Mark discussion as read upon reply

framework/core/src/Flarum/Api/Actions/Posts/Create.php

@@ -2,6 +2,7 @@
 
 use Event;
 use Flarum\Core\Posts\Commands\PostReplyCommand;
+use Flarum\Core\Discussions\Commands\ReadDiscussionCommand;
 use Flarum\Core\Users\User;
 use Flarum\Api\Actions\Base;
 use Flarum\Api\Serializers\PostSerializer;
@@ -15,6 +16,8 @@ class Create extends Base
      */
     protected function run()
     {
+        $user = User::current();
+
         // We've received a request to post a reply. By default, the only
         // required attributes of a post is the ID of the discussion to post in,
         // the post content, and the author's user account. Let's set up a
@@ -22,12 +25,20 @@ class Create extends Base
         // to add data to the command.
         $discussionId = $this->input('posts.links.discussion');
         $content = $this->input('posts.content');
-        $command = new PostReplyCommand($discussionId, $content, User::current());
+        $command = new PostReplyCommand($discussionId, $content, $user);
 
         Event::fire('Flarum.Api.Actions.Posts.Create.WillExecuteCommand', [$command]);
 
         $post = $this->commandBus->execute($command);
 
+        // After replying, we assume that the user has seen all of the posts
+        // in the discussion; thus, we will mark the discussion as read if
+        // they are logged in.
+        if ($user->exists) {
+            $command = new ReadDiscussionCommand($discussionId, $user, $post->number);
+            $this->commandBus->execute($command);
+        }
+
         // Presumably, the post was created successfully. (The command handler
         // would have thrown an exception if not.) We set this post as our
         // document's primary element.