import { execFile } from 'node:child_process';
import { mkdir, readFile } from 'node:fs/promises';
import { join } from 'node:path';
import { promisify } from 'node:util';

const execFileAsync = promisify(execFile);
const fail = (rule) => { throw new Error(rule); };

export const runMediaCommand = async (command, args, rule, timeout = 60_000) => {
  try {
    return await execFileAsync(command, args, {
      encoding: 'utf8', timeout, maxBuffer: 8 * 1024 * 1024, windowsHide: true,
    });
  } catch {
    fail(rule);
  }
};

export const probeVideo = async (path, options = {}) => {
  const { stdout } = await runMediaCommand('ffprobe', [
    '-v', 'error', '-show_entries', 'format=duration:stream=index,codec_type,width,height,duration',
    '-of', 'json', path,
  ], 'ASSET-VIDEO-PROBE-001', 20_000);
  let probe;
  try { probe = JSON.parse(stdout); } catch { fail('ASSET-VIDEO-PROBE-001'); }
  const videoStreams = probe.streams?.filter((stream) => stream.codec_type === 'video') ?? [];
  const audioStreams = probe.streams?.filter((stream) => stream.codec_type === 'audio') ?? [];
  const unexpected = probe.streams?.filter((stream) => !['video', 'audio'].includes(stream.codec_type)) ?? [];
  const duration = Number(probe.format?.duration ?? videoStreams[0]?.duration);
  if (videoStreams.length !== 1 || unexpected.length > 0 || (options.allowAudio === false && audioStreams.length > 0) ||
    !Number.isFinite(duration) || duration <= 0 || duration > 120) {
    fail('ASSET-VIDEO-PROBE-001');
  }
  return { duration, width: Number(videoStreams[0].width), height: Number(videoStreams[0].height) };
};

export const encodeVideoDerivatives = async ({ source, webmPath, mp4Path, posterPath, startSeconds, durationSeconds, maxWidth }) => {
  const common = [
    '-hide_banner', '-loglevel', 'error', '-nostdin', '-y', '-threads', '1',
    '-ss', String(startSeconds), '-i', source, '-t', String(durationSeconds), '-map', '0:v:0',
    '-an', '-sn', '-dn', '-vf', `scale=w='min(${maxWidth},iw)':h=-2:flags=lanczos`,
    '-map_metadata', '-1', '-map_chapters', '-1', '-pix_fmt', 'yuv420p',
  ];
  await runMediaCommand('ffmpeg', [
    ...common, '-fflags', '+bitexact', '-flags:v', '+bitexact',
    '-c:v', 'libvpx-vp9', '-deadline', 'good', '-cpu-used', '4', '-row-mt', '0',
    '-b:v', '0', '-crf', '34', '-threads', '1', webmPath,
  ], 'ASSET-VIDEO-ENCODE-001', 120_000);
  await runMediaCommand('ffmpeg', [
    ...common, '-fflags', '+bitexact', '-flags:v', '+bitexact',
    '-c:v', 'libx264', '-preset', 'slow', '-crf', '25', '-threads', '1',
    '-movflags', '+faststart', mp4Path,
  ], 'ASSET-VIDEO-ENCODE-001', 120_000);
  await runMediaCommand('ffmpeg', [
    '-hide_banner', '-loglevel', 'error', '-nostdin', '-y', '-threads', '1',
    '-ss', '0.05', '-i', webmPath, '-frames:v', '1', '-an', '-sn', '-dn', '-map_metadata', '-1', posterPath,
  ], 'ASSET-VIDEO-POSTER-001', 30_000);
};

export const extractVideoFrames = async ({ source, durationSeconds, outputDir, prefix = 'frame' }) => {
  await mkdir(outputDir, { recursive: true });
  const points = [...new Set([0.05, durationSeconds / 2, Math.max(0.05, durationSeconds - 0.1)].map((value) => Math.min(durationSeconds, Math.max(0, value)).toFixed(3)))];
  const paths = [];
  for (const [index, point] of points.entries()) {
    const path = join(outputDir, `${prefix}-${String(index + 1).padStart(2, '0')}.png`);
    await runMediaCommand('ffmpeg', [
      '-hide_banner', '-loglevel', 'error', '-nostdin', '-y', '-threads', '1',
      '-ss', point, '-i', source, '-frames:v', '1', '-an', '-sn', '-dn', '-map_metadata', '-1', path,
    ], 'ASSET-VIDEO-FRAME-001', 30_000);
    if ((await readFile(path)).length === 0) fail('ASSET-VIDEO-FRAME-001');
    paths.push(path);
  }
  return paths;
};