zoned.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_ZONED_HPP
#define MTCORE_CALENDARS_ZONED_HPP
 
#include "mtcore.hpp"
#include "time.hpp"
 
namespace mtcore::calendars {
  struct TimeZone {
    struct OffsetHMS {
      u8 seconds = 0;
      u8 minutes = 0;
      i8 hours   = 0;
    } offsetVal                      = {};
    Optional<Slice<const char>> name = nullopt;
 
    [[nodiscard]] constexpr i64 offset_in_nanoseconds() const {
      const auto secs = offset_in_seconds();
      return static_cast<i64>(secs) * NANOS_PER_SECOND;
    }
 
    [[nodiscard]] constexpr i32 offset_in_seconds() const {
      const auto sign = (offsetVal.hours >= 0) ? 1 : -1;
      auto total      = static_cast<i32>(offsetVal.hours);
      total *= 60;
      total += offsetVal.minutes;
      total *= 60;
      total += offsetVal.seconds;
      total *= sign;
      return total;
    }
 
    [[nodiscard]] constexpr f64 offset_in_minutes() const { return static_cast<f64>(offset_in_seconds()) / 60.; }
 
    [[nodiscard]] constexpr f64 offset_in_hours() const { return offset_in_minutes() / 60.; }
 
    [[nodiscard]] constexpr auto offset() const { return offsetVal; }
 
    [[nodiscard]] constexpr Result<void, TimeValidationError> try_validate() const {
      if (offsetVal.seconds >= 60) {
        return error(TimeValidationError::INVALID_SECOND);
      }
      if (offsetVal.minutes >= 60) {
        return error(TimeValidationError::INVALID_MINUTE);
      }
      if (offsetVal.hours >= 24) {
        return error(TimeValidationError::INVALID_HOUR);
      }
      if (offsetVal.hours <= -24) {
        return error(TimeValidationError::INVALID_HOUR);
      }
      return success();
    }
 
    [[nodiscard]] constexpr auto operator<=>(const TimeZone &tz) const {
      if (const auto c = (offsetVal.hours <=> tz.offsetVal.hours); c != std::strong_ordering::equivalent) {
        return c;
      }
      if (const auto c = (offsetVal.minutes <=> tz.offsetVal.minutes); c != std::strong_ordering::equivalent) {
        return c;
      }
      if (const auto c = (offsetVal.seconds <=> tz.offsetVal.seconds); c != std::strong_ordering::equivalent) {
        return c;
      }
      return std::strong_ordering::equivalent;
    }
  };
 
  namespace zone {
    constexpr auto utc_name = "UTC";
    constexpr TimeZone utc() { return TimeZone{{}, slice_from(utc_name)}; }
  }  // namespace zone
}  // namespace mtcore::calendars
 
#endif  // MTCORE_CALENDARS_ZONED_HPP