/* ******************************************************************* */
/* Resolve RIM pass and add blur if needed                                 */
/* ******************************************************************* */
uniform sampler2D strokeColor;
uniform sampler2D strokeDepth;
uniform sampler2D strokeRim;

uniform vec3 mask_color;
uniform int mode;

out vec4 FragColor;

#define MODE_NORMAL 0
#define MODE_OVERLAY 1
#define MODE_ADD 2
#define MODE_SUB 3
#define MODE_MULTIPLY 4
#define MODE_DIVIDE 5

float overlay_color(float a, float b)
{
  float rtn;
  if (a < 0.5) {
    rtn = 2.0 * a * b;
  }
  else {
    rtn = 1.0 - 2.0 * (1.0 - a) * (1.0 - b);
  }

  return rtn;
}

vec4 get_blend_color(int mode, vec4 src_color, vec4 mix_color)
{
  vec4 outcolor;
  if (mode == MODE_NORMAL) {
    outcolor = mix_color;
  }
  else if (mode == MODE_OVERLAY) {
    outcolor.r = overlay_color(src_color.r, mix_color.r);
    outcolor.g = overlay_color(src_color.g, mix_color.g);
    outcolor.b = overlay_color(src_color.b, mix_color.b);
  }
  else if (mode == MODE_ADD) {
    outcolor = src_color + mix_color;
  }
  else if (mode == MODE_SUB) {
    outcolor = src_color - mix_color;
  }
  else if (mode == MODE_MULTIPLY) {
    outcolor = src_color * mix_color;
  }
  else if (mode == MODE_DIVIDE) {
    outcolor = src_color / mix_color;
  }
  else {
    outcolor = mix_color;
  }

  /* use always the alpha of source color */

  outcolor.a = src_color.a;
  /* use alpha to calculate the weight of the mixed color */
  outcolor = mix(src_color, outcolor, mix_color.a);

  return outcolor;
}

void main()
{
  ivec2 uv = ivec2(gl_FragCoord.xy);

  float stroke_depth = texelFetch(strokeDepth, uv.xy, 0).r;
  vec4 src_pixel = texelFetch(strokeColor, uv.xy, 0);
  vec4 rim_pixel = texelFetch(strokeRim, uv.xy, 0);

  vec4 outcolor = src_pixel;

  /* is transparent */
  if (src_pixel.a == 0.0f) {
    discard;
  }
  /* pixel is equal to mask color, keep */
  else if (src_pixel.rgb == mask_color.rgb) {
    outcolor = src_pixel;
  }
  else {
    if (rim_pixel.a == 0.0f) {
      outcolor = src_pixel;
    }
    else {
      outcolor = get_blend_color(mode, src_pixel, rim_pixel);
    }
  }

  gl_FragDepth = stroke_depth;
  FragColor = outcolor;
}