/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file date.cpp Handling of dates in our native format and transforming them to something human readable. */

#include "stdafx.h"
#include "network/network.h"
#include "network/network_func.h"
#include "currency.h"
#include "window_func.h"
#include "settings_type.h"
#include "date_func.h"
#include "vehicle_base.h"
#include "rail_gui.h"
#include "linkgraph/linkgraph.h"
#include "saveload/saveload.h"

#include "safeguards.h"

Year      _cur_year;   ///< Current year, starting at 0
Month     _cur_month;  ///< Current month (0..11)
Date      _date;       ///< Current date in days (day counter)
DateFract _date_fract; ///< Fractional part of the day.
uint16 _tick_counter;  ///< Ever incrementing (and sometimes wrapping) tick counter for setting off various events

/**
 * Set the date.
 * @param date  New date
 * @param fract The number of ticks that have passed on this date.
 */
void SetDate(Date date, DateFract fract)
{
	assert(fract < DAY_TICKS);

	YearMonthDay ymd;

	_date = date;
	_date_fract = fract;
	ConvertDateToYMD(date, &ymd);
	_cur_year = ymd.year;
	_cur_month = ymd.month;
}

#define M(a, b) ((a << 5) | b)
static const uint16 _month_date_from_year_day[] = {
	M( 0, 1), M( 0, 2), M( 0, 3), M( 0, 4), M( 0, 5), M( 0, 6), M( 0, 7), M( 0, 8), M( 0, 9), M( 0, 10), M( 0, 11), M( 0, 12), M( 0, 13), M( 0, 14), M( 0, 15), M( 0, 16), M( 0, 17), M( 0, 18), M( 0, 19), M( 0, 20), M( 0, 21), M( 0, 22), M( 0, 23), M( 0, 24), M( 0, 25), M( 0, 26), M( 0, 27), M( 0, 28), M( 0, 29), M( 0, 30), M( 0, 31),
	M( 1, 1), M( 1, 2), M( 1, 3), M( 1, 4), M( 1, 5), M( 1, 6), M( 1, 7), M( 1, 8), M( 1, 9), M( 1, 10), M( 1, 11), M( 1, 12), M( 1, 13), M( 1, 14), M( 1, 15), M( 1, 16), M( 1, 17), M( 1, 18), M( 1, 19), M( 1, 20), M( 1, 21), M( 1, 22), M( 1, 23), M( 1, 24), M( 1, 25), M( 1, 26), M( 1, 27), M( 1, 28), M( 1, 29),
	M( 2, 1), M( 2, 2), M( 2, 3), M( 2, 4), M( 2, 5), M( 2, 6), M( 2, 7), M( 2, 8), M( 2, 9), M( 2, 10), M( 2, 11), M( 2, 12), M( 2, 13), M( 2, 14), M( 2, 15), M( 2, 16), M( 2, 17), M( 2, 18), M( 2, 19), M( 2, 20), M( 2, 21), M( 2, 22), M( 2, 23), M( 2, 24), M( 2, 25), M( 2, 26), M( 2, 27), M( 2, 28), M( 2, 29), M( 2, 30), M( 2, 31),
	M( 3, 1), M( 3, 2), M( 3, 3), M( 3, 4), M( 3, 5), M( 3, 6), M( 3, 7), M( 3, 8), M( 3, 9), M( 3, 10), M( 3, 11), M( 3, 12), M( 3, 13), M( 3, 14), M( 3, 15), M( 3, 16), M( 3, 17), M( 3, 18), M( 3, 19), M( 3, 20), M( 3, 21), M( 3, 22), M( 3, 23), M( 3, 24), M( 3, 25), M( 3, 26), M( 3, 27), M( 3, 28), M( 3, 29), M( 3, 30),
	M( 4, 1), M( 4, 2), M( 4, 3), M( 4, 4), M( 4, 5), M( 4, 6), M( 4, 7), M( 4, 8), M( 4, 9), M( 4, 10), M( 4, 11), M( 4, 12), M( 4, 13), M( 4, 14), M( 4, 15), M( 4, 16), M( 4, 17), M( 4, 18), M( 4, 19), M( 4, 20), M( 4, 21), M( 4, 22), M( 4, 23), M( 4, 24), M( 4, 25), M( 4, 26), M( 4, 27), M( 4, 28), M( 4, 29), M( 4, 30), M( 4, 31),
	M( 5, 1), M( 5, 2), M( 5, 3), M( 5, 4), M( 5, 5), M( 5, 6), M( 5, 7), M( 5, 8), M( 5, 9), M( 5, 10), M( 5, 11), M( 5, 12), M( 5, 13), M( 5, 14), M( 5, 15), M( 5, 16), M( 5, 17), M( 5, 18), M( 5, 19), M( 5, 20), M( 5, 21), M( 5, 22), M( 5, 23), M( 5, 24), M( 5, 25), M( 5, 26), M( 5, 27), M( 5, 28), M( 5, 29), M( 5, 30),
	M( 6, 1), M( 6, 2), M( 6, 3), M( 6, 4), M( 6, 5), M( 6, 6), M( 6, 7), M( 6, 8), M( 6, 9), M( 6, 10), M( 6, 11), M( 6, 12), M( 6, 13), M( 6, 14), M( 6, 15), M( 6, 16), M( 6, 17), M( 6, 18), M( 6, 19), M( 6, 20), M( 6, 21), M( 6, 22), M( 6, 23), M( 6, 24), M( 6, 25), M( 6, 26), M( 6, 27), M( 6, 28), M( 6, 29), M( 6, 30), M( 6, 31),
	M( 7, 1), M( 7, 2), M( 7, 3), M( 7, 4), M( 7, 5), M( 7, 6), M( 7, 7), M( 7, 8), M( 7, 9), M( 7, 10), M( 7, 11), M( 7, 12), M( 7, 13), M( 7, 14), M( 7, 15), M( 7, 16), M( 7, 17), M( 7, 18), M( 7, 19), M( 7, 20), M( 7, 21), M( 7, 22), M( 7, 23), M( 7, 24), M( 7, 25), M( 7, 26), M( 7, 27), M( 7, 28), M( 7, 29), M( 7, 30), M( 7, 31),
	M( 8, 1), M( 8, 2), M( 8, 3), M( 8, 4), M( 8, 5), M( 8, 6), M( 8, 7), M( 8, 8), M( 8, 9), M( 8, 10), M( 8, 11), M( 8, 12), M( 8, 13), M( 8, 14), M( 8, 15), M( 8, 16), M( 8, 17), M( 8, 18), M( 8, 19), M( 8, 20), M( 8, 21), M( 8, 22), M( 8, 23), M( 8, 24), M( 8, 25), M( 8, 26), M( 8, 27), M( 8, 28), M( 8, 29), M( 8, 30),
	M( 9, 1), M( 9, 2), M( 9, 3), M( 9, 4), M( 9, 5), M( 9, 6), M( 9, 7), M( 9, 8), M( 9, 9), M( 9, 10), M( 9, 11), M( 9, 12), M( 9, 13), M( 9, 14), M( 9, 15), M( 9, 16), M( 9, 17), M( 9, 18), M( 9, 19), M( 9, 20), M( 9, 21), M( 9, 22), M( 9, 23), M( 9, 24), M( 9, 25), M( 9, 26), M( 9, 27), M( 9, 28), M( 9, 29), M( 9, 30), M( 9, 31),
	M(10, 1), M(10, 2), M(10, 3), M(10, 4), M(10, 5), M(10, 6), M(10, 7), M(10, 8), M(10, 9), M(10, 10), M(10, 11), M(10, 12), M(10, 13), M(10, 14), M(10, 15), M(10, 16), M(10, 17), M(10, 18), M(10, 19), M(10, 20), M(10, 21), M(10, 22), M(10, 23), M(10, 24), M(10, 25), M(10, 26), M(10, 27), M(10, 28), M(10, 29), M(10, 30),
	M(11, 1), M(11, 2), M(11, 3), M(11, 4), M(11, 5), M(11, 6), M(11, 7), M(11, 8), M(11, 9), M(11, 10), M(11, 11), M(11, 12), M(11, 13), M(11, 14), M(11, 15), M(11, 16), M(11, 17), M(11, 18), M(11, 19), M(11, 20), M(11, 21), M(11, 22), M(11, 23), M(11, 24), M(11, 25), M(11, 26), M(11, 27), M(11, 28), M(11, 29), M(11, 30), M(11, 31),
};
#undef M

enum DaysTillMonth {
	ACCUM_JAN = 0,
	ACCUM_FEB = ACCUM_JAN + 31,
	ACCUM_MAR = ACCUM_FEB + 29,
	ACCUM_APR = ACCUM_MAR + 31,
	ACCUM_MAY = ACCUM_APR + 30,
	ACCUM_JUN = ACCUM_MAY + 31,
	ACCUM_JUL = ACCUM_JUN + 30,
	ACCUM_AUG = ACCUM_JUL + 31,
	ACCUM_SEP = ACCUM_AUG + 31,
	ACCUM_OCT = ACCUM_SEP + 30,
	ACCUM_NOV = ACCUM_OCT + 31,
	ACCUM_DEC = ACCUM_NOV + 30,
};

/** Number of days to pass from the first day in the year before reaching the first of a month. */
static const uint16 _accum_days_for_month[] = {
	ACCUM_JAN, ACCUM_FEB, ACCUM_MAR, ACCUM_APR,
	ACCUM_MAY, ACCUM_JUN, ACCUM_JUL, ACCUM_AUG,
	ACCUM_SEP, ACCUM_OCT, ACCUM_NOV, ACCUM_DEC,
};

/**
 * Converts a Date to a Year, Month & Day.
 * @param date the date to convert from
 * @param ymd  the year, month and day to write to
 */
void ConvertDateToYMD(Date date, YearMonthDay *ymd)
{
	/* Year determination in multiple steps to account for leap
	 * years. First do the large steps, then the smaller ones.
	 */

	/* There are 97 leap years in 400 years */
	Year yr = 400 * (date / (DAYS_IN_YEAR * 400 + 97));
	int rem = date % (DAYS_IN_YEAR * 400 + 97);
	uint16 x;

	if (rem >= DAYS_IN_YEAR * 100 + 25) {
		/* There are 25 leap years in the first 100 years after
		 * every 400th year, as every 400th year is a leap year */
		yr  += 100;
		rem -= DAYS_IN_YEAR * 100 + 25;

		/* There are 24 leap years in the next couple of 100 years */
		yr += 100 * (rem / (DAYS_IN_YEAR * 100 + 24));
		rem = (rem % (DAYS_IN_YEAR * 100 + 24));
	}

	if (!IsLeapYear(yr) && rem >= DAYS_IN_YEAR * 4) {
		/* The first 4 year of the century are not always a leap year */
		yr  += 4;
		rem -= DAYS_IN_YEAR * 4;
	}

	/* There is 1 leap year every 4 years */
	yr += 4 * (rem / (DAYS_IN_YEAR * 4 + 1));
	rem = rem % (DAYS_IN_YEAR * 4 + 1);

	/* The last (max 3) years to account for; the first one
	 * can be, but is not necessarily a leap year */
	while (rem >= (IsLeapYear(yr) ? DAYS_IN_LEAP_YEAR : DAYS_IN_YEAR)) {
		rem -= IsLeapYear(yr) ? DAYS_IN_LEAP_YEAR : DAYS_IN_YEAR;
		yr++;
	}

	/* Skip the 29th of February in non-leap years */
	if (!IsLeapYear(yr) && rem >= ACCUM_MAR - 1) rem++;

	ymd->year = yr;

	x = _month_date_from_year_day[rem];
	ymd->month = x >> 5;
	ymd->day = x & 0x1F;
}

/**
 * Converts a tuple of Year, Month and Day to a Date.
 * @param year  is a number between 0..MAX_YEAR
 * @param month is a number between 0..11
 * @param day   is a number between 1..31
 */
Date ConvertYMDToDate(Year year, Month month, Day day)
{
	/* Day-offset in a leap year */
	int days = _accum_days_for_month[month] + day - 1;

	/* Account for the missing of the 29th of February in non-leap years */
	if (!IsLeapYear(year) && days >= ACCUM_MAR) days--;

	return DAYS_TILL(year) + days;
}

/** Functions used by the IncreaseDate function */

extern void EnginesDailyLoop();
extern void DisasterDailyLoop();
extern void IndustryDailyLoop();

extern void CompaniesMonthlyLoop();
extern void EnginesMonthlyLoop();
extern void TownsMonthlyLoop();
extern void IndustryMonthlyLoop();
extern void StationMonthlyLoop();
extern void SubsidyMonthlyLoop();

extern void CompaniesYearlyLoop();
extern void VehiclesYearlyLoop();
extern void TownsYearlyLoop();

extern void ShowEndGameChart();


/** Available settings for autosave intervals. */
static const Month _autosave_months[] = {
	 0, ///< never
	 1, ///< every month
	 3, ///< every 3 months
	 6, ///< every 6 months
	12, ///< every 12 months
};

/**
 * Runs various procedures that have to be done yearly
 */
static void OnNewYear()
{
	CompaniesYearlyLoop();
	VehiclesYearlyLoop();
	TownsYearlyLoop();
	InvalidateWindowClassesData(WC_BUILD_STATION);
	if (_network_server) NetworkServerYearlyLoop();

	if (_cur_year == _settings_client.gui.semaphore_build_before) ResetSignalVariant();

	/* check if we reached end of the game */
	if (_cur_year == ORIGINAL_END_YEAR) {
		ShowEndGameChart();
	/* check if we reached the maximum year, decrement dates by a year */
	} else if (_cur_year == MAX_YEAR + 1) {
		Vehicle *v;
		int days_this_year;

		_cur_year--;
		days_this_year = IsLeapYear(_cur_year) ? DAYS_IN_LEAP_YEAR : DAYS_IN_YEAR;
		_date -= days_this_year;
		FOR_ALL_VEHICLES(v) v->date_of_last_service -= days_this_year;

		LinkGraph *lg;
		FOR_ALL_LINK_GRAPHS(lg) lg->ShiftDates(-days_this_year);

		/* Because the _date wraps here, and text-messages expire by game-days, we have to clean out
		 *  all of them if the date is set back, else those messages will hang for ever */
		NetworkInitChatMessage();
	}

	if (_settings_client.gui.auto_euro) CheckSwitchToEuro();
}

/**
 * Runs various procedures that have to be done monthly
 */
static void OnNewMonth()
{
	if (_settings_client.gui.autosave != 0 && (_cur_month % _autosave_months[_settings_client.gui.autosave]) == 0) {
		_do_autosave = true;
		SetWindowDirty(WC_STATUS_BAR, 0);
	}

	SetWindowClassesDirty(WC_CHEATS);
	CompaniesMonthlyLoop();
	EnginesMonthlyLoop();
	TownsMonthlyLoop();
	IndustryMonthlyLoop();
	SubsidyMonthlyLoop();
	StationMonthlyLoop();
	if (_network_server) NetworkServerMonthlyLoop();
}

/**
 * Runs various procedures that have to be done daily
 */
static void OnNewDay()
{
	if (_network_server) NetworkServerDailyLoop();

	DisasterDailyLoop();
	IndustryDailyLoop();

	SetWindowWidgetDirty(WC_STATUS_BAR, 0, 0);
	EnginesDailyLoop();

	/* Refresh after possible snowline change */
	SetWindowClassesDirty(WC_TOWN_VIEW);
}

/**
 * Increases the tick counter, increases date  and possibly calls
 * procedures that have to be called daily, monthly or yearly.
 */
void IncreaseDate()
{
	/* increase day, and check if a new day is there? */
	_tick_counter++;

	if (_game_mode == GM_MENU) return;

	_date_fract++;
	if (_date_fract < DAY_TICKS) return;
	_date_fract = 0;

	/* increase day counter */
	_date++;

	YearMonthDay ymd;
	ConvertDateToYMD(_date, &ymd);

	/* check if we entered a new month? */
	bool new_month = ymd.month != _cur_month;

	/* check if we entered a new year? */
	bool new_year = ymd.year != _cur_year;

	/* update internal variables before calling the daily/monthly/yearly loops */
	_cur_month = ymd.month;
	_cur_year  = ymd.year;

	/* yes, call various daily loops */
	OnNewDay();

	/* yes, call various monthly loops */
	if (new_month) OnNewMonth();

	/* yes, call various yearly loops */
	if (new_year) OnNewYear();
}