ah-date.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  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
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  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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*/
 
# ifndef AH_DATE_H
# define AH_DATE_H
 
# include <array>
# include <ctime>
# include <limits>
# include <string>
 
# include <ah-errors.H>
 
namespace Aleph
{
  namespace detail
  {
    inline constexpr size_t tm_epoch_year = 1900u;
    inline constexpr size_t max_supported_year =
      static_cast<size_t>(std::numeric_limits<int>::max()) + tm_epoch_year;
    inline constexpr time_t seconds_per_day =
      static_cast<time_t>(24 * 60 * 60);
  } // namespace detail
 
  [[nodiscard]] inline bool is_leap_year(const size_t yy) noexcept
  {
    return (yy % 4 == 0 and yy % 100 != 0) or (yy % 400 == 0);
  }
 
  [[nodiscard]] inline bool valid_month(const size_t mm) noexcept
  {
    return mm >= 1 and mm <= 12;
  }
 
  [[nodiscard]] inline bool valid_day(const size_t yy, const size_t mm, const size_t dd) noexcept
  {
    if (not valid_month(mm) or dd == 0)
      return false;
 
    static constexpr std::array<size_t, 12> month_lengths =
      {31u, 28u, 31u, 30u, 31u, 30u, 31u, 31u, 30u, 31u, 30u, 31u};
 
    const size_t base = month_lengths[mm - 1];
    const size_t extra = (mm == 2 and is_leap_year(yy)) ? 1u : 0u;
 
    return dd <= base + extra;
  }
 
  inline time_t to_time_t(const size_t dd, const size_t mm, const size_t yy)
  {
    ah_domain_error_if(yy < detail::tm_epoch_year or
                       yy > detail::max_supported_year)
      << "Year " << yy << " is outside the supported range ["
      << detail::tm_epoch_year << ", " << detail::max_supported_year << ']';
 
    ah_domain_error_if(not valid_day(yy, mm, dd))
      << "Invalid date components"
      << " (dd=" << dd << ", mm=" << mm << ", yy=" << yy << ')';
 
    std::tm tm{};
    tm.tm_mday = static_cast<int>(dd);
    tm.tm_mon = static_cast<int>(mm) - 1;
    tm.tm_year = static_cast<int>(yy) - 1900;
    tm.tm_isdst = -1;
 
    return std::mktime(&tm);
  }
 
  inline time_t to_time_t(const std::string & s, const std::string & format)
  {
    std::tm tm{};
    const char *res = ::strptime(s.c_str(), format.c_str(), &tm);
    ah_domain_error_if(res == nullptr or *res != '\0')
      << "Input string '" << s << "' does not match format '" << format << '\'';
 
    tm.tm_isdst = -1;
    return std::mktime(&tm);
  }
 
  inline time_t to_time_t(const std::string & s)
  {
    return to_time_t(s, "%Y-%m-%d %H:%M:%S");
  }
 
  inline size_t to_days(const time_t t)
  {
    ah_domain_error_if(t < 0)
      << "to_days() expects non-negative timestamps";
 
    return static_cast<size_t>(t / detail::seconds_per_day);
  }
 
  inline std::string to_string(const time_t t, const std::string & format)
  {
    const std::tm *tm_ptr = std::localtime(&t);
    ah_runtime_error_if(tm_ptr == nullptr) << "localtime() failed";
 
    std::tm tm = *tm_ptr;
    char buff[128]{};
    const size_t written = std::strftime(buff, sizeof(buff), format.c_str(), &tm);
    ah_range_error_if(written == 0)
      << "Unable to format time using pattern '" << format << "'";
 
    return std::string(buff, written);
  }
 
}
 
# endif