#version 330 core

uniform sampler2D PositionSampler;
uniform sampler2D NormalSampler;
uniform sampler2D ColorSampler;

uniform float Linear;
uniform float Quadratic;
uniform vec3 Eye;
uniform int LightCount;

layout (location = 0) out vec4 Color;

in vec4 PixelTexture;

layout (std140) uniform Lights
{
  vec4 light[256];
};

void main()
{
  vec4 position = texture(PositionSampler, PixelTexture.xy);
  vec4 normal = texture(NormalSampler, PixelTexture.xy);
  vec4 color = texture(ColorSampler, PixelTexture.xy);

  vec3 out_color = color.xyz * 0.1;
  for (int i = 0; i < LightCount; i++) {
    vec3 light_position = light[i].xzy + vec3(0, 0, 0.5);
    float light_distance = length(light_position - position.xyz);
    vec3 light_direction = normalize(light_position - position.xyz);
    float diffuse = max(dot(normal.xyz, light_direction), 0.0);
    if (normal.w == 1.0) // two-sided
      diffuse = 1.0;

    //float attenuation = 1.0 / (1.0 + Linear * light_distance + Quadratic * light_distance * light_distance);
    float attenuation = 1.0 / (1.0 + Quadratic * light_distance * light_distance);
    out_color += color.xyz * attenuation * diffuse;
  }

  //vec3 light_direction = normalize(Eye.xyz - position.xyz);
  //float diffuse = max(dot(normal.xyz, light_direction), 0.0);

  if (normal == vec4(0, 0, 0, 0))
    out_color = color.xyz;

  Color = vec4(out_color, 1.0);
}