#version 450

layout(std140, set = 0, binding = 0) uniform UBO
{
   mat4 MVP;
   vec4 OutputSize;
   vec4 OriginalSize;
   vec4 SourceSize;
   uint FrameCount;
} global;

////////////////////////////////////////////////////////
//	GTU-famicom version 0.50
//	Author: aliaspider - aliaspider@gmail.com
//	License: GPLv3      
////////////////////////////////////////////////////////

#define TO_INT2(X) int(floor(((X) * 3.0) + 0.5))
#define TO_INT3(X) int(floor(((X) * 7.0) + 0.5))
#define TO_INT4(X) int(floor(((X) * 15.0) + 0.5))

bool InColorp (int p, int color) {
  return ((color + p) % 12 < 6);
}

float NTSCsignal(int emphasis, int level, int color, int p)
{
	float black=.518;
	float white=1.962;

	float attenuation=0.746;
	const float levels[8] = float[] (0.350 , 0.518, 0.962, 1.550,
							  1.094f, 1.506, 1.962, 1.962);
	if(color > 13)  level = 1;
	float low  = levels[0 + level];
	float high = levels[4 + level];
	if(color == 0) low = high;
	if(color > 12) high = low;


   float signal = InColorp(p, color) ? high : low;

   if( (bool(emphasis & 1) && InColorp(p, 0))
   ||  (bool(emphasis & 2) && InColorp(p, 4))
   ||  (bool(emphasis & 4) && InColorp(p, 8)) ) signal = signal * attenuation;


   signal = (signal-black) / (white-black);

   return signal;
}

#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;
layout(location = 1) out float colorPhase;

void main()
{
   gl_Position = global.MVP * Position;
   vTexCoord = TexCoord;
   vec2 pos = (vTexCoord.xy*global.OutputSize.xy)-0.5;
   colorPhase = 8.0001 + pos.x + pos.y * 4.0001 + global.FrameCount * 4.0001;
}

#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 1) in float colorPhase;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;

void main()
{
	vec4 c=texture(Source, vTexCoord.xy);

	int color    = TO_INT4(c.x);
	int level    = TO_INT2(c.y);
	int emphasis = TO_INT3(c.z);

	float signal = NTSCsignal(emphasis,level,color,int(colorPhase + 0.5));
   FragColor = vec4(signal);
}