#include "Macros.fxh"

#define FLT_MAX 3.402823466e+38

DECLARE_TEXTURE(Texture, 0);
DECLARE_TEXTURE(Palette, 1);

BEGIN_CONSTANTS

	int PaletteWidth   _ps(c0)   _cb(c0);

END_CONSTANTS

struct VertexInput
{
	float4 Position : POSITION;
	float2 TexCoord : TEXCOORD;
};

struct PixelInput
{
	float4 Position : SV_POSITION;
	float2 TexCoord : TEXCOORD0;
};

PixelInput main_vs(VertexInput input)
{
	PixelInput output;

	output.Position = input.Position;
	output.TexCoord = input.TexCoord;

	return output;
}

float4 main_ps(PixelInput input) : SV_TARGET0
{
	float4 sampled = SAMPLE_TEXTURE(Texture, input.TexCoord);

	float3 sampled_color = sampled.rgb;
	
	float3 closest_color = float3(0, 0, 0);
	float closest_dist = FLT_MAX;

	for (int i = 0; i < PaletteWidth; i++)
	{
		float3 palette_color = SAMPLE_TEXTURE(Palette, float2(i / (float)PaletteWidth, 0));
		float dist = distance(palette_color, sampled_color);
		if (dist < closest_dist)
		{
			closest_dist = dist;
			closest_color = palette_color;
		}
	}

	return float4(closest_color, sampled.a);
}

Technique PaletteCrush
{
	Pass
	{
		VertexShader = compile vs_3_0 main_vs();
		PixelShader = compile ps_3_0 main_ps();
	}
}