import Anthropic from "@anthropic-ai/sdk";
import { embedNotes } from "./embedding.service.js";
import { validateStructure, computeCohesionScore } from "./validation.service.js";

const client = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
});

const buildPrompt = (notes) => {
  const notesJson = JSON.stringify(notes, null, 2);

  return `You are an expert at analyzing text for semantic similarity and thematic patterns.

Below is a JSON array of sticky notes. Each note has an "id" and a "text" field. Analyze the "text" field of every note and group them into meaningful thematic clusters.

For each cluster, return ONLY a valid JSON array with the below exact structure — no markdown, no explanation, no extra text - where the value for the "label" key is a name you create to describe the cluster's theme and the value for the "noteIds" key is an array containing the Ids of the notes that fit into that cluster theme.

[
  {
    "label": "Short descriptive theme name for cluster",
    "noteIds": ["note_001", "note_002"]
  }
]

Rules:
- Every note must appear in exactly one cluster
- Each cluster must have a concise, descriptive label
- Group by semantic meaning, not by keywords
- Aim for the most natural number of groups given the data

Here are the notes:

${notesJson}`;
};

const requestClusters = async (notes) => {
  const response = await client.messages.create({
    model: "claude-sonnet-4-20250514",
    max_tokens: 4096,
    messages: [
      { role: "user", content: buildPrompt(notes) },
    ],
  });

  const textBlock = response?.content?.[0];

  if (!textBlock || textBlock.type !== 'text' || typeof textBlock.text !== 'string') {
    throw new Error('Unexpected response from LLM API: no text content returned');
  }

  try {
    return JSON.parse(textBlock.text);
  } catch {
    throw new Error('LLM API returned non-JSON response');
  }
};

export const clusterNotes = async (notes) => {
  const [clusters, embeddingMap] = await Promise.all([
    requestClusters(notes),
    embedNotes(notes),
  ]);

  const noteIds = notes.map((n) => n.id);
  const { valid, reasons } = validateStructure(clusters, noteIds);
  if (!valid) {
    throw new Error(`Cluster validation failed: ${reasons.join('; ')}`);
  }

  const score = computeCohesionScore(clusters, embeddingMap);

  return { clusters, score: Math.round(score * 100) / 100 };
};