class NIO::Monitor

def add_interest(interest)
  case interest
  when :r
    case @interests
    when :r  then @interests = :r
    when :w  then @interests = :rw
    when :rw then @interests = :rw
    when nil then @interests = :r
    end
  when :w
    case @interests
    when :r  then @interests = :rw
    when :w  then @interests = :w
    when :rw then @interests = :rw
    when nil then @interests = :w
    end
  when :rw
    @interests = :rw
  else raise ArgumentError, "bad interests: #{interest}"
  end
end

def close(deregister = true)
  @closed = true
  @selector.deregister(io) if deregister
end

def closed?
  @closed
end

def initialize(io, interests, selector)
  unless defined?(::OpenSSL) && io.is_a?(::OpenSSL::SSL::SSLSocket)
    unless io.is_a?(IO)
      if IO.respond_to? :try_convert
        io = IO.try_convert(io)
      elsif io.respond_to? :to_io
        io = io.to_io
      end
      raise TypeError, "can't convert #{io.class} into IO" unless io.is_a? IO
    end
  end
  @io        = io
  @interests = interests
  @selector  = selector
  @closed    = false
end

def interests=(interests)
  raise EOFError, "monitor is closed" if closed?
  raise ArgumentError, "bad interests: #{interests}" unless [:r, :w, :rw, nil].include?(interests)
  @interests = interests
end

def readable?
  readiness == :r || readiness == :rw
end

def remove_interest(interest)
  case interest
  when :r
    case @interests
    when :r  then @interests = nil
    when :w  then @interests = :w
    when :rw then @interests = :w
    when nil then @interests = nil
    end
  when :w
    case @interests
    when :r  then @interests = :r
    when :w  then @interests = nil
    when :rw then @interests = :r
    when nil then @interests = nil
    end
  when :rw
    @interests = nil
  else raise ArgumentError, "bad interests: #{interest}"
  end
end

def writable?
  readiness == :w || readiness == :rw
end