/**
 * Copyright (c) 2006 Peter Goodman
 * Licensed under the MIT License:
 * http://www.opensource.org/licenses/mit-license.php
 */

//--------------------------------------------
// A class for dealing with associative stacks.
// Think of how a normal stack would work in php
// with an associative array. This mimicks that
// although the process is much more involved.
//--------------------------------------------

class FA.Stack
{
	private var stack_object:Object = { }
	private var stack_keys:Array = [ ];
	private var stack_vals:Array = [ ];
	
	//--------------------------------------------
	// Push a value on to the end of the stack
	//--------------------------------------------
	
	public function push (key:String, value, _index) : Void
	{
		var index:Number = _index == undefined ? stack_keys.length : _index;
		
		if (stack_object[key] != undefined)
		{
			index = stack_object[key];
		}
		
		// this is such an annoying thing to do to
		// get _all_ the functionality I want.
		stack_vals[index] = value;
		stack_keys[index] = key;
		stack_object[key] = index;
	}
	
	//--------------------------------------------
	// Get a value and delete all stuff relating to it
	// in the stack.
	//--------------------------------------------
	
	private function _get (index:Number)
	{
		var ret;
		
		if (stack_keys[index] != undefined)
		{
			ret = stack_vals[index];
			
			// delete the stuff off of the end of the array
			delete stack_object[stack_keys[index]];
			delete stack_keys[index];
			delete stack_vals[index];
		}
		return ret;
	}
	
	//--------------------------------------------
	// Pop a value off of the end of the stack.
	//--------------------------------------------
	
	public function pop ()
	{
		//return this._get(stack_keys.length);
		var index:Number;
		var ret;
		
		for (index = stack_keys.length-1; index >= 0; index--)
		{
			ret = this._get(index);
			break;
		}
		
		return ret;
	}
	
	//--------------------------------------------
	// Shift a value off of the start of the stack.
	//--------------------------------------------
	
	public function shift ()
	{
		var ret;
		var index:Number;
		
		for (index in stack_keys)
		{
			ret = this._get(index);
			break;
		}
		return ret;
	}
	
	//--------------------------------------------
	// Insert a value (and key) onto the start of the
	// stack. The hope is this function will never be 
	// used :P
	//--------------------------------------------
	 
	public function unshift (key:String, value) : Void
	{
		var index:Number;
		
		// oof, this is an ugly thing to do, we need to
		// change all of the keys in the the arrays.
		for (index = stack_keys.length-1; index >= 0; index--)
		{
			if(stack_keys[index] != undefined)
			{
				stack_object[stack_keys[index]] = index+1;
				stack_keys[index+1] = stack_keys[index];
				stack_vals[index+1] = stack_vals[index];
			
				// this serves to delete all the old stuff.
				this._get(index);
			}
		}
		
		// unshift the value :D
		this.push(key, value, 0);
	}
	
	//--------------------------------------------
	// Get a value from the stack by the key that
	// it was assigned.
	//--------------------------------------------
	
	public function get (key:String)
	{
		var ret;
		
		if (stack_object[key] != undefined)
		{
			ret = stack_vals[stack_object[key]];
		}
		
		return ret;
	}
	
	//--------------------------------------------
	// Just another name for the 'push' function.
	//--------------------------------------------
	
	public function set (key, value) : Void
	{
		this.push(key, value);
	}
}