SCENEGOD/scenegod/web/film.js

// film.js — multi-shot sequencing client (Lane C, M8-C).
//
//   renderSequence(stage, timeline, seqName, opts) -> Promise<url of the film mp4>
//
// A scene is one continuous take; a SEQUENCE is the film — an ordered list of
// shots, each a trimmed window of a saved scene, joined by cuts or dissolves.
// Only the browser can render a shot (three.js lives here), so the server
// orchestrates and this file does the work:
//
//   POST sequences/{name}/render  -> {filmId, fps, width, height, shots[]}
//   per shot: GET scenes/{scene} -> timeline.applyScene -> render frames
//             [in*fps, out*fps) through the ORDINARY render session endpoints
//             -> POST films/{id}/shot/{i} {renderId}
//   POST films/{id}/end -> ffmpeg concat/xfade -> poll -> films/{id}/out.mp4
//
// Shots are rendered SILENT on purpose: a film's soundtrack is the sequence's
// own audio[] (mixed server-side over the finished cut), not per-scene audio —
// the server warns when a referenced scene has audio[] that will be skipped.
// All URLs relative (the app serves under /scenegod/ in prod).
import { withRenderSize, ssFactor, beginRender, captureFrames, endRender, pollRender,
         postJSON, getJSON } from './render.js';

const sleep = ms => new Promise(r => setTimeout(r, ms));

export async function renderSequence(stage, timeline, seqName, opts = {}) {
  const { width = 1920, height = 1080, onProgress, onShot, onWarning } = opts;
  const film = await postJSON(`sequences/${encodeURIComponent(seqName)}/render`, { width, height });
  const { filmId, fps, shots } = film;
  for (const w of film.warnings || []) (onWarning || (m => console.warn('[film]', m)))(w);
  if (!shots?.length) throw new Error('sequence has no shots');

  // one canvas resize for the whole film — shots must all be the same size, the
  // server rejects a mismatched shot at registration anyway. Rendered at ss x the
  // deliverable (2 up to 1080p) and downscaled by ffmpeg; begin still declares the
  // OUTPUT size, so meta.json and the film grid keep matching.
  const ss = ssFactor(width, height, opts.ss);
  await withRenderSize(stage, width * ss, height * ss, async () => {
    for (const shot of shots) {
      const i = shot.index;
      onShot?.(i, shots.length, shot);
      const scene = await getJSON(`scenes/${encodeURIComponent(shot.scene)}`);
      await timeline.applyScene(scene);          // stage.applyState + tracks + clip preload (Lane B)
      const from = Math.round(shot.in * fps), to = Math.round(shot.out * fps);
      const { renderId } = await beginRender({ name: `${seqName}-${i}`, fps, width, height });
      await captureFrames(stage, timeline, { renderId, from, to,
        onProgress: (done, total) => onProgress?.({ shot: i, of: shots.length, scene: shot.scene,
                                                    frame: done, frames: total }) });
      await endRender(renderId, [], { intermediate: true });   // silent (bed is film-level), crf 14
      await pollRender(renderId);                // shot mp4 must exist before we register it
      await postJSON(`films/${filmId}/shot/${i}`, { renderId });
    }
  });

  await postJSON(`films/${filmId}/end`, {});
  let st;
  do { await sleep(500); st = await getJSON(`films/${filmId}/status`); }
  while (st.state === 'collecting' || st.state === 'queued' || st.state === 'encoding');
  if (st.state !== 'done') throw new Error('film encode failed: ' + (st.log || st.state));
  return `films/${filmId}/out.mp4`;
}

// convenience: the sequence list/read/save/delete surface, so a UI lane never has
// to hand-roll the URLs (and never gets them absolute).
export const listSequences = () => getJSON('sequences');
export const getSequence = name => getJSON(`sequences/${encodeURIComponent(name)}`);
export const saveSequence = (name, seq) => postJSON(`sequences/${encodeURIComponent(name)}`, seq);
export async function deleteSequence(name) {
  const r = await fetch(`sequences/${encodeURIComponent(name)}`, { method: 'DELETE' });
  if (!r.ok) throw new Error(`delete ${name}: ${r.status}`);
  return r.json();
}