[Identifier] Implement string extension

lib/famedlysdk.dart

@@ -29,6 +29,7 @@ export 'package:famedlysdk/src/sync/user_update.dart';
 export 'package:famedlysdk/src/utils/device_keys_list.dart';
 export 'package:famedlysdk/src/utils/matrix_exception.dart';
 export 'package:famedlysdk/src/utils/matrix_file.dart';
+export 'package:famedlysdk/src/utils/matrix_id_string_extension.dart';
 export 'package:famedlysdk/src/utils/mx_content.dart';
 export 'package:famedlysdk/src/utils/open_id_credentials.dart';
 export 'package:famedlysdk/src/utils/profile.dart';

lib/src/client.dart

@@ -421,7 +421,7 @@ class Client {
   Future<List<User>> loadFamedlyContacts() async {
     List<User> contacts = [];
     Room contactDiscoveryRoom =
-        this.getRoomByAlias("#famedlyContactDiscovery:${userID.split(":")[1]}");
+        this.getRoomByAlias("#famedlyContactDiscovery:${userID.domain}");
     if (contactDiscoveryRoom != null) {
       contacts = await contactDiscoveryRoom.requestParticipants();
     } else {

lib/src/room.dart

@@ -213,7 +213,7 @@ class Room {
     if (canonicalAlias != null &&
         canonicalAlias.isNotEmpty &&
         canonicalAlias.length > 3) {
-      return canonicalAlias.substring(1, canonicalAlias.length).split(":")[0];
+      return canonicalAlias.localpart;
     }
     List<String> heroes = [];
     if (mHeroes != null &&

lib/src/user.dart

@@ -103,9 +103,7 @@ class User extends Event {
   /// Returns the displayname or the local part of the Matrix ID if the user
   /// has no displayname.
   String calcDisplayname() => (displayName == null || displayName.isEmpty)
-      ? (stateKey != null
-          ? stateKey.replaceFirst("@", "").split(":")[0]
-          : "Unknown User")
+      ? (stateKey != null ? stateKey.localpart : "Unknown User")
       : displayName;
 
   /// Call the Matrix API to kick this user from this room.

lib/src/utils/matrix_id_string_extension.dart

@@ -0,0 +1,26 @@
+extension MatrixIdExtension on String {
+  static const Set<String> VALID_SIGILS = {"@", "!", "#", "\$", "+"};
+
+  static const int MAX_LENGTH = 255;
+
+  bool get isValidMatrixId {
+    if (this.length > MAX_LENGTH) return false;
+    if (!VALID_SIGILS.contains(this.substring(0, 1))) {
+      return false;
+    }
+    final List<String> parts = this.substring(1).split(":");
+    if (parts.length != 2 || parts[0].isEmpty || parts[1].isEmpty) {
+      return false;
+    }
+    return true;
+  }
+
+  String get sigil => isValidMatrixId ? this.substring(0, 1) : null;
+
+  String get localpart =>
+      isValidMatrixId ? this.substring(1).split(":").first : null;
+
+  String get domain => isValidMatrixId ? this.substring(1).split(":")[1] : null;
+
+  bool equals(String other) => this.toLowerCase() == other.toLowerCase();
+}

test/matrix_id_string_extension_test.dart

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2019 Zender & Kurtz GbR.
+ *
+ * Authors:
+ *   Christian Pauly <krille@famedly.com>
+ *   Marcel Radzio <mtrnord@famedly.com>
+ *
+ * This file is part of famedlysdk.
+ *
+ * famedlysdk is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * famedlysdk is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with famedlysdk.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import 'package:test/test.dart';
+import 'package:famedlysdk/src/utils/matrix_id_string_extension.dart';
+
+void main() {
+  /// All Tests related to the ChatTime
+  group("Matrix ID String Extension", () {
+    test("Matrix ID String Extension", () async {
+      final String mxId = "@test:example.com";
+      expect(mxId.isValidMatrixId, true);
+      expect("#test:example.com".isValidMatrixId, true);
+      expect("!test:example.com".isValidMatrixId, true);
+      expect("+test:example.com".isValidMatrixId, true);
+      expect("\$test:example.com".isValidMatrixId, true);
+      expect("test:example.com".isValidMatrixId, false);
+      expect("@testexample.com".isValidMatrixId, false);
+      expect("@:example.com".isValidMatrixId, false);
+      expect("@test:".isValidMatrixId, false);
+      expect(mxId.sigil, "@");
+      expect("#test:example.com".sigil, "#");
+      expect("!test:example.com".sigil, "!");
+      expect("+test:example.com".sigil, "+");
+      expect("\$test:example.com".sigil, "\$");
+      expect(mxId.localpart, "test");
+      expect(mxId.domain, "example.com");
+    });
+  });
+}