////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// 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.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Dr. Frank Celler
/// @author Achim Brandt
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_GENERAL_SERVER_GENERAL_COMM_TASK_H
#define ARANGOD_GENERAL_SERVER_GENERAL_COMM_TASK_H 1

#include "Scheduler/SocketTask.h"

#include <openssl/ssl.h>

#include "Basics/Mutex.h"
#include "Basics/MutexLocker.h"
#include "Basics/StringBuffer.h"
#include "Scheduler/Socket.h"

namespace arangodb {
class GeneralRequest;
class GeneralResponse;

namespace rest {
class GeneralServer;

//
// The flow of events is as follows:
//
// (1) After reading data from the client, `processRead()` is called. Each
//     sub-class of `GeneralCommTask` must implement this method. As long as the
//     function returns true, it is called again in a loop. Returning false
//     signals that new data has to be received in order to continue and that
//     all available data has been processed
//
// (3) As soon as `processRead()` detects that it has read a complete request,
//     it must create an instance of a sub-class of `GeneralRequest` and
//     `GeneralResponse`. Then it must call `executeRequest(...)` to start the
//     execution of the request.
//
// (4) `executeRequest(...)` will create a handler. A handler is responsible for
//     executing the request. It will take the `request` instance and executes a
//     plan to generate a response. It is possible, that one request generates a
//     response and still does some work afterwards. It is even possible, that a
//     request generates a push stream.
//
//     As soon as a response is available, `handleResponse()` will be called.
//     This in turn calls `addResponse()` which must be implemented in the
//     sub-class. It will be called with an response object and an indicator if
//     an error has occurred.
//
//     It is the responsibility of the sub-class to govern what is supported.
//     For example, HTTP will only support one active request executing at a
//     time until the final response has been send out.
//
//     VelocyPack on the other hand, allows multiple active requests. Partial
//     responses are identified by a request id.
//
// (5) Error handling: In case of an error `handleSimpleError()` will be
//     called. This will call `addResponse()` with an error indicator, which in
//     turn will end the responding request.
//

class GeneralCommTask : public SocketTask {
  GeneralCommTask(GeneralCommTask const&) = delete;
  GeneralCommTask const& operator=(GeneralCommTask const&) = delete;

 public:
  GeneralCommTask(EventLoop, GeneralServer*, std::unique_ptr<Socket>,
                  ConnectionInfo&&, double keepAliveTimeout,
                  bool skipSocketInit = false);

  ~GeneralCommTask();

  virtual arangodb::Endpoint::TransportType transportType() = 0;

 protected:
  virtual std::unique_ptr<GeneralResponse> createResponse(
      rest::ResponseCode, uint64_t messageId) = 0;

  virtual void addResponse(GeneralResponse*, RequestStatistics*) = 0;

 protected:
  void executeRequest(std::unique_ptr<GeneralRequest>&&,
                      std::unique_ptr<GeneralResponse>&&);

  void processResponse(GeneralResponse*);

  virtual void handleSimpleError(rest::ResponseCode, uint64_t messageId) = 0;

  virtual void handleSimpleError(rest::ResponseCode, int code,
                                 std::string const& errorMessage,
                                 uint64_t messageId) = 0;

  void setStatistics(uint64_t, RequestStatistics*);
  RequestStatistics* acquireStatistics(uint64_t);
  RequestStatistics* statistics(uint64_t);
  RequestStatistics* stealStatistics(uint64_t);
  void transferStatisticsTo(uint64_t, RestHandler*);

 protected:
  GeneralServer* const _server;

  // protocol to use http, vst
  char const* _protocol = "unknown";
  rest::ProtocolVersion _protocolVersion = rest::ProtocolVersion::UNKNOWN;

  arangodb::Mutex _statisticsMutex;
  std::unordered_map<uint64_t, RequestStatistics*> _statisticsMap;

 private:
  bool handleRequest(std::shared_ptr<RestHandler>);
  void handleRequestDirectly(std::shared_ptr<RestHandler>);
  bool handleRequestAsync(std::shared_ptr<RestHandler>,
                          uint64_t* jobId = nullptr);
};
}
}

#endif