refactor(mobile): assert lists are sorted for diffing

mobile/lib/services/sync.service.dart

@@ -138,7 +138,6 @@ class SyncService {
   Future<bool> _syncUsersFromServer(List<User> users) async {
     users.sortBy((u) => u.id);
     final dbUsers = await _userRepository.getAll(sortBy: UserSort.id);
-    assert(dbUsers.isSortedBy((u) => u.id), "dbUsers not sorted!");
     final List<int> toDelete = [];
     final List<User> toUpsert = [];
     final changes = diffSortedListsSync(
@@ -322,8 +321,6 @@ class SyncService {
       ownerId: isShared ? null : me.isarId,
       sortBy: AlbumSort.remoteId,
     );
-    assert(dbAlbums.isSortedBy((e) => e.remoteId!), "dbAlbums not sorted!");
-
     final List<Asset> toDelete = [];
     final List<Asset> existing = [];
 
@@ -512,7 +509,6 @@ class SyncService {
         await _albumRepository.getAll(remote: false, sortBy: AlbumSort.localId);
     final List<Asset> deleteCandidates = [];
     final List<Asset> existing = [];
-    assert(inDb.isSorted((a, b) => a.localId!.compareTo(b.localId!)), "sort!");
     final bool anyChanges = await diffSortedLists(
       onDevice,
       inDb,

mobile/lib/utils/diff.dart

@@ -1,16 +1,20 @@
 import 'dart:async';
 
+import 'package:collection/collection.dart';
+
 /// Efficiently compares two sorted lists in O(n), calling the given callback
 /// for each item.
 /// Return `true` if there are any differences found, else `false`
-Future<bool> diffSortedLists<A, B>(
-  List<A> la,
-  List<B> lb, {
-  required int Function(A a, B b) compare,
-  required FutureOr<bool> Function(A a, B b) both,
-  required FutureOr<void> Function(A a) onlyFirst,
-  required FutureOr<void> Function(B b) onlySecond,
+Future<bool> diffSortedLists<T>(
+  List<T> la,
+  List<T> lb, {
+  required int Function(T a, T b) compare,
+  required FutureOr<bool> Function(T a, T b) both,
+  required FutureOr<void> Function(T a) onlyFirst,
+  required FutureOr<void> Function(T b) onlySecond,
 }) async {
+  assert(la.isSorted(compare), "first argument must be sorted");
+  assert(lb.isSorted(compare), "second argument must be sorted");
   bool diff = false;
   int i = 0, j = 0;
   for (; i < la.length && j < lb.length;) {
@@ -38,14 +42,16 @@ Future<bool> diffSortedLists<A, B>(
 /// Efficiently compares two sorted lists in O(n), calling the given callback
 /// for each item.
 /// Return `true` if there are any differences found, else `false`
-bool diffSortedListsSync<A, B>(
-  List<A> la,
-  List<B> lb, {
-  required int Function(A a, B b) compare,
-  required bool Function(A a, B b) both,
-  required void Function(A a) onlyFirst,
-  required void Function(B b) onlySecond,
+bool diffSortedListsSync<T>(
+  List<T> la,
+  List<T> lb, {
+  required int Function(T a, T b) compare,
+  required bool Function(T a, T b) both,
+  required void Function(T a) onlyFirst,
+  required void Function(T b) onlySecond,
 }) {
+  assert(la.isSorted(compare), "first argument must be sorted");
+  assert(lb.isSorted(compare), "second argument must be sorted");
   bool diff = false;
   int i = 0, j = 0;
   for (; i < la.length && j < lb.length;) {