgreSQL client
-  - `dotenv` - Environment variable management
-  - `cors` - CORS middleware
-  - `nodemon` - Development auto-reload
-
-### Frontend
-- **Framework:** React 19
-- **Build Tool:** Vite
-- **Language:** JavaScript/TypeScript (mixed)
-- **Type Checking:** TypeScript
 
 ## Getting Started
 
 ### Prerequisites
-- Node.js (v18 or higher recommended)
-- PostgreSQL database
-- npm or yarn
 
-### Backend Setup
+- Go 1.24+
+- Node.js 18+ and npm (or yarn — preferred per repo policy)
+- PostgreSQL 15+
+- `golangci-lint` v2 (for `make lint`)
 
-1. Navigate to the backend directory:
-   ```bash
-   cd backend
+### Setup
+
+```bash
+# Clone and enter the repo
+git clone <repo-url>
+cd koin_ping_0.2.0
+
+# Install pre-commit hook
+make hooks
+
+# Install frontend dependencies
+cd frontend && npm install && cd ..
+
+# Copy and fill in environment variables
+cp backend-go/.env.example backend-go/.env
+# edit backend-go/.env with your DATABASE_URL, FIREBASE_PROJECT_ID, ETH_RPC_URL
+
+# Run checks (requires golangci-lint)
+make check
+
+# Start the API server
+make run
+
+# Start the poller (separate terminal)
+cd backend-go && go run ./cmd/poller
+
+# Start the frontend dev server (separate terminal)
+cd frontend && npm run dev
+```
+
+The API listens on `http://localhost:3001` and the frontend on
+`http://localhost:3000` by default.
+
+## Rationale
+
+Crypto users who hold or actively monitor addresses need a lightweight, reliable
+way to know when on-chain activity occurs without polling block explorers
+manually. Koin Ping fills that gap: it watches a set of Ethereum addresses,
+evaluates configurable alert rules (incoming transactions, outgoing
+transactions, large transfers, balance thresholds), and notifies the user
+through Discord webhooks.
+
+## Design
+
+The system is split into two independently deployable processes and one
+frontend:
+
+```
+koin_ping_0.2.0/
+├── backend-go/                # Go monorepo root
+│   ├── cmd/api/               # HTTP REST API server
+│   ├── cmd/poller/            # Blockchain polling daemon
+│   └── internal/
+│       ├── config/            # Environment-based config loading
+│       ├── database/          # pgx connection pool
+│       ├── domain/            # Shared domain types
+│       ├── firebase/          # Firebase auth client
+│       ├── handlers/          # HTTP handler wiring
+│       ├── middleware/         # Auth middleware
+│       ├── models/            # SQL persistence layer
+│       ├── notifications/     # Discord webhook delivery
+│       ├── protocols/ethereum/ # Ethereum JSON-RPC client
+│       ├── services/          # Observer and evaluator business logic
+│       └── wei/               # ETH/Wei conversion utilities
+└── frontend/                  # React + Vite SPA
+    └── src/
+        ├── api/               # Fetch wrappers for the REST API
+        ├── components/        # Reusable UI components
+        ├── contexts/          # React contexts (auth, etc.)
+        ├── firebase/          # Firebase SDK initialization
+        └── pages/             # Top-level route pages
+```
+
+**API server** (`cmd/api`): standard-library `net/http` with Firebase JWT
+authentication middleware. Exposes CRUD endpoints for addresses, alert rules,
+alert events, and notification configuration.
+
+**Poller** (`cmd/poller`): long-running daemon that polls Ethereum via JSON-RPC,
+compares observed transactions against persisted alert rules, fires alert events
+to the database, and dispatches Discord notifications.
+
+**Frontend** (`frontend/`): React 19 SPA built with Vite. Authenticates with
+Firebase, communicates with the API via fetch, and renders the address/alert
+management UI.
+
+## Setting Up Your Alert Platforms
+
+Koin Ping can send real-time alerts to **Telegram**, **Discord**, **Slack**, and **Email**. Each channel is configured per-user through the **Notification Settings** panel on the Alerts page.
+
+Below are step-by-step guides for setting up each platform.
+
+---
+
+### Telegram
+
+To receive alerts via Telegram, you need to create a bot and get your chat ID.
+
+#### 1. Create a Telegram Bot
+
+1. Open Telegram and search for **@BotFather** (look for the blue verified checkmark).
+2. Open the conversation with BotFather and send: `/newbot`
+3. BotFather will ask for a **display name** — enter something like `Koin Ping Alerts`.
+4. BotFather will ask for a **username** — it must end in `bot`, e.g. `MyKoinPingBot`.
+5. BotFather will reply with your **Bot Token** — a string that looks like `123456789:ABCdefGHIjklMNOpqrSTUvwxYZ`. Copy it.
+
+#### 2. Get Your Chat ID
+
+1. In Telegram, search for the bot username you just created and open the chat.
+2. Tap **Start** or send any message (e.g. `hello`).
+3. Open the following URL in your browser, replacing `YOUR_BOT_TOKEN` with the token from step 1:
+
+   ```
+   https://api.telegram.org/botYOUR_BOT_TOKEN/getUpdates
    ```
 
-2. Install dependencies (already done):
-   ```bash
-   npm install
+4. In the JSON response, find the `"chat"` object — the `"id"` field is your **Chat ID** (a numeric value).
+
+   > **Tip:** If the `"result"` array is empty, make sure you sent a message to your bot first, then refresh the page.
+
+#### 3. Save in Koin Ping
+
+1. Go to the **Alerts** page in Koin Ping.
+2. In the **Notification Settings** panel, find the **Telegram** section.
+3. Paste your **Bot Token** and **Chat ID** into the corresponding fields.
+4. Click **Save Settings**.
+5. Click **Test All Channels** to verify — you should receive a test message from your bot in Telegram.
+
+---
+
+### Discord
+
+To receive alerts in a Discord channel, you need to create a webhook.
+
+#### 1. Create a Discord Webhook
+
+1. Open **Discord** and navigate to the server where you want to receive alerts.
+2. Go to the channel you want alerts posted in (or create a new one, e.g. `#koin-alerts`).
+3. Click the **gear icon** next to the channel name to open **Channel Settings**.
+4. Go to **Integrations** > **Webhooks**.
+5. Click **New Webhook**.
+6. Give it a name (e.g. `Koin Ping`) and click **Copy Webhook URL**.
+
+   The URL will look like: `https://discord.com/api/webhooks/123456789/AbCdEfGhIjKl...`
+
+#### 2. Save in Koin Ping
+
+1. Go to the **Alerts** page in Koin Ping.
+2. In the **Notification Settings** panel, find the **Discord** section.
+3. Paste your **Webhook URL** into the field.
+4. Click **Save Settings**.
+5. Click **Test All Channels** to verify — you should see a test message appear in your Discord channel.
+
+---
+
+### Slack
+
+To receive alerts in a Slack channel, you need to create an Incoming Webhook.
+
+#### 1. Create a Slack App with Incoming Webhooks
+
+1. Go to [https://api.slack.com/apps](https://api.slack.com/apps) and click **Create New App**.
+2. Choose **From scratch**, give it a name (e.g. `Koin Ping`), and select your workspace.
+3. In the app settings, go to **Incoming Webhooks** in the left sidebar.
+4. Toggle **Activate Incoming Webhooks** to **On**.
+5. Click **Add New Webhook to Workspace**.
+6. Select the channel where you want alerts posted (e.g. `#koin-alerts`) and click **Allow**.
+7. Copy the **Webhook URL** — it will start with `https://hooks.slack.com/services/...`
+
+#### 2. Save in Koin Ping
+
+1. Go to the **Alerts** page in Koin Ping.
+2. In the **Notification Settings** panel, find the **Slack** section.
+3. Paste your **Webhook URL** into the field.
+4. Click **Save Settings**.
+5. Click **Test All Channels** to verify — you should see a test message appear in your Slack channel.
+
+---
+
+### Email
+
+Koin Ping sends email alerts and digests via [Resend](https://resend.com). To enable email notifications, the application owner must configure a Resend account and verified sending domain.
+
+#### For Application Owners (Deployment Setup)
+
+1. Create an account at [resend.com](https://resend.com).
+2. Go to [resend.com/domains](https://resend.com/domains) and add your sending domain.
+3. Add the DNS records Resend provides (SPF, DKIM, etc.) to your domain's DNS settings.
+4. Once verified, create an API key at [resend.com/api-keys](https://resend.com/api-keys).
+5. Set the following in your `.env` file:
+
+   ```
+   RESEND_API_KEY=re_your_api_key_here
+   EMAIL_FROM=Your App <alerts@yourdomain.com>
    ```
 
-3. Create a `.env` file (see backend/README.md for required variables)
+6. Restart the API server and poller to pick up the changes.
 
-4. Start the development server:
-   ```bash
-   npm run dev
-   ```
+#### For Users
 
-The backend will run on `http://localhost:3001`
+1. Go to the **Alerts** page in Koin Ping.
+2. In the **Notification Settings** panel, find the **Email** section.
+3. Enter the email address where you want to receive alerts.
+4. Click **Save Settings**.
+5. Click **Verify Email** to receive a confirmation message.
+6. Click **Test All Channels** to verify — you should receive a test alert at your email address.
 
-### Frontend Setup
+## License
 
-1. Navigate to the frontend directory:
-   ```bash
-   cd frontend
-   ```
+MIT. See [LICENSE](LICENSE).
 
-2. Install dependencies (already done):
-   ```bash
-   npm install
-   ```
+## Author
 
-3. Start the development server:
-   ```bash
-   npm run dev
-   ```
-
-The frontend will run on `http://localhost:3000`
+Steven Jannette

REPO_POLICIES.md

@@ -0,0 +1,188 @@
+---
+title: Repository Policies
+last_modified: 2026-02-22
+---
+
+This document covers repository structure, tooling, and workflow standards. Code
+style conventions are in separate documents:
+
+- [Code Styleguide](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/CODE_STYLEGUIDE.md)
+  (general, bash, Docker)
+- [Go](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/CODE_STYLEGUIDE_GO.md)
+- [JavaScript](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/CODE_STYLEGUIDE_JS.md)
+- [Python](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/CODE_STYLEGUIDE_PYTHON.md)
+- [Go HTTP Server Conventions](https://git.eeqj.de/sneak/prompts/raw/branch/main/prompts/GO_HTTP_SERVER_CONVENTIONS.md)
+
+---
+
+- Cross-project documentation (such as this file) must include
+  `last_modified: YYYY-MM-DD` in the YAML front matter so it can be kept in sync
+  with the authoritative source as policies evolve.
+
+- **ALL external references must be pinned by cryptographic hash.** This
+  includes Docker base images, Go modules, npm packages, GitHub Actions, and
+  anything else fetched from a remote source. Version tags (`@v4`, `@latest`,
+  `:3.21`, etc.) are server-mutable and therefore remote code execution
+  vulnerabilities. The ONLY acceptable way to reference an external dependency
+  is by its content hash (Docker `@sha256:...`, Go module hash in `go.sum`, npm
+  integrity hash in lockfile, GitHub Actions `@<commit-sha>`). No exceptions.
+  This also means never `curl | bash` to install tools like pyenv, nvm, rustup,
+  etc. Instead, download a specific release archive from GitHub, verify its hash
+  (hardcoded in the Dockerfile or script), and only then install. Unverified
+  install scripts are arbitrary remote code execution. This is the single most
+  important rule in this document. Double-check every external reference in
+  every file before committing. There are zero exceptions to this rule.
+
+- Every repo with software must have a root `Makefile` with these targets:
+  `make test`, `make lint`, `make fmt` (writes), `make fmt-check` (read-only),
+  `make check` (prereqs: `test`, `lint`, `fmt-check`), `make docker`, and
+  `make hooks` (installs pre-commit hook). A model Makefile is at
+  `https://git.eeqj.de/sneak/prompts/raw/branch/main/Makefile`.
+
+- Always use Makefile targets (`make fmt`, `make test`, `make lint`, etc.)
+  instead of invoking the underlying tools directly. The Makefile is the single
+  source of truth for how these operations are run.
+
+- The Makefile is authoritative documentation for how the repo is used. Beyond
+  the required targets above, it should have targets for every common operation:
+  running a local development server (`make run`, `make dev`), re-initializing
+  or migrating the database (`make db-reset`, `make migrate`), building
+  artifacts (`make build`), generating code, seeding data, or anything else a
+  developer would do regularly. If someone checks out the repo and types
+  `make<tab>`, they should see every meaningful operation available. A new
+  contributor should be able to understand the entire development workflow by
+  reading the Makefile.
+
+- Every repo should have a `Dockerfile`. All Dockerfiles must run `make check`
+  as a build step so the build fails if the branch is not green. For non-server
+  repos, the Dockerfile should bring up a development environment and run
+  `make check`. For server repos, `make check` should run as an early build
+  stage before the final image is assembled.
+
+- Every repo should have a Gitea Actions workflow (`.gitea/workflows/`) that
+  runs `docker build .` on push. Since the Dockerfile already runs `make check`,
+  a successful build implies all checks pass.
+
+- Use platform-standard formatters: `black` for Python, `prettier` for
+  JS/CSS/Markdown/HTML, `go fmt` for Go. Always use default configuration with
+  two exceptions: four-space indents (except Go), and `proseWrap: always` for
+  Markdown (hard-wrap at 80 columns). Documentation and writing repos (Markdown,
+  HTML, CSS) should also have `.prettierrc` and `.prettierignore`.
+
+- Pre-commit hook: `make check` if local testing is possible, otherwise
+  `make lint && make fmt-check`. The Makefile should provide a `make hooks`
+  target to install the pre-commit hook.
+
+- All repos with software must have tests that run via the platform-standard
+  test framework (`go test`, `pytest`, `jest`/`vitest`, etc.). If no meaningful
+  tests exist yet, add the most minimal test possible — e.g. importing the
+  module under test to verify it compiles/parses. There is no excuse for
+  `make test` to be a no-op.
+
+- `make test` must complete in under 20 seconds. Add a 30-second timeout in the
+  Makefile.
+
+- Docker builds must complete in under 5 minutes.
+
+- `make check` must not modify any files in the repo. Tests may use temporary
+  directories.
+
+- `main` must always pass `make check`, no exceptions.
+
+- Never commit secrets. `.env` files, credentials, API keys, and private keys
+  must be in `.gitignore`. No exceptions.
+
+- `.gitignore` should be comprehensive from the start: OS files (`.DS_Store`),
+  editor files (`.swp`, `*~`), language build artifacts, and `node_modules/`.
+  Fetch the standard `.gitignore` from
+  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitignore` when setting up
+  a new repo.
+
+- Never use `git add -A` or `git add .`. Always stage files explicitly by name.
+
+- Never force-push to `main`.
+
+- Make all changes on a feature branch. You can do whatever you want on a
+  feature branch.
+
+- `.golangci.yml` is standardized and must _NEVER_ be modified by an agent, only
+  manually by the user. Fetch from
+  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`.
+
+- When pinning images or packages by hash, add a comment above the reference
+  with the version and date (YYYY-MM-DD).
+
+- Use `yarn`, not `npm`.
+
+- Write all dates as YYYY-MM-DD (ISO 8601).
+
+- Simple projects should be configured with environment variables.
+
+- Dockerized web services listen on port 8080 by default, overridable with
+  `PORT`.
+
+- `README.md` is the primary documentation. Required sections:
+    - **Description**: First line must include the project name, purpose,
+      category (web server, SPA, CLI tool, etc.), license, and author. Example:
+      "µPaaS is an MIT-licensed Go web application by @sneak that receives
+      git-frontend webhooks and deploys applications via Docker in realtime."
+    - **Getting Started**: Copy-pasteable install/usage code block.
+    - **Rationale**: Why does this exist?
+    - **Design**: How is the program structured?
+    - **TODO**: Update meticulously, even between commits. When planning, put
+      the todo list in the README so a new agent can pick up where the last one
+      left off.
+    - **License**: MIT, GPL, or WTFPL. Ask the user for new projects. Include a
+      `LICENSE` file in the repo root and a License section in the README.
+    - **Author**: [@sneak](https://sneak.berlin).
+
+- First commit of a new repo should contain only `README.md`.
+
+- Go module root: `sneak.berlin/go/<name>`. Always run `go mod tidy` before
+  committing.
+
+- Use SemVer.
+
+- Database migrations live in `internal/db/migrations/` and must be embedded in
+  the binary.
+    - `000_migration.sql` — contains ONLY the creation of the migrations
+      tracking table itself. Nothing else.
+    - `001_schema.sql` — the full application schema.
+    - **Pre-1.0.0:** never add additional migration files (002, 003, etc.).
+      There is no installed base to migrate. Edit `001_schema.sql` directly.
+    - **Post-1.0.0:** add new numbered migration files for each schema change.
+      Never edit existing migrations after release.
+
+- All repos should have an `.editorconfig` enforcing the project's indentation
+  settings.
+
+- Avoid putting files in the repo root unless necessary. Root should contain
+  only project-level config files (`README.md`, `Makefile`, `Dockerfile`,
+  `LICENSE`, `.gitignore`, `.editorconfig`, `REPO_POLICIES.md`, and
+  language-specific config). Everything else goes in a subdirectory. Canonical
+  subdirectory names:
+    - `bin/` — executable scripts and tools
+    - `cmd/` — Go command entrypoints
+    - `configs/` — configuration templates and examples
+    - `deploy/` — deployment manifests (k8s, compose, terraform)
+    - `docs/` — documentation and markdown (README.md stays in root)
+    - `internal/` — Go internal packages
+    - `internal/db/migrations/` — database migrations
+    - `pkg/` — Go library packages
+    - `share/` — systemd units, data files
+    - `static/` — static assets (images, fonts, etc.)
+    - `web/` — web frontend source
+
+- When setting up a new repo, files from the `prompts` repo may be used as
+  templates. Fetch them from
+  `https://git.eeqj.de/sneak/prompts/raw/branch/main/<path>`.
+
+- New repos must contain at minimum:
+    - `README.md`, `.git`, `.gitignore`, `.editorconfig`
+    - `LICENSE`, `REPO_POLICIES.md` (copy from the `prompts` repo)
+    - `Makefile`
+    - `Dockerfile`, `.dockerignore`
+    - `.gitea/workflows/check.yml`
+    - Go: `go.mod`, `go.sum`, `.golangci.yml`
+    - JS: `package.json`, `yarn.lock`, `.prettierrc`, `.prettierignore`
+    - Python: `pyproject.toml`

backend-go/.env.example

@@ -14,3 +14,7 @@ POLL_INTERVAL_MS=60000
 
 # Firebase
 FIREBASE_PROJECT_ID=koin-ping
+
+# Email notifications (Resend — https://resend.com)
+# RESEND_API_KEY=re_xxxxxxxxxxxx
+# EMAIL_FROM=Koin Ping <alerts@yourdomain.com>

backend-go/.golangci.yml

@@ -0,0 +1,32 @@
+version: "2"
+
+run:
+  timeout: 5m
+  modules-download-mode: readonly
+
+linters:
+  default: all
+  disable:
+    # Genuinely incompatible with project patterns
+    - exhaustruct      # Requires all struct fields
+    - depguard         # Dependency allow/block lists
+    - godot            # Requires comments to end with periods
+    - wsl              # Deprecated, replaced by wsl_v5
+    - wrapcheck        # Too verbose for internal packages
+    - varnamelen       # Short names like db, id are idiomatic Go
+
+linters-settings:
+  lll:
+    line-length: 88
+  funlen:
+    lines: 80
+    statements: 50
+  cyclop:
+    max-complexity: 15
+  dupl:
+    threshold: 100
+
+issues:
+  exclude-use-default: false
+  max-issues-per-linter: 0
+  max-same-issues: 0

backend-go/ENV_TEMPLATE.md

@@ -37,16 +37,20 @@ cp ENV_TEMPLATE.md .env
 
 ## Firebase Setup
 
-For Firebase Admin SDK to work, you need to set up Application Default Credentials:
+For Firebase Admin SDK to work, you need to set up Application Default
+Credentials:
 
 **Option 1: Use Firebase Project ID (easiest for development)**
+
 - Just set `FIREBASE_PROJECT_ID` in .env
 - Firebase Admin will use Application Default Credentials
 
 **Option 2: Use Service Account Key (production)**
+
 1. Go to Firebase Console > Project Settings > Service Accounts
 2. Click "Generate new private key"
 3. Download the JSON file
 4. Either:
-   - Set `GOOGLE_APPLICATION_CREDENTIALS=/path/to/serviceAccountKey.json` in .env
-   - Or keep it in backend/ and add to .gitignore
+    - Set `GOOGLE_APPLICATION_CREDENTIALS=/path/to/serviceAccountKey.json` in
+      .env
+    - Or keep it in backend/ and add to .gitignore

backend-go/README.md

@@ -1,4 +1,7 @@
+Start DB:
+
+brew services start postgresql@15
+
 Run Backend:
 
-cd /Users/kjannette/workspace/koin_ping/backend-go
-go run ./cmd/api
+cd /Users/kjannette/workspace/koin_ping/backend-go go run ./cmd/api

backend-go/cmd/api/main.go

@@ -1,10 +1,11 @@
+// Package main is the entry point for the API server.
 package main
 
 import (
 	"fmt"
 	"log"
 	"net/http"
-	"os"
+	"time"
 
 	"github.com/joho/godotenv"
 	"github.com/kjannette/koin-ping/backend-go/internal/config"
@@ -13,8 +14,17 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/handlers"
 	"github.com/kjannette/koin-ping/backend-go/internal/middleware"
 	"github.com/kjannette/koin-ping/backend-go/internal/models"
+	"github.com/kjannette/koin-ping/backend-go/internal/services"
 )
 
+const (
+	// max duration to read a request.
+	serverReadTimeoutSeconds = 5
+	// maxiduration to write a response.
+	serverWriteTimeoutSeconds = 10
+)
+
+//nolint:funlen
 func main() {
 	_ = godotenv.Load() // .env is optional; env vars can also be set externally
 
@@ -27,47 +37,76 @@ func main() {
 	if err != nil {
 		log.Fatalf("Failed to connect to database: %v", err)
 	}
-	defer database.Close()
 
 	if err := firebase.Init(cfg.FirebaseProjectID); err != nil {
 		log.Fatalf("Failed to initialize Firebase: %v", err)
 	}
 
+	defer database.Close()
+
 	addressModel := models.NewAddressModel(pool)
 	alertRuleModel := models.NewAlertRuleModel(pool)
 	alertEventModel := models.NewAlertEventModel(pool)
+	checkpointModel := models.NewCheckpointModel(pool)
 	notifConfigModel := models.NewNotificationConfigModel(pool)
 
+	emailDigestSvc := services.NewEmailDigestService(
+		cfg.ResendAPIKey, cfg.EmailFrom, alertEventModel, notifConfigModel,
+	)
+
 	addressHandler := handlers.NewAddressHandler(addressModel)
 	alertRuleHandler := handlers.NewAlertRuleHandler(alertRuleModel, addressModel)
 	alertEventHandler := handlers.NewAlertEventHandler(alertEventModel)
-	notifConfigHandler := handlers.NewNotificationConfigHandler(notifConfigModel)
+	notifConfigHandler := handlers.NewNotificationConfigHandler(notifConfigModel, cfg)
+	emailDigestHandler := handlers.NewEmailDigestHandler(emailDigestSvc, notifConfigModel)
+	statusHandler := handlers.NewStatusHandler(checkpointModel)
 
 	mux := http.NewServeMux()
 	b := cfg.APIBasePath // e.g. "/v1"
 
 	// Public routes
 	mux.HandleFunc("GET "+b+"/health", handlers.HealthCheck)
-	mux.HandleFunc("GET "+b+"/status", handlers.SystemStatus)
+	mux.HandleFunc("GET "+b+"/status", statusHandler.GetStatus)
 
 	// Authenticated routes — addresses
-	mux.Handle("POST "+b+"/addresses", middleware.Authenticate(http.HandlerFunc(addressHandler.Create)))
-	mux.Handle("GET "+b+"/addresses", middleware.Authenticate(http.HandlerFunc(addressHandler.List)))
-	mux.Handle("DELETE "+b+"/addresses/{addressId}", middleware.Authenticate(http.HandlerFunc(addressHandler.Remove)))
+	mux.Handle("POST "+b+"/addresses",
+		middleware.Authenticate(http.HandlerFunc(addressHandler.Create)))
+	mux.Handle("GET "+b+"/addresses",
+		middleware.Authenticate(http.HandlerFunc(addressHandler.List)))
+	mux.Handle("DELETE "+b+"/addresses/{addressId}",
+		middleware.Authenticate(http.HandlerFunc(addressHandler.Remove)))
+	mux.Handle("PATCH "+b+"/addresses/{addressId}",
+		middleware.Authenticate(http.HandlerFunc(addressHandler.UpdateLabel)))
 
-	// Authenticated routes — alert rules
-	mux.Handle("POST "+b+"/addresses/{addressId}/alerts", middleware.Authenticate(http.HandlerFunc(alertRuleHandler.Create)))
-	mux.Handle("GET "+b+"/addresses/{addressId}/alerts", middleware.Authenticate(http.HandlerFunc(alertRuleHandler.ListByAddress)))
-	mux.Handle("PATCH "+b+"/alerts/{alertId}", middleware.Authenticate(http.HandlerFunc(alertRuleHandler.UpdateStatus)))
-	mux.Handle("DELETE "+b+"/alerts/{alertId}", middleware.Authenticate(http.HandlerFunc(alertRuleHandler.Remove)))
+	// Authenticated routes for alert rules
+	mux.Handle("POST "+b+"/addresses/{addressId}/alerts",
+		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.Create)))
+	mux.Handle("GET "+b+"/addresses/{addressId}/alerts",
+		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.ListByAddress)))
+	mux.Handle("PATCH "+b+"/alerts/{alertId}",
+		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.UpdateStatus)))
+	mux.Handle("DELETE "+b+"/alerts/{alertId}",
+		middleware.Authenticate(http.HandlerFunc(alertRuleHandler.Remove)))
 
 	// Authenticated routes — alert events
-	mux.Handle("GET "+b+"/alert-events", middleware.Authenticate(http.HandlerFunc(alertEventHandler.List)))
+	mux.Handle("GET "+b+"/alert-events",
+		middleware.Authenticate(http.HandlerFunc(alertEventHandler.List)))
 
 	// Authenticated routes — notification config
-	mux.Handle("GET "+b+"/notification-config", middleware.Authenticate(http.HandlerFunc(notifConfigHandler.GetConfig)))
-	mux.Handle("PUT "+b+"/notification-config", middleware.Authenticate(http.HandlerFunc(notifConfigHandler.UpdateConfig)))
-	mux.Handle("DELETE "+b+"/notification-config", middleware.Authenticate(http.HandlerFunc(notifConfigHandler.DeleteConfig)))
+	mux.Handle("GET "+b+"/notification-config",
+		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.GetConfig)))
+	mux.Handle("PUT "+b+"/notification-config",
+		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.UpdateConfig)))
+	mux.Handle("DELETE "+b+"/notification-config",
+		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.DeleteConfig)))
+	mux.Handle("POST "+b+"/notification-config/test",
+		middleware.Authenticate(http.HandlerFunc(notifConfigHandler.TestChannels)))
+
+	// Authenticated routes — email digest
+	mux.Handle("POST "+b+"/email/setup",
+		middleware.Authenticate(http.HandlerFunc(emailDigestHandler.SetupEmail)))
+	mux.Handle("POST "+b+"/email/digest",
+		middleware.Authenticate(http.HandlerFunc(emailDigestHandler.SendDigest)))
 
 	handler := corsMiddleware(mux)
 
@@ -76,9 +115,14 @@ func main() {
 	log.Printf("API base path: %s", cfg.APIBasePath)
 	log.Printf("Environment: %s", cfg.NodeEnv)
 
-	if err := http.ListenAndServe(addr, handler); err != nil {
+	server := &http.Server{
+		Addr:         addr,
+		Handler:      handler,
+		ReadTimeout:  serverReadTimeoutSeconds * time.Second,
+		WriteTimeout: serverWriteTimeoutSeconds * time.Second,
+	}
+	if err := server.ListenAndServe(); err != nil {
 		log.Fatalf("Server failed: %v", err)
-		os.Exit(1)
 	}
 }
 
@@ -90,6 +134,7 @@ func corsMiddleware(next http.Handler) http.Handler {
 
 		if r.Method == http.MethodOptions {
 			w.WriteHeader(http.StatusNoContent)
+
 			return
 		}
 

backend-go/cmd/poller/main.go

@@ -1,3 +1,4 @@
+// Package main is the entry point for the blockchain observer poller.
 package main
 
 import (
@@ -18,6 +19,14 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/services"
 )
 
+const (
+	// separatorWidth is the number of characters in log separator lines.
+	separatorWidth = 60
+	// msPerSecond converts milliseconds to seconds.
+	msPerSecond = 1000
+)
+
+//nolint:funlen
 func main() {
 	_ = godotenv.Load()
 
@@ -34,13 +43,14 @@ func main() {
 	if err != nil {
 		log.Fatalf("Failed to connect to database: %v", err)
 	}
-	defer database.Close()
 
 	eth, err := ethereum.NewJsonRpcEthereum(cfg.EthRPCURL)
 	if err != nil {
 		log.Fatalf("Failed to create Ethereum observer: %v", err)
 	}
 
+	defer database.Close()
+
 	addressModel := models.NewAddressModel(pool)
 	alertRuleModel := models.NewAlertRuleModel(pool)
 	alertEventModel := models.NewAlertEventModel(pool)
@@ -48,7 +58,11 @@ func main() {
 	notifConfigModel := models.NewNotificationConfigModel(pool)
 
 	observer := services.NewObserverService(eth, addressModel, checkpointModel)
-	evaluator := services.NewEvaluatorService(eth, alertRuleModel, alertEventModel, addressModel, notifConfigModel)
+	evaluator := services.NewEvaluatorService(
+		eth, alertRuleModel, alertEventModel, addressModel, notifConfigModel,
+		cfg.ResendAPIKey, cfg.EmailFrom,
+	)
+	digestSvc := services.NewEmailDigestService(cfg.ResendAPIKey, cfg.EmailFrom, alertEventModel, notifConfigModel)
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -58,50 +72,69 @@ func main() {
 	go func() {
 		<-sigCh
 		log.Println()
-		log.Println(strings.Repeat("=", 60))
+		log.Println(strings.Repeat("=", separatorWidth))
 		log.Println("Shutting down poller gracefully...")
-		log.Println(strings.Repeat("=", 60))
+		log.Println(strings.Repeat("=", separatorWidth))
 		cancel()
 	}()
 
 	interval := time.Duration(cfg.PollIntervalMS) * time.Millisecond
+	digestInterval := time.Duration(cfg.DigestIntervalHours) * time.Hour
 
-	log.Println(strings.Repeat("=", 60))
+	log.Println(strings.Repeat("=", separatorWidth))
 	log.Println("Koin Ping Observer Poller Starting")
-	log.Println(strings.Repeat("=", 60))
+	log.Println(strings.Repeat("=", separatorWidth))
 	log.Printf("RPC URL: %s", cfg.EthRPCURL)
-	log.Printf("Poll Interval: %dms (%ds)", cfg.PollIntervalMS, cfg.PollIntervalMS/1000)
-	log.Println(strings.Repeat("=", 60))
+	log.Printf("Poll Interval: %dms (%ds)", cfg.PollIntervalMS, cfg.PollIntervalMS/msPerSecond)
+	log.Printf("Digest Interval: %dh", cfg.DigestIntervalHours)
+	log.Println(strings.Repeat("=", separatorWidth))
 
 	runCycle(ctx, observer, evaluator)
 
 	ticker := time.NewTicker(interval)
 	defer ticker.Stop()
 
+	digestTicker := time.NewTicker(digestInterval)
+	defer digestTicker.Stop()
+
 	for {
 		select {
 		case <-ctx.Done():
 			log.Println("Poller stopped")
+
 			return
 		case <-ticker.C:
 			runCycle(ctx, observer, evaluator)
+		case <-digestTicker.C:
+			sent, digestErr := digestSvc.SendDigestsForAllUsers(ctx)
+			if digestErr != nil {
+				log.Printf("Email digest failed: %v", digestErr)
+			} else {
+				log.Printf("Sent %d email digests", sent)
+			}
 		}
 	}
 }
 
-func runCycle(ctx context.Context, observer *services.ObserverService, evaluator *services.EvaluatorService) {
+func runCycle(
+	ctx context.Context,
+	observer *services.ObserverService,
+	evaluator *services.EvaluatorService,
+) {
 	startTime := time.Now()
 	log.Printf("[%s] Starting observation cycle...", time.Now().UTC().Format(time.RFC3339))
 
 	observations, err := observer.RunOnce(ctx)
 	if err != nil {
 		log.Printf("[%s] Observation cycle failed: %v", time.Now().UTC().Format(time.RFC3339), err)
+
 		return
 	}
 
 	alertsFired, err := evaluator.Evaluate(ctx, observations)
 	if err != nil {
 		log.Printf("[%s] Evaluation failed: %v", time.Now().UTC().Format(time.RFC3339), err)
+
 		return
 	}
 

backend-go/go.mod

@@ -42,6 +42,7 @@ require (
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
 	github.com/joho/godotenv v1.5.1 // indirect
 	github.com/planetscale/vtprotobuf v0.6.1-0.20240319094008-0393e58bdf10 // indirect
+	github.com/resend/resend-go/v3 v3.1.1 // indirect
 	github.com/spiffe/go-spiffe/v2 v2.6.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/detectors/gcp v1.39.0 // indirect

backend-go/go.sum

@@ -92,6 +92,8 @@ github.com/planetscale/vtprotobuf v0.6.1-0.20240319094008-0393e58bdf10/go.mod h1
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/resend/resend-go/v3 v3.1.1 h1:Uwpf/tZU+O/r/3nMWE6zUAMIG9dX/vTBS3wlQzYJKSw=
+github.com/resend/resend-go/v3 v3.1.1/go.mod h1:iI7VA0NoGjWvsNii5iNC5Dy0llsI3HncXPejhniYzwE=
 github.com/spiffe/go-spiffe/v2 v2.6.0 h1:l+DolpxNWYgruGQVV0xsfeya3CsC7m8iBzDnMpsbLuo=
 github.com/spiffe/go-spiffe/v2 v2.6.0/go.mod h1:gm2SeUoMZEtpnzPNs2Csc0D/gX33k1xIx7lEzqblHEs=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

backend-go/infra/migrations/003_add_slack_webhook.sql

@@ -0,0 +1,2 @@
+ALTER TABLE user_notification_configs
+  ADD COLUMN IF NOT EXISTS slack_webhook_url TEXT;

backend-go/infra/migrations/004_alert_event_dedup.sql

@@ -0,0 +1,3 @@
+CREATE UNIQUE INDEX IF NOT EXISTS idx_alert_events_dedup
+    ON alert_events (alert_rule_id, tx_hash)
+    WHERE tx_hash IS NOT NULL;

backend-go/infra/schema.sql

@@ -54,8 +54,9 @@ CREATE TABLE user_notification_configs (
   user_id VARCHAR(128) PRIMARY KEY,
   discord_webhook_url TEXT,            -- Discord webhook URL (nullable)
   telegram_chat_id VARCHAR(128),       -- Telegram chat ID (nullable)
-  telegram_bot_token VARCHAR(255),     -- Telegram bot token (nullable, future use)
+  telegram_bot_token VARCHAR(255),     -- Telegram bot token (nullable)
   email VARCHAR(255),                  -- Email for notifications (nullable)
+  slack_webhook_url TEXT,              -- Slack incoming webhook URL (nullable)
   notification_enabled BOOLEAN DEFAULT TRUE,  -- Master on/off switch
   created_at TIMESTAMP DEFAULT NOW(),
   updated_at TIMESTAMP DEFAULT NOW()

backend-go/internal/config/config.go

@@ -1,3 +1,4 @@
+//loads environment-based configuration.
 package config
 
 import (
@@ -7,6 +8,14 @@ import (
 	"strings"
 )
 
+const (
+	defaultPort = 3001
+	defaultDBPort = 5432
+	defaultPollIntervalMS = 60000
+	minPollIntervalMS = 1000
+	defaultDigestIntervalHours = 24
+)
+
 type Config struct {
 	Port              int
 	APIBasePath       string
@@ -20,26 +29,33 @@ type Config struct {
 	EthRPCURL         string
 	PollIntervalMS    int
 	NodeEnv           string
+	ResendAPIKey         string
+	EmailFrom            string
+	DigestIntervalHours  int
 }
 
+// Load reads configuration from environment variables and returns a Config.
 func Load() (*Config, error) {
 	cfg := &Config{
-		Port:           getEnvInt("PORT", 3001),
-		APIBasePath:    getEnv("API_BASE_PATH", "/v1"),
-		DatabaseURL:    os.Getenv("DATABASE_URL"),
-		DBHost:         getEnv("DB_HOST", "localhost"),
-		DBPort:         getEnvInt("DB_PORT", 5432),
-		DBUser:         os.Getenv("DB_USER"),
-		DBPassword:     os.Getenv("DB_PASSWORD"),
-		DBName:         os.Getenv("DB_NAME"),
+		Port:              getEnvInt("PORT", defaultPort),
+		APIBasePath:       getEnv("API_BASE_PATH", "/v1"),
+		DatabaseURL:       os.Getenv("DATABASE_URL"),
+		DBHost:            getEnv("DB_HOST", "localhost"),
+		DBPort:            getEnvInt("DB_PORT", defaultDBPort),
+		DBUser:            os.Getenv("DB_USER"),
+		DBPassword:        os.Getenv("DB_PASSWORD"),
+		DBName:            os.Getenv("DB_NAME"),
 		FirebaseProjectID: os.Getenv("FIREBASE_PROJECT_ID"),
-		EthRPCURL:      os.Getenv("ETH_RPC_URL"),
-		PollIntervalMS: getEnvInt("POLL_INTERVAL_MS", 60000),
-		NodeEnv:        getEnv("NODE_ENV", "development"),
+		EthRPCURL:         os.Getenv("ETH_RPC_URL"),
+		PollIntervalMS:    getEnvInt("POLL_INTERVAL_MS", defaultPollIntervalMS),
+		NodeEnv:           getEnv("NODE_ENV", "development"),
+		ResendAPIKey:        os.Getenv("RESEND_API_KEY"),
+		EmailFrom:           getEnv("EMAIL_FROM", "Koin Ping <alerts@koinping.com>"),
+		DigestIntervalHours: getEnvInt("DIGEST_INTERVAL_HOURS", defaultDigestIntervalHours),
 	}
 
-	if cfg.PollIntervalMS < 1000 {
-		return nil, fmt.Errorf("POLL_INTERVAL_MS must be >= 1000, got %d", cfg.PollIntervalMS)
+	if cfg.PollIntervalMS < minPollIntervalMS {
+		return nil, fmt.Errorf("POLL_INTERVAL_MS must be >= 1000, got %d", cfg.PollIntervalMS) //nolint:err113
 	}
 
 	return cfg, nil
@@ -47,17 +63,19 @@ func Load() (*Config, error) {
 
 func (c *Config) DSN() string {
 	if c.DatabaseURL != "" {
-		// pgx defaults to sslmode=prefer, which fails against local Postgres.
 		// Append sslmode=disable if not already specified.
 		if !strings.Contains(c.DatabaseURL, "sslmode=") {
 			sep := "?"
 			if strings.Contains(c.DatabaseURL, "?") {
 				sep = "&"
 			}
+
 			return c.DatabaseURL + sep + "sslmode=disable"
 		}
+
 		return c.DatabaseURL
 	}
+
 	return fmt.Sprintf(
 		"host=%s port=%d user=%s password=%s dbname=%s sslmode=disable",
 		c.DBHost, c.DBPort, c.DBUser, c.DBPassword, c.DBName,
@@ -68,6 +86,7 @@ func getEnv(key, fallback string) string {
 	if v := os.Getenv(key); v != "" {
 		return v
 	}
+
 	return fallback
 }
 
@@ -77,5 +96,6 @@ func getEnvInt(key string, fallback int) int {
 			return n
 		}
 	}
+
 	return fallback
 }

backend-go/internal/database/postgres.go

@@ -1,3 +1,4 @@
+// Package database manages PostgreSQL connection pools.
 package database
 
 import (
@@ -9,20 +10,34 @@ import (
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
-var pool *pgxpool.Pool
+const (
+	// maxConnIdleSeconds is the maximum idle time for a connection.
+	maxConnIdleSeconds = 30
+	// maxConnLifetimeMinutes is the maximum lifetime for a connection.
+	maxConnLifetimeMinutes = 5
+	// connectTimeoutSeconds is the timeout for initial connection.
+	connectTimeoutSeconds = 10
+	// maxConns is the maximum number of connections in the pool.
+	maxConns = 20
+	// minConns is the minimum number of connections in the pool.
+	minConns = 2
+)
 
+var pool *pgxpool.Pool //nolint:gochecknoglobals
+
+// Connect establishes a PostgreSQL connection pool using the given DSN.
 func Connect(dsn string) (*pgxpool.Pool, error) {
 	cfg, err := pgxpool.ParseConfig(dsn)
 	if err != nil {
 		return nil, fmt.Errorf("parse database config: %w", err)
 	}
 
-	cfg.MaxConns = 20
-	cfg.MinConns = 2
-	cfg.MaxConnIdleTime = 30 * time.Second
-	cfg.MaxConnLifetime = 5 * time.Minute
+	cfg.MaxConns = maxConns
+	cfg.MinConns = minConns
+	cfg.MaxConnIdleTime = maxConnIdleSeconds * time.Second
+	cfg.MaxConnLifetime = maxConnLifetimeMinutes * time.Minute
 
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	ctx, cancel := context.WithTimeout(context.Background(), connectTimeoutSeconds*time.Second)
 	defer cancel()
 
 	p, err := pgxpool.NewWithConfig(ctx, cfg)
@@ -32,18 +47,22 @@ func Connect(dsn string) (*pgxpool.Pool, error) {
 
 	if err := p.Ping(ctx); err != nil {
 		p.Close()
+
 		return nil, fmt.Errorf("ping database: %w", err)
 	}
 
 	log.Println("Connected to PostgreSQL database")
 	pool = p
+
 	return p, nil
 }
 
+// Pool returns the global connection pool.
 func Pool() *pgxpool.Pool {
 	return pool
 }
 
+// Close closes the global connection pool.
 func Close() {
 	if pool != nil {
 		pool.Close()

backend-go/internal/domain/types.go

@@ -1,17 +1,24 @@
+// Package domain defines core domain types shared across the application.
 package domain
 
 import "time"
 
+// Address represents a tracked Ethereum address.
 type Address struct {
 	ID        int       `json:"id"`
-	UserID    string    `json:"user_id"`
+	UserID    string    `json:"user_id"`    //nolint:tagliatelle
 	Address   string    `json:"address"`
 	Label     *string   `json:"label"`
-	CreatedAt time.Time `json:"created_at"`
+	CreatedAt time.Time `json:"created_at"` //nolint:tagliatelle
 }
 
+// AlertType identifies the kind of alert rule.
 type AlertType string
 
+// String implements fmt.Stringer.
+func (a AlertType) String() string { return string(a) }
+
+// Alert type constants define the supported alert triggers.
 const (
 	AlertIncomingTx    AlertType = "incoming_tx"
 	AlertOutgoingTx    AlertType = "outgoing_tx"
@@ -19,97 +26,116 @@ const (
 	AlertBalanceBelow  AlertType = "balance_below"
 )
 
-var ValidAlertTypes = []AlertType{
+// ValidAlertTypes lists all alert types accepted by the API.
+var ValidAlertTypes = []AlertType{ //nolint:gochecknoglobals
 	AlertIncomingTx,
 	AlertOutgoingTx,
 	AlertLargeTransfer,
 	AlertBalanceBelow,
 }
 
-var ThresholdRequiredTypes = []AlertType{
+// ThresholdRequiredTypes lists alert types that require a threshold value.
+var ThresholdRequiredTypes = []AlertType{ //nolint:gochecknoglobals
 	AlertLargeTransfer,
 	AlertBalanceBelow,
 }
 
+// IsValidAlertType returns true if the given string matches a known AlertType.
 func IsValidAlertType(t string) bool {
 	for _, v := range ValidAlertTypes {
 		if string(v) == t {
 			return true
 		}
 	}
+
 	return false
 }
 
+// IsThresholdRequired returns true if the given AlertType requires a threshold.
 func IsThresholdRequired(t AlertType) bool {
 	for _, v := range ThresholdRequiredTypes {
 		if v == t {
 			return true
 		}
 	}
+
 	return false
 }
 
+// AlertRule represents a user-defined alert rule for an address.
 type AlertRule struct {
 	ID        int       `json:"id"`
-	AddressID int       `json:"address_id"`
+	AddressID int       `json:"address_id"` //nolint:tagliatelle
 	Type      AlertType `json:"type"`
 	Threshold *float64  `json:"threshold"`
 	Enabled   bool      `json:"enabled"`
-	CreatedAt time.Time `json:"created_at"`
+	CreatedAt time.Time `json:"created_at"` //nolint:tagliatelle
 }
 
+// AlertEvent represents a fired alert event stored for history.
 type AlertEvent struct {
-	ID          int       `json:"id"`
-	AlertRuleID int       `json:"alert_rule_id"`
-	Message     string    `json:"message"`
-	AddressLabel *string  `json:"address_label"`
-	TxHash      *string   `json:"tx_hash"`
-	Timestamp   time.Time `json:"timestamp"`
+	ID           int       `json:"id"`
+	AlertRuleID  int       `json:"alert_rule_id"`   //nolint:tagliatelle
+	Message      string    `json:"message"`
+	AddressLabel *string   `json:"address_label"`   //nolint:tagliatelle
+	TxHash       *string   `json:"tx_hash"`         //nolint:tagliatelle
+	Timestamp    time.Time `json:"timestamp"`
 }
 
+// AddressCheckpoint tracks the last block checked for an address.
 type AddressCheckpoint struct {
-	AddressID        int       `json:"address_id"`
-	LastCheckedBlock int       `json:"last_checked_block"`
-	LastCheckedAt    time.Time `json:"last_checked_at"`
+	AddressID        int       `json:"address_id"`         //nolint:tagliatelle
+	LastCheckedBlock int       `json:"last_checked_block"` //nolint:tagliatelle
+	LastCheckedAt    time.Time `json:"last_checked_at"`    //nolint:tagliatelle
 }
 
+// CheckpointDetail combines checkpoint and address info for reporting.
 type CheckpointDetail struct {
-	AddressID        int       `json:"address_id"`
+	AddressID        int       `json:"address_id"`         //nolint:tagliatelle
 	Address          string    `json:"address"`
 	Label            *string   `json:"label"`
-	LastCheckedBlock int       `json:"last_checked_block"`
-	LastCheckedAt    time.Time `json:"last_checked_at"`
+	LastCheckedBlock int       `json:"last_checked_block"` //nolint:tagliatelle
+	LastCheckedAt    time.Time `json:"last_checked_at"`    //nolint:tagliatelle
 }
 
+// NotificationConfig holds a user's notification preferences.
 type NotificationConfig struct {
-	UserID              string  `json:"user_id"`
-	DiscordWebhookURL   *string `json:"discord_webhook_url"`
-	TelegramChatID      *string `json:"telegram_chat_id"`
-	TelegramBotToken    *string `json:"telegram_bot_token,omitempty"`
-	Email               *string `json:"email"`
-	NotificationEnabled bool    `json:"notification_enabled"`
-	CreatedAt           *time.Time `json:"created_at,omitempty"`
-	UpdatedAt           *time.Time `json:"updated_at,omitempty"`
+	UserID              string     `json:"user_id"`              //nolint:tagliatelle
+	DiscordWebhookURL   *string    `json:"discord_webhook_url"`  //nolint:tagliatelle
+	TelegramChatID      *string    `json:"telegram_chat_id"`     //nolint:tagliatelle
+	TelegramBotToken    *string    `json:"telegram_bot_token"`   //nolint:tagliatelle
+	Email               *string    `json:"email"`
+	SlackWebhookURL     *string    `json:"slack_webhook_url"`    //nolint:tagliatelle
+	NotificationEnabled bool       `json:"notification_enabled"` //nolint:tagliatelle
+	CreatedAt           *time.Time `json:"created_at,omitempty"` //nolint:tagliatelle
+	UpdatedAt           *time.Time `json:"updated_at,omitempty"` //nolint:tagliatelle
 }
 
+// NormalizedTx is a blockchain transaction normalized for internal use.
 type NormalizedTx struct {
-	Hash           string `json:"hash"`
-	From           string `json:"from"`
+	Hash           string  `json:"hash"`
+	From           string  `json:"from"`
 	To             *string `json:"to"`
-	Value          string `json:"value"` // Wei as string for precision
-	BlockNumber    int    `json:"block_number"`
-	BlockTimestamp int64  `json:"block_timestamp"`
+	Value          string  `json:"value"` // Wei as string for precision
+	BlockNumber    int     `json:"block_number"`    //nolint:tagliatelle
+	BlockTimestamp int64   `json:"block_timestamp"` //nolint:tagliatelle
 }
 
+// Direction indicates whether a transaction is incoming or outgoing.
 type Direction string
 
+// String implements fmt.Stringer.
+func (d Direction) String() string { return string(d) }
+
+// Direction constants indicate the flow of a transaction relative to a watched address.
 const (
 	DirectionIncoming Direction = "incoming"
 	DirectionOutgoing Direction = "outgoing"
 )
 
+// ObservedTx is a NormalizedTx enriched with address and direction context.
 type ObservedTx struct {
 	NormalizedTx
-	AddressID int       `json:"address_id"`
+	AddressID int       `json:"address_id"` //nolint:tagliatelle
 	Direction Direction `json:"direction"`
 }

backend-go/internal/firebase/admin.go

@@ -1,3 +1,4 @@
+// Package firebase provides Firebase authentication integration.
 package firebase
 
 import (
@@ -10,12 +11,13 @@ import (
 	"google.golang.org/api/option"
 )
 
-var (
-	authClient *auth.Client
-	once       sync.Once
-	initErr    error
+var ( //nolint:gochecknoglobals
+	authClient *auth.Client //nolint:gochecknoglobals
+	once       sync.Once    //nolint:gochecknoglobals
+	errInit    error        //nolint:gochecknoglobals
 )
 
+// Init initializes the Firebase app and auth client using the given project ID.
 func Init(projectID string) error {
 	once.Do(func() {
 		ctx := context.Background()
@@ -30,20 +32,23 @@ func Init(projectID string) error {
 			app, err = fb.NewApp(ctx, nil)
 		}
 		if err != nil {
-			initErr = fmt.Errorf("initialize firebase app: %w", err)
+			errInit = fmt.Errorf("initialize firebase app: %w", err)
+
 			return
 		}
 
 		authClient, err = app.Auth(ctx)
 		if err != nil {
-			initErr = fmt.Errorf("initialize firebase auth: %w", err)
+			errInit = fmt.Errorf("initialize firebase auth: %w", err)
+
 			return
 		}
 	})
 
-	return initErr
+	return errInit
 }
 
+// Auth returns the initialized Firebase auth client.
 func Auth() *auth.Client {
 	return authClient
 }

backend-go/internal/handlers/address.go

@@ -1,3 +1,4 @@
+// Package handlers implements HTTP request handlers for the API.
 package handlers
 
 import (
@@ -14,14 +15,17 @@ import (
 
 var ethAddressRe = regexp.MustCompile(`^0x[a-fA-F0-9]{40}$`)
 
+// AddressHandler handles HTTP requests for address management.
 type AddressHandler struct {
 	addresses *models.AddressModel
 }
 
+// NewAddressHandler creates a new AddressHandler.
 func NewAddressHandler(addresses *models.AddressModel) *AddressHandler {
 	return &AddressHandler{addresses: addresses}
 }
 
+// Create handles POST requests to add a new tracked address.
 func (h *AddressHandler) Create(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 
@@ -32,16 +36,19 @@ func (h *AddressHandler) Create(w http.ResponseWriter, r *http.Request) {
 	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
 		log.Printf("Failed to decode address request body: %v", err)
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid request body")
+
 		return
 	}
 
 	if body.Address == "" {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Address is required")
+
 		return
 	}
 
 	if !ethAddressRe.MatchString(body.Address) {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid Ethereum address format")
+
 		return
 	}
 
@@ -51,10 +58,12 @@ func (h *AddressHandler) Create(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		if strings.Contains(err.Error(), "23505") || strings.Contains(err.Error(), "unique") {
 			writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "You are already tracking this address")
+
 			return
 		}
 		log.Printf("Error creating address: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to create address")
+
 		return
 	}
 
@@ -62,6 +71,7 @@ func (h *AddressHandler) Create(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusCreated, addr)
 }
 
+// List handles GET requests to list all tracked addresses for the current user.
 func (h *AddressHandler) List(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 	log.Printf("User %s listing addresses", userID)
@@ -70,6 +80,7 @@ func (h *AddressHandler) List(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Printf("Error listing addresses: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to list addresses")
+
 		return
 	}
 
@@ -81,11 +92,51 @@ func (h *AddressHandler) List(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, addresses)
 }
 
+// UpdateLabel handles PATCH requests to update an address label.
+func (h *AddressHandler) UpdateLabel(w http.ResponseWriter, r *http.Request) {
+	userID := middleware.GetUserID(r.Context())
+	addressID, ok := parseIntParam(r.PathValue("addressId"))
+	if !ok {
+		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid address ID")
+
+		return
+	}
+
+	var body struct {
+		Label *string `json:"label"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid request body")
+
+		return
+	}
+
+	log.Printf("User %s updating label for address ID: %d", userID, addressID)
+
+	addr, err := h.addresses.UpdateLabel(r.Context(), addressID, userID, body.Label)
+	if err != nil {
+		log.Printf("Error updating address label: %v", err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to update address")
+
+		return
+	}
+
+	if addr == nil {
+		writeError(w, http.StatusNotFound, "NOT_FOUND", "Address not found")
+
+		return
+	}
+
+	writeJSON(w, http.StatusOK, addr)
+}
+
+// Remove handles DELETE requests to remove a tracked address.
 func (h *AddressHandler) Remove(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 	addressID, ok := parseIntParam(r.PathValue("addressId"))
 	if !ok {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid address ID")
+
 		return
 	}
 
@@ -95,12 +146,14 @@ func (h *AddressHandler) Remove(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Printf("Error deleting address: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to delete address")
+
 		return
 	}
 
 	if !deleted {
 		log.Printf("Address %d not found or not owned by user", addressID)
 		writeError(w, http.StatusNotFound, "NOT_FOUND", "Address not found")
+
 		return
 	}
 

backend-go/internal/handlers/alert_event.go

@@ -4,21 +4,23 @@ import (
 	"log"
 	"net/http"
 	"strconv"
-	"time"
 
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 	"github.com/kjannette/koin-ping/backend-go/internal/middleware"
 	"github.com/kjannette/koin-ping/backend-go/internal/models"
 )
 
+// AlertEventHandler handles HTTP requests for alert event history.
 type AlertEventHandler struct {
 	alertEvents *models.AlertEventModel
 }
 
+// NewAlertEventHandler creates a new AlertEventHandler.
 func NewAlertEventHandler(alertEvents *models.AlertEventModel) *AlertEventHandler {
 	return &AlertEventHandler{alertEvents: alertEvents}
 }
 
+// List handles GET requests to list recent alert events for the current user.
 func (h *AlertEventHandler) List(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 
@@ -34,6 +36,7 @@ func (h *AlertEventHandler) List(w http.ResponseWriter, r *http.Request) {
 
 	if limit < 1 || limit > 100 {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Limit must be between 1 and 100")
+
 		return
 	}
 
@@ -41,49 +44,15 @@ func (h *AlertEventHandler) List(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Printf("Error listing alert events: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to list alert events")
+
 		return
 	}
 
 	log.Printf("Found %d alert events for user", len(events))
 
-	// MVP scaffolding: return mock data if DB is empty
-	if len(events) == 0 {
-		events = mockEvents(limit)
+	if events == nil {
+		events = []domain.AlertEvent{}
 	}
 
 	writeJSON(w, http.StatusOK, events)
 }
-
-func mockEvents(limit int) []domain.AlertEvent {
-	label1 := "Treasury Wallet"
-	label2 := "Cold Storage"
-
-	mocks := []domain.AlertEvent{
-		{
-			ID:           1,
-			AlertRuleID:  1,
-			Message:      "Incoming transaction detected: 5.5 ETH received",
-			AddressLabel: &label1,
-			Timestamp:    time.Now().Add(-2 * time.Hour),
-		},
-		{
-			ID:           2,
-			AlertRuleID:  2,
-			Message:      "Balance dropped below threshold: Current balance 8.2 ETH",
-			AddressLabel: &label1,
-			Timestamp:    time.Now().Add(-5 * time.Hour),
-		},
-		{
-			ID:           3,
-			AlertRuleID:  3,
-			Message:      "Outgoing transaction detected: 2.0 ETH sent",
-			AddressLabel: &label2,
-			Timestamp:    time.Now().Add(-24 * time.Hour),
-		},
-	}
-
-	if limit < len(mocks) {
-		return mocks[:limit]
-	}
-	return mocks
-}

backend-go/internal/handlers/alert_rule.go

@@ -2,6 +2,7 @@ package handlers
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"net/http"
@@ -13,20 +14,27 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/models"
 )
 
+// errThresholdFormat is returned when the threshold JSON cannot be decoded.
+var errThresholdFormat = errors.New("unsupported threshold format")
+
+// AlertRuleHandler handles HTTP requests for alert rule management.
 type AlertRuleHandler struct {
 	alertRules *models.AlertRuleModel
 	addresses  *models.AddressModel
 }
 
+// NewAlertRuleHandler creates a new AlertRuleHandler.
 func NewAlertRuleHandler(alertRules *models.AlertRuleModel, addresses *models.AddressModel) *AlertRuleHandler {
 	return &AlertRuleHandler{alertRules: alertRules, addresses: addresses}
 }
 
+// Create handles POST requests to create a new alert rule for an address.
 func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 	addressID, ok := parseIntParam(r.PathValue("addressId"))
 	if !ok {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid address ID")
+
 		return
 	}
 
@@ -37,6 +45,7 @@ func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
 		log.Printf("Failed to decode alert request body: %v", err)
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid request body")
+
 		return
 	}
 
@@ -44,6 +53,7 @@ func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Printf("Failed to parse threshold: %v", err)
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "threshold must be a valid number")
+
 		return
 	}
 
@@ -51,16 +61,18 @@ func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 
 	if body.Type == "" {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Alert type is required")
+
 		return
 	}
 
 	if !domain.IsValidAlertType(body.Type) {
 		types := make([]string, len(domain.ValidAlertTypes))
 		for i, t := range domain.ValidAlertTypes {
-			types[i] = string(t)
+			types[i] = t.String()
 		}
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR",
-			fmt.Sprintf("Invalid alert type. Must be one of: %s", strings.Join(types, ", ")))
+			"Invalid alert type. Must be one of: "+strings.Join(types, ", "))
+
 		return
 	}
 
@@ -69,6 +81,7 @@ func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 		if threshold == nil || *threshold <= 0 {
 			writeError(w, http.StatusBadRequest, "VALIDATION_ERROR",
 				fmt.Sprintf("Alert type '%s' requires a positive threshold value", body.Type))
+
 			return
 		}
 	}
@@ -77,11 +90,13 @@ func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Printf("Error finding address: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to create alert rule")
+
 		return
 	}
 	if addr == nil {
 		log.Printf("Address %d not found or not owned by user", addressID)
 		writeError(w, http.StatusNotFound, "NOT_FOUND", "Address not found")
+
 		return
 	}
 
@@ -89,6 +104,7 @@ func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Printf("Error creating alert rule: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to create alert rule")
+
 		return
 	}
 
@@ -98,12 +114,12 @@ func (h *AlertRuleHandler) Create(w http.ResponseWriter, r *http.Request) {
 
 func parseThreshold(raw json.RawMessage) (*float64, error) {
 	if len(raw) == 0 {
-		return nil, nil
+		return nil, nil //nolint:nilnil
 	}
 
 	// Check null before number -- json.Unmarshal treats null as valid for float64 (sets to 0).
 	if string(raw) == "null" {
-		return nil, nil
+		return nil, nil //nolint:nilnil
 	}
 
 	var asNumber float64
@@ -115,23 +131,26 @@ func parseThreshold(raw json.RawMessage) (*float64, error) {
 	if err := json.Unmarshal(raw, &asString); err == nil {
 		asString = strings.TrimSpace(asString)
 		if asString == "" {
-			return nil, nil
+			return nil, nil //nolint:nilnil
 		}
 		parsed, parseErr := strconv.ParseFloat(asString, 64)
 		if parseErr != nil {
 			return nil, parseErr
 		}
+
 		return &parsed, nil
 	}
 
-	return nil, fmt.Errorf("unsupported threshold format")
+	return nil, errThresholdFormat
 }
 
+// ListByAddress handles GET requests to list alert rules for an address.
 func (h *AlertRuleHandler) ListByAddress(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 	addressID, ok := parseIntParam(r.PathValue("addressId"))
 	if !ok {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid address ID")
+
 		return
 	}
 
@@ -141,11 +160,13 @@ func (h *AlertRuleHandler) ListByAddress(w http.ResponseWriter, r *http.Request)
 	if err != nil {
 		log.Printf("Error finding address: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to list alerts")
+
 		return
 	}
 	if addr == nil {
 		log.Printf("Address %d not found or not owned by user", addressID)
 		writeError(w, http.StatusNotFound, "NOT_FOUND", "Address not found")
+
 		return
 	}
 
@@ -153,6 +174,7 @@ func (h *AlertRuleHandler) ListByAddress(w http.ResponseWriter, r *http.Request)
 	if err != nil {
 		log.Printf("Error listing alerts: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to list alerts")
+
 		return
 	}
 
@@ -164,11 +186,13 @@ func (h *AlertRuleHandler) ListByAddress(w http.ResponseWriter, r *http.Request)
 	writeJSON(w, http.StatusOK, alerts)
 }
 
+// UpdateStatus handles PATCH requests to enable or disable an alert rule.
 func (h *AlertRuleHandler) UpdateStatus(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 	alertID, ok := parseIntParam(r.PathValue("alertId"))
 	if !ok {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid alert ID")
+
 		return
 	}
 
@@ -178,6 +202,7 @@ func (h *AlertRuleHandler) UpdateStatus(w http.ResponseWriter, r *http.Request)
 	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
 		log.Printf("Failed to decode update request body: %v", err)
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid request body")
+
 		return
 	}
 
@@ -185,6 +210,7 @@ func (h *AlertRuleHandler) UpdateStatus(w http.ResponseWriter, r *http.Request)
 
 	if body.Enabled == nil {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "enabled must be a boolean value")
+
 		return
 	}
 
@@ -192,11 +218,13 @@ func (h *AlertRuleHandler) UpdateStatus(w http.ResponseWriter, r *http.Request)
 	if err != nil {
 		log.Printf("Error finding alert: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to update alert")
+
 		return
 	}
 	if alert == nil {
 		log.Printf("Alert %d not found or not owned by user", alertID)
 		writeError(w, http.StatusNotFound, "NOT_FOUND", "Alert rule not found")
+
 		return
 	}
 
@@ -204,6 +232,7 @@ func (h *AlertRuleHandler) UpdateStatus(w http.ResponseWriter, r *http.Request)
 	if err != nil {
 		log.Printf("Error updating alert: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to update alert")
+
 		return
 	}
 
@@ -211,11 +240,13 @@ func (h *AlertRuleHandler) UpdateStatus(w http.ResponseWriter, r *http.Request)
 	writeJSON(w, http.StatusOK, updated)
 }
 
+// Remove handles DELETE requests to remove an alert rule.
 func (h *AlertRuleHandler) Remove(w http.ResponseWriter, r *http.Request) {
 	userID := middleware.GetUserID(r.Context())
 	alertID, ok := parseIntParam(r.PathValue("alertId"))
 	if !ok {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR", "Invalid alert ID")
+
 		return
 	}
 
@@ -225,17 +256,20 @@ func (h *AlertRuleHandler) Remove(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Printf("Error finding alert: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to delete alert")
+
 		return
 	}
 	if alert == nil {
 		log.Printf("Alert %d not found or not owned by user", alertID)
 		writeError(w, http.StatusNotFound, "NOT_FOUND", "Alert rule not found")
+
 		return
 	}
 
 	if _, err := h.alertRules.Remove(r.Context(), alertID); err != nil {
 		log.Printf("Error deleting alert: %v", err)
 		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to delete alert")
+
 		return
 	}
 

backend-go/internal/handlers/alert_rule_test.go

@@ -1,3 +1,4 @@
+//nolint:testpackage // parseThreshold is unexported; internal test package required
 package handlers
 
 import (
@@ -6,8 +7,13 @@ import (
 	"testing"
 )
 
+//nolint:gocognit
 func TestParseThreshold(t *testing.T) {
+	t.Parallel()
+
 	t.Run("nil/empty raw message returns nil", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(nil)
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -18,6 +24,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("empty slice returns nil", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage{})
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -28,6 +36,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("JSON null returns nil", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage("null"))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -38,6 +48,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("number 10 returns 10.0", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage("10"))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -51,6 +63,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("number 0.5 returns 0.5", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage("0.5"))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -61,6 +75,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("string '10' returns 10.0", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage(`"10"`))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -71,6 +87,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("string '0.001' returns 0.001", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage(`"0.001"`))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -81,6 +99,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("string with spaces '  10  ' returns 10.0", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage(`"  10  "`))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -91,6 +111,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("empty string returns nil", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage(`""`))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -101,6 +123,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("whitespace-only string returns nil", func(t *testing.T) {
+		t.Parallel()
+
 		val, err := parseThreshold(json.RawMessage(`"   "`))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
@@ -111,6 +135,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("invalid string returns error", func(t *testing.T) {
+		t.Parallel()
+
 		_, err := parseThreshold(json.RawMessage(`"abc"`))
 		if err == nil {
 			t.Fatal("expected error for non-numeric string")
@@ -118,6 +144,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("boolean returns error", func(t *testing.T) {
+		t.Parallel()
+
 		_, err := parseThreshold(json.RawMessage("true"))
 		if err == nil {
 			t.Fatal("expected error for boolean")
@@ -125,6 +153,8 @@ func TestParseThreshold(t *testing.T) {
 	})
 
 	t.Run("array returns error", func(t *testing.T) {
+		t.Parallel()
+
 		_, err := parseThreshold(json.RawMessage("[1,2]"))
 		if err == nil {
 			t.Fatal("expected error for array")
@@ -132,7 +162,10 @@ func TestParseThreshold(t *testing.T) {
 	})
 }
 
+//nolint:funlen
 func TestDecodeAlertBody(t *testing.T) {
+	t.Parallel()
+
 	// Verifies that the struct used in Create handler can decode all
 	// payload shapes the frontend might send.
 
@@ -183,12 +216,15 @@ func TestDecodeAlertBody(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			var body alertBody
 			err := json.Unmarshal([]byte(tt.payload), &body)
 			if tt.wantErr {
 				if err == nil {
 					t.Fatal("expected decode error")
 				}
+
 				return
 			}
 			if err != nil {
@@ -199,6 +235,8 @@ func TestDecodeAlertBody(t *testing.T) {
 }
 
 func TestOldStructFailsWithStringThreshold(t *testing.T) {
+	t.Parallel()
+
 	// Documents the original bug: *float64 cannot decode a string threshold.
 	type oldAlertBody struct {
 		Type      string   `json:"type"`

backend-go/internal/handlers/email_digest.go

@@ -0,0 +1,101 @@
+package handlers
+
+import (
+	"log"
+	"net/http"
+
+	"github.com/kjannette/koin-ping/backend-go/internal/middleware"
+	"github.com/kjannette/koin-ping/backend-go/internal/models"
+	"github.com/kjannette/koin-ping/backend-go/internal/services"
+)
+
+type EmailDigestHandler struct {
+	digestSvc *services.EmailDigestService
+	configs   *models.NotificationConfigModel
+}
+
+func NewEmailDigestHandler(
+	digestSvc *services.EmailDigestService,
+	configs *models.NotificationConfigModel,
+) *EmailDigestHandler {
+	return &EmailDigestHandler{digestSvc: digestSvc, configs: configs}
+}
+
+// SetupEmail reads the user's email from their notification config and sends
+// a confirmation message via Resend to verify the integration works.
+func (h *EmailDigestHandler) SetupEmail(w http.ResponseWriter, r *http.Request) {
+	userID := middleware.GetUserID(r.Context())
+
+	if !h.digestSvc.Configured() {
+		writeError(w, http.StatusServiceUnavailable, "EMAIL_NOT_CONFIGURED",
+			"Email service is not configured on the server")
+		return
+	}
+
+	cfg, err := h.configs.GetConfig(r.Context(), userID)
+	if err != nil {
+		log.Printf("Error getting notification config for email setup: %v", err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR",
+			"Failed to load notification config")
+		return
+	}
+
+	if cfg == nil || cfg.Email == nil || *cfg.Email == "" {
+		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR",
+			"Save an email address in notification settings first")
+		return
+	}
+
+	if err := h.digestSvc.SetupEmail(*cfg.Email); err != nil {
+		log.Printf("Email setup failed for user %s: %v", userID, err)
+		writeError(w, http.StatusBadGateway, "EMAIL_SEND_FAILED",
+			"Failed to send confirmation email — check server email config")
+		return
+	}
+
+	log.Printf("Email setup confirmation sent to user %s (%s)", userID, *cfg.Email)
+	writeJSON(w, http.StatusOK, map[string]any{
+		"success": true,
+		"email":   *cfg.Email,
+		"message": "Confirmation email sent",
+	})
+}
+
+// SendDigest compiles and sends a digest of recent alerts to the user's email.
+func (h *EmailDigestHandler) SendDigest(w http.ResponseWriter, r *http.Request) {
+	userID := middleware.GetUserID(r.Context())
+
+	if !h.digestSvc.Configured() {
+		writeError(w, http.StatusServiceUnavailable, "EMAIL_NOT_CONFIGURED",
+			"Email service is not configured on the server")
+		return
+	}
+
+	cfg, err := h.configs.GetConfig(r.Context(), userID)
+	if err != nil {
+		log.Printf("Error getting notification config for digest: %v", err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR",
+			"Failed to load notification config")
+		return
+	}
+
+	if cfg == nil || cfg.Email == nil || *cfg.Email == "" {
+		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR",
+			"No email address configured")
+		return
+	}
+
+	if err := h.digestSvc.SendDigest(r.Context(), userID, *cfg.Email); err != nil {
+		log.Printf("Digest send failed for user %s: %v", userID, err)
+		writeError(w, http.StatusBadGateway, "DIGEST_SEND_FAILED",
+			"Failed to send digest email")
+		return
+	}
+
+	log.Printf("Digest sent to user %s (%s)", userID, *cfg.Email)
+	writeJSON(w, http.StatusOK, map[string]any{
+		"success": true,
+		"email":   *cfg.Email,
+		"message": "Digest email sent",
+	})
+}

backend-go/internal/handlers/notification_config.go

@@ -7,19 +7,22 @@ import (
 	"regexp"
 	"strings"
 
+	"github.com/kjannette/koin-ping/backend-go/internal/config"
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 	"github.com/kjannette/koin-ping/backend-go/internal/middleware"
 	"github.com/kjannette/koin-ping/backend-go/internal/models"
+	"github.com/kjannette/koin-ping/backend-go/internal/notifications"
 )
 
 var emailRe = regexp.MustCompile(`^[^\s@]+@[^\s@]+\.[^\s@]+$`)
 
 type NotificationConfigHandler struct {
 	configs *models.NotificationConfigModel
+	cfg     *config.Config
 }
 
-func NewNotificationConfigHandler(configs *models.NotificationConfigModel) *NotificationConfigHandler {
-	return &NotificationConfigHandler{configs: configs}
+func NewNotificationConfigHandler(configs *models.NotificationConfigModel, cfg *config.Config) *NotificationConfigHandler {
+	return &NotificationConfigHandler{configs: configs, cfg: cfg}
 }
 
 func (h *NotificationConfigHandler) GetConfig(w http.ResponseWriter, r *http.Request) {
@@ -51,7 +54,9 @@ func (h *NotificationConfigHandler) UpdateConfig(w http.ResponseWriter, r *http.
 	var body struct {
 		DiscordWebhookURL   *string `json:"discord_webhook_url"`
 		TelegramChatID      *string `json:"telegram_chat_id"`
+		TelegramBotToken    *string `json:"telegram_bot_token"`
 		Email               *string `json:"email"`
+		SlackWebhookURL     *string `json:"slack_webhook_url"`
 		NotificationEnabled *bool   `json:"notification_enabled"`
 	}
 	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
@@ -63,7 +68,8 @@ func (h *NotificationConfigHandler) UpdateConfig(w http.ResponseWriter, r *http.
 	log.Printf("User %s updating notification config", userID)
 
 	if body.DiscordWebhookURL == nil && body.TelegramChatID == nil &&
-		body.Email == nil && body.NotificationEnabled == nil {
+		body.TelegramBotToken == nil && body.Email == nil &&
+		body.SlackWebhookURL == nil && body.NotificationEnabled == nil {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR",
 			"At least one configuration field must be provided")
 		return
@@ -76,6 +82,13 @@ func (h *NotificationConfigHandler) UpdateConfig(w http.ResponseWriter, r *http.
 		return
 	}
 
+	if body.SlackWebhookURL != nil && *body.SlackWebhookURL != "" &&
+		!strings.HasPrefix(*body.SlackWebhookURL, "https://hooks.slack.com/") {
+		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR",
+			"Invalid Slack webhook URL format")
+		return
+	}
+
 	if body.Email != nil && *body.Email != "" && !emailRe.MatchString(*body.Email) {
 		writeError(w, http.StatusBadRequest, "VALIDATION_ERROR",
 			"Invalid email address format")
@@ -90,7 +103,9 @@ func (h *NotificationConfigHandler) UpdateConfig(w http.ResponseWriter, r *http.
 	cfg := domain.NotificationConfig{
 		DiscordWebhookURL:   body.DiscordWebhookURL,
 		TelegramChatID:      body.TelegramChatID,
+		TelegramBotToken:    body.TelegramBotToken,
 		Email:               body.Email,
+		SlackWebhookURL:     body.SlackWebhookURL,
 		NotificationEnabled: enabled,
 	}
 
@@ -126,3 +141,76 @@ func (h *NotificationConfigHandler) DeleteConfig(w http.ResponseWriter, r *http.
 	log.Println("Notification config deleted")
 	w.WriteHeader(http.StatusNoContent)
 }
+
+// TestChannels sends a test message to all configured notification channels.
+func (h *NotificationConfigHandler) TestChannels(w http.ResponseWriter, r *http.Request) {
+	userID := middleware.GetUserID(r.Context())
+	log.Printf("User %s testing notification channels", userID)
+
+	cfg, err := h.configs.GetConfig(r.Context(), userID)
+	if err != nil {
+		log.Printf("Error getting notification config for test: %v", err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to get notification config")
+		return
+	}
+
+	if cfg == nil {
+		writeError(w, http.StatusNotFound, "NOT_FOUND", "No notification configuration found")
+		return
+	}
+
+	type channelResult struct {
+		Channel string `json:"channel"`
+		Success bool   `json:"success"`
+		Error   string `json:"error,omitempty"`
+	}
+
+	var results []channelResult
+
+	if cfg.DiscordWebhookURL != nil && *cfg.DiscordWebhookURL != "" {
+		ok, testErr := notifications.TestDiscordWebhook(*cfg.DiscordWebhookURL)
+		res := channelResult{Channel: "discord", Success: ok}
+		if testErr != nil {
+			res.Error = testErr.Error()
+		}
+		results = append(results, res)
+	}
+
+	if cfg.TelegramBotToken != nil && *cfg.TelegramBotToken != "" &&
+		cfg.TelegramChatID != nil && *cfg.TelegramChatID != "" {
+		ok, testErr := notifications.TestTelegramWebhook(*cfg.TelegramBotToken, *cfg.TelegramChatID)
+		res := channelResult{Channel: "telegram", Success: ok}
+		if testErr != nil {
+			res.Error = testErr.Error()
+		}
+		results = append(results, res)
+	}
+
+	if cfg.SlackWebhookURL != nil && *cfg.SlackWebhookURL != "" {
+		ok, testErr := notifications.TestSlackWebhook(*cfg.SlackWebhookURL)
+		res := channelResult{Channel: "slack", Success: ok}
+		if testErr != nil {
+			res.Error = testErr.Error()
+		}
+		results = append(results, res)
+	}
+
+	if cfg.Email != nil && *cfg.Email != "" {
+		ok, testErr := notifications.TestEmailNotification(
+			h.cfg.ResendAPIKey, h.cfg.EmailFrom, *cfg.Email,
+		)
+		res := channelResult{Channel: "email", Success: ok}
+		if testErr != nil {
+			res.Error = testErr.Error()
+		}
+		results = append(results, res)
+	}
+
+	if len(results) == 0 {
+		writeError(w, http.StatusBadRequest, "NO_CHANNELS",
+			"No notification channels are configured")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{"results": results})
+}

backend-go/internal/handlers/status.go

@@ -1,10 +1,67 @@
 package handlers
 
 import (
+	"log"
 	"net/http"
 	"time"
+
+	"github.com/kjannette/koin-ping/backend-go/internal/models"
 )
 
+// StatusHandler handles the system status endpoint.
+type StatusHandler struct {
+	checkpoints *models.CheckpointModel
+}
+
+// NewStatusHandler creates a new StatusHandler.
+func NewStatusHandler(checkpoints *models.CheckpointModel) *StatusHandler {
+	return &StatusHandler{checkpoints: checkpoints}
+}
+
+// GetStatus returns real-time system status derived from checkpoint data.
+func (h *StatusHandler) GetStatus(w http.ResponseWriter, r *http.Request) {
+	block, checkedAt, err := h.checkpoints.GetLatestBlock(r.Context())
+	if err != nil {
+		log.Printf("Error querying latest block: %v", err)
+		writeError(w, http.StatusInternalServerError, "INTERNAL_ERROR", "Failed to get system status")
+
+		return
+	}
+
+	latestBlock := 0
+	lag := 0
+	status := "starting"
+
+	if checkedAt != nil {
+		lag = int(time.Since(*checkedAt).Seconds())
+		if lag > 600 { //nolint:mnd
+			status = "idle"
+		} else {
+			status = "active"
+		}
+	}
+
+	if block != nil {
+		latestBlock = *block
+	}
+
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"status":        status,
+		"latestBlock":   latestBlock,
+		"lag":           lag,
+		"lastCheckedAt": checkedAtStr(checkedAt),
+		"timestamp":     time.Now().UTC().Format(time.RFC3339),
+	})
+}
+
+func checkedAtStr(t *time.Time) string {
+	if t == nil {
+		return ""
+	}
+
+	return t.UTC().Format(time.RFC3339)
+}
+
 func HealthCheck(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]interface{}{
 		"status":    "ok",
@@ -12,12 +69,3 @@ func HealthCheck(w http.ResponseWriter, r *http.Request) {
 		"service":   "koin-ping-backend",
 	})
 }
-
-func SystemStatus(w http.ResponseWriter, r *http.Request) {
-	writeJSON(w, http.StatusOK, map[string]interface{}{
-		"latestBlock": 0,
-		"lag":         0,
-		"status":      "healthy",
-		"timestamp":   time.Now().UTC().Format(time.RFC3339),
-	})
-}

backend-go/internal/middleware/auth.go

@@ -1,3 +1,4 @@
+// Package middleware provides HTTP middleware for authentication and context injection.
 package middleware
 
 import (

backend-go/internal/models/address.go

@@ -2,7 +2,9 @@ package models
 
 import (
 	"context"
+	"errors"
 
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
@@ -97,7 +99,25 @@ func (m *AddressModel) FindByID(ctx context.Context, id int, userID *string) (*d
 	}
 
 	if err != nil {
-		if err.Error() == "no rows in result set" {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, nil
+		}
+		return nil, err
+	}
+	return &a, nil
+}
+
+// UpdateLabel updates the label for an address owned by userID.
+// Returns nil, nil if no row matched (address not found or not owned by user).
+func (m *AddressModel) UpdateLabel(ctx context.Context, id int, userID string, label *string) (*domain.Address, error) {
+	var a domain.Address
+	err := m.pool.QueryRow(ctx,
+		`UPDATE addresses SET label = $3 WHERE id = $1 AND user_id = $2
+		 RETURNING id, user_id, address, label, created_at`,
+		id, userID, label,
+	).Scan(&a.ID, &a.UserID, &a.Address, &a.Label, &a.CreatedAt)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
 			return nil, nil
 		}
 		return nil, err

backend-go/internal/models/alert_event.go

@@ -2,7 +2,9 @@ package models
 
 import (
 	"context"
+	"errors"
 
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
@@ -71,10 +73,15 @@ func (m *AlertEventModel) Create(ctx context.Context, alertRuleID int, message s
 	err := m.pool.QueryRow(ctx,
 		`INSERT INTO alert_events (alert_rule_id, message, address_label, tx_hash)
 		 VALUES ($1, $2, $3, $4)
+		 ON CONFLICT DO NOTHING
 		 RETURNING id, alert_rule_id, message, address_label, tx_hash, timestamp`,
 		alertRuleID, message, addressLabel, txHash,
 	).Scan(&e.ID, &e.AlertRuleID, &e.Message, &e.AddressLabel, &e.TxHash, &e.Timestamp)
 	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			// Duplicate silently skipped by ON CONFLICT DO NOTHING
+			return nil, nil
+		}
 		return nil, err
 	}
 	return &e, nil

backend-go/internal/models/alert_rule.go

@@ -2,7 +2,9 @@ package models
 
 import (
 	"context"
+	"errors"
 
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
@@ -21,7 +23,7 @@ func (m *AlertRuleModel) Create(ctx context.Context, addressID int, alertType do
 		`INSERT INTO alert_rules (address_id, type, threshold, enabled)
 		 VALUES ($1, $2, $3, TRUE)
 		 RETURNING id, address_id, type, threshold, enabled, created_at`,
-		addressID, string(alertType), threshold,
+		addressID, alertType.String(), threshold,
 	).Scan(&r.ID, &r.AddressID, &r.Type, &r.Threshold, &r.Enabled, &r.CreatedAt)
 	if err != nil {
 		return nil, err
@@ -75,7 +77,7 @@ func (m *AlertRuleModel) FindByID(ctx context.Context, id int, userID *string) (
 	}
 
 	if err != nil {
-		if err.Error() == "no rows in result set" {
+		if errors.Is(err, pgx.ErrNoRows) {
 			return nil, nil
 		}
 		return nil, err
@@ -93,7 +95,7 @@ func (m *AlertRuleModel) UpdateEnabled(ctx context.Context, id int, enabled bool
 		id, enabled,
 	).Scan(&r.ID, &r.AddressID, &r.Type, &r.Threshold, &r.Enabled, &r.CreatedAt)
 	if err != nil {
-		if err.Error() == "no rows in result set" {
+		if errors.Is(err, pgx.ErrNoRows) {
 			return nil, nil
 		}
 		return nil, err

backend-go/internal/models/checkpoint.go

@@ -2,7 +2,10 @@ package models
 
 import (
 	"context"
+	"errors"
+	"time"
 
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
@@ -15,6 +18,20 @@ func NewCheckpointModel(pool *pgxpool.Pool) *CheckpointModel {
 	return &CheckpointModel{pool: pool}
 }
 
+// GetLatestBlock returns the highest last_checked_block and its timestamp across all addresses.
+// Returns nil, nil, nil when no checkpoints exist yet.
+func (m *CheckpointModel) GetLatestBlock(ctx context.Context) (*int, *time.Time, error) {
+	var block *int
+	var checkedAt *time.Time
+	err := m.pool.QueryRow(ctx,
+		`SELECT MAX(last_checked_block), MAX(last_checked_at) FROM address_checkpoints`,
+	).Scan(&block, &checkedAt)
+	if err != nil {
+		return nil, nil, err
+	}
+	return block, checkedAt, nil
+}
+
 // GetLastCheckedBlock returns the last checked block for an address, or -1 if never checked.
 func (m *CheckpointModel) GetLastCheckedBlock(ctx context.Context, addressID int) (int, bool, error) {
 	var block int
@@ -23,7 +40,7 @@ func (m *CheckpointModel) GetLastCheckedBlock(ctx context.Context, addressID int
 		addressID,
 	).Scan(&block)
 	if err != nil {
-		if err.Error() == "no rows in result set" {
+		if errors.Is(err, pgx.ErrNoRows) {
 			return 0, false, nil
 		}
 		return 0, false, err

backend-go/internal/models/notification_config.go

@@ -2,7 +2,9 @@ package models
 
 import (
 	"context"
+	"errors"
 
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
@@ -19,14 +21,14 @@ func (m *NotificationConfigModel) GetConfig(ctx context.Context, userID string)
 	var c domain.NotificationConfig
 	err := m.pool.QueryRow(ctx,
 		`SELECT user_id, discord_webhook_url, telegram_chat_id, telegram_bot_token,
-		        email, notification_enabled, created_at, updated_at
+		        email, slack_webhook_url, notification_enabled, created_at, updated_at
 		 FROM user_notification_configs
 		 WHERE user_id = $1`,
 		userID,
 	).Scan(&c.UserID, &c.DiscordWebhookURL, &c.TelegramChatID, &c.TelegramBotToken,
-		&c.Email, &c.NotificationEnabled, &c.CreatedAt, &c.UpdatedAt)
+		&c.Email, &c.SlackWebhookURL, &c.NotificationEnabled, &c.CreatedAt, &c.UpdatedAt)
 	if err != nil {
-		if err.Error() == "no rows in result set" {
+		if errors.Is(err, pgx.ErrNoRows) {
 			return nil, nil
 		}
 		return nil, err
@@ -38,22 +40,24 @@ func (m *NotificationConfigModel) UpsertConfig(ctx context.Context, userID strin
 	var c domain.NotificationConfig
 	err := m.pool.QueryRow(ctx,
 		`INSERT INTO user_notification_configs
-		   (user_id, discord_webhook_url, telegram_chat_id, telegram_bot_token, email, notification_enabled, updated_at)
-		 VALUES ($1, $2, $3, $4, $5, $6, NOW())
+		   (user_id, discord_webhook_url, telegram_chat_id, telegram_bot_token,
+		    email, slack_webhook_url, notification_enabled, updated_at)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7, NOW())
 		 ON CONFLICT (user_id)
 		 DO UPDATE SET
-		   discord_webhook_url = COALESCE($2, user_notification_configs.discord_webhook_url),
-		   telegram_chat_id = COALESCE($3, user_notification_configs.telegram_chat_id),
-		   telegram_bot_token = COALESCE($4, user_notification_configs.telegram_bot_token),
-		   email = COALESCE($5, user_notification_configs.email),
-		   notification_enabled = $6,
+		   discord_webhook_url = $2,
+		   telegram_chat_id = $3,
+		   telegram_bot_token = $4,
+		   email = $5,
+		   slack_webhook_url = $6,
+		   notification_enabled = $7,
 		   updated_at = NOW()
 		 RETURNING user_id, discord_webhook_url, telegram_chat_id, telegram_bot_token,
-		           email, notification_enabled, created_at, updated_at`,
+		           email, slack_webhook_url, notification_enabled, created_at, updated_at`,
 		userID, cfg.DiscordWebhookURL, cfg.TelegramChatID, cfg.TelegramBotToken,
-		cfg.Email, cfg.NotificationEnabled,
+		cfg.Email, cfg.SlackWebhookURL, cfg.NotificationEnabled,
 	).Scan(&c.UserID, &c.DiscordWebhookURL, &c.TelegramChatID, &c.TelegramBotToken,
-		&c.Email, &c.NotificationEnabled, &c.CreatedAt, &c.UpdatedAt)
+		&c.Email, &c.SlackWebhookURL, &c.NotificationEnabled, &c.CreatedAt, &c.UpdatedAt)
 	if err != nil {
 		return nil, err
 	}
@@ -73,7 +77,8 @@ func (m *NotificationConfigModel) Remove(ctx context.Context, userID string) (bo
 
 func (m *NotificationConfigModel) ListEnabled(ctx context.Context) ([]domain.NotificationConfig, error) {
 	rows, err := m.pool.Query(ctx,
-		`SELECT user_id, discord_webhook_url, telegram_chat_id, email
+		`SELECT user_id, discord_webhook_url, telegram_chat_id, telegram_bot_token,
+		        email, slack_webhook_url
 		 FROM user_notification_configs
 		 WHERE notification_enabled = TRUE`,
 	)
@@ -85,7 +90,8 @@ func (m *NotificationConfigModel) ListEnabled(ctx context.Context) ([]domain.Not
 	var configs []domain.NotificationConfig
 	for rows.Next() {
 		var c domain.NotificationConfig
-		if err := rows.Scan(&c.UserID, &c.DiscordWebhookURL, &c.TelegramChatID, &c.Email); err != nil {
+		if err := rows.Scan(&c.UserID, &c.DiscordWebhookURL, &c.TelegramChatID,
+			&c.TelegramBotToken, &c.Email, &c.SlackWebhookURL); err != nil {
 			return nil, err
 		}
 		c.NotificationEnabled = true

backend-go/internal/notifications/discord.go

@@ -2,6 +2,7 @@ package notifications
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -9,11 +10,31 @@ import (
 	"time"
 )
 
-type AlertMetadata struct {
-	TxHash       string
-	AddressLabel string
-	AlertType    string
-	Address      string
+const (
+	// discordHTTPTimeoutSeconds is the timeout for Discord webhook requests.
+	discordHTTPTimeoutSeconds = 10
+
+	// Alert color codes for Discord embeds.
+	colorGreen  = 0x00ff00
+	colorOrange = 0xff9900
+	colorRed    = 0xff0000
+	colorBlue   = 0x0099ff
+)
+
+// discordHTTPClient is a shared HTTP client with a timeout for Discord requests.
+var discordHTTPClient = &http.Client{ //nolint:gochecknoglobals
+	Timeout: discordHTTPTimeoutSeconds * time.Second,
+}
+
+// DiscordNotifier sends alert notifications via a Discord webhook.
+type DiscordNotifier struct {
+	WebhookURL string
+}
+
+// Send implements Notifier for Discord.
+func (d *DiscordNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendDiscordNotification(d.WebhookURL, message, meta)
+	return err
 }
 
 type discordEmbed struct {
@@ -73,7 +94,9 @@ func SendDiscordNotification(webhookURL, message string, meta AlertMetadata) (bo
 		return false, fmt.Errorf("marshal discord payload: %w", err)
 	}
 
-	resp, err := http.Post(webhookURL, "application/json", bytes.NewReader(body))
+	resp, err := discordHTTPClient.Post(
+		webhookURL, "application/json", bytes.NewReader(body),
+	)
 	if err != nil {
 		log.Printf("Failed to send Discord notification: %v", err)
 		return false, err
@@ -98,7 +121,9 @@ func TestDiscordWebhook(webhookURL string) (bool, error) {
 		return false, err
 	}
 
-	resp, err := http.Post(webhookURL, "application/json", bytes.NewReader(body))
+	resp, err := discordHTTPClient.Post(
+		webhookURL, "application/json", bytes.NewReader(body),
+	)
 	if err != nil {
 		log.Printf("Discord webhook test failed: %v", err)
 		return false, err
@@ -111,14 +136,14 @@ func TestDiscordWebhook(webhookURL string) (bool, error) {
 func colorForAlertType(alertType string) int {
 	switch alertType {
 	case "incoming_tx":
-		return 0x00ff00 // Green
+		return colorGreen
 	case "outgoing_tx":
-		return 0xff9900 // Orange
+		return colorOrange
 	case "large_transfer":
-		return 0xff0000 // Red
+		return colorRed
 	case "balance_below":
-		return 0xff0000 // Red
+		return colorRed
 	default:
-		return 0x0099ff // Blue
+		return colorBlue
 	}
 }

backend-go/internal/notifications/email.go

@@ -0,0 +1,156 @@
+package notifications
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+)
+
+// EmailNotifier sends alert notifications via email (Resend).
+type EmailNotifier struct {
+	APIKey string
+	From   string
+	To     string
+}
+
+// Send implements Notifier for email.
+func (e *EmailNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendEmailNotification(e.APIKey, e.From, e.To, message, meta)
+	return err
+}
+
+const emailHTTPTimeoutSeconds = 10
+
+var emailHTTPClient = &http.Client{ //nolint:gochecknoglobals
+	Timeout: emailHTTPTimeoutSeconds * time.Second,
+}
+
+type resendPayload struct {
+	From    string `json:"from"`
+	To      string `json:"to"`
+	Subject string `json:"subject"`
+	HTML    string `json:"html"`
+}
+
+func SendEmailNotification(apiKey, fromAddress, toAddress, message string, meta AlertMetadata) (bool, error) {
+	if apiKey == "" {
+		log.Printf("Skipping email notification: RESEND_API_KEY not configured")
+		return false, nil
+	}
+
+	subject := fmt.Sprintf("Koin Ping Alert: %s", alertTypeLabel(meta.AlertType))
+
+	txLink := ""
+	if meta.TxHash != "" {
+		txLink = fmt.Sprintf(
+			`<p><a href="https://etherscan.io/tx/%s">View on Etherscan</a></p>`,
+			meta.TxHash,
+		)
+	}
+
+	html := fmt.Sprintf(`
+<div style="font-family: sans-serif; max-width: 600px; margin: 0 auto;">
+  <h2 style="color: #333;">Koin Ping Alert</h2>
+  <p style="font-size: 16px;">%s</p>
+  <table style="margin: 16px 0; border-collapse: collapse;">
+    <tr>
+      <td style="padding: 4px 12px 4px 0; color: #666;">Address</td>
+      <td style="padding: 4px 0;">%s</td>
+    </tr>
+    <tr>
+      <td style="padding: 4px 12px 4px 0; color: #666;">Blockchain</td>
+      <td style="padding: 4px 0; font-family: monospace; font-size: 13px;">%s</td>
+    </tr>
+  </table>
+  %s
+  <hr style="border: none; border-top: 1px solid #eee; margin: 24px 0;" />
+  <p style="font-size: 12px; color: #999;">Sent by Koin Ping</p>
+</div>`,
+		message, meta.AddressLabel, meta.Address, txLink)
+
+	payload := resendPayload{
+		From:    fromAddress,
+		To:      toAddress,
+		Subject: subject,
+		HTML:    html,
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return false, fmt.Errorf("marshal email payload: %w", err)
+	}
+
+	req, err := http.NewRequest(http.MethodPost, "https://api.resend.com/emails", bytes.NewReader(body))
+	if err != nil {
+		return false, fmt.Errorf("create email request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", "Bearer "+apiKey)
+
+	resp, err := emailHTTPClient.Do(req)
+	if err != nil {
+		log.Printf("Failed to send email notification: %v", err)
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		log.Printf("Resend API failed: HTTP %d", resp.StatusCode)
+		return false, fmt.Errorf("resend API failed: HTTP %d", resp.StatusCode)
+	}
+
+	return true, nil
+}
+
+func TestEmailNotification(apiKey, fromAddress, toAddress string) (bool, error) {
+	if apiKey == "" {
+		return false, fmt.Errorf("email not configured: RESEND_API_KEY not set") //nolint:err113
+	}
+
+	payload := resendPayload{
+		From:    fromAddress,
+		To:      toAddress,
+		Subject: "Koin Ping — Test Notification",
+		HTML:    `<p>Your email alerts are configured correctly!</p><p style="font-size:12px;color:#999;">Sent by Koin Ping</p>`,
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return false, err
+	}
+
+	req, err := http.NewRequest(http.MethodPost, "https://api.resend.com/emails", bytes.NewReader(body))
+	if err != nil {
+		return false, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", "Bearer "+apiKey)
+
+	resp, err := emailHTTPClient.Do(req)
+	if err != nil {
+		log.Printf("Email test failed: %v", err)
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	return resp.StatusCode >= 200 && resp.StatusCode < 300, nil
+}
+
+func alertTypeLabel(alertType string) string {
+	switch alertType {
+	case "incoming_tx":
+		return "Incoming Transaction"
+	case "outgoing_tx":
+		return "Outgoing Transaction"
+	case "large_transfer":
+		return "Large Transfer"
+	case "balance_below":
+		return "Balance Below Threshold"
+	default:
+		return "Alert"
+	}
+}

backend-go/internal/notifications/notifier.go

@@ -0,0 +1,16 @@
+package notifications
+
+import "context"
+
+// AlertMetadata holds context about the alert being sent.
+type AlertMetadata struct {
+	TxHash       string
+	AddressLabel string
+	AlertType    string
+	Address      string
+}
+
+// Notifier is the interface implemented by all notification channels.
+type Notifier interface {
+	Send(ctx context.Context, message string, meta AlertMetadata) error
+}

backend-go/internal/notifications/slack.go

@@ -0,0 +1,128 @@
+package notifications
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+)
+
+// SlackNotifier sends alert notifications via a Slack webhook.
+type SlackNotifier struct {
+	WebhookURL string
+}
+
+// Send implements Notifier for Slack.
+func (s *SlackNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendSlackNotification(s.WebhookURL, message, meta)
+	return err
+}
+
+const slackHTTPTimeoutSeconds = 10
+
+var slackHTTPClient = &http.Client{ //nolint:gochecknoglobals
+	Timeout: slackHTTPTimeoutSeconds * time.Second,
+}
+
+type slackAttachment struct {
+	Color  string        `json:"color"`
+	Title  string        `json:"title"`
+	Text   string        `json:"text"`
+	Fields []slackField  `json:"fields"`
+	Footer string        `json:"footer"`
+	Ts     int64         `json:"ts"`
+}
+
+type slackField struct {
+	Title string `json:"title"`
+	Value string `json:"value"`
+	Short bool   `json:"short"`
+}
+
+type slackPayload struct {
+	Text        string            `json:"text,omitempty"`
+	Attachments []slackAttachment `json:"attachments,omitempty"`
+}
+
+func SendSlackNotification(webhookURL, message string, meta AlertMetadata) (bool, error) {
+	fields := []slackField{
+		{Title: "Address", Value: meta.AddressLabel, Short: true},
+		{Title: "Blockchain Address", Value: fmt.Sprintf("`%s`", meta.Address), Short: false},
+	}
+
+	if meta.TxHash != "" {
+		fields = append(fields, slackField{
+			Title: "Transaction",
+			Value: fmt.Sprintf("<https://etherscan.io/tx/%s|View on Etherscan>", meta.TxHash),
+			Short: false,
+		})
+	}
+
+	payload := slackPayload{
+		Attachments: []slackAttachment{
+			{
+				Color:  slackColorForAlertType(meta.AlertType),
+				Title:  "Koin Ping Alert",
+				Text:   message,
+				Fields: fields,
+				Footer: "Koin Ping",
+				Ts:     time.Now().Unix(),
+			},
+		},
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return false, fmt.Errorf("marshal slack payload: %w", err)
+	}
+
+	resp, err := slackHTTPClient.Post(webhookURL, "application/json", bytes.NewReader(body))
+	if err != nil {
+		log.Printf("Failed to send Slack notification: %v", err)
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		log.Printf("Slack webhook failed: HTTP %d", resp.StatusCode)
+		return false, fmt.Errorf("slack webhook failed: HTTP %d", resp.StatusCode)
+	}
+
+	return true, nil
+}
+
+func TestSlackWebhook(webhookURL string) (bool, error) {
+	payload := slackPayload{
+		Text: "Koin Ping test notification — Your Slack alerts are configured correctly!",
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return false, err
+	}
+
+	resp, err := slackHTTPClient.Post(webhookURL, "application/json", bytes.NewReader(body))
+	if err != nil {
+		log.Printf("Slack webhook test failed: %v", err)
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	return resp.StatusCode >= 200 && resp.StatusCode < 300, nil
+}
+
+func slackColorForAlertType(alertType string) string {
+	switch alertType {
+	case "incoming_tx":
+		return "#00ff00"
+	case "outgoing_tx":
+		return "#ff9900"
+	case "large_transfer", "balance_below":
+		return "#ff0000"
+	default:
+		return "#0099ff"
+	}
+}

backend-go/internal/notifications/telegram.go

@@ -0,0 +1,122 @@
+package notifications
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+)
+
+// TelegramNotifier sends alert notifications via Telegram.
+type TelegramNotifier struct {
+	BotToken string
+	ChatID   string
+}
+
+// Send implements Notifier for Telegram.
+func (t *TelegramNotifier) Send(_ context.Context, message string, meta AlertMetadata) error {
+	_, err := SendTelegramNotification(t.BotToken, t.ChatID, message, meta)
+	return err
+}
+
+const telegramHTTPTimeoutSeconds = 10
+
+var telegramHTTPClient = &http.Client{ //nolint:gochecknoglobals
+	Timeout: telegramHTTPTimeoutSeconds * time.Second,
+}
+
+type telegramPayload struct {
+	ChatID    string `json:"chat_id"`
+	Text      string `json:"text"`
+	ParseMode string `json:"parse_mode"`
+}
+
+func SendTelegramNotification(botToken, chatID, message string, meta AlertMetadata) (bool, error) {
+	text := fmt.Sprintf("*Koin Ping Alert*\n\n%s\n\n*Address:* %s\n`%s`",
+		escapeMarkdown(message), escapeMarkdown(meta.AddressLabel), meta.Address)
+
+	if meta.TxHash != "" {
+		text += fmt.Sprintf("\n\n[View on Etherscan](https://etherscan.io/tx/%s)", meta.TxHash)
+	}
+
+	payload := telegramPayload{
+		ChatID:    chatID,
+		Text:      text,
+		ParseMode: "Markdown",
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return false, fmt.Errorf("marshal telegram payload: %w", err)
+	}
+
+	url := fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", botToken)
+
+	resp, err := telegramHTTPClient.Post(url, "application/json", bytes.NewReader(body))
+	if err != nil {
+		log.Printf("Failed to send Telegram notification: %v", err)
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		log.Printf("Telegram API failed: HTTP %d", resp.StatusCode)
+		return false, fmt.Errorf("telegram API failed: HTTP %d", resp.StatusCode)
+	}
+
+	return true, nil
+}
+
+func TestTelegramWebhook(botToken, chatID string) (bool, error) {
+	payload := telegramPayload{
+		ChatID:    chatID,
+		Text:      "Koin Ping test notification — Your Telegram alerts are configured correctly!",
+		ParseMode: "Markdown",
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return false, err
+	}
+
+	url := fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", botToken)
+
+	resp, err := telegramHTTPClient.Post(url, "application/json", bytes.NewReader(body))
+	if err != nil {
+		log.Printf("Telegram test failed: %v", err)
+		return false, err
+	}
+	defer resp.Body.Close()
+
+	return resp.StatusCode >= 200 && resp.StatusCode < 300, nil
+}
+
+func escapeMarkdown(s string) string {
+	replacer := []struct{ old, new string }{
+		{"_", "\\_"}, {"*", "\\*"}, {"[", "\\["}, {"]", "\\]"},
+		{"(", "\\("}, {")", "\\)"}, {"~", "\\~"}, {"`", "\\`"},
+		{">", "\\>"}, {"#", "\\#"}, {"+", "\\+"}, {"-", "\\-"},
+		{"=", "\\="}, {"|", "\\|"}, {"{", "\\{"}, {"}", "\\}"},
+		{".", "\\."}, {"!", "\\!"},
+	}
+	result := s
+	for _, r := range replacer {
+		result = replaceAll(result, r.old, r.new)
+	}
+	return result
+}
+
+func replaceAll(s, old, new string) string {
+	out := ""
+	for i := 0; i < len(s); i++ {
+		if string(s[i]) == old {
+			out += new
+		} else {
+			out += string(s[i])
+		}
+	}
+	return out
+}

backend-go/internal/protocols/ethereum/jsonrpc.go

@@ -4,7 +4,9 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"log"
 	"math/big"
 	"net/http"
 	"strings"
@@ -13,7 +15,11 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 )
 
-const rpcTimeoutMS = 30000
+const (
+	rpcTimeoutMS    = 30000
+	rpcMaxRetries   = 3
+	rpcRetryBaseMS  = 1000
+)
 
 type JsonRpcEthereum struct {
 	rpcURL string
@@ -66,6 +72,44 @@ func (j *JsonRpcEthereum) callRPC(ctx context.Context, method string, params ...
 		return nil, fmt.Errorf("marshal RPC request: %w", err)
 	}
 
+	return j.callWithRetry(ctx, method, body)
+}
+
+// callWithRetry executes a JSON-RPC POST with exponential backoff on transient errors.
+// It retries on network errors, HTTP 429, and HTTP 5xx. It does NOT retry on RPC-level
+// errors or other 4xx responses (those are permanent failures).
+func (j *JsonRpcEthereum) callWithRetry(ctx context.Context, method string, body []byte) (json.RawMessage, error) {
+	var lastErr error
+	for attempt := range rpcMaxRetries {
+		if attempt > 0 {
+			wait := time.Duration(rpcRetryBaseMS*(1<<(attempt-1))) * time.Millisecond
+			select {
+			case <-ctx.Done():
+				return nil, ctx.Err()
+			case <-time.After(wait):
+			}
+			log.Printf("Retrying RPC call [%s] (attempt %d/%d)", method, attempt+1, rpcMaxRetries)
+		}
+
+		result, err := j.doRPCCall(ctx, method, body)
+		if err == nil {
+			return result, nil
+		}
+
+		lastErr = err
+
+		// Permanent errors: do not retry
+		if isPermanentRPCError(err) {
+			return nil, err
+		}
+
+		log.Printf("Transient RPC error [%s] (attempt %d/%d): %v", method, attempt+1, rpcMaxRetries, err)
+	}
+
+	return nil, lastErr
+}
+
+func (j *JsonRpcEthereum) doRPCCall(ctx context.Context, method string, body []byte) (json.RawMessage, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodPost, j.rpcURL, bytes.NewReader(body))
 	if err != nil {
 		return nil, fmt.Errorf("create RPC request: %w", err)
@@ -78,8 +122,13 @@ func (j *JsonRpcEthereum) callRPC(ctx context.Context, method string, params ...
 	}
 	defer resp.Body.Close()
 
+	// 429 and 5xx are transient; other non-200 are permanent.
 	if resp.StatusCode != http.StatusOK {
-		return nil, fmt.Errorf("HTTP %d: %s for %s", resp.StatusCode, resp.Status, method)
+		err := fmt.Errorf("HTTP %d: %s for %s", resp.StatusCode, resp.Status, method)
+		if resp.StatusCode == http.StatusTooManyRequests || resp.StatusCode >= 500 { //nolint:mnd
+			return nil, err // transient — will be retried
+		}
+		return nil, &permanentRPCError{err}
 	}
 
 	var rpcResp rpcResponse
@@ -88,12 +137,25 @@ func (j *JsonRpcEthereum) callRPC(ctx context.Context, method string, params ...
 	}
 
 	if rpcResp.Error != nil {
-		return nil, fmt.Errorf("RPC Error [%s]: %s (code: %d)", method, rpcResp.Error.Message, rpcResp.Error.Code)
+		// RPC-level errors are permanent (bad params, unsupported method, etc.)
+		return nil, &permanentRPCError{
+			fmt.Errorf("RPC Error [%s]: %s (code: %d)", method, rpcResp.Error.Message, rpcResp.Error.Code),
+		}
 	}
 
 	return rpcResp.Result, nil
 }
 
+type permanentRPCError struct{ cause error }
+
+func (e *permanentRPCError) Error() string { return e.cause.Error() }
+func (e *permanentRPCError) Unwrap() error { return e.cause }
+
+func isPermanentRPCError(err error) bool {
+	var p *permanentRPCError
+	return errors.As(err, &p)
+}
+
 func (j *JsonRpcEthereum) GetLatestBlockNumber(ctx context.Context) (int, error) {
 	result, err := j.callRPC(ctx, "eth_blockNumber")
 	if err != nil {

backend-go/internal/services/email_digest.go

@@ -0,0 +1,199 @@
+package services
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"time"
+
+	"github.com/kjannette/koin-ping/backend-go/internal/models"
+)
+
+const (
+	resendAPIURL          = "https://api.resend.com/emails"
+	emailHTTPTimeout      = 10 * time.Second
+	defaultDigestMaxItems = 50
+)
+
+var digestHTTPClient = &http.Client{Timeout: emailHTTPTimeout} //nolint:gochecknoglobals
+
+// EmailDigestService handles email setup and digest sending via Resend.
+type EmailDigestService struct {
+	apiKey      string
+	fromAddress string
+	alertEvents *models.AlertEventModel
+	notifCfgs   *models.NotificationConfigModel
+}
+
+func NewEmailDigestService(
+	apiKey, fromAddress string,
+	alertEvents *models.AlertEventModel,
+	notifCfgs *models.NotificationConfigModel,
+) *EmailDigestService {
+	return &EmailDigestService{
+		apiKey:      apiKey,
+		fromAddress: fromAddress,
+		alertEvents: alertEvents,
+		notifCfgs:   notifCfgs,
+	}
+}
+
+// Configured returns true when the Resend API key is present.
+func (s *EmailDigestService) Configured() bool {
+	return s.apiKey != ""
+}
+
+// SetupEmail validates the email works by sending a welcome/confirmation
+// message via Resend. Called when a user saves their email in notification settings.
+func (s *EmailDigestService) SetupEmail(toAddress string) error {
+	if !s.Configured() {
+		return fmt.Errorf("email service not configured: RESEND_API_KEY not set") //nolint:err113
+	}
+
+	html := `
+<div style="font-family: sans-serif; max-width: 600px; margin: 0 auto;">
+  <h2 style="color: #333;">Welcome to Koin Ping Email Alerts</h2>
+  <p>Your email has been successfully configured for alert notifications.</p>
+  <p>You will receive alert digests at this address when events are triggered
+     on your watched addresses.</p>
+  <hr style="border: none; border-top: 1px solid #eee; margin: 24px 0;" />
+  <p style="font-size: 12px; color: #999;">Sent by Koin Ping</p>
+</div>`
+
+	return s.send(toAddress, "Koin Ping — Email Alerts Configured", html)
+}
+
+// SendDigest compiles recent alert events for a user and sends a digest email.
+func (s *EmailDigestService) SendDigest(ctx context.Context, userID, toAddress string) error {
+	if !s.Configured() {
+		return fmt.Errorf("email service not configured: RESEND_API_KEY not set") //nolint:err113
+	}
+
+	events, err := s.alertEvents.ListRecentByUser(ctx, userID, defaultDigestMaxItems)
+	if err != nil {
+		return fmt.Errorf("fetch alert events: %w", err)
+	}
+
+	if len(events) == 0 {
+		log.Printf("No recent alerts for user %s — skipping digest", userID)
+		return nil
+	}
+
+	var rows string
+	for _, e := range events {
+		label := "—"
+		if e.AddressLabel != nil {
+			label = *e.AddressLabel
+		}
+		txLink := "—"
+		if e.TxHash != nil {
+			txLink = fmt.Sprintf(
+				`<a href="https://etherscan.io/tx/%s" style="color:#0066cc;">%s…</a>`,
+				*e.TxHash, (*e.TxHash)[:10],
+			)
+		}
+		rows += fmt.Sprintf(`
+      <tr>
+        <td style="padding:6px 8px; border-bottom:1px solid #eee;">%s</td>
+        <td style="padding:6px 8px; border-bottom:1px solid #eee;">%s</td>
+        <td style="padding:6px 8px; border-bottom:1px solid #eee;">%s</td>
+        <td style="padding:6px 8px; border-bottom:1px solid #eee; font-size:12px; color:#666;">%s</td>
+      </tr>`,
+			label, e.Message, txLink,
+			e.Timestamp.Format("Jan 2 15:04 UTC"),
+		)
+	}
+
+	html := fmt.Sprintf(`
+<div style="font-family: sans-serif; max-width: 700px; margin: 0 auto;">
+  <h2 style="color: #333;">Koin Ping — Alert Digest</h2>
+  <p>Here are your recent alerts (%d total):</p>
+  <table style="width:100%%; border-collapse:collapse; font-size:14px;">
+    <thead>
+      <tr style="background:#f5f5f5;">
+        <th style="padding:8px; text-align:left;">Address</th>
+        <th style="padding:8px; text-align:left;">Alert</th>
+        <th style="padding:8px; text-align:left;">Tx</th>
+        <th style="padding:8px; text-align:left;">Time</th>
+      </tr>
+    </thead>
+    <tbody>%s</tbody>
+  </table>
+  <hr style="border:none; border-top:1px solid #eee; margin:24px 0;" />
+  <p style="font-size:12px; color:#999;">Sent by Koin Ping</p>
+</div>`, len(events), rows)
+
+	subject := fmt.Sprintf("Koin Ping Digest — %d alerts", len(events))
+
+	return s.send(toAddress, subject, html)
+}
+
+// SendDigestsForAllUsers sends a digest email to every user that has
+// notifications enabled and an email configured.
+func (s *EmailDigestService) SendDigestsForAllUsers(ctx context.Context) (int, error) {
+	if !s.Configured() {
+		return 0, nil
+	}
+
+	configs, err := s.notifCfgs.ListEnabled(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("list enabled configs: %w", err)
+	}
+
+	sent := 0
+	for _, cfg := range configs {
+		if cfg.Email == nil || *cfg.Email == "" {
+			continue
+		}
+		if err := s.SendDigest(ctx, cfg.UserID, *cfg.Email); err != nil {
+			log.Printf("Failed to send digest to user %s: %v", cfg.UserID, err)
+			continue
+		}
+		sent++
+	}
+
+	return sent, nil
+}
+
+type resendEmailPayload struct {
+	From    string `json:"from"`
+	To      string `json:"to"`
+	Subject string `json:"subject"`
+	HTML    string `json:"html"`
+}
+
+func (s *EmailDigestService) send(to, subject, html string) error {
+	payload := resendEmailPayload{
+		From:    s.fromAddress,
+		To:      to,
+		Subject: subject,
+		HTML:    html,
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("marshal email payload: %w", err)
+	}
+
+	req, err := http.NewRequest(http.MethodPost, resendAPIURL, bytes.NewReader(body))
+	if err != nil {
+		return fmt.Errorf("create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", "Bearer "+s.apiKey)
+
+	resp, err := digestHTTPClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("send email via Resend: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return fmt.Errorf("Resend API returned HTTP %d", resp.StatusCode) //nolint:err113
+	}
+
+	return nil
+}

backend-go/internal/services/evaluator.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"time"
 
 	"github.com/kjannette/koin-ping/backend-go/internal/domain"
 	"github.com/kjannette/koin-ping/backend-go/internal/models"
@@ -12,12 +13,20 @@ import (
 	"github.com/kjannette/koin-ping/backend-go/internal/wei"
 )
 
+const (
+	notificationTimeout    = 30 * time.Second
+	notificationMaxRetries = 3
+	notificationRetryBase  = time.Second
+)
+
 type EvaluatorService struct {
 	eth          ethereum.EthereumObserver
 	alertRules   *models.AlertRuleModel
 	alertEvents  *models.AlertEventModel
 	addresses    *models.AddressModel
 	notifConfigs *models.NotificationConfigModel
+	resendAPIKey string
+	emailFrom    string
 }
 
 func NewEvaluatorService(
@@ -26,6 +35,8 @@ func NewEvaluatorService(
 	alertEvents *models.AlertEventModel,
 	addresses *models.AddressModel,
 	notifConfigs *models.NotificationConfigModel,
+	resendAPIKey string,
+	emailFrom string,
 ) *EvaluatorService {
 	return &EvaluatorService{
 		eth:          eth,
@@ -33,6 +44,8 @@ func NewEvaluatorService(
 		alertEvents:  alertEvents,
 		addresses:    addresses,
 		notifConfigs: notifConfigs,
+		resendAPIKey: resendAPIKey,
+		emailFrom:    emailFrom,
 	}
 }
 
@@ -161,21 +174,85 @@ func (s *EvaluatorService) fireAlert(ctx context.Context, rule domain.AlertRule,
 	message := s.buildMessage(rule, obs)
 	txHash := &obs.Hash
 
-	_, err = s.alertEvents.Create(ctx, rule.ID, message, &addressLabel, txHash)
+	event, err := s.alertEvents.Create(ctx, rule.ID, message, &addressLabel, txHash)
 	if err != nil {
 		return err
 	}
 
+	if event == nil {
+		log.Printf("[ALERT DEDUP] Rule %d (%s) - duplicate event skipped for TX: %s", rule.ID, rule.Type, obs.Hash)
+		return nil
+	}
+
 	log.Printf("[ALERT FIRED] Rule %d (%s) - %s - TX: %s", rule.ID, rule.Type, message, obs.Hash)
 
-	// Send Discord notification (non-fatal on failure)
 	if addr != nil {
-		go s.sendNotification(ctx, addr.UserID, message, obs, addressLabel, rule, addr.Address)
+		userID := addr.UserID
+		address := addr.Address
+		go func() {
+			notifCtx, cancel := context.WithTimeout(context.Background(), notificationTimeout)
+			defer cancel()
+			s.sendNotification(notifCtx, userID, message, obs, addressLabel, rule, address)
+		}()
 	}
 
 	return nil
 }
 
+func (s *EvaluatorService) buildNotifiers(cfg *domain.NotificationConfig) []notifications.Notifier {
+	var notifiers []notifications.Notifier
+
+	if cfg.DiscordWebhookURL != nil && *cfg.DiscordWebhookURL != "" {
+		notifiers = append(notifiers, &notifications.DiscordNotifier{WebhookURL: *cfg.DiscordWebhookURL})
+	}
+
+	if cfg.TelegramBotToken != nil && *cfg.TelegramBotToken != "" &&
+		cfg.TelegramChatID != nil && *cfg.TelegramChatID != "" {
+		notifiers = append(notifiers, &notifications.TelegramNotifier{
+			BotToken: *cfg.TelegramBotToken,
+			ChatID:   *cfg.TelegramChatID,
+		})
+	}
+
+	if cfg.SlackWebhookURL != nil && *cfg.SlackWebhookURL != "" {
+		notifiers = append(notifiers, &notifications.SlackNotifier{WebhookURL: *cfg.SlackWebhookURL})
+	}
+
+	if cfg.Email != nil && *cfg.Email != "" {
+		notifiers = append(notifiers, &notifications.EmailNotifier{
+			APIKey: s.resendAPIKey,
+			From:   s.emailFrom,
+			To:     *cfg.Email,
+		})
+	}
+
+	return notifiers
+}
+
+func sendWithRetry(ctx context.Context, n notifications.Notifier, message string, meta notifications.AlertMetadata) error {
+	var lastErr error
+	for attempt := range notificationMaxRetries {
+		if attempt > 0 {
+			wait := notificationRetryBase * time.Duration(1<<(attempt-1))
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-time.After(wait):
+			}
+		}
+
+		if err := n.Send(ctx, message, meta); err != nil {
+			log.Printf("Notification attempt %d/%d failed: %v", attempt+1, notificationMaxRetries, err)
+			lastErr = err
+			continue
+		}
+
+		return nil
+	}
+
+	return lastErr
+}
+
 func (s *EvaluatorService) sendNotification(ctx context.Context, userID, message string, obs domain.ObservedTx, addressLabel string, rule domain.AlertRule, address string) {
 	notifConfig, err := s.notifConfigs.GetConfig(ctx, userID)
 	if err != nil {
@@ -183,25 +260,23 @@ func (s *EvaluatorService) sendNotification(ctx context.Context, userID, message
 		return
 	}
 
-	if notifConfig == nil || !notifConfig.NotificationEnabled || notifConfig.DiscordWebhookURL == nil {
+	if notifConfig == nil || !notifConfig.NotificationEnabled {
 		return
 	}
 
-	sent, err := notifications.SendDiscordNotification(
-		*notifConfig.DiscordWebhookURL,
-		message,
-		notifications.AlertMetadata{
-			TxHash:       obs.Hash,
-			AddressLabel: addressLabel,
-			AlertType:    string(rule.Type),
-			Address:      address,
-		},
-	)
+	meta := notifications.AlertMetadata{
+		TxHash:       obs.Hash,
+		AddressLabel: addressLabel,
+		AlertType:    string(rule.Type),
+		Address:      address,
+	}
 
-	if err != nil || !sent {
-		log.Printf("Discord notification failed for user %s: %v", userID, err)
-	} else {
-		log.Printf("Discord notification sent to user %s", userID)
+	for _, n := range s.buildNotifiers(notifConfig) {
+		if err := sendWithRetry(ctx, n, message, meta); err != nil {
+			log.Printf("Notification channel failed for user %s after retries: %v", userID, err)
+		} else {
+			log.Printf("Notification sent to user %s via %T", userID, n)
+		}
 	}
 }
 

frontend/README.md

@@ -5,24 +5,27 @@ React + Vite frontend for the on-chain monitoring and alerting system.
 ## Getting Started
 
 1. Install dependencies:
-   ```bash
-   npm install
-   ```
+
+    ```bash
+    npm install
+    ```
 
 2. Run the development server:
-   ```bash
-   npm run dev
-   ```
+
+    ```bash
+    npm run dev
+    ```
 
 3. Build for production:
-   ```bash
-   npm run build
-   ```
+
+    ```bash
+    npm run build
+    ```
 
 4. Preview production build:
-   ```bash
-   npm run preview
-   ```
+    ```bash
+    npm run preview
+    ```
 
 ## Project Structure
 
@@ -34,5 +37,5 @@ React + Vite frontend for the on-chain monitoring and alerting system.
 
 ## Development
 
-The frontend runs on port 3000 and proxies API requests to the backend running on port 5000.
-
+The frontend runs on port 3000 and proxies API requests to the backend running
+on port 5000.

frontend/package.json

@@ -1,32 +1,36 @@
 {
-  "name": "frontend",
-  "version": "1.0.0",
-  "description": "koin_ping blockchain monoitor UI",
-  "main": "index.js",
-  "scripts": {
-    "dev": "vite",
-    "build": "vite build",
-    "preview": "vite preview"
-  },
-  "keywords": [
-    "cryptocurrency",
-    "blockchain",
-    "blockchain event moitoring"
-  ],
-  "author": "Steven Jannette",
-  "license": "MIT",
-  "type": "module",
-  "dependencies": {
-    "firebase": "^12.7.0",
-    "react": "^19.2.3",
-    "react-dom": "^19.2.3",
-    "react-router-dom": "^7.11.0"
-  },
-  "devDependencies": {
-    "@types/react": "^19.2.7",
-    "@types/react-dom": "^19.2.3",
-    "@vitejs/plugin-react": "^5.1.2",
-    "typescript": "^5.9.3",
-    "vite": "^7.3.0"
-  }
+    "name": "frontend",
+    "version": "1.0.0",
+    "description": "koin_ping blockchain monitor UI",
+    "main": "index.js",
+    "scripts": {
+        "dev": "vite",
+        "build": "vite build",
+        "preview": "vite preview",
+        "test": "vite build",
+        "lint": "prettier --check 'src/**/*.{js,jsx,ts,tsx,css}'",
+        "fmt": "prettier --write 'src/**/*.{js,jsx,ts,tsx,css}'"
+    },
+    "keywords": [
+        "cryptocurrency",
+        "blockchain",
+        "blockchain event monitoring"
+    ],
+    "author": "Steven Jannette",
+    "license": "MIT",
+    "type": "module",
+    "dependencies": {
+        "firebase": "^12.7.0",
+        "react": "^19.2.3",
+        "react-dom": "^19.2.3",
+        "react-router-dom": "^7.11.0"
+    },
+    "devDependencies": {
+        "@types/react": "^19.2.7",
+        "@types/react-dom": "^19.2.3",
+        "@vitejs/plugin-react": "^5.1.2",
+        "prettier": "^3.8.1",
+        "typescript": "^5.9.3",
+        "vite": "^7.3.0"
+    }
 }

frontend/prettierrc

@@ -0,0 +1,4 @@
+{
+    "tabWidth": 4,
+    "proseWrap": "always"
+}

frontend/src/App.jsx

@@ -1,5 +1,6 @@
-import { Routes, Route, Link, Navigate } from "react-router-dom";
+import { Routes, Route, Navigate } from "react-router-dom";
 import { useAuth } from "./contexts/AuthContext";
+import Navbar from "./components/Navbar";
 import Login from "./pages/Login";
 import Signup from "./pages/Signup";
 import Addresses from "./pages/Addresses";
@@ -7,56 +8,28 @@ import Alerts from "./pages/Alerts";
 import AlertHistory from "./pages/AlertHistory";
 
 export default function App() {
-  const { currentUser, logout } = useAuth();
+    const { currentUser } = useAuth();
+
+    if (!currentUser) {
+        return (
+            <Routes>
+                <Route path="/login" element={<Login />} />
+                <Route path="/signup" element={<Signup />} />
+                <Route path="*" element={<Navigate to="/login" />} />
+            </Routes>
+        );
+    }
 
-  // Show login/signup routes if not authenticated
-  if (!currentUser) {
     return (
-      <Routes>
-        <Route path="/login" element={<Login />} />
-        <Route path="/signup" element={<Signup />} />
-        <Route path="*" element={<Navigate to="/login" />} />
-      </Routes>
-    );
-  }
-
-  // Show main app if authenticated
-  return (
-    <div style={{ padding: "1rem" }}>
-      <nav style={{ marginBottom: "1rem", display: "flex", justifyContent: "space-between", alignItems: "center" }}>
         <div>
-          <Link to="/addresses">Addresses</Link>{" | "}
-          <Link to="/alerts">Alerts</Link>{" | "}
-          <Link to="/history">History</Link>
+            <Navbar />
+            <Routes>
+                <Route path="/" element={<Addresses />} />
+                <Route path="/addresses" element={<Addresses />} />
+                <Route path="/alerts" element={<Alerts />} />
+                <Route path="/history" element={<AlertHistory />} />
+                <Route path="*" element={<Navigate to="/addresses" />} />
+            </Routes>
         </div>
-        <div style={{ display: "flex", alignItems: "center", gap: "1rem" }}>
-          <span style={{ fontSize: "0.9rem", color: "#999" }}>
-            {currentUser.email}
-          </span>
-          <button
-            onClick={logout}
-            style={{
-              padding: "0.5rem 1rem",
-              fontSize: "0.9rem",
-              backgroundColor: "#333",
-              color: "white",
-              border: "1px solid #555",
-              borderRadius: "4px",
-              cursor: "pointer"
-            }}
-          >
-            Logout
-          </button>
-        </div>
-      </nav>
-
-      <Routes>
-        <Route path="/" element={<Addresses />} />
-        <Route path="/addresses" element={<Addresses />} />
-        <Route path="/alerts" element={<Alerts />} />
-        <Route path="/history" element={<AlertHistory />} />
-        <Route path="*" element={<Navigate to="/addresses" />} />
-      </Routes>
-    </div>
-  );
+    );
 }

frontend/src/api/addresses.jsx

@@ -1,7 +1,7 @@
 // API client for address management
 
-import { getAuthHeaders, getAuthHeadersSimple } from './authHeaders';
-import { API_BASE } from './config';
+import { getAuthHeaders, getAuthHeadersSimple } from "./authHeaders";
+import { API_BASE } from "./config";
 
 /**
  * Create a new blockchain address to monitor
@@ -11,35 +11,37 @@ import { API_BASE } from './config';
  * @returns {Promise<Object>} Created address with id and metadata
  */
 export async function createAddress(data) {
-  try {
-  const headers = await getAuthHeaders();
-  const response = await fetch(`${API_BASE}/addresses`, {
-    method: 'POST',
-    headers: headers,
-    body: JSON.stringify(data)
-  });
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/addresses`, {
+            method: "POST",
+            headers: headers,
+            body: JSON.stringify(data),
+        });
 
-  if (!response.ok) {
-      // Try to parse error response, but handle if it's not JSON
-      let errorMessage = 'Failed to create address';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        // If JSON parse fails, use status text
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-  }
+        if (!response.ok) {
+            // Try to parse error response, but handle if it's not JSON
+            let errorMessage = "Failed to create address";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                // If JSON parse fails, use status text
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-  return response.json();
-  } catch (error) {
-    // Handle network errors
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        // Handle network errors
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-    throw error;
-  }
 }
 
 /**
@@ -47,33 +49,70 @@ export async function createAddress(data) {
  * @returns {Promise<Array>} List of all addresses
  */
 export async function getAddresses() {
-  try {
-  const headers = await getAuthHeadersSimple();
-  const response = await fetch(`${API_BASE}/addresses`, {
-    headers: headers
-  });
+    try {
+        const headers = await getAuthHeadersSimple();
+        const response = await fetch(`${API_BASE}/addresses`, {
+            headers: headers,
+        });
 
-  if (!response.ok) {
-      // Try to parse error response, but handle if it's not JSON
-      let errorMessage = 'Failed to fetch addresses';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        // If JSON parse fails, use status text
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-  }
+        if (!response.ok) {
+            // Try to parse error response, but handle if it's not JSON
+            let errorMessage = "Failed to fetch addresses";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                // If JSON parse fails, use status text
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-  return response.json();
-  } catch (error) {
-    // Handle network errors or JSON parse errors
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        // Handle network errors or JSON parse errors
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
+    }
+}
+
+/**
+ * Update an address (e.g. change its label)
+ * @param {number} addressId - Address ID to update
+ * @param {Object} data - Fields to update (e.g. { label: "New Label" })
+ * @returns {Promise<Object>} Updated address
+ */
+export async function updateAddress(addressId, data) {
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/addresses/${addressId}`, {
+            method: "PATCH",
+            headers: headers,
+            body: JSON.stringify(data),
+        });
+
+        if (!response.ok) {
+            let errorMessage = "Failed to update address";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
+
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error("Cannot connect to server. Is the backend running?");
+        }
+        throw error;
     }
-    throw error;
-  }
 }
 
 /**
@@ -82,31 +121,32 @@ export async function getAddresses() {
  * @returns {Promise<void>}
  */
 export async function deleteAddress(addressId) {
-  try {
-  const headers = await getAuthHeadersSimple();
-  const response = await fetch(`${API_BASE}/addresses/${addressId}`, {
-    method: 'DELETE',
-    headers: headers
-  });
+    try {
+        const headers = await getAuthHeadersSimple();
+        const response = await fetch(`${API_BASE}/addresses/${addressId}`, {
+            method: "DELETE",
+            headers: headers,
+        });
 
-  if (!response.ok && response.status !== 204) {
-      // Try to parse error response, but handle if it's not JSON
-      let errorMessage = 'Failed to delete address';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        // If JSON parse fails, use status text
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
+        if (!response.ok && response.status !== 204) {
+            // Try to parse error response, but handle if it's not JSON
+            let errorMessage = "Failed to delete address";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                // If JSON parse fails, use status text
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
+    } catch (error) {
+        // Handle network errors
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-  } catch (error) {
-    // Handle network errors
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
-    }
-    throw error;
-  }
 }
-

frontend/src/api/alertEvents.jsx

@@ -1,35 +1,37 @@
 // API client for alert event history
 
-import { getAuthHeadersSimple } from './authHeaders';
-import { API_BASE } from './config';
+import { getAuthHeadersSimple } from "./authHeaders";
+import { API_BASE } from "./config";
 
 /**
  * Get all alert events (history)
  * @returns {Promise<Array>} List of alert events, sorted by most recent first
  */
 export async function getAlertEvents() {
-  try {
-  const headers = await getAuthHeadersSimple();
-  const response = await fetch(`${API_BASE}/alert-events`, {
-    headers: headers
-  });
+    try {
+        const headers = await getAuthHeadersSimple();
+        const response = await fetch(`${API_BASE}/alert-events`, {
+            headers: headers,
+        });
 
-  if (!response.ok) {
-      let errorMessage = 'Failed to fetch alert events';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-  }
+        if (!response.ok) {
+            let errorMessage = "Failed to fetch alert events";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-  return response.json();
-  } catch (error) {
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-    throw error;
-  }
 }

frontend/src/api/alerts.jsx

@@ -1,16 +1,16 @@
 // API client for alert rule management
 
-import { getAuthHeaders, getAuthHeadersSimple } from './authHeaders';
-import { API_BASE } from './config';
+import { getAuthHeaders, getAuthHeadersSimple } from "./authHeaders";
+import { API_BASE } from "./config";
 
 /**
  * Alert types supported by the system
  */
 export const ALERT_TYPES = {
-  INCOMING_TX: 'incoming_tx',
-  OUTGOING_TX: 'outgoing_tx',
-  LARGE_TRANSFER: 'large_transfer',
-  BALANCE_BELOW: 'balance_below'
+    INCOMING_TX: "incoming_tx",
+    OUTGOING_TX: "outgoing_tx",
+    LARGE_TRANSFER: "large_transfer",
+    BALANCE_BELOW: "balance_below",
 };
 
 /**
@@ -22,32 +22,37 @@ export const ALERT_TYPES = {
  * @returns {Promise<Object>} Created alert rule
  */
 export async function createAlert(addressId, data) {
-  try {
-  const headers = await getAuthHeaders();
-  const response = await fetch(`${API_BASE}/addresses/${addressId}/alerts`, {
-    method: 'POST',
-    headers: headers,
-    body: JSON.stringify(data)
-  });
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(
+            `${API_BASE}/addresses/${addressId}/alerts`,
+            {
+                method: "POST",
+                headers: headers,
+                body: JSON.stringify(data),
+            },
+        );
 
-  if (!response.ok) {
-      let errorMessage = 'Failed to create alert rule';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-  }
+        if (!response.ok) {
+            let errorMessage = "Failed to create alert rule";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-  return response.json();
-  } catch (error) {
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-    throw error;
-  }
 }
 
 /**
@@ -56,30 +61,35 @@ export async function createAlert(addressId, data) {
  * @returns {Promise<Array>} List of alert rules
  */
 export async function getAlerts(addressId) {
-  try {
-  const headers = await getAuthHeadersSimple();
-  const response = await fetch(`${API_BASE}/addresses/${addressId}/alerts`, {
-    headers: headers
-  });
+    try {
+        const headers = await getAuthHeadersSimple();
+        const response = await fetch(
+            `${API_BASE}/addresses/${addressId}/alerts`,
+            {
+                headers: headers,
+            },
+        );
 
-  if (!response.ok) {
-      let errorMessage = 'Failed to fetch alert rules';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-  }
+        if (!response.ok) {
+            let errorMessage = "Failed to fetch alert rules";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-  return response.json();
-  } catch (error) {
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-    throw error;
-  }
 }
 
 /**
@@ -89,32 +99,34 @@ export async function getAlerts(addressId) {
  * @returns {Promise<Object>} Updated alert rule
  */
 export async function updateAlertStatus(alertId, enabled) {
-  try {
-  const headers = await getAuthHeaders();
-  const response = await fetch(`${API_BASE}/alerts/${alertId}`, {
-    method: 'PATCH',
-    headers: headers,
-    body: JSON.stringify({ enabled })
-  });
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/alerts/${alertId}`, {
+            method: "PATCH",
+            headers: headers,
+            body: JSON.stringify({ enabled }),
+        });
 
-  if (!response.ok) {
-      let errorMessage = 'Failed to update alert rule';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-  }
+        if (!response.ok) {
+            let errorMessage = "Failed to update alert rule";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-  return response.json();
-  } catch (error) {
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-    throw error;
-  }
 }
 
 /**
@@ -123,27 +135,29 @@ export async function updateAlertStatus(alertId, enabled) {
  * @returns {Promise<void>}
  */
 export async function deleteAlert(alertId) {
-  try {
-  const headers = await getAuthHeadersSimple();
-  const response = await fetch(`${API_BASE}/alerts/${alertId}`, {
-    method: 'DELETE',
-    headers: headers
-  });
+    try {
+        const headers = await getAuthHeadersSimple();
+        const response = await fetch(`${API_BASE}/alerts/${alertId}`, {
+            method: "DELETE",
+            headers: headers,
+        });
 
-  if (!response.ok && response.status !== 204) {
-      let errorMessage = 'Failed to delete alert rule';
-      try {
-    const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
+        if (!response.ok && response.status !== 204) {
+            let errorMessage = "Failed to delete alert rule";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-  } catch (error) {
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
-    }
-    throw error;
-  }
 }

frontend/src/api/authHeaders.js

@@ -5,26 +5,26 @@
  * Includes Firebase ID token in Authorization header
  */
 
-import { auth } from '../firebase/config';
+import { auth } from "../firebase/config";
 
 /**
  * Get headers with authentication token
  * @returns {Promise<Object>} Headers object with Authorization
  */
 export async function getAuthHeaders() {
-  const currentUser = auth.currentUser;
+    const currentUser = auth.currentUser;
 
-  if (!currentUser) {
-    throw new Error('No authenticated user');
-  }
+    if (!currentUser) {
+        throw new Error("No authenticated user");
+    }
 
-  // Get Firebase ID token
-  const token = await currentUser.getIdToken();
+    // Get Firebase ID token
+    const token = await currentUser.getIdToken();
 
-  return {
-    'Content-Type': 'application/json',
-    'Authorization': `Bearer ${token}`
-  };
+    return {
+        "Content-Type": "application/json",
+        Authorization: `Bearer ${token}`,
+    };
 }
 
 /**
@@ -32,16 +32,15 @@ export async function getAuthHeaders() {
  * @returns {Promise<Object>} Headers object with Authorization
  */
 export async function getAuthHeadersSimple() {
-  const currentUser = auth.currentUser;
+    const currentUser = auth.currentUser;
 
-  if (!currentUser) {
-    throw new Error('No authenticated user');
-  }
+    if (!currentUser) {
+        throw new Error("No authenticated user");
+    }
 
-  const token = await currentUser.getIdToken();
+    const token = await currentUser.getIdToken();
 
-  return {
-    'Authorization': `Bearer ${token}`
-  };
+    return {
+        Authorization: `Bearer ${token}`,
+    };
 }
-

frontend/src/api/config.js

@@ -1 +1 @@
-export const API_BASE = import.meta.env.VITE_API_BASE || '/v1';
+export const API_BASE = import.meta.env.VITE_API_BASE || "/v1";

frontend/src/api/notificationConfig.jsx

@@ -1,99 +1,183 @@
-// API client for notification configuration
-
-import { getAuthHeaders } from './authHeaders';
-import { API_BASE } from './config';
+import { getAuthHeaders } from "./authHeaders";
+import { API_BASE } from "./config";
 
 /**
  * Get notification configuration for current user
  * @returns {Promise<Object>} Notification config
  */
 export async function getNotificationConfig() {
-  try {
-    const headers = await getAuthHeaders();
-    const response = await fetch(`${API_BASE}/notification-config`, {
-      headers: headers
-    });
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/notification-config`, {
+            headers: headers,
+        });
 
-    if (!response.ok) {
-      let errorMessage = 'Failed to fetch notification config';
-      try {
-        const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-    }
+        if (!response.ok) {
+            let errorMessage = "Failed to fetch notification config";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-    return response.json();
-  } catch (error) {
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-    throw error;
-  }
 }
 
 /**
  * Update notification configuration
- * @param {Object} config - Configuration to update
- * @param {string} [config.discord_webhook_url] - Discord webhook URL
- * @param {string} [config.telegram_chat_id] - Telegram chat ID
- * @param {string} [config.email] - Email address
- * @param {boolean} [config.notification_enabled] - Enable/disable notifications
+ * @param {Object} config
+ * @param {string} [config.discord_webhook_url]
+ * @param {string} [config.telegram_chat_id]
+ * @param {string} [config.telegram_bot_token]
+ * @param {string} [config.email]
+ * @param {string} [config.slack_webhook_url]
+ * @param {boolean} [config.notification_enabled]
  * @returns {Promise<Object>} Updated config
  */
 export async function updateNotificationConfig(config) {
-  try {
-    const headers = await getAuthHeaders();
-    const response = await fetch(`${API_BASE}/notification-config`, {
-      method: 'PUT',
-      headers: headers,
-      body: JSON.stringify(config)
-    });
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/notification-config`, {
+            method: "PUT",
+            headers: headers,
+            body: JSON.stringify(config),
+        });
 
-    if (!response.ok) {
-      let errorMessage = 'Failed to update notification config';
-      try {
-        const error = await response.json();
-        errorMessage = error.message || errorMessage;
-      } catch {
-        errorMessage = `Server error: ${response.status} ${response.statusText}`;
-      }
-      throw new Error(errorMessage);
-    }
+        if (!response.ok) {
+            let errorMessage = "Failed to update notification config";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-    return response.json();
-  } catch (error) {
-    if (error.message.includes('fetch')) {
-      throw new Error('Cannot connect to server. Is the backend running?');
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
     }
-    throw error;
-  }
 }
 
 /**
- * Test a Discord webhook URL
- * Sends a test message to verify the webhook works
- * @param {string} webhookUrl - Discord webhook URL to test
- * @returns {Promise<boolean>} True if test successful
+ * Set up email notifications via Resend.
+ * Reads the user's saved email from their config and sends a confirmation.
+ * @returns {Promise<Object>} Setup result
  */
-export async function testDiscordWebhook(webhookUrl) {
-  try {
-    const payload = {
-      content: 'Koin Ping test notification - Your Discord webhook is configured correctly!',
-    };
+export async function setupEmail() {
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/email/setup`, {
+            method: "POST",
+            headers: headers,
+        });
 
-    const response = await fetch(webhookUrl, {
-      method: 'POST',
-      headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify(payload)
-    });
+        if (!response.ok) {
+            let errorMessage = "Failed to set up email";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
 
-    return response.ok;
-  } catch (error) {
-    console.error('Discord webhook test failed:', error);
-    return false;
-  }
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
+    }
 }
 
+/**
+ * Send an alert digest email to the user's configured email address.
+ * @returns {Promise<Object>} Digest send result
+ */
+export async function sendEmailDigest() {
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(`${API_BASE}/email/digest`, {
+            method: "POST",
+            headers: headers,
+        });
+
+        if (!response.ok) {
+            let errorMessage = "Failed to send digest";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
+
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
+    }
+}
+
+/**
+ * Test all configured notification channels via the backend
+ * @returns {Promise<Object>} Results per channel
+ */
+export async function testNotificationChannels() {
+    try {
+        const headers = await getAuthHeaders();
+        const response = await fetch(
+            `${API_BASE}/notification-config/test`,
+            {
+                method: "POST",
+                headers: headers,
+            },
+        );
+
+        if (!response.ok) {
+            let errorMessage = "Failed to test notification channels";
+            try {
+                const error = await response.json();
+                errorMessage = error.message || errorMessage;
+            } catch {
+                errorMessage = `Server error: ${response.status} ${response.statusText}`;
+            }
+            throw new Error(errorMessage);
+        }
+
+        return response.json();
+    } catch (error) {
+        if (error.message.includes("fetch")) {
+            throw new Error(
+                "Cannot connect to server. Is the backend running?",
+            );
+        }
+        throw error;
+    }
+}

frontend/src/api/status.jsx

@@ -1,18 +1,18 @@
 // API client for system status
 
-import { API_BASE } from './config';
+import { API_BASE } from "./config";
 
 /**
  * Get system status including latest processed block and health
  * @returns {Promise<Object>} System status
  */
 export async function getSystemStatus() {
-  const response = await fetch(`${API_BASE}/status`);
+    const response = await fetch(`${API_BASE}/status`);
 
-  if (!response.ok) {
-    const error = await response.json();
-    throw new Error(error.message || 'Failed to fetch system status');
-  }
+    if (!response.ok) {
+        const error = await response.json();
+        throw new Error(error.message || "Failed to fetch system status");
+    }
 
-  return response.json();
+    return response.json();
 }

frontend/src/components/AddressForm.jsx

@@ -3,43 +3,43 @@ import Input from "./Input";
 import Button from "./Button";
 
 export default function AddressForm({ onSubmit }) {
-  const [address, setAddress] = useState("");
-  const [label, setLabel] = useState("");
+    const [address, setAddress] = useState("");
+    const [label, setLabel] = useState("");
 
-  const canSubmit = address.trim().length > 0;
+    const canSubmit = address.trim().length > 0;
 
-  function handleSubmit(e) {
-    e.preventDefault();
-    if (!canSubmit) return;
+    function handleSubmit(e) {
+        e.preventDefault();
+        if (!canSubmit) return;
 
-    onSubmit({
-      address: address.trim(),
-      label: label.trim(),
-    });
+        onSubmit({
+            address: address.trim(),
+            label: label.trim(),
+        });
 
-    setAddress("");
-    setLabel("");
-  }
+        setAddress("");
+        setLabel("");
+    }
 
-  return (
-    <form onSubmit={handleSubmit}>
-      <Input
-        label="Blockchain Address"
-        value={address}
-        onChange={setAddress}
-        placeholder="0x..."
-      />
+    return (
+        <form onSubmit={handleSubmit}>
+            <Input
+                label="Blockchain Address"
+                value={address}
+                onChange={setAddress}
+                placeholder="0x..."
+            />
 
-      <Input
-        label="Label (optional)"
-        value={label}
-        onChange={setLabel}
-        placeholder="Treasury, Cold Wallet, etc."
-      />
+            <Input
+                label="Label (optional)"
+                value={label}
+                onChange={setLabel}
+                placeholder="Treasury, Cold Wallet, etc."
+            />
 
-      <Button type="submit" disabled={!canSubmit}>
-        Add Address
-      </Button>
-    </form>
-  );
+            <Button type="submit" disabled={!canSubmit}>
+                Add Address
+            </Button>
+        </form>
+    );
 }

frontend/src/components/AlertForm.jsx

@@ -3,69 +3,69 @@ import Input from "./Input";
 import Button from "./Button";
 
 const ALERT_TYPES = [
-  { value: "incoming_tx", label: "Incoming transaction" },
-  { value: "outgoing_tx", label: "Outgoing transaction" },
-  { value: "large_transfer", label: "Large transfer" },
-  { value: "balance_below", label: "Balance below threshold" },
+    { value: "incoming_tx", label: "Incoming transaction" },
+    { value: "outgoing_tx", label: "Outgoing transaction" },
+    { value: "large_transfer", label: "Large transfer" },
+    { value: "balance_below", label: "Balance below threshold" },
 ];
 
 export default function AlertForm({ onSubmit }) {
-  const [type, setType] = useState("incoming_tx");
-  const [threshold, setThreshold] = useState("");
+    const [type, setType] = useState("incoming_tx");
+    const [threshold, setThreshold] = useState("");
 
-  const needsThreshold =
-    type === "large_transfer" || type === "balance_below";
+    const needsThreshold =
+        type === "large_transfer" || type === "balance_below";
 
-  const canSubmit = needsThreshold
-    ? threshold.trim() !== "" && 
-      !isNaN(Number(threshold)) && 
-      Number(threshold) > 0
-    : true;
+    const canSubmit = needsThreshold
+        ? threshold.trim() !== "" &&
+          !isNaN(Number(threshold)) &&
+          Number(threshold) > 0
+        : true;
 
-  function handleSubmit(e) {
-    e.preventDefault();
-    if (!canSubmit) return;
+    function handleSubmit(e) {
+        e.preventDefault();
+        if (!canSubmit) return;
 
-    onSubmit({
-      type,
-      threshold: needsThreshold ? Number(threshold) : undefined,
-    });
+        onSubmit({
+            type,
+            threshold: needsThreshold ? Number(threshold) : undefined,
+        });
 
-    setThreshold("");
-  }
+        setThreshold("");
+    }
 
-  return (
-    <form onSubmit={handleSubmit}>
-      <div style={{ marginBottom: "1rem" }}>
-        {ALERT_TYPES.map((opt) => (
-          <label key={opt.value} style={{ display: "block" }}>
-            <input
-              type="radio"
-              name="alertType"
-              value={opt.value}
-              checked={type === opt.value}
-              onChange={() => setType(opt.value)}
-            />
-            {" "}{opt.label}
-          </label>
-        ))}
-      </div>
+    return (
+        <form onSubmit={handleSubmit}>
+            <div style={{ marginBottom: "1rem" }}>
+                {ALERT_TYPES.map((opt) => (
+                    <label key={opt.value} style={{ display: "block" }}>
+                        <input
+                            type="radio"
+                            name="alertType"
+                            value={opt.value}
+                            checked={type === opt.value}
+                            onChange={() => setType(opt.value)}
+                        />{" "}
+                        {opt.label}
+                    </label>
+                ))}
+            </div>
 
-      {needsThreshold && (
-        <Input
-          label="Amount (ETH)"
-          type="number"
-          step="0.000001"
-          min="0"
-          value={threshold}
-          onChange={setThreshold}
-          placeholder="e.g. 10"
-        />
-      )}
+            {needsThreshold && (
+                <Input
+                    label="Amount (ETH)"
+                    type="number"
+                    step="0.000001"
+                    min="0"
+                    value={threshold}
+                    onChange={setThreshold}
+                    placeholder="e.g. 10"
+                />
+            )}
 
-      <Button type="submit" disabled={!canSubmit}>
-        Create Alert
-      </Button>
-    </form>
-  );
+            <Button type="submit" disabled={!canSubmit}>
+                Create Alert
+            </Button>
+        </form>
+    );
 }

frontend/src/components/Button.jsx

@@ -3,21 +3,20 @@ export default function Button({
     onClick,
     disabled = false,
     type = "button",
-  }) {
+}) {
     return (
-      <button
-        type={type}
-        onClick={onClick}
-        disabled={disabled}
-        style={{
-          padding: "0.5rem 1rem",
-          fontSize: "1rem",
-          cursor: disabled ? "not-allowed" : "pointer",
-          opacity: disabled ? 0.6 : 1,
-        }}
-      >
-        {children}
-      </button>
+        <button
+            type={type}
+            onClick={onClick}
+            disabled={disabled}
+            style={{
+                padding: "0.5rem 1rem",
+                fontSize: "1rem",
+                cursor: disabled ? "not-allowed" : "pointer",
+                opacity: disabled ? 0.6 : 1,
+            }}
+        >
+            {children}
+        </button>
     );
-  }
-  
+}

frontend/src/components/Input.jsx

@@ -7,27 +7,26 @@ export default function Input({
     step,
     min,
     disabled = false,
-  }) {
+}) {
     return (
-      <label style={{ display: "block", marginBottom: "1rem" }}>
-        <div style={{ marginBottom: "0.25rem", fontSize: "0.9rem" }}>
-          {label}
-        </div>
-        <input
-          type={type}
-          value={value}
-          placeholder={placeholder}
-          step={step}
-          min={min}
-          disabled={disabled}
-          onChange={(e) => onChange(e.target.value)}
-          style={{
-            width: "100%",
-            padding: "0.5rem",
-            fontSize: "1rem",
-          }}
-        />
-      </label>
+        <label style={{ display: "block", marginBottom: "1rem" }}>
+            <div style={{ marginBottom: "0.25rem", fontSize: "0.9rem" }}>
+                {label}
+            </div>
+            <input
+                type={type}
+                value={value}
+                placeholder={placeholder}
+                step={step}
+                min={min}
+                disabled={disabled}
+                onChange={(e) => onChange(e.target.value)}
+                style={{
+                    width: "100%",
+                    padding: "0.5rem",
+                    fontSize: "1rem",
+                }}
+            />
+        </label>
     );
-  }
-  
+}

frontend/src/components/Navbar.jsx

@@ -0,0 +1,85 @@
+import { Link, useLocation } from "react-router-dom";
+import { useAuth } from "../contexts/AuthContext";
+
+const navLinks = [
+  { to: "/addresses", label: "Addresses" },
+  { to: "/alerts", label: "Configure Alerts" },
+  { to: "/history", label: "Alert History" },
+];
+
+export default function Navbar() {
+  const { currentUser, logout } = useAuth();
+  const location = useLocation();
+
+  if (!currentUser) return null;
+
+  return (
+    <nav style={{
+      display: "flex",
+      justifyContent: "space-between",
+      alignItems: "center",
+      padding: "1rem 2rem",
+      marginBottom: "1.5rem",
+      backgroundColor: "#1a1a1a",
+      borderBottom: "1px solid #333",
+    }}>
+      <div style={{ display: "flex", alignItems: "center", gap: "0.5rem" }}>
+        <span style={{
+          fontWeight: 700,
+          fontSize: "1.1rem",
+          color: "#fff",
+          marginRight: "2rem",
+          letterSpacing: "0.5px",
+        }}>
+          Koin Ping
+        </span>
+
+        <div style={{ display: "flex", gap: "0.25rem" }}>
+          {navLinks.map(({ to, label }) => {
+            const isActive = location.pathname === to;
+            return (
+              <Link
+                key={to}
+                to={to}
+                style={{
+                  padding: "0.5rem 1.25rem",
+                  borderRadius: "6px",
+                  textDecoration: "none",
+                  fontSize: "1.425rem",
+                  fontWeight: isActive ? 600 : 200,
+                  color: isActive ? "#fff" : "#999",
+                  backgroundColor: isActive ? "#333" : "transparent",
+                  transition: "all 0.15s ease",
+                }}
+              >
+                {label}
+              </Link>
+            );
+          })}
+        </div>
+      </div>
+
+      <div style={{ display: "flex", alignItems: "center", gap: "1.25rem" }}>
+        <span style={{ fontSize: "1.275rem", color: "#777" }}>
+          {currentUser.email}
+        </span>
+        <button
+          onClick={logout}
+          style={{
+            padding: "0.4rem 1rem",
+            fontSize: "1.275rem",
+            fontWeight: 400,
+            backgroundColor: "transparent",
+            color: "#999",
+            border: "1px solid #444",
+            borderRadius: "6px",
+            cursor: "pointer",
+            transition: "all 0.15s ease",
+          }}
+        >
+          Logout
+        </button>
+      </div>
+    </nav>
+  );
+}

frontend/src/contexts/AuthContext.jsx

@@ -4,14 +4,14 @@
  * Provides authentication state and methods throughout the app
  */
 
-import { createContext, useContext, useEffect, useState } from 'react';
+import { createContext, useContext, useEffect, useState } from "react";
 import {
-  createUserWithEmailAndPassword,
-  signInWithEmailAndPassword,
-  signOut,
-  onAuthStateChanged
-} from 'firebase/auth';
-import { auth } from '../firebase/config';
+    createUserWithEmailAndPassword,
+    signInWithEmailAndPassword,
+    signOut,
+    onAuthStateChanged,
+} from "firebase/auth";
+import { auth } from "../firebase/config";
 
 const AuthContext = createContext();
 
@@ -20,88 +20,95 @@ const AuthContext = createContext();
  * @returns {Object} Auth context value
  */
 export function useAuth() {
-  const context = useContext(AuthContext);
-  if (!context) {
-    throw new Error('useAuth must be used within AuthProvider');
-  }
-  return context;
+    const context = useContext(AuthContext);
+    if (!context) {
+        throw new Error("useAuth must be used within AuthProvider");
+    }
+    return context;
 }
 
 /**
  * AuthProvider - Wraps app and provides auth state
  */
 export function AuthProvider({ children }) {
-  const [currentUser, setCurrentUser] = useState(null);
-  const [loading, setLoading] = useState(true);
-  const [error, setError] = useState(null);
+    const [currentUser, setCurrentUser] = useState(null);
+    const [loading, setLoading] = useState(true);
+    const [error, setError] = useState(null);
 
-  /**
-   * Sign up with email and password
-   */
-  async function signup(email, password) {
-    try {
-      setError(null);
-      const result = await createUserWithEmailAndPassword(auth, email, password);
-      return result.user;
-    } catch (err) {
-      setError(err.message);
-      throw err;
+    /**
+     * Sign up with email and password
+     */
+    async function signup(email, password) {
+        try {
+            setError(null);
+            const result = await createUserWithEmailAndPassword(
+                auth,
+                email,
+                password,
+            );
+            return result.user;
+        } catch (err) {
+            setError(err.message);
+            throw err;
+        }
     }
-  }
 
-  /**
-   * Log in with email and password
-   */
-  async function login(email, password) {
-    try {
-      setError(null);
-      const result = await signInWithEmailAndPassword(auth, email, password);
-      return result.user;
-    } catch (err) {
-      setError(err.message);
-      throw err;
+    /**
+     * Log in with email and password
+     */
+    async function login(email, password) {
+        try {
+            setError(null);
+            const result = await signInWithEmailAndPassword(
+                auth,
+                email,
+                password,
+            );
+            return result.user;
+        } catch (err) {
+            setError(err.message);
+            throw err;
+        }
     }
-  }
 
-  /**
-   * Log out current user
-   */
-  async function logout() {
-    try {
-      setError(null);
-      await signOut(auth);
-    } catch (err) {
-      setError(err.message);
-      throw err;
+    /**
+     * Log out current user
+     */
+    async function logout() {
+        try {
+            setError(null);
+            await signOut(auth);
+        } catch (err) {
+            setError(err.message);
+            throw err;
+        }
     }
-  }
 
-  /**
-   * Listen for auth state changes
-   */
-  useEffect(() => {
-    const unsubscribe = onAuthStateChanged(auth, (user) => {
-      setCurrentUser(user);
-      setLoading(false);
-    });
+    /**
+     * Listen for auth state changes
+     */
+    useEffect(() => {
+        const unsubscribe = onAuthStateChanged(auth, (user) => {
+            setCurrentUser(user);
+            setLoading(false);
+        });
 
-    // Cleanup subscription
-    return unsubscribe;
-  }, []);
+        // Cleanup subscription
+        return unsubscribe;
+    }, []);
 
-  const value = {
-    currentUser,
-    signup,
-    login,
-    logout,
-    error,
-    loading
-  };
+    const value = {
+        currentUser,
+        signup,
+        login,
+        logout,
+        error,
+        loading,
+    };
 
-  return (
-    <AuthContext.Provider value={value}>
-      {!loading && children}
-    </AuthContext.Provider>
-  );
+    return (
+        <AuthContext.Provider value={value}>
+            {!loading && children}
+        </AuthContext.Provider>
+    );
 }
-

frontend/src/firebase/config.js

@@ -1,6 +1,5 @@
-
-import { initializeApp } from 'firebase/app';
-import { getAuth } from 'firebase/auth';
+import { initializeApp } from "firebase/app";
+import { getAuth } from "firebase/auth";
 import {
     firebaseApiKey,
     firebaseAuthDomain,
@@ -8,9 +7,8 @@ import {
     firebaseStorageBucket,
     firebaseMessagingSenderId,
     firebaseAppId,
-    firebaseMeasurementId
-} from '../secrets.js';
-
+    firebaseMeasurementId,
+} from "../secrets.js";
 
 const firebaseConfig = {
     apiKey: firebaseApiKey,
@@ -19,12 +17,11 @@ const firebaseConfig = {
     storageBucket: firebaseStorageBucket,
     messagingSenderId: firebaseMessagingSenderId,
     appId: firebaseAppId,
-    measurementId: firebaseMeasurementId
-  };
+    measurementId: firebaseMeasurementId,
+};
 
 const app = initializeApp(firebaseConfig);
 
 export const auth = getAuth(app);
 
 export default app;
-

frontend/src/index.css

@@ -0,0 +1,33 @@
+@import url('https://fonts.googleapis.com/css2?family=Nunito:ital,wght@0,200..1000;1,200..1000&display=swap');
+
+*,
+*::before,
+*::after {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+html {
+  font-size: 14px;
+}
+
+body {
+  font-family: 'Nunito', sans-serif;
+  font-size: 1.5rem;
+  font-weight: 200;
+  line-height: 1.6;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+h1, h2, h3, h4, h5, h6 {
+  font-family: 'Nunito', sans-serif;
+  font-weight: 200;
+}
+
+input, select, textarea, button {
+  font-family: 'Nunito', sans-serif;
+  font-size: 1rem;
+  font-weight: 200;
+}

frontend/src/main.jsx

@@ -3,13 +3,14 @@ import ReactDOM from "react-dom/client";
 import { BrowserRouter } from "react-router-dom";
 import { AuthProvider } from "./contexts/AuthContext";
 import App from "./App";
+import "./index.css";
 
 ReactDOM.createRoot(document.getElementById("root")).render(
-  <React.StrictMode>
-    <BrowserRouter>
-      <AuthProvider>
-        <App />
-      </AuthProvider>
-    </BrowserRouter>
-  </React.StrictMode>
+    <React.StrictMode>
+        <BrowserRouter>
+            <AuthProvider>
+                <App />
+            </AuthProvider>
+        </BrowserRouter>
+    </React.StrictMode>,
 );

frontend/src/pages/Addresses.jsx

@@ -1,83 +1,200 @@
 import { useState, useEffect } from "react";
 import AddressForm from "../components/AddressForm";
-import { getAddresses, createAddress } from "../api/addresses";
+import { getAddresses, createAddress, deleteAddress, updateAddress } from "../api/addresses";
 
 export default function Addresses() {
-  const [addresses, setAddresses] = useState([]);
-  const [loading, setLoading] = useState(true);
-  const [error, setError] = useState(null);
+    const [addresses, setAddresses] = useState([]);
+    const [loading, setLoading] = useState(true);
+    const [error, setError] = useState(null);
+    const [editingId, setEditingId] = useState(null);
+    const [editLabel, setEditLabel] = useState("");
 
-  // Load addresses on mount
-  useEffect(() => {
-    async function fetchAddresses() {
-      try {
-        setLoading(true);
-        const data = await getAddresses();
-        setAddresses(data);
-      } catch (err) {
-        setError(err.message);
-        console.error("Failed to fetch addresses:", err);
-      } finally {
-        setLoading(false);
-      }
+    // Load addresses on mount
+    useEffect(() => {
+        async function fetchAddresses() {
+            try {
+                setLoading(true);
+                const data = await getAddresses();
+                setAddresses(data);
+            } catch (err) {
+                setError(err.message);
+                console.error("Failed to fetch addresses:", err);
+            } finally {
+                setLoading(false);
+            }
+        }
+
+        fetchAddresses();
+    }, []);
+
+    // Handle new address submission
+    async function handleAddressSubmit(data) {
+        try {
+            const newAddress = await createAddress(data);
+            setAddresses((prev) => [...prev, newAddress]);
+            setError(null);
+        } catch (err) {
+            setError(err.message);
+            console.error("Failed to create address:", err);
+        }
     }
 
-    fetchAddresses();
-  }, []);
-
-  // Handle new address submission
-  async function handleAddressSubmit(data) {
-    try {
-      const newAddress = await createAddress(data);
-      // Append new address to state
-      setAddresses((prev) => [...prev, newAddress]);
-      setError(null); // Clear any previous errors
-    } catch (err) {
-      setError(err.message);
-      console.error("Failed to create address:", err);
+    async function handleDelete(id, label) {
+        const displayName = label || "this address";
+        if (!window.confirm(`Remove "${displayName}"? This will also delete all associated alert rules.`)) {
+            return;
+        }
+        try {
+            await deleteAddress(id);
+            setAddresses((prev) => prev.filter((a) => a.id !== id));
+            setError(null);
+        } catch (err) {
+            setError(err.message);
+            console.error("Failed to delete address:", err);
+        }
     }
-  }
 
-  return (
-    <div style={{ maxWidth: "800px", margin: "0 auto", padding: "2rem" }}>
-      <h1>Tracked Addresses</h1>
+    function handleEditStart(addr) {
+        setEditingId(addr.id);
+        setEditLabel(addr.label ?? "");
+    }
 
-      <div style={{ marginBottom: "2rem" }}>
-        <AddressForm onSubmit={handleAddressSubmit} />
-      </div>
+    async function handleEditSave(id) {
+        try {
+            const updated = await updateAddress(id, { label: editLabel || null });
+            setAddresses((prev) => prev.map((a) => (a.id === id ? updated : a)));
+            setEditingId(null);
+            setEditLabel("");
+            setError(null);
+        } catch (err) {
+            setError(err.message);
+            console.error("Failed to update address:", err);
+        }
+    }
 
-      <div>
-        <h2>Existing Addresses</h2>
-        {loading && <p>Loading addresses...</p>}
-        {error && <p style={{ color: "red" }}>Error: {error}</p>}
-        {!loading && !error && addresses.length === 0 && (
-          <p style={{ color: "#666" }}>
-            No addresses tracked yet. Add one above to get started.
-          </p>
-        )}
-        {addresses.length > 0 && (
-          <ul style={{ listStyle: "none", padding: 0 }}>
-            {addresses.map((addr, index) => (
-              <li
-                key={addr.id || index}
-                style={{
-                  padding: "1rem",
-                  marginBottom: "0.5rem",
-                  border: "1px solid #ddd",
-                  borderRadius: "4px",
-                }}
-              >
-                <div style={{ fontWeight: "bold", marginBottom: "0.25rem" }}>
-                  {addr.label || "Unlabeled"}
-                </div>
-                <div style={{ fontFamily: "monospace", fontSize: "0.9rem" }}>
-                  {addr.address}
-                </div>
-              </li>
-            ))}
-          </ul>
-        )}
-      </div>
-    </div>
-  );
+    function handleEditCancel() {
+        setEditingId(null);
+        setEditLabel("");
+    }
+
+    return (
+        <div style={{ maxWidth: "800px", margin: "0 auto", padding: "2rem" }}>
+            <h1>Tracked Addresses</h1>
+
+            <div style={{ marginBottom: "2rem" }}>
+                <AddressForm onSubmit={handleAddressSubmit} />
+            </div>
+
+            <div>
+                <h2>Existing Addresses</h2>
+                {loading && <p>Loading addresses...</p>}
+                {error && <p style={{ color: "red" }}>Error: {error}</p>}
+                {!loading && !error && addresses.length === 0 && (
+                    <p style={{ color: "#808080" }}>
+                        No addresses tracked yet. Add one above to get started.
+                    </p>
+                )}
+                {addresses.length > 0 && (
+                    <ul style={{ listStyle: "none", padding: 0 }}>
+                        {addresses.map((addr, index) => (
+                            <li
+                                key={addr.id || index}
+                                style={{
+                                    padding: "1rem",
+                                    marginBottom: "0.5rem",
+                                    border: "1px solid #444",
+                                    borderRadius: "4px",
+                                    backgroundColor: "#333",
+                                }}
+                            >
+                                <div style={{ display: "flex", justifyContent: "space-between", alignItems: "center" }}>
+                                    <div style={{ flex: 1 }}>
+                                        {editingId === addr.id ? (
+                                            <div style={{ display: "flex", gap: "0.5rem", alignItems: "center", marginBottom: "0.25rem" }}>
+                                                <input
+                                                    value={editLabel}
+                                                    onChange={(e) => setEditLabel(e.target.value)}
+                                                    placeholder="Label (optional)"
+                                                    style={{
+                                                        background: "#444",
+                                                        border: "1px solid #666",
+                                                        borderRadius: "3px",
+                                                        color: "#fff",
+                                                        padding: "0.25rem 0.5rem",
+                                                        fontSize: "0.9rem",
+                                                    }}
+                                                    onKeyDown={(e) => {
+                                                        if (e.key === "Enter") handleEditSave(addr.id);
+                                                        if (e.key === "Escape") handleEditCancel();
+                                                    }}
+                                                    autoFocus
+                                                />
+                                                <button
+                                                    onClick={() => handleEditSave(addr.id)}
+                                                    style={{ cursor: "pointer", padding: "0.25rem 0.6rem", fontSize: "0.85rem" }}
+                                                >
+                                                    Save
+                                                </button>
+                                                <button
+                                                    onClick={handleEditCancel}
+                                                    style={{ cursor: "pointer", padding: "0.25rem 0.6rem", fontSize: "0.85rem", background: "transparent", color: "#aaa", border: "1px solid #555" }}
+                                                >
+                                                    Cancel
+                                                </button>
+                                            </div>
+                                        ) : (
+                                            <div style={{ display: "flex", alignItems: "center", gap: "0.5rem", marginBottom: "0.25rem" }}>
+                                                <span style={{ fontWeight: "bold" }}>
+                                                    {addr.label || "Unlabeled"}
+                                                </span>
+                                                <button
+                                                    onClick={() => handleEditStart(addr)}
+                                                    style={{
+                                                        cursor: "pointer",
+                                                        background: "transparent",
+                                                        border: "none",
+                                                        color: "#6699cc",
+                                                        fontSize: "0.8rem",
+                                                        padding: "0",
+                                                        textDecoration: "underline",
+                                                    }}
+                                                >
+                                                    Edit
+                                                </button>
+                                            </div>
+                                        )}
+                                        <div
+                                            style={{
+                                                fontFamily: "monospace",
+                                                fontSize: "1.035rem",
+                                                color: "#b3b3b3",
+                                            }}
+                                        >
+                                            {addr.address}
+                                        </div>
+                                    </div>
+                                    <button
+                                        onClick={() => handleDelete(addr.id, addr.label)}
+                                        style={{
+                                            cursor: "pointer",
+                                            background: "transparent",
+                                            border: "1px solid #884444",
+                                            color: "#cc6666",
+                                            borderRadius: "3px",
+                                            padding: "0.3rem 0.7rem",
+                                            fontSize: "0.85rem",
+                                            marginLeft: "1rem",
+                                            flexShrink: 0,
+                                        }}
+                                    >
+                                        Remove
+                                    </button>
+                                </div>
+                            </li>
+                        ))}
+                    </ul>
+                )}
+            </div>
+        </div>
+    );
 }

frontend/src/pages/AlertHistory.jsx

@@ -2,73 +2,84 @@ import { useState, useEffect } from "react";
 import { getAlertEvents } from "../api/alertEvents";
 
 export default function AlertHistory() {
-  const [alertEvents, setAlertEvents] = useState([]);
-  const [loading, setLoading] = useState(true);
-  const [error, setError] = useState(null);
+    const [alertEvents, setAlertEvents] = useState([]);
+    const [loading, setLoading] = useState(true);
+    const [error, setError] = useState(null);
 
-  // Fetch alert events on mount
-  useEffect(() => {
-    async function fetchAlertEvents() {
-      try {
-        setLoading(true);
-        const data = await getAlertEvents();
-        setAlertEvents(data);
-      } catch (err) {
-        setError(err.message);
-        console.error("Failed to fetch alert events:", err);
-      } finally {
-        setLoading(false);
-      }
+    // Fetch alert events on mount
+    useEffect(() => {
+        async function fetchAlertEvents() {
+            try {
+                setLoading(true);
+                const data = await getAlertEvents();
+                setAlertEvents(data);
+            } catch (err) {
+                setError(err.message);
+                console.error("Failed to fetch alert events:", err);
+            } finally {
+                setLoading(false);
+            }
+        }
+
+        fetchAlertEvents();
+    }, []);
+
+    if (loading) {
+        return <div style={{ padding: "2rem" }}>Loading...</div>;
     }
 
-    fetchAlertEvents();
-  }, []);
+    if (error) {
+        return (
+            <div style={{ padding: "2rem", color: "red" }}>Error: {error}</div>
+        );
+    }
 
-  if (loading) {
-    return <div style={{ padding: "2rem" }}>Loading...</div>;
-  }
+    return (
+        <div style={{ maxWidth: "800px", margin: "0 auto", padding: "2rem" }}>
+            <h1>Recent Alerts</h1>
 
-  if (error) {
-    return <div style={{ padding: "2rem", color: "red" }}>Error: {error}</div>;
-  }
-
-  return (
-    <div style={{ maxWidth: "800px", margin: "0 auto", padding: "2rem" }}>
-      <h1>Recent Alerts</h1>
-
-      {alertEvents.length === 0 ? (
-        <p style={{ color: "#666" }}>No alerts yet</p>
-      ) : (
-        <ul style={{ listStyle: "none", padding: 0 }}>
-          {alertEvents.map((event) => (
-            <li
-              key={event.id}
-              style={{
-                padding: "1rem",
-                marginBottom: "0.75rem",
-                border: "1px solid #ddd",
-                borderRadius: "4px",
-              }}
-            >
-              <div style={{ marginBottom: "0.5rem" }}>{event.message}</div>
-              {event.address_label && (
-                <div style={{ fontSize: "0.9rem", color: "#666", marginBottom: "0.25rem" }}>
-                  Address: {event.address_label}
-                </div>
-              )}
-              <small style={{ color: "#999" }}>
-                {formatTimestamp(event.timestamp)}
-              </small>
-            </li>
-          ))}
-        </ul>
-      )}
-    </div>
-  );
+            {alertEvents.length === 0 ? (
+                <p style={{ color: "#808080" }}>No alerts yet</p>
+            ) : (
+                <ul style={{ listStyle: "none", padding: 0 }}>
+                    {alertEvents.map((event) => (
+                        <li
+                            key={event.id}
+                            style={{
+                                padding: "1rem",
+                                marginBottom: "0.75rem",
+                                border: "1px solid #444",
+                                borderRadius: "4px",
+                                backgroundColor: "#333",
+                            }}
+                        >
+                            <div style={{ marginBottom: "0.5rem" }}>
+                                {event.message}
+                            </div>
+                            {event.address_label && (
+                                <div
+                                    style={{
+                                    fontSize: "1.035rem",
+                                    color: "#808080",
+                                        marginBottom: "0.25rem",
+                                    }}
+                                >
+                                    Address: {event.address_label}
+                                </div>
+                            )}
+                            <small style={{ color: "#b3b3b3" }}>
+                                {formatTimestamp(event.timestamp)}
+                            </small>
+                        </li>
+                    ))}
+                </ul>
+            )}
+        </div>
+    );
 }
 
 // Helper to format timestamp for display
 function formatTimestamp(timestamp) {
-  const date = new Date(timestamp);
-  return date.toLocaleString();
+    const date = new Date(timestamp);
+    return date.toLocaleString();
 }

frontend/src/pages/Login.jsx

@@ -4,140 +4,143 @@
  * Allows existing users to sign in with email and password
  */
 
-import { useState } from 'react';
-import { Link, useNavigate } from 'react-router-dom';
-import { useAuth } from '../contexts/AuthContext';
+import { useState } from "react";
+import { Link, useNavigate } from "react-router-dom";
+import { useAuth } from "../contexts/AuthContext";
 
 export default function Login() {
-  const [email, setEmail] = useState('');
-  const [password, setPassword] = useState('');
-  const [error, setError] = useState('');
-  const [loading, setLoading] = useState(false);
+    const [email, setEmail] = useState("");
+    const [password, setPassword] = useState("");
+    const [error, setError] = useState("");
+    const [loading, setLoading] = useState(false);
 
-  const { login } = useAuth();
-  const navigate = useNavigate();
+    const { login } = useAuth();
+    const navigate = useNavigate();
 
-  async function handleSubmit(e) {
-    e.preventDefault();
+    async function handleSubmit(e) {
+        e.preventDefault();
 
-    // Validation
-    if (!email || !password) {
-      setError('Please fill in all fields');
-      return;
+        // Validation
+        if (!email || !password) {
+            setError("Please fill in all fields");
+            return;
+        }
+
+        try {
+            setError("");
+            setLoading(true);
+            await login(email, password);
+            navigate("/addresses"); // Redirect to main app
+        } catch (err) {
+            setError("Failed to log in: " + err.message);
+        } finally {
+            setLoading(false);
+        }
     }
 
-    try {
-      setError('');
-      setLoading(true);
-      await login(email, password);
-      navigate('/addresses'); // Redirect to main app
-    } catch (err) {
-      setError('Failed to log in: ' + err.message);
-    } finally {
-      setLoading(false);
-    }
-  }
-
-  return (
-    <div style={{ 
-      maxWidth: '400px', 
-      margin: '4rem auto', 
-      padding: '2rem',
-      border: '1px solid #333',
-      borderRadius: '8px'
-    }}>
-      <h1 style={{ marginBottom: '2rem', textAlign: 'center' }}>
-        Koin Ping - Login
-      </h1>
-
-      {error && (
-        <div style={{ 
-          padding: '0.75rem', 
-          marginBottom: '1rem', 
-          backgroundColor: '#ff000020',
-          border: '1px solid #ff0000',
-          borderRadius: '4px',
-          color: '#ff6666'
-        }}>
-          {error}
-        </div>
-      )}
-
-      <form onSubmit={handleSubmit}>
-        <div style={{ marginBottom: '1rem' }}>
-          <label style={{ display: 'block', marginBottom: '0.5rem' }}>
-            Email
-          </label>
-          <input
-            type="email"
-            value={email}
-            onChange={(e) => setEmail(e.target.value)}
-            disabled={loading}
+    return (
+        <div
             style={{
-              width: '100%',
-              padding: '0.5rem',
-              fontSize: '1rem',
-              backgroundColor: '#1a1a1a',
-              border: '1px solid #444',
-              borderRadius: '4px',
-              color: 'white'
+                maxWidth: "400px",
+                margin: "4rem auto",
+                padding: "2rem",
+                border: "1px solid #333",
+                borderRadius: "8px",
             }}
-            required
-          />
-        </div>
-
-        <div style={{ marginBottom: '1.5rem' }}>
-          <label style={{ display: 'block', marginBottom: '0.5rem' }}>
-            Password
-          </label>
-          <input
-            type="password"
-            value={password}
-            onChange={(e) => setPassword(e.target.value)}
-            disabled={loading}
-            style={{
-              width: '100%',
-              padding: '0.5rem',
-              fontSize: '1rem',
-              backgroundColor: '#1a1a1a',
-              border: '1px solid #444',
-              borderRadius: '4px',
-              color: 'white'
-            }}
-            required
-          />
-        </div>
-
-        <button
-          type="submit"
-          disabled={loading}
-          style={{
-            width: '100%',
-            padding: '0.75rem',
-            fontSize: '1rem',
-            backgroundColor: loading ? '#333' : '#0066cc',
-            color: 'white',
-            border: 'none',
-            borderRadius: '4px',
-            cursor: loading ? 'not-allowed' : 'pointer'
-          }}
         >
-          {loading ? 'Logging in...' : 'Log In'}
-        </button>
-      </form>
+            <h1 style={{ marginBottom: "2rem", textAlign: "center" }}>
+                Koin Ping - Login
+            </h1>
 
-      <div style={{ marginTop: '1.5rem', textAlign: 'center' }}>
-        <p style={{ color: '#999' }}>
-          Don't have an account?{' '}
-          <Link 
-            to="/signup" 
-            style={{ color: '#0066cc', textDecoration: 'none' }}
-          >
-            Sign up here
-          </Link>
-        </p>
-      </div>
-    </div>
-  );
+            {error && (
+                <div
+                    style={{
+                        padding: "0.75rem",
+                        marginBottom: "1rem",
+                        backgroundColor: "#ff000020",
+                        border: "1px solid #ff0000",
+                        borderRadius: "4px",
+                        color: "#ff6666",
+                    }}
+                >
+                    {error}
+                </div>
+            )}
+
+            <form onSubmit={handleSubmit}>
+                <div style={{ marginBottom: "1rem" }}>
+                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
+                        Email
+                    </label>
+                    <input
+                        type="email"
+                        value={email}
+                        onChange={(e) => setEmail(e.target.value)}
+                        disabled={loading}
+                        style={{
+                            width: "100%",
+                            padding: "0.5rem",
+                            fontSize: "1rem",
+                            backgroundColor: "#242424",
+                            border: "1px solid #444",
+                            borderRadius: "4px",
+                            color: "white",
+                        }}
+                        required
+                    />
+                </div>
+
+                <div style={{ marginBottom: "1.5rem" }}>
+                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
+                        Password
+                    </label>
+                    <input
+                        type="password"
+                        value={password}
+                        onChange={(e) => setPassword(e.target.value)}
+                        disabled={loading}
+                        style={{
+                            width: "100%",
+                            padding: "0.5rem",
+                            fontSize: "1rem",
+                            backgroundColor: "#242424",
+                            border: "1px solid #444",
+                            borderRadius: "4px",
+                            color: "white",
+                        }}
+                        required
+                    />
+                </div>
+
+                <button
+                    type="submit"
+                    disabled={loading}
+                    style={{
+                        width: "100%",
+                        padding: "0.75rem",
+                        fontSize: "1rem",
+                        backgroundColor: loading ? "#333" : "#0066cc",
+                        color: "white",
+                        border: "none",
+                        borderRadius: "4px",
+                        cursor: loading ? "not-allowed" : "pointer",
+                    }}
+                >
+                    {loading ? "Logging in..." : "Log In"}
+                </button>
+            </form>
+
+            <div style={{ marginTop: "1.5rem", textAlign: "center" }}>
+                <p style={{ color: "#b3b3b3" }}>
+                    Don't have an account?{" "}
+                    <Link
+                        to="/signup"
+                        style={{ color: "#0066cc", textDecoration: "none" }}
+                    >
+                        Sign up here
+                    </Link>
+                </p>
+            </div>
+        </div>
+    );
 }
-

frontend/src/pages/Signup.jsx

@@ -4,182 +4,185 @@
  * Allows new users to create an account with email and password
  */
 
-import { useState } from 'react';
-import { Link, useNavigate } from 'react-router-dom';
-import { useAuth } from '../contexts/AuthContext';
+import { useState } from "react";
+import { Link, useNavigate } from "react-router-dom";
+import { useAuth } from "../contexts/AuthContext";
 
 export default function Signup() {
-  const [email, setEmail] = useState('');
-  const [password, setPassword] = useState('');
-  const [confirmPassword, setConfirmPassword] = useState('');
-  const [error, setError] = useState('');
-  const [loading, setLoading] = useState(false);
+    const [email, setEmail] = useState("");
+    const [password, setPassword] = useState("");
+    const [confirmPassword, setConfirmPassword] = useState("");
+    const [error, setError] = useState("");
+    const [loading, setLoading] = useState(false);
 
-  const { signup } = useAuth();
-  const navigate = useNavigate();
+    const { signup } = useAuth();
+    const navigate = useNavigate();
 
-  async function handleSubmit(e) {
-    e.preventDefault();
+    async function handleSubmit(e) {
+        e.preventDefault();
 
-    // Validation
-    if (!email || !password || !confirmPassword) {
-      setError('Please fill in all fields');
-      return;
+        // Validation
+        if (!email || !password || !confirmPassword) {
+            setError("Please fill in all fields");
+            return;
+        }
+
+        if (password !== confirmPassword) {
+            setError("Passwords do not match");
+            return;
+        }
+
+        if (password.length < 6) {
+            setError("Password must be at least 6 characters");
+            return;
+        }
+
+        try {
+            setError("");
+            setLoading(true);
+            await signup(email, password);
+            navigate("/addresses"); // Auto-login and redirect
+        } catch (err) {
+            // Firebase-specific error messages
+            if (err.code === "auth/email-already-in-use") {
+                setError("Email already in use. Try logging in instead.");
+            } else if (err.code === "auth/invalid-email") {
+                setError("Invalid email address");
+            } else if (err.code === "auth/weak-password") {
+                setError("Password is too weak");
+            } else {
+                setError("Failed to create account: " + err.message);
+            }
+        } finally {
+            setLoading(false);
+        }
     }
 
-    if (password !== confirmPassword) {
-      setError('Passwords do not match');
-      return;
-    }
-
-    if (password.length < 6) {
-      setError('Password must be at least 6 characters');
-      return;
-    }
-
-    try {
-      setError('');
-      setLoading(true);
-      await signup(email, password);
-      navigate('/addresses'); // Auto-login and redirect
-    } catch (err) {
-      // Firebase-specific error messages
-      if (err.code === 'auth/email-already-in-use') {
-        setError('Email already in use. Try logging in instead.');
-      } else if (err.code === 'auth/invalid-email') {
-        setError('Invalid email address');
-      } else if (err.code === 'auth/weak-password') {
-        setError('Password is too weak');
-      } else {
-        setError('Failed to create account: ' + err.message);
-      }
-    } finally {
-      setLoading(false);
-    }
-  }
-
-  return (
-    <div style={{ 
-      maxWidth: '400px', 
-      margin: '4rem auto', 
-      padding: '2rem',
-      border: '1px solid #333',
-      borderRadius: '8px'
-    }}>
-      <h1 style={{ marginBottom: '2rem', textAlign: 'center' }}>
-        Koin Ping - Sign Up
-      </h1>
-
-      {error && (
-        <div style={{ 
-          padding: '0.75rem', 
-          marginBottom: '1rem', 
-          backgroundColor: '#ff000020',
-          border: '1px solid #ff0000',
-          borderRadius: '4px',
-          color: '#ff6666'
-        }}>
-          {error}
-        </div>
-      )}
-
-      <form onSubmit={handleSubmit}>
-        <div style={{ marginBottom: '1rem' }}>
-          <label style={{ display: 'block', marginBottom: '0.5rem' }}>
-            Email
-          </label>
-          <input
-            type="email"
-            value={email}
-            onChange={(e) => setEmail(e.target.value)}
-            disabled={loading}
+    return (
+        <div
             style={{
-              width: '100%',
-              padding: '0.5rem',
-              fontSize: '1rem',
-              backgroundColor: '#1a1a1a',
-              border: '1px solid #444',
-              borderRadius: '4px',
-              color: 'white'
+                maxWidth: "400px",
+                margin: "4rem auto",
+                padding: "2rem",
+                border: "1px solid #333",
+                borderRadius: "8px",
             }}
-            required
-          />
-        </div>
-
-        <div style={{ marginBottom: '1rem' }}>
-          <label style={{ display: 'block', marginBottom: '0.5rem' }}>
-            Password
-          </label>
-          <input
-            type="password"
-            value={password}
-            onChange={(e) => setPassword(e.target.value)}
-            disabled={loading}
-            style={{
-              width: '100%',
-              padding: '0.5rem',
-              fontSize: '1rem',
-              backgroundColor: '#1a1a1a',
-              border: '1px solid #444',
-              borderRadius: '4px',
-              color: 'white'
-            }}
-            required
-          />
-        </div>
-
-        <div style={{ marginBottom: '1.5rem' }}>
-          <label style={{ display: 'block', marginBottom: '0.5rem' }}>
-            Confirm Password
-          </label>
-          <input
-            type="password"
-            value={confirmPassword}
-            onChange={(e) => setConfirmPassword(e.target.value)}
-            disabled={loading}
-            style={{
-              width: '100%',
-              padding: '0.5rem',
-              fontSize: '1rem',
-              backgroundColor: '#1a1a1a',
-              border: '1px solid #444',
-              borderRadius: '4px',
-              color: 'white'
-            }}
-            required
-          />
-        </div>
-
-        <button
-          type="submit"
-          disabled={loading}
-          style={{
-            width: '100%',
-            padding: '0.75rem',
-            fontSize: '1rem',
-            backgroundColor: loading ? '#333' : '#0066cc',
-            color: 'white',
-            border: 'none',
-            borderRadius: '4px',
-            cursor: loading ? 'not-allowed' : 'pointer'
-          }}
         >
-          {loading ? 'Creating account...' : 'Sign Up'}
-        </button>
-      </form>
+            <h1 style={{ marginBottom: "2rem", textAlign: "center" }}>
+                Koin Ping - Sign Up
+            </h1>
 
-      <div style={{ marginTop: '1.5rem', textAlign: 'center' }}>
-        <p style={{ color: '#999' }}>
-          Already have an account?{' '}
-          <Link 
-            to="/login" 
-            style={{ color: '#0066cc', textDecoration: 'none' }}
-          >
-            Log in here
-          </Link>
-        </p>
-      </div>
-    </div>
-  );
+            {error && (
+                <div
+                    style={{
+                        padding: "0.75rem",
+                        marginBottom: "1rem",
+                        backgroundColor: "#ff000020",
+                        border: "1px solid #ff0000",
+                        borderRadius: "4px",
+                        color: "#ff6666",
+                    }}
+                >
+                    {error}
+                </div>
+            )}
+
+            <form onSubmit={handleSubmit}>
+                <div style={{ marginBottom: "1rem" }}>
+                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
+                        Email
+                    </label>
+                    <input
+                        type="email"
+                        value={email}
+                        onChange={(e) => setEmail(e.target.value)}
+                        disabled={loading}
+                        style={{
+                            width: "100%",
+                            padding: "0.5rem",
+                            fontSize: "1rem",
+                            backgroundColor: "#242424",
+                            border: "1px solid #444",
+                            borderRadius: "4px",
+                            color: "white",
+                        }}
+                        required
+                    />
+                </div>
+
+                <div style={{ marginBottom: "1rem" }}>
+                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
+                        Password
+                    </label>
+                    <input
+                        type="password"
+                        value={password}
+                        onChange={(e) => setPassword(e.target.value)}
+                        disabled={loading}
+                        style={{
+                            width: "100%",
+                            padding: "0.5rem",
+                            fontSize: "1rem",
+                            backgroundColor: "#242424",
+                            border: "1px solid #444",
+                            borderRadius: "4px",
+                            color: "white",
+                        }}
+                        required
+                    />
+                </div>
+
+                <div style={{ marginBottom: "1.5rem" }}>
+                    <label style={{ display: "block", marginBottom: "0.5rem" }}>
+                        Confirm Password
+                    </label>
+                    <input
+                        type="password"
+                        value={confirmPassword}
+                        onChange={(e) => setConfirmPassword(e.target.value)}
+                        disabled={loading}
+                        style={{
+                            width: "100%",
+                            padding: "0.5rem",
+                            fontSize: "1rem",
+                            backgroundColor: "#242424",
+                            border: "1px solid #444",
+                            borderRadius: "4px",
+                            color: "white",
+                        }}
+                        required
+                    />
+                </div>
+
+                <button
+                    type="submit"
+                    disabled={loading}
+                    style={{
+                        width: "100%",
+                        padding: "0.75rem",
+                        fontSize: "1rem",
+                        backgroundColor: loading ? "#333" : "#0066cc",
+                        color: "white",
+                        border: "none",
+                        borderRadius: "4px",
+                        cursor: loading ? "not-allowed" : "pointer",
+                    }}
+                >
+                    {loading ? "Creating account..." : "Sign Up"}
+                </button>
+            </form>
+
+            <div style={{ marginTop: "1.5rem", textAlign: "center" }}>
+                <p style={{ color: "#b3b3b3" }}>
+                    Already have an account?{" "}
+                    <Link
+                        to="/login"
+                        style={{ color: "#0066cc", textDecoration: "none" }}
+                    >
+                        Log in here
+                    </Link>
+                </p>
+            </div>
+        </div>
+    );
 }
-

frontend/tsconfig.json

@@ -1,25 +1,24 @@
 {
-  "compilerOptions": {
-    "target": "ES2020",
-    "useDefineForClassFields": true,
-    "lib": ["ES2020", "DOM", "DOM.Iterable"],
-    "module": "ESNext",
-    "skipLibCheck": true,
+    "compilerOptions": {
+        "target": "ES2020",
+        "useDefineForClassFields": true,
+        "lib": ["ES2020", "DOM", "DOM.Iterable"],
+        "module": "ESNext",
+        "skipLibCheck": true,
 
-    /* Bundler mode */
-    "moduleResolution": "bundler",
-    "allowImportingTsExtensions": true,
-    "resolveJsonModule": true,
-    "isolatedModules": true,
-    "noEmit": true,
-    "jsx": "react-jsx",
+        /* Bundler mode */
+        "moduleResolution": "bundler",
+        "allowImportingTsExtensions": true,
+        "resolveJsonModule": true,
+        "isolatedModules": true,
+        "noEmit": true,
+        "jsx": "react-jsx",
 
-    /* Linting */
-    "strict": true,
-    "noUnusedLocals": true,
-    "noUnusedParameters": true,
-    "noFallthroughCasesInSwitch": true
-  },
-  "include": ["src"]
+        /* Linting */
+        "strict": true,
+        "noUnusedLocals": true,
+        "noUnusedParameters": true,
+        "noFallthroughCasesInSwitch": true
+    },
+    "include": ["src"]
 }
-

frontend/vite.config.js

@@ -1,17 +1,16 @@
-import { defineConfig } from 'vite'
-import react from '@vitejs/plugin-react'
+import { defineConfig } from "vite";
+import react from "@vitejs/plugin-react";
 
 // https://vitejs.dev/config/
 export default defineConfig({
-  plugins: [react()],
-  server: {
-    port: 3000,
-    proxy: {
-      '/v1': {
-        target: 'http://localhost:3001',
-        changeOrigin: true,
-      },
+    plugins: [react()],
+    server: {
+        port: 3000,
+        proxy: {
+            "/v1": {
+                target: "http://localhost:3001",
+                changeOrigin: true,
+            },
+        },
     },
-  },
-})
-
+});