# coding: ASCII-8BIT
module Net::IRC::PATTERN # :nodoc:
  # letter     =  %x41-5A / %x61-7A       ; A-Z / a-z
  # digit      =  %x30-39                 ; 0-9
  # hexdigit   =  digit / "A" / "B" / "C" / "D" / "E" / "F"
  # special    =  %x5B-60 / %x7B-7D
  #                  ; "[", "]", "\", "`", "_", "^", "{", "|", "}"
  LETTER   = 'A-Za-z'
  DIGIT    = '0-9'
  HEXDIGIT = "#{DIGIT}A-Fa-f"
  SPECIAL  = '\x5B-\x60\x7B-\x7D'

  # shortname  =  ( letter / digit ) *( letter / digit / "-" )
  #               *( letter / digit )
  #                 ; as specified in RFC 1123 [HNAME]
  # hostname   =  shortname *( "." shortname )
  SHORTNAME = "[#{LETTER}#{DIGIT}](?:[-#{LETTER}#{DIGIT}]*[#{LETTER}#{DIGIT}])?"
  HOSTNAME  = "#{SHORTNAME}(?:\\.#{SHORTNAME})*"

  # servername =  hostname
  SERVERNAME = HOSTNAME

  # nickname   =  ( letter / special ) *8( letter / digit / special / "-" )
  #NICKNAME = "[#{LETTER}#{SPECIAL}#{DIGIT}_][-#{LETTER}#{DIGIT}#{SPECIAL}]*"
  NICKNAME = "\\S+" # for multibytes

  # user       =  1*( %x01-09 / %x0B-0C / %x0E-1F / %x21-3F / %x41-FF )
  #                 ; any octet except NUL, CR, LF, " " and "@"
  USER = '[\x01-\x09\x0B-\x0C\x0E-\x1F\x21-\x3F\x41-\xFF]+'

  # ip4addr    =  1*3digit "." 1*3digit "." 1*3digit "." 1*3digit
  IP4ADDR = "[#{DIGIT}]{1,3}(?:\\.[#{DIGIT}]{1,3}){3}"
  # ip6addr    =  1*hexdigit 7( ":" 1*hexdigit )
  # ip6addr    =/ "0:0:0:0:0:" ( "0" / "FFFF" ) ":" ip4addr
  IP6ADDR = "(?:[#{HEXDIGIT}]+(?::[#{HEXDIGIT}]+){7}|0:0:0:0:0:(?:0|FFFF):#{IP4ADDR})"
  # hostaddr   =  ip4addr / ip6addr
  HOSTADDR = "(?:#{IP4ADDR}|#{IP6ADDR})"

  # host       =  hostname / hostaddr
  HOST = "(?:#{HOSTNAME}|#{HOSTADDR})"

  # prefix     =  servername / ( nickname [ [ "!" user ] "@" host ] )
  PREFIX = "(?:#{NICKNAME}(?:(?:!#{USER})?@#{HOST})?|#{SERVERNAME})"

  # nospcrlfcl =  %x01-09 / %x0B-0C / %x0E-1F / %x21-39 / %x3B-FF
  #                 ; any octet except NUL, CR, LF, " " and ":"
  NOSPCRLFCL = '\x01-\x09\x0B-\x0C\x0E-\x1F\x21-\x39\x3B-\xFF'

  # command    =  1*letter / 3digit
  COMMAND = "(?:[#{LETTER}]+|[#{DIGIT}]{3})"

  # SPACE      =  %x20        ; space character
  # middle     =  nospcrlfcl *( ":" / nospcrlfcl )
  # trailing   =  *( ":" / " " / nospcrlfcl )
  # params     =  *14( SPACE middle ) [ SPACE ":" trailing ]
  #            =/ 14( SPACE middle ) [ SPACE [ ":" ] trailing ]
  MIDDLE = "[#{NOSPCRLFCL}][:#{NOSPCRLFCL}]*"
  TRAILING = "[: #{NOSPCRLFCL}]*"
  PARAMS = "(?:((?: #{MIDDLE}){0,14})(?: :(#{TRAILING}))?|((?: #{MIDDLE}){14}):?(#{TRAILING}))"

  # crlf       =  %x0D %x0A   ; "carriage return" "linefeed"
  # message    =  [ ":" prefix SPACE ] command [ params ] crlf
  CRLF = '\x0D\x0A'
  MESSAGE = "(?::(#{PREFIX}) )?(#{COMMAND})#{PARAMS}\s*#{CRLF}"

  CLIENT_PATTERN  = /\A#{NICKNAME}(?:(?:!#{USER})?@#{HOST})\z/on
  MESSAGE_PATTERN = /\A#{MESSAGE}\z/on
end # PATTERN