#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_AREAS_TRACERS_DISC2TRACER_H
#define NUCLEX_GEOMETRY_AREAS_TRACERS_DISC2TRACER_H

#include "Nuclex/Geometry/Config.h"
#include "Nuclex/Geometry/Areas/Disc2.h"
#include "Nuclex/Geometry/Lines/Line2.h"
#include "Nuclex/Geometry/LineContacts.h"

namespace Nuclex { namespace Geometry { namespace Areas { namespace Tracers {

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

  /// <summary>Determines contacts between lines and 2D discs</summary>
  template <typename TScalar>
  class Disc2Tracer {

    /// <summary>Determines where a line enters and where it exits a disc</summary>
    /// <param name="line">
    ///   Line whose entry and exit through the disc will be determined
    /// </param>
    /// <param name="disc">Disc the line will be checked against</param>
    /// <returns>The times at which the line enters and leaves the disc</returns>
    public: static LineContacts<TScalar> FindLineContacts(
      const Lines::Line2<TScalar> &line, const Disc2<TScalar> &disc
    ) {
      Vector2<TScalar> offset = line.Origin - disc.Center;
      float dot = Vector2<TScalar>::Dot(line.Direction, offset);
      
      float lineDistanceSquared = (offset.GetSquaredLength() - (disc.Radius * disc.Radius));
      float discrete = (dot * dot) - lineDistanceSquared;
      if(discrete > 0) {
        discrete = Math<TScalar>::SquareRoot(discrete);
        return LineContacts<TScalar>(-dot - discrete, -dot + discrete);
      } else {
        return LineContacts<TScalar>::None;
      }
    }

  };

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

}}}} // namespace Nuclex::Geometry::Areas::Tracers

#endif // NUCLEX_GEOMETRY_AREAS_TRACERS_DISC2TRACER_H