Source Code added

mobile/lib/utils/diff.dart

@@ -0,0 +1,91 @@
+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<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;) {
+    final int order = compare(la[i], lb[j]);
+    if (order == 0) {
+      diff |= await both(la[i++], lb[j++]);
+    } else if (order < 0) {
+      await onlyFirst(la[i++]);
+      diff = true;
+    } else if (order > 0) {
+      await onlySecond(lb[j++]);
+      diff = true;
+    }
+  }
+  diff |= i < la.length || j < lb.length;
+  for (; i < la.length; i++) {
+    await onlyFirst(la[i]);
+  }
+  for (; j < lb.length; j++) {
+    await onlySecond(lb[j]);
+  }
+  return diff;
+}
+
+/// 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<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;) {
+    final int order = compare(la[i], lb[j]);
+    if (order == 0) {
+      diff |= both(la[i++], lb[j++]);
+    } else if (order < 0) {
+      onlyFirst(la[i++]);
+      diff = true;
+    } else if (order > 0) {
+      onlySecond(lb[j++]);
+      diff = true;
+    }
+  }
+  diff |= i < la.length || j < lb.length;
+  for (; i < la.length; i++) {
+    onlyFirst(la[i]);
+  }
+  for (; j < lb.length; j++) {
+    onlySecond(lb[j]);
+  }
+  return diff;
+}
+
+int compareToNullable<T extends Comparable>(T? a, T? b) {
+  if (a == null && b == null) {
+    return 0;
+  }
+
+  if (a == null) {
+    return 1;
+  }
+  if (b == null) {
+    return -1;
+  }
+  return a.compareTo(b);
+}