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boost/date_time/local_time/local_date_time.hpp

#ifndef LOCAL_TIME_LOCAL_DATE_TIME_HPP__
#define LOCAL_TIME_LOCAL_DATE_TIME_HPP__

/* 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: 2010-01-10 14:17:23 -0500 (Sun, 10 Jan 2010) $
 */

#include <string>
#include <iomanip>
#include <sstream>
#include <stdexcept>
#include <boost/shared_ptr.hpp>
#include <boost/throw_exception.hpp>
#include <boost/date_time/time.hpp>
#include <boost/date_time/posix_time/posix_time.hpp> //todo remove?
#include <boost/date_time/dst_rules.hpp>
#include <boost/date_time/time_zone_base.hpp>
#include <boost/date_time/special_defs.hpp>
#include <boost/date_time/time_resolution_traits.hpp> // absolute_value

namespace boost {
namespace local_time {

  //! simple exception for reporting when STD or DST cannot be determined
  struct ambiguous_result : public std::logic_error
  {
    ambiguous_result (std::string const& msg = std::string()) :
      std::logic_error(std::string("Daylight Savings Results are ambiguous: " + msg)) {}
  };
  //! simple exception for when time label given cannot exist
  struct time_label_invalid : public std::logic_error
  {
    time_label_invalid (std::string const& msg = std::string()) :
      std::logic_error(std::string("Time label given is invalid: " + msg)) {}
  };
  struct dst_not_valid: public std::logic_error
  {
    dst_not_valid(std::string const& msg = std::string()) :
      std::logic_error(std::string("is_dst flag does not match resulting dst for time label given: " + msg)) {}
  };

  //TODO: I think these should be in local_date_time_base and not
  // necessarily brought into the namespace
  using date_time::time_is_dst_result;
  using date_time::is_in_dst;
  using date_time::is_not_in_dst;
  using date_time::ambiguous;
  using date_time::invalid_time_label;

  //! Representation of "wall-clock" time in a particular time zone
  /*! Representation of "wall-clock" time in a particular time zone
   * Local_date_time_base holds a time value (date and time offset from 00:00)
   * along with a time zone. The time value is stored as UTC and conversions
   * to wall clock time are made as needed. This approach allows for
   * operations between wall-clock times in different time zones, and
   * daylight savings time considerations, to be made. Time zones are
   * required to be in the form of a boost::shared_ptr<time_zone_base>.
   */
  template<class utc_time_=posix_time::ptime,
           class tz_type=date_time::time_zone_base<utc_time_,char> >
  class local_date_time_base :  public date_time::base_time<utc_time_,
                                                            boost::posix_time::posix_time_system> {
  public:
    typedef utc_time_ utc_time_type;
    typedef typename utc_time_type::time_duration_type time_duration_type;
    typedef typename utc_time_type::date_type date_type;
    typedef typename date_type::duration_type date_duration_type;
    typedef typename utc_time_type::time_system_type time_system_type;
    /*! This constructor interprets the passed time as a UTC time.
     *  So, for example, if the passed timezone is UTC-5 then the
     *  time will be adjusted back 5 hours.  The time zone allows for
     *  automatic calculation of whether the particular time is adjusted for
     *  daylight savings, etc.
     *  If the time zone shared pointer is null then time stays unadjusted.
     *@param t A UTC time
     *@param tz Timezone for to adjust the UTC time to.
     */
    local_date_time_base(utc_time_type t,
                         boost::shared_ptr<tz_type> tz) :
      date_time::base_time<utc_time_type, time_system_type>(t),
      zone_(tz)
    {
      // param was already utc so nothing more to do
    }

    /*! This constructs a local time -- the passed time information
     * understood to be in the passed tz. The DST flag must be passed
     * to indicate whether the time is in daylight savings or not.
     *  @throws -- time_label_invalid if the time passed does not exist in
     *             the given locale. The non-existent case occurs typically
     *             during the shift-back from daylight savings time.  When
     *             the clock is shifted forward a range of times
     *             (2 am to 3 am in the US) is skipped and hence is invalid.
     *  @throws -- dst_not_valid if the DST flag is passed for a period
     *             where DST is not active.
     */
    local_date_time_base(date_type d,
                         time_duration_type td,
                         boost::shared_ptr<tz_type> tz,
                         bool dst_flag) : //necessary for constr_adj()
      date_time::base_time<utc_time_type,time_system_type>(construction_adjustment(utc_time_type(d, td), tz, dst_flag)),
      zone_(tz)
    {
      if(tz != boost::shared_ptr<tz_type>() && tz->has_dst()){

        // d & td are already local so we use them
        time_is_dst_result result = check_dst(d, td, tz);
        bool in_dst = (result == is_in_dst); // less processing than is_dst()

        // ambig occurs at end, invalid at start
        if(result == invalid_time_label){
          // Ex: 2:15am local on trans-in day in nyc, dst_flag irrelevant
          std::ostringstream ss;
          ss << "time given: " << d << ' ' << td;
          boost::throw_exception(time_label_invalid(ss.str()));
        }
        else if(result != ambiguous && in_dst != dst_flag){
          // is dst_flag accurate?
          // Ex: false flag in NYC in June
          std::ostringstream ss;
          ss.setf(std::ios_base::boolalpha);
          ss << "flag given: dst=" << dst_flag << ", dst calculated: dst=" << in_dst;
          boost::throw_exception(dst_not_valid(ss.str()));
        }

        // everything checks out and conversion to utc already done
      }
    }

    //TODO maybe not the right set...Ignore the last 2 for now...
    enum DST_CALC_OPTIONS { EXCEPTION_ON_ERROR, NOT_DATE_TIME_ON_ERROR };
                            //ASSUME_DST_ON_ERROR, ASSUME_NOT_DST_ON_ERROR };

    /*! This constructs a local time -- the passed time information
     * understood to be in the passed tz.  The DST flag is calculated
     * according to the specified rule.
     */
    local_date_time_base(date_type d,
                         time_duration_type td,
                         boost::shared_ptr<tz_type> tz,
                         DST_CALC_OPTIONS calc_option) :
      // dummy value - time_ is set in constructor code
      date_time::base_time<utc_time_type,time_system_type>(utc_time_type(d,td)),
      zone_(tz)
    {
      time_is_dst_result result = check_dst(d, td, tz);
      if(result == ambiguous) {
        if(calc_option == EXCEPTION_ON_ERROR){
          std::ostringstream ss;
          ss << "time given: " << d << ' ' << td;
          boost::throw_exception(ambiguous_result(ss.str()));
        }
        else{ // NADT on error
          this->time_ = posix_time::posix_time_system::get_time_rep(date_type(date_time::not_a_date_time), time_duration_type(date_time::not_a_date_time));
        }
      }
      else if(result == invalid_time_label){
        if(calc_option == EXCEPTION_ON_ERROR){
          std::ostringstream ss;
          ss << "time given: " << d << ' ' << td;
          boost::throw_exception(time_label_invalid(ss.str()));
        }
        else{ // NADT on error
          this->time_ = posix_time::posix_time_system::get_time_rep(date_type(date_time::not_a_date_time), time_duration_type(date_time::not_a_date_time));
        }
      }
      else if(result == is_in_dst){
        utc_time_type t =
          construction_adjustment(utc_time_type(d, td), tz, true);
        this->time_ = posix_time::posix_time_system::get_time_rep(t.date(),
                                                            t.time_of_day());
      }
      else{
        utc_time_type t =
          construction_adjustment(utc_time_type(d, td), tz, false);
        this->time_ = posix_time::posix_time_system::get_time_rep(t.date(),
                                                            t.time_of_day());
      }
    }


    //! Determines if given time label is in daylight savings for given zone
    /*! Determines if given time label is in daylight savings for given zone.
     * Takes a date and time_duration representing a local time, along
     * with time zone, and returns a time_is_dst_result object as result.
     */
    static time_is_dst_result check_dst(date_type d,
                                        time_duration_type td,
                                        boost::shared_ptr<tz_type> tz)
    {
      if(tz != boost::shared_ptr<tz_type>() && tz->has_dst()) {
        typedef typename date_time::dst_calculator<date_type, time_duration_type> dst_calculator;
        return dst_calculator::local_is_dst(
            d, td,
            tz->dst_local_start_time(d.year()).date(),
            tz->dst_local_start_time(d.year()).time_of_day(),
            tz->dst_local_end_time(d.year()).date(),
            tz->dst_local_end_time(d.year()).time_of_day(),
            tz->dst_offset()
        );
      }
      else{
        return is_not_in_dst;
      }
    }

    //! Simple destructor, releases time zone if last referrer
    ~local_date_time_base() {};

    //! Copy constructor
    local_date_time_base(const local_date_time_base& rhs) :
      date_time::base_time<utc_time_type, time_system_type>(rhs),
      zone_(rhs.zone_)
    {}

    //! Special values constructor
    explicit local_date_time_base(const boost::date_time::special_values sv,
                                  boost::shared_ptr<tz_type> tz = boost::shared_ptr<tz_type>()) :
      date_time::base_time<utc_time_type, time_system_type>(utc_time_type(sv)),
      zone_(tz)
    {}

    //! returns time zone associated with calling instance
    boost::shared_ptr<tz_type> zone() const
    {
      return zone_;
    }
    //! returns false is time_zone is NULL and if time value is a special_value
    bool is_dst() const
    {
      if(zone_ != boost::shared_ptr<tz_type>() && zone_->has_dst() && !this->is_special()) {
        // check_dst takes a local time, *this is utc
        utc_time_type lt(this->time_);
        lt += zone_->base_utc_offset();
        // dst_offset only needs to be considered with ambiguous time labels
        // make that adjustment there

        switch(check_dst(lt.date(), lt.time_of_day(), zone_)){
          case is_not_in_dst:
            return false;
          case is_in_dst:
            return true;
          case ambiguous:
            if(lt + zone_->dst_offset() < zone_->dst_local_end_time(lt.date().year())) {
              return true;
            }
            break;
          case invalid_time_label:
            if(lt >= zone_->dst_local_start_time(lt.date().year())) {
              return true;
            }
            break;
        }
      }
      return false;
    }
    //! Returns object's time value as a utc representation
    utc_time_type utc_time() const
    {
      return utc_time_type(this->time_);
    }
    //! Returns object's time value as a local representation
    utc_time_type local_time() const
    {
      if(zone_ != boost::shared_ptr<tz_type>()){
        utc_time_type lt = this->utc_time() + zone_->base_utc_offset();
        if (is_dst()) {
          lt += zone_->dst_offset();
        }
        return lt;
      }
      return utc_time_type(this->time_);
    }
    //! Returns string in the form "2003-Aug-20 05:00:00 EDT"
    /*! Returns string in the form "2003-Aug-20 05:00:00 EDT". If
     * time_zone is NULL the time zone abbreviation will be "UTC". The time
     * zone abbrev will not be included if calling object is a special_value*/
    std::string to_string() const
    {
      //TODO is this a temporary function ???
      std::ostringstream ss;
      if(this->is_special()){
        ss << utc_time();
        return ss.str();
      }
      if(zone_ == boost::shared_ptr<tz_type>()) {
        ss << utc_time() << " UTC";
        return ss.str();
      }
      bool is_dst_ = is_dst();
      utc_time_type lt = this->utc_time() + zone_->base_utc_offset();
      if (is_dst_) {
        lt += zone_->dst_offset();
      }
      ss << local_time() << " ";
      if (is_dst()) {
        ss << zone_->dst_zone_abbrev();
      }
      else {
        ss << zone_->std_zone_abbrev();
      }
      return ss.str();
    }
    /*! returns a local_date_time_base in the given time zone with the
     * optional time_duration added. */
    local_date_time_base local_time_in(boost::shared_ptr<tz_type> new_tz,
                                       time_duration_type td=time_duration_type(0,0,0)) const
    {
      return local_date_time_base(utc_time_type(this->time_) + td, new_tz);
    }

    //! Returns name of associated time zone or "Coordinated Universal Time".
    /*! Optional bool parameter will return time zone as an offset
     * (ie "+07:00" extended iso format). Empty string is returned for
     * classes that do not use a time_zone */
    std::string zone_name(bool as_offset=false) const
    {
      if(zone_ == boost::shared_ptr<tz_type>()) {
        if(as_offset) {
          return std::string("Z");
        }
        else {
          return std::string("Coordinated Universal Time");
        }
      }
      if (is_dst()) {
        if(as_offset) {
          time_duration_type td = zone_->base_utc_offset();
          td += zone_->dst_offset();
          return zone_as_offset(td, ":");
        }
        else {
          return zone_->dst_zone_name();
        }
      }
      else {
        if(as_offset) {
          time_duration_type td = zone_->base_utc_offset();
          return zone_as_offset(td, ":");
        }
        else {
          return zone_->std_zone_name();
        }
      }
    }
    //! Returns abbreviation of associated time zone or "UTC".
    /*! Optional bool parameter will return time zone as an offset
     * (ie "+0700" iso format). Empty string is returned for classes
     * that do not use a time_zone */
    std::string zone_abbrev(bool as_offset=false) const
    {
      if(zone_ == boost::shared_ptr<tz_type>()) {
        if(as_offset) {
          return std::string("Z");
        }
        else {
          return std::string("UTC");
        }
      }
      if (is_dst()) {
        if(as_offset) {
          time_duration_type td = zone_->base_utc_offset();
          td += zone_->dst_offset();
          return zone_as_offset(td, "");
        }
        else {
          return zone_->dst_zone_abbrev();
        }
      }
      else {
        if(as_offset) {
          time_duration_type td = zone_->base_utc_offset();
          return zone_as_offset(td, "");
        }
        else {
          return zone_->std_zone_abbrev();
        }
      }
    }

    //! returns a posix_time_zone string for the associated time_zone. If no time_zone, "UTC+00" is returned.
    std::string zone_as_posix_string() const
    {
      if(zone_ == shared_ptr<tz_type>()) {
        return std::string("UTC+00");
      }
      return zone_->to_posix_string();
    }

    //! Equality comparison operator
    /*bool operator==(const date_time::base_time<boost::posix_time::ptime,boost::posix_time::posix_time_system>& rhs) const
    { // fails due to rhs.time_ being protected
      return date_time::base_time<boost::posix_time::ptime,boost::posix_time::posix_time_system>::operator==(rhs);
      //return this->time_ == rhs.time_;
    }*/
    //! Equality comparison operator
    bool operator==(const local_date_time_base& rhs) const
    {
      return time_system_type::is_equal(this->time_, rhs.time_);
    }
    //! Non-Equality comparison operator
    bool operator!=(const local_date_time_base& rhs) const
    {
      return !(*this == rhs);
    }
    //! Less than comparison operator
    bool operator<(const local_date_time_base& rhs) const
    {
      return time_system_type::is_less(this->time_, rhs.time_);
    }
    //! Less than or equal to comparison operator
    bool operator<=(const local_date_time_base& rhs) const
    {
      return (*this < rhs || *this == rhs);
    }
    //! Greater than comparison operator
    bool operator>(const local_date_time_base& rhs) const
    {
      return !(*this <= rhs);
    }
    //! Greater than or equal to comparison operator
    bool operator>=(const local_date_time_base& rhs) const
    {
      return (*this > rhs || *this == rhs);
    }

    //! Local_date_time + date_duration
    local_date_time_base operator+(const date_duration_type& dd) const
    {
      return local_date_time_base(time_system_type::add_days(this->time_,dd), zone_);
    }
    //! Local_date_time += date_duration
    local_date_time_base operator+=(const date_duration_type& dd)
    {
      this->time_ = time_system_type::add_days(this->time_,dd);
      return *this;
    }
    //! Local_date_time - date_duration
    local_date_time_base operator-(const date_duration_type& dd) const
    {
      return local_date_time_base(time_system_type::subtract_days(this->time_,dd), zone_);
    }
    //! Local_date_time -= date_duration
    local_date_time_base operator-=(const date_duration_type& dd)
    {
      this->time_ = time_system_type::subtract_days(this->time_,dd);
      return *this;
    }
    //! Local_date_time + time_duration
    local_date_time_base operator+(const time_duration_type& td) const
    {
      return local_date_time_base(time_system_type::add_time_duration(this->time_,td), zone_);
    }
    //! Local_date_time += time_duration
    local_date_time_base operator+=(const time_duration_type& td)
    {
      this->time_ = time_system_type::add_time_duration(this->time_,td);
      return *this;
    }
    //! Local_date_time - time_duration
    local_date_time_base operator-(const time_duration_type& td) const
    {
      return local_date_time_base(time_system_type::subtract_time_duration(this->time_,td), zone_);
    }
    //! Local_date_time -= time_duration
    local_date_time_base operator-=(const time_duration_type& td)
    {
      this->time_ = time_system_type::subtract_time_duration(this->time_,td);
      return *this;
    }
    //! local_date_time -= local_date_time --> time_duration_type
    time_duration_type operator-(const local_date_time_base& rhs) const
    {
      return utc_time_type(this->time_) - utc_time_type(rhs.time_);
    }
  private:
    boost::shared_ptr<tz_type> zone_;
    //bool is_dst_;

    /*! Adjust the passed in time to UTC?
     */
    utc_time_type construction_adjustment(utc_time_type t,
                                          boost::shared_ptr<tz_type> z,
                                          bool dst_flag)
    {
      if(z != boost::shared_ptr<tz_type>()) {
        if(dst_flag && z->has_dst()) {
          t -= z->dst_offset();
        } // else no adjust
        t -= z->base_utc_offset();
      }
      return t;
    }

    /*! Simple formatting code -- todo remove this?
     */
    std::string zone_as_offset(const time_duration_type& td,
                               const std::string& separator) const
    {
      std::ostringstream ss;
      if(td.is_negative()) {
        // a negative duration is represented as "-[h]h:mm"
        // we require two digits for the hour. A positive duration
        // with the %H flag will always give two digits
        ss << "-";
      }
      else {
        ss << "+";
      }
      ss  << std::setw(2) << std::setfill('0')
          << date_time::absolute_value(td.hours())
          << separator
          << std::setw(2) << std::setfill('0')
          << date_time::absolute_value(td.minutes());
      return ss.str();
    }
  };

  //!Use the default parameters to define local_date_time
  typedef local_date_time_base<> local_date_time;

} }


#endif