refactor(cctv): separate camera source and scene components

src/layers/cctv/source.js

@@ -0,0 +1,55 @@
+import {
+  ACTIVE_FRAME_REFRESH_MS,
+  FRAME_ENDPOINT,
+  MEDIA_ENDPOINT,
+} from './policy.js';
+function safeNumber(value, fallback = NaN) {
+  const n = Number(value);
+  return Number.isFinite(n) ? n : fallback;
+}
+function frameUrlFor(camera, refreshMs = ACTIVE_FRAME_REFRESH_MS) {
+  const cadenceMs = Math.max(
+    1000,
+    safeNumber(refreshMs, ACTIVE_FRAME_REFRESH_MS),
+  );
+  const tick = Math.floor(Date.now() / cadenceMs);
+  const params = new URLSearchParams({
+    label: camera.name,
+    city: camera.city,
+    lat: camera.lat.toFixed(6),
+    lon: camera.lon.toFixed(6),
+    heading: String(Math.round(camera.headingDeg)),
+    fov: String(Math.round(camera.fovDeg)),
+    pitch: String(Math.round(camera.pitchDeg || -10)),
+    ts: String(tick),
+  });
+  return `${FRAME_ENDPOINT}/${encodeURIComponent(camera.id)}?${params.toString()}`;
+}
+function mediaUrlFor(camera) {
+  return `${MEDIA_ENDPOINT}/${encodeURIComponent(camera.id)}?ts=${Math.floor(Date.now() / 15000)}`;
+}
+/** Supply catalog/health records and the existing registered camera URL families. */
+export function createCctvSource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+} = {}) {
+  async function read(path, key, { signal } = {}) {
+    signal?.throwIfAborted();
+    const response = await fetchImpl(path, { cache: 'no-store', signal });
+    if (!response.ok) throw new Error('Camera source HTTP ' + response.status);
+    const payload = await response.json();
+    signal?.throwIfAborted();
+    if (!Array.isArray(payload?.[key]))
+      throw new Error('Malformed camera ' + key + ' snapshot');
+    return payload;
+  }
+  return {
+    getCatalog(options) {
+      return read('/api/cctv/sources', 'sources', options);
+    },
+    getHealth(options) {
+      return read('/api/cctv/health', 'cameras', options);
+    },
+    getFrameUrl: frameUrlFor,
+    getMediaUrl: mediaUrlFor,
+  };
+}