import UniformBuffer from './UniformBuffer.js';
import { GPU_CHUNK_BYTES } from './Constants.js';

class UniformsGroup extends UniformBuffer {

	constructor( name ) {

		super( name );

		this.isUniformsGroup = true;

		// the order of uniforms in this array must match the order of uniforms in the shader

		this.uniforms = [];

	}

	addUniform( uniform ) {

		this.uniforms.push( uniform );

		return this;

	}

	removeUniform( uniform ) {

		const index = this.uniforms.indexOf( uniform );

		if ( index !== - 1 ) {

			this.uniforms.splice( index, 1 );

		}

		return this;

	}

	get buffer() {

		let buffer = this._buffer;

		if ( buffer === null ) {

			const byteLength = this.byteLength;

			buffer = new Float32Array( new ArrayBuffer( byteLength ) );

			this._buffer = buffer;

		}

		return buffer;

	}

	get byteLength() {

		let offset = 0; // global buffer offset in bytes

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

			const uniform = this.uniforms[ i ];

			const { boundary, itemSize } = uniform;

			// offset within a single chunk in bytes

			const chunkOffset = offset % GPU_CHUNK_BYTES;
			const remainingSizeInChunk = GPU_CHUNK_BYTES - chunkOffset;

			// conformance tests

			if ( chunkOffset !== 0 && ( remainingSizeInChunk - boundary ) < 0 ) {

				// check for chunk overflow

				offset += ( GPU_CHUNK_BYTES - chunkOffset );

			} else if ( chunkOffset % boundary !== 0 ) {

				// check for correct alignment

				offset += ( chunkOffset % boundary );

			}

			uniform.offset = ( offset / this.bytesPerElement );

			offset += ( itemSize * this.bytesPerElement );

		}

		return Math.ceil( offset / GPU_CHUNK_BYTES ) * GPU_CHUNK_BYTES;

	}

	update() {

		let updated = false;

		for ( const uniform of this.uniforms ) {

			if ( this.updateByType( uniform ) === true ) {

				updated = true;

			}

		}

		return updated;

	}

	updateByType( uniform ) {

		if ( uniform.isFloatUniform ) return this.updateNumber( uniform );
		if ( uniform.isVector2Uniform ) return this.updateVector2( uniform );
		if ( uniform.isVector3Uniform ) return this.updateVector3( uniform );
		if ( uniform.isVector4Uniform ) return this.updateVector4( uniform );
		if ( uniform.isColorUniform ) return this.updateColor( uniform );
		if ( uniform.isMatrix3Uniform ) return this.updateMatrix3( uniform );
		if ( uniform.isMatrix4Uniform ) return this.updateMatrix4( uniform );

		console.error( 'THREE.WebGPUUniformsGroup: Unsupported uniform type.', uniform );

	}

	updateNumber( uniform ) {

		let updated = false;

		const a = this.buffer;
		const v = uniform.getValue();
		const offset = uniform.offset;

		if ( a[ offset ] !== v ) {

			a[ offset ] = v;
			updated = true;

		}

		return updated;

	}

	updateVector2( uniform ) {

		let updated = false;

		const a = this.buffer;
		const v = uniform.getValue();
		const offset = uniform.offset;

		if ( a[ offset + 0 ] !== v.x || a[ offset + 1 ] !== v.y ) {

			a[ offset + 0 ] = v.x;
			a[ offset + 1 ] = v.y;

			updated = true;

		}

		return updated;

	}

	updateVector3( uniform ) {

		let updated = false;

		const a = this.buffer;
		const v = uniform.getValue();
		const offset = uniform.offset;

		if ( a[ offset + 0 ] !== v.x || a[ offset + 1 ] !== v.y || a[ offset + 2 ] !== v.z ) {

			a[ offset + 0 ] = v.x;
			a[ offset + 1 ] = v.y;
			a[ offset + 2 ] = v.z;

			updated = true;

		}

		return updated;

	}

	updateVector4( uniform ) {

		let updated = false;

		const a = this.buffer;
		const v = uniform.getValue();
		const offset = uniform.offset;

		if ( a[ offset + 0 ] !== v.x || a[ offset + 1 ] !== v.y || a[ offset + 2 ] !== v.z || a[ offset + 4 ] !== v.w ) {

			a[ offset + 0 ] = v.x;
			a[ offset + 1 ] = v.y;
			a[ offset + 2 ] = v.z;
			a[ offset + 3 ] = v.w;

			updated = true;

		}

		return updated;

	}

	updateColor( uniform ) {

		let updated = false;

		const a = this.buffer;
		const c = uniform.getValue();
		const offset = uniform.offset;

		if ( a[ offset + 0 ] !== c.r || a[ offset + 1 ] !== c.g || a[ offset + 2 ] !== c.b ) {

			a[ offset + 0 ] = c.r;
			a[ offset + 1 ] = c.g;
			a[ offset + 2 ] = c.b;

			updated = true;

		}

		return updated;

	}

	updateMatrix3( uniform ) {

		let updated = false;

		const a = this.buffer;
		const e = uniform.getValue().elements;
		const offset = uniform.offset;

		if ( a[ offset + 0 ] !== e[ 0 ] || a[ offset + 1 ] !== e[ 1 ] || a[ offset + 2 ] !== e[ 2 ] ||
			a[ offset + 4 ] !== e[ 3 ] || a[ offset + 5 ] !== e[ 4 ] || a[ offset + 6 ] !== e[ 5 ] ||
			a[ offset + 8 ] !== e[ 6 ] || a[ offset + 9 ] !== e[ 7 ] || a[ offset + 10 ] !== e[ 8 ] ) {

			a[ offset + 0 ] = e[ 0 ];
			a[ offset + 1 ] = e[ 1 ];
			a[ offset + 2 ] = e[ 2 ];
			a[ offset + 4 ] = e[ 3 ];
			a[ offset + 5 ] = e[ 4 ];
			a[ offset + 6 ] = e[ 5 ];
			a[ offset + 8 ] = e[ 6 ];
			a[ offset + 9 ] = e[ 7 ];
			a[ offset + 10 ] = e[ 8 ];

			updated = true;

		}

		return updated;

	}

	updateMatrix4( uniform ) {

		let updated = false;

		const a = this.buffer;
		const e = uniform.getValue().elements;
		const offset = uniform.offset;

		if ( arraysEqual( a, e, offset ) === false ) {

			a.set( e, offset );
			updated = true;

		}

		return updated;

	}

}

function arraysEqual( a, b, offset ) {

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

		if ( a[ offset + i ] !== b[ i ] ) return false;

	}

	return true;

}

export default UniformsGroup;
