import {
  CubeTexture,
  DataTexture,
  DefaultLoadingManager,
  FileLoader,
  FloatType,
  HalfFloatType,
  LinearEncoding,
  LinearFilter,
  NearestFilter,
  RGBAFormat,
  RGBEEncoding,
  RGBFormat,
  UnsignedByteType
} from 'three';
import RGBELoader from './RGBELoader';

/**
* @author Prashant Sharma / spidersharma03
* @author Ben Houston / http://clara.io / bhouston
*/

const HDRCubeTextureLoader = function ( manager ) {

	this.manager = ( manager !== undefined ) ? manager : DefaultLoadingManager;
	// override in sub classes
	this.hdrLoader = new RGBELoader();

};

HDRCubeTextureLoader.prototype.load = function ( type, urls, onLoad, onProgress, onError ) {

	var RGBEByteToRGBFloat = function ( sourceArray, sourceOffset, destArray, destOffset ) {

		var e = sourceArray[ sourceOffset + 3 ];
		var scale = Math.pow( 2.0, e - 128.0 ) / 255.0;

		destArray[ destOffset + 0 ] = sourceArray[ sourceOffset + 0 ] * scale;
		destArray[ destOffset + 1 ] = sourceArray[ sourceOffset + 1 ] * scale;
		destArray[ destOffset + 2 ] = sourceArray[ sourceOffset + 2 ] * scale;

	};

	var RGBEByteToRGBHalf = ( function () {

		// Source: http://gamedev.stackexchange.com/questions/17326/conversion-of-a-number-from-single-precision-floating-point-representation-to-a/17410#17410

		var floatView = new Float32Array( 1 );
		var int32View = new Int32Array( floatView.buffer );

		/* This method is faster than the OpenEXR implementation (very often
		 * used, eg. in Ogre), with the additional benefit of rounding, inspired
		 * by James Tursa?s half-precision code. */
		function toHalf( val ) {

			floatView[ 0 ] = val;
			var x = int32View[ 0 ];

			var bits = ( x >> 16 ) & 0x8000; /* Get the sign */
			var m = ( x >> 12 ) & 0x07ff; /* Keep one extra bit for rounding */
			var e = ( x >> 23 ) & 0xff; /* Using int is faster here */

			/* If zero, or denormal, or exponent underflows too much for a denormal
			 * half, return signed zero. */
			if ( e < 103 ) return bits;

			/* If NaN, return NaN. If Inf or exponent overflow, return Inf. */
			if ( e > 142 ) {

				bits |= 0x7c00;
				/* If exponent was 0xff and one mantissa bit was set, it means NaN,
						 * not Inf, so make sure we set one mantissa bit too. */
				bits |= ( ( e == 255 ) ? 0 : 1 ) && ( x & 0x007fffff );
				return bits;

			}

			/* If exponent underflows but not too much, return a denormal */
			if ( e < 113 ) {

				m |= 0x0800;
				/* Extra rounding may overflow and set mantissa to 0 and exponent
				 * to 1, which is OK. */
				bits |= ( m >> ( 114 - e ) ) + ( ( m >> ( 113 - e ) ) & 1 );
				return bits;

			}

			bits |= ( ( e - 112 ) << 10 ) | ( m >> 1 );
			/* Extra rounding. An overflow will set mantissa to 0 and increment
			 * the exponent, which is OK. */
			bits += m & 1;
			return bits;

		}

		return function ( sourceArray, sourceOffset, destArray, destOffset ) {

			var e = sourceArray[ sourceOffset + 3 ];
			var scale = Math.pow( 2.0, e - 128.0 ) / 255.0;

			destArray[ destOffset + 0 ] = toHalf( sourceArray[ sourceOffset + 0 ] * scale );
			destArray[ destOffset + 1 ] = toHalf( sourceArray[ sourceOffset + 1 ] * scale );
			destArray[ destOffset + 2 ] = toHalf( sourceArray[ sourceOffset + 2 ] * scale );

		};

	} )();

	//

	var texture = new CubeTexture();

	texture.type = type;
	texture.encoding = ( type === UnsignedByteType ) ? RGBEEncoding : LinearEncoding;
	texture.format = ( type === UnsignedByteType ) ? RGBAFormat : RGBFormat;
	texture.minFilter = ( texture.encoding === RGBEEncoding ) ? NearestFilter : LinearFilter;
	texture.magFilter = ( texture.encoding === RGBEEncoding ) ? NearestFilter : LinearFilter;
	texture.generateMipmaps = ( texture.encoding !== RGBEEncoding );
	texture.anisotropy = 0;

	var scope = this;

	var loaded = 0;

	function loadHDRData( i, onLoad, onProgress, onError ) {

		var loader = new FileLoader( scope.manager );
		loader.setPath( scope.path );
		loader.setResponseType( 'arraybuffer' );
		loader.load( urls[ i ], function ( buffer ) {

			loaded ++;

			var texData = scope.hdrLoader._parser( buffer );

			if ( ! texData ) return;

			if ( type === FloatType ) {

				var numElements = ( texData.data.length / 4 ) * 3;
				var floatdata = new Float32Array( numElements );

				for ( var j = 0; j < numElements; j ++ ) {

					RGBEByteToRGBFloat( texData.data, j * 4, floatdata, j * 3 );

				}

				texData.data = floatdata;

			} else if ( type === HalfFloatType ) {

				var numElements = ( texData.data.length / 4 ) * 3;
				var halfdata = new Uint16Array( numElements );

				for ( var j = 0; j < numElements; j ++ ) {

					RGBEByteToRGBHalf( texData.data, j * 4, halfdata, j * 3 );

				}

				texData.data = halfdata;

			}

			if ( texData.image !== undefined ) {

				texture[ i ].images = texData.image;

			} else if ( texData.data !== undefined ) {

				var dataTexture = new DataTexture( texData.data, texData.width, texData.height );
				dataTexture.format = texture.format;
				dataTexture.type = texture.type;
				dataTexture.encoding = texture.encoding;
				dataTexture.minFilter = texture.minFilter;
				dataTexture.magFilter = texture.magFilter;
				dataTexture.generateMipmaps = texture.generateMipmaps;

				texture.images[ i ] = dataTexture;

			}

			if ( loaded === 6 ) {

				texture.needsUpdate = true;
				if ( onLoad ) onLoad( texture );

			}

		}, onProgress, onError );

	}

	for ( var i = 0; i < urls.length; i ++ ) {

		loadHDRData( i, onLoad, onProgress, onError );

	}

	return texture;

};

HDRCubeTextureLoader.prototype.setPath = function ( value ) {

	this.path = value;
	return this;

};


export default HDRCubeTextureLoader;
