From 56ef42f93179316e341a7417be76e46dc4adcc18 Mon Sep 17 00:00:00 2001
From: Toby Zerner <toby.zerner@gmail.com>
Date: Mon, 4 May 2015 12:19:25 +0930
Subject: [PATCH] Add concept of "mergeable" activity posts

For example: when you rename a discussion, DiscussionRenamedPost is
created. If you rename it again immediately afterwards, then a new
DiscussionRenamedPost can be merged into the old one. This will either
result in the old one being updated with the new title, or it being
deleted all together if it was renamed back to the old title.
---
 .../Events/DiscussionRenamedNotifier.php      |  8 +---
 src/Core/Models/ActivityPost.php              | 27 ++++++++++++
 src/Core/Models/Discussion.php                | 18 ++++++++
 src/Core/Models/DiscussionRenamedPost.php     | 41 +++++++++++--------
 src/Core/Models/MergeableInterface.php        |  6 +++
 src/Core/Models/MergeableTrait.php            | 23 +++++++++++
 6 files changed, 100 insertions(+), 23 deletions(-)
 create mode 100755 src/Core/Models/ActivityPost.php
 create mode 100644 src/Core/Models/MergeableInterface.php
 create mode 100644 src/Core/Models/MergeableTrait.php

diff --git a/src/Core/Handlers/Events/DiscussionRenamedNotifier.php b/src/Core/Handlers/Events/DiscussionRenamedNotifier.php
index f989cc07c..5b985198c 100755
--- a/src/Core/Handlers/Events/DiscussionRenamedNotifier.php
+++ b/src/Core/Handlers/Events/DiscussionRenamedNotifier.php
@@ -27,7 +27,7 @@ class DiscussionRenamedNotifier
     {
         $post = $this->createPost($event);
 
-        $event->discussion->postWasAdded($post);
+        $event->discussion->addPost($post);
 
         if ($event->discussion->start_user_id !== $event->user->id) {
             $this->sendNotification($event, $post);
@@ -36,16 +36,12 @@ class DiscussionRenamedNotifier
 
     protected function createPost(DiscussionWasRenamed $event)
     {
-        $post = DiscussionRenamedPost::reply(
+        return DiscussionRenamedPost::reply(
             $event->discussion->id,
             $event->user->id,
             $event->oldTitle,
             $event->discussion->title
         );
-
-        $post->save();
-
-        return $post;
     }
 
     protected function sendNotification(DiscussionWasRenamed $event, DiscussionRenamedPost $post)
diff --git a/src/Core/Models/ActivityPost.php b/src/Core/Models/ActivityPost.php
new file mode 100755
index 000000000..0b0413979
--- /dev/null
+++ b/src/Core/Models/ActivityPost.php
@@ -0,0 +1,27 @@
+<?php namespace Flarum\Core\Models;
+
+abstract class ActivityPost extends Post implements MergeableInterface
+{
+    use MergeableTrait;
+
+    /**
+     * Unserialize the content attribute.
+     *
+     * @param  string  $value
+     * @return string
+     */
+    public function getContentAttribute($value)
+    {
+        return json_decode($value);
+    }
+
+    /**
+     * Serialize the content attribute.
+     *
+     * @param  string  $value
+     */
+    public function setContentAttribute($value)
+    {
+        $this->attributes['content'] = json_encode($value);
+    }
+}
diff --git a/src/Core/Models/Discussion.php b/src/Core/Models/Discussion.php
index d3c26e2d9..2e0b0bc6f 100755
--- a/src/Core/Models/Discussion.php
+++ b/src/Core/Models/Discussion.php
@@ -185,6 +185,24 @@ class Discussion extends Model
         $this->removedPosts[] = $post->id;
     }
 
+    public function addPost(Post $post)
+    {
+        if ($post instanceof MergeableInterface) {
+            $lastPost = $this->posts()->orderBy('time', 'desc')->first();
+            $post = $post->saveAfter($lastPost);
+        } else {
+            $post->save();
+        }
+
+        if ($post->exists) {
+            $this->postWasAdded($post);
+        } else {
+            $this->postWasRemoved($post);
+        }
+
+        return $post->exists;
+    }
+
     /**
      * Define the relationship with the discussion's posts.
      *
diff --git a/src/Core/Models/DiscussionRenamedPost.php b/src/Core/Models/DiscussionRenamedPost.php
index 38ce65a9b..d10231ee7 100755
--- a/src/Core/Models/DiscussionRenamedPost.php
+++ b/src/Core/Models/DiscussionRenamedPost.php
@@ -1,7 +1,23 @@
 <?php namespace Flarum\Core\Models;
 
-class DiscussionRenamedPost extends Post
+class DiscussionRenamedPost extends ActivityPost
 {
+    /**
+     * Merge the post into another post of the same type.
+     *
+     * @param \Flarum\Core\Models\DiscussionRenamedPost $previous
+     * @return boolean true if the post was merged, false if it was deleted.
+     */
+    protected function mergeInto(Model $previous)
+    {
+        if ($previous->content[0] == $this->content[1]) {
+            return false;
+        }
+
+        $previous->content = static::buildContent($previous->content[0], $this->content[1]);
+        return true;
+    }
+
     /**
      * Create a new instance in reply to a discussion.
      *
@@ -15,7 +31,7 @@ class DiscussionRenamedPost extends Post
     {
         $post = new static;
 
-        $post->content       = [$oldTitle, $newTitle];
+        $post->content       = static::buildContent($oldTitle, $newTitle);
         $post->time          = time();
         $post->discussion_id = $discussionId;
         $post->user_id       = $userId;
@@ -25,23 +41,14 @@ class DiscussionRenamedPost extends Post
     }
 
     /**
-     * Unserialize the content attribute.
+     * Build the content attribute.
      *
-     * @param  string  $value
-     * @return string
+     * @param boolean $oldTitle The old title of the discussion.
+     * @param boolean $newTitle The new title of the discussion.
+     * @return array
      */
-    public function getContentAttribute($value)
+    public static function buildContent($oldTitle, $newTitle)
     {
-        return json_decode($value);
-    }
-
-    /**
-     * Serialize the content attribute.
-     *
-     * @param  string  $value
-     */
-    public function setContentAttribute($value)
-    {
-        $this->attributes['content'] = json_encode($value);
+        return [$oldTitle, $newTitle];
     }
 }
diff --git a/src/Core/Models/MergeableInterface.php b/src/Core/Models/MergeableInterface.php
new file mode 100644
index 000000000..2a6c81ccf
--- /dev/null
+++ b/src/Core/Models/MergeableInterface.php
@@ -0,0 +1,6 @@
+<?php namespace Flarum\Core\Models;
+
+interface MergeableInterface
+{
+    public function saveAfter(Model $previous);
+}
diff --git a/src/Core/Models/MergeableTrait.php b/src/Core/Models/MergeableTrait.php
new file mode 100644
index 000000000..7d11defeb
--- /dev/null
+++ b/src/Core/Models/MergeableTrait.php
@@ -0,0 +1,23 @@
+<?php namespace Flarum\Core\Models;
+
+trait MergeableTrait
+{
+    public function saveAfter(Model $previous)
+    {
+        if ($previous instanceof static) {
+            if ($this->mergeInto($previous)) {
+                $previous->save();
+            } else {
+                $previous->delete();
+            }
+
+            return $previous;
+        }
+
+        $this->save();
+
+        return $this;
+    }
+
+    abstract protected function mergeInto(Model $previous);
+}