// * This file is part of the COLOBOT source code
// * Copyright (C) 2012, Polish Portal of Colobot (PPC)
// *
// * This program is free software: you can redistribute it and/or modify
// * it under the terms of the GNU General Public License as published by
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// * (at your option) any later version.
// *
// * This program is distributed in the hope that it will be useful,
// * but WITHOUT ANY WARRANTY; without even the implied warranty of
// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// * GNU General Public License for more details.
// *
// * You should have received a copy of the GNU General Public License
// * along with this program. If not, see  http://www.gnu.org/licenses/.

/**
 * \file math/vector.h
 * \brief Vector struct and related functions
 */

#pragma once

#include "const.h"
#include "func.h"

#include <cmath>
#include <sstream>


// Math module namespace
namespace Math
{

/** \struct Vector math/vector.h
    \brief 3D (3x1) vector

    Represents a universal 3x1 vector that can be used in OpenGL and DirectX engines.
    Contains the required methods for operating on vectors.

    All methods are made inline to maximize optimization.

    Unit tests for the structure and related functions are in module: math/test/vector_test.cpp.

 */
struct Vector
{
    //! X - 1st coord
    float x;
    //! Y - 2nd coord
    float y;
    //! Z - 3rd coord
    float z;

    //! Creates a zero vector (0, 0, 0)
    inline Vector()
    {
        LoadZero();
    }

    //! Creates a vector from given values
    inline explicit Vector(float x, float y, float z)
    {
        this->x = x;
        this->y = y;
        this->z = z;
    }

    //! Loads the zero vector (0, 0, 0)
    inline void LoadZero()
    {
        x = y = z = 0.0f;
    }

    //! Returns the struct cast to \c float* array; use with care!
    inline float* Array()
    {
        return reinterpret_cast<float*>(this);
    }

    //! Returns the struct cast to <tt>const float*</tt> array; use with care!
    inline const float* Array() const
    {
        return reinterpret_cast<const float*>(this);
    }

    //! Returns the vector length
    inline float Length() const
    {
        return sqrtf(x*x + y*y + z*z);
    }

    //! Normalizes the vector
    inline void Normalize()
    {
        float l = Length();
        if (IsZero(l))
            return;

        x /= l;
        y /= l;
        z /= l;
    }

    //! Calculates the cross product with another vector
    /** \a right right-hand side vector
            \returns the cross product*/
    inline Vector CrossMultiply(const Vector &right) const
    {
        float px = y * right.z - z * right.y;
        float py = z * right.x - x * right.z;
        float pz = x * right.y - y * right.x;
        return Vector(px, py, pz);
    }

    //! Calculates the dot product with another vector
    /** \a right right-hand side vector
            \returns the dot product */
    inline float DotMultiply(const Vector &right) const
    {
        return x * right.x + y * right.y + z * right.z;
    }

    //! Returns the cosine of angle between this and another vector
    inline float CosAngle(const Vector &right) const
    {
        return DotMultiply(right) / (Length() * right.Length());
    }

    //! Returns angle (in radians) between this and another vector
    inline float Angle(const Vector &right) const
    {
        return acos(CosAngle(right));
    }


    /* Operators */

    //! Returns the inverted vector
    inline Vector operator-() const
    {
        return Vector(-x, -y, -z);
    }

    //! Adds the given vector
    inline const Vector& operator+=(const Vector &right)
    {
        x += right.x;
        y += right.y;
        z += right.z;
        return *this;
    }

    //! Adds two vectors
    inline friend const Vector operator+(const Vector &left, const Vector &right)
    {
        return Vector(left.x + right.x, left.y + right.y, left.z + right.z);
    }

    //! Subtracts the given vector
    inline const Vector& operator-=(const Vector &right)
    {
        x -= right.x;
        y -= right.y;
        z -= right.z;
        return *this;
    }

    //! Subtracts two vectors
    inline friend const Vector operator-(const Vector &left, const Vector &right)
    {
        return Vector(left.x - right.x, left.y - right.y, left.z - right.z);
    }

    //! Multiplies by given scalar
    inline const Vector& operator*=(const float &right)
    {
        x *= right;
        y *= right;
        z *= right;
        return *this;
    }

    //! Multiplies vector by scalar
    inline friend const Vector operator*(const float &left, const Vector &right)
    {
        return Vector(left * right.x, left * right.y, left * right.z);
    }

    //! Multiplies vector by scalar
    inline friend const Vector operator*(const Vector &left, const float &right)
    {
        return Vector(left.x * right, left.y * right, left.z * right);
    }

    //! Divides by given scalar
    inline const Vector& operator/=(const float &right)
    {
        x /= right;
        y /= right;
        z /= right;
        return *this;
    }

    //! Divides vector by scalar
    inline friend const Vector operator/(const Vector &left, const float &right)
    {
        return Vector(left.x / right, left.y / right, left.z / right);
    }


    //! Returns a string "[x, y, z]"
    inline std::string ToString() const
    {
        std::stringstream s;
        s.precision(3);
        s << "[" << x << ", " << y << ", " << z << "]";
        return s.str();
    }

}; // struct Point

//! Checks if two vectors are equal within given \a tolerance
inline bool VectorsEqual(const Math::Vector &a, const Math::Vector &b, float tolerance = TOLERANCE)
{
    return IsEqual(a.x, b.x, tolerance)
            && IsEqual(a.y, b.y, tolerance)
            && IsEqual(a.z, b.z, tolerance);
}

//! Convenience function for getting normalized vector
inline Vector Normalize(const Math::Vector &v)
{
    Vector result = v;
    result.Normalize();
    return result;
}

//! Convenience function for calculating dot product
inline float DotProduct(const Math::Vector &left, const Math::Vector &right)
{
    return left.DotMultiply(right);
}

//! Convenience function for calculating cross product
inline Vector CrossProduct(const Math::Vector &left, const Math::Vector &right)
{
    return left.CrossMultiply(right);
}

//! Convenience function for calculating angle (in radians) between two vectors
inline float Angle(const Math::Vector &a, const Math::Vector &b)
{
    return a.Angle(b);
}

//! Returns the distance between the ends of two vectors
inline float Distance(const Math::Vector &a, const Math::Vector &b)
{
    return sqrtf( (a.x-b.x)*(a.x-b.x) +
                  (a.y-b.y)*(a.y-b.y) +
                  (a.z-b.z)*(a.z-b.z) );
}

}; // namespace Math