//     ____   ______ __
//    / __ \ / ____// /
//   / /_/ // /    / /
//  / ____// /___ / /___   PixInsight Class Library
// /_/     \____//_____/   PCL 2.4.23
// ----------------------------------------------------------------------------
// pcl/ProjectionBase.h - Released 2022-03-12T18:59:29Z
// ----------------------------------------------------------------------------
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// ----------------------------------------------------------------------------

#ifndef __PCL_ProjectionBase_h
#define __PCL_ProjectionBase_h

/// \file pcl/ProjectionBase.h

#include <pcl/Defs.h>

#include <pcl/Optional.h>
#include <pcl/Point.h>
#include <pcl/SphericalRotation.h>
#include <pcl/WCSKeywords.h>

/*
 * Based on original work contributed by Andrés del Pozo.
 */

namespace pcl
{

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

/*!
 * \class ProjectionBase
 * \brief Base class of all projection systems
 *
 * \ingroup astrometry_support
 */
class PCL_CLASS ProjectionBase
{
public:

   /*!
    * Virtual destructor.
    */
   virtual ~ProjectionBase()
   {
   }

   /*!
    * Returns a dynamically allocated duplicate of this object.
    */
   virtual ProjectionBase* Clone() const = 0;

   /*!
    * Returns the WCS projection identifier for this projection system.
    */
   virtual IsoString ProjCode() const = 0;

   /*!
    * Returns the readable name of this projection system.
    */
   virtual IsoString Name() const = 0;

   /*!
    * Updates the specified WCS metadata with field values corresponding to
    * this projection.
    */
   virtual void GetWCS( WCSKeywords& wcs ) const;

   /*!
    *
    */
   void InitFromRefPoint( double lng0, double lat0, const Optional<double>& phip = Optional<double>() );

   /*!
    * Transforms from celestial coordinates to world coordinates.
    */
   virtual bool Direct( DPoint& pW, const DPoint& pRD ) const noexcept
   {
      DPoint pN = m_sph.CelestialToNative( pRD );
      return IsFinite( pN.x ) && IsFinite( pN.y ) && Project( pW, pN );
   }

   /*!
    * Transforms from world coordinates to celestial coordinates.
    */
   virtual bool Inverse( DPoint& pRD, const DPoint& pW ) const noexcept
   {
      DPoint pN;
      if ( Unproject( pN, pW ) )
         if ( IsFinite( pN.x ) )
            if ( IsFinite( pN.y ) )
            {
               pRD = m_sph.NativeToCelestial( pN );
               return true;
            }
      return false;
   }

   /*!
    *
    */
   virtual bool CheckBrokenLine( const DPoint& cp1, const DPoint& cp2 ) const noexcept
   {
      return DistanceFast( m_sph.CelestialToNative( cp1 ), m_sph.CelestialToNative( cp2 ) ) < 150;
   }

   /*!
    * Returns the equatorial coordinates of the projection origin.
    */
   virtual DPoint ProjectionOrigin() const
   {
      return DPoint( Deg( m_ra0 ), Deg( m_dec0 ) );
   }

   /*!
    * Returns the distance in degrees between two locations in equatorial
    * coordinates.
    */
   static double Distance( const DPoint& p1, const DPoint& p2 )
   {
      double sinX, cosX;
      SinCos( Rad( Abs( p1.x - p2.x ) ), sinX, cosX );
      double sinY1, cosY1;
      SinCos( Rad( p1.y ), sinY1, cosY1 );
      double sinY2, cosY2;
      SinCos( Rad( p2.y ), sinY2, cosY2 );
      double K = cosY1*sinY2 - sinY1*cosY2*cosX;
      return Deg( ArcTan( Sqrt( cosY2*sinX*cosY2*sinX + K*K ), sinY1*sinY2 + cosY1*cosY2*cosX ) );
   };

   /*!
    * Returns the distance in degrees between two locations in equatorial
    * coordinates. Uses an approximate, faster algorithm.
    */
   static double DistanceFast( const DPoint& p1, const DPoint& p2 )
   {
      double sinY1, cosY1;
      SinCos( Rad( p1.y ), sinY1, cosY1 );
      double sinY2, cosY2;
      SinCos( Rad( p2.y ), sinY2, cosY2 );
      return Deg( ArcCos( sinY1*sinY2 + cosY1*cosY2*Cos( Rad( p1.x - p2.x ) ) ) );
   }

protected:

   double            m_ra0 = 0;    // radians
   double            m_dec0 = 0;   // radians
   double            m_theta0 = 0; // degrees
   double            m_phi0 = 0;   // degrees
   Optional<double>  m_lonpole;    // degrees
   Optional<double>  m_latpole;    // degrees
   SphericalRotation m_sph;

   /*!
    * Default constructor.
    */
   ProjectionBase() = default;

   /*!
    * Copy constructor.
    */
   ProjectionBase( const ProjectionBase& ) = default;

   /*!
    * Initialization from WCS metadata.
    */
   void InitFromWCS( const WCSKeywords& );

   /*!
    * Transforms from world coordinates to native spherical coordinates.
    */
   virtual bool Project( DPoint& pW, const DPoint& pN ) const noexcept = 0;

   /*!
    * Transforms from native spherical coordinates to world coordinates.
    */
   virtual bool Unproject( DPoint& pN, const DPoint& pW ) const noexcept = 0;

   friend class ProjectionFactory;
};

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

} // pcl

#endif   // __PCL_ProjectionBase_h

// ----------------------------------------------------------------------------
// EOF pcl/ProjectionBase.h - Released 2022-03-12T18:59:29Z