feat: Add support for editing video

Add an Edit

server/server.js

@@ -33,6 +33,7 @@ import { initDb, upsertUser, recordVideoAccess, getUserData, createProfile, getP
 const PORT        = parseInt(process.env.PORT || '3000', 10);
 const APP_VERSION = process.env.APP_VERSION || '1.0.0';
 const YTDLP       = process.env.YTDLP_PATH  || 'yt-dlp';
+const FFMPEG      = process.env.FFMPEG_PATH || 'ffmpeg';
 
 // ----------------------------------------------------------------------------
 // BUILD_TAG — must be DETERMINISTIC across restarts of identical code.
@@ -115,6 +116,68 @@ function runYtdlp(args) {
   });
 }
 
+// Run ffmpeg the same way — async spawn so a multi-minute trim/concat never
+// blocks Bun's event loop. Rejects on non-zero exit with ffmpeg's stderr tail.
+function runFfmpeg(args) {
+  return new Promise((resolve, reject) => {
+    const child = spawn(FFMPEG, args, { stdio: ['ignore', 'ignore', 'pipe'] });
+    let err = '';
+    child.stderr.setEncoding('utf8');
+    // ffmpeg is extremely chatty on stderr; keep only the tail so an error
+    // message stays useful without buffering the whole progress log.
+    child.stderr.on('data', (d) => { err = (err + d).slice(-4000); });
+    child.on('error', (e) => reject(new Error('ffmpeg not found: ' + e.message)));
+    child.on('close', (code) => {
+      if (code !== 0) reject(new Error(err.trim() || 'ffmpeg exited with code ' + code));
+      else resolve();
+    });
+  });
+}
+
+// Parse the compact "s-e,s-e" keep-segment string (see frontend/video-edit.js)
+// into an array of {start,end} second ranges. Skips malformed / non-increasing
+// tokens; returns [] on empty or all-garbage input. Kept in lockstep with the
+// frontend parseKeepParam so both ends agree on the wire format.
+function parseKeepParam(str) {
+  if (typeof str !== 'string') return [];
+  const out = [];
+  for (const tok of str.split(',')) {
+    const t = tok.trim();
+    if (!t) continue;
+    const m = t.match(/^(\d+(?:\.\d+)?)-(\d+(?:\.\d+)?)$/);
+    if (!m) continue;
+    const a = parseFloat(m[1]);
+    const b = parseFloat(m[2]);
+    if (!isFinite(a) || !isFinite(b) || b <= a) continue;
+    out.push({ start: a, end: b });
+  }
+  return out;
+}
+
+// Build an ffmpeg filter_complex that trims `src` to the keep segments and
+// concatenates them back into a single continuous stream. Re-encodes (the cut
+// points rarely fall on keyframes, so stream-copy would glitch), producing one
+// clean mp4. Returns the ffmpeg argv (input already appended by the caller).
+function buildTrimArgs(keep) {
+  const parts = [];
+  keep.forEach((k, i) => {
+    parts.push(
+      `[0:v]trim=start=${k.start}:end=${k.end},setpts=PTS-STARTPTS[v${i}]`,
+      `[0:a]atrim=start=${k.start}:end=${k.end},asetpts=PTS-STARTPTS[a${i}]`,
+    );
+  });
+  const concatInputs = keep.map((_, i) => `[v${i}][a${i}]`).join('');
+  const filter = parts.join(';') + ';' +
+    `${concatInputs}concat=n=${keep.length}:v=1:a=1[outv][outa]`;
+  return [
+    '-filter_complex', filter,
+    '-map', '[outv]', '-map', '[outa]',
+    '-c:v', 'libx264', '-preset', 'veryfast', '-crf', '20',
+    '-c:a', 'aac', '-b:a', '160k',
+    '-movflags', '+faststart',
+  ];
+}
+
 // Helpers to pick the right field from a yt-dlp JSON record
 function pick(obj, ...keys) {
   for (const k of keys) {
@@ -356,6 +419,58 @@ async function ytdlpDownloadResponse(videoId, fp, formatArgs) {
   });
 }
 
+// "Edit & download": fetch the source with yt-dlp (muxed up to 720p, same as
+// the mux path), then run ffmpeg to KEEP only the requested segments and
+// concatenate them into one continuous mp4 — the user's custom cut. The result
+// is streamed to the browser exactly like a normal save, so OPFS stores it
+// under the caller-chosen custom id. Every temp file is swept afterwards.
+async function ytdlpEditedDownloadResponse(videoId, fp, keep) {
+  const tmpBase = `ytp-edit-${videoId}-${Date.now()}`;
+  const srcTmp  = `${tmpdir()}/${tmpBase}.src.mp4`;
+  const outTmp  = `${tmpdir()}/${tmpBase}.out.mp4`;
+  let size, fd;
+  try {
+    // 1) Grab the full source (video+audio merged) so ffmpeg has both streams.
+    await runYtdlp([
+      `https://www.youtube.com/watch?v=${videoId}`,
+      '--no-warnings', '--no-playlist',
+      '-f', 'bv*[height<=720][ext=mp4]+ba[ext=m4a]/bv*[height<=720]+ba/b[ext=mp4]/b',
+      '--merge-output-format', 'mp4',
+      '-N', '4',
+      '-o', srcTmp,
+    ]);
+    // 2) Trim + concat the keep segments into the final custom video.
+    await runFfmpeg([
+      '-y', '-hide_banner', '-loglevel', 'error',
+      '-i', srcTmp,
+      ...buildTrimArgs(keep),
+      outTmp,
+    ]);
+    size = statSync(outTmp).size;
+    fd = openSync(outTmp, 'r');
+  } finally {
+    for (const name of readdirSync(tmpdir())) {
+      if (name.startsWith(tmpBase)) {
+        try { unlinkSync(`${tmpdir()}/${name}`); } catch { /* already gone */ }
+      }
+    }
+  }
+  const stream = createReadStream('', { fd });
+
+  if (fp) recordVideoAccess(fp, { id: videoId }).catch(() => {});
+
+  return new Response(Readable.toWeb(stream), {
+    status: 200,
+    headers: {
+      'Content-Type':        'video/mp4',
+      'Content-Length':      String(size),
+      'Content-Disposition': `attachment; filename="${videoId}-edited.mp4"`,
+      'Cache-Control':       'no-store',
+      'Access-Control-Allow-Origin': '*',
+    },
+  });
+}
+
 // GET /api/download/:videoId
 // Downloads the video server-side via yt-dlp and streams the finished file
 // to the browser so OPFS can store it. The browser never contacts YouTube
@@ -365,6 +480,20 @@ app.get('/api/download/:videoId', async (c) => {
   if (!videoId) return c.json({ ok: false, error: 'missing videoId' }, 400);
   const fp = c.req.query('fp');
 
+  // ?edit=1&keep=s-e,s-e — "Edit & download" path: download the source, then
+  // ffmpeg-trim it to the requested keep segments and stream the custom cut.
+  // Requires ffmpeg; there is no progressive fallback because the whole point
+  // is the server-side edit. Invalid/empty keep params are rejected up front.
+  if (c.req.query('edit') === '1') {
+    const keep = parseKeepParam(c.req.query('keep') || '');
+    if (!keep.length) return c.json({ ok: false, error: 'missing or invalid keep segments' }, 400);
+    try {
+      return await ytdlpEditedDownloadResponse(videoId, fp, keep);
+    } catch (err) {
+      return c.json({ ok: false, error: err.message }, 500);
+    }
+  }
+
   // ?mux=1 — "Save before playing" path: bestvideo up to 720p PLUS bestaudio
   // compiled into one mp4 with ffmpeg on the server. Falls back to the
   // progressive single-file save below when ffmpeg is missing or the merge