// server.js (Node.js + Express) - yt-dlp + ffmpeg required
const express = require('express');
const rateLimit = require('express-rate-limit');
const { spawn } = require('child_process');
const path = require('path');
const fs = require('fs');
const os = require('os');
const helmet = require('helmet');
const cors = require('cors');

const app = express();
app.use(helmet());
app.use(cors());
app.use(express.json({ limit:'1mb' }));

const limiter = rateLimit({ windowMs:60*1000, max:6 });
app.use(limiter);

const TMP = process.env.TEMP_FOLDER || path.join(os.tmpdir(),'multiimagex-yt-mp3');
if(!fs.existsSync(TMP)) fs.mkdirSync(TMP,{recursive:true});

function safeName(pre){ return `${pre}-${Date.now()}-${Math.random().toString(36).slice(2,8)}.mp3`; }
function validateYT(u){
  try{ const url = new URL(u); return /youtube|youtu.be/.test(url.hostname); }catch(e){ return false; }
}

app.post('/api/convert-mp3', async (req,res)=>{
  const { url, bitrate } = req.body || {};
  if(!url || !validateYT(url)) return res.json({ ok:false, error:'Invalid YouTube URL' });
  const bit = (['128','192','256','320'].includes(String(bitrate)))? String(bitrate) : '320';
  const outBasename = safeName('audio');
  const outTemplate = path.join(TMP, outBasename.replace('.mp3','.%\(ext\)s')); // yt-dlp template

  // Build args
  const args = [
    '-f','bestaudio',
    '--no-playlist',
    '--restrict-filenames',
    '-o', path.join(TMP, outBasename.replace('.mp3','.%(ext)s')),
    url,
    '--extract-audio','--audio-format','mp3','--postprocessor-args', `-b:a ${bit}k`
  ];

  // spawn yt-dlp
  try{
    const proc = spawn('yt-dlp', args, { shell: true });
    let stderr = '';
    proc.stderr.on('data', d => stderr += d.toString());
    proc.on('close', code => {
      // find newest mp3 in TMP
      const files = fs.readdirSync(TMP).filter(f => f.endsWith('.mp3')).map(f => ({ f, m: fs.statSync(path.join(TMP,f)).mtimeMs })).sort((a,b)=>b.m-a.m);
      if(!files.length) return res.json({ ok:false, error: 'conversion failed', details: stderr });
      const latest = files[0].f;
      return res.json({ ok:true, downloadUrl: '/static/' + encodeURIComponent(latest) });
    });
  }catch(err){
    return res.json({ ok:false, error: err.message });
  }
});

app.use('/static', express.static(TMP, { index:false }));

// cleanup files older than 12 hours
setInterval(()=>{
  try{
    const now = Date.now();
    fs.readdirSync(TMP).forEach(f=>{
      const p = path.join(TMP,f);
      try{ const s = fs.statSync(p); if(now - s.mtimeMs > 12*3600*1000) fs.unlinkSync(p); }catch(e){}
    });
  }catch(e){}
}, 60*60*1000);

const PORT = process.env.PORT || 3000;
app.listen(PORT, ()=> console.log('YT→MP3 server running on', PORT));