#!/usr/bin/env node
// E2E fake ffmpeg. Recognises two invocation shapes:
//
//   1. Transcode: ffmpeg -y -i <src> -vn -c:a <codec> <out>
//      -> writes a small placeholder to <out>. If <src> contains the
//         CORRUPT_MARKER sentinel, exits 1 with a libavcodec-style stderr
//         line so the audio-check classifier flags it as malformed.
//      -> If <out> is /dev/null (the audio-checked probe), behaves the
//         same w.r.t. corruption detection but doesn't actually write
//         output.
import { readFile, writeFile } from "node:fs/promises";
import { installFixtureWatchdog } from "./_watchdog.mjs";

// Never outlive the run that spawned us — see _watchdog.mjs.
installFixtureWatchdog();

const CORRUPT_MARKER = "__CORRUPT__";
// When the probed file contains this marker, the probe (and transcode) sleeps
// SLOW_PROBE_MS before finishing. The audio-check pause test embeds it so the
// integrity probe takes meaningfully longer than the download's chunk cadence,
// making the "download is frozen during the probe" behaviour observable.
const SLOW_PROBE_MARKER = "__SLOWPROBE__";
const SLOW_PROBE_MS = 600;

const argv = process.argv.slice(2);

function arg(flag) {
  const i = argv.indexOf(flag);
  if (i < 0) return undefined;
  return argv[i + 1];
}

function sleep(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

async function readSrc(file) {
  try {
    return await readFile(file);
  } catch {
    return null;
  }
}

const src = arg("-i") ?? "<unknown>";
const out = argv[argv.length - 1];
if (!out || out.startsWith("-")) {
  process.stderr.write(`[fake-ffmpeg] missing output path\n`);
  process.exit(2);
}

const srcBuf = await readSrc(src);
if (srcBuf?.includes(SLOW_PROBE_MARKER)) {
  await sleep(SLOW_PROBE_MS);
}

if (srcBuf?.includes(CORRUPT_MARKER)) {
  process.stderr.write(
    `[aac @ 0x1234] Sample rate index in program config element does not match the sample rate index configured by the container.\n`,
  );
  process.exit(1);
}

if (out === "/dev/null") {
  // Probe invocation — no output written. Real ffmpeg would also print a
  // "partial file" warning here if the input was truncated; we don't need
  // to simulate that for the exit-code-driven classifier.
  process.exit(0);
}

await writeFile(out, `fake-ffmpeg transcoded from ${src}\n`);
process.stdout.write(`[fake-ffmpeg] wrote ${out}\n`);