text: // Licensed to the Apache Software Foundation (ASF) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The ASF licenses this file
  // to you 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.
  
  #pragma once
  
  #include <dsn/utility/singleton.h>
  
  namespace dsn {
  namespace replication {
  
  bool validate_app_env(const std::string &env_name,
                        const std::string &env_value,
                        std::string &hint_message);
  
  class app_env_validator : public utils::singleton<app_env_validator>
  {
  public:
      app_env_validator() { register_all_validators(); }
      bool validate_app_env(const std::string &env_name,
                            const std::string &env_value,
                            std::string &hint_message);
  
  private:
      void register_all_validators();
  
      using validator_func = std::function<bool(const std::string &, std::string &)>;
      std::map<const std::string, validator_func> _validator_funcs;
  };
  
  } // namespace replication
  } // namespace dsn
  