import { Router } from 'express';

const router = Router();

/**
 * DEM 표고 프록시 — 브라우저 COEP(require-corp)/CSP(connect-src 'self') 때문에
 * 클라이언트가 외부 고도 API를 직접 호출하지 못한다. 서버가 중계해 같은 출처로 응답.
 *
 * GET /api/elevation?lat=36.4,36.5&lon=127.4,127.5  (배치, 콤마 구분)
 * 응답: { elevation: number[] } (입력 순서 보존)
 *
 * 1순위 open-topodata SRTM 30m(절벽/지형 더 정밀), 실패 시 open-meteo 90m 폴백.
 */
router.get('/', async (req, res) => {
  const latStr = String(req.query.lat ?? req.query.latitude ?? '');
  const lonStr = String(req.query.lon ?? req.query.longitude ?? '');
  if (!latStr || !lonStr) {
    res.status(400).json({ error: 'lat/lon required' });
    return;
  }
  const lats = latStr.split(',');
  const lons = lonStr.split(',');
  if (lats.length !== lons.length) {
    res.status(400).json({ error: 'lat/lon length mismatch' });
    return;
  }

  // 1) open-topodata SRTM 30m
  try {
    const locs = lats.map((la, i) => `${la.trim()},${lons[i].trim()}`).join('|');
    const r = await fetch(
      'https://api.opentopodata.org/v1/srtm30m?locations=' + encodeURIComponent(locs),
    );
    if (r.ok) {
      const j: any = await r.json();
      if (Array.isArray(j?.results)) {
        const elevation = j.results.map((x: any) =>
          typeof x?.elevation === 'number' ? x.elevation : null,
        );
        if (elevation.some((v: number | null) => v != null)) {
          res.json({ elevation, source: 'opentopodata-srtm30m' });
          return;
        }
      }
    }
  } catch {
    /* 폴백으로 진행 */
  }

  // 2) open-meteo 90m 폴백
  try {
    const r = await fetch(
      'https://api.open-meteo.com/v1/elevation?latitude=' +
        encodeURIComponent(latStr) +
        '&longitude=' +
        encodeURIComponent(lonStr),
    );
    if (!r.ok) {
      res.status(502).json({ error: 'upstream ' + r.status });
      return;
    }
    const j: any = await r.json();
    res.json({ elevation: j?.elevation ?? [], source: 'open-meteo-90m' });
  } catch (e) {
    res.status(502).json({ error: String(e) });
  }
});

export default router;