refactor(geography): separate cable sources and bundled lookup modules

src/layers/submarineCables/bundledSource.js

@@ -0,0 +1,42 @@
+// This dataset is CC BY-NC-SA 3.0, not the project's MIT license.
+// Commercial users must remove it or obtain a TeleGeography license.
+// See DATA_SOURCES.md and the bundled dataset's source.json.
+const cableUrl = new URL(
+  '../../data/local_data/telegeography_submarine_cables/cable-geo.json',
+  import.meta.url,
+).href;
+const landingPointUrl = new URL(
+  '../../data/local_data/telegeography_submarine_cables/landing-point-geo.json',
+  import.meta.url,
+).href;
+
+/** Supply GeoJSON collections without coupling the renderer to asset URLs. */
+export function createBundledCableSource({
+  fetchImpl = (...args) => fetch(...args),
+} = {}) {
+  async function read(url, signal) {
+    signal?.throwIfAborted();
+    const response = await fetchImpl(url, { signal, cache: 'force-cache' });
+    if (!response.ok) {
+      try {
+        await response.body?.cancel();
+      } catch {
+        /* best effort */
+      }
+      throw new Error(`HTTP ${response.status} for ${url}`);
+    }
+    const json = await response.json();
+    signal?.throwIfAborted();
+    return json;
+  }
+  return {
+    label: 'TeleGeography',
+    async fetch(signal) {
+      const [cables, landingPoints] = await Promise.all([
+        read(cableUrl, signal),
+        read(landingPointUrl, signal),
+      ]);
+      return { cables, landingPoints };
+    },
+  };
+}