feat: Add support for generic map validator (#99)

* feat(luthor): Add map validator

* feat(luthor_generator): Add support for map validator

* test(luthor): Add tests for map validator

packages/luthor/lib/src/validations/map_validation.dart

@@ -0,0 +1,22 @@
+import 'package:luthor/src/validation.dart';
+
+class MapValidation extends Validation {
+  String? customMessage;
+
+  MapValidation({
+    String? message,
+  }) : customMessage = message;
+
+  @override
+  bool call(String? fieldName, Object? value) {
+    super.call(fieldName, value);
+    return value is Map?;
+  }
+
+  @override
+  String get message =>
+      customMessage ?? '${fieldName ?? 'value'} must be a Map';
+
+  @override
+  Map<String, List<String>>? get errors => null;
+}

packages/luthor/lib/src/validator.dart

@@ -6,6 +6,7 @@ import 'package:luthor/src/validations/custom_validation.dart';
 import 'package:luthor/src/validations/double_validation.dart';
 import 'package:luthor/src/validations/int_validation.dart';
 import 'package:luthor/src/validations/list_validation.dart';
+import 'package:luthor/src/validations/map_validation.dart';
 import 'package:luthor/src/validations/null_validation.dart';
 import 'package:luthor/src/validations/number_validation.dart';
 import 'package:luthor/src/validations/required_validation.dart';
@@ -96,6 +97,12 @@ class Validator {
     return this;
   }
 
+  /// Validates that the value is a map.
+  Validator map({String? message}) {
+    validations.add(MapValidation(message: message));
+    return this;
+  }
+
   /// Validates that the value matches the given schema.
   Validator schema(Map<String, Validator> validatorSchema) {
     validations.add(SchemaValidation(validatorSchema));

packages/luthor/test/validations/map_validation_test.dart

@@ -0,0 +1,48 @@
+import 'package:luthor/luthor.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('should return true when value is a map', () {
+    final result = l.map().validateValue({});
+
+    switch (result) {
+      case SingleValidationSuccess(data: _):
+        expect(result.data, {});
+      case SingleValidationError(data: _, errors: _):
+        fail('should not have errors');
+    }
+  });
+
+  test('should return false when value is not a map', () {
+    final result = l.map().validateValue('a');
+
+    switch (result) {
+      case SingleValidationSuccess(data: _):
+        fail('should not be a success');
+      case SingleValidationError(data: _, errors: final errors):
+        expect(errors, ['value must be a Map']);
+    }
+  });
+
+  test('should return true when value is null', () {
+    final result = l.map().validateValue(null);
+
+    switch (result) {
+      case SingleValidationSuccess(data: _):
+        expect(result.data, isNull);
+      case SingleValidationError(data: _, errors: _):
+        fail('should not have errors');
+    }
+  });
+
+  test('should return false if the value is null with required()', () {
+    final result = l.required().map().validateValue(null);
+
+    switch (result) {
+      case SingleValidationSuccess(data: _):
+        fail('should not be a success');
+      case SingleValidationError(data: _, errors: final errors):
+        expect(errors, ['value is required']);
+    }
+  });
+}

packages/luthor_generator/lib/helpers/validations/base_validations.dart

@@ -38,6 +38,10 @@ String getValidations(ParameterElement param) {
     _writeListValidations(buffer, param);
   }
 
+  if (param.type.isDartCoreMap) {
+    buffer.write('l.map()');
+  }
+
   if (param.type.isDartCoreNull) {
     buffer.write('l.nullValue()');
   }