////////////////////////////////////////////////////////////////////////////////
/// 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_AQL_INDEX_NODE_H
#define ARANGOD_AQL_INDEX_NODE_H 1

#include <memory>
#include <vector>

#include "Aql/CollectionAccessingNode.h"
#include "Aql/DocumentProducingNode.h"
#include "Aql/ExecutionNode.h"
#include "Aql/RegisterPlan.h"
#include "Aql/types.h"
#include "Containers/HashSet.h"
#include "Indexes/IndexIterator.h"
#include "Transaction/Methods.h"

namespace arangodb {

namespace aql {
struct Collection;
class Condition;
class ExecutionBlock;
class ExecutionEngine;
class ExecutionPlan;
class Expression;

/// @brief struct to hold the member-indexes in the _condition node
struct NonConstExpression {
  std::unique_ptr<Expression> expression;
  std::vector<size_t> const indexPath;

  NonConstExpression(std::unique_ptr<Expression> exp, std::vector<size_t>&& idxPath);
};

/// @brief class IndexNode
class IndexNode : public ExecutionNode, public DocumentProducingNode, public CollectionAccessingNode {
  friend class ExecutionBlock;

 public:
  IndexNode(ExecutionPlan* plan, size_t id, aql::Collection const* collection,
            Variable const* outVariable,
            std::vector<transaction::Methods::IndexHandle> const& indexes,
            std::unique_ptr<Condition> condition, IndexIteratorOptions const&);

  IndexNode(ExecutionPlan*, arangodb::velocypack::Slice const& base);

  ~IndexNode() override;

  /// @brief return the type of the node
  NodeType getType() const final;

  /// @brief return the condition for the node
  Condition* condition() const;

  /// @brief whether or not all indexes are accessed in reverse order
  IndexIteratorOptions options() const;

  /// @brief set reverse mode
  void setAscending(bool value);

  /// @brief whether or not the index node needs a post sort of the results
  /// of multiple shards in the cluster (via a GatherNode).
  /// not all queries that use an index will need to produce a sorted result
  /// (e.g. if the index is used only for filtering)
  bool needsGatherNodeSort() const;
  void needsGatherNodeSort(bool value);

  /// @brief export to VelocyPack
  void toVelocyPackHelper(arangodb::velocypack::Builder&, unsigned flags,
                          std::unordered_set<ExecutionNode const*>& seen) const final;

  /// @brief creates corresponding ExecutionBlock
  std::unique_ptr<ExecutionBlock> createBlock(
      ExecutionEngine& engine,
      std::unordered_map<ExecutionNode*, ExecutionBlock*> const&) const override;

  /// @brief clone ExecutionNode recursively
  ExecutionNode* clone(ExecutionPlan* plan, bool withDependencies,
                       bool withProperties) const final;

  /// @brief getVariablesSetHere
  std::vector<Variable const*> getVariablesSetHere() const final;

  /// @brief getVariablesUsedHere, modifying the set in-place
  void getVariablesUsedHere(::arangodb::containers::HashSet<Variable const*>& vars) const final;

  /// @brief estimateCost
  CostEstimate estimateCost() const final;

  /// @brief getIndexes, hand out the indexes used
  std::vector<transaction::Methods::IndexHandle> const& getIndexes() const;

  /// @brief called to build up the matching positions of the index values for
  /// the projection attributes (if any)
  void initIndexCoversProjections();

  void planNodeRegisters(std::vector<aql::RegisterId>& nrRegsHere,
                         std::vector<aql::RegisterId>& nrRegs,
                         std::unordered_map<aql::VariableId, aql::VarInfo>& varInfo,
                         unsigned int& totalNrRegs, unsigned int depth) const;

  bool isLateMaterialized() const noexcept {
    TRI_ASSERT((_outNonMaterializedDocId == nullptr && _outNonMaterializedIndVars.second.empty()) ||
               !(_outNonMaterializedDocId == nullptr || _outNonMaterializedIndVars.second.empty()));
    return !_outNonMaterializedIndVars.second.empty();
  }

  struct IndexVariable {
    size_t indexFieldNum;
    Variable const* var;
  };

  using IndexValuesVars = std::pair<TRI_idx_iid_t, std::vector<std::pair<size_t, Variable const*>>>;

  using IndexValuesRegisters = std::pair<TRI_idx_iid_t, std::unordered_map<size_t, RegisterId>>;

  using IndexVarsInfo = std::unordered_map<std::vector<arangodb::basics::AttributeName> const*, IndexVariable>;

  void setLateMaterialized(aql::Variable const* docIdVariable, TRI_idx_iid_t commonIndexId, IndexVarsInfo const& indexVariables);

 private:
  void initializeOnce(bool hasV8Expression, std::vector<Variable const*>& inVars,
                      std::vector<RegisterId>& inRegs,
                      std::vector<std::unique_ptr<NonConstExpression>>& nonConstExpressions,
                      transaction::Methods* trxPtr) const;

  /// @brief adds a UNIQUE() to a dynamic IN condition
  arangodb::aql::AstNode* makeUnique(arangodb::aql::AstNode*, transaction::Methods* trx) const;

 private:
  /// @brief the index
  std::vector<transaction::Methods::IndexHandle> _indexes;

  /// @brief the index(es) condition
  std::unique_ptr<Condition> _condition;

  /// @brief the index sort order - this is the same order for all indexes
  bool _needsGatherNodeSort;

  /// @brief the index iterator options - same for all indexes
  IndexIteratorOptions _options;

  /// @brief output variable to write only non-materialized document ids
  aql::Variable const* _outNonMaterializedDocId;

  /// @brief output variables to non-materialized document index references
  IndexValuesVars _outNonMaterializedIndVars;
};

}  // namespace aql
}  // namespace arangodb

#endif