/**
 * @author Mat Groves
 * 
 * Big thanks to the very clever Matt DesLauriers <mattdesl> https://github.com/mattdesl/
 * for creating the original pixi version!
 *
 * Heavily inspired by LibGDX's WebGLPrimitiveBatch:
 * https://github.com/libgdx/libgdx/blob/master/gdx/src/com/badlogic/gdx/graphics/g2d/WebGLPrimitiveBatch.java
 */

 /**
 *
 * @class WebGLPrimitiveBatch
 * @private
 * @constructor
 * @param gl {WebGLContext} the current WebGL drawing context
 *
 */
PIXI.WebGLPrimitiveBatch = function(gl)
{

    /**
     * 
     *
     * @property vertSize
     * @type Number
     */
    this.vertSize = 6;

    /**
     * The number of images in the SpriteBatch before it flushes
     * @property size
     * @type Number
     */
    this.size = 2000;//Math.pow(2, 16) /  this.vertSize;

    //the total number of floats in our batch
    var numVerts = this.size * 4 *  this.vertSize;
    //the total number of indices in our batch
    var numIndices = this.size * 6;

    //vertex data

    /**
    * Holds the vertices
    *
    * @property vertices
    * @type Float32Array
    */
    this.vertices = new Float32Array(numVerts);

    //index data
    /**
     * Holds the indices
     *
     * @property indices
     * @type Uint16Array
     */
    this.indices = new Uint16Array(numIndices);
    
    this.lastIndexCount = 0;

    for (var i=0, j=0; i < numIndices; i += 6, j += 4)
    {
        this.indices[i + 0] = j + 0;
        this.indices[i + 1] = j + 1;
        this.indices[i + 2] = j + 2;
        this.indices[i + 3] = j + 0;
        this.indices[i + 4] = j + 2;
        this.indices[i + 5] = j + 3;
    }


    this.drawing = false;
    this.currentBatchSize = 0;
    this.currentBaseTexture = null;
    
    this.setContext(gl);
};

/**
* 
* @method setContext
*
* @param gl {WebGLContext} the current WebGL drawing context
*/
PIXI.WebGLPrimitiveBatch.prototype.setContext = function(gl)
{
    this.gl = gl;

    // create a couple of buffers
    this.vertexBuffer = gl.createBuffer();
    this.indexBuffer = gl.createBuffer();

    // 65535 is max index, so 65535 / 6 = 10922.


    //upload the index data
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, this.indexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, this.indices, gl.STATIC_DRAW);

    gl.bindBuffer(gl.ARRAY_BUFFER, this.vertexBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, this.vertices, gl.DYNAMIC_DRAW);

    this.currentBlendMode = 99999;
};

/**
* 
* @method begin
*
* @param renderSession {RenderSession} the RenderSession
*/
PIXI.WebGLPrimitiveBatch.prototype.begin = function(renderSession)
{
    this.renderSession = renderSession;
    this.shader = this.renderSession.shaderManager.defaultShader;

    this.start();
};

/**
* 
* @method end
*
*/
PIXI.WebGLPrimitiveBatch.prototype.end = function()
{
    this.flush();
};

PIXI.WebGLPrimitiveBatch.prototype.render = function(sprite)
{
    var texture = sprite.texture;

    // check texture..
    if(texture.baseTexture !== this.currentBaseTexture || this.currentBatchSize >= this.size)
    {
        this.flush();
        this.currentBaseTexture = texture.baseTexture;
    }


    // check blend mode
    if(sprite.blendMode !== this.currentBlendMode)
    {
        this.setBlendMode(sprite.blendMode);
    }

    // get the uvs for the texture
    var uvs = sprite._uvs || sprite.texture._uvs;
    // if the uvs have not updated then no point rendering just yet!
    if(!uvs)return;

    // get the sprites current alpha
    var alpha = sprite.worldAlpha;
    var tint = sprite.tint;

    var verticies = this.vertices;


    // TODO trim??
    var aX = sprite.anchor.x;
    var aY = sprite.anchor.y;

    var w0, w1, h0, h1;
        
    if (sprite.texture.trim)
    {
        // if the sprite is trimmed then we need to add the extra space before transforming the sprite coords..
        var trim = sprite.texture.trim;

        w1 = trim.x - aX * trim.width;
        w0 = w1 + texture.frame.width;

        h1 = trim.y - aY * trim.height;
        h0 = h1 + texture.frame.height;

    }
    else
    {
        w0 = (texture.frame.width ) * (1-aX);
        w1 = (texture.frame.width ) * -aX;

        h0 = texture.frame.height * (1-aY);
        h1 = texture.frame.height * -aY;
    }

    var index = this.currentBatchSize * 4 * this.vertSize;

    var worldTransform = sprite.worldTransform;//.toArray();

    var a = worldTransform.a;//[0];
    var b = worldTransform.c;//[3];
    var c = worldTransform.b;//[1];
    var d = worldTransform.d;//[4];
    var tx = worldTransform.tx;//[2];
    var ty = worldTransform.ty;///[5];

    // xy
    verticies[index++] = a * w1 + c * h1 + tx;
    verticies[index++] = d * h1 + b * w1 + ty;
    // uv
    verticies[index++] = uvs.x0;
    verticies[index++] = uvs.y0;
    // color
    verticies[index++] = alpha;
    verticies[index++] = tint;

    // xy
    verticies[index++] = a * w0 + c * h1 + tx;
    verticies[index++] = d * h1 + b * w0 + ty;
    // uv
    verticies[index++] = uvs.x1;
    verticies[index++] = uvs.y1;
    // color
    verticies[index++] = alpha;
    verticies[index++] = tint;

    // xy
    verticies[index++] = a * w0 + c * h0 + tx;
    verticies[index++] = d * h0 + b * w0 + ty;
    // uv
    verticies[index++] = uvs.x2;
    verticies[index++] = uvs.y2;
    // color
    verticies[index++] = alpha;
    verticies[index++] = tint;

    // xy
    verticies[index++] = a * w1 + c * h0 + tx;
    verticies[index++] = d * h0 + b * w1 + ty;
    // uv
    verticies[index++] = uvs.x3;
    verticies[index++] = uvs.y3;
    // color
    verticies[index++] = alpha;
    verticies[index++] = tint;
    
    // increment the batchsize
    this.currentBatchSize++;


};

/**
* Renders the content and empties the current batch
*
* @method flush
* 
*/
PIXI.WebGLPrimitiveBatch.prototype.flush = function()
{
    // If the batch is length 0 then return as there is nothing to draw
    if (this.currentBatchSize===0)return;

    var gl = this.gl;
    
    // bind the current texture
    gl.bindTexture(gl.TEXTURE_2D, this.currentBaseTexture._glTextures[gl.id] || PIXI.createWebGLTexture(this.currentBaseTexture, gl));

    // upload the verts to the buffer
    
    if(this.currentBatchSize > ( this.size * 0.5 ) )
    {
        gl.bufferSubData(gl.ARRAY_BUFFER, 0, this.vertices);
    }
    else
    {
        var view = this.vertices.subarray(0, this.currentBatchSize * 4 * this.vertSize);

        gl.bufferSubData(gl.ARRAY_BUFFER, 0, view);
    }

   // var view = this.vertices.subarray(0, this.currentBatchSize * 4 * this.vertSize);
    //gl.bufferSubData(gl.ARRAY_BUFFER, 0, view);
    
    // now draw those suckas!
    gl.drawElements(gl.TRIANGLES, this.currentBatchSize * 6, gl.UNSIGNED_SHORT, 0);
   
    // then reset the batch!
    this.currentBatchSize = 0;

    // increment the draw count
    this.renderSession.drawCount++;
};

/**
* 
* @method stop
*
*/
PIXI.WebGLPrimitiveBatch.prototype.stop = function()
{
    this.flush();
};

/**
* 
* @method start
*
*/
PIXI.WebGLPrimitiveBatch.prototype.start = function()
{
    var gl = this.gl;

    // bind the main texture
    gl.activeTexture(gl.TEXTURE0);

    // bind the buffers
    gl.bindBuffer(gl.ARRAY_BUFFER, this.vertexBuffer);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, this.indexBuffer);

    // set the projection
    var projection = this.renderSession.projection;
    gl.uniform2f(this.shader.projectionVector, projection.x, projection.y);

    // set the pointers
    var stride =  this.vertSize * 4;
    gl.vertexAttribPointer(this.shader.aVertexPosition, 2, gl.FLOAT, false, stride, 0);
    gl.vertexAttribPointer(this.shader.aTextureCoord, 2, gl.FLOAT, false, stride, 2 * 4);
    gl.vertexAttribPointer(this.shader.colorAttribute, 2, gl.FLOAT, false, stride, 4 * 4);

    // set the blend mode..
    if(this.currentBlendMode !== PIXI.blendModes.NORMAL)
    {
        this.setBlendMode(PIXI.blendModes.NORMAL);
    }
};

/**
* Sets-up the given blendMode from WebGL's point of view
* @method setBlendMode 
*
* @param blendMode {Number} the blendMode, should be a Pixi const, such as PIXI.BlendModes.ADD
*/
PIXI.WebGLPrimitiveBatch.prototype.setBlendMode = function(blendMode)
{
    this.flush();

    this.currentBlendMode = blendMode;
    
    var blendModeWebGL = PIXI.blendModesWebGL[this.currentBlendMode];
    this.gl.blendFunc(blendModeWebGL[0], blendModeWebGL[1]);
};

/**
* Destroys the SpriteBatch
* @method destroy
*/
PIXI.WebGLPrimitiveBatch.prototype.destroy = function()
{

    this.vertices = null;
    this.indices = null;
    
    this.gl.deleteBuffer( this.vertexBuffer );
    this.gl.deleteBuffer( this.indexBuffer );
    
    this.currentBaseTexture = null;
    
    this.gl = null;
};