/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2013, 2014 Damien P. George
 * Copyright (c) 2015 Daniel Campora
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "py/obj.h"

#include "lib/timeutils/timeutils.h"

// LEAPOCH corresponds to 2000年03月01日, which is a mod-400 year, immediately
// after Feb 29. We calculate seconds as a signed integer relative to that.
//
// Our timebase is relative to 2000年01月01日.

#define LEAPOCH ((31 + 29) * 86400)

#define DAYS_PER_400Y (365*400 + 97)
#define DAYS_PER_100Y (365*100 + 24)
#define DAYS_PER_4Y (365*4 + 1)

STATIC const uint16_t days_since_jan1[]= { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };

bool timeutils_is_leap_year(mp_uint_t year) {
 return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
}

// month is one based
mp_uint_t timeutils_days_in_month(mp_uint_t year, mp_uint_t month) {
 mp_uint_t mdays = days_since_jan1[month] - days_since_jan1[month - 1];
 if (month == 2 && timeutils_is_leap_year(year)) {
 mdays++;
 }
 return mdays;
}

// compute the day of the year, between 1 and 366
// month should be between 1 and 12, date should start at 1
mp_uint_t timeutils_year_day(mp_uint_t year, mp_uint_t month, mp_uint_t date) {
 mp_uint_t yday = days_since_jan1[month - 1] + date;
 if (month >= 3 && timeutils_is_leap_year(year)) {
 yday += 1;
 }
 return yday;
}

void timeutils_seconds_since_2000_to_struct_time(mp_uint_t t, timeutils_struct_time_t *tm) {
 // The following algorithm was adapted from musl's __secs_to_tm and adapted
 // for differences in MicroPython's timebase.

 mp_int_t seconds = t - LEAPOCH;

 mp_int_t days = seconds / 86400;
 seconds %= 86400;
 if (seconds < 0) {
 seconds += 86400;
 days -= 1;
 }
 tm->tm_hour = seconds / 3600;
 tm->tm_min = seconds / 60 % 60;
 tm->tm_sec = seconds % 60;

 mp_int_t wday = (days + 2) % 7; // Mar 1, 2000 was a Wednesday (2)
 if (wday < 0) {
 wday += 7;
 }
 tm->tm_wday = wday;

 mp_int_t qc_cycles = days / DAYS_PER_400Y;
 days %= DAYS_PER_400Y;
 if (days < 0) {
 days += DAYS_PER_400Y;
 qc_cycles--;
 }
 mp_int_t c_cycles = days / DAYS_PER_100Y;
 if (c_cycles == 4) {
 c_cycles--;
 }
 days -= (c_cycles * DAYS_PER_100Y);

 mp_int_t q_cycles = days / DAYS_PER_4Y;
 if (q_cycles == 25) {
 q_cycles--;
 }
 days -= q_cycles * DAYS_PER_4Y;

 mp_int_t years = days / 365;
 if (years == 4) {
 years--;
 }
 days -= (years * 365);

 /* We will compute tm_yday at the very end
 mp_int_t leap = !years && (q_cycles || !c_cycles);

 tm->tm_yday = days + 31 + 28 + leap;
 if (tm->tm_yday >= 365 + leap) {
 tm->tm_yday -= 365 + leap;
 }

 tm->tm_yday++; // Make one based
 */

 tm->tm_year = 2000 + years + 4 * q_cycles + 100 * c_cycles + 400 * qc_cycles;

 // Note: days_in_month[0] corresponds to March
 STATIC const int8_t days_in_month[] = {31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 29};

 mp_int_t month;
 for (month = 0; days_in_month[month] <= days; month++) {
 days -= days_in_month[month];
 }

 tm->tm_mon = month + 2;
 if (tm->tm_mon >= 12) {
 tm->tm_mon -= 12;
 tm->tm_year++;
 }
 tm->tm_mday = days + 1; // Make one based
 tm->tm_mon++; // Make one based

 tm->tm_yday = timeutils_year_day(tm->tm_year, tm->tm_mon, tm->tm_mday);
}

// returns the number of seconds, as an integer, since 2000年01月01日
mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
 mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
 return
 second
 + minute * 60
 + hour * 3600
 + (timeutils_year_day(year, month, date) - 1
 + ((year - 2000 + 3) / 4) // add a day each 4 years starting with 2001
 - ((year - 2000 + 99) / 100) // subtract a day each 100 years starting with 2001
 + ((year - 2000 + 399) / 400) // add a day each 400 years starting with 2001
 ) * 86400
 + (year - 2000) * 31536000;
}

void timeutils_seconds_since_epoch_to_struct_time(mp_uint_t t, timeutils_struct_time_t *tm) {
 t -= EPOCH1970_EPOCH2000_DIFF_SECS;
 timeutils_seconds_since_2000_to_struct_time(t, tm);
}

mp_uint_t timeutils_seconds_since_epoch(mp_uint_t year, mp_uint_t month, mp_uint_t date,
 mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
 mp_uint_t t = timeutils_seconds_since_2000(year, month, date, hour, minute, second);
 return t + EPOCH1970_EPOCH2000_DIFF_SECS;
}

mp_uint_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday,
 mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {

 // Normalize the tuple. This allows things like:
 //
 // tm_tomorrow = list(time.localtime())
 // tm_tomorrow[2] += 1 # Adds 1 to mday
 // tomorrow = time.mktime(tm_tomorrow)
 //
 // And not have to worry about all the weird overflows.
 //
 // You can subtract dates/times this way as well.

 minutes += seconds / 60;
 if ((seconds = seconds % 60) < 0) {
 seconds += 60;
 minutes--;
 }

 hours += minutes / 60;
 if ((minutes = minutes % 60) < 0) {
 minutes += 60;
 hours--;
 }

 mday += hours / 24;
 if ((hours = hours % 24) < 0) {
 hours += 24;
 mday--;
 }

 month--; // make month zero based
 year += month / 12;
 if ((month = month % 12) < 0) {
 month += 12;
 year--;
 }
 month++; // back to one based

 while (mday < 1) {
 if (--month == 0) {
 month = 12;
 year--;
 }
 mday += timeutils_days_in_month(year, month);
 }
 while ((mp_uint_t)mday > timeutils_days_in_month(year, month)) {
 mday -= timeutils_days_in_month(year, month);
 if (++month == 13) {
 month = 1;
 year++;
 }
 }
 return timeutils_seconds_since_epoch(year, month, mday, hours, minutes, seconds);
}