module BABYLON {
    export type PostProcessOptions = { width: number, height: number };

    /**
	 * PostProcess can be used to apply a shader to a texture after it has been rendered
     * See https://doc.babylonjs.com/how_to/how_to_use_postprocesses
     */
    export class PostProcess {
        /**
        * Width of the texture to apply the post process on
        */
        public width = -1;
        /**
        * Height of the texture to apply the post process on
        */
        public height = -1;

        /**
        * Internal, reference to the location where this postprocess was output to. (Typically the texture on the next postprocess in the chain)
        */
        public _outputTexture: Nullable<InternalTexture> = null;
        /**
        * Sampling mode used by the shader
        * See https://doc.babylonjs.com/classes/3.1/texture
        */
        public renderTargetSamplingMode: number;
        /**
        * Clear color to use when screen clearing
        */
        public clearColor: Color4;
        /**
        * If the buffer needs to be cleared before applying the post process. (default: true)
        * Should be set to false if shader will overwrite all previous pixels.
        */
        public autoClear = true;
        /**
        * Type of alpha mode to use when performing the post process (default: Engine.ALPHA_DISABLE)
        */
        public alphaMode = Engine.ALPHA_DISABLE;
        /**
        * Sets the setAlphaBlendConstants of the babylon engine
        */
        public alphaConstants: Color4;
        /**
        * Animations to be used for the post processing 
        */
        public animations = new Array<Animation>();

        /**
         * Enable Pixel Perfect mode where texture is not scaled to be power of 2.
         * Can only be used on a single postprocess or on the last one of a chain. (default: false)
         */
        public enablePixelPerfectMode = false;

        /**
         * Force the postprocess to be applied without taking in account viewport
         */
        public forceFullscreenViewport = true;

        /**
        * Scale mode for the post process (default: Engine.SCALEMODE_FLOOR)
        */
        public scaleMode = Engine.SCALEMODE_FLOOR;
        /**
        * Force textures to be a power of two (default: false)
        */
        public alwaysForcePOT = false;
        /**
        * Number of sample textures (default: 1)
        */
        public samples = 1;
        /**
        * Modify the scale of the post process to be the same as the viewport (default: false)
        */
        public adaptScaleToCurrentViewport = false;

        private _camera: Camera;
        private _scene: Scene;
        private _engine: Engine;
        
        private _options: number | PostProcessOptions;
        private _reusable = false;
        private _textureType: number;
        /**
        * Smart array of input and output textures for the post process.
        */
        public _textures = new SmartArray<InternalTexture>(2);
        /**
        * The index in _textures that corresponds to the output texture.
        */
        public _currentRenderTextureInd = 0;
        private _effect: Effect;
        private _samplers: string[];
        private _fragmentUrl: string;
        private _vertexUrl: string;
        private _parameters: string[];
        private _scaleRatio = new Vector2(1, 1);
        protected _indexParameters: any;
        private _shareOutputWithPostProcess: Nullable<PostProcess>;
        private _texelSize = Vector2.Zero();
        private _forcedOutputTexture: InternalTexture;

        // Events

        /**
        * An event triggered when the postprocess is activated.
        */
        public onActivateObservable = new Observable<Camera>();

        private _onActivateObserver: Nullable<Observer<Camera>>;
        /**
        * A function that is added to the onActivateObservable
        */
        public set onActivate(callback: Nullable<(camera: Camera) => void>) {
            if (this._onActivateObserver) {
                this.onActivateObservable.remove(this._onActivateObserver);
            }
            if (callback) {
                this._onActivateObserver = this.onActivateObservable.add(callback);
            }
        }

        /**
        * An event triggered when the postprocess changes its size.
        */
        public onSizeChangedObservable = new Observable<PostProcess>();

        private _onSizeChangedObserver: Nullable<Observer<PostProcess>>;
        /**
        * A function that is added to the onSizeChangedObservable
        */
        public set onSizeChanged(callback: (postProcess: PostProcess) => void) {
            if (this._onSizeChangedObserver) {
                this.onSizeChangedObservable.remove(this._onSizeChangedObserver);
            }
            this._onSizeChangedObserver = this.onSizeChangedObservable.add(callback);
        }

        /**
        * An event triggered when the postprocess applies its effect.
        */
        public onApplyObservable = new Observable<Effect>();

        private _onApplyObserver: Nullable<Observer<Effect>>;
        /**
        * A function that is added to the onApplyObservable
        */
        public set onApply(callback: (effect: Effect) => void) {
            if (this._onApplyObserver) {
                this.onApplyObservable.remove(this._onApplyObserver);
            }
            this._onApplyObserver = this.onApplyObservable.add(callback);
        }

        /**
        * An event triggered before rendering the postprocess
        */
        public onBeforeRenderObservable = new Observable<Effect>();

        private _onBeforeRenderObserver: Nullable<Observer<Effect>>;
        /**
        * A function that is added to the onBeforeRenderObservable
        */
        public set onBeforeRender(callback: (effect: Effect) => void) {
            if (this._onBeforeRenderObserver) {
                this.onBeforeRenderObservable.remove(this._onBeforeRenderObserver);
            }
            this._onBeforeRenderObserver = this.onBeforeRenderObservable.add(callback);
        }

        /**
        * An event triggered after rendering the postprocess
        */
        public onAfterRenderObservable = new Observable<Effect>();

        private _onAfterRenderObserver: Nullable<Observer<Effect>>;
        /**
        * A function that is added to the onAfterRenderObservable
        */
        public set onAfterRender(callback: (efect: Effect) => void) {
            if (this._onAfterRenderObserver) {
                this.onAfterRenderObservable.remove(this._onAfterRenderObserver);
            }
            this._onAfterRenderObserver = this.onAfterRenderObservable.add(callback);
        }

        /**
        * The input texture for this post process and the output texture of the previous post process. When added to a pipeline the previous post process will
        * render it's output into this texture and this texture will be used as textureSampler in the fragment shader of this post process.
        */
        public get inputTexture(): InternalTexture {
            return this._textures.data[this._currentRenderTextureInd];
        }

        public set inputTexture(value: InternalTexture) {
            this._forcedOutputTexture = value;
        }

        /**
        * Gets the camera which post process is applied to.
        * @returns The camera the post process is applied to.
        */
        public getCamera(): Camera {
            return this._camera;
        }

        /**
        * Gets the texel size of the postprocess.
        * See https://en.wikipedia.org/wiki/Texel_(graphics)
        */
        public get texelSize(): Vector2 {
            if (this._shareOutputWithPostProcess) {
                return this._shareOutputWithPostProcess.texelSize;
            }

            if (this._forcedOutputTexture) {
                this._texelSize.copyFromFloats(1.0 / this._forcedOutputTexture.width, 1.0 / this._forcedOutputTexture.height);
            }

            return this._texelSize;
        }

        /**
         * Creates a new instance PostProcess
         * @param name The name of the PostProcess.
         * @param fragmentUrl The url of the fragment shader to be used.
		 * @param parameters Array of the names of uniform non-sampler2D variables that will be passed to the shader.
         * @param samplers Array of the names of uniform sampler2D variables that will be passed to the shader.
         * @param options The required width/height ratio to downsize to before computing the render pass. (Use 1.0 for full size)
         * @param camera The camera to apply the render pass to.
         * @param samplingMode The sampling mode to be used when computing the pass. (default: 0)
         * @param engine The engine which the post process will be applied. (default: current engine)
         * @param reusable If the post process can be reused on the same frame. (default: false)
         * @param defines String of defines that will be set when running the fragment shader. (default: null)
         * @param textureType Type of textures used when performing the post process. (default: 0)
         * @param vertexUrl The url of the vertex shader to be used. (default: "postprocess")
         * @param indexParameters The index parameters to be used for babylons include syntax "#include<kernelBlurVaryingDeclaration>[0..varyingCount]". (default: undefined) See usage in babylon.blurPostProcess.ts and kernelBlur.vertex.fx
         * @param blockCompilation If the shader should not be compiled imediatly. (default: false) 
         */
        constructor(/** Name of the PostProcess. */public name: string, fragmentUrl: string, parameters: Nullable<string[]>, samplers: Nullable<string[]>, options: number | PostProcessOptions, camera: Nullable<Camera>,
            samplingMode: number = Texture.NEAREST_SAMPLINGMODE, engine?: Engine, reusable?: boolean, defines: Nullable<string> = null, textureType: number = Engine.TEXTURETYPE_UNSIGNED_INT, vertexUrl: string = "postprocess", indexParameters?: any, blockCompilation = false) {
            if (camera != null) {
                this._camera = camera;
                this._scene = camera.getScene();
                camera.attachPostProcess(this);
                this._engine = this._scene.getEngine();

                this._scene.postProcesses.push(this);
            }
            else if (engine) {
                this._engine = engine;
                this._engine.postProcesses.push(this);
            }

            this._options = options;
            this.renderTargetSamplingMode = samplingMode ? samplingMode : Texture.NEAREST_SAMPLINGMODE;
            this._reusable = reusable || false;
            this._textureType = textureType;

            this._samplers = samplers || [];
            this._samplers.push("textureSampler");

            this._fragmentUrl = fragmentUrl;
            this._vertexUrl = vertexUrl;
            this._parameters = parameters || [];

            this._parameters.push("scale");

            this._indexParameters = indexParameters;

            if (!blockCompilation) {
                this.updateEffect(defines);
            }
        }

        /**
         * Gets the engine which this post process belongs to.
         * @returns The engine the post process was enabled with.
         */
        public getEngine(): Engine {
            return this._engine;
        }

        /**
         * The effect that is created when initializing the post process.
         * @returns The created effect corrisponding the the postprocess.
         */
        public getEffect(): Effect {
            return this._effect;
        }

        /**
         * To avoid multiple redundant textures for multiple post process, the output the output texture for this post process can be shared with another.
         * @param postProcess The post process to share the output with.
         * @returns This post process.
         */
        public shareOutputWith(postProcess: PostProcess): PostProcess {
            this._disposeTextures();

            this._shareOutputWithPostProcess = postProcess;

            return this;
        }

        /**
         * Reverses the effect of calling shareOutputWith and returns the post process back to its original state. 
         * This should be called if the post process that shares output with this post process is disabled/disposed.
         */
        public useOwnOutput() {
            if(this._textures.length == 0){
                this._textures = new SmartArray<InternalTexture>(2);
            }

            this._shareOutputWithPostProcess = null;
        }

        /**
         * Updates the effect with the current post process compile time values and recompiles the shader.
         * @param defines Define statements that should be added at the beginning of the shader. (default: null)
         * @param uniforms Set of uniform variables that will be passed to the shader. (default: null)
         * @param samplers Set of Texture2D variables that will be passed to the shader. (default: null)
         * @param indexParameters The index parameters to be used for babylons include syntax "#include<kernelBlurVaryingDeclaration>[0..varyingCount]". (default: undefined) See usage in babylon.blurPostProcess.ts and kernelBlur.vertex.fx
         * @param onCompiled Called when the shader has been compiled.
         * @param onError Called if there is an error when compiling a shader.
         */
        public updateEffect(defines: Nullable<string> = null, uniforms: Nullable<string[]> = null, samplers: Nullable<string[]> = null, indexParameters?: any,
            onCompiled?: (effect: Effect) => void, onError?: (effect: Effect, errors: string) => void) {
            this._effect = this._engine.createEffect({ vertex: this._vertexUrl, fragment: this._fragmentUrl },
                ["position"],
                uniforms || this._parameters,
                samplers || this._samplers,
                defines !== null ? defines : "",
                undefined,
                onCompiled,
                onError,
                indexParameters || this._indexParameters
            );
        }

        /**
         * The post process is reusable if it can be used multiple times within one frame.
         * @returns If the post process is reusable
         */
        public isReusable(): boolean {
            return this._reusable;
        }

        /** invalidate frameBuffer to hint the postprocess to create a depth buffer */
        public markTextureDirty(): void {
            this.width = -1;
        }

        /**
         * Activates the post process by intializing the textures to be used when executed. Notifies onActivateObservable.
         * When this post process is used in a pipeline, this is call will bind the input texture of this post process to the output of the previous.
         * @param camera The camera that will be used in the post process. This camera will be used when calling onActivateObservable.
         * @param sourceTexture The source texture to be inspected to get the width and height if not specified in the post process constructor. (default: null)
         * @param forceDepthStencil If true, a depth and stencil buffer will be generated. (default: false)
         * @returns The target texture that was bound to be written to. 
         */
        public activate(camera: Nullable<Camera>, sourceTexture: Nullable<InternalTexture> = null, forceDepthStencil?: boolean): InternalTexture {
            camera = camera || this._camera;

            var scene = camera.getScene();
            var engine = scene.getEngine();
            var maxSize = engine.getCaps().maxTextureSize;

            var requiredWidth = ((sourceTexture ? sourceTexture.width : this._engine.getRenderWidth(true)) * <number>this._options) | 0;
            var requiredHeight = ((sourceTexture ? sourceTexture.height : this._engine.getRenderHeight(true)) * <number>this._options) | 0;

            // If rendering to a webvr camera's left or right eye only half the width should be used to avoid resize when rendered to screen
            var webVRCamera = (<WebVRFreeCamera>camera.parent);
            if(webVRCamera && (webVRCamera.leftCamera == camera || webVRCamera.rightCamera == camera)){
                requiredWidth/=2;
            }

            var desiredWidth = ((<PostProcessOptions>this._options).width || requiredWidth);
            var desiredHeight = (<PostProcessOptions>this._options).height || requiredHeight;

            if (!this._shareOutputWithPostProcess && !this._forcedOutputTexture) {

                if (this.adaptScaleToCurrentViewport) {
                    let currentViewport = engine.currentViewport;

                    if (currentViewport) {
                        desiredWidth *= currentViewport.width;
                        desiredHeight *= currentViewport.height;
                    }
                }

                if (this.renderTargetSamplingMode === Texture.TRILINEAR_SAMPLINGMODE || this.alwaysForcePOT) {
                    if (!(<PostProcessOptions>this._options).width) {
                        desiredWidth = engine.needPOTTextures ? Tools.GetExponentOfTwo(desiredWidth, maxSize, this.scaleMode) : desiredWidth;
                    }

                    if (!(<PostProcessOptions>this._options).height) {
                        desiredHeight = engine.needPOTTextures ? Tools.GetExponentOfTwo(desiredHeight, maxSize, this.scaleMode) : desiredHeight;
                    }
                }

                if (this.width !== desiredWidth || this.height !== desiredHeight) {
                    if (this._textures.length > 0) {
                        for (var i = 0; i < this._textures.length; i++) {
                            this._engine._releaseTexture(this._textures.data[i]);
                        }
                        this._textures.reset();
                    }
                    this.width = desiredWidth;
                    this.height = desiredHeight;

                    let textureSize = { width: this.width, height: this.height };
                    let textureOptions = {
                        generateMipMaps: false,
                        generateDepthBuffer: forceDepthStencil || camera._postProcesses.indexOf(this) === 0,
                        generateStencilBuffer: (forceDepthStencil || camera._postProcesses.indexOf(this) === 0) && this._engine.isStencilEnable,
                        samplingMode: this.renderTargetSamplingMode,
                        type: this._textureType
                    };

                    this._textures.push(this._engine.createRenderTargetTexture(textureSize, textureOptions));

                    if (this._reusable) {
                        this._textures.push(this._engine.createRenderTargetTexture(textureSize, textureOptions));
                    }

                    this._texelSize.copyFromFloats(1.0 / this.width, 1.0 / this.height);

                    this.onSizeChangedObservable.notifyObservers(this);
                }

                this._textures.forEach(texture => {
                    if (texture.samples !== this.samples) {
                        this._engine.updateRenderTargetTextureSampleCount(texture, this.samples);
                    }
                });
            }

            var target: InternalTexture;

            if (this._shareOutputWithPostProcess) {
                target = this._shareOutputWithPostProcess.inputTexture;
            } else if (this._forcedOutputTexture) {
                target = this._forcedOutputTexture;

                this.width = this._forcedOutputTexture.width;
                this.height = this._forcedOutputTexture.height;
            } else {
                target = this.inputTexture;
            }

            // Bind the input of this post process to be used as the output of the previous post process.
            if (this.enablePixelPerfectMode) {
                this._scaleRatio.copyFromFloats(requiredWidth / desiredWidth, requiredHeight / desiredHeight);
                this._engine.bindFramebuffer(target, 0, requiredWidth, requiredHeight, this.forceFullscreenViewport);
            }
            else {
                this._scaleRatio.copyFromFloats(1, 1);
                this._engine.bindFramebuffer(target, 0, undefined, undefined, this.forceFullscreenViewport);
            }

            this.onActivateObservable.notifyObservers(camera);

            // Clear
            if (this.autoClear && this.alphaMode === Engine.ALPHA_DISABLE) {
                this._engine.clear(this.clearColor ? this.clearColor : scene.clearColor, true, true, true);
            }

            if (this._reusable) {
                this._currentRenderTextureInd = (this._currentRenderTextureInd + 1) % 2;
            }
            return target;
        }


        /**
         * If the post process is supported.
         */
        public get isSupported(): boolean {
            return this._effect.isSupported;
        }

        /**
         * The aspect ratio of the output texture.
         */
        public get aspectRatio(): number {
            if (this._shareOutputWithPostProcess) {
                return this._shareOutputWithPostProcess.aspectRatio;
            }

            if (this._forcedOutputTexture) {
                return this._forcedOutputTexture.width / this._forcedOutputTexture.height;
            }
            return this.width / this.height;
        }

        /**
         * Get a value indicating if the post-process is ready to be used
         * @returns true if the post-process is ready (shader is compiled)
         */
        public isReady(): boolean {
            return this._effect && this._effect.isReady();
        }

        /**
         * Binds all textures and uniforms to the shader, this will be run on every pass.
         * @returns the effect corrisponding to this post process. Null if not compiled or not ready.
         */
        public apply(): Nullable<Effect> {
            // Check
            if (!this._effect || !this._effect.isReady())
                return null;

            // States
            this._engine.enableEffect(this._effect);
            this._engine.setState(false);
            this._engine.setDepthBuffer(false);
            this._engine.setDepthWrite(false);

            // Alpha
            this._engine.setAlphaMode(this.alphaMode);
            if (this.alphaConstants) {
                this.getEngine().setAlphaConstants(this.alphaConstants.r, this.alphaConstants.g, this.alphaConstants.b, this.alphaConstants.a);
            }

            // Bind the output texture of the preivous post process as the input to this post process.            
            var source: InternalTexture;
            if (this._shareOutputWithPostProcess) {
                source = this._shareOutputWithPostProcess.inputTexture;
            } else if (this._forcedOutputTexture) {
                source = this._forcedOutputTexture;
            } else {
                source = this.inputTexture;
            }
            this._effect._bindTexture("textureSampler", source);

            // Parameters
            this._effect.setVector2("scale", this._scaleRatio);
            this.onApplyObservable.notifyObservers(this._effect);

            return this._effect;
        }

        private _disposeTextures() {
            if (this._shareOutputWithPostProcess || this._forcedOutputTexture) {
                return;
            }

            if (this._textures.length > 0) {
                for (var i = 0; i < this._textures.length; i++) {
                    this._engine._releaseTexture(this._textures.data[i]);
                }
            }
            this._textures.dispose();
        }

        /**
         * Disposes the post process.
         * @param camera The camera to dispose the post process on.
         */
        public dispose(camera?: Camera): void {
            camera = camera || this._camera;

            this._disposeTextures();

            if (this._scene) {
                let index = this._scene.postProcesses.indexOf(this);
                if (index !== -1) {
                    this._scene.postProcesses.splice(index, 1);
                }
            } else {
                let index = this._engine.postProcesses.indexOf(this);
                if (index !== -1) {
                    this._engine.postProcesses.splice(index, 1);
                }
            }

            if (!camera) {
                return;
            }
            camera.detachPostProcess(this);

            var index = camera._postProcesses.indexOf(this);
            if (index === 0 && camera._postProcesses.length > 0) {
                var firstPostProcess = this._camera._getFirstPostProcess();
                if(firstPostProcess){
                    firstPostProcess.markTextureDirty();
                }
            }

            this.onActivateObservable.clear();
            this.onAfterRenderObservable.clear();
            this.onApplyObservable.clear();
            this.onBeforeRenderObservable.clear();
            this.onSizeChangedObservable.clear();
        }
    }
}