use model observer to manage tagging of notes

app/Note.php

@@ -462,7 +462,7 @@ class Note extends Model
                 $name = str_replace('#', '', $name);
                 $replacements[$name] =
                   '<a rel="tag" class="p-category" href="/notes/tagged/'
-                    . Tag::normalizeTag($name)
+                    . Tag::normalize($name)
                     . '">#'
                     . $name
                     . '</a>';

app/Observers/NoteObserver.php

@@ -0,0 +1,76 @@
+<?php
+
+namespace App\Observers;
+
+use App\{Note, Tag};
+
+class NoteObserver
+{
+    /**
+     * Listen to the Note created event.
+     *
+     * @param  \App\Note  $note
+     * @return void
+     */
+    public function created(Note $note)
+    {
+        $tags = $this->getTagsFromNote($note->getAttributes()['note']);
+
+        if (count($tags) === 0) {
+            return;
+        }
+
+        $tags->transform(function ($tag) {
+            return Tag::firstOrCreate(['tag' => $tag]);
+        });
+
+        $note->tags()->attach($tags->map(function ($tag) {
+            return $tag->id;
+        }));
+    }
+
+    /**
+     * Listen to the Note updated event.
+     *
+     * @param  \App\Note  $Note
+     * @return void
+     */
+    public function updated(Note $note)
+    {
+        $tags = $this->getTagsFromNote($note->getAttributes()['note']);
+        if (count($tags) === 0) {
+            return;
+        }
+
+        $tags->transform(function ($tag) {
+            return Tag::firstOrCreate(['tag' => $tag]);
+        });
+
+        $note->tags()->sync($tags->map(function ($tag) {
+            return $tag->id;
+        }));
+    }
+
+    /**
+     * Listen to the Note deleting event.
+     *
+     * @param  \App\Note  $note
+     * @return void
+     */
+    public function deleting(Note $note)
+    {
+        $note->tags()->detach();
+    }
+
+    public function getTagsFromNote($note)
+    {
+        preg_match_all('/#([^\s<>]+)\b/', $note, $tags);
+        if (array_get($tags, '1') === null) {
+            return [];
+        }
+
+        return collect($tags[1])->map(function ($tag) {
+            return Tag::normalize($tag);
+        })->unique();
+    }
+}

app/Tag.php

@@ -6,13 +6,6 @@ use Illuminate\Database\Eloquent\Model;
 
 class Tag extends Model
 {
-    /**
-     * The database table used by the model.
-     *
-     * @var string
-     */
-    protected $table = 'tags';
-
     /**
      * Define the relationship with tags.
      *
@@ -31,13 +24,6 @@ class Tag extends Model
         return $this->belongsToMany('App\Bookmark');
     }
 
-    /**
-     * The attributes excluded from the model's JSON form.
-     *
-     * @var array
-     */
-    protected $hidden = ['deleted'];
-
     /**
      * We shall set a blacklist of non-modifiable model attributes.
      *
@@ -52,7 +38,7 @@ class Tag extends Model
      */
     public function setTagAttribute($value)
     {
-        $this->attributes['tag'] = $this->normalizeTag($value);
+        $this->attributes['tag'] = $this->normalize($value);
     }
 
     /**
@@ -61,7 +47,7 @@ class Tag extends Model
      *
      * @param  string
      */
-    public static function normalizeTag($tag)
+    public static function normalize($tag)
     {
         return mb_strtolower(
             preg_replace(