text: /*
   * Copyright 2021 4Paradigm
   *
   * 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 SRC_ZK_DIST_LOCK_H_
  #define SRC_ZK_DIST_LOCK_H_
  
  #include <atomic>
  #include <mutex> // NOLINT
  #include <vector>
  #include <string>
  #include "boost/function.hpp"
  #include "common/thread_pool.h"
  #include "zk/zk_client.h"
  
  using ::baidu::common::ThreadPool;
  using ::fedb::zk::ZkClient;
  
  namespace fedb {
  namespace zk {
  
  enum LockState { kLocked, kLostLock, kTryLock };
  
  typedef boost::function<void()> NotifyCallback;
  class DistLock {
   public:
      DistLock(const std::string& root_path, ZkClient* zk_client,
               NotifyCallback on_locked_cl, NotifyCallback on_lost_lock_cl,
               const std::string& lock_value);
  
      ~DistLock();
  
      void Lock();
  
      void Stop();
  
      bool IsLocked();
  
      void CurrentLockValue(std::string& value); // NOLINT
  
   private:
      void InternalLock();
      void HandleChildrenChanged(const std::vector<std::string>& children);
      void HandleChildrenChangedLocked(const std::vector<std::string>& children);
  
   private:
      // input args
      std::string root_path_;
      NotifyCallback on_locked_cl_;
      NotifyCallback on_lost_lock_cl_;
  
      // status
      std::mutex mu_;
      ZkClient* zk_client_;
      // sequence path from zookeeper
      std::string assigned_path_;
      std::atomic<LockState> lock_state_;
      ThreadPool pool_;
      std::atomic<bool> running_;
      std::string lock_value_;
      std::string current_lock_node_;
      std::string current_lock_value_;
      uint64_t client_session_term_;
  };
  
  }  // namespace zk
  }  // namespace fedb
  
  #endif  // SRC_ZK_DIST_LOCK_H_
  