egyptian.hpp

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/*
 
Copyright 2025 Matthew Tolman
 
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
 
   http://www.apache.org/licenses/LICENSE-2.0
 
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 
*/
 
#ifndef MTCORE_CALENDARS_EGYPTIAN_HPP
#define MTCORE_CALENDARS_EGYPTIAN_HPP
 
#include "mtcore_calendars/epochs.hpp"
#include "mtcore_calendars/fixed.hpp"
#include "mtcore_calendars/traits.hpp"
#include <string_view>
 
namespace mtcore::calendars::systems {
  struct Egyptian {
    static constexpr auto EPOCH            = EGYPTIAN_EPOCH;
    static constexpr std::string_view name = "Egyptian";
    enum class Month {
      Thoth = 1,
      Phaophi,
      Athyr,
      Choiak,
      Tybi,
      Mechir,
      Phamenoth,
      Pharmuthi,
      Pachon,
      Payni,
      Epiphi,
      Mesori,
 
      epagomenae
    };

    AstronomicalYear year = 0;
    Month month = Month::Thoth;
    u8 day = 1;
 
    [[nodiscard]] constexpr auto operator<=>(const Egyptian &o) const noexcept {
      if (const auto c = year <=> o.year; c != std::strong_ordering::equivalent) {
        return c;
      }
      if (const auto c = month <=> o.month; c != std::strong_ordering::equivalent) {
        return c;
      }
      if (const auto c = day <=> o.day; c != std::strong_ordering::equivalent) {
        return c;
      }
      return std::strong_ordering::equivalent;
    }
 
    [[nodiscard]] static constexpr Egyptian from_fixed(const Fixed &rdDate) noexcept {
      const auto days          = rdDate.day - EPOCH;
      const auto egyptianYear  = math::floor<double, int64_t>(static_cast<double>(days) / 365.0) + 1;
      const auto egyptianMonth = math::floor<double, int64_t>(math::mod(static_cast<double>(days), 365) / 30.0) + 1;
      const auto egyptianDay   = days - 365 * (egyptianYear - 1) - 30 * (egyptianMonth - 1) + 1;
      return Egyptian{static_cast<decltype(year)>(egyptianYear), static_cast<decltype(month)>(egyptianMonth),
                      static_cast<decltype(day)>(egyptianDay)};
    }
 
    [[nodiscard]] constexpr Fixed to_fixed() const noexcept {
      return Fixed{EPOCH + ((365 * (static_cast<i32>(year) - 1) + 30 * (static_cast<i32>(month) - 1) +
                             static_cast<i32>(day - 1)))};
    }
  };
 
  static_assert(IsDayCalendarSystem<Egyptian>);
}  // namespace mtcore::calendars::systems
 
#endif  // MTCORE_CALENDARS_EGYPTIAN_HPP