const express = require('express');
const cors = require('cors');

const app = express();
const PORT = 7860;

app.use(cors());
app.use(express.json());

function extractVideoId(url) {
  const match = url.match(/(?:youtube\.com\/(?:[^\/]+\/.+\/|(?:v|e(?:mbed)?)\/|.*[?&]v=)|youtu\.be\/)([^"&?\/\s]{11})/);
  return match ? match[1] : null;
}

function parseCaptionXml(xml) {
  const matches = xml.match(/<text[^>]*>([^<]*)<\/text>/g);
  if (!matches) return "";
  return matches
    .map(m => m.replace(/<[^>]+>/g, ''))
    .join(" ")
    .replace(/&amp;#39;/g, "'")
    .replace(/&amp;quot;/g, '"')
    .replace(/&amp;amp;/g, "&")
    .replace(/&#39;/g, "'")
    .replace(/\s+/g, ' ')
    .trim();
}

// ========================================================
// KEEP-ALIVE ENDPOINT
// ========================================================
app.get('/api/health', (req, res) => {
  res.json({ status: 'ok', message: 'Transcript API is running!' });
});

// ========================================================
// TRANSCRIPT API
// ========================================================
app.post('/api/transcript', async (req, res) => {
  try {
    const { url } = req.body;
    const videoId = extractVideoId(url);
    
    if (!videoId) {
      return res.status(400).json({ error: "Invalid YouTube URL" });
    }

    console.log(`Fetching InnerTube data for video_id: ${videoId}`);

    // Anti-bot headers and cookies to bypass YouTube blocks on Cloud IPs
    const headers = {
      "Content-Type": "application/json",
      "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36",
      "Origin": "https://www.youtube.com",
      "Referer": "https://www.youtube.com/",
      "Cookie": "CONSENT=YES+1; SOCS=CAESHAgBEhJnd3NfMjAyMzEwMjUtMF9SQzIaAmVuIAEaBgiA-LaoBg"
    };

    // 1. Fetch video player data from InnerTube API
    const playerRes = await fetch("https://www.youtube.com/youtubei/v1/player?prettyPrint=false", {
      method: "POST",
      headers: headers,
      body: JSON.stringify({
        context: {
          client: {
            clientName: "WEB",
            clientVersion: "2.20241210.00.00",
            hl: "en",
            gl: "US"
          }
        },
        videoId: videoId
      })
    });

    if (!playerRes.ok) {
      throw new Error(`YouTube API returned status ${playerRes.status}`);
    }

    const playerData = await playerRes.json();

    // Check if video is playable
    if (playerData.playabilityStatus?.status === "ERROR") {
      return res.status(404).json({ error: playerData.playabilityStatus?.reason || "Video unavailable" });
    }

    // 2. Extract caption tracks
    const captionTracks = playerData?.captions?.playerCaptionsTracklistRenderer?.captionTracks;

    if (!captionTracks || captionTracks.length === 0) {
      return res.status(404).json({ error: "No captions found for this video." });
    }

    // Prefer English, fallback to first available
    let selectedTrack = captionTracks.find(t => t.languageCode === 'en') || captionTracks[0];
    let captionUrl = selectedTrack.baseUrl;

    console.log(`Fetching captions from URL...`);

    // 3. Fetch the actual caption XML
    const captionRes = await fetch(captionUrl, {
      headers: { "User-Agent": headers["User-Agent"] }
    });

    if (!captionRes.ok) {
      throw new Error(`Caption fetch failed with status ${captionRes.status}`);
    }

    const captionXml = await captionRes.text();

    // 4. Parse the XML into plain text
    const fullText = parseCaptionXml(captionXml);

    if (!fullText) {
      return res.status(404).json({ error: "Caption XML was empty." });
    }

    console.log(`Successfully fetched transcript. Length: ${fullText.length} chars`);
    res.json({ text: fullText });

  } catch (error) {
    console.error("Transcript Error:", error.message);
    res.status(500).json({ error: "Could not fetch transcript. " + error.message });
  }
});

// ========================================================
// TRANSLATE API
// ========================================================
app.post('/api/translate', async (req, res) => {
  try {
    const { text, targetLang } = req.body;

    if (!text || !targetLang) {
      return res.status(400).json({ error: "Missing text or target language" });
    }

    const url = `https://translate.googleapis.com/translate_a/single?client=gtx&sl=auto&tl=${targetLang}&dt=t`;

    const fetchRes = await fetch(url, {
      method: "POST",
      headers: {
        "Content-Type": "application/x-www-form-urlencoded",
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36",
      },
      body: `q=${encodeURIComponent(text)}`,
    });

    if (!fetchRes.ok) {
      const errText = await fetchRes.text();
      console.error("Google API Error:", errText);
      throw new Error(`Translation service responded with status ${fetchRes.status}`);
    }

    const data = await fetchRes.json();
    const translated = data[0].map((item) => item[0]).join("");

    res.json({ translatedText: translated });
  } catch (error) {
    console.error("Translation API Error:", error.message);
    res.status(500).json({ error: "Failed to translate text. " + error.message });
  }
});

// Start server
app.listen(PORT, '0.0.0.0', () => {
  console.log(`Server running on http://0.0.0.0:${PORT}`);
});