////////////////////////////////////////////////////////////////////////////////
/// 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"
#include "VocBase/PathEnumerator.h"

namespace arangodb {
class CollectionNameResolver;
class Transaction;

namespace traverser {

class PathEnumerator;

class ClusterTraverser final : public Traverser {

 public:
  ClusterTraverser(
      std::vector<std::string> const& edgeCollections, TraverserOptions& opts,
      std::string const& dbname, Transaction* trx)
      : Traverser(opts),
        _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;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Function to load edges for a node
  //////////////////////////////////////////////////////////////////////////////

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

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Function to load all edges for a list of nodes
  //////////////////////////////////////////////////////////////////////////////

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

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Function to load the other sides vertex of an edge
  ///        Returns true if the vertex passes filtering conditions
  //////////////////////////////////////////////////////////////////////////////

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

  bool next() override;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Builds only the last vertex as AQLValue
  //////////////////////////////////////////////////////////////////////////////

  aql::AqlValue lastVertexToAqlValue() override;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Builds only the last edge as AQLValue
  //////////////////////////////////////////////////////////////////////////////

  aql::AqlValue lastEdgeToAqlValue() override;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Builds the complete path as AQLValue
  ///        Has the format:
  ///        {
  ///           vertices: [<vertex-as-velocypack>],
  ///           edges: [<edge-as-velocypack>]
  ///        }
  ///        NOTE: Will clear the given buffer and will leave the path in it.
  //////////////////////////////////////////////////////////////////////////////

  aql::AqlValue pathToAqlValue(arangodb::velocypack::Builder&) override;

 protected:
  //////////////////////////////////////////////////////////////////////////////
  /// @brief Function to fetch the real data of a vertex into an AQLValue
  //////////////////////////////////////////////////////////////////////////////

  aql::AqlValue fetchVertexData(std::string const&) override;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Function to fetch the real data of an edge into an AQLValue
  //////////////////////////////////////////////////////////////////////////////

  aql::AqlValue fetchEdgeData(std::string const&) override;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Function to add the real data of a vertex into a velocypack builder
  //////////////////////////////////////////////////////////////////////////////

  void addVertexToVelocyPack(std::string const&,
                             arangodb::velocypack::Builder&) override;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief Function to add the real data of an edge into a velocypack builder
  //////////////////////////////////////////////////////////////////////////////

  void addEdgeToVelocyPack(std::string const&,
                           arangodb::velocypack::Builder&) override;

 private:

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

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

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

    virtual ~VertexGetter() = default;

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

    virtual void setStartVertex(std::string const&) {}

   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:
    explicit ClusterEdgeGetter(ClusterTraverser* traverser)
        : _traverser(traverser), _continueConst(1) {}

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

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

   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::traverser::PathEnumerator> _enumerator;
};

}  // traverser
}  // arangodb

#endif