/**
 * Document processing API routes (OCR Pipeline)
 *
 * POST /api/documents/process  — Submit a document URL for OCR + embedding
 * GET  /api/documents          — List processed documents
 * GET  /api/documents/:id      — Get document chunks
 */
import { Router, Request, Response } from "express";
import { embed, upsertPoints, CollectionName } from "../embeddings/client";
import { pool } from "../db/client";
import { randomUUID } from "crypto";

export const documentRouter = Router();

const DOCLING_URL = process.env.DOCLING_URL || "http://localhost:8100";

interface DoclingResult {
  success: boolean;
  content: string;
  format: string;
  pages: number | null;
  error?: string;
}

/** Chunk markdown into overlapping sections */
function chunkMarkdown(
  markdown: string,
  maxChunkSize: number = 1500,
  overlapSize: number = 200,
): Array<{ heading: string; text: string }> {
  const sections = markdown.split(/(?=^#{1,3}\s)/m);
  const chunks: Array<{ heading: string; text: string }> = [];

  for (const section of sections) {
    const trimmed = section.trim();
    if (!trimmed || trimmed.length < 20) continue;

    const headingMatch = trimmed.match(/^(#{1,3})\s+(.+)/);
    const heading = headingMatch ? headingMatch[2].trim() : "Introduction";
    const body = headingMatch ? trimmed.slice(headingMatch[0].length).trim() : trimmed;

    if (body.length <= maxChunkSize) {
      chunks.push({ heading, text: body });
    } else {
      const paragraphs = body.split(/\n\n+/);
      let currentChunk = "";

      for (const para of paragraphs) {
        if (currentChunk.length + para.length > maxChunkSize && currentChunk.length > 0) {
          chunks.push({ heading, text: currentChunk.trim() });
          const overlapText = currentChunk.slice(-overlapSize);
          currentChunk = overlapText + "\n\n" + para;
        } else {
          currentChunk += (currentChunk ? "\n\n" : "") + para;
        }
      }

      if (currentChunk.trim().length > 20) {
        chunks.push({ heading, text: currentChunk.trim() });
      }
    }
  }

  return chunks;
}

// POST /api/documents/process — Process a document URL
documentRouter.post("/process", async (req: Request, res: Response) => {
  const { url, title, doc_type, vendor, collection } = req.body as {
    url?: string;
    title?: string;
    doc_type?: string;
    vendor?: string;
    collection?: string;
  };

  if (!url) {
    res.status(400).json({ success: false, error: "Missing 'url' in request body" });
    return;
  }

  const targetCollection = (collection || "datasheet_chunks") as CollectionName;
  if (!["datasheet_chunks", "manual_chunks"].includes(targetCollection)) {
    res.status(400).json({ success: false, error: "collection must be 'datasheet_chunks' or 'manual_chunks'" });
    return;
  }

  try {
    // Convert via Docling
    const docResp = await fetch(`${DOCLING_URL}/convert`, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ url, format: "markdown" }),
      signal: AbortSignal.timeout(120000),
    });

    if (!docResp.ok) {
      res.status(502).json({ success: false, error: "Docling conversion failed", detail: await docResp.text() });
      return;
    }

    const docResult = (await docResp.json()) as DoclingResult;
    if (!docResult.success) {
      res.status(502).json({ success: false, error: "Docling conversion failed", detail: docResult.error });
      return;
    }

    const documentId = randomUUID();
    const docTitle = title || url.split("/").pop()?.replace(/\.[^.]+$/, "") || "untitled";
    const docType = doc_type || "datasheet";
    const docVendor = vendor || "Unknown";

    // Chunk
    const chunks = chunkMarkdown(docResult.content);

    // Embed and store
    const BATCH_SIZE = 5;
    let stored = 0;

    for (let i = 0; i < chunks.length; i += BATCH_SIZE) {
      const batch = chunks.slice(i, i + BATCH_SIZE);
      const points = await Promise.all(
        batch.map(async (chunk, idx) => {
          const chunkIndex = i + idx;
          const embeddingText = `${docTitle}. ${chunk.heading}. ${chunk.text}`;
          const vector = await embed(embeddingText);
          return {
            id: randomUUID(),
            vector,
            payload: {
              document_id: documentId,
              source_url: url,
              document_type: docType,
              chunk_index: chunkIndex,
              total_chunks: chunks.length,
              title: docTitle,
              section_heading: chunk.heading,
              text: chunk.text,
              page_estimate: docResult.pages,
              vendor: docVendor,
              product_slug: docTitle.replace(/\s+/g, "-").toLowerCase(),
            },
          };
        }),
      );

      await upsertPoints(targetCollection, points);
      stored += points.length;
    }

    // Record in documents table (existing schema)
    try {
      await pool.query(
        `INSERT INTO documents (id, entity_type, doc_type, title, r2_key, source_url, page_count, chunks_count, ocr_status, ocr_text, processed_at)
         VALUES ($1, 'transceiver', $2, $3, $4, $5, $6, $7, 'completed', $8, NOW())
         ON CONFLICT ON CONSTRAINT documents_pkey DO UPDATE
           SET processed_at = NOW(), chunks_count = $7, ocr_status = 'completed'`,
        [documentId, docType, docTitle, `ocr/${documentId}`, url, docResult.pages, chunks.length, docResult.content.slice(0, 50000)],
      );
    } catch {
      // ignore if insert fails
    }

    res.json({
      success: true,
      document_id: documentId,
      title: docTitle,
      pages: docResult.pages,
      chunks: chunks.length,
      collection: targetCollection,
      markdown_length: docResult.content.length,
    });
  } catch (err) {
    res.status(503).json({
      success: false,
      error: "Document processing failed",
      detail: (err as Error).message,
    });
  }
});

// GET /api/documents — List processed documents
documentRouter.get("/", async (_req: Request, res: Response) => {
  try {
    const result = await pool.query(
      `SELECT id, title, source_url, doc_type, entity_type, page_count, chunks_count, ocr_status, processed_at, created_at
       FROM documents
       ORDER BY COALESCE(processed_at, created_at) DESC
       LIMIT 100`,
    );

    res.json({ success: true, documents: result.rows, count: result.rows.length });
  } catch {
    // Table may not exist — return empty
    res.json({ success: true, documents: [], count: 0, note: "documents table not yet created" });
  }
});

// GET /api/documents/:id — Get document details
documentRouter.get("/:id", async (req: Request, res: Response) => {
  try {
    const result = await pool.query(
      `SELECT id, title, source_url, doc_type, entity_type, page_count, chunks_count, ocr_status, processed_at, created_at
       FROM documents WHERE id = $1::uuid`,
      [req.params.id],
    );

    if (result.rows.length === 0) {
      res.status(404).json({ success: false, error: "Document not found" });
      return;
    }

    res.json({ success: true, document: result.rows[0] });
  } catch {
    res.status(404).json({ success: false, error: "Document not found or table not created" });
  }
});