// Copyright 2016 Google Inc. All Rights Reserved.

//

// 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

//

//   https://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 CCTZ_TIME_ZONE_IF_H_

#define CCTZ_TIME_ZONE_IF_H_

#include <chrono>

#include <cstdint>

#include <memory>

#include <string>

#include "cctz/civil_time.h"

#include "cctz/time_zone.h"

namespace cctz {

// A simple interface used to hide time-zone complexities from time_zone::Impl.

// Subclasses implement the functions for civil-time conversions in the zone.

class TimeZoneIf {

 public:

  // A factory function for TimeZoneIf implementations.

  static std::unique_ptr<TimeZoneIf> Load(const std::string& name);

  virtual ~TimeZoneIf();

  virtual time_zone::absolute_lookup BreakTime(

      const time_point<seconds>& tp) const = 0;

  virtual time_zone::civil_lookup MakeTime(

      const civil_second& cs) const = 0;

  virtual bool NextTransition(const time_point<seconds>& tp,

                              time_zone::civil_transition* trans) const = 0;

  virtual bool PrevTransition(const time_point<seconds>& tp,

                              time_zone::civil_transition* trans) const = 0;

  virtual std::string Version() const = 0;

  virtual std::string Description() const = 0;

 protected:

  TimeZoneIf() {}

};

// Convert between time_point<seconds> and a count of seconds since the

// Unix epoch.  We assume that the std::chrono::system_clock and the

// Unix clock are second aligned, and that the results are representable.

// (That is, that they share an epoch, which is required since C++20.)

inline std::int_fast64_t ToUnixSeconds(const time_point<seconds>& tp) {

  return (tp - std::chrono::time_point_cast<seconds>(

                   std::chrono::system_clock::from_time_t(0))).count();

}

inline time_point<seconds> FromUnixSeconds(std::int_fast64_t t) {

  return std::chrono::time_point_cast<seconds>(

             std::chrono::system_clock::from_time_t(0)) + seconds(t);

}

}  // namespace cctz

#endif  // CCTZ_TIME_ZONE_IF_H_