/**
 * Vite plugin: adsb.lol military aircraft proxy with 12 s response cache.
 *
 * Proxies GET /api/adsblol/mil to https://api.adsb.lol/v2/mil. On upstream
 * failure, serves a stale cached response if one exists.
 *
 * @returns {import('vite').Plugin}
 */
export function adsbLolProxy() {
  /** @type {string|null} Cached upstream JSON body. */
  let _cache = null;
  /** @type {number} Epoch-ms when the cache was populated. */
  let _cacheAt = 0;
  /** Response cache TTL (ms). */
  const CACHE_MS = 12000;
  return {
    name: 'adsblol-proxy',
    configureServer(server) {
      server.middlewares.use('/api/adsblol/mil', async (req, res) => {
        try {
          const now = Date.now();
          if (_cache && now - _cacheAt < CACHE_MS) {
            res.writeHead(200, { 'Content-Type': 'application/json', 'Cache-Control': 'no-store', 'X-ADS-B-Cache': 'HIT' });
            res.end(_cache);
            return;
          }
          const upstream = await fetch('https://api.adsb.lol/v2/mil', {
            headers: { 'User-Agent': 'gods-eye-view-adsblol-proxy/1.0' },
          });
          const body = await upstream.text();
          if (upstream.ok) {
            _cache = body;
            _cacheAt = now;
          }
          res.writeHead(upstream.status, { 'Content-Type': 'application/json', 'Cache-Control': 'no-store', 'X-ADS-B-Cache': 'MISS' });
          res.end(body);
        } catch (e) {
          console.error('[adsb.lol Proxy]', e.message);
          if (_cache) {
            res.writeHead(200, { 'Content-Type': 'application/json', 'X-ADS-B-Cache': 'STALE' });
            res.end(_cache);
            return;
          }
          res.writeHead(502, { 'Content-Type': 'application/json' });
          res.end(JSON.stringify({ error: 'ADS-B proxy error' }));
        }
      });
    },
  };
}