/*
 *	PROGRAM:	Client/Server Common Code
 *	MODULE:		timestamp.cpp
 *	DESCRIPTION:	Date/time handling class
 *
 * The contents of this file are subject to the Interbase Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy
 * of the License at http://www.Inprise.com/IPL.html
 *
 * Software distributed under the License is distributed on an
 * "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express
 * or implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code was created by Inprise Corporation
 * and its predecessors. Portions created by Inprise Corporation are
 * Copyright (C) Inprise Corporation.
 *
 * All Rights Reserved.
 * Contributor(s): ______________________________________.
 *
 * NS: The code now contains much of the logic from original gds.c
 *     this is why we need to use IPL license for it
 */

#include "firebird.h"
#include "../jrd/common.h"
#include "../jrd/dsc.h"
#include "../jrd/gdsassert.h"

#ifdef HAVE_SYS_TIMES_H
#include <sys/times.h>
#endif
#ifdef HAVE_SYS_TIMEB_H
#include <sys/timeb.h>
#endif

#include "../common/classes/timestamp.h"

namespace Firebird {

int TimeStamp::yday(const struct tm* times)
{
/**************************************
 *
 *	y d a y
 *
 **************************************
 *
 * Functional description
 *	Convert a calendar date to the day-of-year.
 *
 *	The unix time structure considers
 *	january 1 to be Year day 0, although it
 *	is day 1 of the month.   (Note that QLI,
 *	when printing Year days takes the other
 *	view.)   
 *
 **************************************/
	SSHORT day = times->tm_mday;
	const SSHORT month = times->tm_mon;
	const SSHORT year = times->tm_year + 1900;

	--day;

	day += (214 * month + 3) / 7;

	if (month < 2)
		return day;

	if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
		--day;
	else
		day -= 2;

	return day;
}


void TimeStamp::decode_date(ISC_DATE nday, struct tm* times)
{
/**************************************
 *
 *	d e c o d e _ d a t e
 *
 **************************************
 *
 * Functional description
 *	Convert a numeric day to [day, month, year].
 *
 * Calenders are divided into 4 year cycles.
 * 3 Non-Leap years, and 1 leap year.
 * Each cycle takes 365*4 + 1 == 1461 days.
 * There is a further cycle of 100 4 year cycles.
 * Every 100 years, the normally expected leap year
 * is not present.  Every 400 years it is.
 * This cycle takes 100 * 1461 - 3 == 146097 days
 * The origin of the constant 2400001 is unknown.
 * The origin of the constant 1721119 is unknown.
 * The difference between 2400001 and 1721119 is the
 * number of days From 0/0/0000 to our base date of
 * 11/xx/1858. (678882)
 * The origin of the constant 153 is unknown.
 *
 * This whole routine has problems with ndates
 * less than -678882 (Approx 2/1/0000).
 *
 **************************************/
	// struct tm may include arbitrary number of additional members.
	// zero-initialize them.
	memset(times, 0, sizeof(struct tm));

	nday -= 1721119 - 2400001;
	const SLONG century = (4 * nday - 1) / 146097;
	nday = 4 * nday - 1 - 146097 * century;
	SLONG day = nday / 4;

	nday = (4 * day + 3) / 1461;
	day = 4 * day + 3 - 1461 * nday;
	day = (day + 4) / 4;

	SLONG month = (5 * day - 3) / 153;
	day = 5 * day - 3 - 153 * month;
	day = (day + 5) / 5;

	SLONG year = 100 * century + nday;

	if (month < 10)
		month += 3;
	else {
		month -= 9;
		year += 1;
	}

	times->tm_mday = (int) day;
	times->tm_mon = (int) month - 1;
	times->tm_year = (int) year - 1900;

	times->tm_yday = yday(times);

	if ((times->tm_wday = (nday + 3) % 7) < 0)
		times->tm_wday += 7;
}


ISC_DATE TimeStamp::encode_date(const struct tm* times)
{
/**************************************
 *
 *	e n c o d e _ d a t e
 *
 **************************************
 *
 * Functional description
 *	Convert a calendar date to a numeric day
 *	(the number of days since the base date).
 *
 **************************************/
	const SSHORT day = times->tm_mday;
	SSHORT month = times->tm_mon + 1;
	SSHORT year = times->tm_year + 1900;

	if (month > 2)
		month -= 3;
	else {
		month += 9;
		year -= 1;
	}

	const SLONG c = year / 100;
	const SLONG ya = year - 100 * c;

	return (ISC_DATE) (((SINT64) 146097 * c) / 4 +
					   (1461 * ya) / 4 +
					   (153 * month + 2) / 5 + day + 1721119 - 2400001);
}

// Encode timestamp from UNIX datetime structure
void TimeStamp::encode(const struct tm* times) {
	mValue.timestamp_date = encode_date(times);
	mValue.timestamp_time =
		((times->tm_hour * 60 + times->tm_min) * 60 +
		 times->tm_sec) * ISC_TIME_SECONDS_PRECISION;
}

// Decode timestamp into UNIX datetime structure
void TimeStamp::decode(struct tm* times) const {
	decode_date(mValue.timestamp_date, times);

	const ULONG minutes = mValue.timestamp_time / (ISC_TIME_SECONDS_PRECISION * 60);
	times->tm_hour = minutes / 60;
	times->tm_min = minutes % 60;
	times->tm_sec = (mValue.timestamp_time / ISC_TIME_SECONDS_PRECISION) % 60;
}

void TimeStamp::generate()
{
	// NS: We round generated timestamps to whole millisecond.
	// Not many applications can deal with fractional milliseconds properly and
	// we do not use high resolution timers either so actual time granularity
	// is going to to be somewhere in range between 1 ms (like on UNIX/Risc) 
	// and 53 ms (such as Win9X)

	time_t seconds; // UTC time
	int fractions;  // milliseconds

#ifdef HAVE_GETTIMEOFDAY
	struct timeval tp;
	GETTIMEOFDAY(&tp);
	seconds = tp.tv_sec;
	fractions = tp.tv_usec / 1000;
#else
	struct timeb time_buffer;
	ftime(&time_buffer);
	seconds = time_buffer.time;
	fractions = time_buffer.millitm;
#endif

	// NS: Current FB behavior of using server time zone is not appropriate for 
	// distributed applications. We should be storing UTC times everywhere and
	// convert timestamps to client timezone as necessary. Replace localtime 
	// stuff with these lines as soon appropriate functionality is implemented
	//
	// mValue.timestamp_date = seconds / 86400 + GDS_EPOCH_START;
	// mValue.timestamp_time = (seconds % 86400) * ISC_TIME_SECONDS_PRECISION;

#ifdef HAVE_LOCALTIME_R
	struct tm times;
	if (!localtime_r(&seconds, &times))
		system_call_failed::raise("localtime_r");
	encode(&times);
#else
	struct tm *times = localtime(&seconds);
	if (!times)
		system_call_failed::raise("localtime");
	encode(times);
#endif

	// Add fractions of second
	mValue.timestamp_time += fractions * ISC_TIME_SECONDS_PRECISION / 1000;
}

}	// namespace