URI::RFC2396_Parser#initialize_pattern

# File tmp/rubies/ruby-4.1.0-preview1/lib/uri/rfc2396_parser.rb, line 337
def initialize_pattern(opts = {})
  ret = {}
  ret[:ESCAPED] = escaped = (opts.delete(:ESCAPED) || PATTERN::ESCAPED)
  ret[:UNRESERVED] = unreserved = opts.delete(:UNRESERVED) || PATTERN::UNRESERVED
  ret[:RESERVED] = reserved = opts.delete(:RESERVED) || PATTERN::RESERVED
  ret[:DOMLABEL] = opts.delete(:DOMLABEL) || PATTERN::DOMLABEL
  ret[:TOPLABEL] = opts.delete(:TOPLABEL) || PATTERN::TOPLABEL
  ret[:HOSTNAME] = hostname = opts.delete(:HOSTNAME)

  # RFC 2396 (URI Generic Syntax)
  # RFC 2732 (IPv6 Literal Addresses in URL's)
  # RFC 2373 (IPv6 Addressing Architecture)

  # uric          = reserved | unreserved | escaped
  ret[:URIC] = uric = "(?:[#{unreserved}#{reserved}]|#{escaped})"
  # uric_no_slash = unreserved | escaped | ";" | "?" | ":" | "@" |
  #                 "&" | "=" | "+" | "$" | ","
  ret[:URIC_NO_SLASH] = uric_no_slash = "(?:[#{unreserved};?:@&=+$,]|#{escaped})"
  # query         = *uric
  ret[:QUERY] = query = "#{uric}*"
  # fragment      = *uric
  ret[:FRAGMENT] = fragment = "#{uric}*"

  # hostname      = *( domainlabel "." ) toplabel [ "." ]
  # reg-name      = *( unreserved / pct-encoded / sub-delims ) # RFC3986
  unless hostname
    ret[:HOSTNAME] = hostname = "(?:[a-zA-Z0-9\\-.]|%\\h\\h)+"
  end

  # RFC 2373, APPENDIX B:
  # IPv6address = hexpart [ ":" IPv4address ]
  # IPv4address   = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
  # hexpart = hexseq | hexseq "::" [ hexseq ] | "::" [ hexseq ]
  # hexseq  = hex4 *( ":" hex4)
  # hex4    = 1*4HEXDIG
  #
  # XXX: This definition has a flaw. "::" + IPv4address must be
  # allowed too.  Here is a replacement.
  #
  # IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
  ret[:IPV4ADDR] = ipv4addr = "\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}"
  # hex4     = 1*4HEXDIG
  hex4 = "[#{PATTERN::HEX}]{1,4}"
  # lastpart = hex4 | IPv4address
  lastpart = "(?:#{hex4}|#{ipv4addr})"
  # hexseq1  = *( hex4 ":" ) hex4
  hexseq1 = "(?:#{hex4}:)*#{hex4}"
  # hexseq2  = *( hex4 ":" ) lastpart
  hexseq2 = "(?:#{hex4}:)*#{lastpart}"
  # IPv6address = hexseq2 | [ hexseq1 ] "::" [ hexseq2 ]
  ret[:IPV6ADDR] = ipv6addr = "(?:#{hexseq2}|(?:#{hexseq1})?::(?:#{hexseq2})?)"

  # IPv6prefix  = ( hexseq1 | [ hexseq1 ] "::" [ hexseq1 ] ) "/" 1*2DIGIT
  # unused

  # ipv6reference = "[" IPv6address "]" (RFC 2732)
  ret[:IPV6REF] = ipv6ref = "\\[#{ipv6addr}\\]"

  # host          = hostname | IPv4address
  # host          = hostname | IPv4address | IPv6reference (RFC 2732)
  ret[:HOST] = host = "(?:#{hostname}|#{ipv4addr}|#{ipv6ref})"
  # port          = *digit
  ret[:PORT] = port = '\d*'
  # hostport      = host [ ":" port ]
  ret[:HOSTPORT] = hostport = "#{host}(?::#{port})?"

  # userinfo      = *( unreserved | escaped |
  #                    ";" | ":" | "&" | "=" | "+" | "$" | "," )
  ret[:USERINFO] = userinfo = "(?:[#{unreserved};:&=+$,]|#{escaped})*"

  # pchar         = unreserved | escaped |
  #                 ":" | "@" | "&" | "=" | "+" | "$" | ","
  pchar = "(?:[#{unreserved}:@&=+$,]|#{escaped})"
  # param         = *pchar
  param = "#{pchar}*"
  # segment       = *pchar *( ";" param )
  segment = "#{pchar}*(?:;#{param})*"
  # path_segments = segment *( "/" segment )
  ret[:PATH_SEGMENTS] = path_segments = "#{segment}(?:/#{segment})*"

  # server        = [ [ userinfo "@" ] hostport ]
  server = "(?:#{userinfo}@)?#{hostport}"
  # reg_name      = 1*( unreserved | escaped | "$" | "," |
  #                     ";" | ":" | "@" | "&" | "=" | "+" )
  ret[:REG_NAME] = reg_name = "(?:[#{unreserved}$,;:@&=+]|#{escaped})+"
  # authority     = server | reg_name
  authority = "(?:#{server}|#{reg_name})"

  # rel_segment   = 1*( unreserved | escaped |
  #                     ";" | "@" | "&" | "=" | "+" | "$" | "," )
  ret[:REL_SEGMENT] = rel_segment = "(?:[#{unreserved};@&=+$,]|#{escaped})+"

  # scheme        = alpha *( alpha | digit | "+" | "-" | "." )
  ret[:SCHEME] = scheme = "[#{PATTERN::ALPHA}][\\-+.#{PATTERN::ALPHA}\\d]*"

  # abs_path      = "/"  path_segments
  ret[:ABS_PATH] = abs_path = "/#{path_segments}"
  # rel_path      = rel_segment [ abs_path ]
  ret[:REL_PATH] = rel_path = "#{rel_segment}(?:#{abs_path})?"
  # net_path      = "//" authority [ abs_path ]
  ret[:NET_PATH] = net_path = "//#{authority}(?:#{abs_path})?"

  # hier_part     = ( net_path | abs_path ) [ "?" query ]
  ret[:HIER_PART] = hier_part = "(?:#{net_path}|#{abs_path})(?:\\?(?:#{query}))?"
  # opaque_part   = uric_no_slash *uric
  ret[:OPAQUE_PART] = opaque_part = "#{uric_no_slash}#{uric}*"

  # absoluteURI   = scheme ":" ( hier_part | opaque_part )
  ret[:ABS_URI] = abs_uri = "#{scheme}:(?:#{hier_part}|#{opaque_part})"
  # relativeURI   = ( net_path | abs_path | rel_path ) [ "?" query ]
  ret[:REL_URI] = rel_uri = "(?:#{net_path}|#{abs_path}|#{rel_path})(?:\\?#{query})?"

  # URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]
  ret[:URI_REF] = "(?:#{abs_uri}|#{rel_uri})?(?:##{fragment})?"

  ret[:X_ABS_URI] = "
    (#{scheme}):                           (?# 1: scheme)
    (?:
       (#{opaque_part})                    (?# 2: opaque)
    |
       (?:(?:
         //(?:
             (?:(?:(#{userinfo})@)?        (?# 3: userinfo)
               (?:(#{host})(?::(\\d*))?))? (?# 4: host, 5: port)
           |
             (#{reg_name})                 (?# 6: registry)
           )
         |
         (?!//))                           (?# XXX: '//' is the mark for hostport)
         (#{abs_path})?                    (?# 7: path)
       )(?:\\?(#{query}))?                 (?# 8: query)
    )
    (?:\\#(#{fragment}))?                  (?# 9: fragment)
  "

  ret[:X_REL_URI] = "
    (?:
      (?:
        //
        (?:
          (?:(#{userinfo})@)?       (?# 1: userinfo)
            (#{host})?(?::(\\d*))?  (?# 2: host, 3: port)
        |
          (#{reg_name})             (?# 4: registry)
        )
      )
    |
      (#{rel_segment})              (?# 5: rel_segment)
    )?
    (#{abs_path})?                  (?# 6: abs_path)
    (?:\\?(#{query}))?              (?# 7: query)
    (?:\\#(#{fragment}))?           (?# 8: fragment)
  "

  ret
end