IRC refactoring: casemaps

[rbot] / lib / irc / casemap.rb

#-- vim:sw=2:et
#++
# :title: IRC casemaps
#
# This module defines the IRC casemap class and the most common casemaps
#
# Author:: Giuseppe Bilotta (giuseppe.bilotta@gmail.com)

require 'singleton'

module Irc

  # Due to its Scandinavian origins, IRC has strange case mappings, which
  # consider the characters <tt>{}|^</tt> as the uppercase
  # equivalents of # <tt>[]\~</tt>.
  #
  # This is however not the same on all IRC servers: some use standard ASCII
  # casemapping, other do not consider <tt>^</tt> as the uppercase of
  # <tt>~</tt>
  #
  class Casemap
    @@casemaps = {}

    # Create a new casemap with name _name_, uppercase characters _upper_ and
    # lowercase characters _lower_
    #
    def initialize(name, upper, lower)
      @key = name.to_sym
      raise "Casemap #{name.inspect} already exists!" if @@casemaps.has_key?(@key)
      @@casemaps[@key] = {
        :upper => upper,
        :lower => lower,
        :casemap => self
      }
    end

    # Returns the Casemap with the given name
    #
    def Casemap.get(name)
      @@casemaps[name.to_sym][:casemap]
    end

    # Retrieve the 'uppercase characters' of this Casemap
    #
    def upper
      @@casemaps[@key][:upper]
    end

    # Retrieve the 'lowercase characters' of this Casemap
    #
    def lower
      @@casemaps[@key][:lower]
    end

    # Return a Casemap based on the receiver
    #
    def to_irc_casemap
      self
    end

    # A Casemap is represented by its lower/upper mappings
    #
    def inspect
      self.__to_s__[0..-2] + " #{upper.inspect} ~(#{self})~ #{lower.inspect}>"
    end

    # As a String we return our name
    #
    def to_s
      @key.to_s
    end

    # Two Casemaps are equal if they have the same upper and lower ranges
    #
    def ==(arg)
      other = arg.to_irc_casemap
      return self.upper == other.upper && self.lower == other.lower
    end

    # Give a warning if _arg_ and self are not the same Casemap
    #
    def must_be(arg)
      other = arg.to_irc_casemap
      if self == other
        return true
      else
        warn "Casemap mismatch (#{self.inspect} != #{other.inspect})"
        return false
      end
    end

  end

  # The rfc1459 casemap
  #
  class RfcCasemap < Casemap
    include Singleton

    def initialize
      super('rfc1459', "\x41-\x5e", "\x61-\x7e")
    end

  end
  RfcCasemap.instance

  # The strict-rfc1459 Casemap
  #
  class StrictRfcCasemap < Casemap
    include Singleton

    def initialize
      super('strict-rfc1459', "\x41-\x5d", "\x61-\x7d")
    end

  end
  StrictRfcCasemap.instance

  # The ascii Casemap
  #
  class AsciiCasemap < Casemap
    include Singleton

    def initialize
      super('ascii', "\x41-\x5a", "\x61-\x7a")
    end

  end
  AsciiCasemap.instance


  # This module is included by all classes that are either bound to a server
  # or should have a casemap.
  #
  module ServerOrCasemap

    attr_reader :server

    # This method initializes the instance variables @server and @casemap
    # according to the values of the hash keys :server and :casemap in _opts_
    #
    def init_server_or_casemap(opts={})
      @server = opts.fetch(:server, nil)
      raise TypeError, "#{@server} is not a valid Irc::Server" if @server and not @server.kind_of?(Server)

      @casemap = opts.fetch(:casemap, nil)
      if @server
        if @casemap
          @server.casemap.must_be(@casemap)
          @casemap = nil
        end
      else
        @casemap = (@casemap || 'rfc1459').to_irc_casemap
      end
    end

    # This is an auxiliary method: it returns true if the receiver fits the
    # server and casemap specified in _opts_, false otherwise.
    #
    def fits_with_server_and_casemap?(opts={})
      srv = opts.fetch(:server, nil)
      cmap = opts.fetch(:casemap, nil)
      cmap = cmap.to_irc_casemap unless cmap.nil?

      if srv.nil?
        return true if cmap.nil? or cmap == casemap
      else
        return true if srv == @server and (cmap.nil? or cmap == casemap)
      end
      return false
    end

    # Returns the casemap of the receiver, by looking at the bound
    # @server (if possible) or at the @casemap otherwise
    #
    def casemap
      return @server.casemap if defined?(@server) and @server
      return @casemap
    end

    # Returns a hash with the current @server and @casemap as values of
    # :server and :casemap
    #
    def server_and_casemap
      h = {}
      h[:server] = @server if defined?(@server) and @server
      h[:casemap] = @casemap if defined?(@casemap) and @casemap
      return h
    end

    # We allow up/downcasing with a different casemap
    #
    def irc_downcase(cmap=casemap)
      self.to_s.irc_downcase(cmap)
    end

    # Up/downcasing something that includes this module returns its
    # Up/downcased to_s form
    #
    def downcase
      self.irc_downcase
    end

    # We allow up/downcasing with a different casemap
    #
    def irc_upcase(cmap=casemap)
      self.to_s.irc_upcase(cmap)
    end

    # Up/downcasing something that includes this module returns its
    # Up/downcased to_s form
    #
    def upcase
      self.irc_upcase
    end

  end

end


# We extend the String class with some Irc::Casemap methods
#
class String

  # This method returns the Irc::Casemap whose name is the receiver
  #
  def to_irc_casemap
    Irc::Casemap.get(self) rescue raise TypeError, "Unkown Irc::Casemap #{self.inspect}"
  end

  # This method returns a string which is the downcased version of the
  # receiver, according to the given _casemap_
  #
  #
  def irc_downcase(casemap='rfc1459')
    cmap = casemap.to_irc_casemap
    self.tr(cmap.upper, cmap.lower)
  end

  # This is the same as the above, except that the string is altered in place
  #
  # See also the discussion about irc_downcase
  #
  def irc_downcase!(casemap='rfc1459')
    cmap = casemap.to_irc_casemap
    self.tr!(cmap.upper, cmap.lower)
  end

  # Upcasing functions are provided too
  #
  # See also the discussion about irc_downcase
  #
  def irc_upcase(casemap='rfc1459')
    cmap = casemap.to_irc_casemap
    self.tr(cmap.lower, cmap.upper)
  end

  # In-place upcasing
  #
  # See also the discussion about irc_downcase
  #
  def irc_upcase!(casemap='rfc1459')
    cmap = casemap.to_irc_casemap
    self.tr!(cmap.lower, cmap.upper)
  end
end