const cache = require('./cache');
const { getCameraById } = require('./sources/smart-city-infra');

const UA = 'Mozilla/5.0 (compatible; MekTechShowcase/1.0)';

async function fetchImage(url) {
  const res = await fetch(url, {
    headers: { 'User-Agent': UA, Accept: 'image/*' },
    signal: AbortSignal.timeout(8000)
  });
  if (!res.ok) return null;
  const type = res.headers.get('content-type') || '';
  if (!type.includes('image')) return null;
  const buffer = Buffer.from(await res.arrayBuffer());
  if (buffer.length < 800) return null;
  return { buffer, contentType: type.split(';')[0] || 'image/jpeg' };
}

async function fetchCameraFrame(cameraId) {
  const cam = getCameraById(cameraId);
  if (!cam) return null;

  const cacheKey = `cam-frame-${cameraId}`;
  const cached = cache.get(cacheKey, 1100);
  if (cached) return cached;

  if (cam.youtubeId) {
    const urls = [
      `https://i.ytimg.com/vi/${cam.youtubeId}/maxresdefault_live.jpg`,
      `https://i.ytimg.com/vi/${cam.youtubeId}/hqdefault_live.jpg`,
      `https://i.ytimg.com/vi/${cam.youtubeId}/hqdefault.jpg`
    ];
    for (const url of urls) {
      try {
        const frame = await fetchImage(`${url}?t=${Date.now()}`);
        if (frame) {
          cache.set(cacheKey, frame);
          return frame;
        }
      } catch (_) { /* try next */ }
    }
  }

  return null;
}

module.exports = { fetchCameraFrame };