#version 420 core
out vec4 FragColor;

in vec3 Normal;
in vec3 FragPos;
in vec3 viewPos;
  
uniform vec3 lightPos;
uniform vec4 lightColor;
uniform vec4 meshColor;

struct Material {
    vec4 ambient;
    vec4 diffuse;
    vec4 specular;
    vec4 emissive;
    float shininess;
}; 
  
uniform Material material;

void main()
{
    vec3 normal = normalize(Normal);

    vec3 lightDir   = normalize(lightPos - FragPos);
    vec3 viewDir    = normalize(viewPos - FragPos);
    vec3 halfwayDir = normalize(lightDir + viewDir);

    // diffuse 
    float diff = max(dot(normal, lightDir), 0.0);

    // specular
    vec3 reflectDir = reflect(-lightDir, normal);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);

    vec4 ambient = lightColor * material.ambient;
    vec4 diffuse = lightColor * (diff * material.diffuse);
    vec4 specular = lightColor * (spec *material.specular);

    FragColor =  ambient + diffuse + specular + material.emissive;
}