Even more link handling!

lib/feed/utils/utils.dart

@@ -9,6 +9,7 @@ import 'package:thunder/community/bloc/community_bloc.dart';
 import 'package:thunder/core/auth/bloc/auth_bloc.dart';
 import 'package:thunder/feed/feed.dart';
 import 'package:thunder/instance/bloc/instance_bloc.dart';
+import 'package:thunder/shared/pages/loading_page.dart';
 import 'package:thunder/shared/sort_picker.dart';
 import 'package:thunder/community/widgets/community_drawer.dart';
 import 'package:thunder/thunder/bloc/thunder_bloc.dart';
@@ -96,34 +97,39 @@ Future<void> navigateToFeedPage(
         );
   }
 
-  Navigator.of(context).push(
-    SwipeablePageRoute(
-      transitionDuration: reduceAnimations ? const Duration(milliseconds: 100) : null,
-      backGestureDetectionWidth: 45,
-      canOnlySwipeFromEdge: disableFullPageSwipe(isUserLoggedIn: authBloc.state.isLoggedIn, state: thunderBloc.state, isFeedPage: true) || !thunderState.enableFullScreenSwipeNavigationGesture,
-      builder: (context) => MultiBlocProvider(
-        providers: [
-          BlocProvider.value(value: accountBloc),
-          BlocProvider.value(value: authBloc),
-          BlocProvider.value(value: thunderBloc),
-          BlocProvider.value(value: instanceBloc),
-          BlocProvider.value(value: anonymousSubscriptionsBloc),
-          BlocProvider.value(value: communityBloc),
-        ],
-        child: Material(
-          child: FeedPage(
-            feedType: feedType,
-            sortType: sortType ?? thunderBloc.state.defaultSortType,
-            communityName: communityName,
-            communityId: communityId,
-            userId: userId,
-            username: username,
-            postListingType: postListingType,
-          ),
+  SwipeablePageRoute route = SwipeablePageRoute(
+    transitionDuration: isLoadingPageShown
+        ? Duration.zero
+        : reduceAnimations
+            ? const Duration(milliseconds: 100)
+            : null,
+    reverseTransitionDuration: reduceAnimations ? const Duration(milliseconds: 100) : const Duration(milliseconds: 500),
+    backGestureDetectionWidth: 45,
+    canOnlySwipeFromEdge: disableFullPageSwipe(isUserLoggedIn: authBloc.state.isLoggedIn, state: thunderBloc.state, isFeedPage: true) || !thunderState.enableFullScreenSwipeNavigationGesture,
+    builder: (context) => MultiBlocProvider(
+      providers: [
+        BlocProvider.value(value: accountBloc),
+        BlocProvider.value(value: authBloc),
+        BlocProvider.value(value: thunderBloc),
+        BlocProvider.value(value: instanceBloc),
+        BlocProvider.value(value: anonymousSubscriptionsBloc),
+        BlocProvider.value(value: communityBloc),
+      ],
+      child: Material(
+        child: FeedPage(
+          feedType: feedType,
+          sortType: sortType ?? thunderBloc.state.defaultSortType,
+          communityName: communityName,
+          communityId: communityId,
+          userId: userId,
+          username: username,
+          postListingType: postListingType,
         ),
       ),
     ),
   );
+
+  pushOnTopOfLoadingPage(context, route);
 }
 
 Future<void> triggerRefresh(BuildContext context) async {

lib/shared/link_preview_card.dart

@@ -267,31 +267,7 @@ class LinkPreviewCard extends StatelessWidget {
     }
 
     if (originURL != null) {
-      String? communityName = await getLemmyCommunity(originURL!);
-
-      if (communityName != null) {
-        try {
-          await navigateToFeedPage(context, feedType: FeedType.community, communityName: communityName);
-          return;
-        } catch (e) {
-          // Ignore exception, if it's not a valid community we'll perform the next fallback
-        }
-      }
-
-      String? username = await getLemmyUser(originURL!);
-
-      if (username != null) {
-        try {
-          await navigateToFeedPage(context, feedType: FeedType.user, username: username);
-          return;
-        } catch (e) {
-          // Ignore exception, if it's not a valid user, we'll perform the next fallback
-        }
-      }
-
-      if (context.mounted) {
-        handleLink(context, url: originURL!);
-      }
+      handleLink(context, url: originURL!);
     }
   }
 

lib/shared/pages/loading_page.dart

@@ -0,0 +1,96 @@
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:swipeable_page_route/swipeable_page_route.dart';
+import 'package:thunder/thunder/bloc/thunder_bloc.dart';
+
+bool isLoadingPageShown = false;
+
+class LoadingPage extends StatelessWidget {
+  const LoadingPage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final ThemeData theme = Theme.of(context);
+
+    return Scaffold(
+      body: Container(
+        color: theme.colorScheme.background,
+        child: SafeArea(
+          top: false,
+          child: CustomScrollView(
+            slivers: [
+              SliverAppBar(
+                  toolbarHeight: 70.0,
+                  leading: IconButton(
+                    icon: !kIsWeb && Platform.isIOS
+                        ? Icon(
+                            Icons.arrow_back_ios_new_rounded,
+                            semanticLabel: MaterialLocalizations.of(context).backButtonTooltip,
+                          )
+                        : Icon(Icons.arrow_back_rounded, semanticLabel: MaterialLocalizations.of(context).backButtonTooltip),
+                    onPressed: () => Navigator.of(context).maybePop(),
+                  )),
+              const SliverFillRemaining(
+                child: Center(
+                  child: CircularProgressIndicator(),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+void showLoadingPage(BuildContext context) {
+  if (isLoadingPageShown) return;
+
+  isLoadingPageShown = true;
+
+  // Immediately push the  loading page.
+  final ThunderBloc thunderBloc = context.read<ThunderBloc>();
+  final bool reduceAnimations = thunderBloc.state.reduceAnimations;
+  Navigator.of(context).push(
+    SwipeablePageRoute(
+      transitionDuration: reduceAnimations ? const Duration(milliseconds: 100) : null,
+      backGestureDetectionWidth: 45,
+      canOnlySwipeFromEdge: !thunderBloc.state.enableFullScreenSwipeNavigationGesture,
+      builder: (context) => MultiBlocProvider(
+        providers: [
+          BlocProvider.value(value: thunderBloc),
+        ],
+        child: PopScope(
+          onPopInvoked: (didPop) => isLoadingPageShown = !didPop,
+          child: const LoadingPage(),
+        ),
+      ),
+    ),
+  );
+}
+
+Future<void> hideLoadingPage(BuildContext context, {bool delay = false}) async {
+  if (isLoadingPageShown) {
+    isLoadingPageShown = false;
+
+    if (delay) {
+      await Future.delayed(const Duration(seconds: 1));
+    }
+
+    if (context.mounted) {
+      Navigator.of(context).maybePop();
+    }
+  }
+}
+
+void pushOnTopOfLoadingPage(BuildContext context, Route route) {
+  if (isLoadingPageShown) {
+    isLoadingPageShown = false;
+    Navigator.of(context).pushReplacement(route);
+  } else {
+    Navigator.of(context).push(route);
+  }
+}

lib/utils/links.dart

@@ -9,7 +9,10 @@ import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:lemmy_api_client/v3.dart';
 import 'package:link_preview_generator/link_preview_generator.dart';
 import 'package:share_plus/share_plus.dart';
+import 'package:swipeable_page_route/swipeable_page_route.dart';
 import 'package:thunder/core/enums/browser_mode.dart';
+import 'package:thunder/instances.dart';
+import 'package:thunder/shared/pages/loading_page.dart';
 import 'package:thunder/shared/webview.dart';
 import 'package:thunder/utils/bottom_sheet_list_picker.dart';
 import 'package:thunder/utils/media/image.dart';
@@ -70,9 +73,11 @@ void _openLink(BuildContext context, {required String url}) async {
   ThunderState state = context.read<ThunderBloc>().state;
 
   if (state.browserMode == BrowserMode.external || (!kIsWeb && !Platform.isAndroid && !Platform.isIOS)) {
+    hideLoadingPage(context, delay: true);
     url_launcher.launchUrl(Uri.parse(url), mode: url_launcher.LaunchMode.externalApplication);
   } else if (state.browserMode == BrowserMode.customTabs) {
-    await launchUrl(
+    hideLoadingPage(context, delay: true);
+    launchUrl(
       Uri.parse(url),
       customTabsOptions: CustomTabsOptions(
         browser: const CustomTabsBrowserConfiguration(
@@ -101,13 +106,24 @@ void _openLink(BuildContext context, {required String url}) async {
     if (uri != null && uri.scheme != 'https') {
       // Although a non-https scheme is an indication that this link is intended for another app,
       // we actually have to change it back to https in order for the intent to be properly passed to another app.
+      hideLoadingPage(context, delay: true);
       url_launcher.launchUrl(uri, mode: url_launcher.LaunchMode.externalApplication);
     } else {
-      Navigator.of(context).push(
-        MaterialPageRoute(
-          builder: (context) => WebView(url: url),
-        ),
+      final bool reduceAnimations = state.reduceAnimations;
+
+      SwipeablePageRoute route = SwipeablePageRoute(
+        transitionDuration: isLoadingPageShown
+            ? Duration.zero
+            : reduceAnimations
+                ? const Duration(milliseconds: 100)
+                : null,
+        reverseTransitionDuration: reduceAnimations ? const Duration(milliseconds: 100) : const Duration(milliseconds: 500),
+        backGestureDetectionWidth: 45,
+        canOnlySwipeFromEdge: true,
+        builder: (context) => WebView(url: url),
       );
+
+      pushOnTopOfLoadingPage(context, route);
     }
   }
 }
@@ -121,7 +137,7 @@ void handleLink(BuildContext context, {required String url}) async {
 
   // Try navigating to community
   String? communityName = await getLemmyCommunity(url);
-  if (communityName != null) {
+  if (communityName != null && (!context.mounted || await _testValidCommunity(context, url, communityName, communityName.split('@')[1]))) {
     try {
       if (context.mounted) {
         await navigateToFeedPage(context, feedType: FeedType.community, communityName: communityName);
@@ -134,7 +150,7 @@ void handleLink(BuildContext context, {required String url}) async {
 
   // Try navigating to user
   String? username = await getLemmyUser(url);
-  if (username != null) {
+  if (username != null && (!context.mounted || await _testValidUser(context, url, username, username.split('@')[1]))) {
     try {
       if (context.mounted) {
         await navigateToFeedPage(context, feedType: FeedType.user, username: username);
@@ -197,6 +213,64 @@ void handleLink(BuildContext context, {required String url}) async {
   }
 }
 
+/// This is a helper method which helps [handleLink] determine whether a link refers to a valid Lemmy community.
+/// If the passed in link is not a valid URI, then there's no point in doing any fallback, so assume it passes.
+/// If the passed in [instance] is a known Lemmy instance, then it passes.
+/// If we can retrieve the passed in object, then it passes.
+/// Otherwise it fails.
+Future<bool> _testValidCommunity(BuildContext context, String link, String communityName, String instance) async {
+  Uri? uri = Uri.tryParse(link);
+  if (uri == null || !uri.hasScheme) {
+    return true;
+  }
+
+  if (instances.contains(instance)) {
+    return true;
+  }
+
+  try {
+    // Since this may take a while, show a loading page.
+    showLoadingPage(context);
+
+    Account? account = await fetchActiveProfileAccount();
+    await LemmyClient.instance.lemmyApiV3.run(GetCommunity(name: communityName, auth: account?.jwt));
+    return true;
+  } catch (e) {
+    // Ignore and return false below.
+  }
+
+  return false;
+}
+
+/// This is a helper method which helps [handleLink] determine whether a link refers to a valid Lemmy user.
+/// If the passed in link is not a valid URI, then there's no point in doing any fallback, so assume it passes.
+/// If the passed in [instance] is a known Lemmy instance, then it passes.
+/// If we can retrieve the passed in object, then it passes.
+/// Otherwise it fails.
+Future<bool> _testValidUser(BuildContext context, String link, String userName, String instance) async {
+  Uri? uri = Uri.tryParse(link);
+  if (uri == null || !uri.hasScheme) {
+    return true;
+  }
+
+  if (instances.contains(instance)) {
+    return true;
+  }
+
+  try {
+    // Since this may take a while, show a loading page.
+    showLoadingPage(context);
+
+    Account? account = await fetchActiveProfileAccount();
+    await LemmyClient.instance.lemmyApiV3.run(GetPersonDetails(username: userName, auth: account?.jwt));
+    return true;
+  } catch (e) {
+    // Ignore and return false below.
+  }
+
+  return false;
+}
+
 void handleLinkLongPress(BuildContext context, ThunderState state, String text, String? url) {
   final theme = Theme.of(context);
   final l10n = AppLocalizations.of(context)!;