#version 460

#extension GL_GOOGLE_include_directive : require
#extension GL_EXT_nonuniform_qualifier : require

#define COMPOSITE_PASS

#include "structures.layout"

layout (location = 0) out vec4 FragColor;

void BubbleSort(inout uvec2 array[OIT_LAYERS], int n)
{
	for(int i = (n - 2); i >= 0; --i)
	{
		for(int j = 0; j <= i; ++j)
		{
			if(uintBitsToFloat(array[j].g) >= uintBitsToFloat(array[j+1].g))
			{
				uvec2 temp = array[j+1];
				array[j+1] = array[j];
				array[j] = temp;
			}
		}
	}
}

float UnPreMultSRGBToLinear(float col)
{
	return (col < 0.04045f) ? (col / 12.92f) : pow((col + 0.055f) / 1.055f, 2.4f);
}

vec4 UnPreMultSRGBToLinear(vec4 col)
{
	col.r = UnPreMultSRGBToLinear(col.r);
	col.g = UnPreMultSRGBToLinear(col.g);
	col.b = UnPreMultSRGBToLinear(col.b);
	return col;
}

void DoBlend(inout vec4 color, vec4 base_color)
{
	color.rgb += (1 - color.a) * base_color.rgb;
	color.a += (1 - color.a) * base_color.a;
}

void DoBlendPacked(inout vec4 color, uint fragment)
{
	vec4 unpacked_color = unpackUnorm4x8(fragment);
	//unpacked_color = UnPreMultSRGBToLinear(unpacked_color);
	unpacked_color.rgb *= unpacked_color.a;
	DoBlend(color, unpacked_color);
}

void main()
{
	ivec2 coord = ivec2(gl_FragCoord.xy);
	int store_mask = 0;
	int view_size = int(G.res.x) * int(G.res.y);
	int sample_id = 0;
	int list_pos = view_size * OIT_LAYERS * sample_id + coord.y * int(G.res.x) + coord.x;
	uvec2 array[OIT_LAYERS];

	vec4 color = vec4(0.0);

	int fragments = int(imageLoad(ImageAux, coord).r);
	fragments = min(OIT_LAYERS, fragments);

	for (int i = 0; i < fragments; i++)
	{
		array[i] = imageLoad(ImageABuffer, list_pos + i * view_size).rg;
	}

	BubbleSort(array, fragments);

	vec4 color_sum = vec4(0.0);

	for(int i = 0; i < fragments; i++)
	{
		DoBlendPacked(color_sum, array[i].x);
	}

	FragColor = color_sum;
}