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#ifndef MOZC_REWRITER_CALCULATOR_CALCULATOR_H_
#define MOZC_REWRITER_CALCULATOR_CALCULATOR_H_

#include <cstddef>
#include <string>
#include <utility>
#include <vector>

#include "absl/container/flat_hash_map.h"
#include "absl/strings/string_view.h"

namespace mozc {

class Calculator {
 public:
  Calculator();

  bool CalculateString(absl::string_view key, std::string* result) const;

 private:
  using TokenSequence = std::vector<std::pair<int, double>>;

  // Max byte length of operator character
  static constexpr size_t kMaxLengthOfOperator = 3;

  // Tokenizes |expression_body| and sets the tokens into |tokens|.
  // It returns false if |expression_body| includes an invalid token or
  // does not include both of a number token and an operator token.
  // Parenthesis is not considered as an operator.
  bool Tokenize(absl::string_view expression_body, TokenSequence* tokens) const;

  // Perform calculation with a given sequence of token.
  bool CalculateTokens(const TokenSequence& tokens, double* result_value) const;

  // Mapping from operator character such as '+' to the corresponding
  // token type such as PLUS.
  absl::flat_hash_map<absl::string_view, int> operator_map_;
};

}  // namespace mozc

#endif  // MOZC_REWRITER_CALCULATOR_CALCULATOR_H_
