#ifndef _DATE_TIME_TIME_ZONE_BASE__

#define _DATE_TIME_TIME_ZONE_BASE__

/* Copyright (c) 2003-2005 CrystalClear Software, Inc.

 * Subject to the Boost Software License, Version 1.0. 

 * (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)

 * Author: Jeff Garland, Bart Garst

 * $Date: 2008-02-27 15:00:24 -0500 (Wed, 27 Feb 2008) $

 */

#include <string>

#include <sstream>

namespace boost {

namespace date_time {

  //! Interface class for dynamic time zones.

  /*! This class represents the base interface for all timezone

   *  representations.  Subclasses may provide different systems

   *  for identifying a particular zone.  For example some may

   *  provide a geographical based zone construction while others

   *  may specify the offset from GMT.  Another possible implementation

   *  would be to convert from POSIX timezone strings.  Regardless of

   *  the construction technique, this is the interface that these

   *  time zone types must provide.

   * 

   * Note that this class is intended to be used as a shared

   * resource (hence the derivation from boost::counted_base.  

   */

  template<typename time_type, typename CharT>

  class time_zone_base  {

  public:

    typedef CharT char_type;

    typedef std::basic_string<CharT> string_type;

    typedef std::basic_ostringstream<CharT> stringstream_type;

    typedef typename time_type::date_type::year_type year_type;

    typedef typename time_type::time_duration_type time_duration_type;

    time_zone_base() {};

    virtual ~time_zone_base() {};

    //!String for the timezone when in daylight savings (eg: EDT)

    virtual string_type dst_zone_abbrev() const=0;

    //!String for the zone when not in daylight savings (eg: EST)

    virtual string_type std_zone_abbrev() const=0;

    //!String for the timezone when in daylight savings (eg: Eastern Daylight Time)

    virtual string_type dst_zone_name() const=0;

    //!String for the zone when not in daylight savings (eg: Eastern Standard Time)

    virtual string_type std_zone_name() const=0;

    //! True if zone uses daylight savings adjustments otherwise false

    virtual bool has_dst() const=0;

    //! Local time that DST starts -- undefined if has_dst is false

    virtual time_type dst_local_start_time(year_type y) const=0;

    //! Local time that DST ends -- undefined if has_dst is false

    virtual time_type dst_local_end_time(year_type y) const=0;

    //! Base offset from UTC for zone (eg: -07:30:00)

    virtual time_duration_type base_utc_offset() const=0;

    //! Adjustment forward or back made while DST is in effect

    virtual time_duration_type dst_offset() const=0;

    //! Returns a POSIX time_zone string for this object

    virtual string_type to_posix_string() const =0;

  private:

  };

  //! Structure which holds the time offsets associated with daylight savings time

  /*!

   *@param time_duration_type A type used to represent the offset

   */

  template<class time_duration_type>

  class dst_adjustment_offsets

  {

  public:

    dst_adjustment_offsets(const time_duration_type& dst_adjust,

                           const time_duration_type& dst_start_offset,

                           const time_duration_type& dst_end_offset) :

      dst_adjust_(dst_adjust),

      dst_start_offset_(dst_start_offset),

      dst_end_offset_(dst_end_offset)

    {}

    //! Amount DST adjusts the clock eg: plus one hour

    time_duration_type dst_adjust_;

    //! Time past midnight on start transition day that dst starts

    time_duration_type dst_start_offset_;

    //! Time past midnight on end transition day that dst ends

    time_duration_type dst_end_offset_;

  };

} } //namespace date_time

#endif