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// *
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// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// * GNU General Public License for more details.
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/** @defgroup MathVectorModule math/vector.h
   Contains the Vector struct and related functions.
 */

#pragma once

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

#include <cmath>


// Math module namespace
namespace Math
{

/* @{ */ // start of group

/** \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 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);
  }

}; // struct Point

//! Checks if two vectors are equal within given \a tolerance
inline bool VectorsEqual(const Vector &a, const 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 Vector &v)
{
  Vector result = v;
  result.Normalize();
  return result;
}

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

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

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

//! Returns the distance between the ends of two vectors
inline float Distance(const Vector &a, const 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) );
}

/* @} */ // end of group

}; // namespace Math