/**
* @author       Richard Davey <rich@photonstorm.com>
* @copyright    2013 Photon Storm Ltd.
* @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
*/

/**
* A basic linked list data structure.
*
* @class Phaser.LinkedList
* @constructor
*/
Phaser.LinkedList = function () {

    /**
	* @property {object} next - Next element in the list.
	* @default
	*/
    this.next = null;

    /**
	* @property {object} prev - Previous element in the list.
	* @default
	*/
    this.prev = null;

    /**
	* @property {object} first - First element in the list.
	* @default
	*/
    this.first = null;

    /**
	* @property {object} last - Last element in the list.
	* @default
	*/
    this.last = null;
    
    /**
	* @property {object} game - Number of elements in the list.
	* @default
	*/
    this.total = 0;

};

Phaser.LinkedList.prototype = {

	/**
    * Adds a new element to this linked list.
	* 
	* @method Phaser.LinkedList#add
	* @param {object} child - The element to add to this list. Can be a Phaser.Sprite or any other object you need to quickly iterate through.
	* @return {object} The child that was added.
    */
    add: function (child) {

    	//	If the list is empty
    	if (this.total == 0 && this.first == null && this.last == null)
    	{
    		this.first = child;
    		this.last = child;
	    	this.next = child;
	    	child.prev = this;
	    	this.total++;
    		return child;
    	}

    	//	Get gets appended to the end of the list, regardless of anything, and it won't have any children of its own (non-nested list)
    	this.last.next = child;

    	child.prev = this.last;

    	this.last = child;

		this.total++;

		return child;

    },

	/**
    * Removes the given element from this linked list if it exists.
 	* 
 	* @method Phaser.LinkedList#remove
 	* @param {object} child - The child to be removed from the list.
    */
    remove: function (child) {

    	if (child == this.first)
    	{
			// It was 'first', make 'first' point to first.next
    		this.first = this.first.next;
    	}      
		else if (child == this.last)
		{
			// It was 'last', make 'last' point to last.prev
			this.last = this.last.prev;
		} 

		if (child.prev)
		{
			// make child.prev.next point to childs.next instead of child
			child.prev.next = child.next; 
		} 

		if (child.next)
		{
			// make child.next.prev point to child.prev instead of child
			child.next.prev = child.prev;
		}

		child.next = child.prev = null;

		if (this.first == null )
		{
			this.last = null;
		}

		this.total--;

    },

	/**
    * Calls a function on all members of this list, using the member as the context for the callback.
    * The function must exist on the member.
  	* 
  	* @method Phaser.LinkedList#callAll
  	* @param {function} callback - The function to call.
    */
    callAll: function (callback) {

    	if (!this.first || !this.last)
    	{
    		return;
    	}

		var entity = this.first;
		
		do	
		{
			if (entity && entity[callback])
			{
				entity[callback].call(entity);
			}

			entity = entity.next;

		}
		while(entity != this.last.next)			

    }

};