Map.contains

main.dart

import 'package:collection/collection.dart';

extension ListExtension<E> on List<E> {
  /// Checks whether every element of this iterable satisfies [test] while
  /// passing the element and the index to [test].
  bool everyIndexed(bool Function(int index, E element) test) {
    for (var i = 0; i < length; i++) {
      final element = this[i];
      if (!test(i, element)) return false;
    }
    return true;
  }
}

typedef Json = Map<String, dynamic>;

extension JsonContains on Json {
  /// Checks if the current JSON map contains [other]. By default, this will
  /// skip undefined keys that are not present in the current JSON map. If
  /// [skipUndefinedKeys] is `false`, this will return false if there are
  /// undefined keys present in [other] that is not present in the current
  /// JSON map.
  ///
  /// ```dart
  /// final a = {'a': 1, 'b': 2, 'c': 3};
  /// final b = {'a': 1, 'b': 2, 'd': 4};
  ///
  /// print(a.contains(b)); // returns true
  /// print(a.contains(b, skipUndefinedKeys: false)); // returns false
  /// ```
  bool contains(
    Json other, {
    bool skipUndefinedKeys = true,
  }) {
    return other.entries.every((entry) {
      if (!containsKey(entry.key)) {
        return skipUndefinedKeys;
      }

      final thisValue = this[entry.key];
      final otherValue = entry.value;

      if (thisValue is List &&
          otherValue is List &&
          thisValue.firstOrNull is Map &&
          otherValue.firstOrNull is Map) {
        return thisValue.everyIndexed((index, _) {
          final ithValue = thisValue[index] as Json;
          final ithOtherValue = otherValue[index] as Json;

          return ithValue.contains(
            ithOtherValue,
            skipUndefinedKeys: skipUndefinedKeys,
          );
        });
      }

      if (thisValue is Map && otherValue is Map) {
        return (thisValue as Json).contains(otherValue as Json);
      }

      return const DeepCollectionEquality().equals(thisValue, otherValue);
    });
  }
}

void main() {
  final a = {'a': 1, 'b': 2, 'c': 3};
  final b = {'a': 1, 'b': 2, 'd': 4};
  
  print(a.contains(b)); // returns true
  print(a.contains(b, skipUndefinedKeys: false)); // returns false
}