/*     _______________   ,----------------------------------------------------------------.
      //`````````````\\  \                                                                 \
     //~~~~~~~~~~~~~~~\\  \   by @ohsqueezy           &  @sleepin                           \ 
    //=================\\  \     [ohsqueezy.itch.io]     [sleepin.itch.io]                   \ 
   //                   \\  \                                                                 \ 
  //                     \\  \  code released under the zlib license [git.nugget.fun/pudding]  \ 
 //      ☆ GUNKISS ☆      \\  \                                                                 \
//_________________________\\  `---------------------------------------------------------------*/

#version 130

in vec2 uv;
uniform sampler2D base_texture;
uniform vec3 blend_min_hsv;
uniform float time;
uniform bool scroll = false;

/* from http://lolengine.net/blog/2013/07/27/rgb-to-hsv-in-glsl, licensed under WTFPL */
vec3 hsv2rgb(vec3 c)
{
    vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
    vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
    return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
}

void main(void)
{
    if (scroll)
    {
        ivec2 texture_size = textureSize(base_texture, 0);
        float speed = time * 35.0;
        gl_FragColor = texelFetch(base_texture, ivec2(mod(vec2(gl_FragCoord.x + speed, gl_FragCoord.y - speed), texture_size)), 0);
    }
    else
    {
        gl_FragColor = texture(base_texture, uv);
    }
    /* apply blending, leaving alpha unchanged */
    gl_FragColor.xyz = min(gl_FragColor.xyz, hsv2rgb(blend_min_hsv));
}