text: #ifndef SASS_PRELEXER_H
  #define SASS_PRELEXER_H
  
  #include <cstring>
  #include "lexer.hpp"
  
  namespace Sass {
    // using namespace Lexer;
    namespace Prelexer {
  
      //####################################
      // KEYWORD "REGEX" MATCHERS
      //####################################
  
      // Match Sass boolean keywords.
      const char* kwd_true(const char* src);
      const char* kwd_false(const char* src);
      const char* kwd_only(const char* src);
      const char* kwd_and(const char* src);
      const char* kwd_or(const char* src);
      const char* kwd_not(const char* src);
      const char* kwd_eq(const char* src);
      const char* kwd_neq(const char* src);
      const char* kwd_gt(const char* src);
      const char* kwd_gte(const char* src);
      const char* kwd_lt(const char* src);
      const char* kwd_lte(const char* src);
  
      // Match standard control chars
      const char* kwd_at(const char* src);
      const char* kwd_dot(const char* src);
      const char* kwd_comma(const char* src);
      const char* kwd_colon(const char* src);
      const char* kwd_slash(const char* src);
      const char* kwd_star(const char* src);
      const char* kwd_plus(const char* src);
      const char* kwd_minus(const char* src);
  
      //####################################
      // SPECIAL "REGEX" CONSTRUCTS
      //####################################
  
      // Match a sequence of characters delimited by the supplied chars.
      template <char beg, char end, bool esc>
      const char* delimited_by(const char* src) {
        src = exactly<beg>(src);
        if (!src) return 0;
        const char* stop;
        while (true) {
          if (!*src) return 0;
          stop = exactly<end>(src);
          if (stop && (!esc || *(src - 1) != '\\')) return stop;
          src = stop ? stop : src + 1;
        }
      }
  
      // skip to delimiter (mx) inside given range
      // this will savely skip over all quoted strings
      // recursive skip stuff delimited by start/stop
      // first start/opener must be consumed already!
      template<prelexer start, prelexer stop>
      const char* skip_over_scopes(const char* src, const char* end) {
  
        size_t level = 0;
        bool in_squote = false;
        bool in_dquote = false;
        // bool in_braces = false;
  
        while (*src) {
  
          // check for abort condition
          if (end && src >= end) break;
  
          // has escaped sequence?
          if (*src == '\\') {
            ++ src; // skip this (and next)
          }
          else if (*src == '"') {
            in_dquote = ! in_dquote;
          }
          else if (*src == '\'') {
            in_squote = ! in_squote;
          }
          else if (in_dquote || in_squote) {
            // take everything literally
          }
  
          // find another opener inside?
          else if (const char* pos = start(src)) {
            ++ level; // increase counter
            src = pos - 1; // advance position
          }
  
          // look for the closer (maybe final, maybe not)
          else if (const char* final = stop(src)) {
            // only close one level?
            if (level > 0) -- level;
            // return position at end of stop
            // delimiter may be multiple chars
            else return final;
            // advance position
            src = final - 1;
          }
  
          // next
          ++ src;
        }
  
        return 0;
      }
  
      // skip to a skip delimited by parentheses
      // uses smart `skip_over_scopes` internally
      const char* parenthese_scope(const char* src);
  
      // skip to delimiter (mx) inside given range
      // this will savely skip over all quoted strings
      // recursive skip stuff delimited by start/stop
      // first start/opener must be consumed already!
      template<prelexer start, prelexer stop>
      const char* skip_over_scopes(const char* src) {
        return skip_over_scopes<start, stop>(src, 0);
      }
  
      // Match a sequence of characters delimited by the supplied chars.
      template <prelexer start, prelexer stop>
      const char* recursive_scopes(const char* src) {
        // parse opener
        src = start(src);
        // abort if not found
        if (!src) return 0;
        // parse the rest until final closer
        return skip_over_scopes<start, stop>(src);
      }
  
      // Match a sequence of characters delimited by the supplied strings.
      template <const char* beg, const char* end, bool esc>
      const char* delimited_by(const char* src) {
        src = exactly<beg>(src);
        if (!src) return 0;
        const char* stop;
        while (true) {
          if (!*src) return 0;
          stop = exactly<end>(src);
          if (stop && (!esc || *(src - 1) != '\\')) return stop;
          src = stop ? stop : src + 1;
        }
      }
  
      // Tries to match a certain number of times (between the supplied interval).
      template<prelexer mx, size_t lo, size_t hi>
      const char* between(const char* src) {
        for (size_t i = 0; i < lo; ++i) {
          src = mx(src);
          if (!src) return 0;
        }
        for (size_t i = lo; i <= hi; ++i) {
          const char* new_src = mx(src);
          if (!new_src) return src;
          src = new_src;
        }
        return src;
      }
  
      // equivalent of STRING_REGULAR_EXPRESSIONS
      const char* re_string_double_open(const char* src);
      const char* re_string_double_close(const char* src);
      const char* re_string_single_open(const char* src);
      const char* re_string_single_close(const char* src);
      const char* re_string_uri_open(const char* src);
      const char* re_string_uri_close(const char* src);
  
      // Match a line comment.
      const char* line_comment(const char* src);
  
      // Match a block comment.
      const char* block_comment(const char* src);
      // Match either.
      const char* comment(const char* src);
      // Match double- and single-quoted strings.
      const char* double_quoted_string(const char* src);
      const char* single_quoted_string(const char* src);
      const char* quoted_string(const char* src);
      // Match interpolants.
      const char* interpolant(const char* src);
      // Match number prefix ([\+\-]+)
      const char* number_prefix(const char* src);
  
      // Match zero plus white-space or line_comments
      const char* optional_css_whitespace(const char* src);
      const char* css_whitespace(const char* src);
      // Match optional_css_whitepace plus block_comments
      const char* optional_css_comments(const char* src);
      const char* css_comments(const char* src);
  
      // Match one backslash escaped char
      const char* escape_seq(const char* src);
  
      // Match CSS css variables.
      const char* custom_property_name(const char* src);
      // Match a CSS identifier.
      const char* identifier(const char* src);
      const char* identifier_alpha(const char* src);
      const char* identifier_alnum(const char* src);
      const char* strict_identifier(const char* src);
      const char* strict_identifier_alpha(const char* src);
      const char* strict_identifier_alnum(const char* src);
      // Match a CSS unit identifier.
      const char* one_unit(const char* src);
      const char* multiple_units(const char* src);
      const char* unit_identifier(const char* src);
      // const char* strict_identifier_alnums(const char* src);
      // Match reference selector.
      const char* re_reference_combinator(const char* src);
      const char* static_reference_combinator(const char* src);
      const char* schema_reference_combinator(const char* src);
  
      // Match interpolant schemas
      const char* identifier_schema(const char* src);
      const char* value_schema(const char* src);
      const char* sass_value(const char* src);
      // const char* filename(const char* src);
      // const char* filename_schema(const char* src);
      // const char* url_schema(const char* src);
      // const char* url_value(const char* src);
      const char* vendor_prefix(const char* src);
  
      const char* re_special_directive(const char* src);
      const char* re_prefixed_directive(const char* src);
      const char* re_almost_any_value_token(const char* src);
  
      // Match CSS '@' keywords.
      const char* at_keyword(const char* src);
      const char* kwd_import(const char* src);
      const char* kwd_at_root(const char* src);
      const char* kwd_with_directive(const char* src);
      const char* kwd_without_directive(const char* src);
      const char* kwd_media(const char* src);
      const char* kwd_supports_directive(const char* src);
      // const char* keyframes(const char* src);
      // const char* keyf(const char* src);
      const char* kwd_mixin(const char* src);
      const char* kwd_function(const char* src);
      const char* kwd_return_directive(const char* src);
      const char* kwd_include_directive(const char* src);
      const char* kwd_content_directive(const char* src);
      const char* kwd_charset_directive(const char* src);
      const char* kwd_extend(const char* src);
  
      const char* unicode_seq(const char* src);
  
      const char* kwd_if_directive(const char* src);
      const char* kwd_else_directive(const char* src);
      const char* elseif_directive(const char* src);
  
      const char* kwd_for_directive(const char* src);
      const char* kwd_from(const char* src);
      const char* kwd_to(const char* src);
      const char* kwd_through(const char* src);
  
      const char* kwd_each_directive(const char* src);
      const char* kwd_in(const char* src);
  
      const char* kwd_while_directive(const char* src);
  
      const char* re_nothing(const char* src);
  
      const char* re_special_fun(const char* src);
  
      const char* kwd_warn(const char* src);
      const char* kwd_err(const char* src);
      const char* kwd_dbg(const char* src);
  
      const char* kwd_null(const char* src);
  
      const char* re_selector_list(const char* src);
      const char* re_type_selector(const char* src);
      const char* re_static_expression(const char* src);
  
      // identifier that can start with hyphens
      const char* css_identifier(const char* src);
      const char* css_ip_identifier(const char* src);
  
      // Match CSS type selectors
      const char* namespace_schema(const char* src);
      const char* namespace_prefix(const char* src);
      const char* type_selector(const char* src);
      const char* hyphens_and_identifier(const char* src);
      const char* hyphens_and_name(const char* src);
      const char* universal(const char* src);
      // Match CSS id names.
      const char* id_name(const char* src);
      // Match CSS class names.
      const char* class_name(const char* src);
      // Attribute name in an attribute selector
      const char* attribute_name(const char* src);
      // Match placeholder selectors.
      const char* placeholder(const char* src);
      // Match CSS numeric constants.
      const char* op(const char* src);
      const char* sign(const char* src);
      const char* unsigned_number(const char* src);
      const char* number(const char* src);
      const char* coefficient(const char* src);
      const char* binomial(const char* src);
      const char* percentage(const char* src);
      const char* ampersand(const char* src);
      const char* dimension(const char* src);
      const char* hex(const char* src);
      const char* hexa(const char* src);
      const char* hex0(const char* src);
      // const char* rgb_prefix(const char* src);
      // Match CSS uri specifiers.
      const char* uri_prefix(const char* src);
      // Match CSS "!important" keyword.
      const char* kwd_important(const char* src);
      // Match CSS "!optional" keyword.
      const char* kwd_optional(const char* src);
      // Match Sass "!default" keyword.
      const char* default_flag(const char* src);
      const char* global_flag(const char* src);
      // Match CSS pseudo-class/element prefixes
      const char* pseudo_prefix(const char* src);
      // Match CSS function call openers.
      const char* re_functional(const char* src);
      const char* re_pseudo_selector(const char* src);
      const char* functional_schema(const char* src);
      const char* pseudo_not(const char* src);
      // Match CSS 'odd' and 'even' keywords for functional pseudo-classes.
      const char* even(const char* src);
      const char* odd(const char* src);
      // Match CSS attribute-matching operators.
      const char* exact_match(const char* src);
      const char* class_match(const char* src);
      const char* dash_match(const char* src);
      const char* prefix_match(const char* src);
      const char* suffix_match(const char* src);
      const char* substring_match(const char* src);
      // Match CSS combinators.
      // const char* adjacent_to(const char* src);
      // const char* precedes(const char* src);
      // const char* parent_of(const char* src);
      // const char* ancestor_of(const char* src);
  
      // Match SCSS variable names.
      const char* variable(const char* src);
      const char* calc_fn_call(const char* src);
  
      // IE stuff
      const char* ie_progid(const char* src);
      const char* ie_expression(const char* src);
      const char* ie_property(const char* src);
      const char* ie_keyword_arg(const char* src);
      const char* ie_keyword_arg_value(const char* src);
      const char* ie_keyword_arg_property(const char* src);
  
      // characters that terminate parsing of a list
      const char* list_terminator(const char* src);
      const char* space_list_terminator(const char* src);
  
      // match url()
      const char* H(const char* src);
      const char* W(const char* src);
      // `UNICODE` makes VS sad
      const char* UUNICODE(const char* src);
      const char* NONASCII(const char* src);
      const char* ESCAPE(const char* src);
      const char* real_uri(const char* src);
      const char* real_uri_suffix(const char* src);
      // const char* real_uri_prefix(const char* src);
      const char* real_uri_value(const char* src);
  
      // Path matching functions.
      // const char* folder(const char* src);
      // const char* folders(const char* src);
  
  
      const char* static_string(const char* src);
      const char* static_component(const char* src);
      const char* static_property(const char* src);
      const char* static_value(const char* src);
  
      const char* css_variable_value(const char* src);
      const char* css_variable_top_level_value(const char* src);
  
      // Utility functions for finding and counting characters in a string.
      template<char c>
      const char* find_first(const char* src) {
        while (*src && *src != c) ++src;
        return *src ? src : 0;
      }
      template<prelexer mx>
      const char* find_first(const char* src) {
        while (*src && !mx(src)) ++src;
        return *src ? src : 0;
      }
      template<prelexer mx>
      const char* find_first_in_interval(const char* beg, const char* end) {
        bool esc = false;
        while ((beg < end) && *beg) {
          if (esc) esc = false;
          else if (*beg == '\\') esc = true;
          else if (mx(beg)) return beg;
          ++beg;
        }
        return 0;
      }
      template<prelexer mx, prelexer skip>
      const char* find_first_in_interval(const char* beg, const char* end) {
        bool esc = false;
        while ((beg < end) && *beg) {
          if (esc) esc = false;
          else if (*beg == '\\') esc = true;
          else if (const char* pos = skip(beg)) beg = pos;
          else if (mx(beg)) return beg;
          ++beg;
        }
        return 0;
      }
      template <prelexer mx>
      unsigned int count_interval(const char* beg, const char* end) {
        unsigned int counter = 0;
        bool esc = false;
        while (beg < end && *beg) {
          const char* p;
          if (esc) {
            esc = false;
            ++beg;
          } else if (*beg == '\\') {
            esc = true;
            ++beg;
          } else if ((p = mx(beg))) {
            ++counter;
            beg = p;
          }
          else {
            ++beg;
          }
        }
        return counter;
      }
  
      template <size_t size, prelexer mx, prelexer pad>
      const char* padded_token(const char* src)
      {
        size_t got = 0;
        const char* pos = src;
        while (got < size) {
          if (!mx(pos)) break;
          ++ pos; ++ got;
        }
        while (got < size) {
          if (!pad(pos)) break;
          ++ pos; ++ got;
        }
        return got ? pos : 0;
      }
  
      template <size_t min, size_t max, prelexer mx>
      const char* minmax_range(const char* src)
      {
        size_t got = 0;
        const char* pos = src;
        while (got < max) {
          if (!mx(pos)) break;
          ++ pos; ++ got;
        }
        if (got < min) return 0;
        if (got > max) return 0;
        return pos;
      }
  
      template <char min, char max>
      const char* char_range(const char* src)
      {
        if (*src < min) return 0;
        if (*src > max) return 0;
        return src + 1;
      }
  
    }
  }
  
  #endif
  