import {
	GPUTextureAspect, GPUTextureViewDimension, GPUTextureSampleType, GPUBufferBindingType, GPUStorageTextureAccess,
	GPUSamplerBindingType
} from './WebGPUConstants.js';

import { FloatType, IntType, UnsignedIntType } from '../../../constants.js';
import { NodeAccess } from '../../../nodes/core/constants.js';

/**
 * A WebGPU backend utility module for managing bindings.
 *
 * When reading the documentation it's helpful to keep in mind that
 * all class definitions starting with 'GPU*' are modules from the
 * WebGPU API. So for example `BindGroup` is a class from the engine
 * whereas `GPUBindGroup` is a class from WebGPU.
 *
 * @private
 */
class WebGPUBindingUtils {

	/**
	 * Constructs a new utility object.
	 *
	 * @param {WebGPUBackend} backend - The WebGPU backend.
	 */
	constructor( backend ) {

		/**
		 * A reference to the WebGPU backend.
		 *
		 * @type {WebGPUBackend}
		 */
		this.backend = backend;

		/**
		 * A cache for managing bind group layouts.
		 *
		 * @type {WeakMap<Array<Binding>,GPUBindGroupLayout>}
		 */
		this.bindGroupLayoutCache = new WeakMap();

	}

	/**
	 * Creates a GPU bind group layout for the given bind group.
	 *
	 * @param {BindGroup} bindGroup - The bind group.
	 * @return {GPUBindGroupLayout} The GPU bind group layout.
	 */
	createBindingsLayout( bindGroup ) {

		const backend = this.backend;
		const device = backend.device;

		const entries = [];

		let index = 0;

		for ( const binding of bindGroup.bindings ) {

			const bindingGPU = {
				binding: index ++,
				visibility: binding.visibility
			};

			if ( binding.isUniformBuffer || binding.isStorageBuffer ) {

				const buffer = {}; // GPUBufferBindingLayout

				if ( binding.isStorageBuffer ) {

					if ( binding.visibility & 4 ) {

						// compute

						if ( binding.access === NodeAccess.READ_WRITE || binding.access === NodeAccess.WRITE_ONLY ) {

							buffer.type = GPUBufferBindingType.Storage;

						} else {

							buffer.type = GPUBufferBindingType.ReadOnlyStorage;

						}

					} else {

						buffer.type = GPUBufferBindingType.ReadOnlyStorage;

					}

				}

				bindingGPU.buffer = buffer;

			} else if ( binding.isSampler ) {

				const sampler = {}; // GPUSamplerBindingLayout

				if ( binding.texture.isDepthTexture ) {

					if ( binding.texture.compareFunction !== null ) {

						sampler.type = GPUSamplerBindingType.Comparison;

					} else if ( backend.compatibilityMode ) {

						sampler.type = GPUSamplerBindingType.NonFiltering;

					}

				}

				bindingGPU.sampler = sampler;

			} else if ( binding.isSampledTexture && binding.texture.isVideoTexture ) {

				bindingGPU.externalTexture = {}; // GPUExternalTextureBindingLayout

			} else if ( binding.isSampledTexture && binding.store ) {

				const storageTexture = {}; // GPUStorageTextureBindingLayout
				storageTexture.format = this.backend.get( binding.texture ).texture.format;

				const access = binding.access;

				if ( access === NodeAccess.READ_WRITE ) {

					storageTexture.access = GPUStorageTextureAccess.ReadWrite;

				} else if ( access === NodeAccess.WRITE_ONLY ) {

					storageTexture.access = GPUStorageTextureAccess.WriteOnly;

				} else {

					storageTexture.access = GPUStorageTextureAccess.ReadOnly;

				}

				if ( binding.texture.isArrayTexture ) {

					storageTexture.viewDimension = GPUTextureViewDimension.TwoDArray;

				} else if ( binding.texture.is3DTexture ) {

					storageTexture.viewDimension = GPUTextureViewDimension.ThreeD;

				}

				bindingGPU.storageTexture = storageTexture;

			} else if ( binding.isSampledTexture ) {

				const texture = {}; // GPUTextureBindingLayout

				const { primarySamples } = backend.utils.getTextureSampleData( binding.texture );

				if ( primarySamples > 1 ) {

					texture.multisampled = true;

					if ( ! binding.texture.isDepthTexture ) {

						texture.sampleType = GPUTextureSampleType.UnfilterableFloat;

					}

				}

				if ( binding.texture.isDepthTexture ) {

					if ( backend.compatibilityMode && binding.texture.compareFunction === null ) {

						texture.sampleType = GPUTextureSampleType.UnfilterableFloat;

					} else {

						texture.sampleType = GPUTextureSampleType.Depth;

					}

				} else if ( binding.texture.isDataTexture || binding.texture.isDataArrayTexture || binding.texture.isData3DTexture ) {

					const type = binding.texture.type;

					if ( type === IntType ) {

						texture.sampleType = GPUTextureSampleType.SInt;

					} else if ( type === UnsignedIntType ) {

						texture.sampleType = GPUTextureSampleType.UInt;

					} else if ( type === FloatType ) {

						if ( this.backend.hasFeature( 'float32-filterable' ) ) {

							texture.sampleType = GPUTextureSampleType.Float;

						} else {

							texture.sampleType = GPUTextureSampleType.UnfilterableFloat;

						}

					}

				}

				if ( binding.isSampledCubeTexture ) {

					texture.viewDimension = GPUTextureViewDimension.Cube;

				} else if ( binding.texture.isArrayTexture || binding.texture.isDataArrayTexture || binding.texture.isCompressedArrayTexture ) {

					texture.viewDimension = GPUTextureViewDimension.TwoDArray;

				} else if ( binding.isSampledTexture3D ) {

					texture.viewDimension = GPUTextureViewDimension.ThreeD;

				}

				bindingGPU.texture = texture;

			} else {

				console.error( `WebGPUBindingUtils: Unsupported binding "${ binding }".` );

			}

			entries.push( bindingGPU );

		}

		return device.createBindGroupLayout( { entries } );

	}

	/**
	 * Creates bindings from the given bind group definition.
	 *
	 * @param {BindGroup} bindGroup - The bind group.
	 * @param {Array<BindGroup>} bindings - Array of bind groups.
	 * @param {number} cacheIndex - The cache index.
	 * @param {number} version - The version.
	 */
	createBindings( bindGroup, bindings, cacheIndex, version = 0 ) {

		const { backend, bindGroupLayoutCache } = this;
		const bindingsData = backend.get( bindGroup );

		// setup (static) binding layout and (dynamic) binding group

		let bindLayoutGPU = bindGroupLayoutCache.get( bindGroup.bindingsReference );

		if ( bindLayoutGPU === undefined ) {

			bindLayoutGPU = this.createBindingsLayout( bindGroup );
			bindGroupLayoutCache.set( bindGroup.bindingsReference, bindLayoutGPU );

		}

		let bindGroupGPU;

		if ( cacheIndex > 0 ) {

			if ( bindingsData.groups === undefined ) {

				bindingsData.groups = [];
				bindingsData.versions = [];

			}

			if ( bindingsData.versions[ cacheIndex ] === version ) {

				bindGroupGPU = bindingsData.groups[ cacheIndex ];

			}

		}

		if ( bindGroupGPU === undefined ) {

			bindGroupGPU = this.createBindGroup( bindGroup, bindLayoutGPU );

			if ( cacheIndex > 0 ) {

				bindingsData.groups[ cacheIndex ] = bindGroupGPU;
				bindingsData.versions[ cacheIndex ] = version;

			}

		}

		bindingsData.group = bindGroupGPU;
		bindingsData.layout = bindLayoutGPU;

	}

	/**
	 * Updates a buffer binding.
	 *
	 *  @param {Buffer} binding - The buffer binding to update.
	 */
	updateBinding( binding ) {

		const backend = this.backend;
		const device = backend.device;

		const buffer = binding.buffer;
		const bufferGPU = backend.get( binding ).buffer;

		device.queue.writeBuffer( bufferGPU, 0, buffer, 0 );

	}

	/**
	 * Creates a GPU bind group for the camera index.
	 *
	 * @param {Uint32Array} data - The index data.
	 * @param {GPUBindGroupLayout} layout - The GPU bind group layout.
	 * @return {GPUBindGroup} The GPU bind group.
	 */
	createBindGroupIndex( data, layout ) {

		const backend = this.backend;
		const device = backend.device;

		const usage = GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST;
		const index = data[ 0 ];

		const buffer = device.createBuffer( {
			label: 'bindingCameraIndex_' + index,
			size: 16, // uint(4) * 4
			usage: usage
		} );

		device.queue.writeBuffer( buffer, 0, data, 0 );

		const entries = [ { binding: 0, resource: { buffer } } ];

		return device.createBindGroup( {
			label: 'bindGroupCameraIndex_' + index,
			layout,
			entries
		} );

	}

	/**
	 * Creates a GPU bind group for the given bind group and GPU layout.
	 *
	 * @param {BindGroup} bindGroup - The bind group.
	 * @param {GPUBindGroupLayout} layoutGPU - The GPU bind group layout.
	 * @return {GPUBindGroup} The GPU bind group.
	 */
	createBindGroup( bindGroup, layoutGPU ) {

		const backend = this.backend;
		const device = backend.device;

		let bindingPoint = 0;
		const entriesGPU = [];

		for ( const binding of bindGroup.bindings ) {

			if ( binding.isUniformBuffer ) {

				const bindingData = backend.get( binding );

				if ( bindingData.buffer === undefined ) {

					const byteLength = binding.byteLength;

					const usage = GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST;

					const bufferGPU = device.createBuffer( {
						label: 'bindingBuffer_' + binding.name,
						size: byteLength,
						usage: usage
					} );

					bindingData.buffer = bufferGPU;

				}

				entriesGPU.push( { binding: bindingPoint, resource: { buffer: bindingData.buffer } } );

			} else if ( binding.isStorageBuffer ) {

				const bindingData = backend.get( binding );

				if ( bindingData.buffer === undefined ) {

					const attribute = binding.attribute;
					//const usage = GPUBufferUsage.STORAGE | GPUBufferUsage.VERTEX | /*GPUBufferUsage.COPY_SRC |*/ GPUBufferUsage.COPY_DST;

					//backend.attributeUtils.createAttribute( attribute, usage ); // @TODO: Move it to universal renderer

					bindingData.buffer = backend.get( attribute ).buffer;

				}

				entriesGPU.push( { binding: bindingPoint, resource: { buffer: bindingData.buffer } } );

			} else if ( binding.isSampler ) {

				const textureGPU = backend.get( binding.texture );

				entriesGPU.push( { binding: bindingPoint, resource: textureGPU.sampler } );

			} else if ( binding.isSampledTexture ) {

				const textureData = backend.get( binding.texture );

				let resourceGPU;

				if ( textureData.externalTexture !== undefined ) {

					resourceGPU = device.importExternalTexture( { source: textureData.externalTexture } );

				} else {

					const mipLevelCount = binding.store ? 1 : textureData.texture.mipLevelCount;
					const propertyName = `view-${ textureData.texture.width }-${ textureData.texture.height }-${ mipLevelCount }`;

					resourceGPU = textureData[ propertyName ];

					if ( resourceGPU === undefined ) {

						const aspectGPU = GPUTextureAspect.All;

						let dimensionViewGPU;

						if ( binding.isSampledCubeTexture ) {

							dimensionViewGPU = GPUTextureViewDimension.Cube;

						} else if ( binding.isSampledTexture3D ) {

							dimensionViewGPU = GPUTextureViewDimension.ThreeD;

						} else if ( binding.texture.isArrayTexture || binding.texture.isDataArrayTexture || binding.texture.isCompressedArrayTexture ) {

							dimensionViewGPU = GPUTextureViewDimension.TwoDArray;

						} else {

							dimensionViewGPU = GPUTextureViewDimension.TwoD;

						}

						resourceGPU = textureData[ propertyName ] = textureData.texture.createView( { aspect: aspectGPU, dimension: dimensionViewGPU, mipLevelCount } );

					}

				}

				entriesGPU.push( { binding: bindingPoint, resource: resourceGPU } );

			}

			bindingPoint ++;

		}

		return device.createBindGroup( {
			label: 'bindGroup_' + bindGroup.name,
			layout: layoutGPU,
			entries: entriesGPU
		} );

	}

}

export default WebGPUBindingUtils;
