/*
 * 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.
 *
 */

#include "timezone.h"
#include "misc.h"


namespace Winix
{


TimeZone::DstDate::DstDate()
{
	Clear();
}


void TimeZone::DstDate::Clear()
{
	date_type = ordinary_date;
	weekday = 0;
	date.Clear();
}



int TimeZone::DstDate::Compare(const pt::Date & utc_date) const
{
	int res = 0;

	if( date_type == ordinary_date )
	{
		res = date.Compare(utc_date, true);
	}
	else
	if( date_type == first_weekday )
	{
		pt::Date tmp_date = CalculateRelativeDate(utc_date.year, date.month, true, weekday, date.hour, date.min, date.sec);
		res = tmp_date.Compare(utc_date, true);
	}
	else
	if( date_type == last_weekday )
	{
		pt::Date tmp_date = CalculateRelativeDate(utc_date.year, date.month, false, weekday, date.hour, date.min, date.sec);
		res = tmp_date.Compare(utc_date, true);
	}

	return res;
}


pt::Date TimeZone::DstDate::CalculateRelativeDate(int year, int month, bool is_first, int weekday, int hour, int min, int sec)
{
	pt::Date new_date;
	new_date.year = year;
	new_date.month = month;
	new_date.hour = hour;
	new_date.min = min;
	new_date.sec = sec;

	if( is_first )
	{
		new_date.day = 1;
		int w = new_date.WeekDay();

		if( w < weekday )
		{
			new_date.day += (weekday - w);
		}
		else
		if( w > weekday )
		{
			new_date.day += (weekday - w) + 7;
		}
	}
	else
	{
		new_date.day = pt::Date::MonthLen(new_date.year, new_date.month);
		int w = new_date.WeekDay();

		if( w > weekday )
		{
			new_date.day -= (w - weekday);
		}
		else
		if( w < weekday )
		{
			new_date.day -= (w - weekday) + 7;
		}
	}

	return new_date;
}


TimeZone::Dst::Dst()
{
	Clear();
}


void TimeZone::Dst::Clear()
{
	has_dst = false;
	start.Clear();
	end.Clear();
	offset = 0;
}





bool TimeZone::Dst::IsDstUsed(const pt::Date & utc_date) const
{
	return has_dst && start.Compare(utc_date) <= 0 && end.Compare(utc_date) > 0;
}




TimeZone::TimeZone()
{
	Clear();
}




void TimeZone::Clear()
{
	name.clear();
	id         = 0;
	offset     = 0;
	dst_map.clear();
}



TimeZone::Dst * TimeZone::FindDst(int year)
{
	if( dst_map.empty() )
		return 0;

	DstMap::iterator i = dst_map.lower_bound(year);

	if( i == dst_map.begin() && i->first > year )
		return 0;

	if( i == dst_map.end() )
		return &(--i)->second;

	if( i != dst_map.begin() && i->first > year )
		return &(--i)->second;

return &i->second;
}



time_t TimeZone::CalcLocalOffset(const pt::Date & utc_date)
{
time_t dst_offset = 0;

	Dst * dst = FindDst(utc_date.year);

	if( dst && dst->IsDstUsed(utc_date) )
		dst_offset = dst->offset;

return offset + dst_offset;
}



time_t TimeZone::ToLocal(time_t utc_time)
{
	time_t offset = CalcLocalOffset(pt::Date(utc_time));

return utc_time + offset;
}


pt::Date TimeZone::ToLocal(const pt::Date & utc_date)
{
	pt::Date local(utc_date);
	local += CalcLocalOffset(utc_date);

return local;
}


void TimeZone::PrintOffsetPart(long val, pt::Stream & str)
{
	if( val < 10 )
	{
		str << '0';
	}

	str << val;
}


void TimeZone::PrintOffset(time_t offset, pt::Stream & str)
{
	bool has_sign = false;

	if( offset < 0 )
	{
		has_sign = true;
		offset = 0 - offset;
	}

	time_t days = offset / 60 / 60 / 24;

	if( days == 0 )
	{
		str << ((has_sign) ? '-' : '+');
		time_t diff = offset - days * 60 * 60 * 24;

		long hour = int(diff / 60 / 60);
		long min  = int((diff - hour * 60 * 60) / 60);

		PrintOffsetPart(hour, str);
		str << ':';
		PrintOffsetPart(min, str);
	}
}



time_t TimeZone::CalcUTCOffset(const pt::Date & local_date)
{
time_t dst_offset = 0;

	Dst * dst = FindDst(local_date.year);

	if( dst && dst->has_dst )
	{
		// dst date ranges we have in UTC
		pt::Date utc(local_date);
		utc -= (offset + dst->offset);

		if( dst->IsDstUsed(utc) )
			dst_offset = dst->offset;
	}

return offset + dst_offset;
}



time_t TimeZone::ToUTC(time_t local_time)
{
	time_t offset = CalcUTCOffset(pt::Date(local_time));

return local_time - offset;
}



pt::Date TimeZone::ToUTC(const pt::Date & local_date)
{
time_t offset;
pt::Date utc(local_date);

	offset = CalcUTCOffset(local_date);
	utc   -= offset;

return utc;
}



time_t TimeZone::ParseStrOffset(const wchar_t * str)
{
pt::Date date;
bool is_sign = false;
time_t offset = 0;

	str = SkipWhite(str);

	if( *str == '-' )
	{
		is_sign = true;
		str += 1;
	}
	else
	if( *str == '+' )
	{
		str += 1;
	}

	if( date.ParseTime(str) )
	{
		offset = date.hour * 60 * 60 + date.min * 60 + date.sec;

		if( is_sign )
			offset = -offset;
	}

return offset;
}


time_t TimeZone::GetOffset(pt::Space & space)
{
	std::wstring * offset_str = space.get_wstr(L"offset_str");

	if( offset_str )
		return ParseStrOffset(offset_str->c_str());

	return space.to_long(L"offset");
}


const wchar_t * TimeZone::SkipDstDateSeparator(const wchar_t * date_str)
{
	date_str = pt::skip_white(date_str, false, false);

	// the same separators as in the pikotools library
	if( *date_str == '-' || *date_str == '/' || *date_str == '.' )
	{
		++date_str;
	}

	return pt::skip_white(date_str, false, false);
}



int TimeZone::ParseDstDateWeekday(const wchar_t * date_str, const wchar_t ** after_date_str)
{
	date_str = SkipDstDateSeparator(date_str);
	int weekday_int = -1;

	struct WeekDay {
		const wchar_t * name;
		int weekday;
	};

	static const WeekDay week_days[] = {
		{L"sunday", 0},
		{L"monday", 1},
		{L"tuesday", 2},
		{L"wednesday", 3},
		{L"thursday", 4},
		{L"friday", 5},
		{L"saturday", 6},
	};

	for(const WeekDay & week_day : week_days)
	{
		if( pt::is_substr(week_day.name, date_str) )
		{
			date_str += wcslen(week_day.name);
			weekday_int = week_day.weekday;
			break;
		}
	}

	*after_date_str = date_str;
	return weekday_int;
}


bool TimeZone::ParseDstDate(int year, const wchar_t * date_str, DstDate & dst_date)
{
	bool was_overflow = false;
	bool is_ok = false;
	const wchar_t * after_date_str;

	dst_date.Clear();
	dst_date.date.year = year;

	date_str = pt::skip_white(date_str, false, false);
	dst_date.date.month = pt::to_i(date_str, 10, &after_date_str, &was_overflow, true);

	if( !was_overflow && after_date_str != date_str )
	{
		date_str = SkipDstDateSeparator(after_date_str);

		if( pt::is_substr(L"first", date_str) )
		{
			date_str += 5; // length of "first"
			dst_date.date_type = DstDate::first_weekday;
			dst_date.weekday = ParseDstDateWeekday(date_str, &date_str);
			dst_date.date.day = 1; // to return true from IsCorrectDate() at the end of this method, will not be used in the future
			is_ok = (dst_date.weekday >= 0);
		}
		else
		if( pt::is_substr(L"last", date_str) )
		{
			date_str += 4; // length of "last"
			dst_date.date_type = DstDate::last_weekday;
			dst_date.weekday = ParseDstDateWeekday(date_str, &date_str);
			dst_date.date.day = 1;
			is_ok = (dst_date.weekday >= 0);
		}
		else
		{
			dst_date.date_type = DstDate::ordinary_date;
			dst_date.date.day = pt::to_i(date_str, 10, &after_date_str, &was_overflow, true);
			is_ok = !was_overflow && after_date_str != date_str;
			date_str = after_date_str;
		}
	}

	return is_ok && dst_date.date.ParseTime(date_str) && dst_date.date.IsCorrectDate();
}


bool TimeZone::SetTzDst(pt::Space & year)
{
	time_t h24 = pt::Date::ONE_DAY;
	bool result = true;
	Dst dst;

	int year_int = 0;
	std::wstring * year_name = year.get_wstr(L"year");

	if( year_name )
		year_int = Toi(*year_name);

	if( year_int < 1970 || year_int > 10000 )
		return false;

	bool has_dst = year.to_bool(L"has_dst", false);
	std::wstring * dst_start = year.get_wstr(L"start");
	std::wstring * dst_end = year.get_wstr(L"end");

	if( has_dst && dst_start && dst_end )
	{
		dst.has_dst = true;
		result = result && ParseDstDate(year_int, dst_start->c_str(), dst.start);
		result = result && ParseDstDate(year_int, dst_end->c_str(), dst.end);
		dst.offset = GetOffset(year);

		if( dst.offset < -h24 || dst.offset > h24 )
			result = false;
	}

	if( result )
		dst_map[year_int] = dst;

	return result;
}


bool TimeZone::SetTz(pt::Space & space)
{
	bool result = true;
	name.clear();

	std::wstring * space_name = space.get_wstr(L"name");

	if( space_name )
		name = *space_name;

	id      = space.to_int(L"id", -1);
	offset  = GetOffset(space);
	time_t h24 = pt::Date::ONE_DAY;

	if( offset < -h24 || offset > h24 )
		result = false;

	pt::Space::TableType * dst = space.get_table(L"dst");

	if( dst )
	{
		for(pt::Space * dst_space : *dst)
		{
			if( !SetTzDst(*dst_space) )
			{
				result = false;
				break;
			}
		}
	}

	return result;
}



} // namespace Winix