Added listener to follow after a reply

bootstrap.php

@@ -16,9 +16,11 @@
 return function (Dispatcher $events, Factory $views) {
     $events->subscribe(Listener\AddClientAssets::class);
     $events->subscribe(Listener\AddDiscussionSubscriptionAttribute::class);
+    $events->subscribe(Listener\ConfigureFollowAfterReplyUserPreferences::class);
     $events->subscribe(Listener\FilterDiscussionListBySubscription::class);
     $events->subscribe(Listener\SaveSubscriptionToDatabase::class);
     $events->subscribe(Listener\SendNotificationWhenReplyIsPosted::class);
+    $events->subscribe(Listener\SubscribeWhenPostWasPosted::class);
 
-    $views->addNamespace('flarum-subscriptions', __DIR__.'/views');
-};
+    $views->addNamespace('flarum-subscriptions', __DIR__ . '/views');
+};

src/Listener/ConfigureFollowAfterReplyUserPreferences.php

@@ -0,0 +1,35 @@
+<?php
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Subscriptions\Listener;
+
+use Flarum\Api\Serializer\DiscussionSerializer;
+use Flarum\Event\ConfigureUserPreferences;
+use Flarum\Event\PrepareApiAttributes;
+use Illuminate\Contracts\Events\Dispatcher;
+
+class ConfigureFollowAfterReplyUserPreferences
+{
+    /**
+     * @param Dispatcher $events
+     */
+    public function subscribe(Dispatcher $events)
+    {
+        $events->listen(ConfigureUserPreferences::class, [$this, 'addUserPreference']);
+    }
+
+    /**
+     * @param ConfigureUserPreferences $event
+     */
+    public function addUserPreference(ConfigureUserPreferences $event)
+    {
+        $event->add('followAfterReply', 'boolval', true);
+    }
+}

src/Listener/SubscribeWhenPostWasPosted.php

@@ -0,0 +1,50 @@
+<?php
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Subscriptions\Listener;
+
+use Flarum\Core\Access\AssertPermissionTrait;
+use Flarum\Event\DiscussionWillBeSaved;
+use Flarum\Event\PostWasPosted;
+use Illuminate\Contracts\Events\Dispatcher;
+
+class SubscribeWhenPostWasPosted
+{
+    use AssertPermissionTrait;
+
+    /**
+     * @param Dispatcher $events
+     */
+    public function subscribe(Dispatcher $events)
+    {
+        $events->listen(PostWasPosted::class, [$this, 'whenPostWasPosted']);
+    }
+
+    /**
+     * @param PostWasPosted $event
+     */
+    public function whenPostWasPosted(PostWasPosted $event)
+    {
+        $actor = $event->actor;
+
+        if ($actor && $actor->exists && $actor->getPreference('followAfterReply')) {
+
+            $post = $event->post;
+            $discussion = $post->discussion;
+
+            $this->assertRegistered($actor);
+
+            $state = $discussion->stateFor($actor);
+
+            $state->subscription = 'follow';
+            $state->save();
+        }
+    }
+}