// Fragment shader

// Uniforms
uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;
uniform vec4 u_colors[2];
uniform float u_intensity;
uniform float u_rays;
uniform float u_reach;

#ifndef FNC_MOD289
#define FNC_MOD289
float mod289(const in float x) { return x - floor(x * (1. / 289.)) * 289.; }
vec2 mod289(const in vec2 x) { return x - floor(x * (1. / 289.)) * 289.; }
vec3 mod289(const in vec3 x) { return x - floor(x * (1. / 289.)) * 289.; }
vec4 mod289(const in vec4 x) { return x - floor(x * (1. / 289.)) * 289.; }
#endif

#ifndef FNC_PERMUTE
#define FNC_PERMUTE
float permute(const in float x) { return mod289(((x * 34.0) + 1.0) * x); }
vec2 permute(const in vec2 x) { return mod289(((x * 34.0) + 1.0) * x); }
vec3 permute(const in vec3 x) { return mod289(((x * 34.0) + 1.0) * x); }
vec4 permute(const in vec4 x) { return mod289(((x * 34.0) + 1.0) * x); }
#endif

#ifndef FNC_TAYLORINVSQRT
#define FNC_TAYLORINVSQRT
float taylorInvSqrt(in float r) { return 1.79284291400159 - 0.85373472095314 * r; }
vec2 taylorInvSqrt(in vec2 r) { return 1.79284291400159 - 0.85373472095314 * r; }
vec3 taylorInvSqrt(in vec3 r) { return 1.79284291400159 - 0.85373472095314 * r; }
vec4 taylorInvSqrt(in vec4 r) { return 1.79284291400159 - 0.85373472095314 * r; }
#endif

#ifndef FNC_QUINTIC
#define FNC_QUINTIC
float quintic(const in float v) { return v*v*v*(v*(v*6.0-15.0)+10.0); }
vec2  quintic(const in vec2 v)  { return v*v*v*(v*(v*6.0-15.0)+10.0); }
vec3  quintic(const in vec3 v)  { return v*v*v*(v*(v*6.0-15.0)+10.0); }
vec4  quintic(const in vec4 v)  { return v*v*v*(v*(v*6.0-15.0)+10.0); }
#endif

#ifndef FNC_PNOISE
#define FNC_PNOISE
float pnoise(in vec2 P, in vec2 rep) {
  vec4 Pi = floor(P.xyxy) + vec4(0.0, 0.0, 1.0, 1.0);
  vec4 Pf = fract(P.xyxy) - vec4(0.0, 0.0, 1.0, 1.0);
  Pi = mod(Pi, rep.xyxy); 
  Pi = mod289(Pi);        
  vec4 ix = Pi.xzxz;
  vec4 iy = Pi.yyww;
  vec4 fx = Pf.xzxz;
  vec4 fy = Pf.yyww;

  vec4 i = permute(permute(ix) + iy);

  vec4 gx = fract(i * (1.0 / 41.0)) * 2.0 - 1.0 ;
  vec4 gy = abs(gx) - 0.5 ;
  vec4 tx = floor(gx + 0.5);
  gx = gx - tx;

  vec2 g00 = vec2(gx.x,gy.x);
  vec2 g10 = vec2(gx.y,gy.y);
  vec2 g01 = vec2(gx.z,gy.z);
  vec2 g11 = vec2(gx.w,gy.w);

  vec4 norm = taylorInvSqrt(vec4(dot(g00, g00), dot(g01, g01), dot(g10, g10), dot(g11, g11)));
  g00 *= norm.x;
  g01 *= norm.y;
  g10 *= norm.z;
  g11 *= norm.w;

  float n00 = dot(g00, vec2(fx.x, fy.x));
  float n10 = dot(g10, vec2(fx.y, fy.y));
  float n01 = dot(g01, vec2(fx.z, fy.z));
  float n11 = dot(g11, vec2(fx.w, fy.w));

  vec2 fade_xy = quintic(Pf.xy);
  vec2 n_x = mix(vec2(n00, n01), vec2(n10, n11), fade_xy.x);
  float n_xy = mix(n_x.x, n_x.y, fade_xy.y);
  return 2.3 * n_xy;
}

float pnoise(in vec3 P, in vec3 rep) {
  vec3 Pi0 = mod(floor(P), rep); 
  vec3 Pi1 = mod(Pi0 + vec3(1.0), rep); 
  Pi0 = mod289(Pi0);
  Pi1 = mod289(Pi1);
  vec3 Pf0 = fract(P); 
  vec3 Pf1 = Pf0 - vec3(1.0); 
  vec4 ix = vec4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
  vec4 iy = vec4(Pi0.yy, Pi1.yy);
  vec4 iz0 = Pi0.zzzz;
  vec4 iz1 = Pi1.zzzz;

  vec4 ixy = permute(permute(ix) + iy);
  vec4 ixy0 = permute(ixy + iz0);
  vec4 ixy1 = permute(ixy + iz1);

  vec4 gx0 = ixy0 * (1.0 / 7.0);
  vec4 gy0 = fract(floor(gx0) * (1.0 / 7.0)) - 0.5;
  gx0 = fract(gx0);
  vec4 gz0 = vec4(0.5) - abs(gx0) - abs(gy0);
  vec4 sz0 = step(gz0, vec4(0.0));
  gx0 -= sz0 * (step(0.0, gx0) - 0.5);
  gy0 -= sz0 * (step(0.0, gy0) - 0.5);

  vec4 gx1 = ixy1 * (1.0 / 7.0);
  vec4 gy1 = fract(floor(gx1) * (1.0 / 7.0)) - 0.5;
  gx1 = fract(gx1);
  vec4 gz1 = vec4(0.5) - abs(gx1) - abs(gy1);
  vec4 sz1 = step(gz1, vec4(0.0));
  gx1 -= sz1 * (step(0.0, gx1) - 0.5);
  gy1 -= sz1 * (step(0.0, gy1) - 0.5);

  vec3 g000 = vec3(gx0.x,gy0.x,gz0.x);
  vec3 g100 = vec3(gx0.y,gy0.y,gz0.y);
  vec3 g010 = vec3(gx0.z,gy0.z,gz0.z);
  vec3 g110 = vec3(gx0.w,gy0.w,gz0.w);
  vec3 g001 = vec3(gx1.x,gy1.x,gz1.x);
  vec3 g101 = vec3(gx1.y,gy1.y,gz1.y);
  vec3 g011 = vec3(gx1.z,gy1.z,gz1.z);
  vec3 g111 = vec3(gx1.w,gy1.w,gz1.w);

  vec4 norm0 = taylorInvSqrt(vec4(dot(g000, g000), dot(g010, g010), dot(g100, g100), dot(g110, g110)));
  g000 *= norm0.x;
  g010 *= norm0.y;
  g100 *= norm0.z;
  g110 *= norm0.w;
  vec4 norm1 = taylorInvSqrt(vec4(dot(g001, g001), dot(g011, g011), dot(g101, g101), dot(g111, g111)));
  g001 *= norm1.x;
  g011 *= norm1.y;
  g101 *= norm1.z;
  g111 *= norm1.w;

  float n000 = dot(g000, Pf0);
  float n100 = dot(g100, vec3(Pf1.x, Pf0.yz));
  float n010 = dot(g010, vec3(Pf0.x, Pf1.y, Pf0.z));
  float n110 = dot(g110, vec3(Pf1.xy, Pf0.z));
  float n001 = dot(g001, vec3(Pf0.xy, Pf1.z));
  float n101 = dot(g101, vec3(Pf1.x, Pf0.y, Pf1.z));
  float n011 = dot(g011, vec3(Pf0.x, Pf1.yz));
  float n111 = dot(g111, Pf1);

  vec3 fade_xyz = quintic(Pf0);
  vec4 n_z = mix(vec4(n000, n100, n010, n110), vec4(n001, n101, n011, n111), fade_xyz.z);
  vec2 n_yz = mix(n_z.xy, n_z.zw, fade_xyz.y);
  float n_xyz = mix(n_yz.x, n_yz.y, fade_xyz.x);
  return 2.2 * n_xyz;
}

float pnoise(in vec4 P, in vec4 rep) {
  vec4 Pi0 = mod(floor(P), rep); 
  vec4 Pi1 = mod(Pi0 + 1.0, rep); 
  Pi0 = mod289(Pi0);
  Pi1 = mod289(Pi1);
  vec4 Pf0 = fract(P); 
  vec4 Pf1 = Pf0 - 1.0; 
  vec4 ix = vec4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
  vec4 iy = vec4(Pi0.yy, Pi1.yy);
  vec4 iz0 = vec4(Pi0.zzzz);
  vec4 iz1 = vec4(Pi1.zzzz);
  vec4 iw0 = vec4(Pi0.wwww);
  vec4 iw1 = vec4(Pi1.wwww);

  vec4 ixy = permute(permute(ix) + iy);
  vec4 ixy0 = permute(ixy + iz0);
  vec4 ixy1 = permute(ixy + iz1);
  vec4 ixy00 = permute(ixy0 + iw0);
  vec4 ixy01 = permute(ixy0 + iw1);
  vec4 ixy10 = permute(ixy1 + iw0);
  vec4 ixy11 = permute(ixy1 + iw1);

  vec4 gx00 = ixy00 * (1.0 / 7.0);
  vec4 gy00 = floor(gx00) * (1.0 / 7.0);
  vec4 gz00 = floor(gy00) * (1.0 / 6.0);
  gx00 = fract(gx00) - 0.5;
  gy00 = fract(gy00) - 0.5;
  gz00 = fract(gz00) - 0.5;
  vec4 gw00 = vec4(0.75) - abs(gx00) - abs(gy00) - abs(gz00);
  vec4 sw00 = step(gw00, vec4(0.0));
  gx00 -= sw00 * (step(0.0, gx00) - 0.5);
  gy00 -= sw00 * (step(0.0, gy00) - 0.5);

  vec4 gx01 = ixy01 * (1.0 / 7.0);
  vec4 gy01 = floor(gx01) * (1.0 / 7.0);
  vec4 gz01 = floor(gy01) * (1.0 / 6.0);
  gx01 = fract(gx01) - 0.5;
  gy01 = fract(gy01) - 0.5;
  gz01 = fract(gz01) - 0.5;
  vec4 gw01 = vec4(0.75) - abs(gx01) - abs(gy01) - abs(gz01);
  vec4 sw01 = step(gw01, vec4(0.0));
  gx01 -= sw01 * (step(0.0, gx01) - 0.5);
  gy01 -= sw01 * (step(0.0, gy01) - 0.5);

  vec4 gx10 = ixy10 * (1.0 / 7.0);
  vec4 gy10 = floor(gx10) * (1.0 / 7.0);
  vec4 gz10 = floor(gy10) * (1.0 / 6.0);
  gx10 = fract(gx10) - 0.5;
  gy10 = fract(gy10) - 0.5;
  gz10 = fract(gz10) - 0.5;
  vec4 gw10 = vec4(0.75) - abs(gx10) - abs(gy10) - abs(gz10);
  vec4 sw10 = step(gw10, vec4(0.0));
  gx10 -= sw10 * (step(0.0, gx10) - 0.5);
  gy10 -= sw10 * (step(0.0, gy10) - 0.5);

  vec4 gx11 = ixy11 * (1.0 / 7.0);
  vec4 gy11 = floor(gx11) * (1.0 / 7.0);
  vec4 gz11 = floor(gy11) * (1.0 / 6.0);
  gx11 = fract(gx11) - 0.5;
  gy11 = fract(gy11) - 0.5;
  gz11 = fract(gz11) - 0.5;
  vec4 gw11 = vec4(0.75) - abs(gx11) - abs(gy11) - abs(gz11);
  vec4 sw11 = step(gw11, vec4(0.0));
  gx11 -= sw11 * (step(0.0, gx11) - 0.5);
  gy11 -= sw11 * (step(0.0, gy11) - 0.5);

  vec4 g0000 = vec4(gx00.x,gy00.x,gz00.x,gw00.x);
  vec4 g1000 = vec4(gx00.y,gy00.y,gz00.y,gw00.y);
  vec4 g0100 = vec4(gx00.z,gy00.z,gz00.z,gw00.z);
  vec4 g1100 = vec4(gx00.w,gy00.w,gz00.w,gw00.w);
  vec4 g0010 = vec4(gx10.x,gy10.x,gz10.x,gw10.x);
  vec4 g1010 = vec4(gx10.y,gy10.y,gz10.y,gw10.y);
  vec4 g0110 = vec4(gx10.z,gy10.z,gz10.z,gw10.z);
  vec4 g1110 = vec4(gx10.w,gy10.w,gz10.w,gw10.w);
  vec4 g0001 = vec4(gx01.x,gy01.x,gz01.x,gw01.x);
  vec4 g1001 = vec4(gx01.y,gy01.y,gz01.y,gw01.y);
  vec4 g0101 = vec4(gx01.z,gy01.z,gz01.z,gw01.z);
  vec4 g1101 = vec4(gx01.w,gy01.w,gz01.w,gw01.w);
  vec4 g0011 = vec4(gx11.x,gy11.x,gz11.x,gw11.x);
  vec4 g1011 = vec4(gx11.y,gy11.y,gz11.y,gw11.y);
  vec4 g0111 = vec4(gx11.z,gy11.z,gz11.z,gw11.z);
  vec4 g1111 = vec4(gx11.w,gy11.w,gz11.w,gw11.w);

  vec4 norm00 = taylorInvSqrt(vec4(dot(g0000, g0000), dot(g0100, g0100), dot(g1000, g1000), dot(g1100, g1100)));
  g0000 *= norm00.x;
  g0100 *= norm00.y;
  g1000 *= norm00.z;
  g1100 *= norm00.w;

  vec4 norm01 = taylorInvSqrt(vec4(dot(g0001, g0001), dot(g0101, g0101), dot(g1001, g1001), dot(g1101, g1101)));
  g0001 *= norm01.x;
  g0101 *= norm01.y;
  g1001 *= norm01.z;
  g1101 *= norm01.w;

  vec4 norm10 = taylorInvSqrt(vec4(dot(g0010, g0010), dot(g0110, g0110), dot(g1010, g1010), dot(g1110, g1110)));
  g0010 *= norm10.x;
  g0110 *= norm10.y;
  g1010 *= norm10.z;
  g1110 *= norm10.w;

  vec4 norm11 = taylorInvSqrt(vec4(dot(g0011, g0011), dot(g0111, g0111), dot(g1011, g1011), dot(g1111, g1111)));
  g0011 *= norm11.x;
  g0111 *= norm11.y;
  g1011 *= norm11.z;
  g1111 *= norm11.w;

  float n0000 = dot(g0000, Pf0);
  float n1000 = dot(g1000, vec4(Pf1.x, Pf0.yzw));
  float n0100 = dot(g0100, vec4(Pf0.x, Pf1.y, Pf0.zw));
  float n1100 = dot(g1100, vec4(Pf1.xy, Pf0.zw));
  float n0010 = dot(g0010, vec4(Pf0.xy, Pf1.z, Pf0.w));
  float n1010 = dot(g1010, vec4(Pf1.x, Pf0.y, Pf1.z, Pf0.w));
  float n0110 = dot(g0110, vec4(Pf0.x, Pf1.yz, Pf0.w));
  float n1110 = dot(g1110, vec4(Pf1.xyz, Pf0.w));
  float n0001 = dot(g0001, vec4(Pf0.xyz, Pf1.w));
  float n1001 = dot(g1001, vec4(Pf1.x, Pf0.yz, Pf1.w));
  float n0101 = dot(g0101, vec4(Pf0.x, Pf1.y, Pf0.z, Pf1.w));
  float n1101 = dot(g1101, vec4(Pf1.xy, Pf0.z, Pf1.w));
  float n0011 = dot(g0011, vec4(Pf0.xy, Pf1.zw));
  float n1011 = dot(g1011, vec4(Pf1.x, Pf0.y, Pf1.zw));
  float n0111 = dot(g0111, vec4(Pf0.x, Pf1.yzw));
  float n1111 = dot(g1111, Pf1);

  vec4 fade_xyzw = quintic(Pf0);
  vec4 n_0w = mix(vec4(n0000, n1000, n0100, n1100), vec4(n0001, n1001, n0101, n1101), fade_xyzw.w);
  vec4 n_1w = mix(vec4(n0010, n1010, n0110, n1110), vec4(n0011, n1011, n0111, n1111), fade_xyzw.w);
  vec4 n_zw = mix(n_0w, n_1w, fade_xyzw.z);
  vec2 n_yzw = mix(n_zw.xy, n_zw.zw, fade_xyzw.y);
  float n_xyzw = mix(n_yzw.x, n_yzw.y, fade_xyzw.x);
  return 2.2 * n_xyzw;
}
#endif

#ifndef SRGB_EPSILON 
#define SRGB_EPSILON 0.00000001
#endif

#ifndef FNC_SRGB2RGB
#define FNC_SRGB2RGB
float srgb2rgb(float channel) {
  return (channel < 0.04045) ? channel * 0.0773993808 : pow((channel + 0.055) * 0.947867298578199, 2.4);
}

vec3 srgb2rgb(vec3 srgb) {
  return vec3(srgb2rgb(srgb.r + SRGB_EPSILON), 
        srgb2rgb(srgb.g + SRGB_EPSILON), 
        srgb2rgb(srgb.b + SRGB_EPSILON));
}

vec4 srgb2rgb(vec4 srgb) {
  return vec4(srgb2rgb(srgb.rgb), srgb.a);
}
#endif

#if !defined(FNC_SATURATE) && !defined(saturate)
#define FNC_SATURATE
#define saturate(x) clamp(x, 0.0, 1.0)
#endif

#ifndef FNC_RGB2SRGB
#define FNC_RGB2SRGB
float rgb2srgb(float channel) {
  return (channel < 0.0031308) ? channel * 12.92 : 1.055 * pow(channel, 0.4166666666666667) - 0.055;
}

vec3 rgb2srgb(vec3 rgb) {
  return saturate(vec3(rgb2srgb(rgb.r - SRGB_EPSILON), rgb2srgb(rgb.g - SRGB_EPSILON), rgb2srgb(rgb.b - SRGB_EPSILON)));
}

vec4 rgb2srgb(vec4 rgb) {
  return vec4(rgb2srgb(rgb.rgb), rgb.a);
}
#endif

#ifndef FNC_MIXOKLAB
#define FNC_MIXOKLAB
vec3 mixOklab( vec3 colA, vec3 colB, float h ) {
  #ifdef MIXOKLAB_COLORSPACE_SRGB
  colA = srgb2rgb(colA);
  colB = srgb2rgb(colB);
  #endif

  const mat3 kCONEtoLMS = mat3(                
     0.4121656120,  0.2118591070,  0.0883097947,
     0.5362752080,  0.6807189584,  0.2818474174,
     0.0514575653,  0.1074065790,  0.6302613616);
  const mat3 kLMStoCONE = mat3(
     4.0767245293, -1.2681437731, -0.0041119885,
    -3.3072168827,  2.6093323231, -0.7034763098,
     0.2307590544, -0.3411344290,  1.7068625689);
          
  vec3 lmsA = pow( kCONEtoLMS * colA, vec3(1.0/3.0) );
  vec3 lmsB = pow( kCONEtoLMS * colB, vec3(1.0/3.0) );
  
  vec3 lms = mix( lmsA, lmsB, h );
  
  vec3 rgb = kLMStoCONE*(lms*lms*lms);

  #ifdef MIXOKLAB_COLORSPACE_SRGB
  return rgb2srgb(rgb);
  #else
  return rgb;
  #endif
}

vec4 mixOklab( vec4 colA, vec4 colB, float h ) {
  return vec4( mixOklab(colA.rgb, colB.rgb, h), mix(colA.a, colB.a, h) );
}
#endif

float rayStrength(vec2 raySource, vec2 rayRefDirection, vec2 coord, float seedA, float seedB, float speed)
{
  vec2 sourceToCoord = coord - raySource;
  float cosAngle = dot(normalize(sourceToCoord), rayRefDirection);
  
  return clamp(
    (.45 + 0.15 * sin(cosAngle * seedA + u_time * speed)) +
    (0.3 + 0.2 * cos(-cosAngle * seedB + u_time * speed)),
    u_reach, 1.0) *
    clamp((u_resolution.x - length(sourceToCoord)) / u_resolution.x, u_reach, 1.0);
}

void main()
{
  vec2 uv = gl_FragCoord.xy / u_resolution.xy;
  uv.y = 1.0 - uv.y;
  vec2 coord = vec2(gl_FragCoord.x, u_resolution.y - gl_FragCoord.y);
  float speed = u_rays * 10.0;
  
  // Set the parameters of the sun rays
  vec2 rayPos1 = vec2(u_resolution.x * 0.7, u_resolution.y * -0.4);
  vec2 rayRefDir1 = normalize(vec2(1.0, -0.116));
  float raySeedA1 = 36.2214*speed;
  float raySeedB1 = 21.11349*speed;
  float raySpeed1 = 1.5*speed;
  
  vec2 rayPos2 = vec2(u_resolution.x * 0.8, u_resolution.y * -0.6);
  vec2 rayRefDir2 = normalize(vec2(1.0, 0.241));
  float raySeedA2 = 22.39910*speed;
  float raySeedB2 = 18.0234*speed;
  float raySpeed2 = 1.1*speed;
  
  // Calculate the colour of the sun rays on the current fragment
  vec4 rays1 =
    vec4(0.,0.,0., .0) +
    rayStrength(rayPos1, rayRefDir1, coord, raySeedA1, raySeedB1, raySpeed1) * u_colors[0];
   
  vec4 rays2 =
    vec4(0.,0.,0., .0) +
    rayStrength(rayPos2, rayRefDir2, coord, raySeedA2, raySeedB2, raySpeed2) * u_colors[1];
  
  vec4 fragColor = (rays1) + (rays2);
  
  // Attenuate brightness towards the bottom, simulating light-loss due to depth.
  float brightness = 1.0*u_reach - (coord.y / u_resolution.y);
  fragColor *= (brightness + (0.5+ u_intensity));
  
  // Ensure the background remains transparent
  fragColor.a = max(rays1.a, rays2.a) * (brightness + (0.5 + u_intensity));

  gl_FragColor = fragColor;
}