added docs and reactions modal

packages/stream_chat/lib/src/permission_type.dart

@@ -1,37 +1,81 @@
+/// Describes capabilities of a user vis-a-vis a channel
 class PermissionType {
-  static const String sendMessage = "send-message";
+  /// Capability required to send a message in the channel
+  /// Channel is not frozen (or user has UseFrozenChannel permission)
+  /// and user has CreateMessage permission.
+  static const String sendMessage = 'send-message';
 
-  static const String sendReaction = "send-reaction";
+  /// Capability required to send a message
+  /// Reactions are enabled for the channel, channel is not frozen
+  /// (or user has UseFrozenChannel permission) and user has
+  /// CreateReaction permission
+  static const String sendReaction = 'send-reaction';
 
-  static const String sendLinks = "send-links";
+  /// Capability required to send links in a channel
+  /// send-message + user has AddLinks permission
+  static const String sendLinks = 'send-links';
 
-  static const String sendReply = "send-reply";
+  /// Capability required to send thread reply
+  /// send-message + channel has replies enabled
+  static const String sendReply = 'send-reply';
 
-  static const String freezeChannel = "freeze-channel";
+  /// Capability to freeze a channel
+  /// User has UpdateChannelFrozen permission.
+  /// The name implies freezing,
+  /// but unfreezing is also allowed when this capability is present
+  static const String freezeChannel = 'freeze-channel';
 
-  static const String setChannelCooldown = "set-channel-cooldown";
+  /// User has UpdateChannelCooldown permission.
+  /// Allows to enable/disable slow mode in the channel
+  static const String setChannelCooldown = 'set-channel-cooldown';
 
-  static const String leaveChannel = "leave-channel";
+  /// User has RemoveOwnChannelMembership or UpdateChannelMembers permission
+  static const String leaveChannel = 'leave-channel';
 
-  static const String pinMessage = "pin-message";
+  /// Capability required to pin a message in a channel
+  /// Corresponds to PinMessage permission
+  static const String pinMessage = 'pin-message';
 
-  static const String deleteAnyMessage = "delete-any-message";
+  /// User has ability to delete any message in the channel
+  /// User has DeleteMessage permission
+  /// which applies to any message in the channel
+  static const String deleteAnyMessage = 'delete-any-message';
 
-  static const String deleteOwnMessage = "delete-own-message";
+  /// User has ability to delete their own message in the channel
+  /// User has DeleteMessage permission which applies only to owned messages
+  static const String deleteOwnMessage = 'delete-own-message';
 
-  static const String updateAnyMessage = "update-any-message";
+  /// User has ability to update/edit any message in the channel
+  /// User has UpdateMessage permission which
+  /// applies to any message in the channel
+  static const String updateAnyMessage = 'update-any-message';
 
-  static const String updateOwnMessage = "update-own-message";
+  /// User has ability to update/edit their own message in the channel
+  /// User has UpdateMessage permission which applies only to owned messages
+  static const String updateOwnMessage = 'update-own-message';
 
-  static const String searchMessages = "search-messages";
+  /// User can search for message in a channel
+  /// Search feature is enabled (it will also have
+  /// permission check in the future)
+  static const String searchMessages = 'search-messages';
 
-  static const String sendTypingEvents = "send-typing-events";
+  /// Capability required to send typing events in a channel
+  /// (Typing events are enabled)
+  static const String sendTypingEvents = 'send-typing-events';
 
-  static const String uploadFile = "upload-file";
+  /// Capability required to upload a file in a channel
+  /// Uploads are enabled and user has UploadAttachment
+  static const String uploadFile = 'upload-file';
 
-  static const String deleteChannel = "delete-channel";
+  /// Capability required to delete channel
+  /// User has DeleteChannel permission
+  static const String deleteChannel = 'delete-channel';
 
-  static const String updateChannel = "update-channel";
+  /// Capability required update/edit channel info
+  /// User has UpdateChannel permission
+  static const String updateChannel = 'update-channel';
 
-  static const String updateChannelMembers = "update-channel-members";
+  /// Capability required to update/edit channel members
+  /// Channel is not distinct and user has UpdateChannelMembers permission
+  static const String updateChannelMembers = 'update-channel-members';
 }

packages/stream_chat_flutter/lib/src/message_reactions_modal.dart

@@ -18,7 +18,7 @@ class MessageReactionsModal extends StatelessWidget {
     required this.message,
     required this.messageWidget,
     required this.messageTheme,
-    this.showReactions = true,
+    this.showReactions,
     this.reverse = false,
     this.onUserAvatarTap,
   }) : super(key: key);
@@ -36,7 +36,7 @@ class MessageReactionsModal extends StatelessWidget {
   final bool reverse;
 
   /// Flag to show reactions on message
-  final bool showReactions;
+  final bool? showReactions;
 
   /// Callback when user avatar is tapped
   final void Function(User)? onUserAvatarTap;
@@ -45,6 +45,16 @@ class MessageReactionsModal extends StatelessWidget {
   Widget build(BuildContext context) {
     final size = MediaQuery.of(context).size;
     final user = StreamChat.of(context).currentUser;
+    final _userPermissions = StreamChannel.of(context)
+            .channel
+            .state
+            ?.channelState
+            .channel
+            ?.ownCapabilities ??
+        [];
+
+    final hasReactionPermission =
+        _userPermissions.contains(PermissionType.sendReaction);
 
     final roughMaxSize = size.width * 2 / 3;
     var messageTextLength = message.text!.length;
@@ -76,7 +86,7 @@ class MessageReactionsModal extends StatelessWidget {
             mainAxisAlignment: MainAxisAlignment.center,
             crossAxisAlignment: CrossAxisAlignment.stretch,
             children: <Widget>[
-              if (showReactions &&
+              if ((showReactions ?? hasReactionPermission) &&
                   (message.status == MessageSendingStatus.sent))
                 Align(
                   alignment: Alignment(