class QgsCoordinateTransformCache
{
%TypeHeaderCode
#include <qgscrscache.h>
%End
  public:
    static QgsCoordinateTransformCache* instance();

    ~QgsCoordinateTransformCache();
    /** Returns coordinate transformation. Cache keeps ownership
        @param srcAuthId auth id string of source crs
        @param destAuthId auth id string of dest crs
        @param srcDatumTransform id of source's datum transform
        @param destDatumTransform id of destinations's datum transform
     */
    const QgsCoordinateTransform* transform( const QString& srcAuthId, const QString& destAuthId, int srcDatumTransform = -1, int destDatumTransform = -1 );
    /** Removes transformations where a changed crs is involved from the cache*/
    void invalidateCrs( const QString& crsAuthId );

  private:

    QgsCoordinateTransformCache( const QgsCoordinateTransformCache& rh );
};

/** \ingroup core
 * \class QgsCRSCache
 * \brief Caches QgsCoordinateReferenceSystem construction, which may be expensive.
 *
 * QgsCRSCache maintains a cache of previously constructed coordinate systems, so that
 * creating a new CRS from the cache can reuse previously calculated parameters. The
 * constructors for QgsCoordinateReferenceSystem can be expensive, so it's recommended
 * to use QgsCRSCache instead of directly calling the QgsCoordinateReferenceSystem
 * constructors.
 */

class QgsCRSCache
{
%TypeHeaderCode
#include <qgscrscache.h>
%End

  public:

    //! Returns a pointer to the QgsCRSCache singleton
    static QgsCRSCache* instance();

    /** Returns the CRS for authid, e.g. 'EPSG:4326' (or an invalid CRS in case of error)
     * @deprecated use crsByOgcWmsCrs() instead
    */
    QgsCoordinateReferenceSystem crsByAuthId( const QString& authid ) /Deprecated/;

    /** Returns the CRS from a given OGC WMS-format Coordinate Reference System string.
     * @param ogcCrs OGR compliant CRS definition, eg "EPSG:4326"
     * @returns matching CRS, or an invalid CRS if string could not be matched
     * @note added in QGIS 2.16
     * @see QgsCoordinateReferenceSystem::createFromOgcWmsCrs()
    */
    QgsCoordinateReferenceSystem crsByOgcWmsCrs( const QString& ogcCrs ) const;

    /** Returns the CRS from a given EPSG ID.
     * @param epsg epsg CRS ID
     * @returns matching CRS, or an invalid CRS if string could not be matched
    */
    QgsCoordinateReferenceSystem crsByEpsgId( long epsg ) const;

    /** Returns the CRS from a proj4 style formatted string.
     * @param proj4 proj4 format string
     * @returns matching CRS, or an invalid CRS if string could not be matched
     * @note added in QGIS 2.16
     * @see QgsCoordinateReferenceSystem::createFromProj4()
    */
    QgsCoordinateReferenceSystem crsByProj4( const QString& proj4 ) const;

    /** Updates the cached definition of a CRS. Should be called if the definition of a user-created
     * CRS has been changed.
     * @param authid CRS auth ID, eg "EPSG:4326" or "USER:100009"
     */
    void updateCRSCache( const QString& authid );

  protected:
    QgsCRSCache();

};