#version 460 core

// gbuffer textures
uniform sampler2D s_albedo;
uniform sampler2D s_depth;
uniform sampler2D s_normal;
uniform sampler2D s_material;
uniform sampler2D s_position;

// lights
#define MAX_LIGHT_COUNT 100
#define POINT       0
#define SPOT        1
#define DIRECTIONAL 2
#define AMBIENT     3

struct light_t {
  vec3 color;
  vec3 position;
  vec3 direction;
  float intensity;
  int type;
};

uniform light_t lights[MAX_LIGHT_COUNT];
uniform int light_count;

uniform vec3 view_pos;

// from vertex shader
in vec3 pos;
in vec2 tex;

out vec4 FragColor;

vec3 albedo;
float depth;
vec3 normal;
vec3 material; // specular, roughness, metalic
vec3 position;
vec2 texture_coords;

float specular;
float roughness;
float metalic;

vec3 calc_light(light_t light) {
  // diffuse
  vec3 light_dir = normalize(light.position - position);
  float diff = max(dot(normal, light_dir), 0);
  vec3 diffuse_light = diff * light.color * light.intensity;

  // specular
  float specular_strength = 0.5;
  vec3 view_dir = normalize(view_pos - position);
  vec3 reflect_dir = reflect(-light_dir, normal);

  float spec = pow(max(dot(view_dir, reflect_dir), 0), 32);
  vec3 specular_light = specular_strength * spec * light.color * light.intensity * specular;

  // attenuation
  float dist = length(light.position - position);
  float attenuation = 1 / max(pow(dist, 2), 1);

  return (diffuse_light + specular_light) * attenuation;
}

void main() {
  albedo = pow(texture(s_albedo, tex).rgb, vec3(2.2));
  depth = texture(s_depth, tex).x;
  normal = normalize(texture(s_normal, tex).rgb);
  material = texture(s_material, tex).xyz;
  {
    specular = material.x;
    roughness = 1 - material.y;
    metalic = material.z;
  }
  position = texture(s_position, tex).xyz;

  vec3 light_result = vec3(0.1);
  for (int i = 0; i < light_count; i++) {
    light_result += calc_light(lights[i]);
  }
  FragColor = vec4(albedo * light_result, 1);
}