text: ////////////////////////////////////////////////////////////////////////////////
  /// 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 Michael Hackstein
  ////////////////////////////////////////////////////////////////////////////////
  
  #include "ClusterEdgeCursor.h"
  
  #include "Cluster/ClusterMethods.h"
  #include "Cluster/ClusterTraverser.h"
  #include "Graph/ClusterTraverserCache.h"
  #include "Graph/TraverserCache.h"
  #include "Transaction/Helpers.h"
  #include "Transaction/Methods.h"
  
  #include <velocypack/Slice.h>
  #include <velocypack/velocypack-aliases.h>
  
  using namespace arangodb;
  using namespace arangodb::graph;
  using namespace arangodb::traverser;
  
  // Traverser variant
  ClusterEdgeCursor::ClusterEdgeCursor(arangodb::velocypack::StringRef vertexId, uint64_t depth,
                                       graph::BaseOptions* opts)
      : _position(0),
        _resolver(opts->trx()->resolver()),
        _opts(opts),
        _cache(static_cast<ClusterTraverserCache*>(opts->cache())),
        _httpRequests(0) {
    TRI_ASSERT(_cache != nullptr);
    auto trx = _opts->trx();
    transaction::BuilderLeaser leased(trx);
    transaction::BuilderLeaser b(trx);
  
    b->add(VPackValuePair(vertexId.data(), vertexId.length(), VPackValueType::String));
    fetchEdgesFromEngines(trx->vocbase().name(), _cache->engines(), b->slice(), depth,
                          _cache->cache(), _edgeList, _cache->datalake(), *(leased.get()),
                          _cache->filteredDocuments(), _cache->insertedDocuments());
    _httpRequests += _cache->engines()->size();
  }
  
  // ShortestPath variant
  ClusterEdgeCursor::ClusterEdgeCursor(arangodb::velocypack::StringRef vertexId, bool backward, graph::BaseOptions* opts)
      : _position(0),
        _resolver(opts->trx()->resolver()),
        _opts(opts),
        _cache(static_cast<ClusterTraverserCache*>(opts->cache())),
        _httpRequests(0) {
    TRI_ASSERT(_cache != nullptr);
    auto trx = _opts->trx();
    transaction::BuilderLeaser leased(trx);
    transaction::BuilderLeaser b(trx);
  
    b->add(VPackValuePair(vertexId.data(), vertexId.length(), VPackValueType::String));
    fetchEdgesFromEngines(trx->vocbase().name(), _cache->engines(), b->slice(),
                          backward, _cache->cache(), _edgeList, _cache->datalake(),
                          *(leased.get()), _cache->insertedDocuments());
    _httpRequests += _cache->engines()->size();
  }
  
  bool ClusterEdgeCursor::next(EdgeCursor::Callback const& callback) {
    if (_position < _edgeList.size()) {
      VPackSlice edge = _edgeList[_position];
      callback(EdgeDocumentToken(edge), edge, _position);
      ++_position;
      return true;
    }
    return false;
  }
  
  void ClusterEdgeCursor::readAll(EdgeCursor::Callback const& callback) {
    for (VPackSlice const& edge : _edgeList) {
      callback(EdgeDocumentToken(edge), edge, _position);
    }
  }
  