internal_links: Add variable realmUrlWithSlash to add '/'

Updates the URL construction to include a trailing slash
before the fragment identifier. This ensures that the URL
is properly formatted and makes the url linkified.

Fixes: #845

Author: satyam372

lib/model/internal_link.dart

@@ -96,7 +96,11 @@ Uri narrowLink(PerAccountStore store, Narrow narrow, {int? nearMessageId}) {
     fragment.write('/near/$nearMessageId');
   }
 
-  return store.realmUrl.replace(fragment: fragment.toString());
+  final realmUrlWithSlash = store.realmUrl.path.endsWith('/')
+      ? store.realmUrl
+      : store.realmUrl.replace(path: '${store.realmUrl.path}/');
+
+  return realmUrlWithSlash.replace(fragment: fragment.toString());
 }
 
 /// A [Narrow] from a given URL, on `store`'s realm.

test/widgets/action_sheet_test.dart

@@ -38,11 +38,12 @@ late FakeApiConnection connection;
 Future<void> setupToMessageActionSheet(WidgetTester tester, {
   required Message message,
   required Narrow narrow,
+  Account? account,
 }) async {
   addTearDown(testBinding.reset);
-
-  await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());
-  final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
+  final effectiveAccount = account ?? eg.selfAccount;
+  await testBinding.globalStore.add(effectiveAccount, eg.initialSnapshot());
+  final store = await testBinding.globalStore.perAccount(effectiveAccount.id);
   await store.addUser(eg.user(userId: message.senderId));
   if (message is StreamMessage) {
     final stream = eg.stream(streamId: message.streamId);
@@ -551,6 +552,26 @@ void main() {
       final expectedLink = narrowLink(store, narrow, nearMessageId: message.id).toString();
       check(await Clipboard.getData('text/plain')).isNotNull().text.equals(expectedLink);
     });
+
+    testWidgets('Full Url Testing', (tester) async {
+      final message = eg.streamMessage();
+      final narrow = TopicNarrow.ofMessage(message);
+      await setupToMessageActionSheet(tester, message: message, narrow: narrow);
+      final store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
+
+      await tapCopyMessageLinkButton(tester);
+      await tester.pump(Duration.zero);
+      final expectedLink = narrowLink(store, narrow, nearMessageId: message.id).toString();
+
+      final customAccount = eg.selfAccount.copyWith(id: 2,realmUrl: Uri.parse('https://chat.example'));
+      await setupToMessageActionSheet(tester, message: message, narrow: narrow, account: customAccount);
+      final customAccountStore = await testBinding.globalStore.perAccount(customAccount.id);
+
+      await tapCopyMessageLinkButton(tester);
+      await tester.pump(Duration.zero);
+      final generatedLink = narrowLink(customAccountStore, narrow, nearMessageId: message.id).toString();
+      check(expectedLink).equals(generatedLink);
+    });
   });
 
   group('ShareButton', () {