import { Logger } from "../Misc/logger";
import { Nullable, FloatArray, IndicesArray } from "../types";
import { Engine } from "../Engines/engine";
import { RenderTargetCreationOptions } from "../Materials/Textures/renderTargetCreationOptions";
import { VertexBuffer } from "../Meshes/buffer";
import { InternalTexture, InternalTextureSource } from "../Materials/Textures/internalTexture";
import { Effect } from "../Materials/effect";
import { Constants } from "./constants";
import { IPipelineContext } from './IPipelineContext';
import { DataBuffer } from '../Meshes/dataBuffer';
import { IColor4Like, IViewportLike } from '../Maths/math.like';
import { ISceneLike } from './thinEngine';
import { PerformanceConfigurator } from './performanceConfigurator';

declare const global: any;

/**
 * Options to create the null engine
 */
export class NullEngineOptions {
    /**
     * Render width (Default: 512)
     */
    public renderWidth = 512;
    /**
     * Render height (Default: 256)
     */
    public renderHeight = 256;

    /**
     * Texture size (Default: 512)
     */
    public textureSize = 512;

    /**
     * If delta time between frames should be constant
     * @see https://doc.babylonjs.com/babylon101/animations#deterministic-lockstep
     */
    public deterministicLockstep = false;

    /**
     * Maximum about of steps between frames (Default: 4)
     * @see https://doc.babylonjs.com/babylon101/animations#deterministic-lockstep
     */
    public lockstepMaxSteps = 4;

    /**
     * Make the matrix computations to be performed in 64 bits instead of 32 bits. False by default
     */
    useHighPrecisionMatrix?: boolean;
}

/**
 * The null engine class provides support for headless version of babylon.js.
 * This can be used in server side scenario or for testing purposes
 */
export class NullEngine extends Engine {
    private _options: NullEngineOptions;

    /**
     * Gets a boolean indicating that the engine is running in deterministic lock step mode
     * @see https://doc.babylonjs.com/babylon101/animations#deterministic-lockstep
     * @returns true if engine is in deterministic lock step mode
     */
    public isDeterministicLockStep(): boolean {
        return this._options.deterministicLockstep;
    }

    /**
     * Gets the max steps when engine is running in deterministic lock step
     * @see https://doc.babylonjs.com/babylon101/animations#deterministic-lockstep
     * @returns the max steps
     */
    public getLockstepMaxSteps(): number {
        return this._options.lockstepMaxSteps;
    }

    /**
     * Gets the current hardware scaling level.
     * By default the hardware scaling level is computed from the window device ratio.
     * if level = 1 then the engine will render at the exact resolution of the canvas. If level = 0.5 then the engine will render at twice the size of the canvas.
     * @returns a number indicating the current hardware scaling level
     */
    public getHardwareScalingLevel(): number {
        return 1.0;
    }

    public constructor(options: NullEngineOptions = new NullEngineOptions()) {
        super(null);

        Engine.Instances.push(this);

        if (options.deterministicLockstep === undefined) {
            options.deterministicLockstep = false;
        }

        if (options.lockstepMaxSteps === undefined) {
            options.lockstepMaxSteps = 4;
        }

        this._options = options;

        PerformanceConfigurator.SetMatrixPrecision(!!options.useHighPrecisionMatrix);

        // Init caps
        // We consider we are on a webgl1 capable device

        this._caps = {
            maxTexturesImageUnits: 16,
            maxVertexTextureImageUnits: 16,
            maxCombinedTexturesImageUnits: 32,
            maxTextureSize: 512,
            maxCubemapTextureSize: 512,
            maxRenderTextureSize: 512,
            maxVertexAttribs: 16,
            maxVaryingVectors: 16,
            maxFragmentUniformVectors: 16,
            maxVertexUniformVectors: 16,
            standardDerivatives: false,
            astc: null,
            pvrtc: null,
            etc1: null,
            etc2: null,
            bptc: null,
            maxAnisotropy: 0,
            uintIndices: false,
            fragmentDepthSupported: false,
            highPrecisionShaderSupported: true,
            colorBufferFloat: false,
            textureFloat: false,
            textureFloatLinearFiltering: false,
            textureFloatRender: false,
            textureHalfFloat: false,
            textureHalfFloatLinearFiltering: false,
            textureHalfFloatRender: false,
            textureLOD: false,
            drawBuffersExtension: false,
            depthTextureExtension: false,
            vertexArrayObject: false,
            instancedArrays: false,
            canUseTimestampForTimerQuery: false,
            maxMSAASamples: 1,
            blendMinMax: false,
            canUseGLInstanceID: false,
        };

        this._features = {
            forceBitmapOverHTMLImageElement: false,
            supportRenderAndCopyToLodForFloatTextures: false,
            supportDepthStencilTexture: false,
            supportShadowSamplers: false,
            uniformBufferHardCheckMatrix: false,
            allowTexturePrefiltering: false,
            trackUbosInFrame: false,
            supportCSM: false,
            basisNeedsPOT: false,
            support3DTextures: false,
            needTypeSuffixInShaderConstants: false,
            supportMSAA: false,
            supportSSAO2: false,
            supportExtendedTextureFormats: false,
            supportSwitchCaseInShader: false,
            supportSyncTextureRead: false,
            _collectUbosUpdatedInFrame: false,
        };

        Logger.Log(`Babylon.js v${Engine.Version} - Null engine`);

        // Wrappers
        const theCurrentGlobal = (typeof self !== "undefined" ? self : typeof global !== "undefined" ? global : window);
        if (typeof URL === "undefined") {
            theCurrentGlobal.URL = {
                createObjectURL: function() { },
                revokeObjectURL: function() { }
            };
        }
        if (typeof Blob === "undefined") {
            theCurrentGlobal.Blob = function() { };
        }
    }

    /**
     * Creates a vertex buffer
     * @param vertices the data for the vertex buffer
     * @returns the new WebGL static buffer
     */
    public createVertexBuffer(vertices: FloatArray): DataBuffer {
        let buffer = new DataBuffer();
        buffer.references = 1;
        return buffer;
    }

    /**
     * Creates a new index buffer
     * @param indices defines the content of the index buffer
     * @param updatable defines if the index buffer must be updatable
     * @returns a new webGL buffer
     */
    public createIndexBuffer(indices: IndicesArray): DataBuffer {
        let buffer = new DataBuffer();
        buffer.references = 1;
        return buffer;
    }

    /**
     * Clear the current render buffer or the current render target (if any is set up)
     * @param color defines the color to use
     * @param backBuffer defines if the back buffer must be cleared
     * @param depth defines if the depth buffer must be cleared
     * @param stencil defines if the stencil buffer must be cleared
     */
    public clear(color: IColor4Like, backBuffer: boolean, depth: boolean, stencil: boolean = false): void {
    }

    /**
     * Gets the current render width
     * @param useScreen defines if screen size must be used (or the current render target if any)
     * @returns a number defining the current render width
     */
    public getRenderWidth(useScreen = false): number {
        if (!useScreen && this._currentRenderTarget) {
            return this._currentRenderTarget.width;
        }

        return this._options.renderWidth;
    }

    /**
     * Gets the current render height
     * @param useScreen defines if screen size must be used (or the current render target if any)
     * @returns a number defining the current render height
     */
    public getRenderHeight(useScreen = false): number {
        if (!useScreen && this._currentRenderTarget) {
            return this._currentRenderTarget.height;
        }

        return this._options.renderHeight;
    }

    /**
     * Set the WebGL's viewport
     * @param viewport defines the viewport element to be used
     * @param requiredWidth defines the width required for rendering. If not provided the rendering canvas' width is used
     * @param requiredHeight defines the height required for rendering. If not provided the rendering canvas' height is used
     */
    public setViewport(viewport: IViewportLike, requiredWidth?: number, requiredHeight?: number): void {
        this._cachedViewport = viewport;
    }

    public createShaderProgram(pipelineContext: IPipelineContext, vertexCode: string, fragmentCode: string, defines: string, context?: WebGLRenderingContext): WebGLProgram {
        return {
            __SPECTOR_rebuildProgram: null,
        };
    }

    /**
     * Gets the list of webGL uniform locations associated with a specific program based on a list of uniform names
     * @param pipelineContext defines the pipeline context to use
     * @param uniformsNames defines the list of uniform names
     * @returns an array of webGL uniform locations
     */
    public getUniforms(pipelineContext: IPipelineContext, uniformsNames: string[]): Nullable<WebGLUniformLocation>[] {
        return [];
    }

    /**
     * Gets the lsit of active attributes for a given webGL program
     * @param pipelineContext defines the pipeline context to use
     * @param attributesNames defines the list of attribute names to get
     * @returns an array of indices indicating the offset of each attribute
     */
    public getAttributes(pipelineContext: IPipelineContext, attributesNames: string[]): number[] {
        return [];
    }

    /**
     * Binds an effect to the webGL context
     * @param effect defines the effect to bind
     */
    public bindSamplers(effect: Effect): void {
        this._currentEffect = null;
    }

    /**
     * Activates an effect, mkaing it the current one (ie. the one used for rendering)
     * @param effect defines the effect to activate
     */
    public enableEffect(effect: Effect): void {
        this._currentEffect = effect;

        if (effect.onBind) {
            effect.onBind(effect);
        }
        if (effect._onBindObservable) {
            effect._onBindObservable.notifyObservers(effect);
        }
    }

    /**
     * Set various states to the webGL context
     * @param culling defines backface culling state
     * @param zOffset defines the value to apply to zOffset (0 by default)
     * @param force defines if states must be applied even if cache is up to date
     * @param reverseSide defines if culling must be reversed (CCW instead of CW and CW instead of CCW)
     */
    public setState(culling: boolean, zOffset: number = 0, force?: boolean, reverseSide = false): void {
    }

    /**
     * Set the value of an uniform to an array of int32
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     * @returns true if value was set
     */
    public setIntArray(uniform: WebGLUniformLocation, array: Int32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of int32 (stored as vec2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     * @returns true if value was set
     */
    public setIntArray2(uniform: WebGLUniformLocation, array: Int32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of int32 (stored as vec3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     * @returns true if value was set
     */
    public setIntArray3(uniform: WebGLUniformLocation, array: Int32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of int32 (stored as vec4)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of int32 to store
     * @returns true if value was set
     */
    public setIntArray4(uniform: WebGLUniformLocation, array: Int32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of float32
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     * @returns true if value was set
     */
    public setFloatArray(uniform: WebGLUniformLocation, array: Float32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as vec2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     * @returns true if value was set
     */
    public setFloatArray2(uniform: WebGLUniformLocation, array: Float32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as vec3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     * @returns true if value was set
     */
    public setFloatArray3(uniform: WebGLUniformLocation, array: Float32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as vec4)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of float32 to store
     * @returns true if value was set
     */
    public setFloatArray4(uniform: WebGLUniformLocation, array: Float32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of number
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     * @returns true if value was set
     */
    public setArray(uniform: WebGLUniformLocation, array: number[]): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of number (stored as vec2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     * @returns true if value was set
     */
    public setArray2(uniform: WebGLUniformLocation, array: number[]): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of number (stored as vec3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     * @returns true if value was set
     */
    public setArray3(uniform: WebGLUniformLocation, array: number[]): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of number (stored as vec4)
     * @param uniform defines the webGL uniform location where to store the value
     * @param array defines the array of number to store
     * @returns true if value was set
     */
    public setArray4(uniform: WebGLUniformLocation, array: number[]): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to an array of float32 (stored as matrices)
     * @param uniform defines the webGL uniform location where to store the value
     * @param matrices defines the array of float32 to store
     * @returns true if value was set
     */
    public setMatrices(uniform: WebGLUniformLocation, matrices: Float32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to a matrix (3x3)
     * @param uniform defines the webGL uniform location where to store the value
     * @param matrix defines the Float32Array representing the 3x3 matrix to store
     * @returns true if value was set
     */
    public setMatrix3x3(uniform: WebGLUniformLocation, matrix: Float32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to a matrix (2x2)
     * @param uniform defines the webGL uniform location where to store the value
     * @param matrix defines the Float32Array representing the 2x2 matrix to store
     * @returns true if value was set
     */
    public setMatrix2x2(uniform: WebGLUniformLocation, matrix: Float32Array): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to a number (float)
     * @param uniform defines the webGL uniform location where to store the value
     * @param value defines the float number to store
     * @returns true if value was set
     */
    public setFloat(uniform: WebGLUniformLocation, value: number): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to a vec2
     * @param uniform defines the webGL uniform location where to store the value
     * @param x defines the 1st component of the value
     * @param y defines the 2nd component of the value
     * @returns true if value was set
     */
    public setFloat2(uniform: WebGLUniformLocation, x: number, y: number): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to a vec3
     * @param uniform defines the webGL uniform location where to store the value
     * @param x defines the 1st component of the value
     * @param y defines the 2nd component of the value
     * @param z defines the 3rd component of the value
     * @returns true if value was set
     */
    public setFloat3(uniform: WebGLUniformLocation, x: number, y: number, z: number): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to a boolean
     * @param uniform defines the webGL uniform location where to store the value
     * @param bool defines the boolean to store
     * @returns true if value was set
     */
    public setBool(uniform: WebGLUniformLocation, bool: number): boolean {
        return true;
    }

    /**
     * Set the value of an uniform to a vec4
     * @param uniform defines the webGL uniform location where to store the value
     * @param x defines the 1st component of the value
     * @param y defines the 2nd component of the value
     * @param z defines the 3rd component of the value
     * @param w defines the 4th component of the value
     * @returns true if value was set
     */
    public setFloat4(uniform: WebGLUniformLocation, x: number, y: number, z: number, w: number): boolean {
        return true;
    }

    /**
     * Sets the current alpha mode
     * @param mode defines the mode to use (one of the Engine.ALPHA_XXX)
     * @param noDepthWriteChange defines if depth writing state should remains unchanged (false by default)
     * @see https://doc.babylonjs.com/resources/transparency_and_how_meshes_are_rendered
     */
    public setAlphaMode(mode: number, noDepthWriteChange: boolean = false): void {
        if (this._alphaMode === mode) {
            return;
        }

        this.alphaState.alphaBlend = (mode !== Constants.ALPHA_DISABLE);

        if (!noDepthWriteChange) {
            this.setDepthWrite(mode === Constants.ALPHA_DISABLE);
        }
        this._alphaMode = mode;
    }

    /**
     * Bind webGl buffers directly to the webGL context
     * @param vertexBuffers defines the vertex buffer to bind
     * @param indexBuffer defines the index buffer to bind
     * @param vertexDeclaration defines the vertex declaration to use with the vertex buffer
     * @param vertexStrideSize defines the vertex stride of the vertex buffer
     * @param effect defines the effect associated with the vertex buffer
     */
    public bindBuffers(vertexBuffers: { [key: string]: VertexBuffer; }, indexBuffer: DataBuffer, effect: Effect): void {
    }

    /**
     * Force the entire cache to be cleared
     * You should not have to use this function unless your engine needs to share the webGL context with another engine
     * @param bruteForce defines a boolean to force clearing ALL caches (including stencil, detoh and alpha states)
     */
    public wipeCaches(bruteForce?: boolean): void {
        if (this.preventCacheWipeBetweenFrames) {
            return;
        }
        this.resetTextureCache();
        this._currentEffect = null;

        if (bruteForce) {
            this._currentProgram = null;

            this.stencilState.reset();
            this.depthCullingState.reset();
            this.alphaState.reset();
        }

        this._cachedVertexBuffers = null;
        this._cachedIndexBuffer = null;
        this._cachedEffectForVertexBuffers = null;
    }

    /**
     * Send a draw order
     * @param useTriangles defines if triangles must be used to draw (else wireframe will be used)
     * @param indexStart defines the starting index
     * @param indexCount defines the number of index to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public draw(useTriangles: boolean, indexStart: number, indexCount: number, instancesCount?: number): void {
    }

    /**
     * Draw a list of indexed primitives
     * @param fillMode defines the primitive to use
     * @param indexStart defines the starting index
     * @param indexCount defines the number of index to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public drawElementsType(fillMode: number, indexStart: number, indexCount: number, instancesCount?: number): void {
    }

    /**
     * Draw a list of unindexed primitives
     * @param fillMode defines the primitive to use
     * @param verticesStart defines the index of first vertex to draw
     * @param verticesCount defines the count of vertices to draw
     * @param instancesCount defines the number of instances to draw (if instanciation is enabled)
     */
    public drawArraysType(fillMode: number, verticesStart: number, verticesCount: number, instancesCount?: number): void {
    }

    /** @hidden */
    protected _createTexture(): WebGLTexture {
        return {};
    }

    /** @hidden */
    public _releaseTexture(texture: InternalTexture): void {
    }

    /**
     * Usually called from Texture.ts.
     * Passed information to create a WebGLTexture
     * @param urlArg defines a value which contains one of the following:
     * * A conventional http URL, e.g. 'http://...' or 'file://...'
     * * A base64 string of in-line texture data, e.g. 'data:image/jpg;base64,/...'
     * * An indicator that data being passed using the buffer parameter, e.g. 'data:mytexture.jpg'
     * @param noMipmap defines a boolean indicating that no mipmaps shall be generated.  Ignored for compressed textures.  They must be in the file
     * @param invertY when true, image is flipped when loaded.  You probably want true. Certain compressed textures may invert this if their default is inverted (eg. ktx)
     * @param scene needed for loading to the correct scene
     * @param samplingMode mode with should be used sample / access the texture (Default: Texture.TRILINEAR_SAMPLINGMODE)
     * @param onLoad optional callback to be called upon successful completion
     * @param onError optional callback to be called upon failure
     * @param buffer a source of a file previously fetched as either a base64 string, an ArrayBuffer (compressed or image format), HTMLImageElement (image format), or a Blob
     * @param fallback an internal argument in case the function must be called again, due to etc1 not having alpha capabilities
     * @param format internal format.  Default: RGB when extension is '.jpg' else RGBA.  Ignored for compressed textures
     * @param forcedExtension defines the extension to use to pick the right loader
     * @param mimeType defines an optional mime type
     * @returns a InternalTexture for assignment back into BABYLON.Texture
     */
    public createTexture(urlArg: Nullable<string>, noMipmap: boolean, invertY: boolean, scene: Nullable<ISceneLike>, samplingMode: number = Constants.TEXTURE_TRILINEAR_SAMPLINGMODE,
        onLoad: Nullable<() => void> = null, onError: Nullable<(message: string, exception: any) => void> = null,
        buffer: Nullable<string | ArrayBuffer | ArrayBufferView | HTMLImageElement | Blob | ImageBitmap> = null, fallback: Nullable<InternalTexture> = null, format: Nullable<number> = null,
        forcedExtension: Nullable<string> = null, mimeType?: string): InternalTexture {
        var texture = new InternalTexture(this, InternalTextureSource.Url);
        var url = String(urlArg);

        texture.url = url;
        texture.generateMipMaps = !noMipmap;
        texture.samplingMode = samplingMode;
        texture.invertY = invertY;
        texture.baseWidth = this._options.textureSize;
        texture.baseHeight = this._options.textureSize;
        texture.width = this._options.textureSize;
        texture.height = this._options.textureSize;
        if (format) {
            texture.format = format;
        }

        texture.isReady = true;

        if (onLoad) {
            onLoad();
        }

        this._internalTexturesCache.push(texture);

        return texture;
    }

    /**
     * Creates a new render target texture
     * @param size defines the size of the texture
     * @param options defines the options used to create the texture
     * @returns a new render target texture stored in an InternalTexture
     */
    public createRenderTargetTexture(size: any, options: boolean | RenderTargetCreationOptions): InternalTexture {
        let fullOptions = new RenderTargetCreationOptions();

        if (options !== undefined && typeof options === "object") {
            fullOptions.generateMipMaps = options.generateMipMaps;
            fullOptions.generateDepthBuffer = options.generateDepthBuffer === undefined ? true : options.generateDepthBuffer;
            fullOptions.generateStencilBuffer = fullOptions.generateDepthBuffer && options.generateStencilBuffer;
            fullOptions.type = options.type === undefined ? Constants.TEXTURETYPE_UNSIGNED_INT : options.type;
            fullOptions.samplingMode = options.samplingMode === undefined ? Constants.TEXTURE_TRILINEAR_SAMPLINGMODE : options.samplingMode;
        } else {
            fullOptions.generateMipMaps = <boolean>options;
            fullOptions.generateDepthBuffer = true;
            fullOptions.generateStencilBuffer = false;
            fullOptions.type = Constants.TEXTURETYPE_UNSIGNED_INT;
            fullOptions.samplingMode = Constants.TEXTURE_TRILINEAR_SAMPLINGMODE;
        }
        var texture = new InternalTexture(this, InternalTextureSource.RenderTarget);

        var width = size.width || size;
        var height = size.height || size;

        texture._depthStencilBuffer = {};
        texture._framebuffer = {};
        texture.baseWidth = width;
        texture.baseHeight = height;
        texture.width = width;
        texture.height = height;
        texture.isReady = true;
        texture.samples = 1;
        texture.generateMipMaps = fullOptions.generateMipMaps ? true : false;
        texture.samplingMode = fullOptions.samplingMode;
        texture.type = fullOptions.type;
        texture._generateDepthBuffer = fullOptions.generateDepthBuffer;
        texture._generateStencilBuffer = fullOptions.generateStencilBuffer ? true : false;

        this._internalTexturesCache.push(texture);

        return texture;
    }

    /**
     * Update the sampling mode of a given texture
     * @param samplingMode defines the required sampling mode
     * @param texture defines the texture to update
     */
    public updateTextureSamplingMode(samplingMode: number, texture: InternalTexture): void {
        texture.samplingMode = samplingMode;
    }

    /**
     * Binds the frame buffer to the specified texture.
     * @param texture The texture to render to or null for the default canvas
     * @param faceIndex The face of the texture to render to in case of cube texture
     * @param requiredWidth The width of the target to render to
     * @param requiredHeight The height of the target to render to
     * @param forceFullscreenViewport Forces the viewport to be the entire texture/screen if true
     * @param lodLevel defines le lod level to bind to the frame buffer
     */
    public bindFramebuffer(texture: InternalTexture, faceIndex?: number, requiredWidth?: number, requiredHeight?: number, forceFullscreenViewport?: boolean): void {
        if (this._currentRenderTarget) {
            this.unBindFramebuffer(this._currentRenderTarget);
        }
        this._currentRenderTarget = texture;
        this._currentFramebuffer = texture._MSAAFramebuffer ? texture._MSAAFramebuffer : texture._framebuffer;
        if (this._cachedViewport && !forceFullscreenViewport) {
            this.setViewport(this._cachedViewport, requiredWidth, requiredHeight);
        }
    }

    /**
     * Unbind the current render target texture from the webGL context
     * @param texture defines the render target texture to unbind
     * @param disableGenerateMipMaps defines a boolean indicating that mipmaps must not be generated
     * @param onBeforeUnbind defines a function which will be called before the effective unbind
     */
    public unBindFramebuffer(texture: InternalTexture, disableGenerateMipMaps = false, onBeforeUnbind?: () => void): void {
        this._currentRenderTarget = null;

        if (onBeforeUnbind) {
            if (texture._MSAAFramebuffer) {
                this._currentFramebuffer = texture._framebuffer;
            }
            onBeforeUnbind();
        }
        this._currentFramebuffer = null;
    }

    /**
     * Creates a dynamic vertex buffer
     * @param vertices the data for the dynamic vertex buffer
     * @returns the new WebGL dynamic buffer
     */
    public createDynamicVertexBuffer(vertices: FloatArray): DataBuffer {
        let buffer = new DataBuffer();
        buffer.references = 1;
        buffer.capacity = 1;
        return buffer;
    }

    /**
     * Update the content of a dynamic texture
     * @param texture defines the texture to update
     * @param canvas defines the canvas containing the source
     * @param invertY defines if data must be stored with Y axis inverted
     * @param premulAlpha defines if alpha is stored as premultiplied
     * @param format defines the format of the data
     * @param forceBindTexture if the texture should be forced to be bound eg. after a graphics context loss (Default: false)
     */
    public updateDynamicTexture(texture: Nullable<InternalTexture>, canvas: HTMLCanvasElement, invertY: boolean, premulAlpha: boolean = false, format?: number): void {

    }

    /**
     * Gets a boolean indicating if all created effects are ready
     * @returns true if all effects are ready
     */
    public areAllEffectsReady(): boolean {
        return true;
    }

    /**
     * @hidden
     * Get the current error code of the webGL context
     * @returns the error code
     * @see https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/getError
     */
    public getError(): number {
        return 0;
    }

    /** @hidden */
    public _getUnpackAlignement(): number {
        return 1;
    }

    /** @hidden */
    public _unpackFlipY(value: boolean) {
    }

    /**
     * Update a dynamic index buffer
     * @param indexBuffer defines the target index buffer
     * @param indices defines the data to update
     * @param offset defines the offset in the target index buffer where update should start
     */
    public updateDynamicIndexBuffer(indexBuffer: WebGLBuffer, indices: IndicesArray, offset: number = 0): void {
    }

    /**
     * Updates a dynamic vertex buffer.
     * @param vertexBuffer the vertex buffer to update
     * @param vertices the data used to update the vertex buffer
     * @param byteOffset the byte offset of the data (optional)
     * @param byteLength the byte length of the data (optional)
     */
    public updateDynamicVertexBuffer(vertexBuffer: WebGLBuffer, vertices: FloatArray, byteOffset?: number, byteLength?: number): void {
    }

    /** @hidden */
    public _bindTextureDirectly(target: number, texture: InternalTexture): boolean {
        if (this._boundTexturesCache[this._activeChannel] !== texture) {
            this._boundTexturesCache[this._activeChannel] = texture;
            return true;
        }
        return false;
    }

    /** @hidden */
    public _bindTexture(channel: number, texture: InternalTexture): void {
        if (channel < 0) {
            return;
        }

        this._bindTextureDirectly(0, texture);
    }

    protected _deleteBuffer(buffer: WebGLBuffer): void {
    }

    /**
     * Force the engine to release all cached effects. This means that next effect compilation will have to be done completely even if a similar effect was already compiled
     */
    public releaseEffects() {
    }

    public displayLoadingUI(): void {
    }

    public hideLoadingUI(): void {
    }

    /** @hidden */
    public _uploadCompressedDataToTextureDirectly(texture: InternalTexture, internalFormat: number, width: number, height: number, data: ArrayBufferView, faceIndex: number = 0, lod: number = 0) {
    }

    /** @hidden */
    public _uploadDataToTextureDirectly(texture: InternalTexture, imageData: ArrayBufferView, faceIndex: number = 0, lod: number = 0): void {
    }

    /** @hidden */
    public _uploadArrayBufferViewToTexture(texture: InternalTexture, imageData: ArrayBufferView, faceIndex: number = 0, lod: number = 0): void {
    }

    /** @hidden */
    public _uploadImageToTexture(texture: InternalTexture, image: HTMLImageElement, faceIndex: number = 0, lod: number = 0) {
    }
}