package {

	import flash.display.Shader;
	import flash.events.Event;
	import flash.events.EventDispatcher;
	import flash.net.URLLoader;
	import flash.net.URLLoaderDataFormat;
	import flash.net.URLRequest;
	import flash.utils.ByteArray;

	/**
	* Class to handle loading or embedding, and passing values to a shader
	* to make it easier dealing with the quirks of the Shader class and bytecode.
	*/
	public class graphic_flex_image_effects_05_Flex_ShaderWrapper extends EventDispatcher {

		private var _shader:Shader;

		/**
		* Constructor. This accepts a path to a .pbj file to load or
		* a shader bytecode class to instantiate. If a file needs to be loaded,
		* the loading is initiated immediately. Completion of load will result in
		* a COMPLETE event being fired.
		*
		* @param pathOrClass Either the path to a .pbj file or the shader bytecode class.
		*/
		public function graphic_flex_image_effects_05_Flex_ShaderWrapper(pathOrClass:Object) {
			var shaderClass:Class = pathOrClass as Class;
			// if a class is passed, immediately instantiate it
			if (shaderClass != null) {
				createShader(ByteArray(new shaderClass()));
			// if a file path is passed, immediately load it
			} else if ((pathOrClass as String) != null) {
				load(pathOrClass as String);
			} else {
				throw new Error("Invalid object passed to constructor.");
			}
		}

		/**
		* Creates the Shader instance from the bytecode.
		*
		* @param data The ByteArray containing the shader bytecode.
		*/
		private function createShader(data:ByteArray):void {
			_shader = new Shader(data);
			dispatchEvent(new Event(Event.COMPLETE));
		}

		/**
		* Loads the specified .pbj file.
		*
		* @param path The path to the .pbj file to load.
		*/
		private function load(path:String):void {
			var loader:URLLoader = new URLLoader();
			loader.dataFormat = URLLoaderDataFormat.BINARY;
			loader.addEventListener(Event.COMPLETE, onShaderLoaded);
			loader.load(new URLRequest(path));
		}

		/**
		* Handler for when the .pbj file completes loading.
		*
		* @param event Event dispatched by URLLoader.
		*/
		private function onShaderLoaded(event:Event):void {
			var loader:URLLoader = event.target as URLLoader;
			createShader(loader.data as ByteArray);
		}

		/**
		* Returns the value of the specified parameter from the shader.
		* This method ensures that float and int values are extracted from
		* the Array that wraps them.
		*
		* @param name The name of the parameter to retrieve.
		*
		* @return The value of the parameter.
		*/
		public function getParameter(name:String):Object {
			// check to see if parameter exists
			if (_shader.data.hasOwnProperty(name)) {
				var value:Object = _shader.data[name].value;
				var type:String = _shader.data[name].type;
				// if type is float or int, grab the only value from the array
				if (type == "float" || type == "int") {
					value = (value as Array)[0];
				}
				return value;
			}
			return null;
		}

		/**
		* Sets the value of the specified parameter of the shader.
		* This method ensures that all values are passed as arrays to the shader,
		* even if the parameter is scalar.
		*
		* @param name The name of the parameter to set.
		* @param value The value to give the parameter.
		*
		* @return True if the parameter was found and set.
		*/
		public function setParameter(name:String, value:Object):Boolean {
			// check to see if parameter exists
			if (_shader.data.hasOwnProperty(name)) {
				// wrap scalar values in an array
				if (!(value is Array)) {
					value = [value];
				}
				_shader.data[name].value = value;
				return true;
			}
			return false;
		}

		/**
		* Returns the Shader instance this class wraps.
		*
		* @return The Shader instance managed by this class.
		*/
		public function get shader():Shader {
			return _shader;
		}

	}

}