regex.hpp

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/*
  REGEX.hpp  -  helpers for working with regular expressions
 
   Copyright (C)
     2022,            Hermann Vosseler <Ichthyostega@web.de>
 
 **Lumiera** is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the
 Free Software Foundation; either version 2 of the License, or (at your
 option) any later version. See the file COPYING for further details.
 
*/
 
 
#ifndef LIB_REGEX_H
#define LIB_REGEX_H
 
 
#include "lib/iter-adapter.hpp"
 
#include <regex>
#include <string>
#include <optional>
 
namespace util {
  
  using std::regex;
  using std::smatch;
  using std::string;
  using std::string_view;
  
  
  
  struct RegexSearchIter
    : std::sregex_iterator
    {
      RegexSearchIter()  = default;
      
      RegexSearchIter (string const& toParse, regex const& regex)
        : std::sregex_iterator{toParse.begin(), toParse.end(), regex}
        { }
      RegexSearchIter (string_view toParse, regex const& regex)
        : std::sregex_iterator{string::const_iterator{toParse.begin()}
                              ,string::const_iterator{toParse.end()}, regex}
        { }
      
      operator bool()  const { return isValid(); }
      
      bool isValid ()  const { return (*this)->ready() and not (*this)->empty(); }
      bool empty ()    const { return not isValid(); }
 
      LIFT_PARENT_INCREMENT_OPERATOR (std::sregex_iterator);
      ENABLE_USE_IN_STD_RANGE_FOR_LOOPS (RegexSearchIter);
    };
  
  
  template<typename STR>
  std::optional<smatch>
  matchAtStart (STR&& toParse, regex const& regex)
  {
    auto search = RegexSearchIter{std::forward<STR> (toParse), regex};
    if (search and 0 == search->position(0))
      return *search;
    else
      return std::nullopt;
  }
  
  template<typename STR>
  size_t
  leadingWhitespace (STR&& toParse)
  {
    static const regex LEADING_WHITESPACE{"^\\s*", regex::optimize};
    auto search = RegexSearchIter{std::forward<STR> (toParse), LEADING_WHITESPACE};
    return search? search->length() : 0;
  }
  
}// namespace util
 
namespace lib {
  using std::regex;
  using std::smatch;
  using std::string;
}// namespace lib
#endif/*LIB_REGEX_H*/