/*
 * Created by Brett Terpstra 6920201 on 14/10/22.
 * Copyright (c) Brett Terpstra 2022 All Rights Reserved
 */

#ifndef STEP_2_VECTORS_H
#define STEP_2_VECTORS_H

#include <cmath>
#include "util/std.h"

namespace Raytracing {

    // when running on the CPU it's fine to be a double
    // if your CPU is older (32bit) and has issues with doubles, consider changing it to a float
    // but if we move to the GPU it has to be a float.
    // since GPUs generally are far more optimized for floats
    typedef double PRECISION_TYPE;

    class Vec4 {
        private:
            union xType {
                PRECISION_TYPE x;
                PRECISION_TYPE r;
            };
            union yType {
                PRECISION_TYPE y;
                PRECISION_TYPE g;
            };
            union zType {
                PRECISION_TYPE z;
                PRECISION_TYPE b;
            };
            union wType {
                PRECISION_TYPE w;
                PRECISION_TYPE a;
            };

            struct valueType {
                xType v1;
                yType v2;
                zType v3;
                wType v4;
            };
            // isn't much of a reason to do it this way
            // beyond I wanted an explicit immutable vector type of length 4
            // that could be used as both x,y,z + w? and rgba
            // it's unlikely that we'll need to use the w component
            // but it helps better line up with the GPU
            // and floating point units (especially on GPUs) tend to be aligned to 4*sizeof(float)
            valueType value;
        public:
            Vec4(): value{0, 0, 0, 0} {}
            Vec4(PRECISION_TYPE x, PRECISION_TYPE y, PRECISION_TYPE z): value{x, y, z, 0} {}
            Vec4(PRECISION_TYPE x, PRECISION_TYPE y, PRECISION_TYPE z, PRECISION_TYPE w): value{x, y, z, w} {}
            Vec4(const Vec4& vec): value{vec.x(), vec.y(), vec.z(), vec.w()} {}


            // most of the modern c++ here is because clang tidy was annoying me
            [[nodiscard]] inline PRECISION_TYPE x() const { return value.v1.x; }

            [[nodiscard]] inline PRECISION_TYPE y() const { return value.v2.y; }

            [[nodiscard]] inline PRECISION_TYPE z() const { return value.v3.z; }

            [[nodiscard]] inline PRECISION_TYPE w() const { return value.v4.w; }

            [[nodiscard]] inline PRECISION_TYPE r() const { return value.v1.r; }

            [[nodiscard]] inline PRECISION_TYPE g() const { return value.v2.g; }

            [[nodiscard]] inline PRECISION_TYPE b() const { return value.v3.b; }

            [[nodiscard]] inline PRECISION_TYPE a() const { return value.v4.a; }

            // negation operator
            Vec4 operator-() const { return {-x(), -y(), -z(), -w()}; }

            [[nodiscard]] inline PRECISION_TYPE magnitude() const {
                return sqrt(lengthSquared());
            }

            [[nodiscard]] inline PRECISION_TYPE lengthSquared() const {
                return x() * x() + y() * y() + z() * z() + w() * w();
            }

            // returns the unit-vector.
            [[nodiscard]] inline Vec4 normalize() const {
                PRECISION_TYPE mag = magnitude();
                return {x() / mag, y() / mag, z() / mag, w() / mag};
            }

            // add operator before the vec returns the magnitude
            PRECISION_TYPE operator+() const {
                return magnitude();
            }

            // preforms the dot product of left * right
            static inline PRECISION_TYPE dot(const Vec4& left, const Vec4& right) {
                return left.x() * right.x()
                       + left.y() * right.y()
                       + left.z() * right.z();
            }

            // preforms the cross product of left X right
            // since a general solution to the cross product doesn't exist in 4d
            // we are going to ignore the w.
            static inline Vec4 cross(const Vec4& left, const Vec4& right) {
                return {left.y() * right.z() - left.z() * right.y(),
                        left.z() * right.x() - left.x() * right.z(),
                        left.x() * right.y() - left.y() * right.x()};
            }

    };

// Utility Functions

    // useful for printing out the vector to stdout
    inline std::ostream& operator<<(std::ostream& out, const Vec4& v) {
        return out << "Vec4{" << v.x() << ", " << v.y() << ", " << v.z() << ", " << v.w() << "} ";
    }

    // adds the two vectors left and right
    inline Vec4 operator+(const Vec4& left, const Vec4& right) {
        return {left.x() + right.x(), left.y() + right.y(), left.z() + right.z(), left.w() + right.w()};
    }

    // subtracts the right vector from the left.
    inline Vec4 operator-(const Vec4& left, const Vec4& right) {
        return {left.x() - right.x(), left.y() - right.y(), left.z() - right.z(), left.w() - right.w()};
    }

    // multiples the left with the right
    inline Vec4 operator*(const Vec4& left, const Vec4& right) {
        return {left.x() * right.x(), left.y() * right.y(), left.z() * right.z(), left.w() * right.w()};
    }

    // divides each element individually
    inline Vec4 operator/(const Vec4& left, const Vec4& right) {
        return {left.x() / right.x(), left.y() / right.y(), left.z() / right.z(), left.w() / right.w()};
    }

    // multiplies the const c with each element in the vector v
    inline Vec4 operator*(const PRECISION_TYPE c, const Vec4& v) {
        return {c * v.x(), c * v.y(), c * v.z(), c * v.w()};
    }

    // same as above but for right sided constants
    inline Vec4 operator*(const Vec4& v, PRECISION_TYPE c) {
        return c * v;
    }

    // divides the vector by the constant c
    inline Vec4 operator/(const Vec4& v, PRECISION_TYPE c) {
        return {v.x() / c, v.y() / c, v.z() / c, v.w() / c};
    }

    // divides each element in the vector by over the constant
    inline Vec4 operator/(PRECISION_TYPE c, const Vec4& v) {
        return {c / v.x(), c / v.y(), c / v.z(), c / v.w()};
    }

    class Ray {
        private:
            // the starting point for our ray
            Vec4 start;
            // and the direction it is currently traveling
            Vec4 direction;
            Vec4 inverseDirection;
        public:
            Ray(const Vec4& start, const Vec4& direction): start(start), direction(direction), inverseDirection(1 / direction) {}

            [[nodiscard]] Vec4 getStartingPoint() const { return start; }

            [[nodiscard]] Vec4 getDirection() const { return direction; }

            // not always needed, but it's good to not have to calculate the inverse inside the intersection
            // as that would be very every AABB, and that is expensive
            [[nodiscard]] Vec4 getInverseDirection() const {return inverseDirection; }

            // returns a point along the ray, extended away from start by the length.
            [[nodiscard]] inline Vec4 along(PRECISION_TYPE length) const { return start + length * direction; }

    };

    inline std::ostream& operator<<(std::ostream& out, const Ray& v) {
        return out << "Ray{" << v.getStartingPoint() << " " << v.getDirection() << "} ";
    }

}

#endif //STEP_2_VECTORS_H