////////////////////////////////////////////////////////////////////////////////
/// 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 Jan Christoph Uhde
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_GENERAL_SERVER_VST_COMM_TASK_H
#define ARANGOD_GENERAL_SERVER_VST_COMM_TASK_H 1

#include "Basics/Common.h"
#include "GeneralServer/GeneralCommTask.h"
#include "lib/Rest/VstMessage.h"
#include "lib/Rest/VstRequest.h"
#include "lib/Rest/VstResponse.h"

#include <stdexcept>

namespace arangodb {

namespace rest {

class VstCommTask final : public GeneralCommTask {
 public:
  VstCommTask(GeneralServer& server, std::unique_ptr<Socket> socket, 
              ConnectionInfo&&, double timeout,
              ProtocolVersion protocolVersion, bool skipSocketInit = false);

  arangodb::Endpoint::TransportType transportType() override {
    return arangodb::Endpoint::TransportType::VST;
  }

  // whether or not this task can mix sync and async I/O
  bool canUseMixedIO() const override;

 protected:
  // read data check if chunk and message are complete
  // if message is complete execute a request
  bool processRead(double startTime) override;

  std::unique_ptr<GeneralResponse> createResponse(rest::ResponseCode,
                                                  uint64_t messageId) override final;

  // @brief send simple response including response body
  void addSimpleResponse(rest::ResponseCode, rest::ContentType, uint64_t messageId,
                         velocypack::Buffer<uint8_t>&&) override;

  // convert from GeneralResponse to VstResponse ad dispatch request to class
  // internal addResponse
  void addResponse(GeneralResponse&, RequestStatistics*) override;

  bool allowDirectHandling() const override final { return false; }

 private:
  // process the VST 1000 request type
  void handleAuthHeader(VPackSlice const& header, uint64_t messageId);

  // reets the internal state this method can be called to clean up when the
  // request handling aborts prematurely
  void closeTask(rest::ResponseCode code = rest::ResponseCode::SERVER_ERROR);

 private:
  using MessageID = uint64_t;

  struct IncompleteVPackMessage {
    IncompleteVPackMessage(uint32_t length, std::size_t numberOfChunks)
        : _length(length),
          _buffer(_length),
          _numberOfChunks(numberOfChunks),
          _currentChunk(0) {}
    uint32_t _length;  // length of total message in bytes
    VPackBuffer<uint8_t> _buffer;
    std::size_t _numberOfChunks;
    std::size_t _currentChunk;
  };
  std::unordered_map<MessageID, IncompleteVPackMessage> _incompleteMessages;

  static size_t const _bufferLength = 4096UL;
  static size_t const _chunkMaxBytes = 1000UL;
  struct ProcessReadVariables {
    ProcessReadVariables()
        : _currentChunkLength(0),
          _readBufferOffset(0),
          _cleanupLength(_bufferLength - _chunkMaxBytes - 1) {}
    uint32_t _currentChunkLength;  // size of chunk processed or 0 when
                                   // expecting new chunk
    size_t _readBufferOffset;    // data up to this position has been processed
    std::size_t _cleanupLength;  // length of data after that the read buffer
                                 // will be cleaned
  };
  ProcessReadVariables _processReadVariables;

  struct ChunkHeader {
    std::size_t _headerLength;
    uint32_t _chunkLength;
    uint32_t _chunk;
    uint64_t _messageID;
    uint64_t _messageLength;
    bool _isFirst;
  };
  bool isChunkComplete(char*);    // sub-function of processRead
  ChunkHeader readChunkHeader();  // sub-function of processRead
  void replyToIncompleteMessages();

  // Returns true if and only if there was no error, if false is returned,
  // the connection is closed
  bool getMessageFromSingleChunk(ChunkHeader const& chunkHeader,
                                 VstInputMessage& message, bool& doExecute,
                                 char const* vpackBegin, char const* chunkEnd);

  // Returns true if and only if there was no error, if false is returned,
  // the connection is closed
  bool getMessageFromMultiChunks(ChunkHeader const& chunkHeader,
                                 VstInputMessage& message, bool& doExecute,
                                 char const* vpackBegin, char const* chunkEnd);

 private:
  /// Is the current user authorized
  bool _authorized;
  rest::AuthenticationMethod _authMethod;
  ProtocolVersion _protocolVersion;
  uint32_t _maxChunkSize;
};
}  // namespace rest
}  // namespace arangodb

#endif