feat: add a Bhote Koshi flood event tool

src/sources/eventPacks.js

@@ -0,0 +1,24 @@
+/** Event packs the app serves under `/events/<id>/`, read once per id. */
+
+const EVENT_ID = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;
+
+export function createEventPackSource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+} = {}) {
+  const cache = new Map();
+  return {
+    async getEvent(id, { signal } = {}) {
+      if (!EVENT_ID.test(id)) throw new TypeError(`Invalid event id: ${id}`);
+      if (!cache.has(id)) {
+        signal?.throwIfAborted();
+        const response = await fetchImpl(`/events/${id}/event.json`, {
+          signal,
+        });
+        if (!response.ok)
+          throw new Error(`Event pack ${id} unavailable (${response.status})`);
+        cache.set(id, await response.json());
+      }
+      return cache.get(id);
+    },
+  };
+}