/*
  DateTime.cpp - Arduino Date and Time library
  Copyright (c) Michael Margolis.  All right reserved.

  This library 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.
*/

#include "DateTime.h"
#include "Data/CStringArray.h"
#include <stringconversion.h>

#define LEAP_YEAR(year) ((year % 4) == 0)

DEFINE_FSTR_LOCAL(flashMonthNames, LOCALE_MONTH_NAMES);
DEFINE_FSTR_LOCAL(flashDayNames, LOCALE_DAY_NAMES);

/* We can more efficiently compare text of 4 character length by comparing as words */
union FourDigitName {
	char c[4];
	uint32_t value;

	bool operator==(const FourDigitName& name) const
	{
		return value == name.value;
	}
};

static const FourDigitName isoDayNames[7] PROGMEM = {
	{'S', 'u', 'n', '\0'}, {'M', 'o', 'n', '\0'}, {'T', 'u', 'e', '\0'}, {'W', 'e', 'd', '\0'},
	{'T', 'h', 'u', '\0'}, {'F', 'r', 'i', '\0'}, {'S', 'a', 't', '\0'},
};

static const FourDigitName isoMonthNames[12] PROGMEM = {
	{'J', 'a', 'n', '\0'}, {'F', 'e', 'b', '\0'}, {'M', 'a', 'r', '\0'}, {'A', 'p', 'r', '\0'},
	{'M', 'a', 'y', '\0'}, {'J', 'u', 'n', '\0'}, {'J', 'u', 'l', '\0'}, {'A', 'u', 'g', '\0'},
	{'S', 'e', 'p', '\0'}, {'O', 'c', 't', '\0'}, {'N', 'o', 'v', '\0'}, {'D', 'e', 'c', '\0'},
};

/** @brief Get the number of days in a month, taking leap years into account
 *  @param month 0=jan
 *  @param year
 *  @retval uint8_t number of days in the month
 */
static uint8_t getMonthDays(uint8_t month, uint8_t year)
{
	static const uint8_t monthDays[] PROGMEM = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
	return (month == 1 && LEAP_YEAR(year)) ? 29 : pgm_read_byte(&monthDays[month]);
}

//******************************************************************************
//* DateTime Public Methods
//******************************************************************************

void DateTime::setTime(time_t time)
{
	fromUnixTime(time, &Second, &Minute, &Hour, &Day, &DayofWeek, &Month, &Year);
	Milliseconds = 0;
	calcDayOfYear();
}

bool DateTime::isNull()
{
	return Second == 0 && Minute == 0 && Hour == 0 && Day == 0 && Month == 0 && Year == 0 && DayofWeek == 0 &&
		   Milliseconds == 0;
}

bool DateTime::fromHttpDate(const String& httpDate)
{
	int first = httpDate.indexOf(',');
	if(first < 0 || httpDate.length() - first < 20) {
		return false;
	}
	first += 2; // Skip ", "
	auto ptr = httpDate.c_str();

	// Parse and return a decimal number and update ptr to the first non-numeric character after it
	auto parseNumber = [&ptr]() { return strtol(ptr, const_cast<char**>(&ptr), 10); };

	// Match a day or month name against a list of values and set the required value; return false on failure
	auto matchName = [&ptr](uint8_t& value, const FourDigitName isoNames[], unsigned nameCount) {
		FourDigitName name = {ptr[0], ptr[1], ptr[2], '\0'};
		for(unsigned i = 0; i < nameCount; ++i) {
			if(isoNames[i] == name) {
				value = i;
				return true;
			}
		}
		return false;
	};

	if(!matchName(DayofWeek, isoDayNames, 7)) {
		return false; // Invalid day of week
	}

	ptr += first;

	Day = parseNumber();
	if(*ptr == '\0') {
		return false;
	}
	ptr++;

	// Decode the month name
	if(!matchName(Month, isoMonthNames, 12)) {
		return false; // Invalid month
	}
	ptr += 4; // Skip space as well as month

	Year = parseNumber();
	if(*ptr == '\0') {
		return false;
	}

	if(Year < 70) {
		Year += 2000;
	} else if(Year < 100) {
		Year += 1900;
	}

	Hour = parseNumber();
	if(*ptr != ':') {
		return false;
	}

	ptr++;
	Minute = parseNumber();
	if(*ptr != ':') {
		return false;
	}

	ptr++;
	Second = parseNumber();
	Milliseconds = 0;
	calcDayOfYear();

	return true;
}

time_t DateTime::toUnixTime()
{
	return toUnixTime(Second + (Milliseconds / 1000), Minute, Hour, Day, Month, Year);
}

String DateTime::toShortDateString()
{
	return format(_F("%d.%m.%Y"));
}

String DateTime::toShortTimeString(bool includeSeconds)
{
	return format(includeSeconds ? _F("%T") : _F("%r"));
}

String DateTime::toFullDateTimeString()
{
	return format(_F("%x %T"));
}

String DateTime::toISO8601()
{
	return format(_F("%FT%TZ"));
}

String DateTime::toHTTPDate()
{
	return format(_F("%a, %d %b %Y %T GMT"));
}

void DateTime::addMilliseconds(long add)
{
	int ms = Milliseconds;
	ms += add;
	time_t cur = toUnixTime();
	cur += (ms / 1000);
	ms = ms % 1000;
	setTime(cur);
	Milliseconds = ms;
}

void DateTime::fromUnixTime(time_t timep, uint8_t* psec, uint8_t* pmin, uint8_t* phour, uint8_t* pday, uint8_t* pwday,
							uint8_t* pmonth, uint16_t* pyear)
{
	// convert the given time_t to time components
	// this is a more compact version of the C library localtime function

	unsigned long epoch = timep;
	if(psec != nullptr) {
		*psec = epoch % 60;
	}
	epoch /= 60; // now it is minutes
	if(pmin != nullptr) {
		*pmin = epoch % 60;
	}
	epoch /= 60; // now it is hours
	if(phour != nullptr) {
		*phour = epoch % 24;
	}
	epoch /= 24; // now it is days
	if(pwday != nullptr) {
		*pwday = (epoch + 4) % 7;
	}

	unsigned year = 70;
	unsigned long days = 0;
	while((days += (LEAP_YEAR(year) ? 366 : 365)) <= epoch) {
		year++;
	}
	if(pyear != nullptr) {
		*pyear = year + 1900; // *pyear is returned as years from 1900
	}

	days -= LEAP_YEAR(year) ? 366 : 365;
	epoch -= days; // now it is days in this year, starting at 0
	// *pdayofyear=epoch;  // days since jan 1 this year

	uint8_t month;
	for(month = 0; month < 12; month++) {
		uint8_t monthDays = getMonthDays(month, year);
		if(epoch >= monthDays) {
			epoch -= monthDays;
		} else {
			break;
		}
	}

	if(pmonth != nullptr) {
		*pmonth = month; // jan is month 0
	}
	if(pday != nullptr) {
		*pday = epoch + 1; // day of month
	}
}

time_t DateTime::toUnixTime(uint8_t sec, uint8_t min, uint8_t hour, uint8_t day, uint8_t month, uint16_t year)
{
	// converts time components to time_t
	// note year argument is full four digit year (or digits since 2000), i.e.1975, (year 8 is 2008)

	if(year < 69) {
		year += 2000;
	}
	// seconds from 1970 till 1 jan 00:00:00 this year
	time_t seconds = (year - 1970) * (SECS_PER_DAY * 365);

	// add extra days for leap years
	for(unsigned i = 1970; i < year; i++) {
		if(LEAP_YEAR(i)) {
			seconds += SECS_PER_DAY;
		}
	}
	// add days for this year
	for(unsigned i = 0; i < month; i++) {
		seconds += SECS_PER_DAY * getMonthDays(i, year);
	}

	seconds += (day - 1) * SECS_PER_DAY;
	seconds += hour * SECS_PER_HOUR;
	seconds += min * SECS_PER_MIN;
	seconds += sec;

	return seconds;
}

String DateTime::format(const char* sFormat)
{
	if(sFormat == nullptr) {
		return nullptr;
	}

	String sReturn;

	char c;
	while((c = *sFormat++) != '\0') {
		if(c != '%') {
			// Normal character
			sReturn += c;
			continue;
		}

		if(*sFormat == '\0') {
			// Ignore % as last character
			break;
		}

		c = *sFormat++;
		switch(c) {
		// Year (not implemented: EY, Oy, Ey, EC, G, g)
		case 'Y': // Full year as a decimal number, e.g. 2018
			sReturn += Year;
			break;
		case 'y': // Year, last 2 digits as a decimal number [00..99]
			sReturn.concat(Year % 100, DEC, 2);
			break;
		case 'C': // Year, first 2 digits as a decimal number [00..99]
			sReturn.concat(Year / 100, DEC, 2);
			break;
		// Month (not implemented: Om)
		case 'b': // Abbreviated month name, e.g. Oct (always English)
		case 'h': // Synonym of b
			sReturn.concat(CStringArray(flashMonthNames)[Month], 3);
			break;
		case 'B': // Full month name, e.g. October (always English)
			sReturn += CStringArray(flashMonthNames)[Month];
			break;
		case 'm': // Month as a decimal number [01..12]
			sReturn.concat(Month + 1, DEC, 2);
			break;
		// Week (not implemented: OU, OW, OV)
		case 'U': // Week of the year as a decimal number (Sunday is the first day of the week) [00..53]
			sReturn.concat(calcWeek(0), DEC, 2);
			break;
		case 'V': // ISO 8601 week number (01-53)
			// !@todo Calculation of ISO 8601 week number is crude and frankly wrong but does anyone care?
			sReturn.concat(calcWeek(1) + 1, DEC, 2);
			break;
		case 'W': // Week of the year as a decimal number (Monday is the first day of the week) [00..53]
			sReturn.concat(calcWeek(1), DEC, 2);
			break;
		case 'x': // Locale preferred date format
			sReturn += format(_F(LOCALE_DATE));
			break;
		case 'X': // Locale preferred time format
			sReturn += format(_F(LOCALE_TIME));
			break;
		// Day of year/month (Not implemented: Od, Oe)
		case 'j': // Day of the year as a decimal number [001..366]
			sReturn.concat(DayofYear, DEC, 3);
			break;
		case 'd': // Day of the month as a decimal number [01..31]
			sReturn.concat(Day, DEC, 2);
			break;
		case 'e': // Day of the month as a decimal number [ 1,31]
			sReturn.concat(Day, DEC, 2, ' ');
			break;
		// Day of week (Not implemented: Ow, Ou)
		case 'w': // Weekday as a decimal number with Sunday as 0 [0..6]
			sReturn += char('0' + DayofWeek);
			break;
		case 'a': // Abbreviated weekday name, e.g. Fri
			sReturn.concat(CStringArray(flashDayNames)[DayofWeek], 3);
			break;
		case 'A': // Full weekday name, e.g. Friday
			sReturn += CStringArray(flashDayNames)[DayofWeek];
			break;
		case 'u': // Weekday as a decimal number, where Monday is 1 (ISO 8601 format) [1..7]
			sReturn += (DayofWeek == 0) ? '7' : char('0' + DayofWeek);
			break;
		// Time (not implemented: OH, OI, OM, OS)
		case 'H': // Hour as a decimal number, 24 hour clock [00..23]
			sReturn.concat(Hour, DEC, 2);
			break;
		case 'I': // Hour as a decimal number, 12 hour clock [0..12]
			sReturn.concat(Hour ? ((Hour > 12) ? Hour - 12 : Hour) : 12, DEC, 2);
			break;
		case 'M': // Minute as a decimal number [00..59]
			sReturn.concat(Minute, DEC, 2);
			break;
		case 'S': // Second as a decimal number [00..61]
			sReturn.concat(Second, DEC, 2);
			break;
		// Other (not implemented: Ec, Ex, EX, z, Z)
		case 'c': // Locale preferred date and time format, e.g. Tue Dec 11 08:48:32 2018
			sReturn += format(_F(LOCALE_DATE_TIME));
			break;
		case 'D': // US date (MM/DD/YY)
			sReturn += format(_F("%m/%d/%y"));
			break;
		case 'F': // ISO 8601 date format (YYYY-mm-dd)
			sReturn += format(_F("%Y-%m-%d"));
			break;
		case 'r': // 12-hour clock time (hh:MM:SS AM)
			sReturn += format(_F("%I:%M:%S %p"));
			break;
		case 'R': // Short time (HH:MM)
			sReturn += format(_F("%H:%M"));
			break;
		case 'T': // ISO 8601 time format (HH:MM:SS)
			sReturn += format(_F("%H:%M:%S"));
			break;
		case 'p': // Meridiem [AM,PM]
			sReturn += (Hour < 12) ? "AM" : "PM";
			break;
		case '%': // Literal percent (%). The full conversion specification must be %%
			sReturn += '%';
			break;
		case 'n': // Newline character (\n)
			sReturn += '\n';
			break;
		case 't': // Horizontal tab (\t)
			sReturn += '\t';
			break;
		default: // Silently ignore % and process next character
			--sFormat;
		}
	}
	return sReturn;
}

void DateTime::calcDayOfYear()
{
	DayofYear = 0;
	for(auto i = 0; i < Month; ++i) {
		switch(i) {
		case 8:  // Sep
		case 3:  // Apr
		case 5:  // Jun
		case 10: // Nov
			DayofYear += 30;
			break;
		case 1: // Feb
			DayofYear += LEAP_YEAR(Year) ? 29 : 28;
			break;
		default:
			DayofYear += 31;
		}
	}
	DayofYear += Day;
}

uint8_t DateTime::calcWeek(uint8_t firstDay)
{
	int16_t startOfWeek = DayofYear - DayofWeek + firstDay;
	int8_t firstDayofWeek = startOfWeek % 7;
	if(firstDayofWeek < 0) {
		firstDayofWeek += 7;
	}
	return (startOfWeek + 7 - firstDayofWeek) / 7;
}