////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2018 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 Kaveh Vahedipour
/// @author Matthew Von-Maszewski
////////////////////////////////////////////////////////////////////////////////

#include "UpdateCollection.h"

#include "ApplicationFeatures/ApplicationServer.h"
#include "Basics/VelocyPackHelper.h"
#include "Cluster/ClusterFeature.h"
#include "Cluster/FollowerInfo.h"
#include "Cluster/MaintenanceFeature.h"
#include "Cluster/ClusterComm.h"
#include "Transaction/ClusterUtils.h"
#include "Utils/DatabaseGuard.h"
#include "VocBase/LogicalCollection.h"
#include "VocBase/Methods/Collections.h"
#include "VocBase/Methods/Databases.h"

using namespace arangodb;
using namespace arangodb::application_features;
using namespace arangodb::maintenance;
using namespace arangodb::methods;

UpdateCollection::UpdateCollection(MaintenanceFeature& feature, ActionDescription const& desc)
    : ActionBase(feature, desc) {
  std::stringstream error;

  _labels.emplace(FAST_TRACK);

  if (!desc.has(COLLECTION)) {
    error << "collection must be specified. ";
  }
  TRI_ASSERT(desc.has(COLLECTION));

  if (!desc.has(SHARD)) {
    error << "shard must be specified. ";
  }
  TRI_ASSERT(desc.has(SHARD));

  if (!desc.has(DATABASE)) {
    error << "database must be specified. ";
  }
  TRI_ASSERT(desc.has(DATABASE));

  if (!desc.has(FOLLOWERS_TO_DROP)) {
    error << "followersToDrop must be specified. ";
  }
  TRI_ASSERT(desc.has(FOLLOWERS_TO_DROP));

  if (!error.str().empty()) {
    LOG_TOPIC("a6e4c", ERR, Logger::MAINTENANCE)
        << "UpdateCollection: " << error.str();
    _result.reset(TRI_ERROR_INTERNAL, error.str());
    setState(FAILED);
  }
}

void sendLeaderChangeRequests(std::vector<ServerID> const& currentServers,
                              std::shared_ptr<std::vector<ServerID>>& realInsyncFollowers,
                              std::string const& databaseName, ShardID const& shardID,
                              std::string const& oldLeader) {

  auto cc = ClusterComm::instance();
  if (cc == nullptr) {
    // nullptr happens only during controlled shutdown
    return;
  }

  std::string const& sid = ServerState::instance()->getId();


  VPackBuilder bodyBuilder;
  {
    VPackObjectBuilder ob(&bodyBuilder);
    bodyBuilder.add("leaderId", VPackValue(sid));
    bodyBuilder.add("oldLeaderId", VPackValue(oldLeader));
    bodyBuilder.add("shard", VPackValue(shardID));
  }

  std::string const url = "/_db/" + databaseName + "/_api/replication/set-the-leader";

  std::vector<ClusterCommRequest> requests;
  auto body = std::make_shared<std::string>(bodyBuilder.toJson());
  for (auto const& srv : currentServers) {
    if (srv == sid) {
      continue; // ignore ourself
    }
    requests.emplace_back("server:" + srv, RequestType::PUT, url, body);
  }

  cc->performRequests(requests, 3.0, Logger::COMMUNICATION, false);

  // This code intentionally ignores all errors
  realInsyncFollowers = std::make_shared<std::vector<ServerID>>();
  for (auto const& req : requests) {
    ClusterCommResult const& result = req.result;
    if (result.status == CL_COMM_RECEIVED && result.errorCode == TRI_ERROR_NO_ERROR) {
      if (result.result && result.result->getHttpReturnCode() == 200) {
        realInsyncFollowers->push_back(result.serverID);
      }
    }
  }
}

void handleLeadership(LogicalCollection& collection, std::string const& localLeader,
                      std::string const& plannedLeader,
                      std::string const& followersToDrop, std::string const& databaseName,
                      uint64_t oldCounter, MaintenanceFeature& feature) {
  auto& followers = collection.followers();

  if (plannedLeader.empty()) {   // Planned to lead
    if (!localLeader.empty()) {  // We were not leader, assume leadership
      // This will block the thread until we fetched a new current version
      // in maintenance main thread.
      feature.waitForLargerCurrentCounter(oldCounter);
      auto currentInfo = ClusterInfo::instance()->getCollectionCurrent(
          databaseName, std::to_string(collection.planId()));
      if (currentInfo == nullptr) {
        // Collection has been dropped we cannot continue here.
        return;
      }
      TRI_ASSERT(currentInfo != nullptr);
      std::vector<ServerID> currentServers = currentInfo->servers(collection.name());
      std::shared_ptr<std::vector<ServerID>> realInsyncFollowers;

      if (currentServers.size() > 0) {
        std::string& oldLeader = currentServers.at(0);
        // Check if the old leader has resigned and stopped all write
        // (if so, we can assume that all servers are still in sync)
        if (oldLeader.at(0) == '_') {
          // remove the underscore from the list as it is useless anyway
          oldLeader = oldLeader.substr(1);

          // Update all follower and tell them that we are the leader now
          sendLeaderChangeRequests(currentServers, realInsyncFollowers, databaseName, collection.name(), oldLeader);
        }
      }

      std::vector<ServerID> failoverCandidates = currentInfo->failoverCandidates(collection.name());
      followers->takeOverLeadership(failoverCandidates, realInsyncFollowers);
      transaction::cluster::abortFollowerTransactionsOnShard(collection.id());
    } else {
      // If someone (the Supervision most likely) has thrown
      // out a follower from the plan, then the leader
      // will not notice until it fails to replicate an operation
      // to the old follower. This here is to drop such a follower
      // from the local list of followers. Will be reported
      // to Current in due course.
      if (!followersToDrop.empty()) {
        std::vector<std::string> ftd =
            arangodb::basics::StringUtils::split(followersToDrop, ',');
        for (auto const& s : ftd) {
          followers->remove(s);
        }
      }
    }
  } else {  // Planned to follow
    if (localLeader.empty()) {
      // Note that the following does not delete the follower list
      // and that this is crucial, because in the planned leader
      // resign case, updateCurrentForCollections will report the
      // resignation together with the old in-sync list to the
      // agency. If this list would be empty, then the supervision
      // would be very angry with us!
      followers->setTheLeader(plannedLeader);
      transaction::cluster::abortLeaderTransactionsOnShard(collection.id());
    }
    // Note that if we have been a follower to some leader
    // we do not immediately adjust the leader here, even if
    // the planned leader differs from what we have set locally.
    // The setting must only be adjusted once we have
    // synchronized with the new leader and negotiated
    // a leader/follower relationship!
  }
}

UpdateCollection::~UpdateCollection() {}

bool UpdateCollection::first() {
  auto const& database = _description.get(DATABASE);
  auto const& collection = _description.get(COLLECTION);
  auto const& shard = _description.get(SHARD);
  auto const& followersToDrop = _description.get(FOLLOWERS_TO_DROP);
  auto const& props = properties();

  try {
    DatabaseGuard guard(database);
    auto& vocbase = guard.database();
    Result found = methods::Collections::lookup(
        vocbase, shard, [&](std::shared_ptr<LogicalCollection> const& coll) -> void {
          TRI_ASSERT(coll);
          LOG_TOPIC("60543", DEBUG, Logger::MAINTENANCE)
              << "Updating local collection " + shard;

          // If someone (the Supervision most likely) has thrown
          // out a follower from the plan, then the leader
          // will not notice until it fails to replicate an operation
          // to the old follower. This here is to drop such a follower
          // from the local list of followers. Will be reported
          // to Current in due course.
          if (!followersToDrop.empty()) {
            auto& followers = coll->followers();
            std::vector<std::string> ftd =
                arangodb::basics::StringUtils::split(followersToDrop, ',');
            for (auto const& s : ftd) {
              followers->remove(s);
            }
          }
          _result = Collections::updateProperties(*coll, props, false);  // always a full-update

          if (!_result.ok()) {
            LOG_TOPIC("c3733", ERR, Logger::MAINTENANCE)
                << "failed to update properties"
                   " of collection "
                << shard << ": " << _result.errorMessage();
          }
        });

    if (found.fail()) {
      std::stringstream error;
      error << "failed to lookup local collection " << shard << "in database " + database;
      LOG_TOPIC("620fb", ERR, Logger::MAINTENANCE) << error.str();
      _result = actionError(TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND, error.str());
    }
  } catch (std::exception const& e) {
    std::stringstream error;

    error << "action " << _description << " failed with exception " << e.what();
    LOG_TOPIC("79442", WARN, Logger::MAINTENANCE)
        << "UpdateCollection: " << error.str();
    _result.reset(TRI_ERROR_INTERNAL, error.str());
  }

  if (_result.fail()) {
    _feature.storeShardError(database, collection, shard,
                             _description.get(SERVER_ID), _result);
  }

  notify();

  return false;
}