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 <memory>
  #include <string>
  
  #include "mongo/base/status_with.h"
  #include "mongo/db/query/canonical_query.h"
  
  namespace mongo {
  
  class BSONObj;
  class ExtensionsCallback;
  class NamespaceString;
  class OperationContext;
  
  /**
   * The parsed form of the distinct command request.
   */
  class ParsedDistinct {
  public:
      static const char kKeyField[];
      static const char kQueryField[];
      static const char kCollationField[];
      static const char kCommentField[];
      static const char kUnwoundArrayFieldForViewUnwind[];
  
      ParsedDistinct(std::unique_ptr<CanonicalQuery> query, const std::string key)
          : _query(std::move(query)), _key(std::move(key)) {}
  
      const CanonicalQuery* getQuery() const {
          return _query.get();
      }
  
      /**
       * Releases ownership of the canonical query to the caller.
       */
      std::unique_ptr<CanonicalQuery> releaseQuery() {
          invariant(_query.get());
          return std::move(_query);
      }
  
      const std::string& getKey() const {
          return _key;
      }
  
      /**
       * Convert this ParsedDistinct into an aggregation command object.
       */
      StatusWith<BSONObj> asAggregationCommand() const;
  
      /**
       * 'extensionsCallback' allows for additional mongod parsing. If called from mongos, an
       * ExtensionsCallbackNoop object should be passed to skip this parsing.
       */
      static StatusWith<ParsedDistinct> parse(OperationContext* opCtx,
                                              const NamespaceString& nss,
                                              const BSONObj& cmdObj,
                                              const ExtensionsCallback& extensionsCallback,
                                              bool isExplain,
                                              const CollatorInterface* defaultCollator = nullptr);
  
  private:
      std::unique_ptr<CanonicalQuery> _query;
  
      // The field for which we are getting distinct values.
      const std::string _key;
  };
  
  }  // namespace mongo
  