////////////////////////////////////////////////////////////////////////////////
/// 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 ARANGOD_CLUSTER_CLUSTER_TRAVERSER_H
#define ARANGOD_CLUSTER_CLUSTER_TRAVERSER_H 1

#include "VocBase/Traverser.h"

namespace arangodb {
class CollectionNameResolver;
class Transaction;

namespace traverser {

class ClusterTraversalPath;

class ClusterTraverser : public Traverser {
  friend class ClusterTraversalPath;

 public:
  ClusterTraverser(
      std::vector<std::string> edgeCollections, TraverserOptions& opts,
      std::string const& dbname, Transaction* trx,
      std::unordered_map<size_t, std::vector<TraverserExpression*>> const*
          expressions)
      : Traverser(opts, expressions),
        _edgeCols(edgeCollections),
        _dbname(dbname),
        _trx(trx) {
          _edgeGetter = std::make_unique<ClusterEdgeGetter>(this);
          if (opts.uniqueVertices == TraverserOptions::UniquenessLevel::GLOBAL) {
            _vertexGetter = std::make_unique<UniqueVertexGetter>(this);
          } else {
            _vertexGetter = std::make_unique<VertexGetter>(this);
          }
        }

  ~ClusterTraverser() {
  }

  void setStartVertex(std::string const&) override;

  TraversalPath* next() override;

 private:

  void fetchVertices(std::unordered_set<std::string>&, size_t);

  bool vertexMatchesCondition(arangodb::velocypack::Slice const&,
                              std::vector<TraverserExpression*> const&);

  class VertexGetter : public arangodb::basics::VertexGetter<std::string, std::string> {
   public:
    explicit VertexGetter(ClusterTraverser* traverser)
        : _traverser(traverser) {}

    virtual ~VertexGetter() = default;

    virtual bool getVertex(std::string const&, std::string const&, size_t,
                           std::string&) override;
    virtual void reset();

   protected:
    ClusterTraverser* _traverser;
  };

  class UniqueVertexGetter : public VertexGetter {
   public:
    explicit UniqueVertexGetter(ClusterTraverser* traverser)
        : VertexGetter(traverser) {}

    ~UniqueVertexGetter() = default;

    bool getVertex(std::string const&, std::string const&, size_t,
                    std::string&) override;

    void reset() override;

    void setStartVertex(std::string const& id) override {
      _returnedVertices.emplace(id);
    }

   private:
    std::unordered_set<std::string> _returnedVertices;
  };

  class ClusterEdgeGetter : public arangodb::basics::EdgeGetter<std::string, std::string, size_t> {
   public:
    explicit ClusterEdgeGetter(ClusterTraverser* traverser)
        : _traverser(traverser), _continueConst(1) {}

    void getEdge(std::string const&, std::vector<std::string>&, size_t*&,
                 size_t&) override;

    void getAllEdges(std::string const&, std::vector<std::string>&, size_t depth) override;

   private:
    ClusterTraverser* _traverser;

    size_t _continueConst;
  };

  std::unordered_map<std::string,
                     std::shared_ptr<arangodb::velocypack::Buffer<uint8_t>>>
      _edges;

  std::unordered_map<std::string,
                     std::shared_ptr<arangodb::velocypack::Buffer<uint8_t>>>
      _vertices;

  std::stack<std::stack<std::string>> _iteratorCache;

  std::vector<std::string> _edgeCols;

  std::string _dbname;

  std::unique_ptr<VertexGetter> _vertexGetter;

  std::unique_ptr<ClusterEdgeGetter> _edgeGetter;

  arangodb::velocypack::Builder _builder;

  arangodb::Transaction* _trx;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief internal cursor to enumerate the paths of a graph
  //////////////////////////////////////////////////////////////////////////////

  std::unique_ptr<arangodb::basics::PathEnumerator<std::string, std::string, size_t>> _enumerator;
};

class ClusterTraversalPath : public TraversalPath {
 public:
  ClusterTraversalPath(
      ClusterTraverser const* traverser,
      arangodb::basics::EnumeratedPath<std::string, std::string> const& path)
      : _path(path), _traverser(traverser) {
  }

  void pathToVelocyPack(Transaction*, arangodb::velocypack::Builder&) override;

  void lastEdgeToVelocyPack(Transaction*,
                            arangodb::velocypack::Builder&) override;

  void lastVertexToVelocyPack(Transaction*,
                              arangodb::velocypack::Builder&) override;

 private:
  arangodb::basics::EnumeratedPath<std::string, std::string> _path;

  ClusterTraverser const* _traverser;
};

}  // traverser
}  // triagens

#endif