winix/winixd/core/timezone.h

/*
 * This file is a part of Winix
 * and is distributed under the 2-Clause BSD licence.
 * Author: Tomasz Sowa <t.sowa@ttmath.org>
 */

/* 
 * Copyright (c) 2012-2023, Tomasz Sowa
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef headerfile_winix_core_timezone
#define headerfile_winix_core_timezone

#include <ctime>
#include <map>
#include "date/date.h"
#include "space/space.h"



namespace Winix
{




class TimeZone
{
public:


	struct DstDate
	{
		enum DateType {
			ordinary_date = 0,
			first_weekday,
			last_weekday,
		};

		/*
		 * for ordinary_date
		 *
		 */
		DateType date_type;

		/*
		 * a week day (0-sunday, 1-monday, ..., 6-saturday)
		 * used when date_type is first_weekday or last_weekday
		 */
		int weekday;

		/*
		 * if date_type=ordinary_date the date is used as normal date represented in UTC time
		 * if date_type=first_weekday we are looking for a first weekday in the date.month (year will be changed)
		 * if date_type=last_weekday we are looking for the last weekady in the date.month (year will be changed)
		 */
		pt::Date date;


		DstDate();
		void Clear();
		int Compare(const pt::Date & utc_date) const;
		static pt::Date CalculateRelativeDate(int year, int month, bool is_first, int weekday, int hour, int min, int sec);
	};


	struct Dst
	{
		/*
		 * true if a time zone has daylight saving time
		 */
		bool has_dst;

		/*
		 * time zone daylight saving time (used if has_dst is true)
		 */
		DstDate start, end;

		/*
		 * time zone daylight saving time offset
		 * used when has_dst is true and the date is whithin start and end
		 * this offset should be added to time zone offset
		 */
		time_t offset;

		Dst();
		void Clear();

		/*
		 * checking whether specified 'date' is in the range of Dst
		 * has_dst must be true
		 */
		bool IsDstUsed(const pt::Date & utc_date) const;
	};


	TimeZone();

	void Clear();


	/*
		reading zime zone values from Space struct (tz_id is skipped)
		the space struct should have:
		  "tz_offset" (long)
		  "tz_has_dst" (bool)
		if tz_has_dst is true then also:
		  "tz_dst_start"  date in the following format: MM:DD HH[:MM[:SS]]
		  "tz_dst_end"    the same as above
		  "tz_dst_offset" (long)
	*/
	bool SetTz(pt::Space & space);


	/*
		 converting from UTC to local time
	*/
	time_t   CalcLocalOffset(const pt::Date & utc_date);
	time_t   ToLocal(time_t utc_time);
	pt::Date ToLocal(const pt::Date & utc_date);
	static void PrintOffset(time_t offset, pt::Stream & str); // prints the offset as [+|-]HH:MM:SS e.g.: +02:00:00

	/*
		 converting from local time to UTC
	*/
	time_t   CalcUTCOffset(const pt::Date & local_date);
	time_t   ToUTC(time_t local_time);
	pt::Date ToUTC(const pt::Date & local_date);

	// return a Dst structure for the specified year
	// or null if it not exists
	// this method can return a Dst structure for earlier year than 'year'
	// if 'year' doesn't exist
	Dst * FindDst(int year);



	// a time zone name
	// this is a key to locale
	std::wstring name;

	// each locale has its own identifier
	size_t id;

	// time zone offset (in seconds)
	time_t offset;

	// daylight saving time map
	// year -> Dst
	// if there is not a specified year we are taking the lower year, e.g.
	// if we are looking for 2010 and there is no such a year then we take 2009
	// (or 2008 if 2009 not exists etc)
	typedef std::map<int, Dst> DstMap;
	DstMap dst_map;



private:

	time_t ParseStrOffset(const wchar_t * str);
	time_t GetOffset(pt::Space & space);
	int ParseDstDateWeekday(const wchar_t * date_str, const wchar_t ** after_date_str);
	const wchar_t * SkipDstDateSeparator(const wchar_t * date_str);
	bool ParseDstDate(int year, const wchar_t * date_str, DstDate & dst_date);
	bool SetTzDst(pt::Space & year);
	static void PrintOffsetPart(long val, pt::Stream & str);

};




} // namespace Winix



#endif