notif: Delete older channels

Author: rajveermalviya

lib/notifications/display.dart

@@ -53,8 +53,31 @@ class NotificationChannelManager {
   //    in android/app/src/main/java/com/zulipmobile/notifications/NotificationChannelManager.kt .
   static Future<void> _ensureChannel() async {
     final plugin = ZulipBinding.instance.notifications;
-    await plugin.resolvePlatformSpecificImplementation<AndroidFlutterLocalNotificationsPlugin>()
-      ?.createNotificationChannel(AndroidNotificationChannel(
+    final androidPlugin = plugin.resolvePlatformSpecificImplementation<AndroidFlutterLocalNotificationsPlugin>();
+    if (androidPlugin == null) {
+      // TODO(log)
+      return;
+    }
+
+    // Delete any older channels.
+    var found = false;
+    final channels = await androidPlugin.getNotificationChannels();
+    if (channels != null) {
+      for (final channel in channels) {
+        if (channel.id == kChannelId) {
+          found = true;
+        } else {
+          await androidPlugin.deleteNotificationChannel(channel.id);
+        }
+      }
+    }
+    if (found) {
+      // The channel already exists, nothing to do.
+      return;
+    }
+
+    // The channel doesn't exists, create it.
+    await androidPlugin.createNotificationChannel(AndroidNotificationChannel(
         kChannelId,
         'Messages', // TODO(i18n)
         importance: Importance.high,

test/model/binding.dart

@@ -475,6 +475,18 @@ class FakeAndroidFlutterLocalNotificationsPlugin extends Fake implements Android
   Future<void> createNotificationChannel(AndroidNotificationChannel notificationChannel) async {
     _createdChannels.add(notificationChannel);
   }
+
+  @override
+  Future<List<AndroidNotificationChannel>?> getNotificationChannels() async {
+    return _createdChannels;
+  }
+
+  @override
+  Future<void> deleteNotificationChannel(String channelId) async {
+    _createdChannels.removeWhere((channel) {
+      return channel.id == channelId;
+    });
+  }
 }
 
 class FakeIOSFlutterLocalNotificationsPlugin extends Fake implements IOSFlutterLocalNotificationsPlugin {