refactor: separate traffic and bikeshare components

src/layers/bikeshare/source.js

@@ -0,0 +1,23 @@
+/** Read a GBFS station document through the existing bounded server proxy. */
+export function createBikeshareSource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+} = {}) {
+  return {
+    async getStations(upstreamUrl, { signal } = {}) {
+      const url = new URL(upstreamUrl);
+      if (url.protocol !== 'https:' || url.username || url.password || url.hash)
+        throw new TypeError('A public HTTPS GBFS URL is required');
+      signal?.throwIfAborted();
+      const response = await fetchImpl(
+        '/api/gbfs?url=' + encodeURIComponent(url.href),
+        { method: 'GET', headers: { Accept: 'application/json' }, signal },
+      );
+      if (!response.ok) throw new Error('GBFS HTTP ' + response.status);
+      const payload = await response.json();
+      signal?.throwIfAborted();
+      if (!payload || typeof payload !== 'object')
+        throw new Error('Malformed GBFS payload');
+      return payload;
+    },
+  };
+}