// 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_INFO_H_

#define CCTZ_TIME_ZONE_INFO_H_

#include <atomic>

#include <cstddef>

#include <cstdint>

#include <string>

#include <vector>

#include "cctz/civil_time.h"

#include "cctz/time_zone.h"

#include "cctz/zone_info_source.h"

#include "time_zone_if.h"

#include "tzfile.h"

namespace cctz {

// A transition to a new UTC offset.

struct Transition {

  std::int_least64_t unix_time;   // the instant of this transition

  std::uint_least8_t type_index;  // index of the transition type

  civil_second civil_sec;         // local civil time of transition

  civil_second prev_civil_sec;    // local civil time one second earlier

  struct ByUnixTime {

    inline bool operator()(const Transition& lhs, const Transition& rhs) const {

      return lhs.unix_time < rhs.unix_time;

    }

  };

  struct ByCivilTime {

    inline bool operator()(const Transition& lhs, const Transition& rhs) const {

      return lhs.civil_sec < rhs.civil_sec;

    }

  };

};

// The characteristics of a particular transition.

struct TransitionType {

  std::int_least32_t utc_offset;  // the new prevailing UTC offset

  civil_second civil_max;         // max convertible civil time for offset

  civil_second civil_min;         // min convertible civil time for offset

  bool is_dst;                    // did we move into daylight-saving time

  std::uint_least8_t abbr_index;  // index of the new abbreviation

};

// A time zone backed by the IANA Time Zone Database (zoneinfo).

class TimeZoneInfo : public TimeZoneIf {

 public:

  TimeZoneInfo() = default;

  TimeZoneInfo(const TimeZoneInfo&) = delete;

  TimeZoneInfo& operator=(const TimeZoneInfo&) = delete;

  // Loads the zoneinfo for the given name, returning true if successful.

  bool Load(const std::string& name);

  // TimeZoneIf implementations.

  time_zone::absolute_lookup BreakTime(

      const time_point<seconds>& tp) const override;

  time_zone::civil_lookup MakeTime(

      const civil_second& cs) const override;

  bool NextTransition(const time_point<seconds>& tp,

                      time_zone::civil_transition* trans) const override;

  bool PrevTransition(const time_point<seconds>& tp,

                      time_zone::civil_transition* trans) const override;

  std::string Version() const override;

  std::string Description() const override;

 private:

  struct Header {  // counts of:

    std::size_t timecnt;     // transition times

    std::size_t typecnt;     // transition types

    std::size_t charcnt;     // zone abbreviation characters

    std::size_t leapcnt;     // leap seconds (we expect none)

    std::size_t ttisstdcnt;  // UTC/local indicators (unused)

    std::size_t ttisutcnt;   // standard/wall indicators (unused)

    bool Build(const tzhead& tzh);

    std::size_t DataLength(std::size_t time_len) const;

  };

  bool GetTransitionType(std::int_fast32_t utc_offset, bool is_dst,

                         const std::string& abbr, std::uint_least8_t* index);

  bool EquivTransitions(std::uint_fast8_t tt1_index,

                        std::uint_fast8_t tt2_index) const;

  bool ExtendTransitions();

  bool ResetToBuiltinUTC(const seconds& offset);

  bool Load(ZoneInfoSource* zip);

  // Helpers for BreakTime() and MakeTime().

  time_zone::absolute_lookup LocalTime(std::int_fast64_t unix_time,

                                       const TransitionType& tt) const;

  time_zone::absolute_lookup LocalTime(std::int_fast64_t unix_time,

                                       const Transition& tr) const;

  time_zone::civil_lookup TimeLocal(const civil_second& cs,

                                    year_t c4_shift) const;

  std::vector<Transition> transitions_;  // ordered by unix_time and civil_sec

  std::vector<TransitionType> transition_types_;  // distinct transition types

  std::uint_fast8_t default_transition_type_;  // for before first transition

  std::string abbreviations_;  // all the NUL-terminated abbreviations

  std::string version_;      // the tzdata version if available

  std::string future_spec_;  // for after the last zic transition

  bool extended_;            // future_spec_ was used to generate transitions

  year_t last_year_;         // the final year of the generated transitions

  // We remember the transitions found during the last BreakTime() and

  // MakeTime() calls. If the next request is for the same transition we

  // will avoid re-searching.

  mutable std::atomic<std::size_t> local_time_hint_ = {};  // BreakTime() hint

  mutable std::atomic<std::size_t> time_local_hint_ = {};  // MakeTime() hint

};

}  // namespace cctz

#endif  // CCTZ_TIME_ZONE_INFO_H_