#version 450 core
in vec2 vTexPos;
out vec4 fColor;
layout (location = 0) uniform vec2 screensize;
layout(binding = 0) uniform sampler2D screenTexture;
vec3 f (float x, float y)
//{ return texture(screenTexture, vTexPos + vec2((x+0.5)/screensize.x,(y+0.5)/screensize.y)).xyz; 
{ return texture(screenTexture, vTexPos + vec2(x/screensize.x,y/screensize.y)).xyz; 
}
bool t (vec3 x, vec3 y)
{ return dot(x-y,x-y) < 0.005;
}
bool t3 (vec3 x, vec3 y, vec3 z)
{ return t(x,y) && t(y,z);
}
vec3 c = f(0,0);
bool bt (vec3 x, vec3 y)
{ return x.x+x.y+x.z > y.x+y.y+y.z;}
bool t4 (vec3 x, vec3 y, vec3 z)
{ return t(x,z) && (t(x,y) || bt(x,c)) ; }
bool incenter (int x) { return x > 0 && x < 3; }
int three = int(( floor(vTexPos.y * screensize.y))) % 3;
int i = int(( floor(vTexPos.x * screensize.x))) % 4;
int j = int(( floor(vTexPos.y * screensize.y))) % 4;
vec4 edgecase (vec3 e1, vec3 e2)
{ return vec4((t(e1,e2) && bt(e1,c) ? e1 : c),1); }
vec4 corncase (vec3 e1, vec3 e2, vec3 corn)
{ return vec4( (t(e1,e2) && false == (t(corn,c)) ? e1 : c) , 1);}
//{ return vec4( (t(e1,e2) ? e1 : c) , 1);}
void main() 
{
vec3 tl = f(-4, 4);
vec3 tt = f( 0, 4);
vec3 tr = f( 4, 4);
vec3 mr = f( 4, 0);
vec3 br = f( 4,-4);
vec3 bb = f( 0,-4);
vec3 bl = f(-4,-4);
vec3 ml = f(-4, 0);
vec3 tlc = f(-1, 1);
vec3 trc = f( 1, 1);
vec3 brc = f( 1,-1);
vec3 blc = f(-1,-1);
//    if (t4(tl,tr,br))
//        { fColor = vec4(tl,1);}
//    else if (t4(tr,br,bl))
//        { fColor = vec4(tr,1);}
//    else if (t4(br,bl,tl))
//        { fColor = vec4(br,1);}
//    else if (t4(bl,tl,tr))
//        { fColor = vec4(bl,1);}
if (incenter(i) && incenter(j))
    {fColor = vec4(c,1); }
else
    { fColor = vec4(0,0,0,1);
      switch (i * 10 + j) {
        case 10:
        case 01:
            fColor = edgecase(ml,bb);
            break;
        case 13:
        case 02:
            fColor = edgecase(ml,tt);
            break;
        case 23:
        case 32:
            fColor = edgecase(mr,tt);
            break;
        case 20:
        case 31:
            fColor = edgecase(mr,bb);
            break;
        case 00:
            fColor = corncase(ml,bb,bl);
            break;
        case 03:
            fColor = corncase(ml,tt,tl);
            break;
        case 33:
            fColor = corncase(mr,tt,tr);
            //fColor = vec4(1,0,0,1);
            break;
        case 30:
            fColor = corncase(mr,bb,br);
            break;
                          }
    }
}