/**
 * Runs the ffmpeg program (ffmpeg.mjs, beside this file) for johnmcm.com's
 * /dav-to-mp4 and /dss-to-mp3, one conversion per message, each in a fresh
 * instance (ffmpeg's main() is not made to run twice).
 *
 * The input File is mounted read-only with WORKERFS, so it is read in place
 * in slices however large it is. The output is a device that hands what
 * ffmpeg writes straight out into Blob pieces (run.mjs), so a
 * multi-gigabyte MP4 never sits whole in WebAssembly memory.
 *
 * Messages in:  { args: string[] (reading /in/<file name>, writing /out/<output>), file: File, output: string, type: string }
 * Messages out: { type: 'log', line } while running, then { type: 'done', code, blob, size } or { type: 'error', message }.
 *
 * Written for johnmcm.com (2026); part of the module published at /source/ffmpeg/.
 */

import createFFmpeg from './ffmpeg.mjs';
import { run } from './run.mjs';

let compiled = null;

function wasmModule() {
  compiled ??= WebAssembly.compileStreaming(fetch(new URL('./ffmpeg.wasm', import.meta.url)));
  return compiled;
}

self.onmessage = async (e) => {
  const { args, file, output, type } = e.data;
  try {
    const module = await wasmModule();
    const ff = await createFFmpeg({
      print: (line) => self.postMessage({ type: 'log', line }),
      printErr: (line) => self.postMessage({ type: 'log', line }),
      instantiateWasm(imports, done) {
        WebAssembly.instantiate(module, imports).then((instance) => done(instance));
        return {};
      },
    });
    const { code, blob, size } = run(ff, { args, name: file.name, file, output, type });
    self.postMessage({ type: 'done', code, blob, size });
  } catch (err) {
    self.postMessage({ type: 'error', message: String(err?.message || err) });
  }
};