#version 300 es

/*      _______________   ,--------------------------------------------------------.
       //`````````````\\  \                                                         \
      //~~~~~~~~~~~~~~~\\  \   by @ohsqueezy           &  @sleepin                   \
     //=================\\  \     [ohsqueezy.itch.io]     [sleepin.itch.io]           \
    //                   \\  \                                                         \
   //                     \\  \  zlib licensed code at [git.nugget.fun/nugget/gunkiss]  \
  //      ☆ GUNKISS ☆      \\  \                                                         \
 //_________________________\\  `--------------------------------------------------------*/

/* The precision declaration is required by OpenGL ES */
precision mediump float;

in vec2 uv;
uniform sampler2D base_texture;
uniform vec3 blend_min_hsv;
uniform float time;
uniform bool scroll;
out vec4 outputColor;

/* 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;
        outputColor = texelFetch(base_texture, ivec2(mod(vec2(gl_FragCoord.x + speed, gl_FragCoord.y - speed), vec2(texture_size))), 0);
    }
    else
    {
        outputColor = texture(base_texture, uv);
    }
    /* apply blending, leaving alpha unchanged */
    outputColor.xyz = min(outputColor.xyz, hsv2rgb(blend_min_hsv));
}