#include "RayTracingHeader.hlsli"

SamplerState gWrapSampler : register(s0);
TextureCube gObjBackground : register(t0); // Not used right now
RWTexture2D<float4> gResult : register(u0);

cbuffer cbCamera : register(b0)
{
    Camera gCamera;
};

cbuffer cbGeneralInfo : register(b1)
{
    uint gWidth;
    uint gHeight;
    uint gMaxRecursion; // Not used right now
    float gRayMaxLength;
};

[numthreads(32, 32, 1)]
void main( uint3 DTid : SV_DispatchThreadID,
			uint3 GroupID : SV_GroupThreadID )
{
    gResult[DTid.xy] = float4(0, 0, 0, 1);
    float u = (float) DTid.x / (float) gWidth;
    float v = (float) DTid.y / (float) gHeight;

    float4 currentRayDirection = gCamera.TopLeftCorner + u * (gCamera.TopRightCorner - gCamera.TopLeftCorner)
										+ v * (gCamera.BottomLeftCorner - gCamera.TopLeftCorner);
    currentRayDirection.w = 0.0f;
    currentRayDirection = normalize(currentRayDirection);
    Ray r;
    r.Origin = gCamera.CamPosition.xyz;
    r.Direction = currentRayDirection.xyz;
    r.length = gRayMaxLength;

    Sphere s1;
    s1.Position = float3(0, 0, 10);
    s1.Radius = 1;
    if (s1.Intersect(r))
    {
        float4 reflectedColor = float4(1, 0, 0, 1);
		gResult[DTid.xy] = reflectedColor;
    }

}

class Camera
{
    float4 CamPosition;
    float4 TopLeftCorner;
    float4 TopRightCorner;
    float4 BottomLeftCorner;
};

class Ray
{
    float3 Origin;
    float3 Direction;
    float length;
};

class Sphere
{
    float3 Position;
    float Radius;
    bool Intersect(Ray r)
    {
        float3 OriginToSphere = Position - r.Origin;
        float projection = dot(OriginToSphere, r.Direction);
        float3 distanceVector = OriginToSphere - projection * r.Direction;
        float distanceVectorLengthSQ = dot(distanceVector, distanceVector);
        float radiusSQ = Radius * Radius;
        if (distanceVectorLengthSQ > radiusSQ)
            return false;
		
        float newLength = projection - sqrt(radiusSQ - distanceVectorLengthSQ);
        if (newLength < 0.0f || newLength > r.length)
            return false;

        r.length = newLength;

        return true;
    }
};