slow_irb_emulate.rb

require'pty'
require'io/console'

PTY.spawn('irb'){|r,w|
  echo = true
  q = Queue.new
  Thread.new{
    loop{
      if echo != w.echo?
        echo = w.echo?
        q << [Time.now, echo]
      end
      sleep 0.01
    }
  }

  close = ->{
    r.close rescue nil
    w.close rescue nil
    q.close rescue nil
  }
  Thread.new{
    loop{
      data = STDIN.readpartial 1024
      close.call and break unless data
      w.write data
    } rescue nil
    close.call
  }
  t1 = Thread.new {
    loop do
      t, data = q.deq
      break unless t
      time = 0.5 + (t - Time.now)
      sleep time if time > 0
      case data
      when true
        STDIN.cooked!
      when false
        STDIN.raw!
      else
        STDOUT.write data
      end
    end rescue nil
    close.call
  }
  t2 = Thread.new{
    loop{
      data = r.readpartial 1
      close.call and break unless data
      q << [Time.now, data]
    } rescue nil
    close.call
  }
  t1.join
  t2.join
  close.call
}