layout(location=0) in vec2 TexCoord;
layout(location=0) out vec4 FragColor;

layout(binding=0) uniform sampler2D InputTexture;

vec3 Linear(vec3 c)
{
	//c = max(c, vec3(0.0));
	//return pow(c, 2.2);
	return c * c; // cheaper, but assuming gamma of 2.0 instead of 2.2
}

vec3 sRGB(vec3 c)
{
	c = max(c, vec3(0.0));
	//return pow(c, vec3(1.0 / 2.2));
	return sqrt(c); // cheaper, but assuming gamma of 2.0 instead of 2.2
}

#if defined(LINEAR)

vec3 Tonemap(vec3 color)
{
	return sRGB(color);
}

#elif defined(REINHARD)

vec3 Tonemap(vec3 color)
{
	color = color / (1.0 + color);
	return sRGB(color);
}

#elif defined(HEJLDAWSON)

vec3 Tonemap(vec3 color)
{
	vec3 x = max(vec3(0.0), color - 0.004);
	return (x * (6.2 * x + 0.5)) / (x * (6.2 * x + 1.7) + 0.06); // no sRGB needed
}

#elif defined(UNCHARTED2)

vec3 Uncharted2Tonemap(vec3 x)
{
	float A = 0.15;
	float B = 0.50;
	float C = 0.10;
	float D = 0.20;
	float E = 0.02;
	float F = 0.30;
	return ((x * (A * x + C * B) + D * E) / (x * (A * x + B) + D * F)) - E / F;
}

vec3 Tonemap(vec3 color)
{
	float W = 11.2;
	vec3 curr = Uncharted2Tonemap(color);
	vec3 whiteScale = vec3(1) / Uncharted2Tonemap(vec3(W));
	return sRGB(curr * whiteScale);
}

#elif defined(PALETTE)

layout(binding=1) uniform sampler2D PaletteLUT;

vec3 Tonemap(vec3 color)
{
	ivec3 c = ivec3(clamp(color.rgb, vec3(0.0), vec3(1.0)) * 63.0 + 0.5);
	int index = (c.r * 64 + c.g) * 64 + c.b;
	int tx = index % 512;
	int ty = index / 512;
	return texelFetch(PaletteLUT, ivec2(tx, ty), 0).rgb;
}

#else
#error Tonemap mode define is missing
#endif

void main()
{
	vec3 color = texture(InputTexture, TexCoord).rgb;
#ifndef PALETTE
	color = Linear(color); // needed because gzdoom's scene texture is not linear at the moment
#endif
	FragColor = vec4(Tonemap(color), 1.0);
}