#pragma region CPL License
/*
Nuclex Native Framework
Copyright (C) 2002-2015 Nuclex Development Labs

This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.

This library 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
IBM Common Public License for more details.

You should have received a copy of the IBM Common Public
License along with this library
*/
#pragma endregion // CPL License

#ifndef NUCLEX_GEOMETRY_LINES_SEGMENT2_H
#define NUCLEX_GEOMETRY_LINES_SEGMENT2_H

#include "Nuclex/Geometry/Config.h"
#include "Nuclex/Geometry/Point2.h"
#include "Nuclex/Geometry/Vector2.h"
#include "Nuclex/Geometry/Side2.h"

#include <algorithm>
#include <stdexcept>

namespace Nuclex { namespace Geometry { namespace Lines {

  // ------------------------------------------------------------------------------------------- //

  /// <summary>2D line segment defined by a start and an end point</summary>
  template <typename TScalar>
  struct Segment2 {
  
    /// <summary>Initializes a line segment using the specified coordinates</summary>
    /// <param name="start">Position at which the line segment begins</param>
    /// <param name="end">Position at which the line segment ends</param>
    public: Segment2(const Point2<TScalar> &start, const Point2<TScalar> &end) :
      Start(start), End(end) {}

    /// <summary>Returns the squared length of the line segment</summary>
    /// <returns>The squared length of the line segment</returns>
    public: TScalar GetSquaredLength() const {
      TScalar distanceX = this->End.X - this->Start.X;
      TScalar distanceY = this->End.Y - this->Start.Y;
      return (distanceX * distanceX) + (distanceY * distanceY);
    }

    /// <summary>Returns the length of the line segment</summary>
    /// <returns>The length of the line segment</returns>
    public: TScalar GetLength() const {
      return Math<TScalar>::SquareRoot(GetSquaredLength());
    }

    /// <summary>Offsets the entire line segment by the specified amount</summary>
    /// <param name="offsetX">Amount the line segment will be offset on the X axis</param>
    /// <param name="offsetY">Amount the line segment will be offset on the Y axis</param>
    public: void ShiftBy(TScalar offsetX, TScalar offsetY) {
      this->Start.X += offsetX;
      this->Start.Y += offsetY;
      this->End.X += offsetX;
      this->End.Y += offsetY;
    }

    /// <summary>Offsets the entire line segment by the specified amount</summary>
    /// <param name="offset">Amount the line segment will be offset</param>
    public: void ShiftBy(const Vector2<TScalar> &offset) {
      this->Start += offset;
      this->End += offset;
    }

    /// <summary>Determines which side of the line segment a point is on</summary>
    /// <param name="point">Point that will be checked</param>
    /// <returns>The side of the line the point is on</returns>
    /// <remarks>
    ///   There is no colinear / dead center case. Lines are infinitely thin and any check
    ///   for hitting the center would be prone to the same problems as comparing a floating
    ///   point variable to an exact value. Thus the point is either left or right or the
    ///   line, removing silly special handling code and increasing robustness.
    /// </remarks>
    public: Side2::Enum GetSide(const Point2<TScalar> &point) {
      return GetSide(point.X, point.Y);
    }

    /// <summary>Determines which side of the line segment a point is on</summary>
    /// <param name="pointX">X coordinate of the point that will be checked</param>
    /// <param name="pointY">Y coordinate of the point that will be checked</param>
    /// <returns>The side of the line the point is on</returns>
    /// <remarks>
    ///   There is no colinear / dead center case. Lines are infinitely thin and any check
    ///   for hitting the center would be prone to the same problems as comparing a floating
    ///   point variable to an exact value. Thus the point is either left or right or the
    ///   line, removing silly special handling code and increasing robustness.
    /// </remarks>
    public: Side2::Enum GetSide(TScalar pointX, TScalar pointY) {
      TScalar determinant =
        (this->End.X - this->Start.X) * (pointY - this->Start.Y) -
        (pointX - this->Start.X) * (this->End.Y - this->Start.Y);

      if(determinant >= 0) {
        return Side2::LeftHandSide;
      } else {
        return Side2::RightHandSide;
      }
    }

    /// <summary>Coordinates at which the line segment begins</summary>
    public: Point2<TScalar> Start;
    /// <summary>Coordinates at which the line segment ends</summary>
    public: Point2<TScalar> End;

  };

  // ------------------------------------------------------------------------------------------- //

}}} // namespace Nuclex::Geometry::Lines

#endif // NUCLEX_GEOMETRY_LINES_SEGMENT2_H