/**
 * TODO
 */

import {
	Vector2
} from "../../../build/three.module.js";

var DepthLimitedBlurShader = {
	defines: {
		"KERNEL_RADIUS": 4,
		"DEPTH_PACKING": 1,
		"PERSPECTIVE_CAMERA": 1
	},
	uniforms: {
		"tDiffuse": { value: null },
		"size": { value: new Vector2( 512, 512 ) },
		"sampleUvOffsets": { value: [ new Vector2( 0, 0 ) ] },
		"sampleWeights": { value: [ 1.0 ] },
		"tDepth": { value: null },
		"cameraNear": { value: 10 },
		"cameraFar": { value: 1000 },
		"depthCutoff": { value: 10 },
	},
	vertexShader: [
		"#include <common>",

		"uniform vec2 size;",

		"varying vec2 vUv;",
		"varying vec2 vInvSize;",

		"void main() {",
		"	vUv = uv;",
		"	vInvSize = 1.0 / size;",

		"	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );",
		"}"

	].join( "\n" ),
	fragmentShader: [
		"#include <common>",
		"#include <packing>",

		"uniform sampler2D tDiffuse;",
		"uniform sampler2D tDepth;",

		"uniform float cameraNear;",
		"uniform float cameraFar;",
		"uniform float depthCutoff;",

		"uniform vec2 sampleUvOffsets[ KERNEL_RADIUS + 1 ];",
		"uniform float sampleWeights[ KERNEL_RADIUS + 1 ];",

		"varying vec2 vUv;",
		"varying vec2 vInvSize;",

		"float getDepth( const in vec2 screenPosition ) {",
		"	#if DEPTH_PACKING == 1",
		"	return unpackRGBAToDepth( texture2D( tDepth, screenPosition ) );",
		"	#else",
		"	return texture2D( tDepth, screenPosition ).x;",
		"	#endif",
		"}",

		"float getViewZ( const in float depth ) {",
		"	#if PERSPECTIVE_CAMERA == 1",
		"	return perspectiveDepthToViewZ( depth, cameraNear, cameraFar );",
		"	#else",
		"	return orthographicDepthToViewZ( depth, cameraNear, cameraFar );",
		"	#endif",
		"}",

		"void main() {",
		"	float depth = getDepth( vUv );",
		"	if( depth >= ( 1.0 - EPSILON ) ) {",
		"		discard;",
		"	}",

		"	float centerViewZ = -getViewZ( depth );",
		"	bool rBreak = false, lBreak = false;",

		"	float weightSum = sampleWeights[0];",
		"	vec4 diffuseSum = texture2D( tDiffuse, vUv ) * weightSum;",

		"	for( int i = 1; i <= KERNEL_RADIUS; i ++ ) {",

		"		float sampleWeight = sampleWeights[i];",
		"		vec2 sampleUvOffset = sampleUvOffsets[i] * vInvSize;",

		"		vec2 sampleUv = vUv + sampleUvOffset;",
		"		float viewZ = -getViewZ( getDepth( sampleUv ) );",

		"		if( abs( viewZ - centerViewZ ) > depthCutoff ) rBreak = true;",

		"		if( ! rBreak ) {",
		"			diffuseSum += texture2D( tDiffuse, sampleUv ) * sampleWeight;",
		"			weightSum += sampleWeight;",
		"		}",

		"		sampleUv = vUv - sampleUvOffset;",
		"		viewZ = -getViewZ( getDepth( sampleUv ) );",

		"		if( abs( viewZ - centerViewZ ) > depthCutoff ) lBreak = true;",

		"		if( ! lBreak ) {",
		"			diffuseSum += texture2D( tDiffuse, sampleUv ) * sampleWeight;",
		"			weightSum += sampleWeight;",
		"		}",

		"	}",

		"	gl_FragColor = diffuseSum / weightSum;",
		"}"
	].join( "\n" )
};

var BlurShaderUtils = {

	createSampleWeights: function ( kernelRadius, stdDev ) {

		var gaussian = function ( x, stdDev ) {

			return Math.exp( - ( x * x ) / ( 2.0 * ( stdDev * stdDev ) ) ) / ( Math.sqrt( 2.0 * Math.PI ) * stdDev );

		};

		var weights = [];

		for ( var i = 0; i <= kernelRadius; i ++ ) {

			weights.push( gaussian( i, stdDev ) );

		}

		return weights;

	},

	createSampleOffsets: function ( kernelRadius, uvIncrement ) {

		var offsets = [];

		for ( var i = 0; i <= kernelRadius; i ++ ) {

			offsets.push( uvIncrement.clone().multiplyScalar( i ) );

		}

		return offsets;

	},

	configure: function ( material, kernelRadius, stdDev, uvIncrement ) {

		material.defines[ "KERNEL_RADIUS" ] = kernelRadius;
		material.uniforms[ "sampleUvOffsets" ].value = BlurShaderUtils.createSampleOffsets( kernelRadius, uvIncrement );
		material.uniforms[ "sampleWeights" ].value = BlurShaderUtils.createSampleWeights( kernelRadius, stdDev );
		material.needsUpdate = true;

	}

};

export { DepthLimitedBlurShader, BlurShaderUtils };
