#version 330 core
out vec4 FragColor;

in vec3 Normal;
in vec3 FragPos;
in vec2 TexCoords;

struct Material {
    sampler2D diffuse;
    sampler2D specular;
    float shininess;
};

struct PointLight {
    vec3 position;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;

    float constant;
    float linear;
    float quadratic;
};

struct DirectionalLight {
    vec3 direction;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};

struct SpotLight {
    vec3 position;  
    vec3 direction;
    float cutOff;
    float outerCutOff;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;

    float constant;
    float linear;
    float quadratic;
};

#define POINT_LIGHTS_COUNT 4

uniform Material material;
uniform vec3 viewPos;

uniform SpotLight spotLight;
uniform DirectionalLight directionalLight;
uniform PointLight pointLights[POINT_LIGHTS_COUNT];


vec3 ComputeDirectionalLight(DirectionalLight light, vec3 norm, vec3 viewDir)
{
    vec3 lightDir = normalize(-light.direction);
    vec3 reflectDir = reflect(-lightDir, norm);

    float diff = max(dot(norm, lightDir), 0.0);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);

    vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));
    vec3 diffuse = light.diffuse * diff * vec3(texture(material.diffuse, TexCoords));
    vec3 specular = light.specular * spec * vec3(texture(material.specular, TexCoords));

    return (ambient + diffuse + specular);
}

vec3 ComputePointLight(PointLight light, vec3 norm, vec3 viewDir, vec3 fragPos)
{
    float distance = length(light.position - fragPos);
    float attenuation = 1.0 / (light.constant + light.linear * distance + light.quadratic * (distance * distance));

    vec3 lightDir = normalize(light.position - fragPos);
    vec3 reflectDir = reflect(-lightDir, norm);

    float diff = max(dot(norm, lightDir), 0.0);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);

    vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));
    vec3 diffuse = light.diffuse * diff * vec3(texture(material.diffuse, TexCoords));
    vec3 specular = light.specular * spec * vec3(texture(material.specular, TexCoords));

    return (ambient * attenuation + diffuse * attenuation + specular * attenuation);
}

vec3 ComputeSpotLight(SpotLight light, vec3 norm, vec3 viewDir, vec3 fragPos) {
    vec3 lightDir = normalize(light.position - fragPos);
    vec3 reflectDir = reflect(-lightDir, norm);

    float theta = dot(lightDir, normalize(-light.direction));
    float epsilon = light.cutOff - light.outerCutOff;
    float intensity = clamp((theta - light.outerCutOff) / epsilon, 0.0, 1.0);

    float distance = length(light.position - fragPos);
    float attenuation = 1.0 / (light.constant + light.linear * distance + light.quadratic * (distance * distance));

    float diff = max(dot(norm, lightDir), 0.0);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);

    vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));
    vec3 diffuse = light.diffuse * diff * vec3(texture(material.diffuse, TexCoords));
    vec3 specular = light.specular * spec * vec3(texture(material.specular, TexCoords));

    // we leave ambient alone so there's always a little light
    return ((ambient * attenuation) + (diffuse * intensity * attenuation) + (specular * intensity * attenuation));
}

void main()
{
    vec3 norm = normalize(Normal);
    vec3 viewDir = normalize(viewPos - FragPos);

    vec3 result = vec3(0.0);
    
    result += ComputeDirectionalLight(directionalLight, norm, viewDir);
    for (int i = 0; i < POINT_LIGHTS_COUNT; i++) {
        result += ComputePointLight(pointLights[i], norm, viewDir, FragPos);
    }
    result += ComputeSpotLight(spotLight, norm, viewDir, FragPos);

    FragColor = vec4(result, 1.0);
}