/**
* @author       Richard Davey <rich@photonstorm.com>
* @author       Mat Groves (@Doormat23)
* @copyright    2016 Photon Storm Ltd.
* @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
*/

/**
* A Canvas based renderer.
*
* @class Phaser.Renderer.Canvas
* @constructor
* @param {Phaser.Game} game - Game reference to the currently running game.
*/
Phaser.Renderer.WebGL = function (game)
{
    /**
    * @property {Phaser.Game} game - A reference to the currently running Game.
    */
    this.game = game;

    this.type = Phaser.WEBGL;

    this.shaderID = 0;

    /**
     * This sets if the CanvasRenderer will clear the canvas or not before the new render pass.
     * If the Stage is NOT transparent Pixi will use a canvas sized fillRect operation every frame to set the canvas background color.
     * If the Stage is transparent Pixi will use clearRect to clear the canvas every frame.
     * Disable this by setting this to false. For example if your game has a canvas filling background image you often don't need this set.
     *
     * @property clearBeforeRender
     * @type Boolean
     * @default
     */
    this.clearBeforeRender = game.clearBeforeRender;

    /**
     * Whether the render view is transparent
     *
     * @property transparent
     * @type Boolean
     */
    this.transparent = game.transparent;

    /**
     * Whether the render view should be resized automatically
     *
     * @property autoResize
     * @type Boolean
     */
    this.autoResize = false;

    /**
     * The width of the canvas view
     *
     * @property width
     * @type Number
     * @default 800
     */
    this.width = game.width * game.resolution;

    /**
     * The height of the canvas view
     *
     * @property height
     * @type Number
     * @default 600
     */
    this.height = game.height * game.resolution;

    this.resolution = game.resolution;

    /**
     * The canvas element that everything is drawn to.
     *
     * @property view
     * @type HTMLCanvasElement
     */
    this.view = game.canvas;

    /**
     * The number of points beyond which the renderer swaps to using the Stencil Buffer to render the Graphics.
     *
     * @type {number}
     */
    this.stencilBufferLimit = 6;

    //  WebGL specific from here

    this.enableMultiTextureToggle = false;

    this.extensions = {};

    /**
     * The value of the preserveDrawingBuffer flag affects whether or not the contents of the stencil buffer is retained after rendering.
     *
     * @property preserveDrawingBuffer
     * @type Boolean
     */
    this.preserveDrawingBuffer = game.preserveDrawingBuffer;

    /**
     * @property _contextOptions
     * @type Object
     * @private
     */
    this.contextOptions = {
        alpha: this.transparent,
        antialias: game.antialias,
        premultipliedAlpha: this.transparent && this.transparent !== 'notMultiplied',
        stencil: true,
        preserveDrawingBuffer: this.preserveDrawingBuffer
    };

    /**
     * @property projection
     * @type Point
     */
    this.projection = new Phaser.Point();

    /**
     * @property offset
     * @type Point
     */
    this.offset = new Phaser.Point();

    /**
     * Deals with managing the shader programs and their attribs
     * @property shaderManager
     * @type WebGLShaderManager
     */
    this.shaderManager = new Phaser.Renderer.WebGL.ShaderManager(this);

    /**
     * Manages the rendering of sprites
     * @property spriteBatch
     * @type WebGLSpriteBatch
     */
    this.spriteBatch = new Phaser.Renderer.WebGL.BatchManager(this);

    /**
     * Manages the filters
     * @property filterManager
     * @type WebGLFilterManager
     */
    this.filterManager = new Phaser.Renderer.WebGL.FilterManager(this);

    /**
     * Manages the stencil buffer
     * @property stencilManager
     * @type WebGLStencilManager
     */
    this.stencilManager = new Phaser.Renderer.WebGL.StencilManager(this);

    this.gl = null;

    this.textureArray = [];

    this.blendModes = [];

    this.drawCount = 0;
    this.flipY = 1;

    this._fbErrors = {
        36054: 'Incomplete attachment',
        36055: 'Missing attachment',
        36057: 'Incomplete dimensions',
        36061: 'Framebuffer unsupported'
    };

    this.init();

};

Phaser.Renderer.WebGL.GameObjects = {};
Phaser.Renderer.WebGL.Shaders = {};

Phaser.Renderer.WebGL.prototype.constructor = Phaser.Renderer.WebGL;

Phaser.Renderer.WebGL.prototype = {

    init: function ()
    {
        this.gl = this.view.getContext('webgl', this.contextOptions) || this.view.getContext('experimental-webgl', this.contextOptions);

        if (!this.gl)
        {
            throw new Error('This browser does not support WebGL. Try using the Canvas renderer.');
        }

        //  Mixin the renderer functions
        for (var renderer in Phaser.Renderer.WebGL.GameObjects)
        {
            var types = Phaser.Renderer.WebGL.GameObjects[renderer].TYPES;

            if (!types)
            {
                continue;
            }

            for (var i = 0; i < types.length; i++)
            {
                types[i].render = Phaser.Renderer.WebGL.GameObjects[renderer].render;
            }
        }

        var gl = this.gl;

        this.maxTextures = gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS);

        gl.disable(gl.DEPTH_TEST);
        gl.disable(gl.CULL_FACE);
        gl.enable(gl.BLEND);

        this.shaderManager.init();
        this.spriteBatch.init();
        this.filterManager.init();
        this.stencilManager.init();

        this.resize(this.width, this.height);

        // Load WebGL extension
        this.extensions.compression = {};

        var etc1 = gl.getExtension('WEBGL_compressed_texture_etc1') || gl.getExtension('WEBKIT_WEBGL_compressed_texture_etc1');
        var pvrtc = gl.getExtension('WEBGL_compressed_texture_pvrtc') || gl.getExtension('WEBKIT_WEBGL_compressed_texture_pvrtc');
        var s3tc = gl.getExtension('WEBGL_compressed_texture_s3tc') || gl.getExtension('WEBKIT_WEBGL_compressed_texture_s3tc');

        if (etc1)
        {
            this.extensions.compression.ETC1 = etc1;
        }

        if (pvrtc)
        {
            this.extensions.compression.PVRTC = pvrtc;
        }

        if (s3tc)
        {
            this.extensions.compression.S3TC = s3tc;
        }

        //  Map Blend Modes

        var add = [ gl.SRC_ALPHA, gl.DST_ALPHA ];
        var normal = [ gl.ONE, gl.ONE_MINUS_SRC_ALPHA ];
        var multiply = [ gl.DST_COLOR, gl.ONE_MINUS_SRC_ALPHA ];
        var screen = [ gl.SRC_ALPHA, gl.ONE ];

        this.blendModes = [
            normal, add, multiply, screen, normal,
            normal, normal, normal, normal,
            normal, normal, normal, normal,
            normal, normal, normal, normal
        ];

    },

    resize: function (width, height)
    {
        this.width = width * this.game.resolution;
        this.height = height * this.game.resolution;

        this.view.width = this.width;
        this.view.height = this.height;

        if (this.autoResize)
        {
            this.view.style.width = (this.width / this.game.resolution) + 'px';
            this.view.style.height = (this.height / this.game.resolution) + 'px';
        }

        this.gl.viewport(0, 0, this.width, this.height);

        this.projection.x = (this.width / 2) / this.game.resolution;
        this.projection.y = -(this.height / 2) / this.game.resolution;
    },

    getShaderID: function (shader)
    {
        this.shaderID++;

        //  Store shader reference somewhere?

        return this.shaderID;
    },

    /**
    * If Multi Texture support has been enabled, then calling this method will enable batching on the given
    * textures. The texture collection is an array of keys, that map to Phaser.Cache image entries.
    *
    * The number of textures that can be batched is dependent on hardware. If you provide more textures
    * than can be batched by the GPU, then only those at the start of the array will be used. Generally
    * you shouldn't provide more than 16 textures to this method. You can check the hardware limit via the
    * `maxTextures` property.
    *
    * You can also check the property `currentBatchedTextures` at any time, to see which textures are currently
    * being batched.
    *
    * To stop all textures from being batched, call this method again with an empty array.
    *
    * To change the textures being batched, call this method with a new array of image keys. The old ones
    * will all be purged out and no-longer batched, and the new ones enabled.
    * 
    * Note: Throws a warning if you haven't enabled Multiple Texture batching support in the Phaser Game config.
    * 
    * @method setTexturePriority
    * @param textureNameCollection {Array} An Array of Texture Cache keys to use for multi-texture batching.
    * @return {Array} An array containing the texture keys that were enabled for batching.
    */
    setTexturePriority: function (textureNameCollection)
    {
        if (!this.enableMultiTextureToggle)
        {
            console.warn('setTexturePriority error: Multi Texture support hasn\'t been enabled in the Phaser Game Config.');
            return;
        }

        var maxTextures = this.maxTextures;
        var imageCache = this.game.cache._cache.image;
        var imageName = null;

        //  Clear out all previously batched textures and reset their flags.
        //  If the array has been modified, then the developer will have to
        //  deal with that in their own way.
        for (var i = 0; i < this.currentBatchedTextures.length; i++)
        {
            imageName = textureNameCollection[index];

            if (!(imageName in imageCache))
            {
                continue;
            }
            
            imageCache[imageName].base.textureIndex = 0;
        }

        this.currentBatchedTextures.length = 0;

        // We start from 1 because framebuffer texture uses unit 0.
        for (var index = 0; index < textureNameCollection.length; ++index)
        {
            imageName = textureNameCollection[index];

            if (!(imageName in imageCache))
            {
                continue;
            }

            if (index + 1 < maxTextures)
            {
                imageCache[imageName].base.textureIndex = index + 1;
            }
            else
            {
                imageCache[imageName].base.textureIndex = maxTextures - 1;
            }

            this.currentBatchedTextures.push(imageName);
        }

        return this.currentBatchedTextures;

    },

    getMaxTextureUnits: function ()
    {
        return this.gl.getParameter(this.gl.MAX_TEXTURE_IMAGE_UNITS);
    },

    /**
     * Renders the stage to its webGL view
     *
     * @method render
     * @param stage {Stage} the Stage element to be rendered
     */
    render: function (stage)
    {
        // no point rendering if our context has been blown up!
        if (this.contextLost)
        {
            return;
        }

        //  Add Pre-render hook

        var gl = this.gl;

        gl.viewport(0, 0, this.width, this.height);

        // make sure we are bound to the main frame buffer
        gl.bindFramebuffer(gl.FRAMEBUFFER, null);

        if (this.game.clearBeforeRender)
        {
            gl.clearColor(stage._bgColor.r, stage._bgColor.g, stage._bgColor.b, stage._bgColor.a);

            gl.clear(gl.COLOR_BUFFER_BIT);
        }

        this.offset.x = this.game.camera._shake.x;
        this.offset.y = this.game.camera._shake.y;

        this.setBlendMode(this.blendModes.NORMAL);

        //  Reset draw count
        this.drawCount = 0;

        //  RenderTextures set this to -1
        this.flipY = 1;

        this.spriteBatch.begin();

        this.filterManager.begin();

        stage.render(this, stage);

        this.spriteBatch.end();

        //  Add Post-render hook
    },

    /**
    * Removes the base texture from the GPU, useful for managing resources on the GPU.
    * A texture is still 100% usable and will simply be re-uploaded if there is a sprite on screen that is using it.
    *
    * @method unloadTexture
    */
    unloadTexture: function (texture)
    {
        var gl = this.gl;

        var glTexture = texture._glTexture;

        if (gl && glTexture)
        {
            gl.deleteTexture(glTexture);
        }

        texture._glTexture = null;
        texture._dirty = false;
    },

    updateTexture: function (texture)
    {
        if (!texture.hasLoaded)
        {
            return false;
        }

        if (texture.source.compressionAlgorithm)
        {
            return this.updateCompressedTexture(texture);
        }

        var gl = this.gl;

        if (!texture._glTextures)
        {
            texture._glTextures = gl.createTexture();
        }

        gl.activeTexture(gl.TEXTURE0 + texture.textureIndex);

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

        gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, texture.premultipliedAlpha);

        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texture.source);

        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, texture.scaleMode === Phaser.scaleModes.LINEAR ? gl.LINEAR : gl.NEAREST);

        if (texture.mipmap && Phaser.Math.isPowerOfTwo(texture.width, texture.height))
        {
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, texture.scaleMode === Phaser.scaleModes.LINEAR ? gl.LINEAR_MIPMAP_LINEAR : gl.NEAREST_MIPMAP_NEAREST);
            gl.generateMipmap(gl.TEXTURE_2D);
        }
        else
        {
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, texture.scaleMode === Phaser.scaleModes.LINEAR ? gl.LINEAR : gl.NEAREST);
        }

        if (!texture._powerOf2)
        {
            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);
        }

        texture._dirty = false;

        return true;
    },

    updateCompressedTexture: function (texture)
    {
        if (!texture.hasLoaded)
        {
            return false;
        }

        var gl = this.gl;
        var textureMetaData = texture.source;

        if (!texture._glTextures)
        {
            texture._glTextures = gl.createTexture();
        }

        gl.activeTexture(gl.TEXTURE0 + texture.textureIndex);

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

        gl.compressedTexImage2D(
            gl.TEXTURE_2D,
            0,
            textureMetaData.glExtensionFormat,
            textureMetaData.width,
            textureMetaData.height,
            0,
            textureMetaData.textureData
        );

        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, texture.scaleMode === Phaser.scaleModes.LINEAR ? gl.LINEAR : gl.NEAREST);

        if (texture.mipmap && Phaser.Math.isPowerOfTwo(texture.width, texture.height))
        {
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, texture.scaleMode === Phaser.scaleModes.LINEAR ? gl.LINEAR_MIPMAP_LINEAR : gl.NEAREST_MIPMAP_NEAREST);
            gl.generateMipmap(gl.TEXTURE_2D);
        }
        else
        {
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, texture.scaleMode === Phaser.scaleModes.LINEAR ? gl.LINEAR : gl.NEAREST);
        }

        if (!texture._powerOf2)
        {
            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);
        }

        texture._dirty = false;

        return true;
    },

    //  Blend Mode Manager

    setBlendMode: function (blendMode)
    {
        if (this.currentBlendMode === blendMode)
        {
            return false;
        }

        this.currentBlendMode = blendMode;
        
        var blendModeWebGL = this.blendModes[this.currentBlendMode];

        if (blendModeWebGL)
        {
            this.gl.blendFunc(blendModeWebGL[0], blendModeWebGL[1]);
        }
        
        return true;
    },

    //  WebGL Mask Manager

    pushMask: function (maskData)
    {
        var gl = this.gl;

        if (maskData.dirty)
        {
            // PIXI.WebGLGraphics.updateGraphics(maskData, gl);
        }

        if (maskData._webGL === undefined || maskData._webGL.data === undefined || maskData._webGL.data.length === 0)
        {
            return;
        }

        this.stencilManager.pushStencil(maskData, maskData._webGL.data[0]);
    },

    popMask: function (maskData)
    {
        if (maskData._webGL === undefined || maskData._webGL.data === undefined || maskData._webGL.data.length === 0)
        {
            return;
        }

        this.stencilManager.popStencil(maskData, maskData._webGL.data[0]);
    },

    //  Shader Utils

    //  PIXI.CompileVertexShader
    compileVertexShader: function (src)
    {
        return this.compileShader(src, this.gl.VERTEX_SHADER);
    },

    //  PIXI.CompileFragmentShader
    compileFragmentShader: function (src)
    {
        return this.compileShader(src, this.gl.FRAGMENT_SHADER);
    },

    //  PIXI._CompileShader
    compileShader: function (src, type)
    {
        if (Array.isArray(src))
        {
            src = src.join('\n');
        }

        var shader = this.gl.createShader(type);
        this.gl.shaderSource(shader, src);
        this.gl.compileShader(shader);

        if (!this.gl.getShaderParameter(shader, this.gl.COMPILE_STATUS))
        {
            console.log(this.gl.getShaderInfoLog(shader));
            return null;
        }

        return shader;
    },

    //  PIXI.compileProgram
    compileProgram: function (vertexSrc, fragmentSrc)
    {
        var gl = this.gl;

        var fragmentShader = this.compileFragmentShader(fragmentSrc);
        var vertexShader = this.compileVertexShader(vertexSrc);

        var shaderProgram = gl.createProgram();

        gl.attachShader(shaderProgram, vertexShader);
        gl.attachShader(shaderProgram, fragmentShader);
        gl.linkProgram(shaderProgram);

        if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS))
        {
            console.log(gl.getProgramInfoLog(shaderProgram));
            console.log('Could not initialize shaders');
        }

        return shaderProgram;
    },

    createEmptyTexture: function (width, height, scaleMode)
    {
        var gl = this.gl;
        var texture = gl.createTexture();
        var glScaleMode = (scaleMode === Phaser.scaleModes.LINEAR) ? gl.LINEAR : gl.NEAREST;

        gl.bindTexture(gl.TEXTURE_2D, texture);
        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);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, glScaleMode);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, glScaleMode);

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

        return texture;
    },

    createFramebuffer: function (width, height, scaleMode, textureUnit)
    {
        var gl = this.gl;
        var framebuffer = gl.createFramebuffer();
        var depthStencilBuffer = gl.createRenderbuffer();
        var colorBuffer = null;   
        var fbStatus = 0;
        
        gl.activeTexture(gl.TEXTURE0 + textureUnit);

        gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
        gl.bindRenderbuffer(gl.RENDERBUFFER, depthStencilBuffer);

        //  `this.renderBuffer` = undefined? FilterTexture has a renderBuffer, but `this` doesn't.
        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, this.renderBuffer);

        colorBuffer = this.createEmptyTexture(width, height, scaleMode);

        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, colorBuffer, 0);

        fbStatus = gl.checkFramebufferStatus(gl.FRAMEBUFFER);

        if (fbStatus !== gl.FRAMEBUFFER_COMPLETE)
        {
            console.error('Incomplete GL framebuffer. ', this._fbErrors[fbStatus]);
        }

        framebuffer.width = width;
        framebuffer.height = height;
        framebuffer.targetTexture = colorBuffer;
        framebuffer.renderBuffer = depthStencilBuffer;

        return framebuffer;
    },

    destroy: function ()
    {
        this.projection = null;
        this.offset = null;

        this.shaderManager.destroy();
        this.spriteBatch.destroy();
        this.maskManager.destroy();
        this.filterManager.destroy();

        this.shaderManager = null;
        this.spriteBatch = null;
        this.maskManager = null;
        this.filterManager = null;

        this.gl = null;
        this.renderSession = null;

        Phaser.CanvasPool.remove(this);
    }

};