import { WebGLUniforms } from './WebGLUniforms.js';
import { WebGLShader } from './WebGLShader.js';
import { ShaderChunk } from '../shaders/ShaderChunk.js';
import { NoToneMapping, AddOperation, MixOperation, MultiplyOperation, CubeRefractionMapping, CubeUVReflectionMapping, CubeReflectionMapping, PCFSoftShadowMap, PCFShadowMap, VSMShadowMap, ACESFilmicToneMapping, CineonToneMapping, CustomToneMapping, ReinhardToneMapping, LinearToneMapping, sRGBEncoding, LinearEncoding, GLSL3 } from '../../constants.js';

let programIdCount = 0;

function handleSource( string, errorLine ) {

	const lines = string.split( '\n' );
	const lines2 = [];

	const from = Math.max( errorLine - 6, 0 );
	const to = Math.min( errorLine + 6, lines.length );

	for ( let i = from; i < to; i ++ ) {

		lines2.push( ( i + 1 ) + ': ' + lines[ i ] );

	}

	return lines2.join( '\n' );

}

function getEncodingComponents( encoding ) {

	switch ( encoding ) {

		case LinearEncoding:
			return [ 'Linear', '( value )' ];
		case sRGBEncoding:
			return [ 'sRGB', '( value )' ];
		default:
			console.warn( 'THREE.WebGLProgram: Unsupported encoding:', encoding );
			return [ 'Linear', '( value )' ];

	}

}

function getShaderErrors( gl, shader, type ) {

	const status = gl.getShaderParameter( shader, gl.COMPILE_STATUS );
	const errors = gl.getShaderInfoLog( shader ).trim();

	if ( status && errors === '' ) return '';

	const errorMatches = /ERROR: 0:(\d+)/.exec( errors );
	if ( errorMatches ) {

		// --enable-privileged-webgl-extension
		// console.log( '**' + type + '**', gl.getExtension( 'WEBGL_debug_shaders' ).getTranslatedShaderSource( shader ) );

		const errorLine = parseInt( errorMatches[ 0 ] );
		return type.toUpperCase() + '\n\n' + errors + '\n\n' + handleSource( gl.getShaderSource( shader ), errorLine );

	} else {

		return errors;

	}

}

function getTexelEncodingFunction( functionName, encoding ) {

	const components = getEncodingComponents( encoding );
	return 'vec4 ' + functionName + '( vec4 value ) { return LinearTo' + components[ 0 ] + components[ 1 ] + '; }';

}

function getToneMappingFunction( functionName, toneMapping ) {

	let toneMappingName;

	switch ( toneMapping ) {

		case LinearToneMapping:
			toneMappingName = 'Linear';
			break;

		case ReinhardToneMapping:
			toneMappingName = 'Reinhard';
			break;

		case CineonToneMapping:
			toneMappingName = 'OptimizedCineon';
			break;

		case ACESFilmicToneMapping:
			toneMappingName = 'ACESFilmic';
			break;

		case CustomToneMapping:
			toneMappingName = 'Custom';
			break;

		default:
			console.warn( 'THREE.WebGLProgram: Unsupported toneMapping:', toneMapping );
			toneMappingName = 'Linear';

	}

	return 'vec3 ' + functionName + '( vec3 color ) { return ' + toneMappingName + 'ToneMapping( color ); }';

}

function generateExtensions( parameters ) {

	const chunks = [
		( parameters.extensionDerivatives || !! parameters.envMapCubeUVHeight || parameters.bumpMap || parameters.tangentSpaceNormalMap || parameters.clearcoatNormalMap || parameters.flatShading || parameters.shaderID === 'physical' ) ? '#extension GL_OES_standard_derivatives : enable' : '',
		( parameters.extensionFragDepth || parameters.logarithmicDepthBuffer ) && parameters.rendererExtensionFragDepth ? '#extension GL_EXT_frag_depth : enable' : '',
		( parameters.extensionDrawBuffers && parameters.rendererExtensionDrawBuffers ) ? '#extension GL_EXT_draw_buffers : require' : '',
		( parameters.extensionShaderTextureLOD || parameters.envMap || parameters.transmission ) && parameters.rendererExtensionShaderTextureLod ? '#extension GL_EXT_shader_texture_lod : enable' : ''
	];

	return chunks.filter( filterEmptyLine ).join( '\n' );

}

function generateDefines( defines ) {

	const chunks = [];

	for ( const name in defines ) {

		const value = defines[ name ];

		if ( value === false ) continue;

		chunks.push( '#define ' + name + ' ' + value );

	}

	return chunks.join( '\n' );

}

function fetchAttributeLocations( gl, program ) {

	const attributes = {};

	const n = gl.getProgramParameter( program, gl.ACTIVE_ATTRIBUTES );

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

		const info = gl.getActiveAttrib( program, i );
		const name = info.name;

		let locationSize = 1;
		if ( info.type === gl.FLOAT_MAT2 ) locationSize = 2;
		if ( info.type === gl.FLOAT_MAT3 ) locationSize = 3;
		if ( info.type === gl.FLOAT_MAT4 ) locationSize = 4;

		// console.log( 'THREE.WebGLProgram: ACTIVE VERTEX ATTRIBUTE:', name, i );

		attributes[ name ] = {
			type: info.type,
			location: gl.getAttribLocation( program, name ),
			locationSize: locationSize
		};

	}

	return attributes;

}

function filterEmptyLine( string ) {

	return string !== '';

}

function replaceLightNums( string, parameters ) {

	return string
		.replace( /NUM_DIR_LIGHTS/g, parameters.numDirLights )
		.replace( /NUM_SPOT_LIGHTS/g, parameters.numSpotLights )
		.replace( /NUM_RECT_AREA_LIGHTS/g, parameters.numRectAreaLights )
		.replace( /NUM_POINT_LIGHTS/g, parameters.numPointLights )
		.replace( /NUM_HEMI_LIGHTS/g, parameters.numHemiLights )
		.replace( /NUM_DIR_LIGHT_SHADOWS/g, parameters.numDirLightShadows )
		.replace( /NUM_SPOT_LIGHT_SHADOWS/g, parameters.numSpotLightShadows )
		.replace( /NUM_POINT_LIGHT_SHADOWS/g, parameters.numPointLightShadows );

}

function replaceClippingPlaneNums( string, parameters ) {

	return string
		.replace( /NUM_CLIPPING_PLANES/g, parameters.numClippingPlanes )
		.replace( /UNION_CLIPPING_PLANES/g, ( parameters.numClippingPlanes - parameters.numClipIntersection ) );

}

// Resolve Includes

const includePattern = /^[ \t]*#include +<([\w\d./]+)>/gm;

function resolveIncludes( string ) {

	return string.replace( includePattern, includeReplacer );

}

function includeReplacer( match, include ) {

	const string = ShaderChunk[ include ];

	if ( string === undefined ) {

		throw new Error( 'Can not resolve #include <' + include + '>' );

	}

	return resolveIncludes( string );

}

// Unroll Loops

const deprecatedUnrollLoopPattern = /#pragma unroll_loop[\s]+?for \( int i \= (\d+)\; i < (\d+)\; i \+\+ \) \{([\s\S]+?)(?=\})\}/g;
const unrollLoopPattern = /#pragma unroll_loop_start\s+for\s*\(\s*int\s+i\s*=\s*(\d+)\s*;\s*i\s*<\s*(\d+)\s*;\s*i\s*\+\+\s*\)\s*{([\s\S]+?)}\s+#pragma unroll_loop_end/g;

function unrollLoops( string ) {

	return string
		.replace( unrollLoopPattern, loopReplacer )
		.replace( deprecatedUnrollLoopPattern, deprecatedLoopReplacer );

}

function deprecatedLoopReplacer( match, start, end, snippet ) {

	console.warn( 'WebGLProgram: #pragma unroll_loop shader syntax is deprecated. Please use #pragma unroll_loop_start syntax instead.' );
	return loopReplacer( match, start, end, snippet );

}

function loopReplacer( match, start, end, snippet ) {

	let string = '';

	for ( let i = parseInt( start ); i < parseInt( end ); i ++ ) {

		string += snippet
			.replace( /\[\s*i\s*\]/g, '[ ' + i + ' ]' )
			.replace( /UNROLLED_LOOP_INDEX/g, i );

	}

	return string;

}

//

function generatePrecision( parameters ) {

	let precisionstring = 'precision ' + parameters.precision + ' float;\nprecision ' + parameters.precision + ' int;';

	if ( parameters.precision === 'highp' ) {

		precisionstring += '\n#define HIGH_PRECISION';

	} else if ( parameters.precision === 'mediump' ) {

		precisionstring += '\n#define MEDIUM_PRECISION';

	} else if ( parameters.precision === 'lowp' ) {

		precisionstring += '\n#define LOW_PRECISION';

	}

	return precisionstring;

}

function generateShadowMapTypeDefine( parameters ) {

	let shadowMapTypeDefine = 'SHADOWMAP_TYPE_BASIC';

	if ( parameters.shadowMapType === PCFShadowMap ) {

		shadowMapTypeDefine = 'SHADOWMAP_TYPE_PCF';

	} else if ( parameters.shadowMapType === PCFSoftShadowMap ) {

		shadowMapTypeDefine = 'SHADOWMAP_TYPE_PCF_SOFT';

	} else if ( parameters.shadowMapType === VSMShadowMap ) {

		shadowMapTypeDefine = 'SHADOWMAP_TYPE_VSM';

	}

	return shadowMapTypeDefine;

}

function generateEnvMapTypeDefine( parameters ) {

	let envMapTypeDefine = 'ENVMAP_TYPE_CUBE';

	if ( parameters.envMap ) {

		switch ( parameters.envMapMode ) {

			case CubeReflectionMapping:
			case CubeRefractionMapping:
				envMapTypeDefine = 'ENVMAP_TYPE_CUBE';
				break;

			case CubeUVReflectionMapping:
				envMapTypeDefine = 'ENVMAP_TYPE_CUBE_UV';
				break;

		}

	}

	return envMapTypeDefine;

}

function generateEnvMapModeDefine( parameters ) {

	let envMapModeDefine = 'ENVMAP_MODE_REFLECTION';

	if ( parameters.envMap ) {

		switch ( parameters.envMapMode ) {

			case CubeRefractionMapping:

				envMapModeDefine = 'ENVMAP_MODE_REFRACTION';
				break;

		}

	}

	return envMapModeDefine;

}

function generateEnvMapBlendingDefine( parameters ) {

	let envMapBlendingDefine = 'ENVMAP_BLENDING_NONE';

	if ( parameters.envMap ) {

		switch ( parameters.combine ) {

			case MultiplyOperation:
				envMapBlendingDefine = 'ENVMAP_BLENDING_MULTIPLY';
				break;

			case MixOperation:
				envMapBlendingDefine = 'ENVMAP_BLENDING_MIX';
				break;

			case AddOperation:
				envMapBlendingDefine = 'ENVMAP_BLENDING_ADD';
				break;

		}

	}

	return envMapBlendingDefine;

}

function generateCubeUVSize( parameters ) {

	const imageHeight = parameters.envMapCubeUVHeight;

	if ( imageHeight === null ) return null;

	const maxMip = Math.log2( imageHeight ) - 2;

	const texelHeight = 1.0 / imageHeight;

	const texelWidth = 1.0 / ( 3 * Math.max( Math.pow( 2, maxMip ), 7 * 16 ) );

	return { texelWidth, texelHeight, maxMip };

}

function WebGLProgram( renderer, cacheKey, parameters, bindingStates ) {

	// TODO Send this event to Three.js DevTools
	// console.log( 'WebGLProgram', cacheKey );

	const gl = renderer.getContext();

	const defines = parameters.defines;

	let vertexShader = parameters.vertexShader;
	let fragmentShader = parameters.fragmentShader;

	const shadowMapTypeDefine = generateShadowMapTypeDefine( parameters );
	const envMapTypeDefine = generateEnvMapTypeDefine( parameters );
	const envMapModeDefine = generateEnvMapModeDefine( parameters );
	const envMapBlendingDefine = generateEnvMapBlendingDefine( parameters );
	const envMapCubeUVSize = generateCubeUVSize( parameters );

	const customExtensions = parameters.isWebGL2 ? '' : generateExtensions( parameters );

	const customDefines = generateDefines( defines );

	const program = gl.createProgram();

	let prefixVertex, prefixFragment;
	let versionString = parameters.glslVersion ? '#version ' + parameters.glslVersion + '\n' : '';

	if ( parameters.isRawShaderMaterial ) {

		prefixVertex = [

			customDefines

		].filter( filterEmptyLine ).join( '\n' );

		if ( prefixVertex.length > 0 ) {

			prefixVertex += '\n';

		}

		prefixFragment = [

			customExtensions,
			customDefines

		].filter( filterEmptyLine ).join( '\n' );

		if ( prefixFragment.length > 0 ) {

			prefixFragment += '\n';

		}

	} else {

		prefixVertex = [

			generatePrecision( parameters ),

			'#define SHADER_NAME ' + parameters.shaderName,

			customDefines,

			parameters.instancing ? '#define USE_INSTANCING' : '',
			parameters.instancingColor ? '#define USE_INSTANCING_COLOR' : '',

			parameters.supportsVertexTextures ? '#define VERTEX_TEXTURES' : '',

			'#define MAX_BONES ' + parameters.maxBones,
			( parameters.useFog && parameters.fog ) ? '#define USE_FOG' : '',
			( parameters.useFog && parameters.fogExp2 ) ? '#define FOG_EXP2' : '',

			parameters.map ? '#define USE_MAP' : '',
			parameters.envMap ? '#define USE_ENVMAP' : '',
			parameters.envMap ? '#define ' + envMapModeDefine : '',
			parameters.lightMap ? '#define USE_LIGHTMAP' : '',
			parameters.aoMap ? '#define USE_AOMAP' : '',
			parameters.emissiveMap ? '#define USE_EMISSIVEMAP' : '',
			parameters.bumpMap ? '#define USE_BUMPMAP' : '',
			parameters.normalMap ? '#define USE_NORMALMAP' : '',
			( parameters.normalMap && parameters.objectSpaceNormalMap ) ? '#define OBJECTSPACE_NORMALMAP' : '',
			( parameters.normalMap && parameters.tangentSpaceNormalMap ) ? '#define TANGENTSPACE_NORMALMAP' : '',

			parameters.clearcoatMap ? '#define USE_CLEARCOATMAP' : '',
			parameters.clearcoatRoughnessMap ? '#define USE_CLEARCOAT_ROUGHNESSMAP' : '',
			parameters.clearcoatNormalMap ? '#define USE_CLEARCOAT_NORMALMAP' : '',

			parameters.displacementMap && parameters.supportsVertexTextures ? '#define USE_DISPLACEMENTMAP' : '',

			parameters.specularMap ? '#define USE_SPECULARMAP' : '',
			parameters.specularIntensityMap ? '#define USE_SPECULARINTENSITYMAP' : '',
			parameters.specularColorMap ? '#define USE_SPECULARCOLORMAP' : '',

			parameters.roughnessMap ? '#define USE_ROUGHNESSMAP' : '',
			parameters.metalnessMap ? '#define USE_METALNESSMAP' : '',
			parameters.alphaMap ? '#define USE_ALPHAMAP' : '',

			parameters.transmission ? '#define USE_TRANSMISSION' : '',
			parameters.transmissionMap ? '#define USE_TRANSMISSIONMAP' : '',
			parameters.thicknessMap ? '#define USE_THICKNESSMAP' : '',

			parameters.sheenColorMap ? '#define USE_SHEENCOLORMAP' : '',
			parameters.sheenRoughnessMap ? '#define USE_SHEENROUGHNESSMAP' : '',

			parameters.vertexTangents ? '#define USE_TANGENT' : '',
			parameters.vertexColors ? '#define USE_COLOR' : '',
			parameters.vertexAlphas ? '#define USE_COLOR_ALPHA' : '',
			parameters.vertexUvs ? '#define USE_UV' : '',
			parameters.uvsVertexOnly ? '#define UVS_VERTEX_ONLY' : '',

			parameters.flatShading ? '#define FLAT_SHADED' : '',

			parameters.skinning ? '#define USE_SKINNING' : '',
			parameters.useVertexTexture ? '#define BONE_TEXTURE' : '',

			parameters.morphTargets ? '#define USE_MORPHTARGETS' : '',
			parameters.morphNormals && parameters.flatShading === false ? '#define USE_MORPHNORMALS' : '',
			( parameters.morphColors && parameters.isWebGL2 ) ? '#define USE_MORPHCOLORS' : '',
			( parameters.morphTargetsCount > 0 && parameters.isWebGL2 ) ? '#define MORPHTARGETS_TEXTURE' : '',
			( parameters.morphTargetsCount > 0 && parameters.isWebGL2 ) ? '#define MORPHTARGETS_TEXTURE_STRIDE ' + parameters.morphTextureStride : '',
			( parameters.morphTargetsCount > 0 && parameters.isWebGL2 ) ? '#define MORPHTARGETS_COUNT ' + parameters.morphTargetsCount : '',
			parameters.doubleSided ? '#define DOUBLE_SIDED' : '',
			parameters.flipSided ? '#define FLIP_SIDED' : '',

			parameters.shadowMapEnabled ? '#define USE_SHADOWMAP' : '',
			parameters.shadowMapEnabled ? '#define ' + shadowMapTypeDefine : '',

			parameters.sizeAttenuation ? '#define USE_SIZEATTENUATION' : '',

			parameters.logarithmicDepthBuffer ? '#define USE_LOGDEPTHBUF' : '',
			( parameters.logarithmicDepthBuffer && parameters.rendererExtensionFragDepth ) ? '#define USE_LOGDEPTHBUF_EXT' : '',

			'uniform mat4 modelMatrix;',
			'uniform mat4 modelViewMatrix;',
			'uniform mat4 projectionMatrix;',
			'uniform mat4 viewMatrix;',
			'uniform mat3 normalMatrix;',
			'uniform vec3 cameraPosition;',
			'uniform bool isOrthographic;',

			'#ifdef USE_INSTANCING',

			'	attribute mat4 instanceMatrix;',

			'#endif',

			'#ifdef USE_INSTANCING_COLOR',

			'	attribute vec3 instanceColor;',

			'#endif',

			'attribute vec3 position;',
			'attribute vec3 normal;',
			'attribute vec2 uv;',

			'#ifdef USE_TANGENT',

			'	attribute vec4 tangent;',

			'#endif',

			'#if defined( USE_COLOR_ALPHA )',

			'	attribute vec4 color;',

			'#elif defined( USE_COLOR )',

			'	attribute vec3 color;',

			'#endif',

			'#if ( defined( USE_MORPHTARGETS ) && ! defined( MORPHTARGETS_TEXTURE ) )',

			'	attribute vec3 morphTarget0;',
			'	attribute vec3 morphTarget1;',
			'	attribute vec3 morphTarget2;',
			'	attribute vec3 morphTarget3;',

			'	#ifdef USE_MORPHNORMALS',

			'		attribute vec3 morphNormal0;',
			'		attribute vec3 morphNormal1;',
			'		attribute vec3 morphNormal2;',
			'		attribute vec3 morphNormal3;',

			'	#else',

			'		attribute vec3 morphTarget4;',
			'		attribute vec3 morphTarget5;',
			'		attribute vec3 morphTarget6;',
			'		attribute vec3 morphTarget7;',

			'	#endif',

			'#endif',

			'#ifdef USE_SKINNING',

			'	attribute vec4 skinIndex;',
			'	attribute vec4 skinWeight;',

			'#endif',

			'\n'

		].filter( filterEmptyLine ).join( '\n' );

		prefixFragment = [

			customExtensions,

			generatePrecision( parameters ),

			'#define SHADER_NAME ' + parameters.shaderName,

			customDefines,

			( parameters.useFog && parameters.fog ) ? '#define USE_FOG' : '',
			( parameters.useFog && parameters.fogExp2 ) ? '#define FOG_EXP2' : '',

			parameters.map ? '#define USE_MAP' : '',
			parameters.matcap ? '#define USE_MATCAP' : '',
			parameters.envMap ? '#define USE_ENVMAP' : '',
			parameters.envMap ? '#define ' + envMapTypeDefine : '',
			parameters.envMap ? '#define ' + envMapModeDefine : '',
			parameters.envMap ? '#define ' + envMapBlendingDefine : '',
			envMapCubeUVSize ? '#define CUBEUV_TEXEL_WIDTH ' + envMapCubeUVSize.texelWidth : '',
			envMapCubeUVSize ? '#define CUBEUV_TEXEL_HEIGHT ' + envMapCubeUVSize.texelHeight : '',
			envMapCubeUVSize ? '#define CUBEUV_MAX_MIP ' + envMapCubeUVSize.maxMip + '.0' : '',
			parameters.lightMap ? '#define USE_LIGHTMAP' : '',
			parameters.aoMap ? '#define USE_AOMAP' : '',
			parameters.emissiveMap ? '#define USE_EMISSIVEMAP' : '',
			parameters.bumpMap ? '#define USE_BUMPMAP' : '',
			parameters.normalMap ? '#define USE_NORMALMAP' : '',
			( parameters.normalMap && parameters.objectSpaceNormalMap ) ? '#define OBJECTSPACE_NORMALMAP' : '',
			( parameters.normalMap && parameters.tangentSpaceNormalMap ) ? '#define TANGENTSPACE_NORMALMAP' : '',

			parameters.clearcoat ? '#define USE_CLEARCOAT' : '',
			parameters.clearcoatMap ? '#define USE_CLEARCOATMAP' : '',
			parameters.clearcoatRoughnessMap ? '#define USE_CLEARCOAT_ROUGHNESSMAP' : '',
			parameters.clearcoatNormalMap ? '#define USE_CLEARCOAT_NORMALMAP' : '',

			parameters.specularMap ? '#define USE_SPECULARMAP' : '',
			parameters.specularIntensityMap ? '#define USE_SPECULARINTENSITYMAP' : '',
			parameters.specularColorMap ? '#define USE_SPECULARCOLORMAP' : '',
			parameters.roughnessMap ? '#define USE_ROUGHNESSMAP' : '',
			parameters.metalnessMap ? '#define USE_METALNESSMAP' : '',

			parameters.alphaMap ? '#define USE_ALPHAMAP' : '',
			parameters.alphaTest ? '#define USE_ALPHATEST' : '',

			parameters.sheen ? '#define USE_SHEEN' : '',
			parameters.sheenColorMap ? '#define USE_SHEENCOLORMAP' : '',
			parameters.sheenRoughnessMap ? '#define USE_SHEENROUGHNESSMAP' : '',

			parameters.transmission ? '#define USE_TRANSMISSION' : '',
			parameters.transmissionMap ? '#define USE_TRANSMISSIONMAP' : '',
			parameters.thicknessMap ? '#define USE_THICKNESSMAP' : '',

			parameters.decodeVideoTexture ? '#define DECODE_VIDEO_TEXTURE' : '',

			parameters.vertexTangents ? '#define USE_TANGENT' : '',
			parameters.vertexColors || parameters.instancingColor ? '#define USE_COLOR' : '',
			parameters.vertexAlphas ? '#define USE_COLOR_ALPHA' : '',
			parameters.vertexUvs ? '#define USE_UV' : '',
			parameters.uvsVertexOnly ? '#define UVS_VERTEX_ONLY' : '',

			parameters.gradientMap ? '#define USE_GRADIENTMAP' : '',

			parameters.flatShading ? '#define FLAT_SHADED' : '',

			parameters.doubleSided ? '#define DOUBLE_SIDED' : '',
			parameters.flipSided ? '#define FLIP_SIDED' : '',

			parameters.shadowMapEnabled ? '#define USE_SHADOWMAP' : '',
			parameters.shadowMapEnabled ? '#define ' + shadowMapTypeDefine : '',

			parameters.premultipliedAlpha ? '#define PREMULTIPLIED_ALPHA' : '',

			parameters.physicallyCorrectLights ? '#define PHYSICALLY_CORRECT_LIGHTS' : '',

			parameters.logarithmicDepthBuffer ? '#define USE_LOGDEPTHBUF' : '',
			( parameters.logarithmicDepthBuffer && parameters.rendererExtensionFragDepth ) ? '#define USE_LOGDEPTHBUF_EXT' : '',

			'uniform mat4 viewMatrix;',
			'uniform vec3 cameraPosition;',
			'uniform bool isOrthographic;',

			( parameters.toneMapping !== NoToneMapping ) ? '#define TONE_MAPPING' : '',
			( parameters.toneMapping !== NoToneMapping ) ? ShaderChunk[ 'tonemapping_pars_fragment' ] : '', // this code is required here because it is used by the toneMapping() function defined below
			( parameters.toneMapping !== NoToneMapping ) ? getToneMappingFunction( 'toneMapping', parameters.toneMapping ) : '',

			parameters.dithering ? '#define DITHERING' : '',
			parameters.opaque ? '#define OPAQUE' : '',

			ShaderChunk[ 'encodings_pars_fragment' ], // this code is required here because it is used by the various encoding/decoding function defined below
			getTexelEncodingFunction( 'linearToOutputTexel', parameters.outputEncoding ),

			parameters.useDepthPacking ? '#define DEPTH_PACKING ' + parameters.depthPacking : '',

			'\n'

		].filter( filterEmptyLine ).join( '\n' );

	}

	vertexShader = resolveIncludes( vertexShader );
	vertexShader = replaceLightNums( vertexShader, parameters );
	vertexShader = replaceClippingPlaneNums( vertexShader, parameters );

	fragmentShader = resolveIncludes( fragmentShader );
	fragmentShader = replaceLightNums( fragmentShader, parameters );
	fragmentShader = replaceClippingPlaneNums( fragmentShader, parameters );

	vertexShader = unrollLoops( vertexShader );
	fragmentShader = unrollLoops( fragmentShader );

	if ( parameters.isWebGL2 && parameters.isRawShaderMaterial !== true ) {

		// GLSL 3.0 conversion for built-in materials and ShaderMaterial

		versionString = '#version 300 es\n';

		prefixVertex = [
			'precision mediump sampler2DArray;',
			'#define attribute in',
			'#define varying out',
			'#define texture2D texture'
		].join( '\n' ) + '\n' + prefixVertex;

		prefixFragment = [
			'#define varying in',
			( parameters.glslVersion === GLSL3 ) ? '' : 'layout(location = 0) out highp vec4 pc_fragColor;',
			( parameters.glslVersion === GLSL3 ) ? '' : '#define gl_FragColor pc_fragColor',
			'#define gl_FragDepthEXT gl_FragDepth',
			'#define texture2D texture',
			'#define textureCube texture',
			'#define texture2DProj textureProj',
			'#define texture2DLodEXT textureLod',
			'#define texture2DProjLodEXT textureProjLod',
			'#define textureCubeLodEXT textureLod',
			'#define texture2DGradEXT textureGrad',
			'#define texture2DProjGradEXT textureProjGrad',
			'#define textureCubeGradEXT textureGrad'
		].join( '\n' ) + '\n' + prefixFragment;

	}

	const vertexGlsl = versionString + prefixVertex + vertexShader;
	const fragmentGlsl = versionString + prefixFragment + fragmentShader;

	// console.log( '*VERTEX*', vertexGlsl );
	// console.log( '*FRAGMENT*', fragmentGlsl );

	const glVertexShader = WebGLShader( gl, gl.VERTEX_SHADER, vertexGlsl );
	const glFragmentShader = WebGLShader( gl, gl.FRAGMENT_SHADER, fragmentGlsl );

	gl.attachShader( program, glVertexShader );
	gl.attachShader( program, glFragmentShader );

	// Force a particular attribute to index 0.

	if ( parameters.index0AttributeName !== undefined ) {

		gl.bindAttribLocation( program, 0, parameters.index0AttributeName );

	} else if ( parameters.morphTargets === true ) {

		// programs with morphTargets displace position out of attribute 0
		gl.bindAttribLocation( program, 0, 'position' );

	}

	gl.linkProgram( program );

	// check for link errors
	if ( renderer.debug.checkShaderErrors ) {

		const programLog = gl.getProgramInfoLog( program ).trim();
		const vertexLog = gl.getShaderInfoLog( glVertexShader ).trim();
		const fragmentLog = gl.getShaderInfoLog( glFragmentShader ).trim();

		let runnable = true;
		let haveDiagnostics = true;

		if ( gl.getProgramParameter( program, gl.LINK_STATUS ) === false ) {

			runnable = false;

			const vertexErrors = getShaderErrors( gl, glVertexShader, 'vertex' );
			const fragmentErrors = getShaderErrors( gl, glFragmentShader, 'fragment' );

			console.error(
				'THREE.WebGLProgram: Shader Error ' + gl.getError() + ' - ' +
				'VALIDATE_STATUS ' + gl.getProgramParameter( program, gl.VALIDATE_STATUS ) + '\n\n' +
				'Program Info Log: ' + programLog + '\n' +
				vertexErrors + '\n' +
				fragmentErrors
			);

		} else if ( programLog !== '' ) {

			console.warn( 'THREE.WebGLProgram: Program Info Log:', programLog );

		} else if ( vertexLog === '' || fragmentLog === '' ) {

			haveDiagnostics = false;

		}

		if ( haveDiagnostics ) {

			this.diagnostics = {

				runnable: runnable,

				programLog: programLog,

				vertexShader: {

					log: vertexLog,
					prefix: prefixVertex

				},

				fragmentShader: {

					log: fragmentLog,
					prefix: prefixFragment

				}

			};

		}

	}

	// Clean up

	// Crashes in iOS9 and iOS10. #18402
	// gl.detachShader( program, glVertexShader );
	// gl.detachShader( program, glFragmentShader );

	gl.deleteShader( glVertexShader );
	gl.deleteShader( glFragmentShader );

	// set up caching for uniform locations

	let cachedUniforms;

	this.getUniforms = function () {

		if ( cachedUniforms === undefined ) {

			cachedUniforms = new WebGLUniforms( gl, program );

		}

		return cachedUniforms;

	};

	// set up caching for attribute locations

	let cachedAttributes;

	this.getAttributes = function () {

		if ( cachedAttributes === undefined ) {

			cachedAttributes = fetchAttributeLocations( gl, program );

		}

		return cachedAttributes;

	};

	// free resource

	this.destroy = function () {

		bindingStates.releaseStatesOfProgram( this );

		gl.deleteProgram( program );
		this.program = undefined;

	};

	//

	this.name = parameters.shaderName;
	this.id = programIdCount ++;
	this.cacheKey = cacheKey;
	this.usedTimes = 1;
	this.program = program;
	this.vertexShader = glVertexShader;
	this.fragmentShader = glFragmentShader;

	return this;

}

export { WebGLProgram };
