/*
 * @project      The CERN Tape Archive (CTA)
 * @copyright    Copyright © 2021-2022 CERN
 * @license      This program is free software, distributed under the terms of the GNU General Public
 *               Licence version 3 (GPL Version 3), copied verbatim in the file "COPYING". You can
 *               redistribute it and/or modify it under the terms of the GPL Version 3, or (at your
 *               option) any later version.
 *
 *               This program is distributed in the hope that it will be useful, but WITHOUT ANY
 *               WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 *               PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 *               In applying this licence, CERN does not waive the privileges and immunities
 *               granted to it by virtue of its status as an Intergovernmental Organization or
 *               submit itself to any jurisdiction.
 */

#pragma once

#include <syscall.h>

#include <fstream>
#include <future>
#include <list>
#include <map>
#include <set>
#include <string>

#include "common/dataStructures/JobQueueType.hpp"
#include "common/dataStructures/RepackQueueType.hpp"
#include "common/dataStructures/Tape.hpp"
#include "common/threading/Mutex.hpp"
#include "common/threading/MutexLocker.hpp"
#include "scheduler/OStoreDB/OStoreDB.hpp"
#include "scheduler/SchedulerDatabase.hpp"

// Activate or not helper cache update for debugging
// #define HELPERS_CACHE_UPDATE_LOGGING
#define HELPERS_CACHE_UPDATE_LOGGING_FILE "/var/tmp/cta-helpers-update-cache.log"

/**
 * A collection of helper functions for commonly used multi-object operations
 */

namespace cta {

namespace catalogue {
class Catalogue;
}

namespace objectstore {

class ScopedExclusiveLock;
class AgentReference;
class RepackQueue;

/**
 * A class with static functions allowing multi-object operations
 */
class Helpers {
 public:
  /**
   * Find or create an archive or retrieve queue, and return it locked and fetched to the caller
   * (Queue and ScopedExclusiveLock objects are provided empty)
   * @param queue the queue object, empty
   * @param queueLock the lock, not initialized
   * @param agentReference the agent reference that will be needed in case of object creation
   * @param tapePool or vid the name of the needed tape pool
   */
  template <class Queue>
  static void getLockedAndFetchedJobQueue(Queue & queue,
    ScopedExclusiveLock & queueLock, AgentReference & agentReference,
    const std::optional<std::string> & tapePoolOrVid, common::dataStructures::JobQueueType queueType, log::LogContext & lc);

  /**
   * Find or create a repack queue, and return it locked and fetched to the caller
   * (Queue and ScopedExclusiveLock objects are provided empty)
   * @param queue the queue object, empty
   * @param queueLock the lock, not initialized
   * @param agentReference the agent reference that will be needed in case of object creation
   */
  static void getLockedAndFetchedRepackQueue(RepackQueue & queue,
    ScopedExclusiveLock & queueLock, AgentReference & agentReference,
    common::dataStructures::RepackQueueType queueType, log::LogContext & lc);

  CTA_GENERATE_EXCEPTION_CLASS(NoTapeAvailableForRetrieve);
  /**
   * Find the most appropriate queue (bid) to add the retrieve request to. The potential
   * VIDs (VIDs for non-failed copies) is provided by the caller. The status of the
   * the tapes (and available queue size) are all cached to avoid
   * frequent access to the object store. The caching create a small inefficiency
   * to the algorithm, but will help performance drastically for a very similar result
   */
  static std::string selectBestRetrieveQueue(const std::set<std::string> & candidateVids,
    cta::catalogue::Catalogue & catalogue, objectstore::Backend & objectstore, bool isRepack = false);

  /**
   * Gets the retrieve queue statistics for a set of Vids (extracted from the OStoreDB
   * so it can be used in the Helper context without passing the DB object.
   */
  static std::list<SchedulerDatabase::RetrieveQueueStatistics> getRetrieveQueueStatistics(
    const cta::common::dataStructures::RetrieveFileQueueCriteria& criteria,
    const std::set<std::string> & vidsToConsider,
    objectstore::Backend & objectstore);

  /**
   * Opportunistic updating of the queue stats cache as we access it. This implies the
   * tape is not disabled (full status not fetched).
   */
  static void updateRetrieveQueueStatisticsCache(const std::string & vid, uint64_t files, uint64_t bytes, uint64_t priority);

  /**
   * Allows to flush the RetrieveQueueStatisticsCache
   * TO BE USED BY UNIT TESTS !
   */
  static void flushRetrieveQueueStatisticsCache();
  static void flushRetrieveQueueStatisticsCacheForVid(const std::string & vid);

 private:
  /** A struct holding together tape statistics and an update time */
  struct TapeStatusWithTime {
    common::dataStructures::Tape tapeStatus;
    time_t updateTime;
  };
  /** Cache for tape statistics */
  static std::map<std::string, TapeStatusWithTime> g_tapeStatuses;
  /** Lock for the retrieve queues stats */
  static cta::threading::Mutex g_retrieveQueueStatisticsMutex;
  /** A struct holding together RetrieveQueueStatistics, tape status and an update time. */
  struct RetrieveQueueStatisticsWithTime {
    cta::SchedulerDatabase::RetrieveQueueStatistics stats;
    cta::common::dataStructures::Tape tapeStatus;
    bool updating;
    /** The shared future will allow all updating safely an entry of the cache while
     * releasing the global mutex to allow threads interested in other VIDs to carry on.*/
    std::shared_future<void> updateFuture;
    time_t updateTime;
  };
  /** The stats for the queues */
  static std::map<std::string, RetrieveQueueStatisticsWithTime> g_retrieveQueueStatistics;
  /** Time between cache updates */
  static const time_t c_tapeCacheMaxAge = 600;
  static const time_t c_retrieveQueueCacheMaxAge = 10;
  static void logUpdateCacheIfNeeded(const bool entryCreation, const RetrieveQueueStatisticsWithTime& tapeStatistic,
    const std::string& message = "");

 public:
  enum class CreateIfNeeded: bool {
    create = true,
    doNotCreate = false
  };

  /**
   * Helper to register a repack request in the repack index.
   * As this structure was developed late, we potentially have to create it on the fly.
   */
  static void registerRepackRequestToIndex(const std::string & vid, const std::string & requestAddress,
      AgentReference & agentReference, Backend & backend, log::LogContext & lc);

  /**
   * Helper to remove an entry form the repack index.
   */
  static void removeRepackRequestToIndex(const std::string & vid, Backend & backend, log::LogContext & lc);
};

}  // namespace objectstore
}  // namespace cta