text: /**
   *    Copyright (C) 2018-present MongoDB, Inc.
   *
   *    This program is free software: you can redistribute it and/or modify
   *    it under the terms of the Server Side Public License, version 1,
   *    as published by MongoDB, Inc.
   *
   *    This program is distributed in the hope that it will be useful,
   *    but WITHOUT ANY WARRANTY; without even the implied warranty of
   *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *    Server Side Public License for more details.
   *
   *    You should have received a copy of the Server Side Public License
   *    along with this program. If not, see
   *    <http://www.mongodb.com/licensing/server-side-public-license>.
   *
   *    As a special exception, the copyright holders give permission to link the
   *    code of portions of this program with the OpenSSL library under certain
   *    conditions as described in each individual source file and distribute
   *    linked combinations including the program with the OpenSSL library. You
   *    must comply with the Server Side Public License in all respects for
   *    all of the code used other than as permitted herein. If you modify file(s)
   *    with this exception, you may extend this exception to your version of the
   *    file(s), but you are not obligated to do so. If you do not wish to do so,
   *    delete this exception statement from your version. If you delete this
   *    exception statement from all source files in the program, then also delete
   *    it in the license file.
   */
  
  #pragma once
  
  #include <map>
  #include <memory>
  #include <string>
  #include <utility>
  #include <vector>
  
  #include "mongo/db/update/update_leaf_node.h"
  
  namespace mongo {
  
  /**
   * Represents the application of a $rename to the value at the end of a path, where the path
   * represents the rename destination.
   */
  class RenameNode : public UpdateLeafNode {
  public:
      /**
       * This init provides input validation on the source field (stored as the field name in
       * "modExpr") and the destination field (stored as the value in "modExpr").
       */
      Status init(BSONElement modExpr, const boost::intrusive_ptr<ExpressionContext>& expCtx) final;
  
      std::unique_ptr<UpdateNode> clone() const final {
          return std::make_unique<RenameNode>(*this);
      }
  
      void setCollator(const CollatorInterface* collator) final {}
  
      ApplyResult apply(ApplyParams applyParams,
                        UpdateNodeApplyParams updateNodeApplyParams) const final;
  
      void produceSerializationMap(
          FieldRef* currentPath,
          std::map<std::string, std::vector<std::pair<std::string, BSONObj>>>*
              operatorOrientedUpdates) const final {
          // The RenameNode sits in the update tree at the destination path, because that's the path
          // that may need to be synthesized if it's not already in the document. However, the
          // destination path is the _value_ and goes on the right side of the rename element (i.e.:
          // {$rename: {sourcePath: "destPath"}}), unlike all other modifiers, where the path to
          // synthesize is the field (on the left).
          (*operatorOrientedUpdates)["$rename"].emplace_back(_val.fieldName(),
                                                             BSON("" << currentPath->dottedField()));
      }
  
      void acceptVisitor(UpdateNodeVisitor* visitor) final {
          visitor->visit(this);
      }
  
      BSONElement getValue() const {
          return _val;
      }
  
  private:
      BSONElement _val;
  };
  
  }  // namespace mongo
  