text: ////////////////////////////////////////////////////////////////////////////////
  /// 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 Michael Hackstein
  ////////////////////////////////////////////////////////////////////////////////
  
  #ifndef ARANGODB_GRAPH_CONSTANT_WEIGHT_SHORTEST_PATH_FINDER_H
  #define ARANGODB_GRAPH_CONSTANT_WEIGHT_SHORTEST_PATH_FINDER_H 1
  
  #include "Basics/VelocyPackHelper.h"
  #include "Graph/EdgeDocumentToken.h"
  #include "Graph/ShortestPathFinder.h"
  
  #include <velocypack/StringRef.h>
  #include <deque>
  
  namespace arangodb {
  
  namespace velocypack {
  class Slice;
  }
  
  namespace graph {
  
  struct ShortestPathOptions;
  
  class ConstantWeightShortestPathFinder : public ShortestPathFinder {
   private:
    struct PathSnippet {
      arangodb::velocypack::StringRef const _pred;
      graph::EdgeDocumentToken _path;
  
      PathSnippet(arangodb::velocypack::StringRef& pred, graph::EdgeDocumentToken&& path);
    };
  
    typedef std::deque<arangodb::velocypack::StringRef> Closure;
    typedef std::unordered_map<arangodb::velocypack::StringRef, PathSnippet*> Snippets;
  
   public:
    explicit ConstantWeightShortestPathFinder(ShortestPathOptions& options);
  
    ~ConstantWeightShortestPathFinder();
  
    bool shortestPath(arangodb::velocypack::Slice const& start,
                      arangodb::velocypack::Slice const& end,
                      arangodb::graph::ShortestPathResult& result) override;
  
   private:
    void expandVertex(bool backward, arangodb::velocypack::StringRef vertex);
  
    void clearVisited();
  
    bool expandClosure(Closure& sourceClosure, Snippets& sourceSnippets,
                       Snippets& targetSnippets, bool direction, arangodb::velocypack::StringRef& result);
  
    void fillResult(arangodb::velocypack::StringRef& n, arangodb::graph::ShortestPathResult& result);
  
   private:
    Snippets _leftFound;
    Closure _leftClosure;
  
    Snippets _rightFound;
    Closure _rightClosure;
  
    Closure _nextClosure;
  
    std::vector<arangodb::velocypack::StringRef> _neighbors;
    std::vector<graph::EdgeDocumentToken> _edges;
  };
  
  }  // namespace graph
  }  // namespace arangodb
  #endif
  