/*
 * Copyright 2003,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#include <log4cxx/helpers/timezone.h>
#include <locale>


int getYear(int64_t date)
{
	time_t d = (time_t)(date / 1000);
	return ::localtime(&d)->tm_year;
}

using namespace log4cxx;
using namespace log4cxx::helpers;

IMPLEMENT_LOG4CXX_OBJECT(TimeZone)

TimeZonePtr TimeZone::defaultTimeZone = new TimeZone(_T(""));

TimeZone::TimeZone(const String& ID)
: ID(ID), rawOffset(0), DSTSavings(0)
{
	String timeZoneEnv = _T("TZ=") + ID;

	USES_CONVERSION;
	::putenv((char *)T2A(timeZoneEnv.c_str()));
	tzset();

	time_t now = time(0);
	tm localNow = *::localtime(&now);
	tm utcNow = *::gmtime(&now);
	rawOffset = (int)::difftime(::mktime(&localNow), ::mktime(&utcNow)) * 1000;
	
	int year = localNow.tm_year;
	Rule * rule = new Rule(year);
	
	// we check if we found a daylight time
	if (rule->startDate != 0 && rule->endDate != 0)
	{
		// since we have computed a rule, we store it
		rules.insert(RuleMap::value_type(year, rule));
		DSTSavings = 3600 * 1000; // 1 hour
	}
	else
	{
		delete rule;
	}
}

TimeZone::~TimeZone()
{
	for (RuleMap::iterator it = rules.begin(); it != rules.end(); it++)
	{
		Rule * rule = it->second;
		delete rule;
	}
}

int TimeZone::getOffset(int64_t date) const
{
	if (inDaylightTime(date))
	{
		return rawOffset + DSTSavings;
	}
	else
	{
		return rawOffset;
	}
}

TimeZonePtr TimeZone::getDefault()
{
	return defaultTimeZone;
}

TimeZonePtr TimeZone::getTimeZone(const String& ID)
{
	return new TimeZone(ID);
}

bool TimeZone::inDaylightTime(int64_t date) const
{
	if (!useDaylightTime())
	{
		return false;
	}
	
	time_t d = (time_t)(date / 1000);
	int year = ::localtime(&d)->tm_year;

	RuleMap::iterator it = rules.find(year);
	if (it == rules.end())
	{
		synchronized sync(this);

		it = rules.find(year);
		if (it == rules.end())
		{
			it = rules.insert(RuleMap::value_type(
				year, new Rule(year))).first;
		}
	}

	Rule * rule = it->second;
	return (date >= rule->startDate && date < rule->endDate);
}

TimeZone::Rule::Rule(int year)
: startDate(0), endDate(0)
{
	tm tm;
	memset (&tm, 0, sizeof (tm));
	tm.tm_mday = 1;
	tm.tm_year = year;
	
	time_t t = ::mktime(&tm);
	int isDST, day, hour, min;

	for (day = 0; day < 365; day++)
	{
		t += 60 * 60 * 24;
		
		isDST = ::localtime(&t)->tm_isdst;
		if (startDate == 0)
		{
			if (isDST > 0)
			{
				t -= 60 * 60 * 24;
	
				for (hour = 0; hour < 24; hour++)
				{
					t += 60 * 60;
	
					isDST = ::localtime(&t)->tm_isdst;
					if (isDST > 0)
					{
						t -= 60 * 60;
						for (min = 0; min < 60; min++)
						{
							t += 60;
							isDST = ::localtime(&t)->tm_isdst;
							if (isDST > 0)
							{
								startDate = (int64_t)t * 1000;
								break;
							}
						}
						
						break;
					}
				}
			}
		}
		else if (isDST == 0)
		{
			t -= 60 * 60 * 24;

			for (hour = 0; hour < 24; hour++)
			{
				t += 60 * 60;

				isDST = ::localtime(&t)->tm_isdst;
				if (isDST == 0)
				{
					t -= 60 * 60;
					for (min = 0; min < 60; min++)
					{
						t += 60;
						isDST = ::localtime(&t)->tm_isdst;
						if (isDST == 0)
						{
							endDate = (int64_t)t * 1000;
							break;
						}
					}
					
					break;
				}
			}
			
			if (endDate != 0)
			{
				break;
			}
		}
	}
}