feat: 2 way pagination

Signed-off-by: Sahil Kumar <[email protected]>

example/lib/main.dart

@@ -294,7 +294,16 @@ class _ChannelListPageState extends State<ChannelListPage> {
   @override
   Widget build(BuildContext context) {
     final user = StreamChat.of(context).user;
-    return ChannelsBloc(
+    return WillPopScope(
+      onWillPop: () async {
+        if (_isSearchActive) {
+          _controller.clear();
+          setState(() => _isSearchActive = false);
+          return false;
+        }
+        return true;
+      },
+      child: ChannelsBloc(
         child: MessageSearchBloc(
           child: Column(
             children: [
@@ -323,7 +332,48 @@ class _ChannelListPageState extends State<ChannelListPage> {
                               ),
                             ],
                             paginationParams: PaginationParams(limit: 20),
-                          onItemTap: (message) {},
+                            onItemTap: (messageResponse) async {
+                              final client = StreamChat.of(context).client;
+                              final message = messageResponse.message;
+                              final channel = Channel.fromState(
+                                client,
+                                ChannelState(
+                                  channel: messageResponse.channel,
+                                  messages: [message],
+                                ),
+                              );
+                              await Future.wait([
+                                channel.query(
+                                  messagesPagination: PaginationParams(
+                                    lessThan: message.id,
+                                    limit: 25,
+                                  ),
+                                  preferOffline: true,
+                                ),
+                                channel.query(
+                                  messagesPagination: PaginationParams(
+                                    greaterThan: message.id,
+                                    limit: 25,
+                                  ),
+                                  preferOffline: true,
+                                ),
+                              ]);
+                              final messages = channel.state.messages;
+                              final totalMessages = messages.length;
+                              final messageIndex = messages
+                                  .indexWhere((e) => e.id == message.id);
+                              final initialIndex = totalMessages - messageIndex;
+                              final bool isFirstMessage = messageIndex == 0;
+                              Navigator.pushNamed(
+                                context,
+                                Routes.CHANNEL_PAGE,
+                                arguments: ChannelPageArgs(
+                                  channel: channel,
+                                  initialScrollIndex: initialIndex,
+                                  initialAlignment: isFirstMessage ? 0 : 0.5,
+                                ),
+                              );
+                            },
                           )
                         : ChannelListView(
                             onStartChatPressed: () {
@@ -349,75 +399,31 @@ class _ChannelListPageState extends State<ChannelListPage> {
             ],
           ),
         ),
+      ),
     );
   }
 }
 
-class ChannelQuerySearchResultPage extends StatelessWidget {
+class ChannelPageArgs {
-  final Stream<List<Message>> searchResultStream;
+  final Channel channel;
+  final int initialScrollIndex;
+  final double initialAlignment;
 
-  const ChannelQuerySearchResultPage({
+  const ChannelPageArgs({
-    Key key,
+    this.channel,
-    @required this.searchResultStream,
+    this.initialScrollIndex = 0,
-  }) : super(key: key);
+    this.initialAlignment = 0,
-
+  });
-  @override
-  Widget build(BuildContext context) {
-    return StreamBuilder<List<Message>>(
-      initialData: const <Message>[],
-      stream: searchResultStream,
-      builder: (context, snapshot) {
-        final result = snapshot.data;
-        return Column(
-          children: [
-            if (result.isNotEmpty)
-              Container(
-                width: double.maxFinite,
-                decoration: BoxDecoration(
-                  gradient: LinearGradient(
-                    begin: Alignment.centerLeft,
-                    end: Alignment.centerRight,
-                    colors: [
-                      Colors.black.withOpacity(0.02),
-                      Colors.white.withOpacity(0.05),
-                    ],
-                    stops: [0, 1],
-                  ),
-                ),
-                child: Padding(
-                  padding: const EdgeInsets.symmetric(
-                    vertical: 8,
-                    horizontal: 8,
-                  ),
-                  child: Text(
-                    '${result.length} results',
-                    style: TextStyle(
-                      color: Colors.black.withOpacity(0.5),
-                    ),
-                  ),
-                ),
-              ),
-            Expanded(
-              child: ListView.builder(
-                itemCount: result.length,
-                itemBuilder: (context, index) {
-                  return ListTile(
-                    leading: UserAvatar(),
-                    title: Text(result[index].toJson().toString()),
-                  );
-                },
-              ),
-            ),
-          ],
-        );
-      },
-    );
-  }
 }
 
 class ChannelPage extends StatelessWidget {
+  final int initialScrollIndex;
+  final double initialAlignment;
+
   const ChannelPage({
     Key key,
+    this.initialScrollIndex = 0,
+    this.initialAlignment = 0,
   }) : super(key: key);
 
   @override
@@ -433,6 +439,8 @@ class ChannelPage extends StatelessWidget {
             child: Stack(
               children: <Widget>[
                 MessageListView(
+                  initialScrollIndex: initialScrollIndex,
+                  initialAlignment: initialAlignment,
                   threadBuilder: (_, parentMessage) {
                     return ThreadPage(
                       parent: parentMessage,
@@ -467,10 +475,14 @@ class ChannelPage extends StatelessWidget {
 
 class ThreadPage extends StatelessWidget {
   final Message parent;
+  final int initialScrollIndex;
+  final double initialAlignment;
 
   ThreadPage({
     Key key,
     this.parent,
+    this.initialScrollIndex = 0,
+    this.initialAlignment = 0,
   }) : super(key: key);
 
   @override
@@ -484,6 +496,8 @@ class ThreadPage extends StatelessWidget {
           Expanded(
             child: MessageListView(
               parentMessage: parent,
+              initialScrollIndex: initialScrollIndex,
+              initialAlignment: initialAlignment,
             ),
           ),
           if (parent.type != 'deleted')

example/lib/routes/app_routes.dart

@@ -34,9 +34,13 @@ class AppRoutes {
         return MaterialPageRoute(
             settings: const RouteSettings(name: Routes.CHANNEL_PAGE),
             builder: (_) {
+              final arg = args as ChannelPageArgs;
               return StreamChannel(
-                channel: args as Channel,
+                channel: arg.channel,
-                child: ChannelPage(),
+                child: ChannelPage(
+                  initialScrollIndex: arg.initialScrollIndex,
+                  initialAlignment: arg.initialAlignment,
+                ),
               );
             });
       case Routes.NEW_CHAT:

lib/src/message_list_view.dart

@@ -480,8 +480,8 @@ class _MessageListViewState extends State<MessageListView> {
           } else {
             streamChannel.getReplies(widget.parentMessage.id);
           }
+          _topWasVisible = !topIsVisible;
         }
-        _topWasVisible = topIsVisible;
       },
     );
   }
@@ -515,14 +515,21 @@ class _MessageListViewState extends State<MessageListView> {
       key: ValueKey<String>('BOTTOM-MESSAGE'),
       onVisibilityChanged: (visibility) {
         final isVisible = visibility.visibleBounds != Rect.zero;
-        if (isVisible &&
+        if (isVisible && !_bottomWasVisible) {
-            !_bottomWasVisible &&
+          if (widget.parentMessage == null) {
-            streamChannel.channel.config?.readEvents == true) {
+            streamChannel.queryMessages(direction: QueryDirection.bottom);
-          if (streamChannel.channel.state.unreadCount > 0) {
+          } else {
+            streamChannel.getReplies(
+              widget.parentMessage.id,
+              direction: QueryDirection.bottom,
+            );
+          }
+          if (streamChannel.channel.config?.readEvents == true &&
+              streamChannel.channel.state.unreadCount > 0) {
             streamChannel.channel.markRead();
           }
+          _bottomWasVisible = !isVisible;
         }
-        _bottomWasVisible = isVisible;
         if (mounted) {
           setState(() {
             _showScrollToBottom = !isVisible;

lib/src/stream_channel.dart

@@ -4,6 +4,8 @@ import 'package:flutter/material.dart';
 import 'package:rxdart/rxdart.dart';
 import 'package:stream_chat/stream_chat.dart';
 
+enum QueryDirection { top, bottom }
+
 /// Widget used to provide information about the channel to the widget tree
 ///
 /// Use [StreamChannel.of] to get the current [StreamChannelState] instance.
@@ -52,34 +54,57 @@ class StreamChannelState extends State<StreamChannel> {
   /// The stream notifying the state of queryMessage call
   Stream<bool> get queryMessage => _queryMessageController.stream;
 
-  bool _paginationEnded = false;
+  bool _topPaginationEnded = false;
+  bool _bottomPaginationEnded = false;
 
   /// Calls [channel.query] updating [queryMessage] stream
-  void queryMessages() {
+  void queryMessages({QueryDirection direction = QueryDirection.top}) {
-    if (_queryMessageController.value == true || _paginationEnded) {
+    if (_queryMessageController.value == true ||
+        (_topPaginationEnded && _bottomPaginationEnded)) {
       return;
     }
 
     _queryMessageController.add(true);
 
-    String firstId;
+    String id;
-    if (channel.state.messages.isNotEmpty) {
+    PaginationParams params;
-      firstId = channel.state.messages.first.id;
-    }
 
-    final messageLimit = 50;
+    final messageLimit = 25;
+
+    if (channel.state.messages.isNotEmpty) {
+      switch (direction) {
+        case QueryDirection.top:
+          id = channel.state.messages.first.id;
+          params = PaginationParams(
+            lessThan: id,
+            limit: messageLimit,
+          );
+          break;
+        case QueryDirection.bottom:
+          id = channel.state.messages.last.id;
+          params = PaginationParams(
+            greaterThan: id,
+            limit: messageLimit,
+          );
+          break;
+      }
+    }
 
     widget.channel
         .query(
-      messagesPagination: PaginationParams(
+      messagesPagination: params,
-        lessThan: firstId,
-        limit: messageLimit,
-      ),
       preferOffline: true,
     )
         .then((res) {
       if (res.messages.isEmpty || res.messages.length < messageLimit) {
-        _paginationEnded = true;
+        switch (direction) {
+          case QueryDirection.top:
+            _topPaginationEnded = true;
+            break;
+          case QueryDirection.bottom:
+            _bottomPaginationEnded = true;
+            break;
+        }
       }
       _queryMessageController.add(false);
     }).catchError((e, stack) {
@@ -90,35 +115,60 @@ class StreamChannelState extends State<StreamChannel> {
   }
 
   /// Calls [channel.getReplies] updating [queryMessage] stream
-  Future<void> getReplies(String parentId) async {
+  Future<void> getReplies(
-    if (_queryMessageController.value == true || _paginationEnded) {
+    String parentId, {
+    QueryDirection direction = QueryDirection.top,
+  }) async {
+    if (_queryMessageController.value == true ||
+        (_topPaginationEnded && _bottomPaginationEnded)) {
       return;
     }
 
     _queryMessageController.add(true);
 
-    String firstId;
+    String id;
-    if (widget.channel.state.threads.containsKey(parentId)) {
+    PaginationParams params;
-      final thread = widget.channel.state.threads[parentId];
-
-      if (thread != null && thread.isNotEmpty) {
-        firstId = thread?.first?.id;
-      }
-    }
 
     final messageLimit = 50;
+
+    if (widget.channel.state.threads.containsKey(parentId)) {
+      final thread = widget.channel.state.threads[parentId];
+      if (thread != null && thread.isNotEmpty) {
+        switch (direction) {
+          case QueryDirection.top:
+            id = thread?.first?.id;
+            params = PaginationParams(
+              lessThan: id,
+              limit: messageLimit,
+            );
+            break;
+          case QueryDirection.bottom:
+            id = thread?.last?.id;
+            params = PaginationParams(
+              greaterThan: id,
+              limit: messageLimit,
+            );
+            break;
+        }
+      }
+    }
+
     return widget.channel
         .getReplies(
       parentId,
-      PaginationParams(
+      params,
-        lessThan: firstId,
-        limit: messageLimit,
-      ),
       preferOffline: true,
     )
         .then((res) {
       if (res.messages.isEmpty || res.messages.length < messageLimit) {
-        _paginationEnded = true;
+        switch (direction) {
+          case QueryDirection.top:
+            _topPaginationEnded = true;
+            break;
+          case QueryDirection.bottom:
+            _bottomPaginationEnded = true;
+            break;
+        }
       }
       _queryMessageController.add(false);
     }).catchError((e, stack) {

pubspec.yaml

@@ -28,7 +28,10 @@ dependencies:
   file_picker: ^2.0.12
   image_picker: ^0.6.7+2
   flutter_keyboard_visibility: ^3.3.0
-  stream_chat: ^0.2.14
+  stream_chat:
+    git:
+      url: https://github.com/GetStream/stream-chat-dart
+      ref: two-way-pagination
   mime: ^0.9.6+3
   video_compress: ^2.1.1
   visibility_detector: ^0.1.5