var math = require('../../../math'),
    utils = require('../../../utils'),
    CONST = require('../../../const'),
    //StencilManager = require('../managers/StencilManager'),
    StencilMaskStack = require('./StencilMaskStack');

/**
 * @author Mat Groves http://matgroves.com/ @Doormat23
 */

/**
 * @class
 * @memberof PIXI
 * @param gl {WebGLRenderingContext} the current WebGL drawing context
 * @param width {number} the horizontal range of the filter
 * @param height {number} the vertical range of the filter
 * @param scaleMode {number} See {{#crossLink "PIXI/scaleModes:property"}}PIXI.scaleModes{{/crossLink}} for possible values
 * @param resolution {number} the current resolution
 * @param root {boolean} Whether this object is the root element or not
 */
var RenderTarget = function(gl, width, height, scaleMode, resolution, root)
{
    //TODO Resolution could go here ( eg low res blurs )

    /**
     * The current WebGL drawing context
     * @member {WebGLRenderingContext}
     */
    this.gl = gl;

    // next time to create a frame buffer and texture

    /**
     * A frame buffer
     * @member {WebGLFrameBuffer}
     */
    this.frameBuffer = null;

    /**
     * @member {Texture}
     */
    this.texture = null;

    /**
     * The size of the object as a rectangle
     * @member {Rectangle} 
     */
    this.size = new math.Rectangle(0, 0, 1, 1);

    /**
     * The current resolution
     * @member {number}
     */
    this.resolution = resolution || CONST.RESOLUTION;

    /**
     * The projection matrix 
     * @member {Matrix}
     */
    this.projectionMatrix = new math.Matrix();

    /**
     * The object's transform
     * @member {Matrix}
     */
    this.transform = null;

    /**
     * 
     * @member {Rectangle}
     */
    this.frame = null;

    /**
     * The stencil buffer stores masking data for the render target
     * @member {WebGLRenderBuffer}
     */
    this.stencilBuffer = null;

    /**
     * The data structure for the stencil masks
     * @member {StencilMaskStack}
     */
    this.stencilMaskStack = new StencilMaskStack();

    /**
     * Stores filter data for the render target
     * @member {Array}
     */
    this.filterStack = [
        {
            renderTarget:this,
            filter:[],
            bounds:this.size
        }
    ];


    /**
     * The scale mode
     * @member {number}
     * @default CONST.SCALE_MODES.DEFAULT
     */
    this.scaleMode = scaleMode || CONST.SCALE_MODES.DEFAULT;

    /**
     * Whether this object is the root element or not
     * @member {boolean}
     */
    this.root = root;

    if (!this.root)
    {
       // this.flipY = true;
        this.frameBuffer = gl.createFramebuffer();

        /*
            A frame buffer needs a target to render to..
            create a texture and bind it attach it to the framebuffer..
         */

        this.texture = gl.createTexture();

        gl.bindTexture(gl.TEXTURE_2D,  this.texture);

        // set the scale properties of the texture..
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, scaleMode === CONST.SCALE_MODES.LINEAR ? gl.LINEAR : gl.NEAREST);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, scaleMode === CONST.SCALE_MODES.LINEAR ? gl.LINEAR : gl.NEAREST);

        // check to see if the texture is a power of two!
        var isPowerOfTwo = utils.isPowerOfTwo(width, height);

        //TODO for 99% of use cases if a texture is power of two we should tile the texture...
         if (!isPowerOfTwo)
        {
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
        }
        else
        {

            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT);
        }

        gl.bindFramebuffer(gl.FRAMEBUFFER, this.frameBuffer );
        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, this.texture, 0);
    }


    this.resize(width, height);
};

RenderTarget.prototype.constructor = RenderTarget;
module.exports = RenderTarget;

/**
* Clears the filter texture.
*
*/
RenderTarget.prototype.clear = function()
{
    var gl = this.gl;
    gl.bindFramebuffer(gl.FRAMEBUFFER, this.frameBuffer);
    gl.clearColor(0,0,0,0);
    gl.clear(gl.COLOR_BUFFER_BIT);
};

/**
* Binds the stencil buffer.
*
*/
RenderTarget.prototype.attachStencilBuffer = function()
{

    if ( this.stencilBuffer )
    {
        return;
    }

    /*
        The stencil buffer is used for masking in pixi
        lets create one and then add attach it to the framebuffer..
     */
    if (!this.root)
    {
        var gl = this.gl;

        this.stencilBuffer = gl.createRenderbuffer();
        gl.bindRenderbuffer(gl.RENDERBUFFER, this.stencilBuffer);
        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, this.stencilBuffer);
        gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_STENCIL,  this.size.width * this.resolution  , this.size.height * this.resolution );
    }
};

/**
* Binds the buffers and initialises the viewport.
*
*/
RenderTarget.prototype.activate = function()
{
    //TOOD refactor usage of frame..
    var gl = this.gl;

    gl.bindFramebuffer(gl.FRAMEBUFFER, this.frameBuffer);

    var projectionFrame = this.frame || this.size;

    // TODO add a dirty flag to this of a setter for the frame?
    this.calculateProjection( projectionFrame );

    if(this.transform)
    {
        this.projectionMatrix.append(this.transform);
    }

    gl.viewport(0,0, projectionFrame.width * this.resolution, projectionFrame.height * this.resolution);
};

/**
* Updates the projection matrix based on a projection frame (which is a rectangle)
*
*/
RenderTarget.prototype.calculateProjection = function( projectionFrame )
{
    var pm = this.projectionMatrix;

    pm.identity();

    if (!this.root)
    {
        pm.a = 1 / projectionFrame.width*2;
        pm.d = 1 / projectionFrame.height*2;

        pm.tx = -1 - projectionFrame.x * pm.a;
        pm.ty = -1 - projectionFrame.y * pm.d;
    }
    else
    {
        pm.a = 1 / projectionFrame.width*2;
        pm.d = -1 / projectionFrame.height*2;

        pm.tx = -1 - projectionFrame.x * pm.a;
        pm.ty = 1 - projectionFrame.y * pm.d;
    }
};


/**
 * Resizes the texture to the specified width and height
 *
 * @param width {Number} the new width of the texture
 * @param height {Number} the new height of the texture
 */
RenderTarget.prototype.resize = function(width, height)
{
    width = width | 0;
    height = height | 0;

    if (this.size.width === width && this.size.height === height) {
        return;
    }

    this.size.width = width;
    this.size.height = height;

    if (!this.root)
    {
        var gl = this.gl;

        gl.bindTexture(gl.TEXTURE_2D,  this.texture);

        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA,  width * this.resolution, height * this.resolution , 0, gl.RGBA, gl.UNSIGNED_BYTE, null);

        if (this.stencilBuffer )
        {
            // update the stencil buffer width and height
            gl.bindRenderbuffer(gl.RENDERBUFFER, this.stencilBuffer);
            gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_STENCIL,  width * this.resolution, height * this.resolution );
        }
    }

    var projectionFrame = this.frame || this.size;

    this.calculateProjection( projectionFrame );
};

/**
 * Destroys the render target.
 *
 */
RenderTarget.prototype.destroy = function()
{
    var gl = this.gl;
    gl.deleteFramebuffer( this.frameBuffer );
    gl.deleteTexture( this.texture );

    this.frameBuffer = null;
    this.texture = null;
};