/*
* Filter
* Visit http://createjs.com/ for documentation, updates and examples.
*
* Copyright (c) 2010 gskinner.com, inc.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/

/**
 * @module EaselJS
 */

// namespace:
this.createjs = this.createjs||{};

(function() {
	"use strict";


// constructor:
	/**
	 * Base class that all filters should inherit from. Appli
	 *
	 * When on a regular Stage apply the Filters and then cache the object using the {{#crossLink "DisplayObject/cache"}}{{/crossLink}} method.
	 * When a cached object changes, please use {{#crossLink "DisplayObject/updateCache"}}{{/crossLink}}.
	 * When on a StageGL simply setting content in the `.filters` array will trigger an automatic and constantly updated cache.
	 *
	 * <h4>Example</h4>
	 *
	 *      myInstance.filters = [
	 *          new createjs.ColorFilter(0, 0, 0, 1, 255, 0, 0),
	 *          new createjs.BlurFilter(5, 5, 10)
	 *      ];
	 *      myInstance.cache(0,0, 100, 100);
	 *
	 * Note that each filter can implement a {{#crossLink "Filter/getBounds"}}{{/crossLink}} method, which returns the
	 * margins that need to be applied in order to fully display the filter. For example, the {{#crossLink "BlurFilter"}}{{/crossLink}}
	 * will cause an object to feather outwards, resulting in a margin around the shape.
	 *
	 * Any filter that consumes an external image stretches the image to cover the cached bounds. If this is an undesired
	 * visual result, then use an intermediary cache to properly size and layout your data before passing it to a filter.
	 *
	 *
	 * <h4>EaselJS Filters</h4>
	 * EaselJS comes with a number of pre-built filters:
	 * <ul>
	 *     <li>{{#crossLink "AberrationFilter"}}{{/crossLink}} : Shift the RGB components separately along a given vector</li>
	 *     <li>{{#crossLink "AlphaMapFilter"}}{{/crossLink}} : Map a greyscale image to the alpha channel of a display object</li>
	 *     <li>{{#crossLink "AlphaMaskFilter"}}{{/crossLink}}: Map an image's alpha channel to the alpha channel of a display object</li>
	 *     <li>{{#crossLink "BlurFilter"}}{{/crossLink}}: Apply vertical and horizontal blur to a display object</li>
	 *     <li>{{#crossLink "ColorFilter"}}{{/crossLink}}: Color transform a display object</li>
	 *     <li>{{#crossLink "ColorMatrixFilter"}}{{/crossLink}}: Transform an image using a {{#crossLink "ColorMatrix"}}{{/crossLink}}</li>
	 *     <li>{{#crossLink "DisplacementFilter"}}{{/crossLink}}: Create localized distortions in supplied display object</li>
	 * </ul>
	 *
	 * @class Filter
	 * @constructor
	 **/
	function Filter() {
		/**
		 * A flag stating that this filter uses a context draw mode and cannot be batched into imageData processing.
		 * @property usesContext
		 * @type {boolean}
		 * @default false
		 */
		this.usesContext = false;

		/**
		 * Another filter that is required to act as part of this filter and created and managed under the hood.
		 * @private
		 * @property _multiPass
		 * @type {Filter}
		 * @default null
		 */
		this._multiPass = null;

		/**
		 * Pre-processed template shader code. It will be parsed before being fed in into the shader compiler.
		 * This should be based upon StageGL.SHADER_VERTEX_BODY_REGULAR
		 * @property VTX_SHADER
		 * @type {String}
		 * @readonly
		 */
		this.VTX_SHADER_BODY = null;

		/**
		 * Pre-processed template shader code. It will be parsed before being fed in into the shader compiler.
		 * This should be based upon StageGL.SHADER_FRAGMENT_BODY_REGULAR
		 * @property FRAG_SHADER
		 * @type {String}
		 * @readonly
		 */
		this.FRAG_SHADER_BODY = null;
	}
	var p = Filter.prototype;

// static methods:
	/**
	 * Check to see if an image source being provided is one that is valid.
	 * <h4>Valid Sources:</h4>
	 * <ul>
	 *     <li>Image Object</li>
	 *     <li>HTML Canvas Element</li>
	 *     <li>`.cacheCanvas` on an object with the same stage</li>
	 * </ul>
	 * WebGLTextures CANNOT be shared between multiple WebGL contexts. This means the only safe source for a WebGLTexture
	 * is an object cached using the same StageGL as the object trying to use it in a filter. This function does not
	 * enforce that restriction, as it is difficult or expensive to detect. The render will crash or fail to load the
	 * image data if the rule isn't followed.
	 * @param {HTMLImageElement|HTMLCanvasElement|WebGLTexture} src The element to check for validity
	 * @return Boolean Whether the source is valid
	 */
	Filter.isValidImageSource = function(src) {
		return Boolean(src) && (
			src instanceof Image ||
			src instanceof WebGLTexture ||
			src instanceof HTMLCanvasElement
		);
	};

// public methods:
	/**
	 * Provides padding values for this filter. That is, how much the filter will extend the visual bounds of an object it is applied to.
	 * @method getBounds
	 * @param {Rectangle} [rect] If specified, the provided Rectangle instance will be expanded by the padding amounts and returned.
	 * @return {Rectangle} If a `rect` param was provided, it is returned. If not, either a new rectangle with the padding values, or null if no padding is required for this filter.
	 **/
	p.getBounds = function(rect) {
		return rect;
	};

	/**
	 * Assign any unique uniforms or other setup functionality here.
	 * @method shaderParamSetup
	 * @param {WebGLContext} gl The context associated with the stage performing the render.
	 * @param {StageGL} stage The stage instance that will be rendering.
	 * @param {ShaderProgram} shaderProgram The compiled shader that is going to be used to perform the render.
	 */
	p.shaderParamSetup = function(gl, stage, shaderProgram) {};

	/**
	 * Applies the filter to the specified context.
	 * @method applyFilter
	 * @param {CanvasRenderingContext2D} ctx The 2D context to use as the source.
	 * @param {Number} x The x position to use for the source rect.
	 * @param {Number} y The y position to use for the source rect.
	 * @param {Number} width The width to use for the source rect.
	 * @param {Number} height The height to use for the source rect.
	 * @param {CanvasRenderingContext2D} [targetCtx=ctx] The 2D context to draw the result to. Defaults to the context passed to ctx.
	 * @return {Boolean} If the filter was applied successfully.
	 **/
	p.applyFilter = function(ctx, x, y, width, height, targetCtx) {
		// this is the default behaviour because most filters access pixel data. It is overridden when not needed.
		targetCtx = targetCtx || ctx;
		try {
			var imageData = ctx.getImageData(x, y, width, height);
		} catch (e) {
			return false;
		}
		if (this._applyFilter(imageData)) {
			targetCtx.putImageData(imageData, x, y);
			return true;
		}
		return false;
	};

	/**
	 * Returns a string representation of this object.
	 * @method toString
	 * @return {String} a string representation of the instance.
	 **/
	p.toString = function() {
		return "[Filter]";
	};

	/**
	 * Returns a clone of this Filter instance.
	 * @method clone
	 * @return {Filter} A clone of the current Filter instance.
	 **/
	p.clone = function() {
		return new Filter();
	};
	
// private methods:
	/**
	 * @method _applyFilter
	 * @param {ImageData} imageData Target ImageData instance.
	 * @return {Boolean}
	 **/
	p._applyFilter = function(imageData) { return true; };


	createjs.Filter = Filter;
}());