#version 430 core

#define FAR_CLIP  10000.0f
#define width 1080
#define height 720

struct Triangle
{
    vec3 vA, vB, vC;
};
struct Light{
    vec4    dir;
    vec4    color;
    vec4    attenuation;
};
struct Primitive{
    vec4 A, B, C;
};
struct Camera{
    vec3    pos, dir, yAxis, xAxis ;
    float   tanFovY, tanFovX;
};
struct Ray{
    vec3    origin;
    vec3    dir;
};

layout(binding = 0, rgba32f) uniform image2D framebuffer;
layout(std430, binding = 1) buffer meshtriangles
 {
    Triangle tris[ ];
 };

uniform int mNumTriangles;
uniform sampler2D diffuse;
uniform uint reflectionDepth;
uniform Camera camera;
uniform mat4 mvpMatrix;
Light light;





float hitTriangle(Ray r, Primitive t)
{
vec3 v0 = t.A.xyz, v1 = t.B.xyz, v2 = t.C.xyz;

  vec3 v0v1 = v1 - v0;
  vec3 v0v2 = v2 - v0;

  vec3 pvec = cross(r.dir, v0v2);

  float det = dot(v0v1, pvec);

  if (det < 0.000001)
    return FAR_CLIP;

  float invDet = 1.0 / det;

  vec3 tvec = r.origin - v0;

  float u = dot(tvec, pvec) * invDet;

  if (u < 0 || u > 1)
    return FAR_CLIP;

  vec3 qvec = cross(tvec, v0v1);

  float v = dot(r.dir, qvec) * invDet;

  if (v < 0 || u + v > 1)
    return FAR_CLIP;

  return dot(v0v2, qvec) * invDet;
}


Ray initRay(uint x, uint y, Camera cam){
    Ray r;
    vec3 dir;
    float a, b, halfWidth, halfHeight;

    halfWidth = float(width)/2.0f;
    halfHeight = float(height)/2.0f;

    a = cam.tanFovX*( (float(x)-halfWidth+0.5f) / halfWidth);
    b = cam.tanFovY*( (halfHeight - float(y)-0.5f) / halfHeight);

    dir = normalize( a*cam.xAxis.xyz + b*cam.yAxis.xyz + cam.dir.xyz);

    r.dir = dir;
    r.origin = cam.pos.xyz;

    return r;
}

layout (local_size_x = 25, local_size_y = 8) in;
void main(void) {
    uint x = gl_GlobalInvocationID.x;
    uint y = gl_GlobalInvocationID.y;
    light.dir = vec4(0, -1, 0, 0);
    light.color = vec4(1, 1, 1, 1);
    light.attenuation = vec4(1.0f);
    if(x < width && y < height)
    {
        vec4 color = vec4(0.0f, 0.0f, 0.0f, 1.0f);
        vec4 tempColor = vec4(0);

        //Initialize the ray
        Ray r = initRay(x, y, camera);

        float t = FAR_CLIP, temp = FAR_CLIP;
        int currentObject = -1;


        for(uint n = 0; n < reflectionDepth; ++n)
        {
            for(int i = 0; i < mNumTriangles; i++)
            {

                    Primitive t0;
                    t0.A = vec4(tris[i].vA, 1);
                    t0.B =  vec4(tris[i].vB, 1);
                    t0.C =  vec4(tris[i].vC, 1);
                    temp = hitTriangle(r, t0);



                if(temp < t && temp >= -0.001f)
                {
                color = vec4(0, 1, 0,1);
                    t = temp;
                    currentObject = i;
                }
            }

        }

        imageStore(framebuffer, ivec2(x, y), color);

    }
}