// Use of this source code is governed by a BSD-style license

// that can be found in the License file.

//

// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include "muduo/base/Date.h"

#include <stdio.h>  // snprintf

#include <time.h>  // struct tm

namespace muduo

{

namespace detail

{

char require_32_bit_integer_at_least[sizeof(int) >= sizeof(int32_t) ? 1 : -1];

// algorithm and explanation see:

// http://www.faqs.org/faqs/calendars/faq/part2/

// http://blog.csdn.net/Solstice

int getJulianDayNumber(int year, int month, int day)

{

  (void) require_32_bit_integer_at_least; // no warning please

  int a = (14 - month) / 12;

  int y = year + 4800 - a;

  int m = month + 12 * a - 3;

  return day + (153*m + 2) / 5 + y*365 + y/4 - y/100 + y/400 - 32045;

}

struct Date::YearMonthDay getYearMonthDay(int julianDayNumber)

{

  int a = julianDayNumber + 32044;

  int b = (4 * a + 3) / 146097;

  int c = a - ((b * 146097) / 4);

  int d = (4 * c + 3) / 1461;

  int e = c - ((1461 * d) / 4);

  int m = (5 * e + 2) / 153;

  Date::YearMonthDay ymd;

  ymd.day = e - ((153 * m + 2) / 5) + 1;

  ymd.month = m + 3 - 12 * (m / 10);

  ymd.year = b * 100 + d - 4800 + (m / 10);

  return ymd;

}

}  // namespace detail

const int Date::kJulianDayOf1970_01_01 = detail::getJulianDayNumber(1970, 1, 1);

}  // namespace muduo

using namespace muduo;

using namespace muduo::detail;

Date::Date(int y, int m, int d)

  : julianDayNumber_(getJulianDayNumber(y, m, d))

{

}

Date::Date(const struct tm& t)

  : julianDayNumber_(getJulianDayNumber(

        t.tm_year+1900,

        t.tm_mon+1,

        t.tm_mday))

{

}

string Date::toIsoString() const

{

  char buf[32];

  YearMonthDay ymd(yearMonthDay());

  snprintf(buf, sizeof buf, "%4d-%02d-%02d", ymd.year, ymd.month, ymd.day);

  return buf;

}

Date::YearMonthDay Date::yearMonthDay() const

{

  return getYearMonthDay(julianDayNumber_);

}