////////////////////////////////////////////////////////////////////////////////
/// 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
////////////////////////////////////////////////////////////////////////////////

#include "HttpHandler.h"

#include "Basics/StringUtils.h"
#include "Dispatcher/Dispatcher.h"
#include "Logger/Logger.h"
#include "Rest/HttpRequest.h"

using namespace arangodb;
using namespace arangodb::basics;
using namespace arangodb::rest;

namespace {
std::atomic_uint_fast64_t NEXT_HANDLER_ID(
    static_cast<uint64_t>(TRI_microtime() * 100000.0));
}

////////////////////////////////////////////////////////////////////////////////
/// @brief constructs a new handler
////////////////////////////////////////////////////////////////////////////////

HttpHandler::HttpHandler(HttpRequest* request)
    : _handlerId(NEXT_HANDLER_ID.fetch_add(1, std::memory_order_seq_cst)),
      _taskId(0),
      _request(request),
      _response(nullptr),
      _server(nullptr) {}

////////////////////////////////////////////////////////////////////////////////
/// @brief destructs a handler
////////////////////////////////////////////////////////////////////////////////

HttpHandler::~HttpHandler() {
  delete _request;
  delete _response;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the queue id
////////////////////////////////////////////////////////////////////////////////

size_t HttpHandler::queue() const {
#if 0
  // feature currently disabled because it is neither documented nor used
  bool found;
  std::string const& queue = _request->header(StaticStrings::Queue, found);

  if (found) {
    uint32_t n = StringUtils::uint32(queue);

    if (n == 0) {
      return Dispatcher::STANDARD_QUEUE;
    }

    return n + (Dispatcher::SYSTEM_QUEUE_SIZE - 1);
  }
#endif
  return Dispatcher::STANDARD_QUEUE;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief prepares for execution
////////////////////////////////////////////////////////////////////////////////

void HttpHandler::prepareExecute() {}

////////////////////////////////////////////////////////////////////////////////
/// @brief finalize the execution
////////////////////////////////////////////////////////////////////////////////

void HttpHandler::finalizeExecute() {}

////////////////////////////////////////////////////////////////////////////////
/// @brief tries to cancel an execution
////////////////////////////////////////////////////////////////////////////////

bool HttpHandler::cancel() { return false; }

////////////////////////////////////////////////////////////////////////////////
/// @brief adds a response
////////////////////////////////////////////////////////////////////////////////

void HttpHandler::addResponse(HttpHandler*) {
  // nothing by default
}

//////////////////////////////////////////////////////////////////////////////
/// @brief returns the id of the underlying task
//////////////////////////////////////////////////////////////////////////////

uint64_t HttpHandler::taskId() const { return _taskId; }

//////////////////////////////////////////////////////////////////////////////
/// @brief returns the event loop of the underlying task
//////////////////////////////////////////////////////////////////////////////

EventLoop HttpHandler::eventLoop() const { return _loop; }

//////////////////////////////////////////////////////////////////////////////
/// @brief sets the id of the underlying task or 0 to dettach
//////////////////////////////////////////////////////////////////////////////

void HttpHandler::setTaskId(uint64_t id, EventLoop loop) {
  _taskId = id;
  _loop = loop;
}

//////////////////////////////////////////////////////////////////////////////
/// @brief execution cycle including error handling and prepare
//////////////////////////////////////////////////////////////////////////////

HttpHandler::status_t HttpHandler::executeFull() {
  HttpHandler::status_t status(HttpHandler::HANDLER_FAILED);

  requestStatisticsAgentSetRequestStart();

#ifdef USE_DEV_TIMERS
  TRI_request_statistics_t::STATS = _statistics;
#endif
  
  try {
    prepareExecute();

    try {
      status = execute();
    } catch (Exception const& ex) {
      requestStatisticsAgentSetExecuteError();
      handleError(ex);
    } catch (std::bad_alloc const& ex) {
      requestStatisticsAgentSetExecuteError();
      Exception err(TRI_ERROR_OUT_OF_MEMORY, ex.what(), __FILE__, __LINE__);
      handleError(err);
    } catch (std::exception const& ex) {
      requestStatisticsAgentSetExecuteError();
      Exception err(TRI_ERROR_INTERNAL, ex.what(), __FILE__, __LINE__);
      handleError(err);
    } catch (...) {
      requestStatisticsAgentSetExecuteError();
      Exception err(TRI_ERROR_INTERNAL, __FILE__, __LINE__);
      handleError(err);
    }

    finalizeExecute();

    if (status._status != HANDLER_ASYNC && _response == nullptr) {
      Exception err(TRI_ERROR_INTERNAL, "no response received from handler",
                    __FILE__, __LINE__);

      handleError(err);
    }
  } catch (Exception const& ex) {
    status = HANDLER_FAILED;
    requestStatisticsAgentSetExecuteError();
    LOG(ERR) << "caught exception: " << DIAGNOSTIC_INFORMATION(ex);
  } catch (std::exception const& ex) {
    status = HANDLER_FAILED;
    requestStatisticsAgentSetExecuteError();
    LOG(ERR) << "caught exception: " << ex.what();
  } catch (...) {
    status = HANDLER_FAILED;
    requestStatisticsAgentSetExecuteError();
    LOG(ERR) << "caught exception";
  }

  if (status._status != HANDLER_ASYNC && _response == nullptr) {
    _response = new HttpResponse(GeneralResponse::ResponseCode::SERVER_ERROR);
  }

  requestStatisticsAgentSetRequestEnd();

#ifdef USE_DEV_TIMERS
  TRI_request_statistics_t::STATS = nullptr;
#endif
  
  return status;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief register the server object
////////////////////////////////////////////////////////////////////////////////

void HttpHandler::setServer(HttpHandlerFactory* server) { _server = server; }

////////////////////////////////////////////////////////////////////////////////
/// @brief return a pointer to the request
////////////////////////////////////////////////////////////////////////////////

HttpRequest const* HttpHandler::getRequest() const { return _request; }

////////////////////////////////////////////////////////////////////////////////
/// @brief steal the request
////////////////////////////////////////////////////////////////////////////////

HttpRequest* HttpHandler::stealRequest() {
  HttpRequest* tmp = _request;
  _request = nullptr;
  return tmp;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the response
////////////////////////////////////////////////////////////////////////////////

HttpResponse* HttpHandler::getResponse() const { return _response; }

////////////////////////////////////////////////////////////////////////////////
/// @brief steal the response
////////////////////////////////////////////////////////////////////////////////

HttpResponse* HttpHandler::stealResponse() {
  HttpResponse* tmp = _response;
  _response = nullptr;
  return tmp;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief create a new HTTP response
////////////////////////////////////////////////////////////////////////////////

void HttpHandler::createResponse(GeneralResponse::ResponseCode code) {
  // avoid having multiple responses. this would be a memleak
  delete _response;
  _response = nullptr;

  // create a "standard" (standalone) Http response
  _response = new HttpResponse(code);
}