Add Web Push warning notification backend

lib/push-store.ts

@@ -0,0 +1,51 @@
+import type { WarningPushSubscription } from "@/types/notifications";
+
+interface PushStore {
+  subscriptions: Map<string, WarningPushSubscription>;
+  sentWarningIds: Map<string, Set<string>>;
+}
+
+const globalStore = globalThis as typeof globalThis & { __wtrPushStore?: PushStore };
+
+function getStore() {
+  if (!globalStore.__wtrPushStore) {
+    globalStore.__wtrPushStore = {
+      subscriptions: new Map(),
+      sentWarningIds: new Map(),
+    };
+  }
+  return globalStore.__wtrPushStore;
+}
+
+export function upsertPushSubscription(subscription: WarningPushSubscription) {
+  getStore().subscriptions.set(subscription.endpoint, subscription);
+}
+
+export function removePushSubscription(endpoint: string) {
+  const store = getStore();
+  store.subscriptions.delete(endpoint);
+  store.sentWarningIds.delete(endpoint);
+}
+
+export function getPushSubscriptions() {
+  return Array.from(getStore().subscriptions.values());
+}
+
+export function hasSentWarning(endpoint: string, warningId: string) {
+  return getStore().sentWarningIds.get(endpoint)?.has(warningId) ?? false;
+}
+
+export function markWarningSent(endpoint: string, warningId: string) {
+  const store = getStore();
+  const sentIds = store.sentWarningIds.get(endpoint) ?? new Set<string>();
+  sentIds.add(warningId);
+  store.sentWarningIds.set(endpoint, sentIds);
+}
+
+export function pruneSentWarnings(activeWarningIds: Set<string>) {
+  getStore().sentWarningIds.forEach((sentIds) => {
+    sentIds.forEach((warningId) => {
+      if (!activeWarningIds.has(warningId)) sentIds.delete(warningId);
+    });
+  });
+}