implement isBefore validator

Author: ArturAssisComp

lib/new_api_prototype/datetime_validators.dart

@@ -5,7 +5,7 @@ String tmpIsAfterErrorMsg(DateTime reference) =>
 
 /// This function returns a validator that checks if the user [DateTime] input is
 /// after (or equal, if `inclusive` is true) to `reference`. If the checking results
-/// true, the validators returns `null`. Otherwise, it returns `isAfterMsg`, if
+/// true, the validator returns `null`. Otherwise, it returns `isAfterMsg`, if
 /// provided, or `FormBuilderLocalizations.current.isAfterErrorText`.
 Validator<DateTime> isAfter(
   DateTime reference, {
@@ -19,3 +19,24 @@ Validator<DateTime> isAfter(
         : isAfterMsg?.call(reference) ?? tmpIsAfterErrorMsg(reference);
   };
 }
+
+String tmpIsBeforeErrorMsg(DateTime reference) {
+  return 'The date must be before ${reference.toLocal()}';
+}
+
+/// This function returns a validator that checks if the user [DateTime] input is
+/// before (or equal, if `inclusive` is true) to `reference`. If the checking results
+/// true, the validator returns `null`. Otherwise, it returns `isBeforeMsg`, if
+/// provided, or `FormBuilderLocalizations.current.isBeforeErrorText`.
+Validator<DateTime> isBefore(
+  DateTime reference, {
+  String Function(DateTime)? isBeforeMsg,
+  bool inclusive = false,
+}) {
+  return (DateTime value) {
+    return value.isBefore(reference) ||
+            (inclusive ? value.isAtSameMomentAs(reference) : false)
+        ? null
+        : isBeforeMsg?.call(reference) ?? tmpIsBeforeErrorMsg(reference);
+  };
+}

test/new_api_testing/datetime_validators/is_before_validator_test.dart

@@ -0,0 +1,111 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:form_builder_validators/new_api_prototype/constants.dart';
+import 'package:form_builder_validators/new_api_prototype/datetime_validators.dart';
+
+void main() {
+  group('Validator: isBefore', () {
+    test('Validation for the year 1994', () {
+      final DateTime reference = DateTime(1994);
+      final DateTime eq = reference.copyWith();
+      final DateTime after10Years = DateTime(2004);
+      final DateTime after1Ms = reference.add(const Duration(milliseconds: 1));
+      final DateTime before1Year = DateTime(1993);
+      final DateTime before1Sec =
+          reference.subtract(const Duration(seconds: 1));
+      final Validator<DateTime> v = isBefore(reference);
+      final String errorMsg = tmpIsBeforeErrorMsg(reference);
+
+      expect(
+        v(eq),
+        errorMsg,
+        reason: 'Should return error against 1994',
+      );
+      expect(
+        v(after10Years),
+        errorMsg,
+        reason: 'Should return error against 2004',
+      );
+      expect(
+        v(after1Ms),
+        errorMsg,
+        reason: 'Should return error against 1994 + 1ms',
+      );
+      expect(
+        v(before1Year),
+        isNull,
+        reason: 'Should return null against 1993',
+      );
+      expect(
+        v(before1Sec),
+        isNull,
+        reason: 'Should return null against 1994 - 1s',
+      );
+    });
+    test(
+        'Inclusive validation for datetime 2089, month 3, day 23, h 3, min 46, s 12, 233 ms',
+        () {
+      final DateTime reference = DateTime(2089, 3, 23, 3, 46, 12, 233);
+      final DateTime eq = reference.copyWith();
+      final DateTime after10Years = reference.copyWith(year: 2099);
+      final DateTime after1Ms = reference.add(const Duration(milliseconds: 1));
+      final DateTime before1Year = reference.copyWith(year: 2088);
+      final DateTime before1Sec =
+          reference.subtract(const Duration(seconds: 1));
+      final Validator<DateTime> v = isBefore(reference, inclusive: true);
+      final String errorMsg = tmpIsBeforeErrorMsg(reference);
+
+      expect(
+        v(eq),
+        isNull,
+        reason: 'Should return null against the same datetime',
+      );
+      expect(
+        v(after10Years),
+        errorMsg,
+        reason: 'Should return error against the reference shifted +10 years',
+      );
+      expect(
+        v(after1Ms),
+        errorMsg,
+        reason: 'Should return error against the reference shifted +1 ms',
+      );
+      expect(
+        v(before1Year),
+        isNull,
+        reason:
+            'Should return null against a datetime 1 year before the reference',
+      );
+      expect(
+        v(before1Sec),
+        isNull,
+        reason:
+            'Should return null against a datetime 1 sec before the reference',
+      );
+    });
+
+    test('Should return a custom message after validating', () {
+      const String errorMsg = 'error msg';
+      final DateTime reference = DateTime(2);
+      final Validator<DateTime> v =
+          isBefore(reference, isBeforeMsg: (_) => errorMsg);
+
+      expect(
+        v(reference.copyWith()),
+        errorMsg,
+        reason:
+            'Should return custom message when input is equal to the reference',
+      );
+      expect(
+        v(reference.subtract(const Duration(microseconds: 1))),
+        isNull,
+        reason: 'Should return null when input is before the reference',
+      );
+      expect(
+        v(reference.add(const Duration(days: 1))),
+        errorMsg,
+        reason:
+            'Should return custom message when the input is after the reference',
+      );
+    });
+  });
+}