// Copyright © 2017 Project Golan, all rights reserved.
#version 120

uniform sampler2D DGE_Texture;
uniform int       DGE_Ticks;
uniform float     DGE_Seconds;

varying vec4 color;
varying vec4 texcoord;

vec4 HSVToRGB(float h, float s, float v, float a)
{
   h *= 360.0;

        if(h < 0)     h = 0;
   else if(h > 359.5) h = 359.5;

   float chroma = v * s;
   float hp = h / 60.0;
   float x = chroma * (1 - abs(mod(hp, 2) - 1));
   float r1 = 0, g1 = 0, b1 = 0;

        if(0 <= hp && hp < 1) r1 = chroma, g1 = x,      b1 = 0;
   else if(1 <= hp && hp < 2) r1 = x,      g1 = chroma, b1 = 0;
   else if(2 <= hp && hp < 3) r1 = 0,      g1 = chroma, b1 = x;
   else if(3 <= hp && hp < 4) r1 = 0,      g1 = x,      b1 = chroma;
   else if(4 <= hp && hp < 5) r1 = x,      g1 = 0,      b1 = chroma;
   else if(5 <= hp && hp < 6) r1 = chroma, g1 = 0,      b1 = x;

   float m = v - chroma;
   return vec4(r1 + m, g1 + m, b1 + m, a);
}

void main(void)
{
   const float pi = 3.14159265;

   float t = (DGE_Seconds * 1000.0) / 32.0;
   vec2 uv = texcoord.xy * vec2(256.0, 224.0);
   float bx = uv.x + 0.5 * sin(t / 8.0);
   float by = uv.y + 0.5 * cos(t / 8.0);
   float v;

   v  = sin((-bx + t) / 32.0);
   v += cos((by + t) / 32.0);
   v += sin((bx + by + t) / 32.0);
   v += sin((sqrt(pow(bx + sin(t / 3.0), 2.0) + pow(by + cos(t / 2.0), 2.0) + 1.0) + t) / 128.0);

   gl_FragColor =
      texture2D(DGE_Texture, texcoord.xy) *
      HSVToRGB(sin(v * pi) * 0.5 + 0.5, 1.0, 0.2, 1.0) *
      color;
}

// EOF