/*// debugger tools
import 'https://greggman.github.io/webgpu-avoid-redundant-state-setting/webgpu-check-redundant-state-setting.js';
//*/

import { GPUFeatureName, GPUTextureFormat, GPULoadOp, GPUStoreOp, GPUIndexFormat, GPUTextureViewDimension } from './utils/WebGPUConstants.js';

import WGSLNodeBuilder from './nodes/WGSLNodeBuilder.js';
import Backend from '../common/Backend.js';

import WebGPUUtils from './utils/WebGPUUtils.js';
import WebGPUAttributeUtils from './utils/WebGPUAttributeUtils.js';
import WebGPUBindingUtils from './utils/WebGPUBindingUtils.js';
import WebGPUPipelineUtils from './utils/WebGPUPipelineUtils.js';
import WebGPUTextureUtils from './utils/WebGPUTextureUtils.js';

import { WebGPUCoordinateSystem } from '../../constants.js';

//

class WebGPUBackend extends Backend {

	constructor( parameters = {} ) {

		super( parameters );

		this.isWebGPUBackend = true;

		// some parameters require default values other than "undefined"
		this.parameters.alpha = ( parameters.alpha === undefined ) ? true : parameters.alpha;

		this.parameters.requiredLimits = ( parameters.requiredLimits === undefined ) ? {} : parameters.requiredLimits;

		this.trackTimestamp = ( parameters.trackTimestamp === true );

		this.device = null;
		this.context = null;
		this.colorBuffer = null;
		this.defaultRenderPassdescriptor = null;

		this.utils = new WebGPUUtils( this );
		this.attributeUtils = new WebGPUAttributeUtils( this );
		this.bindingUtils = new WebGPUBindingUtils( this );
		this.pipelineUtils = new WebGPUPipelineUtils( this );
		this.textureUtils = new WebGPUTextureUtils( this );
		this.occludedResolveCache = new Map();

	}

	async init( renderer ) {

		await super.init( renderer );

		//

		const parameters = this.parameters;

		// create the device if it is not passed with parameters

		let device;

		if ( parameters.device === undefined ) {

			const adapterOptions = {
				powerPreference: parameters.powerPreference
			};

			const adapter = await navigator.gpu.requestAdapter( adapterOptions );

			if ( adapter === null ) {

				throw new Error( 'WebGPUBackend: Unable to create WebGPU adapter.' );

			}

			// feature support

			const features = Object.values( GPUFeatureName );

			const supportedFeatures = [];

			for ( const name of features ) {

				if ( adapter.features.has( name ) ) {

					supportedFeatures.push( name );

				}

			}

			const deviceDescriptor = {
				requiredFeatures: supportedFeatures,
				requiredLimits: parameters.requiredLimits
			};

			device = await adapter.requestDevice( deviceDescriptor );

		} else {

			device = parameters.device;

		}

		const context = ( parameters.context !== undefined ) ? parameters.context : renderer.domElement.getContext( 'webgpu' );

		this.device = device;
		this.context = context;

		const alphaMode = parameters.alpha ? 'premultiplied' : 'opaque';

		this.context.configure( {
			device: this.device,
			format: GPUTextureFormat.BGRA8Unorm,
			usage: GPUTextureUsage.RENDER_ATTACHMENT | GPUTextureUsage.COPY_SRC,
			alphaMode: alphaMode
		} );

		this.updateSize();

	}

	get coordinateSystem() {

		return WebGPUCoordinateSystem;

	}

	async getArrayBufferAsync( attribute ) {

		return await this.attributeUtils.getArrayBufferAsync( attribute );

	}

	getContext() {

		return this.context;

	}

	_getDefaultRenderPassDescriptor() {

		let descriptor = this.defaultRenderPassdescriptor;

		if ( descriptor === null ) {

			const renderer = this.renderer;

			descriptor = {
				colorAttachments: [ {
					view: null
				} ],
				depthStencilAttachment: {
					view: this.textureUtils.getDepthBuffer( renderer.depth, renderer.stencil ).createView()
				}
			};

			const colorAttachment = descriptor.colorAttachments[ 0 ];

			if ( this.renderer.samples > 0 ) {

				colorAttachment.view = this.colorBuffer.createView();

			} else {

				colorAttachment.resolveTarget = undefined;

			}

			this.defaultRenderPassdescriptor = descriptor;

		}

		const colorAttachment = descriptor.colorAttachments[ 0 ];

		if ( this.renderer.samples > 0 ) {

			colorAttachment.resolveTarget = this.context.getCurrentTexture().createView();

		} else {

			colorAttachment.view = this.context.getCurrentTexture().createView();

		}

		return descriptor;

	}

	_getRenderPassDescriptor( renderContext ) {

		const renderTarget = renderContext.renderTarget;
		const renderTargetData = this.get( renderTarget );

		let descriptors = renderTargetData.descriptors;

		if ( descriptors === undefined ) {

			descriptors = [];

			renderTargetData.descriptors = descriptors;

		}

		if ( renderTargetData.width !== renderTarget.width ||
			renderTargetData.height !== renderTarget.height ||
			renderTargetData.activeMipmapLevel !== renderTarget.activeMipmapLevel ||
			renderTargetData.samples !== renderTarget.samples ||
			descriptors.length !== renderTarget.textures.length
		) {

			descriptors.length = 0;

			// dispose

			const onDispose = () => {

				renderTarget.removeEventListener( 'dispose', onDispose );

				this.delete( renderTarget );

			};

			renderTarget.addEventListener( 'dispose', onDispose );

		}

		let descriptor = descriptors[ renderContext.activeCubeFace ];

		if ( descriptor === undefined ) {

			const textures = renderContext.textures;
			const colorAttachments = [];

			for ( let i = 0; i < textures.length; i ++ ) {

				const textureData = this.get( textures[ i ] );

				const textureView = textureData.texture.createView( {
					baseMipLevel: renderContext.activeMipmapLevel,
					mipLevelCount: 1,
					baseArrayLayer: renderContext.activeCubeFace,
					dimension: GPUTextureViewDimension.TwoD
				} );

				let view, resolveTarget;

				if ( textureData.msaaTexture !== undefined ) {

					view = textureData.msaaTexture.createView();
					resolveTarget = textureView;

				} else {

					view = textureView;
					resolveTarget = undefined;

				}

				colorAttachments.push( {
					view,
					resolveTarget,
					loadOp: GPULoadOp.Load,
					storeOp: GPUStoreOp.Store
				} );

			}

			const depthTextureData = this.get( renderContext.depthTexture );

			const depthStencilAttachment = {
				view: depthTextureData.texture.createView()
			};

			descriptor = {
				colorAttachments,
				depthStencilAttachment
			};

			descriptors[ renderContext.activeCubeFace ] = descriptor;

			renderTargetData.width = renderTarget.width;
			renderTargetData.height = renderTarget.height;
			renderTargetData.samples = renderTarget.samples;
			renderTargetData.activeMipmapLevel = renderTarget.activeMipmapLevel;

		}

		return descriptor;

	}

	beginRender( renderContext ) {

		const renderContextData = this.get( renderContext );

		const device = this.device;
		const occlusionQueryCount = renderContext.occlusionQueryCount;

		let occlusionQuerySet;

		if ( occlusionQueryCount > 0 ) {

			if ( renderContextData.currentOcclusionQuerySet ) renderContextData.currentOcclusionQuerySet.destroy();
			if ( renderContextData.currentOcclusionQueryBuffer ) renderContextData.currentOcclusionQueryBuffer.destroy();

			// Get a reference to the array of objects with queries. The renderContextData property
			// can be changed by another render pass before the buffer.mapAsyc() completes.
			renderContextData.currentOcclusionQuerySet = renderContextData.occlusionQuerySet;
			renderContextData.currentOcclusionQueryBuffer = renderContextData.occlusionQueryBuffer;
			renderContextData.currentOcclusionQueryObjects = renderContextData.occlusionQueryObjects;

			//

			occlusionQuerySet = device.createQuerySet( { type: 'occlusion', count: occlusionQueryCount } );

			renderContextData.occlusionQuerySet = occlusionQuerySet;
			renderContextData.occlusionQueryIndex = 0;
			renderContextData.occlusionQueryObjects = new Array( occlusionQueryCount );

			renderContextData.lastOcclusionObject = null;

		}

		let descriptor;

		if ( renderContext.textures === null ) {

			descriptor = this._getDefaultRenderPassDescriptor();

		} else {

			descriptor = this._getRenderPassDescriptor( renderContext );

		}

		this.initTimestampQuery( renderContext, descriptor );

		descriptor.occlusionQuerySet = occlusionQuerySet;

		const depthStencilAttachment = descriptor.depthStencilAttachment;

		if ( renderContext.textures !== null ) {

			const colorAttachments = descriptor.colorAttachments;

			for ( let i = 0; i < colorAttachments.length; i ++ ) {

				const colorAttachment = colorAttachments[ i ];

				if ( renderContext.clearColor ) {

					colorAttachment.clearValue = renderContext.clearColorValue;
					colorAttachment.loadOp = GPULoadOp.Clear;
					colorAttachment.storeOp = GPUStoreOp.Store;

				} else {

					colorAttachment.loadOp = GPULoadOp.Load;
					colorAttachment.storeOp = GPUStoreOp.Store;

				}

			}

		} else {

			const colorAttachment = descriptor.colorAttachments[ 0 ];

			if ( renderContext.clearColor ) {

				colorAttachment.clearValue = renderContext.clearColorValue;
				colorAttachment.loadOp = GPULoadOp.Clear;
				colorAttachment.storeOp = GPUStoreOp.Store;

			} else {

				colorAttachment.loadOp = GPULoadOp.Load;
				colorAttachment.storeOp = GPUStoreOp.Store;

			}

		}

		//

		if ( renderContext.depth ) {

			if ( renderContext.clearDepth ) {

				depthStencilAttachment.depthClearValue = renderContext.clearDepthValue;
				depthStencilAttachment.depthLoadOp = GPULoadOp.Clear;
				depthStencilAttachment.depthStoreOp = GPUStoreOp.Store;

			} else {

				depthStencilAttachment.depthLoadOp = GPULoadOp.Load;
				depthStencilAttachment.depthStoreOp = GPUStoreOp.Store;

			}

		}

		if ( renderContext.stencil ) {

			if ( renderContext.clearStencil ) {

				depthStencilAttachment.stencilClearValue = renderContext.clearStencilValue;
				depthStencilAttachment.stencilLoadOp = GPULoadOp.Clear;
				depthStencilAttachment.stencilStoreOp = GPUStoreOp.Store;

			} else {

				depthStencilAttachment.stencilLoadOp = GPULoadOp.Load;
				depthStencilAttachment.stencilStoreOp = GPUStoreOp.Store;

			}

		}

		//

		const encoder = device.createCommandEncoder( { label: 'renderContext_' + renderContext.id } );
		const currentPass = encoder.beginRenderPass( descriptor );

		//

		renderContextData.descriptor = descriptor;
		renderContextData.encoder = encoder;
		renderContextData.currentPass = currentPass;
		renderContextData.currentSets = { attributes: {} };

		//

		if ( renderContext.viewport ) {

			this.updateViewport( renderContext );

		}

		if ( renderContext.scissor ) {

			const { x, y, width, height } = renderContext.scissorValue;

			currentPass.setScissorRect( x, renderContext.height - height - y, width, height );

		}

	}

	finishRender( renderContext ) {

		const renderContextData = this.get( renderContext );
		const occlusionQueryCount = renderContext.occlusionQueryCount;

		if ( renderContextData.renderBundles !== undefined && renderContextData.renderBundles.length > 0 ) {

			renderContextData.registerBundlesPhase = false;
			renderContextData.currentPass.executeBundles( renderContextData.renderBundles );

		}

		if ( occlusionQueryCount > renderContextData.occlusionQueryIndex ) {

			renderContextData.currentPass.endOcclusionQuery();

		}

		renderContextData.currentPass.end();

		if ( occlusionQueryCount > 0 ) {

			const bufferSize = occlusionQueryCount * 8; // 8 byte entries for query results

			//

			let queryResolveBuffer = this.occludedResolveCache.get( bufferSize );

			if ( queryResolveBuffer === undefined ) {

				queryResolveBuffer = this.device.createBuffer(
					{
						size: bufferSize,
						usage: GPUBufferUsage.QUERY_RESOLVE | GPUBufferUsage.COPY_SRC
					}
				);

				this.occludedResolveCache.set( bufferSize, queryResolveBuffer );

			}

			//

			const readBuffer = this.device.createBuffer(
				{
					size: bufferSize,
					usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.MAP_READ
				}
			);

			// two buffers required here - WebGPU doesn't allow usage of QUERY_RESOLVE & MAP_READ to be combined
			renderContextData.encoder.resolveQuerySet( renderContextData.occlusionQuerySet, 0, occlusionQueryCount, queryResolveBuffer, 0 );
			renderContextData.encoder.copyBufferToBuffer( queryResolveBuffer, 0, readBuffer, 0, bufferSize );

			renderContextData.occlusionQueryBuffer = readBuffer;

			//

			this.resolveOccludedAsync( renderContext );

		}

		this.prepareTimestampBuffer( renderContext, renderContextData.encoder );

		this.device.queue.submit( [ renderContextData.encoder.finish() ] );


		//

		if ( renderContext.textures !== null ) {

			const textures = renderContext.textures;

			for ( let i = 0; i < textures.length; i ++ ) {

				const texture = textures[ i ];

				if ( texture.generateMipmaps === true ) {

					this.textureUtils.generateMipmaps( texture );

				}

			}

		}

	}

	isOccluded( renderContext, object ) {

		const renderContextData = this.get( renderContext );

		return renderContextData.occluded && renderContextData.occluded.has( object );

	}

	async resolveOccludedAsync( renderContext ) {

		const renderContextData = this.get( renderContext );

		// handle occlusion query results

		const { currentOcclusionQueryBuffer, currentOcclusionQueryObjects } = renderContextData;

		if ( currentOcclusionQueryBuffer && currentOcclusionQueryObjects ) {

			const occluded = new WeakSet();

			renderContextData.currentOcclusionQueryObjects = null;
			renderContextData.currentOcclusionQueryBuffer = null;

			await currentOcclusionQueryBuffer.mapAsync( GPUMapMode.READ );

			const buffer = currentOcclusionQueryBuffer.getMappedRange();
			const results = new BigUint64Array( buffer );

			for ( let i = 0; i < currentOcclusionQueryObjects.length; i ++ ) {

				if ( results[ i ] !== BigInt( 0 ) ) {

					occluded.add( currentOcclusionQueryObjects[ i ] );

				}

			}

			currentOcclusionQueryBuffer.destroy();

			renderContextData.occluded = occluded;

		}

	}

	updateViewport( renderContext ) {

		const { currentPass } = this.get( renderContext );
		const { x, y, width, height, minDepth, maxDepth } = renderContext.viewportValue;

		currentPass.setViewport( x, renderContext.height - height - y, width, height, minDepth, maxDepth );

	}

	clear( color, depth, stencil, renderTargetData = null ) {

		const device = this.device;
		const renderer = this.renderer;

		let colorAttachments = [];

		let depthStencilAttachment;
		let clearValue;

		let supportsDepth;
		let supportsStencil;

		if ( color ) {

			const clearColor = this.getClearColor();

			clearValue = { r: clearColor.r, g: clearColor.g, b: clearColor.b, a: clearColor.a };

		}

		if ( renderTargetData === null ) {

			supportsDepth = renderer.depth;
			supportsStencil = renderer.stencil;

			const descriptor = this._getDefaultRenderPassDescriptor();

			if ( color ) {

				colorAttachments = descriptor.colorAttachments;

				const colorAttachment = colorAttachments[ 0 ];

				colorAttachment.clearValue = clearValue;
				colorAttachment.loadOp = GPULoadOp.Clear;
				colorAttachment.storeOp = GPUStoreOp.Store;

			}

			if ( supportsDepth || supportsStencil ) {

				depthStencilAttachment = descriptor.depthStencilAttachment;

			}

		} else {

			supportsDepth = renderTargetData.depth;
			supportsStencil = renderTargetData.stencil;

			if ( color ) {

				for ( const texture of renderTargetData.textures ) {

					const textureData = this.get( texture );
					const textureView = textureData.texture.createView();

					let view, resolveTarget;

					if ( textureData.msaaTexture !== undefined ) {

						view = textureData.msaaTexture.createView();
						resolveTarget = textureView;

					} else {

						view = textureView;
						resolveTarget = undefined;

					}

					colorAttachments.push( {
						view,
						resolveTarget,
						clearValue,
						loadOp: GPULoadOp.Clear,
						storeOp: GPUStoreOp.Store
					} );

				}

			}

			if ( supportsDepth || supportsStencil ) {

				const depthTextureData = this.get( renderTargetData.depthTexture );

				depthStencilAttachment = {
					view: depthTextureData.texture.createView()
				};

			}

		}

		//

		if ( supportsDepth ) {

			if ( depth ) {

				depthStencilAttachment.depthLoadOp = GPULoadOp.Clear;
				depthStencilAttachment.depthClearValue = renderer.getClearDepth();
				depthStencilAttachment.depthStoreOp = GPUStoreOp.Store;

			} else {

				depthStencilAttachment.depthLoadOp = GPULoadOp.Load;
				depthStencilAttachment.depthStoreOp = GPUStoreOp.Store;

			}

		}

		//

		if ( supportsStencil ) {

			if ( stencil ) {

				depthStencilAttachment.stencilLoadOp = GPULoadOp.Clear;
				depthStencilAttachment.stencilClearValue = renderer.getClearStencil();
				depthStencilAttachment.stencilStoreOp = GPUStoreOp.Store;

			} else {

				depthStencilAttachment.stencilLoadOp = GPULoadOp.Load;
				depthStencilAttachment.stencilStoreOp = GPUStoreOp.Store;

			}

		}

		//

		const encoder = device.createCommandEncoder( {} );
		const currentPass = encoder.beginRenderPass( {
			colorAttachments,
			depthStencilAttachment
		} );

		currentPass.end();

		device.queue.submit( [ encoder.finish() ] );

	}

	// compute

	beginCompute( computeGroup ) {

		const groupGPU = this.get( computeGroup );


		const descriptor = {};

		this.initTimestampQuery( computeGroup, descriptor );

		groupGPU.cmdEncoderGPU = this.device.createCommandEncoder();

		groupGPU.passEncoderGPU = groupGPU.cmdEncoderGPU.beginComputePass( descriptor );

	}

	compute( computeGroup, computeNode, bindings, pipeline ) {

		const { passEncoderGPU } = this.get( computeGroup );

		// pipeline

		const pipelineGPU = this.get( pipeline ).pipeline;
		passEncoderGPU.setPipeline( pipelineGPU );

		// bind groups

		for ( let i = 0, l = bindings.length; i < l; i ++ ) {

			const bindGroup = bindings[ i ];
			const bindingsData = this.get( bindGroup );

			passEncoderGPU.setBindGroup( i, bindingsData.group );

		}

		const maxComputeWorkgroupsPerDimension = this.device.limits.maxComputeWorkgroupsPerDimension;

		const computeNodeData = this.get( computeNode );

		if ( computeNodeData.dispatchSize === undefined ) computeNodeData.dispatchSize = { x: 0, y: 1, z: 1 };

		const { dispatchSize } = computeNodeData;

		if ( computeNode.dispatchCount > maxComputeWorkgroupsPerDimension ) {

			dispatchSize.x = Math.min( computeNode.dispatchCount, maxComputeWorkgroupsPerDimension );
			dispatchSize.y = Math.ceil( computeNode.dispatchCount / maxComputeWorkgroupsPerDimension );

		} else {

			dispatchSize.x = computeNode.dispatchCount;

		}

		passEncoderGPU.dispatchWorkgroups(
			dispatchSize.x,
			dispatchSize.y,
			dispatchSize.z
		);

	}

	finishCompute( computeGroup ) {

		const groupData = this.get( computeGroup );

		groupData.passEncoderGPU.end();

		this.prepareTimestampBuffer( computeGroup, groupData.cmdEncoderGPU );

		this.device.queue.submit( [ groupData.cmdEncoderGPU.finish() ] );

	}

	// render object

	draw( renderObject, info ) {

		const { object, geometry, context, pipeline } = renderObject;

		const bindings = renderObject.getBindings();
		const contextData = this.get( context );
		const pipelineGPU = this.get( pipeline ).pipeline;
		const currentSets = contextData.currentSets;

		const renderObjectData = this.get( renderObject );

		const { bundleEncoder, renderBundle, lastPipelineGPU } = renderObjectData;

		const renderContextData = this.get( context );

		if ( renderContextData.registerBundlesPhase === true && bundleEncoder !== undefined && lastPipelineGPU === pipelineGPU ) {

			renderContextData.renderBundles.push( renderBundle );
			return;

		}

		const passEncoderGPU = this.renderer._currentRenderBundle ? this.createBundleEncoder( context, renderObject ) : contextData.currentPass;

		// pipeline

		if ( currentSets.pipeline !== pipelineGPU ) {

			passEncoderGPU.setPipeline( pipelineGPU );

			currentSets.pipeline = pipelineGPU;

		}

		// bind groups

		for ( let i = 0, l = bindings.length; i < l; i ++ ) {

			const bindGroup = bindings[ i ];
			const bindingsData = this.get( bindGroup );

			passEncoderGPU.setBindGroup( i, bindingsData.group );

		}

		// attributes

		const index = renderObject.getIndex();

		const hasIndex = ( index !== null );

		// index

		if ( hasIndex === true ) {

			if ( currentSets.index !== index ) {

				const buffer = this.get( index ).buffer;
				const indexFormat = ( index.array instanceof Uint16Array ) ? GPUIndexFormat.Uint16 : GPUIndexFormat.Uint32;

				passEncoderGPU.setIndexBuffer( buffer, indexFormat );

				currentSets.index = index;

			}

		}

		// vertex buffers

		const vertexBuffers = renderObject.getVertexBuffers();

		for ( let i = 0, l = vertexBuffers.length; i < l; i ++ ) {

			const vertexBuffer = vertexBuffers[ i ];

			if ( currentSets.attributes[ i ] !== vertexBuffer ) {

				const buffer = this.get( vertexBuffer ).buffer;
				passEncoderGPU.setVertexBuffer( i, buffer );

				currentSets.attributes[ i ] = vertexBuffer;

			}

		}

		// occlusion queries - handle multiple consecutive draw calls for an object

		if ( contextData.occlusionQuerySet !== undefined ) {

			const lastObject = contextData.lastOcclusionObject;

			if ( lastObject !== object ) {

				if ( lastObject !== null && lastObject.occlusionTest === true ) {

					passEncoderGPU.endOcclusionQuery();
					contextData.occlusionQueryIndex ++;

				}

				if ( object.occlusionTest === true ) {

					passEncoderGPU.beginOcclusionQuery( contextData.occlusionQueryIndex );
					contextData.occlusionQueryObjects[ contextData.occlusionQueryIndex ] = object;

				}

				contextData.lastOcclusionObject = object;

			}

		}

		// draw

		const drawRange = renderObject.drawRange;
		const firstVertex = drawRange.start;

		const instanceCount = this.getInstanceCount( renderObject );
		if ( instanceCount === 0 ) return;

		if ( object.isBatchedMesh === true ) {

			const starts = object._multiDrawStarts;
			const counts = object._multiDrawCounts;
			const drawCount = object._multiDrawCount;
			const drawInstances = object._multiDrawInstances;

			const bytesPerElement = index.bytesPerElement || 1;

			for ( let i = 0; i < drawCount; i ++ ) {

				const count = drawInstances ? drawInstances[ i ] : 1;
				const firstInstance = count > 1 ? 0 : i;

				passEncoderGPU.drawIndexed( counts[ i ] / bytesPerElement, count, starts[ i ] / 4, 0, firstInstance );

			}

		} else if ( hasIndex === true ) {

			const indexCount = ( drawRange.count !== Infinity ) ? drawRange.count : index.count;

			passEncoderGPU.drawIndexed( indexCount, instanceCount, firstVertex, 0, 0 );

			info.update( object, indexCount, instanceCount );

		} else {

			const positionAttribute = geometry.attributes.position;
			const vertexCount = ( drawRange.count !== Infinity ) ? drawRange.count : positionAttribute.count;

			passEncoderGPU.draw( vertexCount, instanceCount, firstVertex, 0 );

			info.update( object, vertexCount, instanceCount );

		}

		if ( this.renderer._currentRenderBundle ) {

			const renderBundle = passEncoderGPU.finish();
			renderObjectData.lastPipelineGPU = pipelineGPU;
			renderObjectData.renderBundle = renderBundle;
			renderObjectData.bundleEncoder = passEncoderGPU;

		}

	}

	// cache key

	needsRenderUpdate( renderObject ) {

		const data = this.get( renderObject );

		const { object, material } = renderObject;

		const utils = this.utils;

		const sampleCount = utils.getSampleCountRenderContext( renderObject.context );
		const colorSpace = utils.getCurrentColorSpace( renderObject.context );
		const colorFormat = utils.getCurrentColorFormat( renderObject.context );
		const depthStencilFormat = utils.getCurrentDepthStencilFormat( renderObject.context );
		const primitiveTopology = utils.getPrimitiveTopology( object, material );

		let needsUpdate = false;

		if ( data.material !== material || data.materialVersion !== material.version ||
			data.transparent !== material.transparent || data.blending !== material.blending || data.premultipliedAlpha !== material.premultipliedAlpha ||
			data.blendSrc !== material.blendSrc || data.blendDst !== material.blendDst || data.blendEquation !== material.blendEquation ||
			data.blendSrcAlpha !== material.blendSrcAlpha || data.blendDstAlpha !== material.blendDstAlpha || data.blendEquationAlpha !== material.blendEquationAlpha ||
			data.colorWrite !== material.colorWrite || data.depthWrite !== material.depthWrite || data.depthTest !== material.depthTest || data.depthFunc !== material.depthFunc ||
			data.stencilWrite !== material.stencilWrite || data.stencilFunc !== material.stencilFunc ||
			data.stencilFail !== material.stencilFail || data.stencilZFail !== material.stencilZFail || data.stencilZPass !== material.stencilZPass ||
			data.stencilFuncMask !== material.stencilFuncMask || data.stencilWriteMask !== material.stencilWriteMask ||
			data.side !== material.side || data.alphaToCoverage !== material.alphaToCoverage ||
			data.sampleCount !== sampleCount || data.colorSpace !== colorSpace ||
			data.colorFormat !== colorFormat || data.depthStencilFormat !== depthStencilFormat ||
			data.primitiveTopology !== primitiveTopology ||
			data.clippingContextVersion !== renderObject.clippingContextVersion
		) {

			data.material = material; data.materialVersion = material.version;
			data.transparent = material.transparent; data.blending = material.blending; data.premultipliedAlpha = material.premultipliedAlpha;
			data.blendSrc = material.blendSrc; data.blendDst = material.blendDst; data.blendEquation = material.blendEquation;
			data.blendSrcAlpha = material.blendSrcAlpha; data.blendDstAlpha = material.blendDstAlpha; data.blendEquationAlpha = material.blendEquationAlpha;
			data.colorWrite = material.colorWrite;
			data.depthWrite = material.depthWrite; data.depthTest = material.depthTest; data.depthFunc = material.depthFunc;
			data.stencilWrite = material.stencilWrite; data.stencilFunc = material.stencilFunc;
			data.stencilFail = material.stencilFail; data.stencilZFail = material.stencilZFail; data.stencilZPass = material.stencilZPass;
			data.stencilFuncMask = material.stencilFuncMask; data.stencilWriteMask = material.stencilWriteMask;
			data.side = material.side; data.alphaToCoverage = material.alphaToCoverage;
			data.sampleCount = sampleCount;
			data.colorSpace = colorSpace;
			data.colorFormat = colorFormat;
			data.depthStencilFormat = depthStencilFormat;
			data.primitiveTopology = primitiveTopology;
			data.clippingContextVersion = renderObject.clippingContextVersion;

			needsUpdate = true;

		}

		return needsUpdate;

	}

	getRenderCacheKey( renderObject ) {

		const { object, material } = renderObject;

		const utils = this.utils;
		const renderContext = renderObject.context;

		return [
			material.transparent, material.blending, material.premultipliedAlpha,
			material.blendSrc, material.blendDst, material.blendEquation,
			material.blendSrcAlpha, material.blendDstAlpha, material.blendEquationAlpha,
			material.colorWrite,
			material.depthWrite, material.depthTest, material.depthFunc,
			material.stencilWrite, material.stencilFunc,
			material.stencilFail, material.stencilZFail, material.stencilZPass,
			material.stencilFuncMask, material.stencilWriteMask,
			material.side,
			utils.getSampleCountRenderContext( renderContext ),
			utils.getCurrentColorSpace( renderContext ), utils.getCurrentColorFormat( renderContext ), utils.getCurrentDepthStencilFormat( renderContext ),
			utils.getPrimitiveTopology( object, material ),
			renderObject.clippingContextVersion
		].join();

	}

	// textures

	createSampler( texture ) {

		this.textureUtils.createSampler( texture );

	}

	destroySampler( texture ) {

		this.textureUtils.destroySampler( texture );

	}

	createDefaultTexture( texture ) {

		this.textureUtils.createDefaultTexture( texture );

	}

	createTexture( texture, options ) {

		this.textureUtils.createTexture( texture, options );

	}

	updateTexture( texture, options ) {

		this.textureUtils.updateTexture( texture, options );

	}

	generateMipmaps( texture ) {

		this.textureUtils.generateMipmaps( texture );

	}

	destroyTexture( texture ) {

		this.textureUtils.destroyTexture( texture );

	}

	copyTextureToBuffer( texture, x, y, width, height ) {

		return this.textureUtils.copyTextureToBuffer( texture, x, y, width, height );

	}


	initTimestampQuery( renderContext, descriptor ) {

		if ( ! this.hasFeature( GPUFeatureName.TimestampQuery ) || ! this.trackTimestamp ) return;

		const renderContextData = this.get( renderContext );

		if ( ! renderContextData.timeStampQuerySet ) {

			// Create a GPUQuerySet which holds 2 timestamp query results: one for the
			// beginning and one for the end of compute pass execution.
			const timeStampQuerySet = this.device.createQuerySet( { type: 'timestamp', count: 2 } );

			const timestampWrites = {
				querySet: timeStampQuerySet,
				beginningOfPassWriteIndex: 0, // Write timestamp in index 0 when pass begins.
				endOfPassWriteIndex: 1, // Write timestamp in index 1 when pass ends.
			};

			Object.assign( descriptor, {
				timestampWrites,
			} );

			renderContextData.timeStampQuerySet = timeStampQuerySet;

		}

	}

	// timestamp utils

	prepareTimestampBuffer( renderContext, encoder ) {

		if ( ! this.hasFeature( GPUFeatureName.TimestampQuery ) || ! this.trackTimestamp ) return;

		const renderContextData = this.get( renderContext );

		const size = 2 * BigInt64Array.BYTES_PER_ELEMENT;

		if ( renderContextData.currentTimestampQueryBuffers === undefined ) {

			renderContextData.currentTimestampQueryBuffers = {
				resolveBuffer: this.device.createBuffer( {
					label: 'timestamp resolve buffer',
					size: size,
					usage: GPUBufferUsage.QUERY_RESOLVE | GPUBufferUsage.COPY_SRC,
				} ),
				resultBuffer: this.device.createBuffer( {
					label: 'timestamp result buffer',
					size: size,
					usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.MAP_READ,
				} ),
				isMappingPending: false,
			};

		}

		const { resolveBuffer, resultBuffer, isMappingPending } = renderContextData.currentTimestampQueryBuffers;

		if ( isMappingPending === true ) return;

		encoder.resolveQuerySet( renderContextData.timeStampQuerySet, 0, 2, resolveBuffer, 0 );
		encoder.copyBufferToBuffer( resolveBuffer, 0, resultBuffer, 0, size );

	}

	async resolveTimestampAsync( renderContext, type = 'render' ) {

		if ( ! this.hasFeature( GPUFeatureName.TimestampQuery ) || ! this.trackTimestamp ) return;

		const renderContextData = this.get( renderContext );

		if ( renderContextData.currentTimestampQueryBuffers === undefined ) return;

		const { resultBuffer, isMappingPending } = renderContextData.currentTimestampQueryBuffers;

		if ( isMappingPending === true ) return;

		renderContextData.currentTimestampQueryBuffers.isMappingPending = true;

		resultBuffer.mapAsync( GPUMapMode.READ ).then( () => {

			const times = new BigUint64Array( resultBuffer.getMappedRange() );
			const duration = Number( times[ 1 ] - times[ 0 ] ) / 1000000;


			this.renderer.info.updateTimestamp( type, duration );

			resultBuffer.unmap();

			renderContextData.currentTimestampQueryBuffers.isMappingPending = false;

		} );

	}

	// node builder

	createNodeBuilder( object, renderer ) {

		return new WGSLNodeBuilder( object, renderer );

	}

	// program

	createProgram( program ) {

		const programGPU = this.get( program );

		programGPU.module = {
			module: this.device.createShaderModule( { code: program.code, label: program.stage } ),
			entryPoint: 'main'
		};

	}

	destroyProgram( program ) {

		this.delete( program );

	}

	// pipelines

	createRenderPipeline( renderObject, promises ) {

		this.pipelineUtils.createRenderPipeline( renderObject, promises );

	}

	createComputePipeline( computePipeline, bindings ) {

		this.pipelineUtils.createComputePipeline( computePipeline, bindings );

	}

	createBundleEncoder( renderContext, renderObject ) {

		return this.pipelineUtils.createBundleEncoder( renderContext, renderObject );

	}

	// bindings

	createBindings( bindGroup ) {

		this.bindingUtils.createBindings( bindGroup );

	}

	updateBindings( bindGroup ) {

		this.bindingUtils.createBindings( bindGroup );

	}

	updateBinding( binding ) {

		this.bindingUtils.updateBinding( binding );

	}

	// attributes

	createIndexAttribute( attribute ) {

		this.attributeUtils.createAttribute( attribute, GPUBufferUsage.INDEX | GPUBufferUsage.COPY_SRC | GPUBufferUsage.COPY_DST );

	}

	createAttribute( attribute ) {

		this.attributeUtils.createAttribute( attribute, GPUBufferUsage.VERTEX | GPUBufferUsage.COPY_SRC | GPUBufferUsage.COPY_DST );

	}

	createStorageAttribute( attribute ) {

		this.attributeUtils.createAttribute( attribute, GPUBufferUsage.STORAGE | GPUBufferUsage.VERTEX | GPUBufferUsage.COPY_SRC | GPUBufferUsage.COPY_DST );

	}

	updateAttribute( attribute ) {

		this.attributeUtils.updateAttribute( attribute );

	}

	destroyAttribute( attribute ) {

		this.attributeUtils.destroyAttribute( attribute );

	}

	// canvas

	updateSize() {

		this.colorBuffer = this.textureUtils.getColorBuffer();
		this.defaultRenderPassdescriptor = null;

	}

	// utils public

	getMaxAnisotropy() {

		return 16;

	}

	hasFeature( name ) {

		return this.device.features.has( name );

	}

	copyTextureToTexture( srcTexture, dstTexture, srcRegion = null, dstPosition = null, level = 0 ) {

		let dstX = 0;
		let dstY = 0;

		let srcX = 0;
		let srcY = 0;

		let srcWidth = srcTexture.image.width;
		let srcHeight = srcTexture.image.height;

		if ( srcRegion !== null ) {

			srcX = srcRegion.x;
			srcY = srcRegion.y;
			srcWidth = srcRegion.width;
			srcHeight = srcRegion.height;

		}

		if ( dstPosition !== null ) {

			dstX = dstPosition.x;
			dstY = dstPosition.y;

		}

		const encoder = this.device.createCommandEncoder( { label: 'copyTextureToTexture_' + srcTexture.id + '_' + dstTexture.id } );

		const sourceGPU = this.get( srcTexture ).texture;
		const destinationGPU = this.get( dstTexture ).texture;

		encoder.copyTextureToTexture(
			{
				texture: sourceGPU,
				mipLevel: level,
				origin: { x: srcX, y: srcY, z: 0 }
			},
			{
				texture: destinationGPU,
				mipLevel: level,
				origin: { x: dstX, y: dstY, z: 0 }
			},
			[
				srcWidth,
				srcHeight
			]
		);

		this.device.queue.submit( [ encoder.finish() ] );

	}

	copyFramebufferToTexture( texture, renderContext ) {

		const renderContextData = this.get( renderContext );

		const { encoder, descriptor } = renderContextData;

		let sourceGPU = null;

		if ( renderContext.renderTarget ) {

			if ( texture.isDepthTexture ) {

				sourceGPU = this.get( renderContext.depthTexture ).texture;

			} else {

				sourceGPU = this.get( renderContext.textures[ 0 ] ).texture;

			}

		} else {

			if ( texture.isDepthTexture ) {

				sourceGPU = this.textureUtils.getDepthBuffer( renderContext.depth, renderContext.stencil );

			} else {

				sourceGPU = this.context.getCurrentTexture();

			}

		}

		const destinationGPU = this.get( texture ).texture;

		if ( sourceGPU.format !== destinationGPU.format ) {

			console.error( 'WebGPUBackend: copyFramebufferToTexture: Source and destination formats do not match.', sourceGPU.format, destinationGPU.format );

			return;

		}

		renderContextData.currentPass.end();

		encoder.copyTextureToTexture(
			{
				texture: sourceGPU,
				origin: { x: 0, y: 0, z: 0 }
			},
			{
				texture: destinationGPU
			},
			[
				texture.image.width,
				texture.image.height
			]
		);

		if ( texture.generateMipmaps ) this.textureUtils.generateMipmaps( texture );

		for ( let i = 0; i < descriptor.colorAttachments.length; i ++ ) {

			descriptor.colorAttachments[ i ].loadOp = GPULoadOp.Load;

		}

		if ( renderContext.depth ) descriptor.depthStencilAttachment.depthLoadOp = GPULoadOp.Load;
		if ( renderContext.stencil ) descriptor.depthStencilAttachment.stencilLoadOp = GPULoadOp.Load;

		renderContextData.currentPass = encoder.beginRenderPass( descriptor );
		renderContextData.currentSets = { attributes: {} };

	}

}

export default WebGPUBackend;
