Add server-generated URL preview support

README.md

@@ -67,6 +67,7 @@ A simple and user-friendly Matrix client made with Flutter and a Gomuks backend.
         - [x] Plain text
         - [x] Per message profiles
         - [x] HTML
+        - [x] URL Previews
             - [x] Replies
                 - [x] Viewing
                 - [ ] Jump to original message
@@ -116,7 +117,7 @@ A simple and user-friendly Matrix client made with Flutter and a Gomuks backend.
     - [ ] Devices
         - [ ] Viewing devices
         - [ ] Verifying devices
-    - [ ] URL preview: Server / Client / None
+    - [ ] URL preview: Server / Sending Client (Beeper spec) / None
     - [ ] Account changes
         - [ ] Display name
         - [ ] Profile picture

lib/controllers/url_preview_controller.dart

@@ -0,0 +1,63 @@
+import "dart:convert";
+import "package:flutter_chat_core/flutter_chat_core.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:http/http.dart";
+import "package:nexus/controllers/client_state_controller.dart";
+import "package:nexus/controllers/header_controller.dart";
+import "package:nexus/helpers/extensions/mxc_to_https.dart";
+
+class UrlPreviewController extends AsyncNotifier<LinkPreviewData?> {
+  final TextMessage message;
+  UrlPreviewController(this.message);
+
+  @override
+  Future<LinkPreviewData?> build() async {
+    final homeserver = ref.watch(ClientStateController.provider)?.homeserverUrl;
+    final link = RegExp(
+      r'''https?://[^\s"'<>]+''',
+    ).allMatches(message.text).firstOrNull?.group(0);
+
+    if (homeserver != null && link != null) {
+      {
+        final response = await get(
+          Uri.parse(homeserver)
+              .resolve("/_matrix/client/v1/media/preview_url")
+              .replace(queryParameters: {"url": link}),
+          headers: await ref.watch(HeaderController.provider.future),
+        );
+
+        if (response.statusCode == 200) {
+          final decodedValue = json.decode(response.body);
+          final mxc = decodedValue["og:image"];
+          final image = mxc == null
+              ? null
+              : Uri.tryParse(mxc)?.mxcToHttps(homeserver);
+
+          return LinkPreviewData(
+            link: link,
+            title: decodedValue["og:title"],
+            description: decodedValue["og:description"],
+            image: image == null
+                ? null
+                : ImagePreviewData(
+                    url: image.toString(),
+                    width:
+                        (decodedValue["og:image:width"] as int?)?.toDouble() ??
+                        0,
+                    height:
+                        (decodedValue["og:image:height"] as int?)?.toDouble() ??
+                        0,
+                  ),
+          );
+        }
+      }
+    }
+
+    return null;
+  }
+
+  static final provider = AsyncNotifierProvider.autoDispose
+      .family<UrlPreviewController, LinkPreviewData?, TextMessage>(
+        UrlPreviewController.new,
+      );
+}

lib/widgets/chat_page/wrappers/text_message_wrapper.dart

@@ -1,11 +1,17 @@
+import "package:cross_cache/cross_cache.dart";
 import "package:flutter/material.dart";
 import "package:flutter_chat_core/flutter_chat_core.dart";
 import "package:flutter_link_previewer/flutter_link_previewer.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/cross_cache_controller.dart";
+import "package:nexus/controllers/url_preview_controller.dart";
+import "package:nexus/helpers/extensions/better_when.dart";
+import "package:nexus/helpers/extensions/get_headers.dart";
 import "package:nexus/widgets/chat_page/html/html.dart";
 import "package:nexus/widgets/chat_page/wrappers/message_wrapper.dart";
 import "package:nexus/widgets/chat_page/reply_widget.dart";
 
-class TextMessageWrapper extends StatelessWidget {
+class TextMessageWrapper extends ConsumerWidget {
   final Message message;
   final String? content;
   final MessageGroupStatus? groupStatus;
@@ -27,7 +33,7 @@ class TextMessageWrapper extends StatelessWidget {
   });
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     final theme = Theme.of(context);
     final colorScheme = theme.colorScheme;
     final textMessage = message is TextMessage ? message as TextMessage : null;
@@ -80,7 +86,22 @@ class TextMessageWrapper extends StatelessWidget {
               if (textMessage?.editedAt != null)
                 Text("(edited)", style: theme.textTheme.labelSmall),
               if (textMessage != null)
-                LinkPreview(
+                ref
+                    .watch(UrlPreviewController.provider(textMessage))
+                    .betterWhen(
+                      loading: SizedBox.shrink,
+                      data: (preview) => preview == null
+                          ? SizedBox.shrink()
+                          : LinkPreview(
+                              imageBuilder: (url) => Image(
+                                image: CachedNetworkImage(
+                                  url,
+                                  ref.watch(CrossCacheController.provider),
+                                  headers: ref.headers,
+                                ),
+                                fit: BoxFit.cover,
+                                errorBuilder: (_, _, _) => SizedBox.shrink(),
+                              ),
                               text: textMessage.text,
                               backgroundColor: isSentByMe
                                   ? colorScheme.inversePrimary
@@ -90,15 +111,8 @@ class TextMessageWrapper extends StatelessWidget {
                                 vertical: 8,
                                 horizontal: 16,
                               ),
-                  linkPreviewData: message.metadata?["linkPreviewData"],
+                              linkPreviewData: preview,
-                  onLinkPreviewDataFetched: (linkPreviewData) => updateMessage(
+                              onLinkPreviewDataFetched: (_) => null,
-                    message,
-                    message.copyWith(
-                      metadata: {
-                        ...(message.metadata ?? {}),
-                        "linkPreviewData": linkPreviewData,
-                      },
-                    ),
                             ),
                     ),
               if (extra != null) extra!,

pubspec.lock

@@ -655,7 +655,7 @@ packages:
     source: hosted
     version: "0.15.6"
   http:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: http
       sha256: "87721a4a50b19c7f1d49001e51409bddc46303966ce89a65af4f4e6004896412"

pubspec.yaml

@@ -56,6 +56,7 @@ dependencies:
   code_assets: ^1.0.0
   ffigen: ^20.1.1
   timeago: ^3.7.1
+  http: ^1.6.0
   
 dev_dependencies:
   build_runner: ^2.4.11