#version 430 core
layout (points) in;
layout (triangle_strip, max_vertices = 11) out;

uniform vec2 lightPos;
uniform mat4 perpMat;
uniform mat4 worldMat;
uniform float facesToDraw;

vec2 lightPosa = ( perpMat * vec4(lightPos,0,1) ).xy;

vec4 shift (vec4 p)
{ return vec4 (p.xy + (200 * (p.xy-lightPos)), 0 , 1);
}
float isLHS (vec2 startV, vec2 testV)
{
    return sign( -startV.x * testV.y + startV.y * testV.x);
}
// construct a box with openings on bottom face and face away from wall
void main()
{
vec4 p1 = vec4 (gl_in[0].gl_Position.xy,0,1);
vec4 p2 = vec4 (gl_in[0].gl_Position.zw,0,1);
if (isLHS (p1.xy - lightPos, p2.xy - lightPos) < 0)
{
vec4 p3 = vec4 (p1.xy,-0.5,1);
vec4 p4 = vec4 (p2.xy,-0.5,1);
vec4 p5 = shift(p1);
vec4 p6 = shift(p2);
vec4 p7 = vec4 (p6.xy,-0.5,1);
vec4 p8 = vec4 (p5.xy,-0.5,1);

vec4 a1 = perpMat * p1;
vec4 a2 = perpMat * p2;
vec4 a3 = perpMat * p3;
vec4 a4 = perpMat * p4;
vec4 a5 = perpMat * p5;
vec4 a6 = perpMat * p6;
vec4 a7 = perpMat * p7;
vec4 a8 = perpMat * p8;

//  gl_Position = a1; EmitVertex();
//  gl_Position = a5; EmitVertex();
//  gl_Position = a2; EmitVertex();
//  gl_Position = a6; EmitVertex();

  gl_Position = a4; EmitVertex();
  gl_Position = a3; EmitVertex();
  gl_Position = a7; EmitVertex();
  gl_Position = a8; EmitVertex();
  gl_Position = a5; EmitVertex();
  gl_Position = a3; EmitVertex();
  gl_Position = a1; EmitVertex();
  gl_Position = a4; EmitVertex();
  gl_Position = a2; EmitVertex();
  gl_Position = a7; EmitVertex();
  gl_Position = a6; EmitVertex();

  EndPrimitive();
} else {}
}

//  //  void main()
//  //  {
//  //    vec4 frontL4 = worldMat * vec4(gl_in[0].gl_Position.xy, 0 ,1);
//  //    vec4 frontR4 = worldMat * vec4(gl_in[0].gl_Position.zw, 0 ,1);
//  //    vec2 frontL = frontL4.xy;
//  //    vec2 frontR = frontR4.xy;
//  //  
//  //      emitLine (frontR);
//  //      emitLine (frontL);
//  //    EndPrimitive();
//  //  }
//  gl_Position = perspective * worldMat * p4; EmitVertex();
//  gl_Position = perspective * worldMat * p3; EmitVertex();
//  gl_Position = perspective * worldMat * p7; EmitVertex();
//  gl_Position = perspective * worldMat * p8; EmitVertex();
//  gl_Position = perspective * worldMat * p5; EmitVertex();
//  gl_Position = perspective * worldMat * p3; EmitVertex();
//  gl_Position = perspective * worldMat * p1; EmitVertex();
//  gl_Position = perspective * worldMat * p4; EmitVertex();
//  gl_Position = perspective * worldMat * p2; EmitVertex();
//  gl_Position = perspective * worldMat * p7; EmitVertex();
//  gl_Position = perspective * worldMat * p6; EmitVertex();
//  gl_Position = perspective * worldMat * p5; EmitVertex();
//void emitLine (vec2 pa)
//{
//    gl_Position = vec4 (pa, 0, 1);
//    EmitVertex();
//    gl_Position = shift (vec4 (pa,0,1)); //vec4 (pa + (200 * (pa - lightPosa)), 0 , 1);
//    EmitVertex();
//}