feat(push): dedupe FCM sends with 23h / 10m windows

Track lastNotifiedAt on stored tokens, preserve it on register upsert,
and skip messaging.send when inside the production or test-mode window.

src/db/fcmTokens.ts

@@ -11,6 +11,7 @@ type StoredRow = {
   testMode?: boolean;
   createdAt: string;
   updatedAt: string;
+  lastNotifiedAt?: string;
 };
 
 async function load(): Promise<Record<string, StoredRow>> {
@@ -49,7 +50,21 @@ export const db = {
       testMode: row.testMode,
       updatedAt: now,
       createdAt: prev?.createdAt ?? now,
+      lastNotifiedAt: prev?.lastNotifiedAt,
     };
     await save(all);
   },
+
+  async getByFcmToken(fcmToken: string): Promise<StoredRow | undefined> {
+    const all = await load();
+    return all[fcmToken];
+  },
+
+  async setLastNotifiedAt(fcmToken: string, at: Date): Promise<void> {
+    const all = await load();
+    const row = all[fcmToken];
+    if (row === undefined) return;
+    all[fcmToken] = { ...row, lastNotifiedAt: at.toISOString() };
+    await save(all);
+  },
 };

src/services/pushService.ts

@@ -1,8 +1,54 @@
-import type { Device } from "../models/device.js";
+import { messaging } from "./firebase.js";
+import { db } from "../db/fcmTokens.js";
 
-export async function sendPushToDevice(
-  _device: Device,
-  _payload: Record<string, unknown>
-): Promise<void> {
-  // TODO: integrate with push provider (FCM, APNs, etc.)
+const MS_PRODUCTION = 23 * 60 * 60 * 1000;
+const MS_TEST = 10 * 60 * 1000;
+
+function notifyThresholdMs(testMode?: boolean): number {
+  return testMode === true ? MS_TEST : MS_PRODUCTION;
+}
+
+function stringifyData(
+  payload: Record<string, unknown>
+): Record<string, string> {
+  const out: Record<string, string> = {};
+  for (const [k, v] of Object.entries(payload)) {
+    out[k] = v === undefined || v === null ? "" : String(v);
+  }
+  return out;
+}
+
+/**
+ * Sends an FCM data message if the token is outside the dedupe window
+ * (23h production, 10m test).
+ */
+export async function sendPushToDevice(
+  fcmToken: string,
+  payload: Record<string, unknown> = {}
+): Promise<"sent" | "skipped" | "failed"> {
+  const row = await db.getByFcmToken(fcmToken);
+  const now = Date.now();
+  const lastNotifiedAt = row?.lastNotifiedAt
+    ? Date.parse(row.lastNotifiedAt)
+    : undefined;
+
+  if (
+    lastNotifiedAt !== undefined &&
+    !Number.isNaN(lastNotifiedAt) &&
+    now - lastNotifiedAt < notifyThresholdMs(row?.testMode)
+  ) {
+    return "skipped";
+  }
+
+  try {
+    await messaging.send({
+      token: fcmToken,
+      data: stringifyData(payload),
+    });
+    await db.setLastNotifiedAt(fcmToken, new Date());
+    return "sent";
+  } catch (err) {
+    console.error("FCM send failed", err);
+    return "failed";
+  }
 }