Allow author to delete discussion if there are no replies

Also disallow the first post in a discussion to be deleted or hidden
(thus preventing discussions with zero posts)

closes flarum/core#90 closes flarum/core#92

src/Core/Handlers/Commands/EditPostCommandHandler.php

@@ -3,6 +3,7 @@
 use Flarum\Core\Repositories\PostRepositoryInterface as PostRepository;
 use Flarum\Core\Events\PostWillBeSaved;
 use Flarum\Core\Support\DispatchesEvents;
+use Flarum\Core\Models\CommentPost;
 
 class EditPostCommandHandler
 {
@@ -22,15 +23,17 @@ class EditPostCommandHandler
 
         $post->assertCan($user, 'edit');
 
-        if (isset($command->data['content'])) {
-            $post->revise($command->data['content'], $user);
-        }
+        if ($post instanceof CommentPost) {
+            if (isset($command->data['content'])) {
+                $post->revise($command->data['content'], $user);
+            }
 
-        if (isset($command->data['isHidden'])) {
-            if ($command->data['isHidden']) {
-                $post->hide($user);
-            } else {
-                $post->restore($user);
+            if (isset($command->data['isHidden'])) {
+                if ($command->data['isHidden']) {
+                    $post->hide($user);
+                } else {
+                    $post->restore($user);
+                }
             }
         }
 

src/Core/Handlers/Events/DiscussionMetadataUpdater.php

@@ -28,6 +28,7 @@ class DiscussionMetadataUpdater
 
         $discussion->comments_count++;
         $discussion->setLastPost($event->post);
+        $discussion->refreshParticipantsCount();
         $discussion->save();
     }
 
@@ -46,6 +47,7 @@ class DiscussionMetadataUpdater
         $discussion = $event->post->discussion;
 
         $discussion->refreshCommentsCount();
+        $discussion->refreshParticipantsCount();
         $discussion->refreshLastPost();
         $discussion->save();
     }
@@ -56,6 +58,7 @@ class DiscussionMetadataUpdater
 
         if ($discussion->exists) {
             $discussion->refreshCommentsCount();
+            $discussion->refreshParticipantsCount();
 
             if ($discussion->last_post_id == $post->id) {
                 $discussion->refreshLastPost();

src/Core/Models/CommentPost.php

@@ -5,6 +5,7 @@ use Flarum\Core\Events\PostWasPosted;
 use Flarum\Core\Events\PostWasRevised;
 use Flarum\Core\Events\PostWasHidden;
 use Flarum\Core\Events\PostWasRestored;
+use Flarum\Core\Exceptions\ValidationFailureException;
 
 class CommentPost extends Post
 {
@@ -75,6 +76,10 @@ class CommentPost extends Post
      */
     public function hide($user)
     {
+        if ($this->number == 1) {
+            throw new ValidationFailureException;
+        }
+
         if (! $this->hide_time) {
             $this->hide_time = time();
             $this->hide_user_id = $user->id;
@@ -93,6 +98,10 @@ class CommentPost extends Post
      */
     public function restore($user)
     {
+        if ($this->number == 1) {
+            throw new ValidationFailureException;
+        }
+
         if ($this->hide_time !== null) {
             $this->hide_time = null;
             $this->hide_user_id = null;

src/Core/Models/Discussion.php

@@ -20,15 +20,16 @@ class Discussion extends Model
      * @var array
      */
     public static $rules = [
-        'title'            => 'required',
-        'start_time'       => 'required|date',
-        'comments_count'   => 'integer',
-        'start_user_id'    => 'integer',
-        'start_post_id'    => 'integer',
-        'last_time'        => 'date',
-        'last_user_id'     => 'integer',
-        'last_post_id'     => 'integer',
-        'last_post_number' => 'integer'
+        'title'              => 'required',
+        'start_time'         => 'required|date',
+        'comments_count'     => 'integer',
+        'participants_count' => 'integer',
+        'start_user_id'      => 'integer',
+        'start_post_id'      => 'integer',
+        'last_time'          => 'date',
+        'last_user_id'       => 'integer',
+        'last_post_id'       => 'integer',
+        'last_post_number'   => 'integer'
     ];
 
     protected static $relationships = [];
@@ -175,6 +176,18 @@ class Discussion extends Model
         return $this;
     }
 
+    /**
+     * Refresh the discussion's participants count.
+     *
+     * @return $this
+     */
+    public function refreshParticipantsCount()
+    {
+        $this->participants_count = $this->participants()->count('users.id');
+
+        return $this;
+    }
+
     /**
      * Specify that a post was added to this discussion during this request
      * for later retrieval.
@@ -255,6 +268,16 @@ class Discussion extends Model
         return $this->posts()->where('type', 'comment')->whereNull('hide_time');
     }
 
+    /**
+     * Define the relationship with the discussion's participants.
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\HasMany
+     */
+    public function participants()
+    {
+        return User::join('posts', 'posts.user_id', '=', 'users.id')->where('posts.discussion_id', $this->id)->select('users.*')->distinct();
+    }
+
     /**
      * Define the relationship with the discussion's first post.
      *

src/Core/Models/Post.php

@@ -2,6 +2,7 @@
 
 use Flarum\Core\Events\PostWasDeleted;
 use Flarum\Core\Support\Locked;
+use Flarum\Core\Exceptions\ValidationFailureException;
 
 class Post extends Model
 {
@@ -74,6 +75,12 @@ class Post extends Model
             $post->discussion->save();
         });
 
+        static::deleting(function ($post) {
+            if ($post->number == 1) {
+                throw new ValidationFailureException;
+            }
+        });
+
         static::deleted(function ($post) {
             $post->raise(new PostWasDeleted($post));
         });