import { google } from "googleapis";
import fs from "fs";
import path from "path";
import readline from "readline";

const __dirname = path.dirname(new URL(import.meta.url).pathname);
const PROJECT_ROOT = path.resolve(__dirname, "..");
const CREDENTIALS_PATH = path.join(PROJECT_ROOT, "credentials.json");
const TOKEN_PATH = path.join(PROJECT_ROOT, "token.json");

// Gmail modify scope: read, send, delete, and manage labels
const SCOPES = ["https://www.googleapis.com/auth/gmail.modify"];

async function authorize(): Promise<void> {
  if (!fs.existsSync(CREDENTIALS_PATH)) {
    console.error(
      `Missing ${CREDENTIALS_PATH}\n\n` +
        "To create this file:\n" +
        "1. Go to https://console.cloud.google.com/\n" +
        "2. Create a project and enable the Gmail API\n" +
        "3. Create OAuth 2.0 credentials (Desktop app type)\n" +
        "4. Download the JSON and save it as credentials.json in the project root\n"
    );
    process.exit(1);
  }

  const credentials = JSON.parse(fs.readFileSync(CREDENTIALS_PATH, "utf-8"));
  const { client_id, client_secret, redirect_uris } =
    credentials.installed || credentials.web;

  const oAuth2Client = new google.auth.OAuth2(
    client_id,
    client_secret,
    redirect_uris[0]
  );

  // Check if we already have a valid token
  if (fs.existsSync(TOKEN_PATH)) {
    const token = JSON.parse(fs.readFileSync(TOKEN_PATH, "utf-8"));
    oAuth2Client.setCredentials(token);
    console.log("Token already exists at:", TOKEN_PATH);
    console.log("To re-authorize, delete token.json and run this script again.");
    return;
  }

  // Generate auth URL and prompt user
  const authUrl = oAuth2Client.generateAuthUrl({
    access_type: "offline",
    scope: SCOPES,
    prompt: "consent",
  });

  console.log("Authorize this app by visiting this URL:\n");
  console.log(authUrl);
  console.log();

  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });

  const rawInput = await new Promise<string>((resolve) => {
    rl.question(
      "Paste the FULL URL from your browser address bar (or just the code): ",
      (answer) => {
        rl.close();
        resolve(answer.trim());
      }
    );
  });

  // Extract the code whether they pasted the full URL or just the code
  let code = rawInput;
  if (rawInput.includes("code=")) {
    const url = new URL(rawInput);
    code = url.searchParams.get("code") ?? rawInput;
  }

  console.log(`\nExtracted code: ${code.substring(0, 10)}...`);

  const { tokens } = await oAuth2Client.getToken(code);
  oAuth2Client.setCredentials(tokens);

  fs.writeFileSync(TOKEN_PATH, JSON.stringify(tokens, null, 2));
  console.log("\nToken saved to:", TOKEN_PATH);
  console.log("You can now start the MCP server.");
}

authorize().catch((err) => {
  console.error("Authorization failed:", err);
  process.exit(1);
});