refactor: separate installation and proximity context components

src/layers/installations/source.js

@@ -0,0 +1,78 @@
+/** Read mapped installations and explicit nearby-place searches through fixed endpoints. */
+export function createInstallationSource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+} = {}) {
+  return {
+    async getMappedSites(box, { exact = false, signal } = {}) {
+      const { south, west, north, east } = box || {};
+      if (
+        ![south, west, north, east].every(Number.isFinite) ||
+        south < -90 ||
+        north > 90 ||
+        west < -180 ||
+        east > 180 ||
+        north <= south ||
+        east <= west ||
+        north - south > 10 ||
+        east - west > 10
+      )
+        throw new TypeError('A bounded installation viewport is required');
+      signal?.throwIfAborted();
+      const query = new URLSearchParams(
+        Object.entries({ south, west, north, east }).map(([key, value]) => [
+          key,
+          value.toFixed(5),
+        ]),
+      );
+      if (exact) query.set('exact', '1');
+      const response = await fetchImpl(`/api/military-installations?${query}`, {
+        signal,
+      });
+      const body = await response.json();
+      signal?.throwIfAborted();
+      if (!response.ok)
+        throw Object.assign(
+          new Error(body?.error || `Installation feed HTTP ${response.status}`),
+          {
+            failureReason: ['rate_limited', 'timeout', 'query_failed'].includes(
+              body?.reason,
+            )
+              ? body.reason
+              : 'unavailable',
+          },
+        );
+      if (!Array.isArray(body?.elements))
+        throw new Error('Malformed installation snapshot');
+      return body;
+    },
+    async searchNearby({ latitude, longitude, radiusM }, { signal } = {}) {
+      if (
+        ![latitude, longitude, radiusM].every(Number.isFinite) ||
+        Math.abs(latitude) > 90 ||
+        Math.abs(longitude) > 180 ||
+        radiusM < 1000 ||
+        radiusM > 50000
+      )
+        throw new TypeError('Invalid nearby installation search');
+      signal?.throwIfAborted();
+      const response = await fetchImpl(
+        `/api/google/text-search?${new URLSearchParams({
+          q: 'military installation',
+          lat: latitude.toFixed(5),
+          lon: longitude.toFixed(5),
+          radiusM: String(radiusM),
+        })}`,
+        { signal },
+      );
+      const payload = await response.json();
+      signal?.throwIfAborted();
+      if (!response.ok)
+        throw new Error(
+          payload?.error || `Google Places HTTP ${response.status}`,
+        );
+      if (!Array.isArray(payload?.places))
+        throw new Error('Malformed nearby-place snapshot');
+      return payload;
+    },
+  };
+}