<?php

class SortableDataObject extends DataObjectDecorator
{
	
	static $sortable_classes = array();
	static $many_many_sortable_relations = array();
	static $sort_dir = "ASC";
	
	public static function set_sort_dir($dir)
	{
		self::$sort_dir = $dir;
	}
	
	
	public static function add_sortable_class($className)
	{
		if(!self::is_sortable_class($className)) {
  		DataObject::add_extension($className,'SortableDataObject');
  		self::$sortable_classes[] = $className;
		}
	}
	
	public function extraStatics()
	{
		return array (
			'db' => array (
				'SortOrder' => 'Int'
			)
		);
	}
	
	
	public static function add_sortable_classes(array $classes)
	{
		foreach($classes as $class) 
			self::add_sortable_class($class);
	}
	
	public static function add_sortable_many_many_relation($ownerClass,$componentName)
	{

    list($parentClass, $componentClass, $parentField, $componentField, $table) = singleton($ownerClass)->many_many($componentName);
    Object::add_static_var($ownerClass,'many_many_extraFields',array(
      $componentName => array(
        'SortOrder' => 'Int'
     )));
    if(!isset(self::$many_many_sortable_relations[$componentClass]))
      self::$many_many_sortable_relations[$componentClass] = array();
      
    self::$many_many_sortable_relations[$componentClass][$parentClass] = $table;
    self::add_sortable_class($componentClass);
	} 
	
	public static function remove_sortable_class($class)
	{
		Object::remove_extension($class, 'SortableDataObject');
	}
	
	public static function is_sortable_class($classname)
	{
		if(in_array($classname, self::$sortable_classes))
			return true;
		foreach(self::$sortable_classes as $class) {
			if(is_subclass_of($classname, $class))
				return true;
		}
		return false;
			
	}
	
	public static function is_sortable_many_many($componentClass, $parentClass = null)
	{
     $map = self::$many_many_sortable_relations;
	   if($parentClass === null)
  	   return isset($map[$componentClass]);
  	 else {
  	   if(isset($map[$componentClass]))
  	     return isset($map[$componentClass][$parentClass]);
  	   return false;
    }

	}
	
	public static function get_join_tables($classname)
	{
	   if(isset(self::$many_many_sortable_relations[$classname]))
	     return self::$many_many_sortable_relations[$classname];
	   return false;
	}
	
	
	public function augmentSQL(SQLQuery &$query)
	{
	   if(empty($query->select) || $query->delete) return;
	   $sort_field = false;
	   if($join_tables = self::get_join_tables($this->owner->class)) {
       foreach($query->from as $from) {
          if($sort_field) break;
          foreach($join_tables as $join_table) {
            if(stristr($from,$join_table)) {
              $sort_field = "`$join_table`.SortOrder";
              break;
            }
          }
       }
	   }
	   if(!$sort_field) $sort_field = "SortOrder";
	   
	   if(!$query->orderby || ($query->orderby == $this->owner->stat('default_sort')))
	     $query->orderby = "$sort_field " . self::$sort_dir;
	}

 	public function onBeforeWrite()
	{
		if(!$this->owner->ID) {
			if($peers = DataObject::get($this->owner->class))
				$this->owner->SortOrder = $peers->Count()+1;
		}
	}	

}