Store discussion slug in database table

In preparation for #646.

js/lib/models/Discussion.js

@@ -2,14 +2,13 @@ import Model from 'flarum/Model';
 import mixin from 'flarum/utils/mixin';
 import computed from 'flarum/utils/computed';
 import ItemList from 'flarum/utils/ItemList';
-import { slug } from 'flarum/utils/string';
 import Badge from 'flarum/components/Badge';
 
 export default class Discussion extends Model {}
 
 Object.assign(Discussion.prototype, {
   title: Model.attribute('title'),
-  slug: computed('title', slug),
+  slug: Model.attribute('slug'),
 
   startTime: Model.attribute('startTime', Model.transformDate),
   startUser: Model.hasOne('startUser'),

migrations/2016_02_04_095452_add_slug_to_discussions.php

@@ -0,0 +1,41 @@
+<?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\Core\Migration;
+
+use Flarum\Core\Discussion;
+use Flarum\Database\AbstractMigration;
+use Flarum\Util\Str;
+use Illuminate\Database\Schema\Blueprint;
+
+class AddSlugToDiscussions extends AbstractMigration
+{
+    public function up()
+    {
+        $this->schema->table('discussions', function (Blueprint $table) {
+            $table->string('slug');
+        });
+
+        // Store slugs for existing discussions
+        Discussion::chunk(100, function ($discussions) {
+            foreach ($discussions as $discussion) {
+                $discussion->slug = Str::slug($discussion->title);
+                $discussion->save();
+            }
+        });
+    }
+
+    public function down()
+    {
+        $this->schema->table('discussions', function (Blueprint $table) {
+            $table->dropColumn('slug');
+        });
+    }
+}

src/Api/Serializer/DiscussionBasicSerializer.php

@@ -34,7 +34,8 @@ class DiscussionBasicSerializer extends AbstractSerializer
         }
 
         return [
-            'title' => $discussion->title
+            'title' => $discussion->title,
+            'slug'  => $discussion->slug,
         ];
     }
 

src/Core/Discussion.php

@@ -22,10 +22,12 @@ use Flarum\Event\DiscussionWasRestored;
 use Flarum\Event\DiscussionWasStarted;
 use Flarum\Event\PostWasDeleted;
 use Flarum\Event\ScopePostVisibility;
+use Flarum\Util\Str;
 
 /**
  * @property int $id
  * @property string $title
+ * @property string $slug
  * @property int $comments_count
  * @property int $participants_count
  * @property int $number_index
@@ -432,4 +434,17 @@ class Discussion extends AbstractModel
     {
         static::$stateUser = $user;
     }
+
+    /**
+     * Set the discussion title.
+     *
+     * This automatically creates a matching slug for the discussion.
+     *
+     * @param string $title
+     */
+    protected function setTitleAttribute($title)
+    {
+        $this->attributes['title'] = $title;
+        $this->slug = Str::slug($title);
+    }
 }

src/Util/Str.php

@@ -0,0 +1,32 @@
+<?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\Util;
+
+class Str
+{
+    /**
+     * Create a slug out of the given string.
+     *
+     * Non-alphanumeric characters are converted to hyphens.
+     *
+     * @param string $str
+     * @return string
+     */
+    public static function slug($str)
+    {
+        $str = strtolower($str);
+        $str = preg_replace('/[^a-z0-9]/i', '-', $str);
+        $str = preg_replace('/-+/', '-', $str);
+        $str = preg_replace('/-$|^-/', '', $str);
+
+        return $str ?: '-';
+    }
+}