feat: unify alerts into one plugin, channels, rules and inbox

src/backend/plugins/notify-hub.ts

@@ -0,0 +1,45 @@
+/**
+ * The one plugin that stores alerts and delivers them to channels. Core only
+ * resolves who an alert is for and hands it over; with no hub running an
+ * alert reaches nobody.
+ */
+
+import type { PluginNotifyHub } from "@termix/plugin-sdk/backend";
+import { hasCapability } from "./permissions.js";
+
+interface HubRegistration {
+  pluginId: string;
+  declared: readonly string[];
+  hub: PluginNotifyHub;
+}
+
+let current: HubRegistration | null = null;
+
+export function registerNotifyHub(registration: HubRegistration): () => void {
+  if (current && current.pluginId !== registration.pluginId) {
+    throw new Error(
+      `Plugin ${registration.pluginId} cannot serve alerts: ${current.pluginId} already does`,
+    );
+  }
+  current = registration;
+  return () => {
+    if (current === registration) current = null;
+  };
+}
+
+/** The running hub, or null while none is registered or its grant is gone. */
+export async function activeNotifyHub(): Promise<PluginNotifyHub | null> {
+  const registration = current;
+  if (!registration) return null;
+  const granted = await hasCapability(
+    registration.pluginId,
+    "notify:hub",
+    registration.declared,
+  );
+  return granted ? registration.hub : null;
+}
+
+/** Test seam. */
+export function clearNotifyHub(): void {
+  current = null;
+}