/*
* Copyright (c) 2006-2007 Erin Catto http:
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked, and must not be
* misrepresented the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/




/**
 * @class b2Mat22
 * @constructor
 * @param angle
 * @param c1
 * @param c2
 */
var b2Mat22 = function (angle, c1, c2) {
	if (angle==null) angle = 0;
	// initialize instance variables for references
	this.col1 = new b2Vec2();
	this.col2 = new b2Vec2();
	//

	if (c1!=null && c2!=null){
		this.col1.SetV(c1);
		this.col2.SetV(c2);
	}
	else{
		var c = Math.cos(angle);
		var s = Math.sin(angle);
		this.col1.x = c; this.col2.x = -s;
		this.col1.y = s; this.col2.y = c;
	}
};

b2Mat22.prototype = 
{
	Set: function(angle)
	{
		var c = Math.cos(angle);
		var s = Math.sin(angle);
		this.col1.x = c; this.col2.x = -s;
		this.col1.y = s; this.col2.y = c;
	},

	SetVV: function(c1, c2)
	{
		this.col1.SetV(c1);
		this.col2.SetV(c2);
	},

	Copy: function(){
		return new b2Mat22(0, this.col1, this.col2);
	},

	SetM: function(m)
	{
		this.col1.SetV(m.col1);
		this.col2.SetV(m.col2);
	},

	AddM: function(m)
	{
		this.col1.x += m.col1.x;
		this.col1.y += m.col1.y;
		this.col2.x += m.col2.x;
		this.col2.y += m.col2.y;
	},

	SetIdentity: function()
	{
		this.col1.x = 1.0; this.col2.x = 0.0;
		this.col1.y = 0.0; this.col2.y = 1.0;
	},

	SetZero: function()
	{
		this.col1.x = 0.0; this.col2.x = 0.0;
		this.col1.y = 0.0; this.col2.y = 0.0;
	},

	Invert: function(out)
	{
		var a = this.col1.x;
		var b = this.col2.x;
		var c = this.col1.y;
		var d = this.col2.y;
		//var B = new b2Mat22();
		var det = a * d - b * c;
		//b2Settings.b2Assert(det != 0.0);
		det = 1.0 / det;
		out.col1.x =  det * d;	out.col2.x = -det * b;
		out.col1.y = -det * c;	out.col2.y =  det * a;
		return out;
	},

	// this.Solve A * x = b
	Solve: function(out, bX, bY)
	{
		//float32 a11 = this.col1.x, a12 = this.col2.x, a21 = this.col1.y, a22 = this.col2.y;
		var a11 = this.col1.x;
		var a12 = this.col2.x;
		var a21 = this.col1.y;
		var a22 = this.col2.y;
		//float32 det = a11 * a22 - a12 * a21;
		var det = a11 * a22 - a12 * a21;
		//b2Settings.b2Assert(det != 0.0);
		det = 1.0 / det;
		out.x = det * (a22 * bX - a12 * bY);
		out.y = det * (a11 * bY - a21 * bX);

		return out;
	},

	Abs: function()
	{
		this.col1.Abs();
		this.col2.Abs();
	},

	col1: new b2Vec2(),
	col2: new b2Vec2()
};