(ns advent.screens.shader
  (:require [advent.utils :as utils]))
(println "loading " *ns*)


(def v-shader (constantly "attribute vec4 a_position;
attribute vec4 a_color;
attribute vec2 a_texCoord0;

uniform mat4 u_projTrans;

varying vec4 v_color;
varying vec2 v_texCoords;

void main() {
    v_color = a_color;
    v_texCoords = a_texCoord0;
    gl_Position = u_projTrans * a_position;
}"))


(def mobile-pix-shader
  "
  #ifdef GL_ES
    #define LOWP lowp
    #define HIGHP highp
    precision mediump float;
  #else
    #define LOWP
    #define HIGHP
  #endif

  varying vec4 v_color;
  varying HIGHP vec2 v_texCoords;
  uniform HIGHP float multiply_amount;
  uniform HIGHP float hue_amount;

  uniform sampler2D u_texture;

  vec4 toGrayscale(in vec4 color)
  {
  float average = (color.r + color.g + color.b) / 3.0;
  return vec4(average, average, average, color.a);
  }

  vec4 colorize(in vec4 grayscale, in vec4 color)
  {
    return (grayscale * color);
  }


  void main ()
  {
    vec4 scaledColor = texture2D(u_texture, v_texCoords);

    vec4 grayscale = toGrayscale(scaledColor);
    vec4 colorizedOutput = mix(scaledColor, colorize(grayscale, v_color.rgba),  hue_amount);

    vec4 multiplied = mix(colorizedOutput.rgba, v_color.rgba * scaledColor.rgba, multiply_amount);

    gl_FragColor = vec4(multiplied.rgb, scaledColor.a * v_color.a);

  }
  "
  )

(def desktop-pix-shader
  "
#ifdef GL_ES
    #define LOWP lowp
    #define HIGHP highp
    precision mediump float;
#else
    #define LOWP
    #define HIGHP
#endif

varying vec4 v_color;
varying HIGHP vec2 v_texCoords;
uniform HIGHP float multiply_amount;
uniform HIGHP float hue_amount;

uniform sampler2D u_texture;

vec4 toGrayscale(in vec4 color)
{
  float average = (color.r + color.g + color.b) / 3.0;
  return vec4(average, average, average, color.a);
}

vec4 colorize(in vec4 grayscale, in vec4 color)
{
    return (grayscale * color);
}


void main ()
{
    HIGHP vec2 sz = vec2 (2048.0, 2048.0);
    HIGHP vec3 step = vec3 (1.0 / 4.0, 1.0 / 4.0, 0.0);
    HIGHP vec2 tex_pixel = sz * v_texCoords - step.xy / 2.0;

    HIGHP vec2 corner = floor (tex_pixel) + 1.0;
    HIGHP vec2 frac = min ((corner - tex_pixel) * vec2 (4.0, 4.0), vec2 (1.0, 1.0));

    HIGHP vec4 c1 = texture2D (u_texture, (floor (tex_pixel + step.zz) + 0.5) / sz);
    HIGHP vec4 c2 = texture2D (u_texture, (floor (tex_pixel + step.xz) + 0.5) / sz);
    HIGHP vec4 c3 = texture2D (u_texture, (floor (tex_pixel + step.zy) + 0.5) / sz);
    HIGHP vec4 c4 = texture2D (u_texture, (floor (tex_pixel + step.xy) + 0.5) / sz);

    c1 *=        frac.x  *        frac.y;
    c2 *= (1.0 - frac.x) *        frac.y;
    c3 *=        frac.x  * (1.0 - frac.y);
    c4 *= (1.0 - frac.x) * (1.0 - frac.y);
    vec4 scaledColor = (c1 + c2 + c3 + c4);

    vec4 grayscale = toGrayscale(scaledColor);
    vec4 colorizedOutput = mix(scaledColor, colorize(grayscale, v_color.rgba),  hue_amount);

    vec4 multiplied = mix(colorizedOutput.rgba, v_color.rgba * scaledColor.rgba, multiply_amount);

    gl_FragColor = vec4(multiplied.rgb, scaledColor.a * v_color.a);

}
")


(defn pix-shader []
  (if utils/mobile?
    mobile-pix-shader
    desktop-pix-shader))