////////////////////////////////////////////////////////////////////////////////
/// 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 Steemann
////////////////////////////////////////////////////////////////////////////////

#include "AsyncJobManager.h"

#include "Basics/ReadLocker.h"
#include "Basics/WriteLocker.h"
#include "HttpServer/HttpHandler.h"
#include "HttpServer/HttpServerJob.h"
#include "Logger/Logger.h"
#include "Rest/HttpResponse.h"

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

////////////////////////////////////////////////////////////////////////////////
/// @brief AsyncCallbackContext
////////////////////////////////////////////////////////////////////////////////

class arangodb::rest::AsyncCallbackContext {
 public:
  explicit AsyncCallbackContext(std::string const& coordHeader)
      : _coordHeader(coordHeader), _response(nullptr) {}

  ~AsyncCallbackContext() {
    if (_response != nullptr) {
      delete _response;
    }
  }

 public:
  //////////////////////////////////////////////////////////////////////////////
  /// @brief gets the coordinator header
  //////////////////////////////////////////////////////////////////////////////

  std::string& getCoordinatorHeader() { return _coordHeader; }

 private:
  //////////////////////////////////////////////////////////////////////////////
  /// @brief coordinator header
  //////////////////////////////////////////////////////////////////////////////

  std::string _coordHeader;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief http response
  //////////////////////////////////////////////////////////////////////////////

  HttpResponse* _response;
};

////////////////////////////////////////////////////////////////////////////////
/// @brief constructor for an unspecified job result
////////////////////////////////////////////////////////////////////////////////

AsyncJobResult::AsyncJobResult()
    : _jobId(0),
      _response(nullptr),
      _stamp(0.0),
      _status(JOB_UNDEFINED),
      _ctx(nullptr) {}

////////////////////////////////////////////////////////////////////////////////
/// @brief constructor for a specific job result
////////////////////////////////////////////////////////////////////////////////

AsyncJobResult::AsyncJobResult(IdType jobId, HttpResponse* response,
                               double stamp, Status status,
                               AsyncCallbackContext* ctx)
    : _jobId(jobId),
      _response(response),
      _stamp(stamp),
      _status(status),
      _ctx(ctx) {}

AsyncJobResult::~AsyncJobResult() {}

AsyncJobManager::AsyncJobManager(callback_fptr callback)
    : _lock(), _jobs(), callback(callback) {}

AsyncJobManager::~AsyncJobManager() {
  // remove all results that haven't been fetched
  deleteJobResults();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the result of an async job
////////////////////////////////////////////////////////////////////////////////

HttpResponse* AsyncJobManager::getJobResult(AsyncJobResult::IdType jobId,
                                            AsyncJobResult::Status& status,
                                            bool removeFromList) {
  WRITE_LOCKER(writeLocker, _lock);

  auto it = _jobs.find(jobId);

  if (it == _jobs.end()) {
    status = AsyncJobResult::JOB_UNDEFINED;
    return nullptr;
  }

  HttpResponse* response = (*it).second._response;
  status = (*it).second._status;

  if (status == AsyncJobResult::JOB_PENDING) {
    return nullptr;
  }

  if (!removeFromList) {
    return nullptr;
  }

  // remove the job from the list
  _jobs.erase(it);
  return response;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief deletes the result of an async job
////////////////////////////////////////////////////////////////////////////////

bool AsyncJobManager::deleteJobResult(AsyncJobResult::IdType jobId) {
  WRITE_LOCKER(writeLocker, _lock);

  auto it = _jobs.find(jobId);

  if (it == _jobs.end()) {
    return false;
  }

  HttpResponse* response = (*it).second._response;

  if (response != nullptr) {
    delete response;
  }

  // remove the job from the list
  _jobs.erase(it);
  return true;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief deletes all results
////////////////////////////////////////////////////////////////////////////////

void AsyncJobManager::deleteJobResults() {
  WRITE_LOCKER(writeLocker, _lock);

  auto it = _jobs.begin();

  while (it != _jobs.end()) {
    HttpResponse* response = (*it).second._response;

    if (response != nullptr) {
      delete response;
    }

    ++it;
  }

  _jobs.clear();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief deletes expired results
////////////////////////////////////////////////////////////////////////////////

void AsyncJobManager::deleteExpiredJobResults(double stamp) {
  WRITE_LOCKER(writeLocker, _lock);

  auto it = _jobs.begin();

  while (it != _jobs.end()) {
    AsyncJobResult ajr = (*it).second;

    if (ajr._stamp < stamp) {
      HttpResponse* response = ajr._response;

      if (response != nullptr) {
        delete response;
      }

      _jobs.erase(it++);
    } else {
      ++it;
    }
  }
}

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the list of pending jobs
////////////////////////////////////////////////////////////////////////////////

std::vector<AsyncJobResult::IdType> AsyncJobManager::pending(size_t maxCount) {
  return byStatus(AsyncJobResult::JOB_PENDING, maxCount);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the list of done jobs
////////////////////////////////////////////////////////////////////////////////

std::vector<AsyncJobResult::IdType> AsyncJobManager::done(size_t maxCount) {
  return byStatus(AsyncJobResult::JOB_DONE, maxCount);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the list of jobs by status
////////////////////////////////////////////////////////////////////////////////

std::vector<AsyncJobResult::IdType> AsyncJobManager::byStatus(
    AsyncJobResult::Status status, size_t maxCount) {
  std::vector<AsyncJobResult::IdType> jobs;

  {
    size_t n = 0;
    READ_LOCKER(readLocker, _lock);
    auto it = _jobs.begin();

    // iterate the list. the list is sorted by id
    while (it != _jobs.end()) {
      AsyncJobResult::IdType jobId = (*it).first;

      if ((*it).second._status == status) {
        jobs.emplace_back(jobId);

        if (++n >= maxCount) {
          break;
        }
      }

      ++it;
    }
  }

  return jobs;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief initializes an async job
////////////////////////////////////////////////////////////////////////////////

void AsyncJobManager::initAsyncJob(HttpServerJob* job, char const* hdr) {
  AsyncCallbackContext* ctx = nullptr;

  if (hdr != nullptr) {
    LOG(DEBUG) << "Found header X-Arango-Coordinator in async request";
    ctx = new AsyncCallbackContext(std::string(hdr));
  }

  AsyncJobResult ajr(job->jobId(), nullptr, TRI_microtime(),
                     AsyncJobResult::JOB_PENDING, ctx);

  WRITE_LOCKER(writeLocker, _lock);

  _jobs.emplace(job->jobId(), ajr);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief finishes the execution of an async job
////////////////////////////////////////////////////////////////////////////////

void AsyncJobManager::finishAsyncJob(AsyncJobResult::IdType jobId,
                                     HttpResponse* response) {
  double const now = TRI_microtime();
  AsyncCallbackContext* ctx = nullptr;

  {
    WRITE_LOCKER(writeLocker, _lock);
    auto it = _jobs.find(jobId);

    if (it == _jobs.end()) {
      delete response;
      return;
    } else {
      (*it).second._response = response;
      (*it).second._status = AsyncJobResult::JOB_DONE;
      (*it).second._stamp = now;

      ctx = (*it).second._ctx;

      if (ctx != nullptr) {
        // we have found a context object, so we can immediately remove the job
        // from the list of "done" jobs
        _jobs.erase(it);
      }
    }
  }

  // If there is a callback context, the job is no longer in the
  // list of "done" jobs, so we have to free the response and the
  // callback context:

  if (nullptr != ctx && nullptr != callback) {
    callback(ctx->getCoordinatorHeader(), response);
    delete ctx;

    if (response != nullptr) {
      delete response;
    }
  }
}