#ifndef VEC3_H
#define VEC3_H

#include <cmath>
#include <iostream>

#include "util.h"

class Vec3 {
   public:
    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]; }

    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; }

    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];
    }

    inline static Vec3 random() {
        return Vec3(random_double(), random_double(), random_double());
    }

    inline static Vec3 random(double min, double max) {
        return Vec3(random_double(min, max), random_double(min, max), random_double(min, max));
    }

   private:
    double e[3];
    
    friend std::ostream& operator<<(std::ostream&, const Vec3&);
    friend Vec3 operator+(const Vec3&, const Vec3&);
    friend Vec3 operator-(const Vec3&, const Vec3&);
    friend Vec3 operator*(const Vec3&, const Vec3&);
    friend Vec3 operator*(double, const Vec3&);
    friend Vec3 operator*(const Vec3&, double);
    friend Vec3 operator/(const Vec3&, double);
    friend double dot(const Vec3&, const Vec3&);
    friend Vec3 cross(const Vec3&, const Vec3&);
    friend Vec3 unit_vector(const Vec3);
};

using Point3 = Vec3;
using Color = Vec3;

// 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 Vec3(t * v.e[0], t * v.e[1], t * v.e[2]);
}

inline Vec3 operator/(const Vec3& v, double t) {
    return (1/t) * v;
}

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];
}

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]);
}

inline Vec3 unit_vector(Vec3 v) {
    return v / v.length();
}

Vec3 random_in_unit_sphere() {
    while (true) {
        auto p = Vec3::random(-1, 1);
        if (p.length_squared() >= 1) continue;
        return p;
    }
}

Vec3 random_unit_vector() {
    auto a = random_double(0, 2*pi);
    auto z = random_double(-1, 1);
    auto r = std::sqrt(1 - z*z);
    return Vec3(r*std::cos(a), r*std::sin(a), z);
}

Vec3 random_in_hemisphere(const Vec3& normal) {
    Vec3 in_unit_sphere = random_in_unit_sphere();
    if (dot(in_unit_sphere, normal) > 0.0)
        return in_unit_sphere;
    else
        return -in_unit_sphere;
}

#endif  // VEC3_H