/**
 * @author Mugen87 / https://github.com/Mugen87
 * @author mrdoob / http://mrdoob.com/
 */

THREE.Lensflare = function () {

	THREE.Mesh.call( this, THREE.Lensflare.Geometry, new THREE.MeshBasicMaterial( { opacity: 0, transparent: true } ) );

	this.type = 'Lensflare';
	this.frustumCulled = false;
	this.renderOrder = Infinity;

	//

	var positionScreen = new THREE.Vector3();
	var positionView = new THREE.Vector3();

	// textures

	var tempMap = new THREE.DataTexture( new Uint8Array( 16 * 16 * 3 ), 16, 16, THREE.RGBFormat );
	tempMap.minFilter = THREE.NearestFilter;
	tempMap.magFilter = THREE.NearestFilter;
	tempMap.wrapS = THREE.ClampToEdgeWrapping;
	tempMap.wrapT = THREE.ClampToEdgeWrapping;
	tempMap.needsUpdate = true;

	var occlusionMap = new THREE.DataTexture( new Uint8Array( 16 * 16 * 3 ), 16, 16, THREE.RGBFormat );
	occlusionMap.minFilter = THREE.NearestFilter;
	occlusionMap.magFilter = THREE.NearestFilter;
	occlusionMap.wrapS = THREE.ClampToEdgeWrapping;
	occlusionMap.wrapT = THREE.ClampToEdgeWrapping;
	occlusionMap.needsUpdate = true;

	// material

	var geometry = THREE.Lensflare.Geometry;

	var material1a = new THREE.RawShaderMaterial( {
		uniforms: {
			'scale': { value: null },
			'screenPosition': { value: null }
		},
		vertexShader: [

			'precision highp float;',

			'uniform vec3 screenPosition;',
			'uniform vec2 scale;',

			'attribute vec3 position;',

			'void main() {',

			'	gl_Position = vec4( position.xy * scale + screenPosition.xy, screenPosition.z, 1.0 );',

			'}'

		].join( '\n' ),
		fragmentShader: [

			'precision highp float;',

			'void main() {',

			'	gl_FragColor = vec4( 1.0, 0.0, 1.0, 1.0 );',

			'}'

		].join( '\n' ),
		depthTest: true,
		depthWrite: false,
		transparent: false
	} );

	var material1b = new THREE.RawShaderMaterial( {
		uniforms: {
			'map': { value: tempMap },
			'scale': { value: null },
			'screenPosition': { value: null }
		},
		vertexShader: [

			'precision highp float;',

			'uniform vec3 screenPosition;',
			'uniform vec2 scale;',

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

			'varying vec2 vUV;',

			'void main() {',

			'	vUV = uv;',

			'	gl_Position = vec4( position.xy * scale + screenPosition.xy, screenPosition.z, 1.0 );',

			'}'

		].join( '\n' ),
		fragmentShader: [

			'precision highp float;',

			'uniform sampler2D map;',

			'varying vec2 vUV;',

			'void main() {',

			'	gl_FragColor = texture2D( map, vUV );',

			'}'

		].join( '\n' ),
		depthTest: false,
		depthWrite: false,
		transparent: false
	} );

	// the following object is used for occlusionMap generation

	var mesh1 = new THREE.Mesh( geometry, material1a );

	//

	var elements = [];

	var shader = THREE.LensflareElement.Shader;

	var material2 = new THREE.RawShaderMaterial( {
		uniforms: {
			'map': { value: null },
			'occlusionMap': { value: occlusionMap },
			'color': { value: new THREE.Color( 0xffffff ) },
			'scale': { value: new THREE.Vector2() },
			'screenPosition': { value: new THREE.Vector3() }
		},
		vertexShader: shader.vertexShader,
		fragmentShader: shader.fragmentShader,
		blending: THREE.AdditiveBlending,
		transparent: true,
		depthWrite: false
	} );

	var mesh2 = new THREE.Mesh( geometry, material2 );

	this.addElement = function ( element ) {

		elements.push( element );

	};

	//

	var scale = new THREE.Vector2();
	var screenPositionPixels = new THREE.Vector2();
	var validArea = new THREE.Box2();
	var viewport = new THREE.Vector4();

	this.onBeforeRender = function ( renderer, scene, camera ) {

		renderer.getCurrentViewport( viewport );

		var invAspect = viewport.w / viewport.z;
		var halfViewportWidth = viewport.z / 2.0;
		var halfViewportHeight = viewport.w / 2.0;

		var size = 16 / viewport.w;
		scale.set( size * invAspect, size );

		validArea.min.set( viewport.x, viewport.y );
		validArea.max.set( viewport.x + ( viewport.z - 16 ), viewport.y + ( viewport.w - 16 ) );

		// calculate position in screen space

		positionView.setFromMatrixPosition( this.matrixWorld );
		positionView.applyMatrix4( camera.matrixWorldInverse );

		if ( positionView.z > 0 ) return; // lensflare is behind the camera

		positionScreen.copy( positionView ).applyMatrix4( camera.projectionMatrix );

		// horizontal and vertical coordinate of the lower left corner of the pixels to copy

		screenPositionPixels.x = viewport.x + ( positionScreen.x * halfViewportWidth ) + halfViewportWidth - 8;
		screenPositionPixels.y = viewport.y + ( positionScreen.y * halfViewportHeight ) + halfViewportHeight - 8;

		// screen cull

		if ( validArea.containsPoint( screenPositionPixels ) ) {

			// save current RGB to temp texture

			renderer.copyFramebufferToTexture( screenPositionPixels, tempMap );

			// render pink quad

			var uniforms = material1a.uniforms;
			uniforms[ "scale" ].value = scale;
			uniforms[ "screenPosition" ].value = positionScreen;

			renderer.renderBufferDirect( camera, null, geometry, material1a, mesh1, null );

			// copy result to occlusionMap

			renderer.copyFramebufferToTexture( screenPositionPixels, occlusionMap );

			// restore graphics

			var uniforms = material1b.uniforms;
			uniforms[ "scale" ].value = scale;
			uniforms[ "screenPosition" ].value = positionScreen;

			renderer.renderBufferDirect( camera, null, geometry, material1b, mesh1, null );

			// render elements

			var vecX = - positionScreen.x * 2;
			var vecY = - positionScreen.y * 2;

			for ( var i = 0, l = elements.length; i < l; i ++ ) {

				var element = elements[ i ];

				var uniforms = material2.uniforms;

				uniforms[ "color" ].value.copy( element.color );
				uniforms[ "map" ].value = element.texture;
				uniforms[ "screenPosition" ].value.x = positionScreen.x + vecX * element.distance;
				uniforms[ "screenPosition" ].value.y = positionScreen.y + vecY * element.distance;

				var size = element.size / viewport.w;
				var invAspect = viewport.w / viewport.z;

				uniforms[ "scale" ].value.set( size * invAspect, size );

				material2.uniformsNeedUpdate = true;

				renderer.renderBufferDirect( camera, null, geometry, material2, mesh2, null );

			}

		}

	};

	this.dispose = function () {

		material1a.dispose();
		material1b.dispose();
		material2.dispose();

		tempMap.dispose();
		occlusionMap.dispose();

		for ( var i = 0, l = elements.length; i < l; i ++ ) {

			elements[ i ].texture.dispose();

		}

	};

};

THREE.Lensflare.prototype = Object.create( THREE.Mesh.prototype );
THREE.Lensflare.prototype.constructor = THREE.Lensflare;
THREE.Lensflare.prototype.isLensflare = true;

//

THREE.LensflareElement = function ( texture, size, distance, color ) {

	this.texture = texture;
	this.size = size || 1;
	this.distance = distance || 0;
	this.color = color || new THREE.Color( 0xffffff );

};

THREE.LensflareElement.Shader = {

	uniforms: {

		'map': { value: null },
		'occlusionMap': { value: null },
		'color': { value: null },
		'scale': { value: null },
		'screenPosition': { value: null }

	},

	vertexShader: [

		'precision highp float;',

		'uniform vec3 screenPosition;',
		'uniform vec2 scale;',

		'uniform sampler2D occlusionMap;',

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

		'varying vec2 vUV;',
		'varying float vVisibility;',

		'void main() {',

		'	vUV = uv;',

		'	vec2 pos = position.xy;',

		'	vec4 visibility = texture2D( occlusionMap, vec2( 0.1, 0.1 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.5, 0.1 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.9, 0.1 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.9, 0.5 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.9, 0.9 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.5, 0.9 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.1, 0.9 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.1, 0.5 ) );',
		'	visibility += texture2D( occlusionMap, vec2( 0.5, 0.5 ) );',

		'	vVisibility =        visibility.r / 9.0;',
		'	vVisibility *= 1.0 - visibility.g / 9.0;',
		'	vVisibility *=       visibility.b / 9.0;',

		'	gl_Position = vec4( ( pos * scale + screenPosition.xy ).xy, screenPosition.z, 1.0 );',

		'}'

	].join( '\n' ),

	fragmentShader: [

		'precision highp float;',

		'uniform sampler2D map;',
		'uniform vec3 color;',

		'varying vec2 vUV;',
		'varying float vVisibility;',

		'void main() {',

		'	vec4 texture = texture2D( map, vUV );',
		'	texture.a *= vVisibility;',
		'	gl_FragColor = texture;',
		'	gl_FragColor.rgb *= color;',

		'}'

	].join( '\n' )

};

THREE.Lensflare.Geometry = ( function () {

	var geometry = new THREE.BufferGeometry();

	var float32Array = new Float32Array( [
		- 1, - 1, 0, 0, 0,
		1, - 1, 0, 1, 0,
		1, 1, 0, 1, 1,
		- 1, 1, 0, 0, 1
	] );

	var interleavedBuffer = new THREE.InterleavedBuffer( float32Array, 5 );

	geometry.setIndex( [ 0, 1, 2,	0, 2, 3 ] );
	geometry.addAttribute( 'position', new THREE.InterleavedBufferAttribute( interleavedBuffer, 3, 0, false ) );
	geometry.addAttribute( 'uv', new THREE.InterleavedBufferAttribute( interleavedBuffer, 2, 3, false ) );

	return geometry;

} )();
