vec3.h

//
// Created by Jorge on 12/16/2024.
//

#ifndef VEC3_H
#define VEC3_H

#include <cmath>
#include <iostream>

class vec3 {
public:
    double e[3];
    vec3() : e{0,0,0} {}
    vec3(double e0, double e1, double e2) : e{e0, e1, e2} {};

    double x() const {return e[0];}
    double y() const {return e[1];}
    double z() const {return e[2];}

    // operator overloading

    vec3 operator-() const {return vec3(-e[0], -e[1], -e[2]);}
    double operator[](int i) const {return e[i];}
    double& operator[](int i) {return e[i];}

    //+=
    vec3& operator+=(const vec3 &v) {
        e[0] += v.e[0];
        e[1] += v.e[1];
        e[2] += v.e[2];

        return *this;
    }

    // *=
    vec3& operator*=(const double t) {
        e[0] *= t;
        e[1] *= t;
        e[2] *= t;

        return *this;
    }

    // /=
    vec3& operator/=(const double t) {
        return *this *= 1/t;
    }

    // length and length_squared
    double length() const {
        return std::sqrt(length_squared());
    }

    double length_squared() const {
        return e[0]*e[0] + e[1]*e[1] + e[2]*e[2];
    }

    static vec3 random()
    {
        return vec3(random_double(), random_double(), random_double());
    }

    static vec3 random(double min, double max)
    {
        return vec3(random_double(min, max), random_double(min, max), random_double(min, max));
    }

};

// type aliases for vec3
using point3 = vec3; // 3D point
using color = vec3;


// utility functions

inline std::ostream& operator<<(std::ostream &out, const vec3 &v) {
    return out << v.e[0] << ' ' << v.e[1] << ' ' << v.e[2];
}

inline vec3 operator+(const vec3 &u, const vec3 &v) {
    return vec3(u.e[0] + v.e[0], u.e[1] + v.e[1], u.e[2] + v.e[2]);
}

inline vec3 operator-(const vec3 &u, const vec3 &v) {
    return vec3(u.e[0] - v.e[0], u.e[1] - v.e[1], u.e[2] - v.e[2]);
}

inline vec3 operator*(const vec3 &u, const vec3 &v) {
    return vec3(u.e[0] * v.e[0], u.e[1] * v.e[1], u.e[2] * v.e[2]);
}

inline vec3 operator*(double t, const vec3 &v) {
    return vec3(t*v.e[0], t*v.e[1], t*v.e[2]);
}

inline vec3 operator*(const vec3 &v, double t) {
    return t * v;
}

inline vec3 operator/(vec3 v, double t) {
    return (1/t) * v;
}

// dot product
inline double dot(const vec3 &u, const vec3 &v) {
    return u.e[0]*v.e[0] + u.e[1]*v.e[1] + u.e[2]*v.e[2];
}

// cross product
inline vec3 cross(const vec3 &u, const vec3 &v) {
    return vec3(u.e[1]*v.e[2] - u.e[2]*v.e[1],
                u.e[2]*v.e[0] - u.e[0]*v.e[2],
                u.e[0]*v.e[1] - u.e[1]*v.e[0]);
}

// unit vector
inline vec3 unit_vector(const vec3& v) {
    return v / v.length();
}

inline vec3 random_unit_vector() {
    while (true)
    {
        auto p = vec3::random(-1, 1);
        auto lensq = p.length_squared();
        if (1e-160 < lensq && lensq <= 1) return p / std::sqrt(lensq);
    }
}

inline vec3 random_on_hemisphere(const vec3& normal)
{
    auto in_unit_sphere = random_unit_vector();
    if (dot(in_unit_sphere, normal) > 0.0)
    {
        return in_unit_sphere;
    } else {
        return -in_unit_sphere;
    }
}




#endif //VEC3_H