////////////////////////////////////////////////////////////////////////////////
/// 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 "RecoverState.h"
#include "Basics/FileUtils.h"
#include "Basics/conversions.h"
#include "Basics/files.h"
#include "Basics/Exceptions.h"
#include "Basics/memory-map.h"
#include "Utils/SingleCollectionTransaction.h"
#include "Utils/StandaloneTransactionContext.h"
#include "VocBase/collection.h"
#include "VocBase/VocShaper.h"
#include "Wal/LogfileManager.h"
#include "Wal/Slots.h"

#include <velocypack/Collection.h>
#include <velocypack/Parser.h>
#include <velocypack/velocypack-aliases.h>

using namespace arangodb::wal;

////////////////////////////////////////////////////////////////////////////////
/// @brief whether or not a collection is volatile
////////////////////////////////////////////////////////////////////////////////

static inline bool IsVolatile(
    TRI_transaction_collection_t const* trxCollection) {
  return trxCollection->_collection->_collection->_info.isVolatile();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief get the directory for a database
////////////////////////////////////////////////////////////////////////////////

static std::string GetDatabaseDirectory(TRI_server_t* server,
                                        TRI_voc_tick_t databaseId) {
  char* idString = TRI_StringUInt64(databaseId);
  char* dname = TRI_Concatenate2String("database-", idString);
  TRI_FreeString(TRI_CORE_MEM_ZONE, idString);
  char* filename = TRI_Concatenate2File(server->_databasePath, dname);
  TRI_FreeString(TRI_CORE_MEM_ZONE, dname);

  std::string result(filename);
  TRI_FreeString(TRI_CORE_MEM_ZONE, filename);

  return result;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief wait until a database directory disappears
////////////////////////////////////////////////////////////////////////////////

static int WaitForDeletion(TRI_server_t* server, TRI_voc_tick_t databaseId,
                           int statusCode) {
  std::string const result = GetDatabaseDirectory(server, databaseId);

  int iterations = 0;
  // wait for at most 30 seconds for the directory to be removed
  while (TRI_IsDirectory(result.c_str())) {
    if (iterations == 0) {
      LOG(TRACE) << "waiting for deletion of database directory '" << result << "', called with status code " << statusCode;

      if (statusCode != TRI_ERROR_FORBIDDEN &&
          (statusCode == TRI_ERROR_ARANGO_DATABASE_NOT_FOUND ||
           statusCode != TRI_ERROR_NO_ERROR)) {
        LOG(WARN) << "forcefully deleting database directory '" << result << "'";
        TRI_RemoveDirectory(result.c_str());
      }
    } else if (iterations >= 30 * 10) {
      LOG(WARN) << "unable to remove database directory '" << result << "'";
      return TRI_ERROR_INTERNAL;
    }

    if (iterations == 5 * 10) {
      LOG(INFO) << "waiting for deletion of database directory '" << result << "'";
    }

    ++iterations;
    usleep(100000);
  }

  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief creates the recover state
////////////////////////////////////////////////////////////////////////////////

RecoverState::RecoverState(TRI_server_t* server, bool ignoreRecoveryErrors)
    : server(server),
      failedTransactions(),
      lastTick(0),
      logfilesToProcess(),
      openedCollections(),
      openedDatabases(),
      emptyLogfiles(),
      policy(TRI_DOC_UPDATE_ONLY_IF_NEWER, 0, nullptr),
      ignoreRecoveryErrors(ignoreRecoveryErrors),
      errorCount(0) {}

////////////////////////////////////////////////////////////////////////////////
/// @brief destroys the recover state
////////////////////////////////////////////////////////////////////////////////

RecoverState::~RecoverState() { releaseResources(); }

////////////////////////////////////////////////////////////////////////////////
/// @brief release opened collections and databases so they can be shut down
/// etc.
////////////////////////////////////////////////////////////////////////////////

void RecoverState::releaseResources() {
  // release all collections
  for (auto it = openedCollections.begin(); it != openedCollections.end();
       ++it) {
    TRI_vocbase_col_t* collection = (*it).second;
    TRI_ReleaseCollectionVocBase(collection->_vocbase, collection);
  }

  openedCollections.clear();

  // release all databases
  for (auto it = openedDatabases.begin(); it != openedDatabases.end(); ++it) {
    TRI_vocbase_t* vocbase = (*it).second;
    TRI_ReleaseDatabaseServer(server, vocbase);
  }

  openedDatabases.clear();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief gets a database (and inserts it into the cache if not in it)
////////////////////////////////////////////////////////////////////////////////

TRI_vocbase_t* RecoverState::useDatabase(TRI_voc_tick_t databaseId) {
  auto it = openedDatabases.find(databaseId);

  if (it != openedDatabases.end()) {
    return (*it).second;
  }

  TRI_vocbase_t* vocbase = TRI_UseDatabaseByIdServer(server, databaseId);

  if (vocbase == nullptr) {
    return nullptr;
  }

  openedDatabases.emplace(databaseId, vocbase);
  return vocbase;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief release a database (so it can be dropped)
////////////////////////////////////////////////////////////////////////////////

TRI_vocbase_t* RecoverState::releaseDatabase(TRI_voc_tick_t databaseId) {
  auto it = openedDatabases.find(databaseId);

  if (it == openedDatabases.end()) {
    return nullptr;
  }

  TRI_vocbase_t* vocbase = (*it).second;

  TRI_ASSERT(vocbase != nullptr);

  // release all collections we ourselves have opened for this database
  auto it2 = openedCollections.begin();

  while (it2 != openedCollections.end()) {
    TRI_vocbase_col_t* collection = (*it2).second;

    TRI_ASSERT(collection != nullptr);

    if (collection->_vocbase->_id == databaseId) {
      // correct database, now release the collection
      TRI_ASSERT(vocbase == collection->_vocbase);

      TRI_ReleaseCollectionVocBase(vocbase, collection);
      // get new iterator position
      it2 = openedCollections.erase(it2);
    } else {
      // collection not found, advance in the loop
      ++it2;
    }
  }

  TRI_ReleaseDatabaseServer(server, vocbase);
  openedDatabases.erase(databaseId);

  return vocbase;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief release a collection (so it can be dropped)
////////////////////////////////////////////////////////////////////////////////

TRI_vocbase_col_t* RecoverState::releaseCollection(TRI_voc_cid_t collectionId) {
  auto it = openedCollections.find(collectionId);

  if (it == openedCollections.end()) {
    return nullptr;
  }

  TRI_vocbase_col_t* collection = (*it).second;

  TRI_ASSERT(collection != nullptr);
  TRI_ReleaseCollectionVocBase(collection->_vocbase, collection);
  openedCollections.erase(collectionId);

  return collection;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief gets a collection (and inserts it into the cache if not in it)
////////////////////////////////////////////////////////////////////////////////

TRI_vocbase_col_t* RecoverState::useCollection(TRI_vocbase_t* vocbase,
                                               TRI_voc_cid_t collectionId,
                                               int& res) {
  auto it = openedCollections.find(collectionId);

  if (it != openedCollections.end()) {
    res = TRI_ERROR_NO_ERROR;
    return (*it).second;
  }

  TRI_set_errno(TRI_ERROR_NO_ERROR);
  TRI_vocbase_col_status_e status;  // ignored here
  TRI_vocbase_col_t* collection =
      TRI_UseCollectionByIdVocBase(vocbase, collectionId, status);

  if (collection == nullptr) {
    res = TRI_errno();

    if (res == TRI_ERROR_ARANGO_CORRUPTED_COLLECTION) {
      LOG(WARN) << "unable to open collection " << collectionId << ". Please check the logs above for errors.";
    }

    return nullptr;
  }

  TRI_document_collection_t* document = collection->_collection;
  TRI_ASSERT(document != nullptr);

  // disable secondary indexes for the moment
  document->useSecondaryIndexes(false);

  openedCollections.emplace(collectionId, collection);
  res = TRI_ERROR_NO_ERROR;
  return collection;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief looks up a collection
/// the collection will be opened after this call and inserted into a local
/// cache for faster lookups
/// returns nullptr if the collection does not exist
////////////////////////////////////////////////////////////////////////////////

TRI_document_collection_t* RecoverState::getCollection(
    TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId) {
  TRI_vocbase_t* vocbase = useDatabase(databaseId);

  if (vocbase == nullptr) {
    LOG(TRACE) << "database " << databaseId << " not found";
    return nullptr;
  }

  int res;
  TRI_vocbase_col_t* collection = useCollection(vocbase, collectionId, res);

  if (collection == nullptr) {
    LOG(TRACE) << "collection " << collectionId << " of database " << databaseId << " not found";
    return nullptr;
  }

  TRI_document_collection_t* document = collection->_collection;
  TRI_ASSERT(document != nullptr);

  return document;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief executes a single operation inside a transaction
////////////////////////////////////////////////////////////////////////////////

int RecoverState::executeSingleOperation(
    TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId,
    TRI_df_marker_t const* marker, TRI_voc_fid_t fid,
    std::function<int(SingleCollectionTransaction*, Marker*)> func) {
  // first find the correct database
  TRI_vocbase_t* vocbase = useDatabase(databaseId);

  if (vocbase == nullptr) {
    LOG(TRACE) << "database " << databaseId << " not found";
    return TRI_ERROR_ARANGO_DATABASE_NOT_FOUND;
  }

  int res;
  TRI_vocbase_col_t* collection = useCollection(vocbase, collectionId, res);

  if (collection == nullptr || collection->_collection == nullptr) {
    if (res == TRI_ERROR_ARANGO_CORRUPTED_COLLECTION) {
      return res;
    }

    return TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND;
  }

  TRI_voc_tick_t tickMax = collection->_collection->_tickMax;
  if (marker->_tick <= tickMax) {
    // already transferred this marker
    return TRI_ERROR_NO_ERROR;
  }

  SingleCollectionTransaction* trx = nullptr;
  EnvelopeMarker* envelope = nullptr;
  res = TRI_ERROR_INTERNAL;

  try {
    trx = new SingleCollectionTransaction(arangodb::StandaloneTransactionContext::Create(vocbase), collectionId, TRI_TRANSACTION_WRITE);

    if (trx == nullptr) {
      THROW_ARANGO_EXCEPTION(res);
    }

    trx->addHint(TRI_TRANSACTION_HINT_NO_BEGIN_MARKER, false);
    trx->addHint(TRI_TRANSACTION_HINT_NO_ABORT_MARKER, false);
    trx->addHint(TRI_TRANSACTION_HINT_NO_THROTTLING, false);
    trx->addHint(TRI_TRANSACTION_HINT_LOCK_NEVER, false);

    res = trx->begin();

    if (res != TRI_ERROR_NO_ERROR) {
      THROW_ARANGO_EXCEPTION(res);
    }

    envelope = new EnvelopeMarker(marker, fid);

    // execute the operation
    res = func(trx, envelope);

    if (res != TRI_ERROR_NO_ERROR) {
      THROW_ARANGO_EXCEPTION(res);
    }

    // commit the operation
    res = trx->commit();
  } catch (arangodb::basics::Exception const& ex) {
    res = ex.code();
  } catch (...) {
    res = TRI_ERROR_INTERNAL;
  }

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

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

  return res;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief callback to handle one marker during recovery
/// this function only builds up state and does not change any data
////////////////////////////////////////////////////////////////////////////////

bool RecoverState::InitialScanMarker(TRI_df_marker_t const* marker, void* data,
                                     TRI_datafile_t* datafile) {
  RecoverState* state = reinterpret_cast<RecoverState*>(data);

  TRI_ASSERT(marker != nullptr);

  // note the marker's tick
  TRI_ASSERT(marker->_tick >= state->lastTick);

  if (marker->_tick > state->lastTick) {
    state->lastTick = marker->_tick;
  }

  switch (marker->_type) {
    // -----------------------------------------------------------------------------
    // transactions
    // -----------------------------------------------------------------------------

    case TRI_WAL_MARKER_BEGIN_TRANSACTION: {
      transaction_begin_marker_t const* m =
          reinterpret_cast<transaction_begin_marker_t const*>(marker);
      // insert this transaction into the list of failed transactions
      // we do this because if we don't find a commit marker for this
      // transaction,
      // we'll have it in the failed list at the end of the scan and can ignore
      // it
      state->failedTransactions.emplace(m->_transactionId,
                                        std::make_pair(m->_databaseId, false));
      break;
    }

    case TRI_WAL_MARKER_COMMIT_TRANSACTION: {
      transaction_commit_marker_t const* m =
          reinterpret_cast<transaction_commit_marker_t const*>(marker);
      // remove this transaction from the list of failed transactions
      state->failedTransactions.erase(m->_transactionId);
      break;
    }

    case TRI_WAL_MARKER_ABORT_TRANSACTION: {
      // insert this transaction into the list of failed transactions
      transaction_abort_marker_t const* m =
          reinterpret_cast<transaction_abort_marker_t const*>(marker);

      auto it = state->failedTransactions.find(m->_transactionId);

      if (it != state->failedTransactions.end()) {
        // delete previous element if present
        state->failedTransactions.erase(m->_transactionId);
      }

      // and (re-)insert
      state->failedTransactions.emplace(m->_transactionId,
                                        std::make_pair(m->_databaseId, true));
      break;
    }

    case TRI_WAL_MARKER_BEGIN_REMOTE_TRANSACTION: {
      transaction_remote_begin_marker_t const* m =
          reinterpret_cast<transaction_remote_begin_marker_t const*>(marker);
      // insert this transaction into the list of failed transactions
      state->failedTransactions.emplace(m->_transactionId,
                                        std::make_pair(m->_databaseId, false));
      break;
    }

    case TRI_WAL_MARKER_COMMIT_REMOTE_TRANSACTION: {
      transaction_remote_commit_marker_t const* m =
          reinterpret_cast<transaction_remote_commit_marker_t const*>(marker);
      // remove this transaction from the list of failed transactions
      state->failedTransactions.erase(m->_transactionId);
      break;
    }

    case TRI_WAL_MARKER_ABORT_REMOTE_TRANSACTION: {
      transaction_remote_abort_marker_t const* m =
          reinterpret_cast<transaction_remote_abort_marker_t const*>(marker);
      // insert this transaction into the list of failed transactions
      // the transaction is treated the same as a regular local transaction that
      // is aborted
      auto it = state->failedTransactions.find(m->_transactionId);

      if (it != state->failedTransactions.end()) {
        state->failedTransactions.erase(m->_transactionId);
      }

      // and (re-)insert
      state->failedTransactions.emplace(m->_transactionId,
                                        std::make_pair(m->_databaseId, true));
      break;
    }
    /*
        //
       -----------------------------------------------------------------------------
        // create markers
        //
       -----------------------------------------------------------------------------

        case TRI_WAL_MARKER_CREATE_COLLECTION: {
          collection_create_marker_t const* m =
       reinterpret_cast<collection_create_marker_t const*>(marker);
          // undo a potential drop marker discovered before for the same
       collection
          state->droppedCollections.erase(m->_collectionId);
          break;
        }

        case TRI_WAL_MARKER_CREATE_DATABASE: {
          database_create_marker_t const* m =
       reinterpret_cast<database_create_marker_t const*>(marker);
          // undo a potential drop marker discovered before for the same
       database
          state->droppedDatabases.erase(m->_databaseId);
          break;
        }

        case TRI_WAL_MARKER_CREATE_INDEX: {
          // ignored
          break;
        }

        //
       -----------------------------------------------------------------------------
        // drop markers
        //
       -----------------------------------------------------------------------------
    */

    case TRI_WAL_MARKER_DROP_COLLECTION: {
      collection_drop_marker_t const* m =
          reinterpret_cast<collection_drop_marker_t const*>(marker);
      // note that the collection was dropped and doesn't need to be recovered
      state->droppedIds.insert(m->_collectionId);
      break;
    }

      /*
          case TRI_WAL_MARKER_DROP_DATABASE: {
            database_drop_marker_t const* m =
         reinterpret_cast<database_drop_marker_t const*>(marker);
            // note that the database was dropped and doesn't need to be
         recovered
            state->droppedDatabases.insert(m->_databaseId);
            break;
          }

          case TRI_WAL_MARKER_DROP_INDEX: {
            // ignored
            break;
          }
         */
  }

  return true;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief callback to replay one marker during recovery
/// this function modifies indexes etc.
////////////////////////////////////////////////////////////////////////////////

bool RecoverState::ReplayMarker(TRI_df_marker_t const* marker, void* data,
                                TRI_datafile_t* datafile) {
  RecoverState* state = reinterpret_cast<RecoverState*>(data);

#ifdef ARANGODB_ENABLE_FAILURE_TESTS
  LOG(TRACE) << "replaying marker of type " << TRI_NameMarkerDatafile(marker);
#endif

  switch (marker->_type) {
    // -----------------------------------------------------------------------------
    // attributes and shapes
    // -----------------------------------------------------------------------------

    case TRI_WAL_MARKER_ATTRIBUTE: {
      // re-insert the attribute into the shaper
      attribute_marker_t const* m =
          reinterpret_cast<attribute_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      if (state->isDropped(databaseId, collectionId)) {
        return true;
      }

      int res = state->executeSingleOperation(
          databaseId, collectionId, marker, datafile->_fid,
          [&](SingleCollectionTransaction* trx, Marker* envelope) -> int {
            TRI_document_collection_t* document = trx->documentCollection();

            // re-insert the attribute
            int res = document->getShaper()->insertAttribute(marker, false);
            return res;
          });

      if (res != TRI_ERROR_NO_ERROR &&
          res != TRI_ERROR_ARANGO_DATABASE_NOT_FOUND &&
          res != TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND) {
        LOG(WARN) << "could not apply attribute marker: " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }
      break;
    }

    case TRI_WAL_MARKER_SHAPE: {
      // re-insert the shape into the shaper
      shape_marker_t const* m = reinterpret_cast<shape_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      if (state->isDropped(databaseId, collectionId)) {
        return true;
      }

      int res = state->executeSingleOperation(
          databaseId, collectionId, marker, datafile->_fid,
          [&](SingleCollectionTransaction* trx, Marker* envelope) -> int {
            TRI_document_collection_t* document = trx->documentCollection();

            // re-insert the shape
            int res = document->getShaper()->insertShape(marker, false);
            return res;
          });

      if (res != TRI_ERROR_NO_ERROR &&
          res != TRI_ERROR_ARANGO_DATABASE_NOT_FOUND &&
          res != TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND) {
        LOG(WARN) << "could not apply shape marker: " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }
      break;
    }

    // -----------------------------------------------------------------------------
    // crud operations
    // -----------------------------------------------------------------------------

    case TRI_WAL_MARKER_DOCUMENT: {
      // re-insert the document into the collection
      document_marker_t const* m =
          reinterpret_cast<document_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      if (state->isDropped(databaseId, collectionId)) {
        return true;
      }

      TRI_voc_tick_t transactionId = m->_transactionId;
      if (state->ignoreTransaction(transactionId)) {
        // transaction was aborted
        return true;
      }

      char const* base = reinterpret_cast<char const*>(m);
      char const* key = base + m->_offsetKey;
      TRI_shaped_json_t shaped;
      TRI_EXTRACT_SHAPED_JSON_MARKER(shaped, m);

      int res = state->executeSingleOperation(
          databaseId, collectionId, marker, datafile->_fid,
          [&](SingleCollectionTransaction* trx, Marker* envelope) -> int {
            if (IsVolatile(trx->trxCollection())) {
              return TRI_ERROR_NO_ERROR;
            }

            TRI_doc_mptr_copy_t mptr;
            int res = TRI_InsertShapedJsonDocumentCollection(
                trx, trx->trxCollection(), (TRI_voc_key_t)key, m->_revisionId,
                envelope, &mptr, &shaped, nullptr, false, false, true);

            if (res == TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED) {
              state->policy.setExpectedRevision(m->_revisionId);
              res = TRI_UpdateShapedJsonDocumentCollection(
                  trx, trx->trxCollection(), (TRI_voc_key_t)key, m->_revisionId,
                  envelope, &mptr, &shaped, &state->policy, false, false);
            }

            return res;
          });

      if (res != TRI_ERROR_NO_ERROR && res != TRI_ERROR_ARANGO_CONFLICT &&
          res != TRI_ERROR_ARANGO_DATABASE_NOT_FOUND &&
          res != TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND) {
        LOG(WARN) << "unable to insert document in collection " << collectionId << " of database " << databaseId << ": " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }
      break;
    }

    case TRI_WAL_MARKER_EDGE: {
      // re-insert the edge into the collection
      edge_marker_t const* m = reinterpret_cast<edge_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      if (state->isDropped(databaseId, collectionId)) {
        return true;
      }

      TRI_voc_tick_t transactionId = m->_transactionId;
      if (state->ignoreTransaction(transactionId)) {
        return true;
      }

      char const* base = reinterpret_cast<char const*>(m);
      char const* key = base + m->_offsetKey;
      TRI_document_edge_t edge;
      edge._fromCid = m->_fromCid;
      edge._toCid = m->_toCid;
      edge._fromKey = const_cast<char*>(base) + m->_offsetFromKey;
      edge._toKey = const_cast<char*>(base) + m->_offsetToKey;

      TRI_shaped_json_t shaped;
      TRI_EXTRACT_SHAPED_JSON_MARKER(shaped, m);

      int res = state->executeSingleOperation(
          databaseId, collectionId, marker, datafile->_fid,
          [&](SingleCollectionTransaction* trx, Marker* envelope) -> int {
            if (IsVolatile(trx->trxCollection())) {
              return TRI_ERROR_NO_ERROR;
            }

            TRI_doc_mptr_copy_t mptr;
            int res = TRI_InsertShapedJsonDocumentCollection(
                trx, trx->trxCollection(), (TRI_voc_key_t)key, m->_revisionId,
                envelope, &mptr, &shaped, &edge, false, false, true);

            if (res == TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED) {
              state->policy.setExpectedRevision(m->_revisionId);
              res = TRI_UpdateShapedJsonDocumentCollection(
                  trx, trx->trxCollection(), (TRI_voc_key_t)key, m->_revisionId,
                  envelope, &mptr, &shaped, &state->policy, false, false);
            }

            return res;
          });

      if (res != TRI_ERROR_NO_ERROR && res != TRI_ERROR_ARANGO_CONFLICT &&
          res != TRI_ERROR_ARANGO_DATABASE_NOT_FOUND &&
          res != TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND) {
        LOG(WARN) << "unable to insert edge in collection " << collectionId << " of database " << databaseId << ": " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }

      break;
    }

    case TRI_WAL_MARKER_REMOVE: {
      // re-apply the remove operation
      remove_marker_t const* m =
          reinterpret_cast<remove_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      if (state->isDropped(databaseId, collectionId)) {
        return true;
      }

      TRI_voc_tick_t transactionId = m->_transactionId;
      if (state->ignoreTransaction(transactionId)) {
        return true;
      }

      char const* base = reinterpret_cast<char const*>(m);
      char const* key = base + sizeof(remove_marker_t);
      int res = state->executeSingleOperation(
          databaseId, collectionId, marker, datafile->_fid,
          [&](SingleCollectionTransaction* trx, Marker* envelope) -> int {
            if (IsVolatile(trx->trxCollection())) {
              return TRI_ERROR_NO_ERROR;
            }

            // remove the document and ignore any potential errors
            state->policy.setExpectedRevision(m->_revisionId);
            TRI_RemoveShapedJsonDocumentCollection(
                trx, trx->trxCollection(), (TRI_voc_key_t)key, m->_revisionId,
                envelope, &state->policy, false, false);

            return TRI_ERROR_NO_ERROR;
          });

      if (res != TRI_ERROR_NO_ERROR && res != TRI_ERROR_ARANGO_CONFLICT &&
          res != TRI_ERROR_ARANGO_DATABASE_NOT_FOUND &&
          res != TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND) {
        LOG(WARN) << "unable to remove document in collection " << collectionId << " of database " << databaseId << ": " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }
      break;
    }

    // -----------------------------------------------------------------------------
    // transactions
    // -----------------------------------------------------------------------------

    case TRI_WAL_MARKER_RENAME_COLLECTION: {
      collection_rename_marker_t const* m =
          reinterpret_cast<collection_rename_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      if (state->isDropped(databaseId)) {
        return true;
      }

      TRI_vocbase_t* vocbase = state->useDatabase(databaseId);

      if (vocbase == nullptr) {
        // if the underlying database is gone, we can go on
        LOG(TRACE) << "cannot open database " << databaseId;
        return true;
      }

      TRI_vocbase_col_t* collection = state->releaseCollection(collectionId);

      if (collection == nullptr) {
        collection = TRI_LookupCollectionByIdVocBase(vocbase, collectionId);
      }

      if (collection == nullptr) {
        // if the underlying collection is gone, we can go on
        LOG(TRACE) << "cannot open collection " << collectionId;
        return true;
      }

      char const* name =
          reinterpret_cast<char const*>(m) + sizeof(collection_rename_marker_t);

      // check if other collection exist with target name
      TRI_vocbase_col_t* other =
          TRI_LookupCollectionByNameVocBase(vocbase, name);

      if (other != nullptr) {
        TRI_voc_cid_t otherCid = other->_cid;
        state->releaseCollection(otherCid);
        TRI_DropCollectionVocBase(vocbase, other, false);
      }


      int res =
          TRI_RenameCollectionVocBase(vocbase, collection, name, true, false);

      if (res != TRI_ERROR_NO_ERROR) {
        LOG(WARN) << "cannot rename collection collection " << collectionId << " in database " << databaseId << ": " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }
      break;
    }

    case TRI_WAL_MARKER_CHANGE_COLLECTION: {
      collection_change_marker_t const* m =
          reinterpret_cast<collection_change_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      if (state->isDropped(databaseId)) {
        return true;
      }

      TRI_vocbase_t* vocbase = state->useDatabase(databaseId);

      if (vocbase == nullptr) {
        // if the underlying database is gone, we can go on
        LOG(TRACE) << "cannot open database " << databaseId;
        return true;
      }

      TRI_document_collection_t* document =
          state->getCollection(databaseId, collectionId);

      if (document == nullptr) {
        // if the underlying collection is gone, we can go on
        LOG(TRACE) << "cannot change properties of collection " << collectionId << " in database " << databaseId << ": " << TRI_errno_string(TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND);
        return true;
      }

      char const* properties =
          reinterpret_cast<char const*>(m) + sizeof(collection_change_marker_t);
      std::shared_ptr<VPackBuilder> parsedProperties;
      try {
        parsedProperties = VPackParser::fromJson(properties);
      } catch (...) {
        LOG(WARN) << "cannot unpack collection properties for collection " << collectionId << " in database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }

      VPackSlice const slice = parsedProperties->slice();

      int res = TRI_UpdateCollectionInfo(
          vocbase, document, slice, vocbase->_settings.forceSyncProperties);

      if (res != TRI_ERROR_NO_ERROR) {
        LOG(WARN) << "cannot change collection properties for collection " << collectionId << " in database " << databaseId << ": " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }

      break;
    }

    // -----------------------------------------------------------------------------
    // create operations
    // -----------------------------------------------------------------------------

    case TRI_WAL_MARKER_CREATE_INDEX: {
      index_create_marker_t const* m =
          reinterpret_cast<index_create_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;
      TRI_idx_iid_t indexId = m->_indexId;

      if (state->isDropped(databaseId, collectionId)) {
        return true;
      }

      TRI_vocbase_t* vocbase = state->useDatabase(databaseId);

      if (vocbase == nullptr) {
        // if the underlying database is gone, we can go on
        LOG(TRACE) << "cannot create index for collection " << collectionId << " in database " << databaseId << ": " << TRI_errno_string(TRI_ERROR_ARANGO_DATABASE_NOT_FOUND);
        return true;
      }

      TRI_document_collection_t* document =
          state->getCollection(databaseId, collectionId);

      if (document == nullptr) {
        // if the underlying collection is gone, we can go on
        LOG(TRACE) << "cannot create index for collection " << collectionId << " in database " << databaseId << ": " << TRI_errno_string(TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND);
        return true;
      }
      
      TRI_vocbase_col_t* col = TRI_LookupCollectionByIdVocBase(vocbase, collectionId);

      if (col == nullptr) {
        // if the underlying collection gone, we can go on
        LOG(TRACE) << "cannot create index for collection " << collectionId << " in database " << databaseId << ": " << TRI_errno_string(TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND);
        return true;
      }

      char const* properties =
          reinterpret_cast<char const*>(m) + sizeof(index_create_marker_t);
      std::shared_ptr<VPackBuilder> builder;
      try {
        builder = VPackParser::fromJson(properties);
      } catch (...) {
        LOG(WARN) << "cannot unpack index properties for index " << indexId << ", collection " << collectionId << " in database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }
      VPackSlice slice = builder->slice();
      if (!slice.isObject()) {
        LOG(WARN) << "cannot unpack index properties for index " << indexId << ", collection " << collectionId << " in database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }

      std::string const indexName("index-" + std::to_string(indexId) + ".json");
      std::string const filename(arangodb::basics::FileUtils::buildFilename(col->path(), indexName));

      bool ok = arangodb::basics::VelocyPackHelper::velocyPackToFile(
          filename.c_str(), slice, vocbase->_settings.forceSyncProperties);

      if (!ok) {
        LOG(WARN) << "cannot create index " << indexId << ", collection " << collectionId << " in database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      } else {
        char* p = TRI_DuplicateString(TRI_CORE_MEM_ZONE, filename.c_str(), filename.size());
        TRI_PushBackVectorString(&document->_indexFiles, p);
      }

      break;
    }

    case TRI_WAL_MARKER_CREATE_COLLECTION: {
      collection_create_marker_t const* m =
          reinterpret_cast<collection_create_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      // remove the drop marker
      state->droppedCollections.erase(collectionId);

      if (state->isDropped(databaseId)) {
        return true;
      }

      TRI_vocbase_t* vocbase = state->useDatabase(databaseId);

      if (vocbase == nullptr) {
        // if the underlying database is gone, we can go on
        LOG(TRACE) << "cannot open database " << databaseId;
        return true;
      }

      TRI_vocbase_col_t* collection = state->releaseCollection(collectionId);

      if (collection == nullptr) {
        collection = TRI_LookupCollectionByIdVocBase(vocbase, collectionId);
      }
      
      if (collection != nullptr) {
        // drop an existing collection
        TRI_DropCollectionVocBase(vocbase, collection, false);
      }

      char const* properties =
          reinterpret_cast<char const*>(m) + sizeof(collection_create_marker_t);
      std::shared_ptr<VPackBuilder> builder;
      try {
        builder = VPackParser::fromJson(properties);
      } catch (...) {
        LOG(WARN) << "cannot unpack collection properties for collection " << collectionId << " in database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }
      VPackSlice slice = builder->slice();
      if (!slice.isObject()) {
        LOG(WARN) << "cannot unpack collection properties for collection " << collectionId << " in database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }

      // check if there is another collection with the same name as the one that
      // we attempt to create
      VPackSlice const nameSlice = slice.get("name");
      std::string name = "";

      if (nameSlice.isString()) {
        name = nameSlice.copyString();
        collection = TRI_LookupCollectionByNameVocBase(vocbase, name.c_str());

        if (collection != nullptr) {  // && !
          // TRI_IsSystemNameCollection(name->_value._string.data))
          // {
          // if yes, delete it
          TRI_voc_cid_t otherCid = collection->_cid;

          state->releaseCollection(otherCid);
          TRI_DropCollectionVocBase(vocbase, collection, false);
        }
      } else {
        LOG(WARN) << "empty name attribute in create collection marker for collection " << collectionId << " and database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }

      // fiddle "isSystem" value, which is not contained in the JSON file
      bool isSystemValue = false;
      if (!name.empty()) {
        isSystemValue = name[0] == '_';
      }

      VPackBuilder bx;
      bx.openObject();
      bx.add("isSystem", VPackValue(isSystemValue));
      bx.close();
      VPackSlice isSystem = bx.slice();
      VPackBuilder b2 = VPackCollection::merge(slice, isSystem, false);
      slice = b2.slice();

      arangodb::VocbaseCollectionInfo info(vocbase, name.c_str(), slice);

      if (state->willBeDropped(collectionId)) {
        // in case we detect that this collection is going to be deleted anyway,
        // set
        // the sync properties to false temporarily
        bool oldSync = vocbase->_settings.forceSyncProperties;
        vocbase->_settings.forceSyncProperties = false;
        collection =
            TRI_CreateCollectionVocBase(vocbase, info, collectionId, false);
        vocbase->_settings.forceSyncProperties = oldSync;

      } else {
        // collection will be kept
        collection =
            TRI_CreateCollectionVocBase(vocbase, info, collectionId, false);
      }

      if (collection == nullptr) {
        LOG(WARN) << "cannot create collection " << collectionId << " in database " << databaseId << ": " << TRI_last_error();
        ++state->errorCount;
        return state->canContinue();
      }
      break;
    }

    case TRI_WAL_MARKER_CREATE_DATABASE: {
      database_create_marker_t const* m =
          reinterpret_cast<database_create_marker_t const*>(marker);
      TRI_voc_tick_t databaseId = m->_databaseId;

      // remove the drop marker
      state->droppedDatabases.erase(databaseId);
      TRI_vocbase_t* vocbase = state->releaseDatabase(databaseId);

      if (vocbase != nullptr) {
        // remove already existing database
        int statusCode =
            TRI_DropByIdDatabaseServer(state->server, databaseId, false, false);
        WaitForDeletion(state->server, databaseId, statusCode);
      }

      char const* properties =
          reinterpret_cast<char const*>(m) + sizeof(database_create_marker_t);
      std::shared_ptr<VPackBuilder> parsedProperties;
      try {
        parsedProperties = VPackParser::fromJson(properties);
      } catch (...) {
        LOG(WARN) << "cannot unpack database properties for database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }
      VPackSlice const slice = parsedProperties->slice();

      if (!slice.isObject()) {
        LOG(WARN) << "cannot unpack database properties for database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }

      VPackSlice const nameSlice = slice.get("name");

      if (!nameSlice.isString()) {
        LOG(WARN) << "cannot unpack database properties for database " << databaseId;
        ++state->errorCount;
        return state->canContinue();
      }

      std::string nameString = nameSlice.copyString();

      // remove already existing database with same name
      vocbase =
          TRI_LookupDatabaseByNameServer(state->server, nameString.c_str());

      if (vocbase != nullptr) {
        TRI_voc_tick_t otherId = vocbase->_id;

        state->releaseDatabase(otherId);
        int statusCode = TRI_DropDatabaseServer(
            state->server, nameString.c_str(), false, false);
        WaitForDeletion(state->server, otherId, statusCode);
      }

      TRI_vocbase_defaults_t defaults;
      TRI_GetDatabaseDefaultsServer(state->server, &defaults);

      vocbase = nullptr;
      WaitForDeletion(state->server, databaseId,
                      TRI_ERROR_ARANGO_DATABASE_NOT_FOUND);
      int res = TRI_CreateDatabaseServer(state->server, databaseId,
                                         nameString.c_str(), &defaults,
                                         &vocbase, false);

      if (res != TRI_ERROR_NO_ERROR) {
        LOG(WARN) << "cannot create database " << databaseId << ": " << TRI_errno_string(res);
        ++state->errorCount;
        return state->canContinue();
      }
      break;
    }

    // -----------------------------------------------------------------------------
    // drop operations
    // -----------------------------------------------------------------------------

    case TRI_WAL_MARKER_DROP_INDEX: {
      index_drop_marker_t const* m =
          reinterpret_cast<index_drop_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;
      TRI_idx_iid_t indexId = m->_indexId;

      if (state->isDropped(databaseId, collectionId)) {
        return true;
      }

      TRI_vocbase_t* vocbase = state->useDatabase(databaseId);

      if (vocbase == nullptr) {
        // if the underlying database is gone, we can go on
        LOG(TRACE) << "cannot open database " << databaseId;
        return true;
      }

      TRI_document_collection_t* document =
          state->getCollection(databaseId, collectionId);
      if (document == nullptr) {
        // if the underlying collection gone, we can go on
        return true;
      }

      TRI_vocbase_col_t* col = TRI_LookupCollectionByIdVocBase(vocbase, collectionId);

      if (col == nullptr) {
        // if the underlying collection gone, we can go on
        return true;
      }

      // ignore any potential error returned by this call
      TRI_DropIndexDocumentCollection(document, indexId, false);
      TRI_RemoveFileIndexCollection(document, indexId);

      // additionally remove the index file
      std::string const indexName("index-" + std::to_string(indexId) + ".json");
      std::string const filename(arangodb::basics::FileUtils::buildFilename(col->path(), indexName));

      TRI_UnlinkFile(filename.c_str());
      break;
    }

    case TRI_WAL_MARKER_DROP_COLLECTION: {
      collection_drop_marker_t const* m =
          reinterpret_cast<collection_drop_marker_t const*>(marker);
      TRI_voc_cid_t collectionId = m->_collectionId;
      TRI_voc_tick_t databaseId = m->_databaseId;

      // insert the drop marker
      state->droppedCollections.insert(collectionId);

      TRI_vocbase_t* vocbase = state->useDatabase(databaseId);

      if (vocbase == nullptr) {
        // database already deleted - do nothing
        return true;
      }

      // ignore any potential error returned by this call
      TRI_vocbase_col_t* collection = state->releaseCollection(collectionId);

      if (collection == nullptr) {
        collection = TRI_LookupCollectionByIdVocBase(vocbase, collectionId);
      }

      if (collection != nullptr) {
        TRI_DropCollectionVocBase(vocbase, collection, false);
      }
      break;
    }

    case TRI_WAL_MARKER_DROP_DATABASE: {
      database_drop_marker_t const* m =
          reinterpret_cast<database_drop_marker_t const*>(marker);
      TRI_voc_tick_t databaseId = m->_databaseId;

      // insert the drop marker
      state->droppedDatabases.insert(databaseId);
      TRI_vocbase_t* vocbase = state->releaseDatabase(databaseId);

      if (vocbase != nullptr) {
        // ignore any potential error returned by this call
        TRI_DropByIdDatabaseServer(state->server, databaseId, false, false);
      }
      break;
    }
  }

  return true;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief replay a single logfile
////////////////////////////////////////////////////////////////////////////////

int RecoverState::replayLogfile(Logfile* logfile, int number) {
  std::string const logfileName = logfile->filename();

  int const n = static_cast<int>(logfilesToProcess.size());

  LOG(INFO) << "replaying WAL logfile '" << logfileName << "' (" << number + 1 << " of " << n << ")";

  // Advise on sequential use:
  TRI_MMFileAdvise(logfile->df()->_data, logfile->df()->_maximalSize,
                   TRI_MADVISE_SEQUENTIAL);
  TRI_MMFileAdvise(logfile->df()->_data, logfile->df()->_maximalSize,
                   TRI_MADVISE_WILLNEED);

  if (!TRI_IterateDatafile(logfile->df(), &RecoverState::ReplayMarker,
                           static_cast<void*>(this))) {
    LOG(WARN) << "WAL inspection failed when scanning logfile '" << logfileName << "'";
    return TRI_ERROR_ARANGO_RECOVERY;
  }

  // Advise on random access use:
  TRI_MMFileAdvise(logfile->df()->_data, logfile->df()->_maximalSize,
                   TRI_MADVISE_RANDOM);

  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief replay all logfiles
////////////////////////////////////////////////////////////////////////////////

int RecoverState::replayLogfiles() {
  droppedCollections.clear();
  droppedDatabases.clear();

  int i = 0;
  for (auto& it : logfilesToProcess) {
    TRI_ASSERT(it != nullptr);
    int res = replayLogfile(it, i++);

    if (res != TRI_ERROR_NO_ERROR) {
      return res;
    }
  }

  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief abort open transactions
////////////////////////////////////////////////////////////////////////////////

int RecoverState::abortOpenTransactions() {
  if (failedTransactions.empty()) {
    // nothing to do
    return TRI_ERROR_NO_ERROR;
  }

  LOG(TRACE) << "writing abort markers for still open transactions";
  int res = TRI_ERROR_NO_ERROR;

  try {
    // write abort markers for all transactions
    for (auto it = failedTransactions.begin(); it != failedTransactions.end();
         ++it) {
      TRI_voc_tid_t transactionId = (*it).first;

      if ((*it).second.second) {
        // already handled
        continue;
      }

      TRI_voc_tick_t databaseId = (*it).second.first;

      AbortTransactionMarker marker(databaseId, transactionId);
      SlotInfoCopy slotInfo =
          arangodb::wal::LogfileManager::instance()->allocateAndWrite(
              marker.mem(), marker.size(), false);

      if (slotInfo.errorCode != TRI_ERROR_NO_ERROR) {
        THROW_ARANGO_EXCEPTION(slotInfo.errorCode);
      }
    }
  } catch (arangodb::basics::Exception const& ex) {
    res = ex.code();
  } catch (...) {
    res = TRI_ERROR_INTERNAL;
  }

  return res;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief remove all empty logfiles found during logfile inspection
////////////////////////////////////////////////////////////////////////////////

int RecoverState::removeEmptyLogfiles() {
  if (emptyLogfiles.empty()) {
    return TRI_ERROR_NO_ERROR;
  }

  LOG(TRACE) << "removing empty WAL logfiles";

  for (auto it = emptyLogfiles.begin(); it != emptyLogfiles.end(); ++it) {
    auto filename = (*it);

    if (basics::FileUtils::remove(filename, 0)) {
      LOG(TRACE) << "removing empty WAL logfile '" << filename << "'";
    }
  }

  emptyLogfiles.clear();

  return TRI_ERROR_NO_ERROR;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief fill the secondary indexes of all collections used in recovery
////////////////////////////////////////////////////////////////////////////////

int RecoverState::fillIndexes() {
  // release all collections
  for (auto it = openedCollections.begin(); it != openedCollections.end();
       ++it) {
    TRI_vocbase_col_t* collection = (*it).second;
    TRI_document_collection_t* document = collection->_collection;

    TRI_ASSERT(document != nullptr);

    // activate secondary indexes
    document->useSecondaryIndexes(true);

    arangodb::SingleCollectionTransaction trx(arangodb::StandaloneTransactionContext::Create(collection->_vocbase),
        document->_info.id(), TRI_TRANSACTION_WRITE);

    int res = TRI_FillIndexesDocumentCollection(&trx, collection, document);

    if (res != TRI_ERROR_NO_ERROR) {
      return res;
    }
  }

  return TRI_ERROR_NO_ERROR;
}