class Tag_Model extends Model
{
    public function get_related_tags( $tags )
    {
        ## Get db entries with specific tags and build array with counts

        ## is it cached already? ------------------------------------------------
        $this->cache = Cache::instance();
        $tags = array_filter( array_flip(array_flip($tags)) );
        sort($tags);
        $cache_name = implode('', $tags);
        $cache = $this->cache->get( $cache_name );
         
        if( $cache )
         return $cache;
 
        ## not cached, fire up ---------------------------------------------------
 
        $db = Database::instance();
        
        ## count tagged items ----------------------------------------------------

        // build like string
        $like = array();
        foreach( $tags as $tag )
           $like[] = "tags LIKE '%$tag%'";
        
        $like = implode(' AND ', $like);
        
        // get counts
        $count = $db->query("SELECT count(id) AS count FROM `articles` WHERE $like")->current()->count;
        
        ## check what tags are related ------------------------------------------
 
        $offset = 0;
        $step = 300;
        
        $related_tags = array();
        
        while( $offset < $count )
		{
            $assets = $db->query("SELECT tags FROM `articles` WHERE $like ORDER BY id ASC LIMIT $step OFFSET $offset");
        
            foreach($assets as $asset)
			{
                // tags 
                $input = explode( ' ', trim($asset->tags) );
                foreach( $input as $k => $v )
				{
                     if( $v == ''){
                         //do nothing, shouldnt be here anyway
                     }
                     elseif( array_key_exists($v, $related_tags) ){
                         $related_tags[$v]++;
                     }
                     else{
                        $related_tags[$v] = 1;
                     }        
                }
            }
            $offset += $step;
        }
 
        // remove already displayed from list
        foreach( $tags as $tag )
            unset( $related_tags[$tag] );
        
        ksort($related_tags);

        // set cache 
        $this->cache->set( $cache_name, array($related_tags, $count), 'related_tags_counts', 0);
        
        return array($related_tags, $count);
    }

	public function update_tags( $tags, $saved_tags )
	{		
		// make array if not already
		if( ! is_array($tags) )
		{
			$tags = explode(' ', trim($tags) );
		}
		
		if( ! is_array($saved_tags) )
		{
			$saved_tags = explode(' ', trim($saved_tags) );
		}
		
		// find new tags
		$new_tags = array_filter( array_diff($tags, $saved_tags) );
		
			// update counts
			if( count($new_tags) > 0 )
			{
				$this->add_tags($new_tags);
			}	
		
		// find removed tags
		$removed_tags = array_filter( array_diff($saved_tags, $tags) );
	
			// update counts
			if( count($removed_tags) > 0 )
			{
				$this->remove_tags($removed_tags);		
			}
	}
	
	private function add_tags( $new_tags )
	{
		$db = Database::instance();
	
		// check if tags are new system wide
		// try to load all and then compare
		$tags_db = array();		
		$tags_in_db = $db->in('tag_name', $new_tags)->get('tags');
		
		foreach( $tags_in_db as $t )
		{
			$tags_db[] = $t->tag_name;
		}
		
		$system_new_tags = array_filter( array_diff($new_tags, $tags_db) );	
	
		// insert new tags to db if necessary
		if( count($system_new_tags) > 0 )
		{
			$tag_array = array();
			foreach( $system_new_tags as $t )
			{
				$tag_array[] = "('$t')";
			}
			
			$tag_str = implode(',', $tag_array);
					
			$sql = "INSERT INTO tags (tag_name) VALUES $tag_str";
			$db->query($sql);
		}	
			
		// update counts
		$tag_array = array();
		foreach( $new_tags as $t )
		{
			$tag_array[] = "'$t'";
		}
		
		$tag_str = implode(',', $tag_array);
		
		$sql = "UPDATE tags SET `tag_count`=`tag_count`+1 WHERE `tag_name` IN ($tag_str)";
		$db->query($sql);
	}
	
	private function remove_tags( $removed_tags )
	{
		$db = Database::instance();

		// update counts
		$tag_array = array();
		foreach( $removed_tags as $t )
		{
			$tag_array[] = "'$t'";
		}
		
		$tag_str = implode(',', $tag_array);
		
		$sql = "UPDATE tags SET `tag_count`=`tag_count`-1 WHERE `tag_name` IN ($tag_str)";
		$db->query($sql);		
	}
	
}