#include "light/light.h"
#include "scene/scene.h"
#include "shader/phongshader.h"

PhongShader::PhongShader(Color const &diffuseColor, float diffuseCoefficient, Color const &specularColor,
                         float specularCoefficient, float shininessExponent)
        : diffuseColor(diffuseColor), diffuseCoefficient(diffuseCoefficient), specularColor(specularColor),
          specularCoefficient(specularCoefficient), shininessExponent(shininessExponent) {}

Color PhongShader::shade(Scene const &scene, Ray const &ray) const {
    Color fragmentColor;


    for (auto &light: scene.lights()) {
        auto illum = light->illuminate(scene, ray);

        auto omegaI = normalized(illum.direction);
        auto omegaR = 2 * dotProduct(omegaI, ray.normal) * ray.normal - omegaI;
        auto cosPsi = dotProduct(ray.direction, omegaR);
        auto colorI = diffuseCoefficient * diffuseColor / PI +
                      (specularCoefficient * specularColor * std::pow(cosPsi, shininessExponent));

        fragmentColor += illum.color * colorI;
    }

    return fragmentColor;
}