text: /*
   *  Copyright (c) 2018, The OpenThread Authors.
   *  All rights reserved.
   *
   *  Redistribution and use in source and binary forms, with or without
   *  modification, are permitted provided that the following conditions are met:
   *  1. Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the following disclaimer.
   *  2. Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in the
   *     documentation and/or other materials provided with the distribution.
   *  3. Neither the name of the copyright holder nor the
   *     names of its contributors may be used to endorse or promote products
   *     derived from this software without specific prior written permission.
   *
   *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
   *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   *  POSSIBILITY OF SUCH DAMAGE.
   */
  
  /**
   * @file
   *   This file includes definitions for Thread network time synchronization service.
   */
  
  #ifndef TIME_SYNC_HPP_
  #define TIME_SYNC_HPP_
  
  #include "openthread-core-config.h"
  
  #if OPENTHREAD_CONFIG_ENABLE_TIME_SYNC
  #include <openthread/network_time.h>
  
  #include "common/locator.hpp"
  #include "common/message.hpp"
  #include "common/notifier.hpp"
  #include "common/timer.hpp"
  
  namespace ot {
  
  /**
   * This class implements OpenThread Time Synchronization Service.
   *
   */
  class TimeSync : public InstanceLocator
  {
  public:
      /**
       * This constructor initializes the object.
       *
       */
      TimeSync(Instance &aInstance);
  
      /**
       * Get the Thread network time.
       *
       * @param[inout] aNetworkTime  The Thread network time in microseconds.
       *
       * @returns The time synchronization status.
       *
       */
      otNetworkTimeStatus GetTime(uint64_t &aNetworkTime) const;
  
      /**
       * Handle the message which includes time synchronization information.
       *
       * @param[in] aMessage  The message which includes time synchronization information.
       *
       */
      void HandleTimeSyncMessage(const Message &aMessage);
  
  #if OPENTHREAD_FTD
      /**
       * Send a time synchronization message when it is required.
       *
       * Note: A time synchronization message is required in following cases:
       *       1. Leader send time sync message periodically;
       *       2. Router(except Leader) received a time sync message with newer sequence;
       *       3. Router received a time sync message with older sequence.
       *
       */
      void ProcessTimeSync(void);
  #endif
  
      /**
       * This method gets the time synchronization sequence.
       *
       * @returns The time synchronization sequence.
       *
       */
      uint8_t GetTimeSyncSeq(void) const { return mTimeSyncSeq; };
  
      /**
       * This method gets the time offset to the Thread network time.
       *
       * @returns The time offset to the Thread network time, in microseconds.
       *
       */
      int64_t GetNetworkTimeOffset(void) const { return mNetworkTimeOffset; };
  
      /**
       * Set the time synchronization period.
       *
       * @param[in] aTimeSyncPeriod   The time synchronization period, in seconds.
       *
       */
      void SetTimeSyncPeriod(uint16_t aTimeSyncPeriod) { mTimeSyncPeriod = aTimeSyncPeriod; }
  
      /**
       * Get the time synchronization period.
       *
       * @returns The time synchronization period, in seconds.
       *
       */
      uint16_t GetTimeSyncPeriod(void) const { return mTimeSyncPeriod; }
  
      /**
       * Set the time synchronization XTAL accuracy threshold for Router.
       *
       * @param[in] aXtalThreshold   The XTAL accuracy threshold for Router, in PPM.
       *
       */
      void SetXtalThreshold(uint16_t aXtalThreshold) { mXtalThreshold = aXtalThreshold; }
  
      /**
       * Get the time synchronization XTAL accuracy threshold for Router.
       *
       * @returns The XTAL accuracy threshold for Router, in PPM.
       *
       */
      uint16_t GetXtalThreshold(void) const { return mXtalThreshold; }
  
      /**
       * Set the time sync callback to be notified of a network time update.
       *
       * @param[in] aCallback The callback to be called when time sync is handled.
       * @param[in] aCallbackContext The context to be passed to callback.
       *
       */
      void SetTimeSyncCallback(otNetworkTimeSyncCallbackFn aCallback, void *aCallbackContext)
      {
          mTimeSyncCallback        = aCallback;
          mTimeSyncCallbackContext = aCallbackContext;
      }
  
      /**
       * Callback to be called when thread state changes.
       *
       * @param[in] aFlags Flags that denote the state change events.
       *
       */
      void HandleStateChanged(otChangedFlags aFlags);
  
      /**
       * Callback to be called when timer expires.
       *
       */
      void HandleTimeout(void);
  
  private:
      /**
       * Callback to be called when thread state changes.
       *
       * @param[in] aCallback Callback context.
       * @param[in] aFlags Flags that denote the state change events.
       *
       */
      static void HandleStateChanged(Notifier::Callback &aCallback, otChangedFlags aFlags);
  
      /**
       * Callback to be called when timer expires.
       *
       * @param[in] aTimer The corresponding timer.
       *
       */
      static void HandleTimeout(Timer &aTimer);
  
      /**
       * Check and handle any status change, and notify observers if applicable.
       *
       * @param[in] aNotifyTimeUpdated True to denote that observers should be notified due to a time change, false
       * otherwise.
       *
       */
      void CheckAndHandleChanges(bool aNotifyTimeUpdated);
  
      /**
       * Increase the time synchronization sequence.
       *
       */
      void IncrementTimeSyncSeq(void);
  
      /**
       * Notify any listener of a network time sync update event.
       *
       */
      void NotifyTimeSyncCallback(void);
  
      bool     mTimeSyncRequired; ///< Indicate whether or not a time synchronization message is required.
      uint8_t  mTimeSyncSeq;      ///< The time synchronization sequence.
      uint16_t mTimeSyncPeriod;   ///< The time synchronization period.
      uint16_t mXtalThreshold;    ///< The XTAL accuracy threshold for a device to become a Router, in PPM.
  #if OPENTHREAD_FTD
      uint32_t mLastTimeSyncSent; ///< The time when the last time synchronization message was sent.
  #endif
      uint32_t mLastTimeSyncReceived; ///< The time when the last time synchronization message was received.
      int64_t  mNetworkTimeOffset;    ///< The time offset to the Thread Network time
      otNetworkTimeSyncCallbackFn
                          mTimeSyncCallback; ///< The callback to be called when time sync is handled or status updated.
      void *              mTimeSyncCallbackContext; ///< The context to be passed to callback.
      Notifier::Callback  mNotifierCallback;        ///< Callback for thread state changes.
      TimerMilli          mTimer;                   ///< Timer for checking if a resync is required.
      otNetworkTimeStatus mCurrentStatus;           ///< Current network time status.
  };
  
  /**
   * @}
   */
  
  } // namespace ot
  
  #endif // OPENTHREAD_CONFIG_ENABLE_TIME_SYNC
  
  #endif // TIME_SYNC_HPP_
  