#pragma once

#include <glm/glm.hpp>

namespace Donut
{
    class Ray
    {
    public:
        glm::vec3 m_direction;
        glm::vec3 m_origin;

        Ray(glm::vec3 o, glm::vec3 d) 
            : m_origin(o), 
              m_direction(glm::normalize(d)) { }
    };

    class Material
    {
    public:
        glm::vec3 m_color;
        float     m_specular;
        float     m_emission;

        Material(glm::vec3 c, float s, float e)
            : m_color(c), 
              m_specular(s), 
              m_emission(e) { }
    };

    class Object
    {
    public:
        glm::vec3 m_centre;
        float     m_radius;
        Material  m_material;
    
        Object(glm::vec3 c, float r, Material m) 
            : m_centre(c), 
              m_radius(r), 
              m_material(m) { }
    
        bool intersect(Ray &ray, float &t)
        {
            glm::vec3 oc = ray.m_origin - m_centre;
            float a = glm::dot(ray.m_direction, ray.m_direction); 
            float b = 2.0f * glm::dot(oc, ray.m_direction);
            float c = glm::dot(oc, oc) - m_radius * m_radius;
            double discriminant = b*b - 4*a*c;

            if(discriminant < 0)
                return false;
    
            float intercept = (-b - sqrt(discriminant)) / (2.0f*a);
            if(intercept < 0)
            {
                intercept = (-b + sqrt(discriminant)) / (2.0f*a);
                if(intercept<0)
                    return false;
            }

            t = intercept;
            return true;
        }
    
        glm::vec3 get_normal(glm::vec3 &point) const
        {
            return glm::normalize(point - m_centre);
        }
    };
};