// Copyright 2024 Google LLC

//

// 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

//

//     https://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.

#ifndef THIRD_PARTY_CEL_CPP_COMMON_AST_VISITOR_NATIVE_H_

#define THIRD_PARTY_CEL_CPP_COMMON_AST_VISITOR_NATIVE_H_

#include "common/constant.h"

#include "common/expr.h"

namespace cel {

// ComprehensionArg specifies arg_num values passed to PostVisitArg

// for subexpressions of Comprehension.

enum ComprehensionArg {

  ITER_RANGE,

  ACCU_INIT,

  LOOP_CONDITION,

  LOOP_STEP,

  RESULT,

};

// Callback handler class, used in conjunction with AstTraverse.

// Methods of this class are invoked when AST nodes with corresponding

// types are processed.

//

// For all types with children, the children will be visited in the natural

// order from first to last.  For structs, keys are visited before values.

class AstVisitor {

 public:

  virtual ~AstVisitor() = default;

  // Expr node handler method. Called for all Expr nodes.

  // Is invoked before child Expr nodes being processed.

  virtual void PreVisitExpr(const Expr&) = 0;

  // Expr node handler method. Called for all Expr nodes.

  // Is invoked after child Expr nodes are processed.

  virtual void PostVisitExpr(const Expr&) = 0;

  // Const node handler.

  // Invoked after child nodes are processed.

  virtual void PostVisitConst(const Expr&, const Constant&) = 0;

  // Ident node handler.

  // Invoked after child nodes are processed.

  virtual void PostVisitIdent(const Expr&, const IdentExpr&) = 0;

  // Select node handler

  // Invoked before child nodes are processed.

  virtual void PreVisitSelect(const Expr&, const SelectExpr&) = 0;

  // Select node handler

  // Invoked after child nodes are processed.

  virtual void PostVisitSelect(const Expr&, const SelectExpr&) = 0;

  // Call node handler group

  // We provide finer granularity for Call node callbacks to allow special

  // handling for short-circuiting

  // PreVisitCall is invoked before child nodes are processed.

  virtual void PreVisitCall(const Expr&, const CallExpr&) = 0;

  // Invoked after all child nodes are processed.

  virtual void PostVisitCall(const Expr&, const CallExpr&) = 0;

  // Invoked after target node is processed.

  // Expr is the call expression.

  virtual void PostVisitTarget(const Expr&) = 0;

  // Invoked before all child nodes are processed.

  virtual void PreVisitComprehension(const Expr&, const ComprehensionExpr&) = 0;

  // Invoked before comprehension child node is processed.

  virtual void PreVisitComprehensionSubexpression(

      const Expr&, const ComprehensionExpr& compr,

      ComprehensionArg comprehension_arg) {}

  // Invoked after comprehension child node is processed.

  virtual void PostVisitComprehensionSubexpression(

      const Expr&, const ComprehensionExpr& compr,

      ComprehensionArg comprehension_arg) {}

  // Invoked after all child nodes are processed.

  virtual void PostVisitComprehension(const Expr&,

                                      const ComprehensionExpr&) = 0;

  // Invoked after each argument node processed.

  // For Call arg_num is the index of the argument.

  // For Comprehension arg_num is specified by ComprehensionArg.

  // Expr is the call expression.

  virtual void PostVisitArg(const Expr&, int arg_num) = 0;

  // List node handler

  // Invoked after child nodes are processed.

  virtual void PostVisitList(const Expr&, const ListExpr&) = 0;

  // Struct node handler

  // Invoked after child nodes are processed.

  virtual void PostVisitStruct(const Expr&, const StructExpr&) = 0;

  // Map node handler

  // Invoked after child nodes are processed.

  virtual void PostVisitMap(const Expr&, const MapExpr&) = 0;

};

}  // namespace cel

#endif  // THIRD_PARTY_CEL_CPP_COMMON_AST_VISITOR_NATIVE_H_