#include "Lighting.h"
#include <math.h>               /* pow() */

Color Lighting::computePhong(const Material & material,
                             const std::vector<Light *> & lights,
                             const Ray & viewRay,
                             const Vector & surfacePoint,
                             const Vector & surfaceNormal,
                             const Color & ambientLight)
{
    Color result = ambientLight;

    Vector viewDirection = -viewRay.getDirection();
    double shininess = material.getShininess();
    const Color & diffuseColor = material.getDiffuseColor();
    const Color & specularColor = material.getSpecularColor();

    for (std::vector<Light *>::const_iterator it = lights.begin();
         it != lights.end();
         it++)
    {
        Vector directionToLight = (*it)->getPosition() - surfacePoint;
        directionToLight.normalize();
        Vector reflectedLightDirection =
            directionToLight.reflect(surfaceNormal);

        /* calculate the diffuse term */
        result += diffuseColor
                * (*it)->getDiffuseColor()
                * (directionToLight % surfaceNormal);

        /* calculate the specular term */
        result += specularColor
                * (*it)->getSpecularColor()
                * pow(reflectedLightDirection % viewDirection, shininess);
    }

    return result;
}