// Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.
//
// 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.

#ifndef FORTRAN_PARSER_PREPROCESSOR_H_
#define FORTRAN_PARSER_PREPROCESSOR_H_

// A Fortran-aware preprocessing module used by the prescanner to implement
// preprocessing directives and macro replacement.  Intended to be efficient
// enough to always run on all source files even when no preprocessing is
// performed, so that special compiler command options &/or source file name
// extensions for preprocessing will not be necessary.

#include "char-block.h"
#include "provenance.h"
#include "token-sequence.h"
#include <cstddef>
#include <list>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

namespace Fortran::parser {

class Prescanner;

// Defines a macro
class Definition {
public:
  Definition(const TokenSequence &, std::size_t firstToken, std::size_t tokens);
  Definition(const std::vector<std::string> &argNames, const TokenSequence &,
      std::size_t firstToken, std::size_t tokens, bool isVariadic = false);
  Definition(const std::string &predefined, AllSources &);

  bool isFunctionLike() const { return isFunctionLike_; }
  std::size_t argumentCount() const { return argumentCount_; }
  bool isVariadic() const { return isVariadic_; }
  bool isDisabled() const { return isDisabled_; }
  bool isPredefined() const { return isPredefined_; }
  const TokenSequence &replacement() const { return replacement_; }

  bool set_isDisabled(bool disable);

  TokenSequence Apply(const std::vector<TokenSequence> &args, AllSources &);

private:
  static TokenSequence Tokenize(const std::vector<std::string> &argNames,
      const TokenSequence &token, std::size_t firstToken, std::size_t tokens);

  bool isFunctionLike_{false};
  std::size_t argumentCount_{0};
  bool isVariadic_{false};
  bool isDisabled_{false};
  bool isPredefined_{false};
  TokenSequence replacement_;
};

// Preprocessing state
class Preprocessor {
public:
  explicit Preprocessor(AllSources &);

  void Define(std::string macro, std::string value);
  void Undefine(std::string macro);

  std::optional<TokenSequence> MacroReplacement(
      const TokenSequence &, const Prescanner &);

  // Implements a preprocessor directive.
  void Directive(const TokenSequence &, Prescanner *);

private:
  enum class IsElseActive { No, Yes };
  enum class CanDeadElseAppear { No, Yes };

  CharBlock SaveTokenAsName(const CharBlock &);
  bool IsNameDefined(const CharBlock &);
  TokenSequence ReplaceMacros(const TokenSequence &, const Prescanner &);
  void SkipDisabledConditionalCode(
      const std::string &, IsElseActive, Prescanner *, ProvenanceRange);
  bool IsIfPredicateTrue(const TokenSequence &expr, std::size_t first,
      std::size_t exprTokens, Prescanner *);

  AllSources &allSources_;
  std::list<std::string> names_;
  std::unordered_map<CharBlock, Definition> definitions_;
  std::stack<CanDeadElseAppear> ifStack_;
};

}  // namespace Fortran::parser
#endif  // FORTRAN_PARSER_PREPROCESSOR_H_