#version 430 core

#pragma optimize(on)
#pragma debug(off)

const int MaxLights = 8;

// Structure for holding general light properties
struct GeneralLight
{

    vec4 ambientColor;      // ambient color of the light
    vec4 diffuseColor;      // diffuse color of the light
    vec4 specularColor;     // specular color of the light

                            // Either the position or direction
                            // if w = 0 then the light is directional and direction specified
                            // is the negative of the direction the light is shinning
                            // if w = 1 then the light is positional
    vec4 positionOrDirection;

    // Spotlight attributes
    vec3 spotDirection;     // the direction the cone of light is shinning
    bool isSpot;                // 1 if the light is a spotlight
    float spotCutoffCos;    // Cosine of the spot cutoff angle
    float spotExponent;     // For gradual falloff near cone edge

                            // Attenuation coefficients
    float constant;
    float linear;
    float quadratic;

    bool enabled;           // true if light is "on"

};

layout(shared) uniform LightBlock
{
    GeneralLight lights[MaxLights];
};


struct Material
{
    vec4 ambientMat;
    vec4 diffuseMat;
    vec4 specularMat;
    vec4 emmissiveMat;
    float specularExp;
    int textureMode;
    bool diffuseTextureEnabled;
    bool specularTextureEnabled;
    bool normalMapEnabled;
    bool bumpMapEnabled;
};

layout(shared) uniform MaterialBlock
{
    Material object;
};

layout(shared) uniform worldEyeBlock
{
    vec3 worldEyePosition;
};

layout(location = 100) uniform sampler2D diffuseSampler;
layout(location = 101) uniform sampler2D specularSampler;

in vec3 vertexWorldPosition;
in vec3 vertexWorldNormal;
in vec2 TexCoord;

out vec4 fragmentColor;

vec3 fragmentWorldNormal;

vec3 shadingCaculation(GeneralLight light, Material mat) {
    vec3 totalLight;
    vec3 lightVector = light.positionOrDirection.xyz;
    vec3 eyeVector = worldEyePosition - vertexWorldPosition;
    float falloffFactor = 1;
    float attenuationCoffecient = 1 / (light.constant + light.linear * length(eyeVector) + light.quadratic * length(normalize(eyeVector * eyeVector)));

    totalLight = vec3(mat.emmissiveMat);
    totalLight += light.ambientColor * mat.ambientMat;      //Ambient

    if (light.isSpot) {
        falloffFactor = pow(light.spotCutoffCos, light.spotExponent);
    }
    totalLight += falloffFactor * (max(0, dot(fragmentWorldNormal, lightVector)) * light.diffuseColor * mat.diffuseMat +
                pow(max(0, dot(fragmentWorldNormal, (lightVector + eyeVector) / 2)), mat.specularExp) * light.specularColor * mat.specularMat); //Specular


    return totalLight;
}

void main()
{
    //fragmentColor = texture(diffuseSampler, TexCoord.st);

    Material material = object;
    // Substitute diffuse texture for ambient and diffuse material properties
    if (material.diffuseTextureEnabled == true && material.textureMode != 0) {

        material.diffuseMat = texture(diffuseSampler, TexCoord.st);
        material.ambientMat = material.diffuseMat;
    }

    // Substitute specular texture for specular material properties
    if (material.specularTextureEnabled == true && material.textureMode != 0) {

        material.specularMat = texture(specularSampler, TexCoord.st);
    }

    // Check if shading calculations should be performed
    if (material.textureMode == 2 || material.textureMode == 0) {

        fragmentColor = material.emmissiveMat;

        for (int i = 0; i < MaxLights; i++) {

            fragmentColor += vec4(shadingCaculation(lights[i], material), 1.0);
        }

    }
    else if (material.textureMode == 1) { // No shading calculations

        fragmentColor = texture(diffuseSampler, TexCoord.st);
    }

} // main