import http from "node:http";
import { execFile } from "node:child_process";
import { readFile, unlink, mkdir } from "node:fs/promises";
import { promisify } from "node:util";
import { Innertube } from "youtubei.js";
import { createClient } from "@supabase/supabase-js";

const execFileAsync = promisify(execFile);

// ── Config ────────────────────────────────────────────────────
const PORT = parseInt(process.env.PORT || "3001", 10);
const SUPABASE_URL = process.env.SUPABASE_URL;
const SUPABASE_SERVICE_ROLE_KEY = process.env.SUPABASE_SERVICE_ROLE_KEY;
const STORAGE_BUCKET = process.env.STORAGE_BUCKET || "workout-audio";
// Public-facing URL for constructing browser-accessible storage URLs.
// SUPABASE_URL is the internal Docker network URL (e.g. http://kong:8000)
// which browsers cannot reach.
const SUPABASE_PUBLIC_URL = process.env.SUPABASE_PUBLIC_URL || SUPABASE_URL;

if (!SUPABASE_URL || !SUPABASE_SERVICE_ROLE_KEY) {
  console.error("Missing SUPABASE_URL or SUPABASE_SERVICE_ROLE_KEY");
  process.exit(1);
}

const supabase = createClient(SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY);

// ── YouTube client (singleton, reused across requests) ────────
let ytClient = null;
let ytClientPromise = null;

async function getYouTubeClient() {
  if (ytClient) return ytClient;
  if (ytClientPromise) return ytClientPromise;

  ytClientPromise = Innertube.create({
    generate_session_locally: true,
    retrieve_player: true,
  }).then((client) => {
    ytClient = client;
    ytClientPromise = null;
    console.log("YouTube client initialized");
    return client;
  });

  return ytClientPromise;
}

// Pre-warm the client on startup
getYouTubeClient().catch((err) =>
  console.error("Failed to pre-warm YouTube client:", err.message)
);

// ── Helpers ───────────────────────────────────────────────────

function parsePlaylistId(url) {
  if (/^[A-Za-z0-9_-]+$/.test(url) && !url.includes(".")) {
    return url;
  }
  try {
    const parsed = new URL(url);
    const listParam = parsed.searchParams.get("list");
    if (listParam) return listParam;
  } catch {}
  throw new Error(`Could not parse playlist ID from: "${url}"`);
}

function readBody(req) {
  return new Promise((resolve, reject) => {
    const chunks = [];
    req.on("data", (c) => chunks.push(c));
    req.on("end", () => {
      try {
        resolve(JSON.parse(Buffer.concat(chunks).toString()));
      } catch (e) {
        reject(new Error("Invalid JSON body"));
      }
    });
    req.on("error", reject);
  });
}

function jsonResponse(res, status, data) {
  res.writeHead(status, { "Content-Type": "application/json" });
  res.end(JSON.stringify(data));
}

// ── Routes ────────────────────────────────────────────────────

async function handlePlaylist(req, res) {
  const { playlistUrl } = await readBody(req);
  if (!playlistUrl) {
    return jsonResponse(res, 400, { error: "playlistUrl is required" });
  }

  const playlistId = parsePlaylistId(playlistUrl);
  const yt = await getYouTubeClient();
  const playlist = await yt.getPlaylist(playlistId);

  const title = playlist.info.title ?? "Untitled Playlist";
  const items = [];

  function extractItems(page) {
    if (!page.items) return;
    for (const item of page.items) {
      // Only include items that have a video ID (skip Shorts/Reels)
      if (!item.id) continue;
      items.push({
        videoId: item.id,
        title: item.title?.toString() ?? "Untitled",
        durationSeconds: item.duration?.seconds ?? 0,
        thumbnailUrl: item.thumbnails?.[0]?.url ?? null,
      });
    }
  }

  // First page
  extractItems(playlist);

  // Pagination
  let page = playlist;
  while (page.has_continuation) {
    page = await page.getContinuation();
    extractItems(page);
  }

  console.log(`Playlist "${title}": ${items.length} items`);

  jsonResponse(res, 200, { title, items });
}

async function handleDownload(req, res) {
  const { videoId, jobId } = await readBody(req);
  if (!videoId || !jobId) {
    return jsonResponse(res, 400, { error: "videoId and jobId are required" });
  }

  // Use yt-dlp for the actual download — it handles PO tokens, signature
  // deciphering, and anti-bot measures that youtubei.js cannot.
  const tmpDir = `/tmp/ytdl-${jobId}`;
  const outPath = `${tmpDir}/${videoId}.m4a`;

  await mkdir(tmpDir, { recursive: true });

  try {
    console.log(`Downloading ${videoId} via yt-dlp...`);

    const { stderr } = await execFileAsync("yt-dlp", [
      "-f", "ba[ext=m4a]/ba",   // best audio in m4a, fallback to best audio
      "--no-playlist",
      "--no-warnings",
      "-x",                      // extract audio
      "--audio-format", "m4a",   // ensure m4a output
      "--audio-quality", "0",    // best quality
      "-o", outPath,
      `https://www.youtube.com/watch?v=${videoId}`,
    ], { timeout: 120_000 });

    if (stderr) console.warn(`yt-dlp stderr for ${videoId}: ${stderr}`);

    // Read the downloaded file
    const audioData = await readFile(outPath);
    console.log(
      `Downloaded ${videoId}: ${(audioData.length / 1024 / 1024).toFixed(1)} MB`
    );

    // Upload to Supabase Storage — flat structure, no subfolder
    const storagePath = `${videoId}.m4a`;

    const { error: uploadError } = await supabase.storage
      .from(STORAGE_BUCKET)
      .upload(storagePath, audioData, {
        contentType: "audio/mp4",
        cacheControl: "3600",
        upsert: true,
      });

    if (uploadError) {
      throw new Error(`Storage upload failed: ${uploadError.message}`);
    }

    // Construct public URL using the external-facing base URL, not the
    // internal Docker URL that supabase.storage.getPublicUrl() would use.
    const publicUrl = `${SUPABASE_PUBLIC_URL}/storage/v1/object/public/${STORAGE_BUCKET}/${storagePath}`;

    jsonResponse(res, 200, { storagePath, publicUrl });
  } finally {
    // Clean up temp file
    await unlink(outPath).catch(() => {});
  }
}

async function handleHealth(_req, res) {
  jsonResponse(res, 200, { status: "ok" });
}

// ── Server ────────────────────────────────────────────────────

const server = http.createServer(async (req, res) => {
  try {
    if (req.method === "GET" && req.url === "/health") {
      return await handleHealth(req, res);
    }
    if (req.method === "POST" && req.url === "/playlist") {
      return await handlePlaylist(req, res);
    }
    if (req.method === "POST" && req.url === "/download") {
      return await handleDownload(req, res);
    }
    jsonResponse(res, 404, { error: "Not found" });
  } catch (err) {
    console.error(`${req.method} ${req.url} error:`, err.message);
    jsonResponse(res, 500, { error: err.message });
  }
});

server.listen(PORT, () => {
  console.log(`youtube-worker listening on port ${PORT}`);
});