/**
 * @author alteredq / http://alteredqualia.com/
 *
 */

import {
	Color,
	ShaderChunk,
	UniformsLib,
	UniformsUtils,
	Vector2
} from "../../../build/three.module.js";

var TerrainShader = {

	/* -------------------------------------------------------------------------
	//	Dynamic terrain shader
	//		- Blinn-Phong
	//		- height + normal + diffuse1 + diffuse2 + specular + detail maps
	//		- point, directional and hemisphere lights (use with "lights: true" material option)
	//		- shadow maps receiving
	 ------------------------------------------------------------------------- */

	uniforms: UniformsUtils.merge( [

		UniformsLib[ "fog" ],
		UniformsLib[ "lights" ],

		{

			"enableDiffuse1": { value: 0 },
			"enableDiffuse2": { value: 0 },
			"enableSpecular": { value: 0 },
			"enableReflection": { value: 0 },

			"tDiffuse1": { value: null },
			"tDiffuse2": { value: null },
			"tDetail": { value: null },
			"tNormal": { value: null },
			"tSpecular": { value: null },
			"tDisplacement": { value: null },

			"uNormalScale": { value: 1.0 },

			"uDisplacementBias": { value: 0.0 },
			"uDisplacementScale": { value: 1.0 },

			"diffuse": { value: new Color( 0xeeeeee ) },
			"specular": { value: new Color( 0x111111 ) },
			"shininess": { value: 30 },
			"opacity": { value: 1 },

			"uRepeatBase": { value: new Vector2( 1, 1 ) },
			"uRepeatOverlay": { value: new Vector2( 1, 1 ) },

			"uOffset": { value: new Vector2( 0, 0 ) }

		}

	] ),

	fragmentShader: [

		"uniform vec3 diffuse;",
		"uniform vec3 specular;",
		"uniform float shininess;",
		"uniform float opacity;",

		"uniform bool enableDiffuse1;",
		"uniform bool enableDiffuse2;",
		"uniform bool enableSpecular;",

		"uniform sampler2D tDiffuse1;",
		"uniform sampler2D tDiffuse2;",
		"uniform sampler2D tDetail;",
		"uniform sampler2D tNormal;",
		"uniform sampler2D tSpecular;",
		"uniform sampler2D tDisplacement;",

		"uniform float uNormalScale;",

		"uniform vec2 uRepeatOverlay;",
		"uniform vec2 uRepeatBase;",

		"uniform vec2 uOffset;",

		"varying vec3 vTangent;",
		"varying vec3 vBinormal;",
		"varying vec3 vNormal;",
		"varying vec2 vUv;",

		"varying vec3 vViewPosition;",

		ShaderChunk[ "common" ],
		ShaderChunk[ "bsdfs" ],
		ShaderChunk[ "lights_pars_begin" ],
		ShaderChunk[ "shadowmap_pars_fragment" ],
		ShaderChunk[ "fog_pars_fragment" ],

		"float calcLightAttenuation( float lightDistance, float cutoffDistance, float decayExponent ) {",
		"		if ( decayExponent > 0.0 ) {",
		"			return pow( saturate( - lightDistance / cutoffDistance + 1.0 ), decayExponent );",
		"		}",
		"		return 1.0;",
		"	}",

		"void main() {",

		"	vec3 outgoingLight = vec3( 0.0 );",	// outgoing light does not have an alpha, the surface does
		"	vec4 diffuseColor = vec4( diffuse, opacity );",

		"	vec3 specularTex = vec3( 1.0 );",

		"	vec2 uvOverlay = uRepeatOverlay * vUv + uOffset;",
		"	vec2 uvBase = uRepeatBase * vUv;",

		"	vec3 normalTex = texture2D( tDetail, uvOverlay ).xyz * 2.0 - 1.0;",
		"	normalTex.xy *= uNormalScale;",
		"	normalTex = normalize( normalTex );",

		"	if( enableDiffuse1 && enableDiffuse2 ) {",

		"		vec4 colDiffuse1 = texture2D( tDiffuse1, uvOverlay );",
		"		vec4 colDiffuse2 = texture2D( tDiffuse2, uvOverlay );",

		"		colDiffuse1 = GammaToLinear( colDiffuse1, float( GAMMA_FACTOR ) );",
		"		colDiffuse2 = GammaToLinear( colDiffuse2, float( GAMMA_FACTOR ) );",

		"		diffuseColor *= mix ( colDiffuse1, colDiffuse2, 1.0 - texture2D( tDisplacement, uvBase ) );",

		"	 } else if( enableDiffuse1 ) {",

		"		diffuseColor *= texture2D( tDiffuse1, uvOverlay );",

		"	} else if( enableDiffuse2 ) {",

		"		diffuseColor *= texture2D( tDiffuse2, uvOverlay );",

		"	}",

		"	if( enableSpecular )",
		"		specularTex = texture2D( tSpecular, uvOverlay ).xyz;",

		"	mat3 tsb = mat3( vTangent, vBinormal, vNormal );",
		"	vec3 finalNormal = tsb * normalTex;",

		"	vec3 normal = normalize( finalNormal );",
		"	vec3 viewPosition = normalize( vViewPosition );",

		"	vec3 totalDiffuseLight = vec3( 0.0 );",
		"	vec3 totalSpecularLight = vec3( 0.0 );",

		// point lights

		"	#if NUM_POINT_LIGHTS > 0",

		"		for ( int i = 0; i < NUM_POINT_LIGHTS; i ++ ) {",

		"			vec3 lVector = pointLights[ i ].position + vViewPosition.xyz;",

		"			float attenuation = calcLightAttenuation( length( lVector ), pointLights[ i ].distance, pointLights[ i ].decay );",

		"			lVector = normalize( lVector );",

		"			vec3 pointHalfVector = normalize( lVector + viewPosition );",

		"			float pointDotNormalHalf = max( dot( normal, pointHalfVector ), 0.0 );",
		"			float pointDiffuseWeight = max( dot( normal, lVector ), 0.0 );",

		"			float pointSpecularWeight = specularTex.r * max( pow( pointDotNormalHalf, shininess ), 0.0 );",

		"			totalDiffuseLight += attenuation * pointLights[ i ].color * pointDiffuseWeight;",
		"			totalSpecularLight += attenuation * pointLights[ i ].color * specular * pointSpecularWeight * pointDiffuseWeight;",

		"		}",

		"	#endif",

		// directional lights

		"	#if NUM_DIR_LIGHTS > 0",

		"		vec3 dirDiffuse = vec3( 0.0 );",
		"		vec3 dirSpecular = vec3( 0.0 );",

		"		for( int i = 0; i < NUM_DIR_LIGHTS; i++ ) {",

		"			vec3 dirVector = directionalLights[ i ].direction;",
		"			vec3 dirHalfVector = normalize( dirVector + viewPosition );",

		"			float dirDotNormalHalf = max( dot( normal, dirHalfVector ), 0.0 );",
		"			float dirDiffuseWeight = max( dot( normal, dirVector ), 0.0 );",

		"			float dirSpecularWeight = specularTex.r * max( pow( dirDotNormalHalf, shininess ), 0.0 );",

		"			totalDiffuseLight += directionalLights[ i ].color * dirDiffuseWeight;",
		"			totalSpecularLight += directionalLights[ i ].color * specular * dirSpecularWeight * dirDiffuseWeight;",

		"		}",

		"	#endif",

		// hemisphere lights

		"	#if NUM_HEMI_LIGHTS > 0",

		"		vec3 hemiDiffuse  = vec3( 0.0 );",
		"		vec3 hemiSpecular = vec3( 0.0 );",

		"		for( int i = 0; i < NUM_HEMI_LIGHTS; i ++ ) {",

		"			vec3 lVector = hemisphereLightDirection[ i ];",

		// diffuse

		"			float dotProduct = dot( normal, lVector );",
		"			float hemiDiffuseWeight = 0.5 * dotProduct + 0.5;",

		"			totalDiffuseLight += mix( hemisphereLights[ i ].groundColor, hemisphereLights[ i ].skyColor, hemiDiffuseWeight );",

		// specular (sky light)

		"			float hemiSpecularWeight = 0.0;",

		"			vec3 hemiHalfVectorSky = normalize( lVector + viewPosition );",
		"			float hemiDotNormalHalfSky = 0.5 * dot( normal, hemiHalfVectorSky ) + 0.5;",
		"			hemiSpecularWeight += specularTex.r * max( pow( hemiDotNormalHalfSky, shininess ), 0.0 );",

		// specular (ground light)

		"			vec3 lVectorGround = -lVector;",

		"			vec3 hemiHalfVectorGround = normalize( lVectorGround + viewPosition );",
		"			float hemiDotNormalHalfGround = 0.5 * dot( normal, hemiHalfVectorGround ) + 0.5;",
		"			hemiSpecularWeight += specularTex.r * max( pow( hemiDotNormalHalfGround, shininess ), 0.0 );",

		"			totalSpecularLight += specular * mix( hemisphereLights[ i ].groundColor, hemisphereLights[ i ].skyColor, hemiDiffuseWeight ) * hemiSpecularWeight * hemiDiffuseWeight;",

		"		}",

		"	#endif",

		"	outgoingLight += diffuseColor.xyz * ( totalDiffuseLight + ambientLightColor + totalSpecularLight );",

		"	gl_FragColor = vec4( outgoingLight, diffuseColor.a );",	// TODO, this should be pre-multiplied to allow for bright highlights on very transparent objects

		ShaderChunk[ "fog_fragment" ],

		"}"

	].join( "\n" ),

	vertexShader: [

		"attribute vec4 tangent;",

		"uniform vec2 uRepeatBase;",

		"uniform sampler2D tNormal;",

		"#ifdef VERTEX_TEXTURES",

		"	uniform sampler2D tDisplacement;",
		"	uniform float uDisplacementScale;",
		"	uniform float uDisplacementBias;",

		"#endif",

		"varying vec3 vTangent;",
		"varying vec3 vBinormal;",
		"varying vec3 vNormal;",
		"varying vec2 vUv;",

		"varying vec3 vViewPosition;",

		ShaderChunk[ "shadowmap_pars_vertex" ],
		ShaderChunk[ "fog_pars_vertex" ],

		"void main() {",

		"	vNormal = normalize( normalMatrix * normal );",

		// tangent and binormal vectors

		"	vTangent = normalize( normalMatrix * tangent.xyz );",

		"	vBinormal = cross( vNormal, vTangent ) * tangent.w;",
		"	vBinormal = normalize( vBinormal );",

		// texture coordinates

		"	vUv = uv;",

		"	vec2 uvBase = uv * uRepeatBase;",

		// displacement mapping

		"	#ifdef VERTEX_TEXTURES",

		"		vec3 dv = texture2D( tDisplacement, uvBase ).xyz;",
		"		float df = uDisplacementScale * dv.x + uDisplacementBias;",
		"		vec3 displacedPosition = normal * df + position;",

		"		vec4 worldPosition = modelMatrix * vec4( displacedPosition, 1.0 );",
		"		vec4 mvPosition = modelViewMatrix * vec4( displacedPosition, 1.0 );",

		"	#else",

		"		vec4 worldPosition = modelMatrix * vec4( position, 1.0 );",
		"		vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );",

		"	#endif",

		"	gl_Position = projectionMatrix * mvPosition;",

		"	vViewPosition = -mvPosition.xyz;",

		"	vec3 normalTex = texture2D( tNormal, uvBase ).xyz * 2.0 - 1.0;",
		"	vNormal = normalMatrix * normalTex;",

		ShaderChunk[ "shadowmap_vertex" ],
		ShaderChunk[ "fog_vertex" ],

		"}"

	].join( "\n" )

};

export { TerrainShader };
