feat(leaderboard_repository): enable ability to check if initials are allowed (#226)

* feat(leaderboard_repository): enable ability to check if a username is allowed

* chore: addressed review feedback

* chore: addressed review feedback

packages/leaderboard_repository/lib/src/leaderboard_repository.dart

@@ -72,6 +72,20 @@ class FetchPlayerRankingException extends LeaderboardException {
         );
 }
 
+/// {@template fetch_prohibited_initials_exception}
+/// Exception thrown when failure occurs while fetching prohibited initials.
+/// {@endtemplate}
+class FetchProhibitedInitialsException extends LeaderboardException {
+  /// {@macro fetch_prohibited_initials_exception}
+  const FetchProhibitedInitialsException(
+    Object error,
+    StackTrace stackTrace,
+  ) : super(
+          error,
+          stackTrace,
+        );
+}
+
 /// {@template leaderboard_repository}
 /// Repository to access leaderboard data in Firebase Cloud Firestore.
 /// {@endtemplate}
@@ -152,4 +166,25 @@ class LeaderboardRepository {
       throw FetchPlayerRankingException(error, stackTrace);
     }
   }
+
+  /// Determines if the given [initials] are allowed.
+  Future<bool> areInitialsAllowed({required String initials}) async {
+    // Initials can only be three uppercase A-Z letters
+    final initialsRegex = RegExp(r'^[A-Z]{3}$');
+    if (!initialsRegex.hasMatch(initials)) {
+      return false;
+    }
+
+    try {
+      final document = await _firebaseFirestore
+          .collection('prohibitedInitials')
+          .doc('list')
+          .get();
+      final prohibitedInitials =
+          document.get('prohibitedInitials') as List<String>;
+      return !prohibitedInitials.contains(initials);
+    } on Exception catch (error, stackTrace) {
+      throw FetchProhibitedInitialsException(error, stackTrace);
+    }
+  }
 }

packages/leaderboard_repository/test/src/leaderboard_repository_test.dart

@@ -21,6 +21,9 @@ class MockQueryDocumentSnapshot extends Mock
 class MockDocumentReference extends Mock
     implements DocumentReference<Map<String, dynamic>> {}
 
+class MockDocumentSnapshot extends Mock
+    implements DocumentSnapshot<Map<String, dynamic>> {}
+
 void main() {
   group('LeaderboardRepository', () {
     late FirebaseFirestore firestore;
@@ -223,5 +226,94 @@ void main() {
         );
       });
     });
+
+    group('areInitialsAllowed', () {
+      late LeaderboardRepository leaderboardRepository;
+      late CollectionReference<Map<String, dynamic>> collectionReference;
+      late DocumentReference<Map<String, dynamic>> documentReference;
+      late DocumentSnapshot<Map<String, dynamic>> documentSnapshot;
+
+      setUp(() async {
+        collectionReference = MockCollectionReference();
+        documentReference = MockDocumentReference();
+        documentSnapshot = MockDocumentSnapshot();
+        leaderboardRepository = LeaderboardRepository(firestore);
+
+        when(() => firestore.collection('prohibitedInitials'))
+            .thenReturn(collectionReference);
+        when(() => collectionReference.doc('list'))
+            .thenReturn(documentReference);
+        when(() => documentReference.get())
+            .thenAnswer((_) async => documentSnapshot);
+        when<dynamic>(() => documentSnapshot.get('prohibitedInitials'))
+            .thenReturn(['BAD']);
+      });
+
+      test('returns true if initials are three letters and allowed', () async {
+        final isUsernameAllowedResponse =
+            await leaderboardRepository.areInitialsAllowed(
+          initials: 'ABC',
+        );
+        expect(
+          isUsernameAllowedResponse,
+          isTrue,
+        );
+      });
+
+      test(
+        'returns false if initials are shorter than 3 characters',
+        () async {
+          final areInitialsAllowedResponse =
+              await leaderboardRepository.areInitialsAllowed(initials: 'AB');
+          expect(areInitialsAllowedResponse, isFalse);
+        },
+      );
+
+      test(
+        'returns false if initials are longer than 3 characters',
+        () async {
+          final areInitialsAllowedResponse =
+              await leaderboardRepository.areInitialsAllowed(initials: 'ABCD');
+          expect(areInitialsAllowedResponse, isFalse);
+        },
+      );
+
+      test(
+        'returns false if initials contain a lowercase letter',
+        () async {
+          final areInitialsAllowedResponse =
+              await leaderboardRepository.areInitialsAllowed(initials: 'AbC');
+          expect(areInitialsAllowedResponse, isFalse);
+        },
+      );
+
+      test(
+        'returns false if initials contain a special character',
+        () async {
+          final areInitialsAllowedResponse =
+              await leaderboardRepository.areInitialsAllowed(initials: 'A@C');
+          expect(areInitialsAllowedResponse, isFalse);
+        },
+      );
+
+      test('returns false if initials are forbidden', () async {
+        final areInitialsAllowedResponse =
+            await leaderboardRepository.areInitialsAllowed(initials: 'BAD');
+        expect(areInitialsAllowedResponse, isFalse);
+      });
+
+      test(
+        'throws FetchProhibitedInitialsException when Exception occurs '
+        'when trying to retrieve information from firestore',
+        () async {
+          when(() => firestore.collection('prohibitedInitials'))
+              .thenThrow(Exception('oops'));
+          expect(
+            () => leaderboardRepository.areInitialsAllowed(initials: 'ABC'),
+            throwsA(isA<FetchProhibitedInitialsException>()),
+          );
+        },
+      );
+    });
   });
 }