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/**
* Copyright (C) 2019-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 "mongo/db/query/tree_walker.h"
namespace mongo {
namespace projection_ast {
class MatchExpressionASTNode;
class ProjectionPathASTNode;
class ProjectionPositionalASTNode;
class ProjectionSliceASTNode;
class ProjectionElemMatchASTNode;
class ExpressionASTNode;
class BooleanConstantASTNode;
/**
* Visitor pattern for ProjectionAST.
*
* This code is not responsible for traversing the AST, only for performing the double-dispatch.
*
* If the visitor doesn't intend to modify the AST, then the template argument 'IsConst' should be
* set to 'true'. In this case all 'visit()' methods will take a const pointer to a visiting node.
*/
template <bool IsConst = false>
class ProjectionASTVisitor {
public:
virtual ~ProjectionASTVisitor() = default;
virtual void visit(tree_walker::MaybeConstPtr<IsConst, MatchExpressionASTNode> node) = 0;
virtual void visit(tree_walker::MaybeConstPtr<IsConst, ProjectionPathASTNode> node) = 0;
virtual void visit(tree_walker::MaybeConstPtr<IsConst, ProjectionPositionalASTNode> node) = 0;
virtual void visit(tree_walker::MaybeConstPtr<IsConst, ProjectionSliceASTNode> node) = 0;
virtual void visit(tree_walker::MaybeConstPtr<IsConst, ProjectionElemMatchASTNode> node) = 0;
virtual void visit(tree_walker::MaybeConstPtr<IsConst, ExpressionASTNode> node) = 0;
virtual void visit(tree_walker::MaybeConstPtr<IsConst, BooleanConstantASTNode> node) = 0;
};
using ProjectionASTMutableVisitor = ProjectionASTVisitor<false>;
using ProjectionASTConstVisitor = ProjectionASTVisitor<true>;
} // namespace projection_ast
} // namespace mongo
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