fix(notif): fix Android background push notification delivery and deduplicate alerts

backend/src/controllers/notificationController.js

@@ -2,9 +2,28 @@ const db = require('../config/db');
 const fcmService = require('../services/fcmService');
 fcmService.init();
 
+// In-memory debouncer to prevent rapid duplicate notification creation (within 2 seconds)
+const _recentCreates = new Map();
+
 // Programmatic helper to create notifications (can be called from other controllers)
 // category: 'student' | 'document' | 'user' | 'system'
 exports.createNotification = (userId, title, message, category = 'system', entityType = null, entityId = null) => {
+    // Deduplication check: suppress identical notifications fired within 2000ms
+    const dedupeKey = `${userId || 'all'}_${title}_${message}_${entityType || ''}_${entityId || ''}`;
+    const now = Date.now();
+    const lastCreated = _recentCreates.get(dedupeKey);
+    if (lastCreated && (now - lastCreated < 2000)) {
+        return; // Suppress duplicate call
+    }
+    _recentCreates.set(dedupeKey, now);
+
+    // Evict old cache entries periodically
+    if (_recentCreates.size > 200) {
+        for (const [k, t] of _recentCreates.entries()) {
+            if (now - t > 10000) _recentCreates.delete(k);
+        }
+    }
+
     let notifId = null;
     try {
         const result = db.prepare('INSERT INTO notifications (user_id, title, message, is_read, category, entity_type, entity_id) VALUES (?, ?, ?, 0, ?, ?, ?)')
@@ -44,6 +63,18 @@ exports.registerFcmToken = (req, res) => {
               SET user_id = excluded.user_id,
                   updated_at = excluded.updated_at
         `).run(req.user.id, token);
+
+        // Prune stale tokens: keep only the 3 most recently updated tokens for this user
+        db.prepare(`
+            DELETE FROM fcm_tokens 
+            WHERE user_id = ? AND id NOT IN (
+                SELECT id FROM fcm_tokens 
+                WHERE user_id = ? 
+                ORDER BY updated_at DESC, id DESC 
+                LIMIT 3
+            )
+        `).run(req.user.id, req.user.id);
+
         res.json({ message: 'FCM token registered' });
     } catch (error) {
         res.status(500).json({ message: 'Failed to register FCM token', error: error.message });

backend/src/services/fcmService.js

@@ -101,7 +101,10 @@ const _sendMulticast = async (tokens, title, body, category = 'system', notifica
                         priority: 'high',
                         defaultSound: true,
                         defaultVibrateTimings: true,
-                        visibility: 'public'
+                        visibility: 'public',
+                        icon: 'ic_launcher_foreground',
+                        clickAction: 'FLUTTER_NOTIFICATION_CLICK',
+                        tag: notificationId ? String(notificationId) : undefined
                     }
                 }
             });
@@ -188,9 +191,16 @@ const sendNotification = async ({ userId = null, title, body, category = 'system
                     WHERE ts.section_id = ? AND u.role = 'teacher' AND u.is_active = 1
                 `).all(entityId).map(r => r.token);
                 tokens.push(...teacherTokens);
+            } else if (!entityType) {
+                // Broadcast to all active teachers for unscoped system notifications
+                const allTeacherTokens = db.prepare(`
+                    SELECT ft.token 
+                    FROM fcm_tokens ft
+                    JOIN users u ON ft.user_id = u.id
+                    WHERE u.role = 'teacher' AND u.is_active = 1
+                `).all().map(r => r.token);
+                tokens.push(...allTeacherTokens);
             }
-            // Note: Unscoped notifications (entityType is null or not student/document/section)
-            // are delivered solely to Admins and not broadcast to teachers.
         }
 
         await _sendMulticast(tokens, title, body, category, notificationId);

frontend/android/app/src/main/AndroidManifest.xml

@@ -27,6 +27,12 @@
         <meta-data
             android:name="com.pravera.flutter_foreground_task.notification_icon"
             android:resource="@mipmap/ic_launcher" />
+        <meta-data
+            android:name="com.google.firebase.messaging.default_notification_icon"
+            android:resource="@drawable/ic_launcher_foreground" />
+        <meta-data
+            android:name="com.google.firebase.messaging.default_notification_color"
+            android:resource="@color/ic_launcher_background" />
         <meta-data
             android:name="com.google.firebase.messaging.default_notification_channel_id"
             android:value="tis_rms_activities_channel" />

frontend/android/app/src/main/kotlin/com/teamsb/tis_rms/AlarmReceiver.kt

@@ -68,8 +68,20 @@ class AlarmReceiver : BroadcastReceiver() {
         if (list.length() == 0) return
 
         val highestOldId = prefs.getInt(KEY_LAST_ID, 0)
-        var newHighestId = highestOldId
+        if (highestOldId == 0) {
+            // Seed KEY_LAST_ID on initial check to avoid spamming past notifications
+            var maxId = 0
+            for (i in 0 until list.length()) {
+                val id = list.getJSONObject(i).optInt("id", 0)
+                if (id > maxId) maxId = id
+            }
+            if (maxId > 0) {
+                prefs.edit().putInt(KEY_LAST_ID, maxId).apply()
+            }
+            return
+        }
 
+        var newHighestId = highestOldId
         ensureChannel(context)
         val notifManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
 
@@ -81,8 +93,7 @@ class AlarmReceiver : BroadcastReceiver() {
             val isReadRaw = item.opt("is_read")
             val isRead = isReadRaw == true || isReadRaw == 1
 
-            val isNew = if (highestOldId == 0) !isRead else (id > highestOldId && !isRead)
-            if (!isNew) continue
+            if (id <= highestOldId || isRead) continue
 
             val title = item.optString("title", "TIS RMS Notification")
             val message = item.optString("message", "")
@@ -97,7 +108,7 @@ class AlarmReceiver : BroadcastReceiver() {
             )
 
             val notification = Notification.Builder(context, CHANNEL_ID)
-                .setSmallIcon(R.mipmap.ic_launcher)
+                .setSmallIcon(R.drawable.ic_launcher_foreground)
                 .setContentTitle(title)
                 .setContentText(message)
                 .setAutoCancel(true)

frontend/android/app/src/main/kotlin/com/teamsb/tis_rms/MainActivity.kt

@@ -1,11 +1,32 @@
 package com.teamsb.tis_rms
 
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.content.Context
+import android.os.Build
 import android.os.Bundle
 import io.flutter.embedding.android.FlutterActivity
 
 class MainActivity : FlutterActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+        ensureNotificationChannel()
         AlarmScheduler.schedule(this)
     }
+
+    private fun ensureNotificationChannel() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            val channelId = "tis_rms_activities_channel"
+            val channelName = "Recent Activities"
+            val channelDescription = "Notifications for recent activities and system events"
+            val importance = NotificationManager.IMPORTANCE_HIGH
+            val channel = NotificationChannel(channelId, channelName, importance).apply {
+                description = channelDescription
+                enableVibration(true)
+            }
+            val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+            notificationManager.createNotificationChannel(channel)
+        }
+    }
 }
+

frontend/lib/core/services/background_sync_service.dart

@@ -46,13 +46,20 @@ void callbackDispatcher() {
         // 3. Find the last seen notification ID
         final highestOldId = prefs.getInt('last_seen_notification_id') ?? 0;
 
+        // On first run, seed last_seen_notification_id to latest ID to prevent alert storms of past items
+        if (highestOldId == 0) {
+          final ids = list.map((e) => e['id'] as int? ?? 0).toList();
+          if (ids.isNotEmpty) {
+            final newHighestId = ids.reduce(math.max);
+            await prefs.setInt('last_seen_notification_id', newHighestId);
+          }
+          return Future.value(true);
+        }
+
         // Find new unread notifications
         final newNotes = list.where((e) {
           final id = e['id'] as int? ?? 0;
           final isRead = (e['is_read'] == 1 || e['is_read'] == true);
-          if (highestOldId == 0) {
-            return !isRead;
-          }
           return id > highestOldId && !isRead;
         }).toList();
 

frontend/lib/core/services/fcm_service.dart

@@ -14,22 +14,34 @@ import 'notification_service.dart';
 Future<void> firebaseMessagingBackgroundHandler(RemoteMessage message) async {
   try {
     await Firebase.initializeApp();
-    final title = message.notification?.title ??
-        message.data['title']?.toString() ??
-        'TIS RMS';
-    final body = message.notification?.body ??
-        message.data['body']?.toString() ??
-        '';
-    int? notifId;
-    if (message.data['id'] != null && message.data['id'].toString().isNotEmpty) {
-      notifId = int.tryParse(message.data['id'].toString());
+    final notifIdStr = message.data['id']?.toString();
+    int? notifId = (notifIdStr != null && notifIdStr.isNotEmpty)
+        ? int.tryParse(notifIdStr)
+        : null;
+
+    // Advance last_seen_notification_id so AlarmReceiver and Workmanager won't duplicate it
+    if (notifId != null) {
+      try {
+        final prefs = await SharedPreferences.getInstance();
+        final currentLastId = prefs.getInt('last_seen_notification_id') ?? 0;
+        if (notifId > currentLastId) {
+          await prefs.setInt('last_seen_notification_id', notifId);
+        }
+      } catch (_) {}
     }
-    if (body.isNotEmpty) {
-      await NotificationService().showNotification(
-        id: notifId,
-        title: title,
-        body: body,
-      );
+
+    // On Android, if message.notification != null, Google Play Services has already
+    // presented the notification in the tray. Only present manually for data-only messages.
+    if (message.notification == null) {
+      final title = message.data['title']?.toString() ?? 'TIS RMS';
+      final body = message.data['body']?.toString() ?? '';
+      if (body.isNotEmpty) {
+        await NotificationService().showNotification(
+          id: notifId,
+          title: title,
+          body: body,
+        );
+      }
     }
   } catch (e) {
     debugPrint('[FcmBackground] Handler error: $e');
@@ -54,16 +66,28 @@ class FcmService {
 
       // Foreground: show local notification banner (with deduplication)
       FirebaseMessaging.onMessage.listen((RemoteMessage message) async {
+        final notifIdStr = message.data['id']?.toString();
+        int? notifId = (notifIdStr != null && notifIdStr.isNotEmpty)
+            ? int.tryParse(notifIdStr)
+            : null;
+
+        // Advance last_seen_notification_id so polling or background sync won't repeat it
+        if (notifId != null) {
+          try {
+            final prefs = await SharedPreferences.getInstance();
+            final currentLastId = prefs.getInt('last_seen_notification_id') ?? 0;
+            if (notifId > currentLastId) {
+              await prefs.setInt('last_seen_notification_id', notifId);
+            }
+          } catch (_) {}
+        }
+
         final title = message.notification?.title ??
             message.data['title']?.toString() ??
             'TIS RMS';
         final body = message.notification?.body ??
             message.data['body']?.toString() ??
             '';
-        int? notifId;
-        if (message.data['id'] != null && message.data['id'].toString().isNotEmpty) {
-          notifId = int.tryParse(message.data['id'].toString());
-        }
         if (body.isNotEmpty) {
           await NotificationService().showNotification(
             id: notifId,
@@ -72,6 +96,9 @@ class FcmService {
           );
         }
       });
+
+      // Eagerly register token with backend on startup if an active session exists
+      registerToken();
     } catch (e) {
       debugPrint('[FcmService] Init error: $e');
     }
@@ -96,13 +123,13 @@ class FcmService {
 
       final dio = Dio(BaseOptions(
         baseUrl: baseUrl,
-        connectTimeout: const Duration(seconds: 5),
-        receiveTimeout: const Duration(seconds: 5),
+        connectTimeout: const Duration(seconds: 8),
+        receiveTimeout: const Duration(seconds: 8),
         headers: {'Authorization': 'Bearer $jwtToken'},
       ));
 
       await dio.post('/notifications/fcm-token', data: {'token': token});
-      debugPrint('[FcmService] Token registered');
+      debugPrint('[FcmService] FCM token registered successfully with backend');
     } catch (e) {
       debugPrint('[FcmService] Token registration failed: $e');
     }

frontend/lib/core/services/notification_service.dart

@@ -1,5 +1,6 @@
 import 'package:flutter_local_notifications/flutter_local_notifications.dart';
-import 'package:flutter/foundation.dart' show kIsWeb;
+import 'package:flutter/foundation.dart' show kIsWeb, debugPrint;
+import 'package:shared_preferences/shared_preferences.dart';
 import 'dart:io' show Platform;
 
 class NotificationService {
@@ -55,7 +56,6 @@ class NotificationService {
                 .resolvePlatformSpecificImplementation<
                   AndroidFlutterLocalNotificationsPlugin
                 >();
-        await androidImplementation?.requestNotificationsPermission();
 
         const AndroidNotificationChannel channel = AndroidNotificationChannel(
           'tis_rms_activities_channel',
@@ -66,6 +66,10 @@ class NotificationService {
           enableVibration: true,
         );
         await androidImplementation?.createNotificationChannel(channel);
+
+        try {
+          await androidImplementation?.requestNotificationsPermission();
+        } catch (_) {}
       }
     } catch (_) {}
 
@@ -84,17 +88,32 @@ class NotificationService {
 
     if (!_initialized) await initialize();
 
-    // Deduplication check (prevents duplicate triggers from FCM + Polling + Stream)
-    final dedupeKey = '${id ?? ''}_${title.trim()}_${body.trim()}';
+    // Deduplication check: key primarily by notification ID if available, otherwise by content
+    final dedupeKey = id != null
+        ? 'id_$id'
+        : 'msg_${title.trim()}_${body.trim()}';
+
     if (_recentlyShown.contains(dedupeKey)) {
+      debugPrint('[NotificationService] Suppressed duplicate notification: $dedupeKey');
       return;
     }
     _recentlyShown.add(dedupeKey);
-    // Evict after 15 seconds
-    Future.delayed(const Duration(seconds: 15), () {
+    // Evict after 60 seconds (covers rapid polling cycles and AlarmManager checks)
+    Future.delayed(const Duration(seconds: 60), () {
       _recentlyShown.remove(dedupeKey);
     });
 
+    // Advance last_seen_notification_id in SharedPreferences
+    if (id != null) {
+      try {
+        final prefs = await SharedPreferences.getInstance();
+        final current = prefs.getInt('last_seen_notification_id') ?? 0;
+        if (id > current) {
+          await prefs.setInt('last_seen_notification_id', id);
+        }
+      } catch (_) {}
+    }
+
     const AndroidNotificationDetails androidPlatformChannelSpecifics =
         AndroidNotificationDetails(
           'tis_rms_activities_channel', // id