import { execFile } from 'node:child_process';
import { promisify } from 'node:util';

const execFileAsync = promisify(execFile);

function parseRate(rate) {
  const [numerator, denominator] = String(rate || '0/1').split('/').map(Number);
  return denominator ? numerator / denominator : 0;
}

// Handyvideos liegen oft quer im Container und tragen die Drehung als Metadatum.
function readRotation(stream) {
  const side = stream.side_data_list?.find((entry) => entry.rotation !== undefined);
  if (side) return Number(side.rotation);
  if (stream.tags?.rotate) return Number(stream.tags.rotate);
  return 0;
}

// Länge aus dem Ende des letzten Pakets, wenn der Dateikopf keine nennt.
async function measureDuration(file) {
  const { stdout } = await execFileAsync(
    'ffprobe',
    ['-v', 'error', '-show_entries', 'packet=pts_time,duration_time', '-of', 'csv=p=0', file],
    { maxBuffer: 64 * 1024 * 1024 },
  );
  let end = 0;
  for (const line of stdout.split('\n')) {
    const [pts, duration] = line.split(',').map(Number);
    if (Number.isFinite(pts)) end = Math.max(end, pts + (Number.isFinite(duration) ? duration : 0));
  }
  return end > 0 ? end : null;
}

// Liefert die Eckdaten einer Video- oder Audiodatei; Breite und Höhe so,
// wie das Video angezeigt wird.
export async function probe(file) {
  const { stdout } = await execFileAsync(
    'ffprobe',
    ['-v', 'error', '-print_format', 'json', '-show_streams', '-show_format', file],
    { maxBuffer: 10 * 1024 * 1024 },
  );
  const info = JSON.parse(stdout);
  const video = info.streams.find(
    (stream) => stream.codec_type === 'video' && !stream.disposition?.attached_pic,
  );
  const audio = info.streams.find((stream) => stream.codec_type === 'audio');
  const hasAudio = Boolean(audio);
  if (!video && !hasAudio) throw new Error('Weder Bild noch Ton gefunden.');

  // Browser-Aufnahmen (WebM) tragen oft keine Gesamtlänge im Kopf.
  const duration =
    [info.format?.duration, video?.duration, audio?.duration].map(Number).find(Number.isFinite) ??
    (await measureDuration(file));
  if (!video) {
    return { duration, hasVideo: false, width: null, height: null, rotation: 0, fps: 0, hasAudio };
  }
  const rotation = readRotation(video);
  const sideways = Math.abs(rotation) % 180 === 90;
  return {
    duration,
    hasVideo: true,
    width: sideways ? video.height : video.width,
    height: sideways ? video.width : video.height,
    rotation,
    fps: Math.round(parseRate(video.avg_frame_rate || video.r_frame_rate) * 100) / 100,
    hasAudio,
  };
}