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=begin

= net/imap.rb

Copyright (C) 2000  Shugo Maeda <shugo@ruby-lang.org>

This library is distributed under the terms of the Ruby license.
You can freely distribute/modify this library.

== class Net::IMAP

Net::IMAP implements Internet Message Access Protocol (IMAP) clients.

=== Super Class

Object

=== Class Methods

: new(host, port = 143)
      Creates a new Net::IMAP object and connects it to the specified
      port on the named host.

: debug
      Returns the debug mode

: debug = val
      Sets the debug mode

: add_authenticator(auth_type, authenticator)
      Adds an authenticator for Net::IMAP#authenticate.

=== Methods

: greeting
      Returns an initial greeting response from the server.

: responses
      Returns recorded untagged responses.

      ex).
        imap.select("inbox")
        p imap.responses["EXISTS"][-1]
        #=> 2
        p imap.responses["UIDVALIDITY"][-1]
        #=> 968263756

: disconnect
      Disconnects from the server.

: capability
      Sends a CAPABILITY command, and returns a listing of
      capabilities that the server supports.

: noop
      Sends a NOOP command to the server. It does nothing.

: logout
      Sends a LOGOUT command to inform the server that the client is
      done with the connection.

: authenticate(auth_type, arg...)
      Sends an AUTEHNTICATE command to authenticate the client.
      The auth_type parameter is a string that represents
      the authentication mechanism to be used. Currently Net::IMAP
      supports "LOGIN" and "CRAM-MD5" for the auth_type.

      ex).
        imap.authenticate('LOGIN', user, password)

: login(user, password)
      Sends a LOGIN command to identify the client and carries
      the plaintext password authenticating this user.

: select(mailbox)
      Sends a SELECT command to select a mailbox so that messages
      in the mailbox can be accessed.

: examine(mailbox)
      Sends a EXAMINE command to select a mailbox so that messages
      in the mailbox can be accessed. However, the selected mailbox
      is identified as read-only.

: create(mailbox)
      Sends a CREATE command to create a new mailbox.

: delete(mailbox)
      Sends a DELETE command to remove the mailbox.

: rename(mailbox, newname)
      Sends a RENAME command to change the name of the mailbox to
      the newname.

: subscribe(mailbox)
      Sends a SUBSCRIBE command to add the specified mailbox name to
      the server's set of "active" or "subscribed" mailboxes.

: unsubscribe(mailbox)
      Sends a UNSUBSCRIBE command to remove the specified mailbox name
      from the server's set of "active" or "subscribed" mailboxes.

: list(refname, mailbox)
      Sends a LIST command, and returns a subset of names from
      the complete set of all names available to the client.

      ex).
        imap.create("foo/bar")
        imap.create("foo/baz")
        p imap.list("", "foo/%")
        #=> [#<Net::IMAP::MailboxList attr=[:NoSelect], delim="/", name="foo/">, #<Net::IMAP::MailboxList attr=[:NoInferiors, :Marked], delim="/", name="foo/bar">, #<Net::IMAP::MailboxList attr=[:NoInferiors], delim="/", name="foo/baz">]

: lsub(refname, mailbox)
      Sends a LSUB command, and returns a subset of names from the set
      of names that the user has declared as being "active" or
      "subscribed".

: status(mailbox, attr)
      Sends a STATUS command, and returns the status of the indicated
      mailbox.

      ex).
        p imap.status("inbox", ["MESSAGES", "RECENT"])
        #=> {"RECENT"=>0, "MESSAGES"=>44}

: append(mailbox, message, flags = nil, date_time = nil)
      Sends a APPEND command to append the message to the end of
      the mailbox.

      ex).
        imap.append("inbox", <<EOF.gsub(/\n/, "\r\n"), [:Seen], Time.now)
        Subject: hello
        From: shugo@ruby-lang.org
        To: shugo@ruby-lang.org
        
        hello world
        EOF

: check
      Sends a CHECK command to request a checkpoint of the currently
      selected mailbox.

: close
      Sends a CLOSE command to close the currently selected mailbox.
      The CLOSE command permanently removes from the mailbox all
      messages that have the \Deleted flag set.

: expunge
      Sends a EXPUNGE command to permanently remove from the currently
      selected mailbox all messages that have the \Deleted flag set.

: search(keys, charset = nil)
: uid_search(keys, charset = nil)
      Sends a SEARCH command to search the mailbox for messages that
      match the given searching criteria, and returns message sequence
      numbers (search) or unique identifiers (uid_search).

      ex).
        p imap.search(["SUBJECT", "hello"])
        #=> [1, 6, 7, 8]
        p imap.search('SUBJECT "hello"')
        #=> [1, 6, 7, 8]

: fetch(set, attr)
: uid_fetch(set, attr)
      Sends a FETCH command to retrieve data associated with a message
      in the mailbox. the set parameter is a number or an array of
      numbers or a Range object. the number is a message sequence
      number (fetch) or a unique identifier (uid_fetch).

      ex).
        p imap.fetch(6..8, "UID")
        #=> [#<Net::IMAP::FetchData seqno=6, attr={"UID"=>98}>, #<Net::IMAP::FetchData seqno=7, attr={"UID"=>99}>, #<Net::IMAP::FetchData seqno=8, attr={"UID"=>100}>]
        p imap.fetch(6, "BODY[HEADER.FIELDS (SUBJECT)]")
        #=> [#<Net::IMAP::FetchData seqno=6, attr={"BODY[HEADER.FIELDS (SUBJECT)]"=>"Subject: test\r\n\r\n"}>]
        data = imap.uid_fetch(98, ["RFC822.SIZE", "INTERNALDATE"])[0]
        p data.seqno
        #=> 6
        p data.attr["RFC822.SIZE"]
        #=> 611
        p data.attr["INTERNALDATE"]
        #=> "12-Oct-2000 22:40:59 +0900"
        p data.attr["UID"]
        #=> 98

: store(set, attr, flags)
: uid_store(set, attr, flags)
      Sends a STORE command to alter data associated with a message
      in the mailbox. the set parameter is a number or an array of
      numbers or a Range object. the number is a message sequence
      number (store) or a unique identifier (uid_store).

      ex).
        p imap.store(6..8, "+FLAGS", [:Deleted])
        #=> [#<Net::IMAP::FetchData seqno=6, attr={"FLAGS"=>[:Seen, :Deleted]}>, #<Net::IMAP::FetchData seqno=7, attr={"FLAGS"=>[:Seen, :Deleted]}>, #<Net::IMAP::FetchData seqno=8, attr={"FLAGS"=>[:Seen, :Deleted]}>]

: copy(set, mailbox)
: uid_copy(set, mailbox)
      Sends a COPY command to copy the specified message(s) to the end
      of the specified destination mailbox. the set parameter is
      a number or an array of numbers or a Range object. the number is
      a message sequence number (copy) or a unique identifier (uid_copy).

: sort(sort_keys, search_keys, charset)
: uid_sort(sort_keys, search_keys, charset)
      Sends a SORT command to sort messages in the mailbox.

      ex).
        p imap.sort(["FROM"], ["ALL"], "US-ASCII")
        #=> [1, 2, 3, 5, 6, 7, 8, 4, 9]
        p imap.sort(["DATE"], ["SUBJECT", "hello"], "US-ASCII")
        #=> [6, 7, 8, 1]

=end

require "socket"
require "md5"

module Net
  class IMAP
    attr_reader :greeting, :responses

    def self.debug
      return @@debug
    end

    def self.debug=(val)
      return @@debug = val
    end

    def self.add_authenticator(auth_type, authenticator)
      @@authenticators[auth_type] = authenticator
    end

    def disconnect
      @sock.close
    end

    def capability
      send_command("CAPABILITY")
      return @responses.delete("CAPABILITY")[-1]
    end

    def noop
      send_command("NOOP")
    end

    def logout
      send_command("LOGOUT")
    end

    def authenticate(auth_type, *args)
      auth_type = auth_type.upcase
      unless @@authenticators.has_key?(auth_type)
	raise ArgumentError,
	  format('unknown auth type - "%s"', auth_type)
      end
      authenticator = @@authenticators[auth_type].new(*args)
      send_command("AUTHENTICATE", auth_type) do |resp|
	if resp.instance_of?(ContinueRequest)
	  data = authenticator.process(resp.data.text.unpack("m")[0])
	  send_data([data].pack("m").chomp)
	end
      end
    end

    def login(user, password)
      send_command("LOGIN", user, password)
    end

    def select(mailbox)
      @responses.clear
      send_command("SELECT", mailbox)
    end

    def examine(mailbox)
      @responses.clear
      send_command("EXAMINE", mailbox)
    end

    def create(mailbox)
      send_command("CREATE", mailbox)
    end

    def delete(mailbox)
      send_command("DELETE", mailbox)
    end

    def rename(mailbox, newname)
      send_command("RENAME", mailbox, newname)
    end

    def subscribe(mailbox)
      send_command("SUBSCRIBE", mailbox)
    end

    def unsubscribe(mailbox)
      send_command("UNSUBSCRIBE", mailbox)
    end

    def list(refname, mailbox)
      send_command("LIST", refname, mailbox)
      return @responses.delete("LIST")
    end

    def lsub(refname, mailbox)
      send_command("LSUB", refname, mailbox)
      return @responses.delete("LSUB")
    end

    def status(mailbox, attr)
      send_command("STATUS", mailbox, attr)
      return @responses.delete("STATUS")[-1][1]
    end

    def append(mailbox, message, flags = nil, date_time = nil)
      args = []
      if flags
	args.push(flags)
      end
      args.push(date_time) if date_time
      args.push(Literal.new(message))
      send_command("APPEND", mailbox, *args)
    end

    def check
      send_command("CHECK")
    end

    def close
      send_command("CLOSE")
    end

    def expunge
      send_command("EXPUNGE")
      return @responses.delete("EXPUNGE")
    end

    def search(keys, charset = nil)
      return search_internal("SEARCH", keys, charset)
    end

    def uid_search(keys, charset = nil)
      return search_internal("UID SEARCH", keys, charset)
    end

    def fetch(set, attr)
      return fetch_internal("FETCH", set, attr)
    end

    def uid_fetch(set, attr)
      return fetch_internal("UID FETCH", set, attr)
    end

    def store(set, attr, flags)
      return store_internal("STORE", set, attr, flags)
    end

    def uid_store(set, attr, flags)
      return store_internal("UID STORE", set, attr, flags)
    end

    def copy(set, mailbox)
      copy_internal("COPY", set, mailbox)
    end

    def uid_copy(set, mailbox)
      copy_internal("UID COPY", set, mailbox)
    end

    def sort(sort_keys, search_keys, charset)
      return sort_internal("SORT", sort_keys, search_keys, charset)
    end

    def uid_sort(sort_keys, search_keys, charset)
      return sort_internal("UID SORT", sort_keys, search_keys, charset)
    end

    private

    CRLF = "\r\n"
    PORT = 143

    @@debug = false
    @@authenticators = {}

    def initialize(host, port = PORT)
      @host = host
      @port = port
      @tag_prefix = "RUBY"
      @tagno = 0
      @parser = ResponseParser.new
      @sock = TCPSocket.open(host, port)
      @responses = Hash.new([].freeze)
      @greeting = get_response
      if /\ABYE\z/ni =~ @greeting.name
	@sock.close
	raise ByeResponseError, resp[0]
      end
    end

    def send_command(cmd, *args, &block)
      tag = generate_tag
      data = args.collect {|i| format_data(i)}.join(" ")
      if data.length > 0
	put_line(tag + " " + cmd + " " + data)
      else
	put_line(tag + " " + cmd)
      end
      return get_all_responses(tag, cmd, &block)
    end

    def generate_tag
      @tagno += 1
      return format("%s%04d", @tag_prefix, @tagno)
    end

    def send_data(*args)
      data = args.collect {|i| format_data(i)}.join(" ")
      put_line(data)
    end

    def put_line(line)
      line = line + CRLF
      @sock.print(line)
      if @@debug
        $stderr.print(line.gsub(/^/n, "C: "))
      end
    end

    def get_all_responses(tag, cmd, &block)
      while resp = get_response
	if @@debug
	  $stderr.printf("R: %s\n", resp.inspect)
	end
	case resp
	when TaggedResponse
	  case resp.name
	  when /\A(?:NO)\z/ni
	    raise NoResponseError, resp.data.text
	  when /\A(?:BAD)\z/ni
	    raise BadResponseError, resp.data.text
	  else
	    return resp
	  end
	when UntaggedResponse
	  if /\ABYE\z/ni =~ resp.name &&
	      cmd != "LOGOUT"
	    raise ByeResponseError, resp.data.text
	  end
	  record_response(resp.name, resp.data)
	  if resp.data.instance_of?(ResponseText) &&
	      (code = resp.data.code)
	    record_response(code.name, code.data)
	  end
	end
	block.call(resp) if block
      end
    end

    def get_response
      buff = ""
      while true
	s = @sock.gets(CRLF)
	break unless s
	buff.concat(s)
	if /\{(\d+)\}\r\n/n =~ s
	  s = @sock.read($1.to_i)
	  buff.concat(s)
	else
	  break
	end
      end
      return nil if buff.length == 0
      if @@debug
        $stderr.print(buff.gsub(/^/n, "S: "))
      end
      return @parser.parse(buff)
    end

    def record_response(name, data)
      unless @responses.has_key?(name)
	@responses[name] = []
      end
      @responses[name].push(data)
    end

    def format_data(data)
      case data
      when nil
	return "NIL"
      when String
	return format_string(data)
      when Integer
	return format_number(data)
      when Array
	return format_list(data)
      when Time
	return format_time(data)
      when Symbol
	return format_symbol(data)
      else
	return data.format_data
      end
    end

    def format_string(str)
      case str
      when ""
	return '""'
      when /[\x80-\xff\r\n]/n
	# literal
	return "{" + str.length.to_s + "}" + CRLF + str
      when /[(){ \x00-\x1f\x7f%*"\\]/n
	# quoted string
	return '"' + str.gsub(/["\\]/n, "\\\\\\&") + '"'
      else
	# atom
	return str
      end
    end

    def format_number(num)
      if num < 0 || num >= 4294967296
	raise DataFormatError, num.to_s
      end
      return num.to_s
    end

    def format_list(list)
      contents = list.collect {|i| format_data(i)}.join(" ")
      return "(" + contents + ")"
    end

    DATE_MONTH = %w(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)

    def format_time(time)
      t = time.dup.gmtime
      return format('"%2d-%3s-%4d %02d:%02d:%02d +0000"',
		    t.day, DATE_MONTH[t.month - 1], t.year,
		    t.hour, t.min, t.sec)
    end

    def format_symbol(symbol)
      return "\\" + symbol.to_s
    end

    def search_internal(cmd, keys, charset)
      if keys.instance_of?(String)
	keys = [RawData.new(keys)]
      else
	normalize_searching_criteria(keys)
      end
      if charset
	send_command(cmd, "CHARSET", charset, *keys)
      else
	send_command(cmd, *keys)
      end
      return @responses.delete("SEARCH")[-1]
    end

    def fetch_internal(cmd, set, attr)
      if attr.instance_of?(String)
	attr = RawData.new(attr)
      end
      @responses.delete("FETCH")
      send_command(cmd, MessageSet.new(set), attr)
      return @responses.delete("FETCH")
    end

    def store_internal(cmd, set, attr, flags)
      if attr.instance_of?(String)
	attr = RawData.new(attr)
      end
      @responses.delete("FETCH")
      send_command(cmd, MessageSet.new(set), attr, flags)
      return @responses.delete("FETCH")
    end

    def copy_internal(cmd, set, mailbox)
      send_command(cmd, MessageSet.new(set), mailbox)
    end

    def sort_internal(cmd, sort_keys, search_keys, charset)
      if search_keys.instance_of?(String)
	search_keys = [RawData.new(search_keys)]
      else
	normalize_searching_criteria(search_keys)
      end
      normalize_searching_criteria(search_keys)
      send_command(cmd, sort_keys, charset, *search_keys)
      return @responses.delete("SORT")[-1]
    end

    def normalize_searching_criteria(keys)
      keys.collect! do |i|
	case i
	when -1, Range, Array
	  MessageSet.new(i)
	else
	  i
	end
      end
    end

    class RawData
      def format_data
	return @data
      end

      private

      def initialize(data)
	@data = data
      end
    end

    class Atom
      def format_data
	return @data
      end

      private

      def initialize(data)
	@data = data
      end
    end

    class QuotedString
      def format_data
	return '"' + @data.gsub(/["\\]/n, "\\\\\\&") + '"'
      end

      private

      def initialize(data)
	@data = data
      end
    end

    class Literal
      def format_data
	return "{" + @data.length.to_s + "}" + CRLF + @data
      end

      private

      def initialize(data)
	@data = data
      end
    end

    class MessageSet
      def format_data
	return format_internal(@data)
      end

      private

      def initialize(data)
	@data = data
      end

      def format_internal(data)
	case data
	when "*"
	  return data
	when Integer
	  ensure_nz_number(data)
	  if data == -1
	    return "*"
	  else
	    return data.to_s
	  end
	when Range
	  return format_internal(data.first) +
	    ":" + format_internal(data.last)
	when Array
	  return data.collect {|i| format_internal(i)}.join(",")
	else
	  raise DataFormatError, data.inspect
	end
      end

      def ensure_nz_number(num)
	if num < -1 || num == 0 || num >= 4294967296
	  raise DataFormatError, num.inspect
	end
      end
    end

    ContinueRequest = Struct.new(:data, :raw_data)
    UntaggedResponse = Struct.new(:name, :data, :raw_data)
    TaggedResponse = Struct.new(:tag, :name, :data, :raw_data)
    ResponseText = Struct.new(:code, :text)
    ResponseCode = Struct.new(:name, :data)
    MailboxList = Struct.new(:attr, :delim, :name)
    StatusData = Struct.new(:mailbox, :attr)
    FetchData = Struct.new(:seqno, :attr)
    Envelope = Struct.new(:date, :subject, :from, :sender, :reply_to,
			  :to, :cc, :bcc, :in_reply_to, :message_id)
    Address = Struct.new(:name, :route, :mailbox, :host)
    ContentDisposition = Struct.new(:dsp_type, :param)

    class BodyTypeBasic < Struct.new(:media_type, :media_subtype,
				     :param, :content_id,
				     :description, :encoding, :size,
				     :md5, :disposition, :language,
				     :extension)
      def multipart?
	return false
      end
    end

    class BodyTypeText < Struct.new(:media_type, :media_subtype,
				    :param, :content_id,
				    :description, :encoding, :size,
				    :lines,
				    :md5, :disposition, :language,
				    :extension)
      def multipart?
	return false
      end
    end

    class BodyTypeMessage < Struct.new(:media_type, :media_subtype,
				       :param, :content_id,
				       :description, :encoding, :size,
				       :envelope, :body, :lines,
				       :md5, :disposition, :language,
				       :extension)
      def multipart?
	return false
      end
    end

    class BodyTypeMultipart < Struct.new(:media_type, :media_subtype,
					 :parts,
					 :param, :disposition, :language,
					 :extension)
      def multipart?
	return true
      end
    end

    class ResponseParser
      def parse(str)
	@str = str
	@pos = 0
	@lex_state = EXPR_BEG
	@token = nil
	return response
      end

      private

      EXPR_BEG		= :EXPR_BEG
      EXPR_DATA		= :EXPR_DATA
      EXPR_TEXT		= :EXPR_TEXT
      EXPR_RTEXT	= :EXPR_RTEXT
      EXPR_CTEXT	= :EXPR_CTEXT

      T_SPACE	= :SPACE
      T_NIL	= :NIL
      T_NUMBER	= :NUMBER
      T_ATOM	= :ATOM
      T_QUOTED	= :QUOTED
      T_LPAR	= :LPAR
      T_RPAR	= :RPAR
      T_BSLASH	= :BSLASH
      T_STAR	= :STAR
      T_LBRA	= :LBRA
      T_RBRA	= :RBRA
      T_LITERAL	= :LITERAL
      T_PLUS	= :PLUS
      T_PERCENT	= :PERCENT
      T_CRLF	= :CRLF
      T_EOF	= :EOF
      T_TEXT	= :TEXT

      BEG_REGEXP = /\G(?:\
(?# 1:	SPACE	)( )|\
(?# 2:	NIL	)(NIL)(?=[\x80-\xff(){ \x00-\x1f\x7f%*"\\\[\]+])|\
(?# 3:	NUMBER	)(\d+)(?=[\x80-\xff(){ \x00-\x1f\x7f%*"\\\[\]+])|\
(?# 4:	ATOM	)([^\x80-\xff(){ \x00-\x1f\x7f%*"\\\[\]+]+)|\
(?# 5:	QUOTED	)"((?:[^\x80-\xff\x00\r\n"\\]|\\["\\])*)"|\
(?# 6:	LPAR	)(\()|\
(?# 7:	RPAR	)(\))|\
(?# 8:	BSLASH	)(\\)|\
(?# 9:	STAR	)(\*)|\
(?# 10:	LBRA	)(\[)|\
(?# 11:	RBRA	)(\])|\
(?# 12:	LITERAL	)\{(\d+)\}\r\n|\
(?# 13:	PLUS	)(\+)|\
(?# 14:	PERCENT	)(%)|\
(?# 15:	CRLF	)(\r\n)|\
(?# 16:	EOF	)(\z))/ni

      DATA_REGEXP = /\G(?:\
(?# 1:	SPACE	)( )|\
(?# 2:	NIL	)(NIL)|\
(?# 3:	NUMBER	)(\d+)|\
(?# 4:	QUOTED	)"((?:[^\x80-\xff\x00\r\n"\\]|\\["\\])*)"|\
(?# 5:	LITERAL	)\{(\d+)\}\r\n|\
(?# 6:	LPAR	)(\()|\
(?# 7:	RPAR	)(\)))/ni

      TEXT_REGEXP = /\G(?:\
(?# 1:	TEXT	)([^\x00\x80-\xff\r\n]*))/ni

      RTEXT_REGEXP = /\G(?:\
(?# 1:	LBRA	)(\[)|\
(?# 2:	TEXT	)([^\x00\x80-\xff\r\n]*))/ni

      CTEXT_REGEXP = /\G(?:\
(?# 1:	TEXT	)([^\x00\x80-\xff\r\n\]]*))/ni

      Token = Struct.new(:symbol, :value)

      def response
	token = lookahead
	case token.symbol
	when T_PLUS
	  result = continue_req
	when T_STAR
	  result = response_untagged
	else
	  result = response_tagged
	end
	match(T_CRLF)
	match(T_EOF)
	return result
      end

      def continue_req
	match(T_PLUS)
	match(T_SPACE)
	return ContinueRequest.new(resp_text, @str)
      end

      def response_untagged
	match(T_STAR)
	match(T_SPACE)
	token = lookahead
	if token.symbol == T_NUMBER
	  return numeric_response
	elsif token.symbol == T_ATOM
	  case token.value
	  when /\A(?:OK|NO|BAD|BYE|PREAUTH)\z/ni
	    return response_cond
	  when /\A(?:FLAGS)\z/ni
	    return flags_response
	  when /\A(?:LIST|LSUB)\z/ni
	    return list_response
	  when /\A(?:SEARCH|SORT)\z/ni
	    return search_response
	  when /\A(?:STATUS)\z/ni
	    return status_response
	  when /\A(?:CAPABILITY)\z/ni
	    return capability_response
	  else
	    return text_response
	  end
	else
	  parse_error("unexpected token %s", token.symbol)
	end
      end

      def response_tagged
	tag = atom
	match(T_SPACE)
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return TaggedResponse.new(tag, name, resp_text, @str)
      end

      def response_cond
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return UntaggedResponse.new(name, resp_text, @str)
      end

      def numeric_response
	n = number
	match(T_SPACE)
	token = match(T_ATOM)
	name = token.value.upcase
	case name
	when "EXISTS", "RECENT", "EXPUNGE"
	  return UntaggedResponse.new(name, n, @str)
	when "FETCH"
	  shift_token
	  match(T_SPACE)
	  data = FetchData.new(n, msg_att)
	  return UntaggedResponse.new(name, data, @str)
	end
      end

      def msg_att
	match(T_LPAR)
	attr = {}
	while true
	  token = lookahead
	  case token.symbol
	  when T_RPAR
	    shift_token
	    break
	  when T_SPACE
	    shift_token
	    token = lookahead
	  end
	  case token.value
	  when /\A(?:ENVELOPE)\z/ni
	    name, val = envelope_data
	  when /\A(?:FLAGS)\z/ni
	    name, val = flags_data
	  when /\A(?:INTERNALDATE)\z/ni
	    name, val = internaldate_data
	  when /\A(?:RFC822(?:\.HEADER|\.TEXT)?)\z/ni
	    name, val = rfc822_text
	  when /\A(?:RFC822\.SIZE)\z/ni
	    name, val = rfc822_size
	  when /\A(?:BODY(?:STRUCTURE)?)\z/ni
	    name, val = body_data
	  when /\A(?:UID)\z/ni
	    name, val = uid_data
	  else
	    parse_error("unknown attribute `%s'", token.value)
	  end
	  attr[name] = val
	end
	return attr
      end

      def envelope_data
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return name, envelope
      end

      def envelope
	@lex_state = EXPR_DATA
	match(T_LPAR)
	date = nstring
	match(T_SPACE)
	subject = nstring
	match(T_SPACE)
	from = address_list
	match(T_SPACE)
	sender = address_list
	match(T_SPACE)
	reply_to = address_list
	match(T_SPACE)
	to = address_list
	match(T_SPACE)
	cc = address_list
	match(T_SPACE)
	bcc = address_list
	match(T_SPACE)
	in_reply_to = nstring
	match(T_SPACE)
	message_id = nstring
	match(T_RPAR)
	@lex_state = EXPR_BEG
	return Envelope.new(date, subject, from, sender, reply_to,
			    to, cc, bcc, in_reply_to, message_id)
      end

      def flags_data
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return name, flag_list
      end

      def internaldate_data
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	token = match(T_QUOTED)
	return name, token.value
      end

      def rfc822_text
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return name, nstring
      end

      def rfc822_size
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return name, number
      end

      def body_data
	token = match(T_ATOM)
	name = token.value.upcase
	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	  return name, body
	end
	name.concat(section)
	token = lookahead
	if token.symbol == T_ATOM
	  name.concat(token.value)
	  shift_token
	end
	match(T_SPACE)
	data = nstring
	return name, data
      end

      def body
	@lex_state = EXPR_DATA
	match(T_LPAR)
	token = lookahead
	if token.symbol == T_LPAR
	  result = body_type_mpart
	else
	  result = body_type_1part
	end
	match(T_RPAR)
	@lex_state = EXPR_BEG
	return result
      end

      def body_type_1part
	token = lookahead
	case token.value
	when /\A(?:TEXT)\z/ni
	  return body_type_text
	when /\A(?:MESSAGE)\z/ni
	  return body_type_msg
	else
	  return body_type_basic
	end
      end

      def body_type_basic
	mtype, msubtype = media_type
	match(T_SPACE)
	param, content_id, desc, enc, size = body_fields
	md5, disposition, language, extension = body_ext_1part
	return BodyTypeBasic.new(mtype, msubtype,
				 param, content_id,
				 desc, enc, size,
				 md5, disposition, language, extension)
      end

      def body_type_text
	mtype, msubtype = media_type
	match(T_SPACE)
	param, content_id, desc, enc, size = body_fields
	match(T_SPACE)
	lines = number
	md5, disposition, language, extension = body_ext_1part
	return BodyTypeText.new(mtype, msubtype,
				param, content_id,
				desc, enc, size,
				lines,
				md5, disposition, language, extension)
      end

      def body_type_msg
	mtype, msubtype = media_type
	match(T_SPACE)
	param, content_id, desc, enc, size = body_fields
	match(T_SPACE)
	env = envelope
	match(T_SPACE)
	b = body
	match(T_SPACE)
	lines = number
	md5, disposition, language, extension = body_ext_1part
	return BodyTypeMessage.new(mtype, msubtype,
				   param, content_id,
				   desc, enc, size,
				   env, b, lines,
				   md5, disposition, language, extension)
      end

      def body_type_mpart
	parts = []
	while true
	  token = lookahead
	  if token.symbol == T_SPACE
	    shift_token
	    break
	  end
	  parts.push(body)
	end
	mtype = "MULTIPART"
	msubtype = string.upcase
	param, disposition, language, extension = body_ext_mpart
	return BodyTypeMultipart.new(mtype, msubtype, parts,
				     param, disposition, language,
				     extension)
      end

      def media_type
	mtype = string.upcase
	match(T_SPACE)
	msubtype = string.upcase
	return mtype, msubtype
      end

      def body_fields
	param = body_fld_param
	match(T_SPACE)
	content_id = nstring
	match(T_SPACE)
	desc = nstring
	match(T_SPACE)
	enc = string.upcase
	match(T_SPACE)
	size = number
	return param, content_id, desc, enc, size
      end

      def body_fld_param
	token = lookahead
	if token.symbol == T_NIL
	  shift_token
	  return nil
	end
	match(T_LPAR)
	param = {}
	while true
	  token = lookahead
	  case token.symbol
	  when T_RPAR
	    shift_token
	    break
	  when T_SPACE
	    shift_token
	  end
	  name = string.upcase
	  match(T_SPACE)
	  val = string
	  param[name] = val
	end
	return param
      end

      def body_ext_1part
	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	else
	  return nil
	end
	md5 = nstring

	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	else
	  return md5
	end
	disposition = body_fld_dsp

	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	else
	  return md5, disposition
	end
	language = body_fld_lang

	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	else
	  return md5, disposition, language
	end

	extension = body_extensions
	return md5, disposition, language, extension
      end

      def body_ext_mpart
	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	else
	  return nil
	end
	param = body_fld_param

	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	else
	  return param
	end
	disposition = body_fld_dsp
	match(T_SPACE)
	language = body_fld_lang

	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	else
	  return param, disposition, language
	end

	extension = body_extensions
	return param, disposition, language, extension
      end

      def body_fld_dsp
	token = lookahead
	if token.symbol == T_NIL
	  shift_token
	  return nil
	end
	match(T_LPAR)
	dsp_type = string.upcase
	match(T_SPACE)
	param = body_fld_param
	match(T_RPAR)
	return ContentDisposition.new(dsp_type, param)
      end

      def body_fld_lang
	token = lookahead
	if token.symbol == T_LPAR
	  shift_token
	  result = []
	  while true
	    token = lookahead
	    case token.symbol
	    when T_RPAR
	      shift_token
	      return result
	    when T_SPACE
	      shift_token
	    end
	    result.push(string.upcase)
	  end
	else
	  lang = nstring
	  if lang
	    return lang.upcase
	  else
	    return lang
	  end
	end
      end

      def body_extensions
	result = []
	while true
	  token = lookahead
	  case token.symbol
	  when T_RPAR
	    return result
	  when T_SPACE
	    shift_token
	  end
	  result.push(body_extension)
	end
      end

      def body_extension
	token = lookahead
	case token.symbol
	when T_LPAR
	  shift_token
	  result = body_extensions
	  match(T_RPAR)
	  return result
	when T_NUMBER
	  return number
	else
	  return nstring
	end
      end

      def section
	str = ""
	token = match(T_LBRA)
	str.concat(token.value)
	token = match(T_ATOM)
	str.concat(token.value)
	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	  str.concat(token.value)
	  token = match(T_LPAR)
	  str.concat(token.value)
	  while true
	    token = lookahead
	    case token.symbol
	    when T_RPAR
	      str.concat(token.value)
	      shift_token
	      break
	    when T_SPACE
	      shift_token
	      str.concat(token.value)
	    end
	    str.concat(format_string(astring))
	  end
	end
	token = match(T_RBRA)
	str.concat(token.value)
	return str
      end

      def format_string(str)
	case str
	when ""
	  return '""'
	when /[\x80-\xff\r\n]/n
	  # literal
	  return "{" + str.length.to_s + "}" + CRLF + str
	when /[(){ \x00-\x1f\x7f%*"\\]/n
	  # quoted string
	  return '"' + str.gsub(/["\\]/n, "\\\\\\&") + '"'
	else
	  # atom
	  return str
	end
      end

      def uid_data
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return name, number
      end

      def text_response
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	@lex_state = EXPR_TEXT
	token = match(T_TEXT)
	@lex_state = EXPR_BEG
	return UntaggedResponse.new(name, token.value)
      end

      def flags_response
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return UntaggedResponse.new(name, flag_list, @str)
      end

      def list_response
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	return UntaggedResponse.new(name, mailbox_list, @str)
      end

      def mailbox_list
	attr = flag_list
	match(T_SPACE)
	token = match(T_QUOTED, T_NIL)
	if token.symbol == T_NIL
	  delim = nil
	else
	  delim = token.value
	end
	match(T_SPACE)
	name = astring
	return MailboxList.new(attr, delim, name)
      end

      def search_response
	token = match(T_ATOM)
	name = token.value.upcase
	token = lookahead
	if token.symbol == T_SPACE
	  shift_token
	  data = []
	  while true
	    token = lookahead
	    case token.symbol
	    when T_CRLF
	      break
	    when T_SPACE
	      shift_token
	    end
	    data.push(number)
	  end
	else
	  data = []
	end
	return UntaggedResponse.new(name, data, @str)
      end

      def status_response
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	mailbox = astring
	match(T_SPACE)
	match(T_LPAR)
	attr = {}
	while true
	  token = lookahead
	  case token.symbol
	  when T_RPAR
	    shift_token
	    break
	  when T_SPACE
	    shift_token
	  end
	  token = match(T_ATOM)
	  key = token.value.upcase
	  match(T_SPACE)
	  val = number
	  attr[key] = val
	end
	data = StatusData.new(mailbox, attr)
	return UntaggedResponse.new(name, data, @str)
      end

      def capability_response
	token = match(T_ATOM)
	name = token.value.upcase
	match(T_SPACE)
	data = []
	while true
	  token = lookahead
	  case token.symbol
	  when T_CRLF
	    break
	  when T_SPACE
	    shift_token
	  end
	  data.push(atom.upcase)
	end
	return UntaggedResponse.new(name, data, @str)
      end

      def resp_text
	@lex_state = EXPR_RTEXT
	token = lookahead
	if token.symbol == T_LBRA
	  code = resp_text_code
	else
	  code = nil
	end
	token = match(T_TEXT)
	@lex_state = EXPR_BEG
	return ResponseText.new(code, token.value)
      end

      def resp_text_code
	@lex_state = EXPR_BEG
	match(T_LBRA)
	token = match(T_ATOM)
	name = token.value.upcase
	case name
	when /\A(?:ALERT|PARSE|READ-ONLY|READ-WRITE|TRYCREATE)\z/n
	  result = ResponseCode.new(name, nil)
	when /\A(?:PERMANENTFLAGS)\z/n
	  match(T_SPACE)
	  result = ResponseCode.new(name, flag_list)
	when /\A(?:UIDVALIDITY|UIDNEXT|UNSEEN)\z/n
	  match(T_SPACE)
	  result = ResponseCode.new(name, number)
	end
	match(T_RBRA)
	@lex_state = EXPR_RTEXT
	return result
      end

      def address_list
	token = lookahead
	if token.symbol == T_NIL
	  shift_token
	  return nil
	else
	  result = []
	  match(T_LPAR)
	  while true
	    token = lookahead
	    case token.symbol
	    when T_RPAR
	      shift_token
	      break
	    when T_SPACE
	      shift_token
	    end
	    result.push(address)
	  end
	  return result
	end
      end

      ADDRESS_REGEXP = /\G\
(?# 1: NAME	)(?:NIL|"((?:[^\x80-\xff\x00\r\n"\\]|\\["\\])*)") \
(?# 2: ROUTE	)(?:NIL|"((?:[^\x80-\xff\x00\r\n"\\]|\\["\\])*)") \
(?# 3: MAILBOX	)(?:NIL|"((?:[^\x80-\xff\x00\r\n"\\]|\\["\\])*)") \
(?# 4: HOST	)(?:NIL|"((?:[^\x80-\xff\x00\r\n"\\]|\\["\\])*)")\
\)/ni

      def address
	match(T_LPAR)
	if @str.index(ADDRESS_REGEXP, @pos)
	  # address does not include literal.
	  @pos = $~.end(0)
	  name = $1 ? $1.gsub(/\\(["\\])/n, "\\1") : nil
	  route = $2 ? $2.gsub(/\\(["\\])/n, "\\1") : nil
	  mailbox = $3 ? $3.gsub(/\\(["\\])/n, "\\1") : nil
	  host = $4 ? $4.gsub(/\\(["\\])/n, "\\1") : nil
	else
	  name = nstring
	  match(T_SPACE)
	  route = nstring
	  match(T_SPACE)
	  mailbox = nstring
	  match(T_SPACE)
	  host = nstring
	  match(T_RPAR)
	end
	return Address.new(name, route, mailbox, host)
      end

#        def flag_list
#  	result = []
#  	match(T_LPAR)
#  	while true
#  	  token = lookahead
#  	  case token.symbol
#  	  when T_RPAR
#  	    shift_token
#  	    break
#  	  when T_SPACE
#  	    shift_token
#  	  end
#  	  result.push(flag)
#  	end
#  	return result
#        end

#        def flag
#  	token = lookahead
#  	if token.symbol == T_BSLASH
#  	  shift_token
#  	  token = lookahead
#  	  if token.symbol == T_STAR
#  	    shift_token
#  	    return token.value.intern
#  	  else
#  	    return atom.intern
#  	  end
#  	else
#  	  return atom
#  	end
#        end

      FLAG_REGEXP = /\
(?# FLAG	)\\([^\x80-\xff(){ \x00-\x1f\x7f%"\\]+)|\
(?# ATOM	)([^\x80-\xff(){ \x00-\x1f\x7f%*"\\]+)/n

      def flag_list
	if @str.index(/\(([^)]*)\)/ni, @pos)
	  @pos = $~.end(0)
	  return $1.scan(FLAG_REGEXP).collect { |flag, atom|
	    atom || flag.intern
	  }
	else
	  parse_error("invalid flag list")
	end
      end

      def nstring
	token = lookahead
	if token.symbol == T_NIL
	  shift_token
	  return nil
	else
	  return string
	end
      end

      def astring
	token = lookahead
	if string_token?(token)
	  return string
	else
	  return atom
	end
      end

      def string
	token = match(T_QUOTED, T_LITERAL)
	return token.value
      end

      STRING_TOKENS = [T_QUOTED, T_LITERAL]

      def string_token?(token)
	return STRING_TOKENS.include?(token.symbol)
      end

      def atom
  	result = ""
  	while true
  	  token = lookahead
  	  if atom_token?(token)
  	    result.concat(token.value)
  	    shift_token
  	  else
  	    if result.empty?
  	      parse_error("unexpected token %s", token.symbol)
  	    else
  	      return result
  	    end
  	  end
  	end
      end

      ATOM_TOKENS = [
	T_ATOM,
	T_NUMBER,
	T_NIL,
	T_LBRA,
	T_RBRA,
	T_PLUS
      ]

      def atom_token?(token)
	return ATOM_TOKENS.include?(token.symbol)
      end

      def number
	token = match(T_NUMBER)
	return token.value.to_i
      end

      def nil_atom
	match(T_NIL)
	return nil
      end

      def match(*args)
	token = lookahead
	unless args.include?(token.symbol)
	  parse_error('unexpected token %s (expected %s)',
		      token.symbol.id2name,
		      args.collect {|i| i.id2name}.join(" or "))
	end
	shift_token
	return token
      end

      def lookahead
	unless @token
	  @token = next_token
	end
	return @token
      end

      def shift_token
	@token = nil
      end

      def next_token
	case @lex_state
	when EXPR_BEG
	  if @str.index(BEG_REGEXP, @pos)
	    @pos = $~.end(0)
	    if $1
	      return Token.new(T_SPACE, $+)
	    elsif $2
	      return Token.new(T_NIL, $+)
	    elsif $3
	      return Token.new(T_NUMBER, $+)
	    elsif $4
	      return Token.new(T_ATOM, $+)
	    elsif $5
	      return Token.new(T_QUOTED,
			       $+.gsub(/\\(["\\])/n, "\\1"))
	    elsif $6
	      return Token.new(T_LPAR, $+)
	    elsif $7
	      return Token.new(T_RPAR, $+)
	    elsif $8
	      return Token.new(T_BSLASH, $+)
	    elsif $9
	      return Token.new(T_STAR, $+)
	    elsif $10
	      return Token.new(T_LBRA, $+)
	    elsif $11
	      return Token.new(T_RBRA, $+)
	    elsif $12
	      len = $+.to_i
	      val = @str[@pos, len]
	      @pos += len
	      return Token.new(T_LITERAL, val)
	    elsif $13
	      return Token.new(T_PLUS, $+)
	    elsif $14
	      return Token.new(T_PERCENT, $+)
	    elsif $15
	      return Token.new(T_CRLF, $+)
	    elsif $16
	      return Token.new(T_EOF, $+)
	    else
	      parse_error("[Net::IMAP BUG] BEG_REGEXP is invalid")
	    end
	  else
	    @str.index(/\S*/n, @pos)
	    parse_error("unknown token - %s", $&.dump)
	  end
	when EXPR_DATA
	  if @str.index(DATA_REGEXP, @pos)
	    @pos = $~.end(0)
	    if $1
	      return Token.new(T_SPACE, $+)
	    elsif $2
	      return Token.new(T_NIL, $+)
	    elsif $3
	      return Token.new(T_NUMBER, $+)
	    elsif $4
	      return Token.new(T_QUOTED,
			       $+.gsub(/\\(["\\])/n, "\\1"))
	    elsif $5
	      len = $+.to_i
	      val = @str[@pos, len]
	      @pos += len
	      return Token.new(T_LITERAL, val)
	    elsif $6
	      return Token.new(T_LPAR, $+)
	    elsif $7
	      return Token.new(T_RPAR, $+)
	    else
	      parse_error("[Net::IMAP BUG] BEG_REGEXP is invalid")
	    end
	  else
	    @str.index(/\S*/n, @pos)
	    parse_error("unknown token - %s", $&.dump)
	  end
	when EXPR_TEXT
	  if @str.index(TEXT_REGEXP, @pos)
	    @pos = $~.end(0)
	    if $1
	      return Token.new(T_TEXT, $+)
	    else
	      parse_error("[Net::IMAP BUG] TEXT_REGEXP is invalid")
	    end
	  else
	    @str.index(/\S*/n, @pos)
	    parse_error("unknown token - %s", $&.dump)
	  end
	when EXPR_RTEXT
	  if @str.index(RTEXT_REGEXP, @pos)
	    @pos = $~.end(0)
	    if $1
	      return Token.new(T_LBRA, $+)
	    elsif $2
	      return Token.new(T_TEXT, $+)
	    else
	      parse_error("[Net::IMAP BUG] RTEXT_REGEXP is invalid")
	    end
	  else
	    @str.index(/\S*/n, @pos)
	    parse_error("unknown token - %s", $&.dump)
	  end
	when EXPR_CTEXT
	  if @str.index(CTEXT_REGEXP, @pos)
	    @pos = $~.end(0)
	    if $1
	      return Token.new(T_TEXT, $+)
	    else
	      parse_error("[Net::IMAP BUG] CTEXT_REGEXP is invalid")
	    end
	  else
	    @str.index(/\S*/n, @pos) #/
	    parse_error("unknown token - %s", $&.dump)
	  end
	else
	  parse_error("illegal @lex_state - %s", @lex_state.inspect)
	end
      end

      def parse_error(fmt, *args)
	if IMAP.debug
	  $stderr.printf("@str: %s\n", @str.dump)
	  $stderr.printf("@pos: %d\n", @pos)
	  $stderr.printf("@lex_state: %s\n", @lex_state)
	  if @token.symbol
	    $stderr.printf("@token.symbol: %s\n", @token.symbol)
	    $stderr.printf("@token.value: %s\n", @token.value.inspect)
	  end
	end
	raise ResponseParseError, format(fmt, *args)
      end
    end

    class LoginAuthenticator
      def process(data)
	case @state
	when STATE_USER
	  @state = STATE_PASSWORD
	  return @user
	when STATE_PASSWORD
	  return @password
	end
      end

      private

      STATE_USER = :USER
      STATE_PASSWORD = :PASSWORD

      def initialize(user, password)
	@user = user
	@password = password
	@state = STATE_USER
      end
    end
    add_authenticator "LOGIN", LoginAuthenticator

    class CramMD5Authenticator
      def process(challenge)
	digest = hmac_md5(challenge, @password)
	return @user + " " + digest
      end

      private

      def initialize(user, password)
	@user = user
	@password = password
      end

      def hmac_md5(text, key)
	if key.length > 64
	  md5 = MD5.new(key)
	  key = md5.digest
	end

	k_ipad = key + "\0" * (64 - key.length)
	k_opad = key + "\0" * (64 - key.length)
	for i in 0..63
	  k_ipad[i] ^= 0x36
	  k_opad[i] ^= 0x5c
	end

	md5 = MD5.new
	md5.update(k_ipad)
	md5.update(text)
	digest = md5.digest

	md5 = MD5.new
	md5.update(k_opad)
	md5.update(digest)
	return md5.hexdigest
      end
    end
    add_authenticator "CRAM-MD5", CramMD5Authenticator

    class Error < StandardError
    end

    class DataFormatError < Error
    end

    class ResponseParseError < Error
    end

    class ResponseError < Error
    end

    class NoResponseError < ResponseError
    end

    class BadResponseError < ResponseError
    end

    class ByeResponseError < ResponseError
    end
  end
end