feat: Add support for messages filter in MessageListView and MessageListCore (#303)

* [MessageListView, MessageListCore] Add support for message filter

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

* [UI-Kit -> Pubspec] Remove `stream_chat_flutter_core` relative import

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

packages/stream_chat_flutter/lib/src/message_list_view.dart

@@ -135,6 +135,7 @@ class MessageListView extends StatefulWidget {
     this.systemMessageBuilder,
     this.messageListBuilder,
     this.errorWidgetBuilder,
+    this.messageFilter,
     this.customAttachmentBuilders,
     this.onMessageTap,
     this.onSystemMessageTap,
@@ -214,6 +215,9 @@ class MessageListView extends StatefulWidget {
   /// of a connection failure.
   final ErrorBuilder errorWidgetBuilder;
 
+  /// Predicate used to filter messages
+  final bool Function(Message) messageFilter;
+
   /// Attachment builders for the default message widget
   /// Please change this in the [MessageWidget] if you are using a custom implementation
   final Map<String, AttachmentBuilder> customAttachmentBuilders;
@@ -281,6 +285,7 @@ class _MessageListViewState extends State<MessageListView> {
   @override
   Widget build(BuildContext context) {
     return MessageListCore(
+      messageFilter: widget.messageFilter,
       loadingBuilder: widget.loadingBuilder ??
           (context) {
             return Center(

packages/stream_chat_flutter_core/lib/src/message_list_core.dart

@@ -64,6 +64,7 @@ class MessageListCore extends StatefulWidget {
     this.showScrollToBottom = true,
     this.parentMessage,
     this.messageListController,
+    this.messageFilter,
   })  : assert(loadingBuilder != null),
         assert(emptyBuilder != null),
         assert(messageListBuilder != null),
@@ -95,6 +96,9 @@ class MessageListCore extends StatefulWidget {
   /// first message or the parent of the conversation.
   final Message parentMessage;
 
+  /// Predicate used to filter messages
+  final bool Function(Message) messageFilter;
+
   @override
   _MessageListCoreState createState() => _MessageListCoreState();
 }
@@ -106,6 +110,8 @@ class _MessageListCoreState extends State<MessageListCore> {
 
   bool get _isThreadConversation => widget.parentMessage != null;
 
+  OwnUser get _currentUser => streamChannel.channel.client.state.user;
+
   int initialIndex;
   double initialAlignment;
 
@@ -121,13 +127,16 @@ class _MessageListCoreState extends State<MessageListCore> {
             .map((threads) => threads[widget.parentMessage.id])
         : streamChannel.channel.state?.messagesStream;
 
+    bool defaultFilter(Message m) {
+      final isMyMessage = m.user.id == _currentUser.id;
+      final isDeletedOrShadowed = m.isDeleted || m.shadowed;
+      if (isDeletedOrShadowed && !isMyMessage) return false;
+      return true;
+    }
+
     return StreamBuilder<List<Message>>(
-      stream: messagesStream?.map((messages) => messages
-          ?.where((e) =>
-              (!e.isDeleted && e.shadowed != true) ||
-              (e.isDeleted &&
-                  e.user.id == streamChannel.channel.client.state.user.id))
-          ?.toList()),
+      stream: messagesStream?.map((messages) =>
+          messages?.where(widget.messageFilter ?? defaultFilter)?.toList()),
       builder: (context, snapshot) {
         if (!snapshot.hasData) {
           return widget.loadingBuilder(context);