lexer.hpp

#ifndef LEXER
#define LEXER

#include <iterator>
#include <regex>
#include <string>
#include <vector>

#include "types.hpp"

class Lexer {
  std::vector<std::pair<std::string, Token>> REGEX_TO_TOKENS = {
      {"select", Token::SELECT},
      {"create", Token::CREATE},
      {"insert", Token::INSERT},
      {"values", Token::VALUES},
      {"from", Token::FROM},
      {"into", Token::INTO},
      {"table", Token::TABLE},
      {"drop", Token::DROP},
      {"int", Token::TYPE_INT},
      {"=", Token::EQUAL},
      {"where", Token::WHERE},
      {"string", Token::TYPE_STRING},
      {"\\*", Token::ALL_ATTRIBUTES},
      {"[A-Za-z0-9]+", Token::IDENTIFIER},
      {"\\(", Token::LPAREN},
      {"\\)", Token::RPAREN},
      {",", Token::COMMA}};
  int prev_token_pos, curr_token_pos, next_token_pos;
  std::vector<std::pair<std::string, Token>> tokens;

  const std::string get_valid_regex() const {
    std::string valid = "";

    for (const auto& regex_to_token : REGEX_TO_TOKENS) {
      valid += "(" + regex_to_token.first + ")|";
    }
    valid.pop_back();

    return valid;
  }

  const Token& get_token_at_idx(const int& idx) const {
    return REGEX_TO_TOKENS[idx].second;
  }

 public:
  Lexer()
      : prev_token_pos(-1),
        curr_token_pos(0),
        next_token_pos(0),
        tokens(std::vector<std::pair<std::string, Token>>()){};

  ~Lexer() = default;

  void lex(const std::string&);

  const bool has_next_token() const noexcept;

  const std::pair<std::string, Token> get_prev_token() const noexcept;

  const std::pair<std::string, Token> get_curr_token() noexcept;
};

#endif