#version 430 core

layout(local_size_x = 16, local_size_y = 16) in;
layout(binding = 0, rgba32f) uniform image2D output_image;
layout(binding = 1, rgba32f) uniform image2D accumulation_image;

struct GPUObject {
	vec3    position;       // 12 + 4
	
	vec3	normal;			// 12 + 4
	
	vec3	vertex1;		// 12 + 4
	vec3	vertex2;		// 12 + 4
	
	float   radius;         // 4

	int		mat_index;		// 4
	int     type;           // 4
};

struct GPUMaterial
{
	vec3    color;          // 12 + 4
	float   emission;       // 4
	float   roughness;      // 4
	float   metallic;       // 4
	int		type;			// 4
};

layout(std430, binding = 1) buffer ObjectBuffer
{
	GPUObject objects[];
};

layout(std430, binding = 2) buffer MaterialBuffer
{
	GPUMaterial materials[];
};

uniform int     u_objectsNum;
uniform vec2    u_resolution;
uniform vec3    u_cameraPosition;
uniform mat4    u_viewMatrix;
uniform int		u_frameCount;
uniform float	u_time;

struct Ray
{
	vec3 origin;
	vec3 direction;
};

struct hitInfo
{
	float	t;
	vec3	normal;
	vec3	position;
	int		obj_index;
};

#include "shaders/random.glsl"
#include "shaders/intersect.glsl"
#include "shaders/scatter.glsl"

hitInfo	traceRay(Ray ray)
{
	hitInfo hit;
	hit.t = 1e30;
	hit.obj_index = -1;

	for (int i = 0; i < u_objectsNum; i++)
	{
		GPUObject obj = objects[i];

		hitInfo temp_hit;
		if (intersect(ray, obj, temp_hit) && temp_hit.t > 0.0f && temp_hit.t < hit.t)
		{
			hit.t = temp_hit.t;
			hit.obj_index = i;
			hit.position = temp_hit.position;
			hit.normal = temp_hit.normal;
		}
	}

	return (hit);
}

vec3    pathtrace(Ray ray, inout uint rng_state)
{
	vec3	color = vec3(1.0);
	vec3	light = vec3(0.0);

	float	closest_t = 1e30;

	for (int i = 0; i < 5; i++)
	{
		hitInfo hit = traceRay(ray);
		if (hit.obj_index == -1)
		{
			light += vec3(0); //ambient color 
			break;
		}

		GPUObject obj = objects[hit.obj_index];
		GPUMaterial mat = materials[obj.mat_index];
		
		// RR
		float p = max(color.r, max(color.g, color.b));
        if (randomValue(rng_state) > p)
            break;
        color /= p;
		//

		color *= mat.color;
		light += mat.emission * mat.color;
		
		if (mat.emission > 0.0)
			break;

		ray = newRay(hit, ray, rng_state);
	}
	return (color * light);
}

void main()
{
	ivec2 pixel_coords = ivec2(gl_GlobalInvocationID.xy);
	if (pixel_coords.x >= int(u_resolution.x) || pixel_coords.y >= int(u_resolution.y)) 
		return;

	vec2 uv = (vec2(pixel_coords) / u_resolution) * 2.0 - 1.0;;
	uv.x *= u_resolution.x / u_resolution.y;

	float fov = 90.0;
	float focal_length = 1.0 / tan(radians(fov) / 2.0);
	vec3 view_space_ray = normalize(vec3(uv.x, uv.y, -focal_length));

	vec3 ray_direction = normalize((inverse(u_viewMatrix) * vec4(view_space_ray, 0.0)).xyz);
	Ray ray = Ray(u_cameraPosition, ray_direction);

	uint rng_state = uint(u_resolution.x) * uint(pixel_coords.y) + pixel_coords.x;
	rng_state = rng_state + u_frameCount * 719393;

	vec3 color = pathtrace(ray, rng_state);
	
	float blend = 1.0 / float(u_frameCount + 1);
    vec4 accum = imageLoad(accumulation_image, pixel_coords);
    accum.rgb = mix(accum.rgb, color, blend);
	accum.a = 1.0;

    imageStore(accumulation_image, pixel_coords, accum);
    
    vec4 final_color = vec4(sqrt(accum.r), sqrt(accum.g), sqrt(accum.b), accum.a);
	imageStore(output_image, pixel_coords, final_color);
}