/**
 * @author mpk / http://polko.me/
 *
 * WebGL port of Subpixel Morphological Antialiasing (SMAA) v2.8
 * Preset: SMAA 1x Medium (with color edge detection)
 * https://github.com/iryoku/smaa/releases/tag/v2.8
 */

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

var SMAAEdgesShader = {

	defines: {

		"SMAA_THRESHOLD": "0.1"

	},

	uniforms: {

		"tDiffuse": { value: null },
		"resolution": { value: new Vector2( 1 / 1024, 1 / 512 ) }

	},

	vertexShader: [

		"uniform vec2 resolution;",

		"varying vec2 vUv;",
		"varying vec4 vOffset[ 3 ];",

		"void SMAAEdgeDetectionVS( vec2 texcoord ) {",
			"vOffset[ 0 ] = texcoord.xyxy + resolution.xyxy * vec4( -1.0, 0.0, 0.0,  1.0 );", // WebGL port note: Changed sign in W component
			"vOffset[ 1 ] = texcoord.xyxy + resolution.xyxy * vec4(  1.0, 0.0, 0.0, -1.0 );", // WebGL port note: Changed sign in W component
			"vOffset[ 2 ] = texcoord.xyxy + resolution.xyxy * vec4( -2.0, 0.0, 0.0,  2.0 );", // WebGL port note: Changed sign in W component
		"}",

		"void main() {",

			"vUv = uv;",

			"SMAAEdgeDetectionVS( vUv );",

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

		"}"

	].join( "\n" ),

	fragmentShader: [

		"uniform sampler2D tDiffuse;",

		"varying vec2 vUv;",
		"varying vec4 vOffset[ 3 ];",

		"vec4 SMAAColorEdgeDetectionPS( vec2 texcoord, vec4 offset[3], sampler2D colorTex ) {",
			"vec2 threshold = vec2( SMAA_THRESHOLD, SMAA_THRESHOLD );",

			// Calculate color deltas:
			"vec4 delta;",
			"vec3 C = texture2D( colorTex, texcoord ).rgb;",

			"vec3 Cleft = texture2D( colorTex, offset[0].xy ).rgb;",
			"vec3 t = abs( C - Cleft );",
			"delta.x = max( max( t.r, t.g ), t.b );",

			"vec3 Ctop = texture2D( colorTex, offset[0].zw ).rgb;",
			"t = abs( C - Ctop );",
			"delta.y = max( max( t.r, t.g ), t.b );",

			// We do the usual threshold:
			"vec2 edges = step( threshold, delta.xy );",

			// Then discard if there is no edge:
			"if ( dot( edges, vec2( 1.0, 1.0 ) ) == 0.0 )",
				"discard;",

			// Calculate right and bottom deltas:
			"vec3 Cright = texture2D( colorTex, offset[1].xy ).rgb;",
			"t = abs( C - Cright );",
			"delta.z = max( max( t.r, t.g ), t.b );",

			"vec3 Cbottom  = texture2D( colorTex, offset[1].zw ).rgb;",
			"t = abs( C - Cbottom );",
			"delta.w = max( max( t.r, t.g ), t.b );",

			// Calculate the maximum delta in the direct neighborhood:
			"float maxDelta = max( max( max( delta.x, delta.y ), delta.z ), delta.w );",

			// Calculate left-left and top-top deltas:
			"vec3 Cleftleft  = texture2D( colorTex, offset[2].xy ).rgb;",
			"t = abs( C - Cleftleft );",
			"delta.z = max( max( t.r, t.g ), t.b );",

			"vec3 Ctoptop = texture2D( colorTex, offset[2].zw ).rgb;",
			"t = abs( C - Ctoptop );",
			"delta.w = max( max( t.r, t.g ), t.b );",

			// Calculate the final maximum delta:
			"maxDelta = max( max( maxDelta, delta.z ), delta.w );",

			// Local contrast adaptation in action:
			"edges.xy *= step( 0.5 * maxDelta, delta.xy );",

			"return vec4( edges, 0.0, 0.0 );",
		"}",

		"void main() {",

			"gl_FragColor = SMAAColorEdgeDetectionPS( vUv, vOffset, tDiffuse );",

		"}"

	].join( "\n" )

};

var SMAAWeightsShader = {

	defines: {

		"SMAA_MAX_SEARCH_STEPS": "8",
		"SMAA_AREATEX_MAX_DISTANCE": "16",
		"SMAA_AREATEX_PIXEL_SIZE": "( 1.0 / vec2( 160.0, 560.0 ) )",
		"SMAA_AREATEX_SUBTEX_SIZE": "( 1.0 / 7.0 )"

	},

	uniforms: {

		"tDiffuse": { value: null },
		"tArea": { value: null },
		"tSearch": { value: null },
		"resolution": { value: new Vector2( 1 / 1024, 1 / 512 ) }

	},

	vertexShader: [

		"uniform vec2 resolution;",

		"varying vec2 vUv;",
		"varying vec4 vOffset[ 3 ];",
		"varying vec2 vPixcoord;",

		"void SMAABlendingWeightCalculationVS( vec2 texcoord ) {",
			"vPixcoord = texcoord / resolution;",

			// We will use these offsets for the searches later on (see @PSEUDO_GATHER4):
			"vOffset[ 0 ] = texcoord.xyxy + resolution.xyxy * vec4( -0.25, 0.125, 1.25, 0.125 );", // WebGL port note: Changed sign in Y and W components
			"vOffset[ 1 ] = texcoord.xyxy + resolution.xyxy * vec4( -0.125, 0.25, -0.125, -1.25 );", // WebGL port note: Changed sign in Y and W components

			// And these for the searches, they indicate the ends of the loops:
			"vOffset[ 2 ] = vec4( vOffset[ 0 ].xz, vOffset[ 1 ].yw ) + vec4( -2.0, 2.0, -2.0, 2.0 ) * resolution.xxyy * float( SMAA_MAX_SEARCH_STEPS );",

		"}",

		"void main() {",

			"vUv = uv;",

			"SMAABlendingWeightCalculationVS( vUv );",

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

		"}"

	].join( "\n" ),

	fragmentShader: [

		"#define SMAASampleLevelZeroOffset( tex, coord, offset ) texture2D( tex, coord + float( offset ) * resolution, 0.0 )",

		"uniform sampler2D tDiffuse;",
		"uniform sampler2D tArea;",
		"uniform sampler2D tSearch;",
		"uniform vec2 resolution;",

		"varying vec2 vUv;",
		"varying vec4 vOffset[3];",
		"varying vec2 vPixcoord;",

		"#if __VERSION__ == 100",
		"vec2 round( vec2 x ) {",
			"return sign( x ) * floor( abs( x ) + 0.5 );",
		"}",
		"#endif",

		"float SMAASearchLength( sampler2D searchTex, vec2 e, float bias, float scale ) {",
			// Not required if searchTex accesses are set to point:
			// float2 SEARCH_TEX_PIXEL_SIZE = 1.0 / float2(66.0, 33.0);
			// e = float2(bias, 0.0) + 0.5 * SEARCH_TEX_PIXEL_SIZE +
			//     e * float2(scale, 1.0) * float2(64.0, 32.0) * SEARCH_TEX_PIXEL_SIZE;
			"e.r = bias + e.r * scale;",
			"return 255.0 * texture2D( searchTex, e, 0.0 ).r;",
		"}",

		"float SMAASearchXLeft( sampler2D edgesTex, sampler2D searchTex, vec2 texcoord, float end ) {",
			/**
			* @PSEUDO_GATHER4
			* This texcoord has been offset by (-0.25, -0.125) in the vertex shader to
			* sample between edge, thus fetching four edges in a row.
			* Sampling with different offsets in each direction allows to disambiguate
			* which edges are active from the four fetched ones.
			*/
			"vec2 e = vec2( 0.0, 1.0 );",

			"for ( int i = 0; i < SMAA_MAX_SEARCH_STEPS; i ++ ) {", // WebGL port note: Changed while to for
				"e = texture2D( edgesTex, texcoord, 0.0 ).rg;",
				"texcoord -= vec2( 2.0, 0.0 ) * resolution;",
				"if ( ! ( texcoord.x > end && e.g > 0.8281 && e.r == 0.0 ) ) break;",
			"}",

			// We correct the previous (-0.25, -0.125) offset we applied:
			"texcoord.x += 0.25 * resolution.x;",

			// The searches are bias by 1, so adjust the coords accordingly:
			"texcoord.x += resolution.x;",

			// Disambiguate the length added by the last step:
			"texcoord.x += 2.0 * resolution.x;", // Undo last step
			"texcoord.x -= resolution.x * SMAASearchLength(searchTex, e, 0.0, 0.5);",

			"return texcoord.x;",
		"}",

		"float SMAASearchXRight( sampler2D edgesTex, sampler2D searchTex, vec2 texcoord, float end ) {",
			"vec2 e = vec2( 0.0, 1.0 );",

			"for ( int i = 0; i < SMAA_MAX_SEARCH_STEPS; i ++ ) {", // WebGL port note: Changed while to for
				"e = texture2D( edgesTex, texcoord, 0.0 ).rg;",
				"texcoord += vec2( 2.0, 0.0 ) * resolution;",
				"if ( ! ( texcoord.x < end && e.g > 0.8281 && e.r == 0.0 ) ) break;",
			"}",

			"texcoord.x -= 0.25 * resolution.x;",
			"texcoord.x -= resolution.x;",
			"texcoord.x -= 2.0 * resolution.x;",
			"texcoord.x += resolution.x * SMAASearchLength( searchTex, e, 0.5, 0.5 );",

			"return texcoord.x;",
		"}",

		"float SMAASearchYUp( sampler2D edgesTex, sampler2D searchTex, vec2 texcoord, float end ) {",
			"vec2 e = vec2( 1.0, 0.0 );",

			"for ( int i = 0; i < SMAA_MAX_SEARCH_STEPS; i ++ ) {", // WebGL port note: Changed while to for
				"e = texture2D( edgesTex, texcoord, 0.0 ).rg;",
				"texcoord += vec2( 0.0, 2.0 ) * resolution;", // WebGL port note: Changed sign
				"if ( ! ( texcoord.y > end && e.r > 0.8281 && e.g == 0.0 ) ) break;",
			"}",

			"texcoord.y -= 0.25 * resolution.y;", // WebGL port note: Changed sign
			"texcoord.y -= resolution.y;", // WebGL port note: Changed sign
			"texcoord.y -= 2.0 * resolution.y;", // WebGL port note: Changed sign
			"texcoord.y += resolution.y * SMAASearchLength( searchTex, e.gr, 0.0, 0.5 );", // WebGL port note: Changed sign

			"return texcoord.y;",
		"}",

		"float SMAASearchYDown( sampler2D edgesTex, sampler2D searchTex, vec2 texcoord, float end ) {",
			"vec2 e = vec2( 1.0, 0.0 );",

			"for ( int i = 0; i < SMAA_MAX_SEARCH_STEPS; i ++ ) {", // WebGL port note: Changed while to for
				"e = texture2D( edgesTex, texcoord, 0.0 ).rg;",
				"texcoord -= vec2( 0.0, 2.0 ) * resolution;", // WebGL port note: Changed sign
				"if ( ! ( texcoord.y < end && e.r > 0.8281 && e.g == 0.0 ) ) break;",
			"}",

			"texcoord.y += 0.25 * resolution.y;", // WebGL port note: Changed sign
			"texcoord.y += resolution.y;", // WebGL port note: Changed sign
			"texcoord.y += 2.0 * resolution.y;", // WebGL port note: Changed sign
			"texcoord.y -= resolution.y * SMAASearchLength( searchTex, e.gr, 0.5, 0.5 );", // WebGL port note: Changed sign

			"return texcoord.y;",
		"}",

		"vec2 SMAAArea( sampler2D areaTex, vec2 dist, float e1, float e2, float offset ) {",
			// Rounding prevents precision errors of bilinear filtering:
			"vec2 texcoord = float( SMAA_AREATEX_MAX_DISTANCE ) * round( 4.0 * vec2( e1, e2 ) ) + dist;",

			// We do a scale and bias for mapping to texel space:
			"texcoord = SMAA_AREATEX_PIXEL_SIZE * texcoord + ( 0.5 * SMAA_AREATEX_PIXEL_SIZE );",

			// Move to proper place, according to the subpixel offset:
			"texcoord.y += SMAA_AREATEX_SUBTEX_SIZE * offset;",

			"return texture2D( areaTex, texcoord, 0.0 ).rg;",
		"}",

		"vec4 SMAABlendingWeightCalculationPS( vec2 texcoord, vec2 pixcoord, vec4 offset[ 3 ], sampler2D edgesTex, sampler2D areaTex, sampler2D searchTex, ivec4 subsampleIndices ) {",
			"vec4 weights = vec4( 0.0, 0.0, 0.0, 0.0 );",

			"vec2 e = texture2D( edgesTex, texcoord ).rg;",

			"if ( e.g > 0.0 ) {", // Edge at north
				"vec2 d;",

				// Find the distance to the left:
				"vec2 coords;",
				"coords.x = SMAASearchXLeft( edgesTex, searchTex, offset[ 0 ].xy, offset[ 2 ].x );",
				"coords.y = offset[ 1 ].y;", // offset[1].y = texcoord.y - 0.25 * resolution.y (@CROSSING_OFFSET)
				"d.x = coords.x;",

				// Now fetch the left crossing edges, two at a time using bilinear
				// filtering. Sampling at -0.25 (see @CROSSING_OFFSET) enables to
				// discern what value each edge has:
				"float e1 = texture2D( edgesTex, coords, 0.0 ).r;",

				// Find the distance to the right:
				"coords.x = SMAASearchXRight( edgesTex, searchTex, offset[ 0 ].zw, offset[ 2 ].y );",
				"d.y = coords.x;",

				// We want the distances to be in pixel units (doing this here allow to
				// better interleave arithmetic and memory accesses):
				"d = d / resolution.x - pixcoord.x;",

				// SMAAArea below needs a sqrt, as the areas texture is compressed
				// quadratically:
				"vec2 sqrt_d = sqrt( abs( d ) );",

				// Fetch the right crossing edges:
				"coords.y -= 1.0 * resolution.y;", // WebGL port note: Added
				"float e2 = SMAASampleLevelZeroOffset( edgesTex, coords, ivec2( 1, 0 ) ).r;",

				// Ok, we know how this pattern looks like, now it is time for getting
				// the actual area:
				"weights.rg = SMAAArea( areaTex, sqrt_d, e1, e2, float( subsampleIndices.y ) );",
			"}",

			"if ( e.r > 0.0 ) {", // Edge at west
				"vec2 d;",

				// Find the distance to the top:
				"vec2 coords;",

				"coords.y = SMAASearchYUp( edgesTex, searchTex, offset[ 1 ].xy, offset[ 2 ].z );",
				"coords.x = offset[ 0 ].x;", // offset[1].x = texcoord.x - 0.25 * resolution.x;
				"d.x = coords.y;",

				// Fetch the top crossing edges:
				"float e1 = texture2D( edgesTex, coords, 0.0 ).g;",

				// Find the distance to the bottom:
				"coords.y = SMAASearchYDown( edgesTex, searchTex, offset[ 1 ].zw, offset[ 2 ].w );",
				"d.y = coords.y;",

				// We want the distances to be in pixel units:
				"d = d / resolution.y - pixcoord.y;",

				// SMAAArea below needs a sqrt, as the areas texture is compressed
				// quadratically:
				"vec2 sqrt_d = sqrt( abs( d ) );",

				// Fetch the bottom crossing edges:
				"coords.y -= 1.0 * resolution.y;", // WebGL port note: Added
				"float e2 = SMAASampleLevelZeroOffset( edgesTex, coords, ivec2( 0, 1 ) ).g;",

				// Get the area for this direction:
				"weights.ba = SMAAArea( areaTex, sqrt_d, e1, e2, float( subsampleIndices.x ) );",
			"}",

			"return weights;",
		"}",

		"void main() {",

			"gl_FragColor = SMAABlendingWeightCalculationPS( vUv, vPixcoord, vOffset, tDiffuse, tArea, tSearch, ivec4( 0.0 ) );",

		"}"

	].join( "\n" )

};

var SMAABlendShader = {

	uniforms: {

		"tDiffuse": { value: null },
		"tColor": { value: null },
		"resolution": { value: new Vector2( 1 / 1024, 1 / 512 ) }

	},

	vertexShader: [

		"uniform vec2 resolution;",

		"varying vec2 vUv;",
		"varying vec4 vOffset[ 2 ];",

		"void SMAANeighborhoodBlendingVS( vec2 texcoord ) {",
			"vOffset[ 0 ] = texcoord.xyxy + resolution.xyxy * vec4( -1.0, 0.0, 0.0, 1.0 );", // WebGL port note: Changed sign in W component
			"vOffset[ 1 ] = texcoord.xyxy + resolution.xyxy * vec4( 1.0, 0.0, 0.0, -1.0 );", // WebGL port note: Changed sign in W component
		"}",

		"void main() {",

			"vUv = uv;",

			"SMAANeighborhoodBlendingVS( vUv );",

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

		"}"

	].join( "\n" ),

	fragmentShader: [

		"uniform sampler2D tDiffuse;",
		"uniform sampler2D tColor;",
		"uniform vec2 resolution;",

		"varying vec2 vUv;",
		"varying vec4 vOffset[ 2 ];",

		"vec4 SMAANeighborhoodBlendingPS( vec2 texcoord, vec4 offset[ 2 ], sampler2D colorTex, sampler2D blendTex ) {",
			// Fetch the blending weights for current pixel:
			"vec4 a;",
			"a.xz = texture2D( blendTex, texcoord ).xz;",
			"a.y = texture2D( blendTex, offset[ 1 ].zw ).g;",
			"a.w = texture2D( blendTex, offset[ 1 ].xy ).a;",

			// Is there any blending weight with a value greater than 0.0?
			"if ( dot(a, vec4( 1.0, 1.0, 1.0, 1.0 )) < 1e-5 ) {",
				"return texture2D( colorTex, texcoord, 0.0 );",
			"} else {",
				// Up to 4 lines can be crossing a pixel (one through each edge). We
				// favor blending by choosing the line with the maximum weight for each
				// direction:
				"vec2 offset;",
				"offset.x = a.a > a.b ? a.a : -a.b;", // left vs. right
				"offset.y = a.g > a.r ? -a.g : a.r;", // top vs. bottom // WebGL port note: Changed signs

				// Then we go in the direction that has the maximum weight:
				"if ( abs( offset.x ) > abs( offset.y )) {", // horizontal vs. vertical
					"offset.y = 0.0;",
				"} else {",
					"offset.x = 0.0;",
				"}",

				// Fetch the opposite color and lerp by hand:
				"vec4 C = texture2D( colorTex, texcoord, 0.0 );",
				"texcoord += sign( offset ) * resolution;",
				"vec4 Cop = texture2D( colorTex, texcoord, 0.0 );",
				"float s = abs( offset.x ) > abs( offset.y ) ? abs( offset.x ) : abs( offset.y );",

				// WebGL port note: Added gamma correction
				"C.xyz = pow(C.xyz, vec3(2.2));",
				"Cop.xyz = pow(Cop.xyz, vec3(2.2));",
				"vec4 mixed = mix(C, Cop, s);",
				"mixed.xyz = pow(mixed.xyz, vec3(1.0 / 2.2));",

				"return mixed;",
			"}",
		"}",

		"void main() {",

			"gl_FragColor = SMAANeighborhoodBlendingPS( vUv, vOffset, tColor, tDiffuse );",

		"}"

	].join( "\n" )

};

export { SMAAEdgesShader, SMAAWeightsShader, SMAABlendShader };