content: Implement inline video preview

Fixes: zulip#356

assets/l10n/app_en.arb

@@ -381,6 +381,10 @@
       "httpStatus": {"type": "int", "example": "500"}
     }
   },
+  "errorVideoPlayerFailed": "Unable to play the video",
+  "@errorVideoPlayerFailed": {
+    "description": "Error message when a video fails to play."
+  },
   "serverUrlValidationErrorEmpty": "Please enter a URL.",
   "@serverUrlValidationErrorEmpty": {
     "description": "Error message when URL is empty"

lib/widgets/content.dart

@@ -99,13 +99,7 @@ class BlockContentList extends StatelessWidget {
           );
           return MessageImage(node: node);
         } else if (node is InlineVideoNode) {
-          return Text.rich(
-            TextSpan(children: [
-              const TextSpan(text: "(unimplemented:", style: errorStyle),
-              TextSpan(text: node.debugHtmlText, style: errorCodeStyle),
-              const TextSpan(text: ")", style: errorStyle),
-            ]),
-            style: errorStyle);
+          return MessageInlineVideo(node: node);
         } else if (node is EmbedVideoNode) {
           return MessageEmbedVideo(node: node);
         } else if (node is UnimplementedBlockContentNode) {
@@ -386,7 +380,10 @@ class MessageImage extends StatelessWidget {
     return MessageMediaContainer(
       onTap: resolvedSrc == null ? null : () { // TODO(log)
         Navigator.of(context).push(getLightboxRoute(
-          context: context, message: message, src: resolvedSrc));
+          context: context,
+          message: message,
+          src: resolvedSrc,
+          mediaType: MediaType.image));
       },
       child: resolvedSrc == null ? null : LightboxHero(
         message: message,
@@ -397,6 +394,37 @@ class MessageImage extends StatelessWidget {
   }
 }
 
+class MessageInlineVideo extends StatelessWidget {
+  const MessageInlineVideo({super.key, required this.node});
+
+  final InlineVideoNode node;
+
+  @override
+  Widget build(BuildContext context) {
+    final message = InheritedMessage.of(context);
+    final store = PerAccountStoreWidget.of(context);
+    final resolvedSrc = store.tryResolveUrl(node.srcUrl);
+
+    return MessageMediaContainer(
+      onTap: resolvedSrc == null ? null : () { // TODO(log)
+        Navigator.of(context).push(getLightboxRoute(
+          context: context,
+          message: message,
+          src: resolvedSrc,
+          mediaType: MediaType.video));
+      },
+      child: Container(
+        color: Colors.black,
+        alignment: Alignment.center,
+        // To avoid potentially confusing UX, do not show play icon as
+        // we also disable onTap above.
+        child: resolvedSrc == null ? null : const Icon( // TODO(log)
+          Icons.play_arrow_rounded,
+          color: Colors.white,
+          size: 32)));
+  }
+}
+
 class MessageEmbedVideo extends StatelessWidget {
   const MessageEmbedVideo({super.key, required this.node});
 

lib/widgets/dialog.dart

@@ -19,16 +19,19 @@ Future<void> showErrorDialog({
   required BuildContext context,
   required String title,
   String? message,
+  bool barrierDismissible = true,
+  VoidCallback? onContinue,
 }) {
   final zulipLocalizations = ZulipLocalizations.of(context);
   return showDialog(
     context: context,
+    barrierDismissible: barrierDismissible,
     builder: (BuildContext context) => AlertDialog(
       title: Text(title),
       content: message != null ? SingleChildScrollView(child: Text(message)) : null,
       actions: [
         TextButton(
-          onPressed: () => Navigator.pop(context),
+          onPressed: onContinue ?? () => Navigator.pop(context),
           child: _dialogActionText(zulipLocalizations.errorDialogContinue)),
       ]));
 }

lib/widgets/lightbox.dart

@@ -1,10 +1,15 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 import 'package:intl/intl.dart';
+import 'package:video_player/video_player.dart';
 
+import '../api/core.dart';
 import '../api/model/model.dart';
+import '../log.dart';
 import 'content.dart';
+import 'dialog.dart';
 import 'page.dart';
 import 'clipboard.dart';
 import 'store.dart';
@@ -238,11 +243,164 @@ class _ImageLightboxPageState extends State<_ImageLightboxPage> {
   }
 }
 
+class VideoLightboxPage extends StatefulWidget {
+  const VideoLightboxPage({
+    super.key,
+    required this.routeEntranceAnimation,
+    required this.message,
+    required this.src,
+  });
+
+  final Animation routeEntranceAnimation;
+  final Message message;
+  final Uri src;
+
+  @override
+  State<VideoLightboxPage> createState() => _VideoLightboxPageState();
+}
+
+class _VideoLightboxPageState extends State<VideoLightboxPage> {
+  VideoPlayerController? _controller;
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    assert(debugLog('_VideoLightboxPageState($hashCode).didChangeDependencies'));
+
+    // We are pretty sure that the dependencies (PerAccountStore & ZulipLocalizations)
+    // won't change while user is on the lightbox page but we still
+    // handle the reinitialization for correctness.
+    if (_controller != null) _deinitialize();
+    _initialize();
+  }
+
+  Future<void> _initialize() async {
+    final store = PerAccountStoreWidget.of(context);
+    final zulipLocalizations = ZulipLocalizations.of(context);
+
+    assert(debugLog('VideoPlayerController.networkUrl(${widget.src})'));
+    _controller = VideoPlayerController.networkUrl(widget.src, httpHeaders: {
+      if (widget.src.origin == store.account.realmUrl.origin) ...authHeader(
+        email: store.account.email,
+        apiKey: store.account.apiKey,
+      ),
+      ...userAgentHeader()
+    });
+    _controller!.addListener(_handleVideoControllerUpdates);
+
+    try {
+      await _controller!.initialize();
+      await _controller!.play();
+    } catch (error) { // TODO(log)
+      assert(debugLog("VideoPlayerController.initialize failed: $error"));
+      if (mounted) {
+        await showErrorDialog(
+          context: context,
+          title: zulipLocalizations.errorDialogTitle,
+          message: zulipLocalizations.errorVideoPlayerFailed,
+          // To avoid showing the disabled video lightbox for the unnsupported
+          // video, we make sure user doesn't reach there by dismissing the dialog
+          // by clicking around it, user must press the 'OK' button, which will
+          // take user back to content message list.
+          barrierDismissible: false,
+          onContinue: () {
+            Navigator.pop(context); // Pops the dialog
+            Navigator.pop(context); // Pops the lightbox
+          });
+      }
+    }
+  }
+
+  @override
+  void dispose() {
+    _deinitialize();
+    super.dispose();
+  }
+
+  void _deinitialize() {
+    _controller?.removeListener(_handleVideoControllerUpdates);
+    _controller?.dispose();
+    _controller = null;
+  }
+
+  void _handleVideoControllerUpdates() {
+    setState(() {});
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return _LightboxPageLayout(
+      routeEntranceAnimation: widget.routeEntranceAnimation,
+      message: widget.message,
+      buildBottomAppBar: (context, color, elevation) =>
+        _controller == null
+          ? null
+          : BottomAppBar(
+              height: 150,
+              color: color,
+              elevation: elevation,
+              child: Column(mainAxisAlignment: MainAxisAlignment.end, children: [
+              Row(children: [
+                Text(_formatDuration(_controller!.value.position),
+                  style: const TextStyle(color: Colors.white)),
+                Expanded(child: Slider(
+                  value: _controller!.value.position.inSeconds.toDouble(),
+                  max: _controller!.value.duration.inSeconds.toDouble(),
+                  activeColor: Colors.white,
+                  onChanged: (value) {
+                    _controller!.seekTo(Duration(seconds: value.toInt()));
+                  })),
+                Text(_formatDuration(_controller!.value.duration),
+                  style: const TextStyle(color: Colors.white)),
+                ]),
+              IconButton(
+                onPressed: () {
+                  if (_controller!.value.isPlaying) {
+                    _controller!.pause();
+                  } else {
+                    _controller!.play();
+                  }
+                },
+                icon: Icon(
+                  _controller!.value.isPlaying
+                    ? Icons.pause_circle_rounded
+                    : Icons.play_circle_rounded,
+                  size: 50)),
+              ])),
+      child: SafeArea(
+        child: Center(
+          child: Stack(alignment: Alignment.center, children: [
+            if (_controller != null && _controller!.value.isInitialized)
+              AspectRatio(
+                aspectRatio: _controller!.value.aspectRatio,
+                child: VideoPlayer(_controller!)),
+            if (_controller == null || !_controller!.value.isInitialized || _controller!.value.isBuffering)
+              const SizedBox(
+                width: 32,
+                height: 32,
+                child: CircularProgressIndicator(color: Colors.white)),
+            ]))));
+  }
+
+  String _formatDuration(Duration value) {
+    final hours = value.inHours.toString().padLeft(2, '0');
+    final minutes = value.inMinutes.remainder(60).toString().padLeft(2, '0');
+    final seconds = value.inSeconds.remainder(60).toString().padLeft(2, '0');
+    return '${hours == '00' ? '' : '$hours:'}$minutes:$seconds';
+  }
+}
+
+enum MediaType {
+  video,
+  image
+}
+
 Route getLightboxRoute({
   int? accountId,
   BuildContext? context,
   required Message message,
   required Uri src,
+  required MediaType mediaType,
 }) {
   return AccountPageRouteBuilder(
     accountId: accountId,
@@ -254,7 +412,16 @@ Route getLightboxRoute({
       Animation<double> secondaryAnimation,
     ) {
       // TODO(#40): Drag down to close?
-      return _ImageLightboxPage(routeEntranceAnimation: animation, message: message, src: src);
+      return switch (mediaType) {
+        MediaType.image => _ImageLightboxPage(
+          routeEntranceAnimation: animation,
+          message: message,
+          src: src),
+        MediaType.video => VideoLightboxPage(
+          routeEntranceAnimation: animation,
+          message: message,
+          src: src),
+      };
     },
     transitionsBuilder: (
       BuildContext context,

test/test_animation.dart

@@ -0,0 +1,35 @@
+import 'package:flutter/widgets.dart';
+
+/// An animation that is always considered complete and
+/// immediately notifies listeners.
+///
+/// This is different from [kAlwaysCompleteAnimation] where
+/// it doesn't notify the listeners.
+class MockCompletedAnimation extends Animation<double> {
+  const MockCompletedAnimation();
+
+  @override
+  void addListener(VoidCallback listener) {
+    listener();
+  }
+
+  @override
+  void removeListener(VoidCallback listener) { }
+
+  @override
+  void addStatusListener(AnimationStatusListener listener) {
+    listener(AnimationStatus.completed);
+  }
+
+  @override
+  void removeStatusListener(AnimationStatusListener listener) { }
+
+  @override
+  AnimationStatus get status => AnimationStatus.completed;
+
+  @override
+  double get value => 1.0;
+
+  @override
+  String toString() => 'MockCompletedAnimation';
+}