fix: multiple notifications on android app #5367

src/app/features/android/android-notification-id.util.spec.ts

@@ -0,0 +1,79 @@
+import { generateNotificationId } from './android-notification-id.util';
+
+describe('generateNotificationId', () => {
+  it('should generate the same ID for the same input', () => {
+    const reminderId = 'test-reminder-id-123';
+    const id1 = generateNotificationId(reminderId);
+    const id2 = generateNotificationId(reminderId);
+
+    expect(id1).toBe(id2);
+  });
+
+  it('should generate different IDs for different inputs', () => {
+    const id1 = generateNotificationId('reminder-abc-123');
+    const id2 = generateNotificationId('reminder-xyz-456');
+
+    expect(id1).not.toBe(id2);
+  });
+
+  it('should always return a positive integer', () => {
+    const testIds = [
+      'short',
+      'a-very-long-reminder-id-with-many-characters-123456789',
+      'special-chars-!@#$%',
+      'nanoid-V1StGXR8_Z5jdHi6B-myT',
+    ];
+
+    testIds.forEach((reminderId) => {
+      const id = generateNotificationId(reminderId);
+      expect(id).toBeGreaterThan(0);
+      expect(Number.isInteger(id)).toBe(true);
+    });
+  });
+
+  it('should return ID within safe Android range', () => {
+    const testIds = [
+      'test-1',
+      'test-2',
+      'very-long-id-that-might-cause-overflow-123456789',
+    ];
+
+    testIds.forEach((reminderId) => {
+      const id = generateNotificationId(reminderId);
+      expect(id).toBeLessThan(2147483647); // Max 32-bit signed integer
+      expect(id).toBeGreaterThan(0);
+    });
+  });
+
+  it('should throw error for invalid input', () => {
+    expect(() => generateNotificationId('')).toThrow();
+    expect(() => generateNotificationId(null as any)).toThrow();
+    expect(() => generateNotificationId(undefined as any)).toThrow();
+    expect(() => generateNotificationId(123 as any)).toThrow();
+  });
+
+  it('should handle typical nanoid format', () => {
+    // Typical nanoid format used in the app
+    const nanoidExamples = [
+      'V1StGXR8_Z5jdHi6B-myT',
+      'xQY6fK9kL3mN5pR2sT7vW',
+      'aB1cD2eF3gH4iJ5kL6mN7',
+    ];
+
+    nanoidExamples.forEach((reminderId) => {
+      const id = generateNotificationId(reminderId);
+      expect(id).toBeGreaterThan(0);
+      expect(Number.isInteger(id)).toBe(true);
+    });
+  });
+
+  it('should be deterministic across multiple calls', () => {
+    const reminderId = 'consistent-test-id';
+    const ids = Array.from({ length: 100 }, () => generateNotificationId(reminderId));
+    const firstId = ids[0];
+
+    ids.forEach((id) => {
+      expect(id).toBe(firstId);
+    });
+  });
+});

src/app/features/android/android-notification-id.util.ts

@@ -0,0 +1,24 @@
+/**
+ * Generates a deterministic numeric notification ID from a string reminder ID.
+ * This ensures the same reminder always gets the same notification ID,
+ * preventing duplicate notifications on Android.
+ *
+ * @param reminderId - The reminder's relatedId (task/note ID)
+ * @returns A positive integer suitable for Android notification ID
+ */
+export const generateNotificationId = (reminderId: string): number => {
+  if (!reminderId || typeof reminderId !== 'string') {
+    throw new Error('Invalid reminderId: must be a non-empty string');
+  }
+
+  // Simple hash function to convert string to positive integer
+  let hash = 0;
+  for (let i = 0; i < reminderId.length; i++) {
+    const char = reminderId.charCodeAt(i);
+    hash = (hash << 5) - hash + char;
+    hash = hash & hash; // Convert to 32-bit integer
+  }
+
+  // Ensure positive integer and within safe range for Android
+  return Math.abs(hash) % 2147483647;
+};

src/app/features/android/store/android.effects.ts

@@ -9,6 +9,7 @@ import { SnackService } from '../../../core/snack/snack.service';
 import { IS_ANDROID_WEB_VIEW } from '../../../util/is-android-web-view';
 import { LocalNotificationSchema } from '@capacitor/local-notifications/dist/esm/definitions';
 import { DroidLog } from '../../../core/log';
+import { generateNotificationId } from '../android-notification-id.util';
 
 // TODO send message to electron when current task changes here
 
@@ -93,8 +94,8 @@ export class AndroidEffects {
               // Re-schedule the full set so the native alarm manager is always in sync.
               await LocalNotifications.schedule({
                 notifications: reminders.map((reminder) => {
-                  // since the ids are temporary we can use just Math.random()
-                  const id = Math.round(Math.random() * 10000000);
+                  // Use deterministic ID based on reminder's relatedId to prevent duplicate notifications
+                  const id = generateNotificationId(reminder.relatedId);
                   const now = Date.now();
                   const scheduleAt =
                     reminder.remindAt <= now ? now + 1000 : reminder.remindAt; // push overdue reminders into the immediate future