module Utils::IRB::Shell

def irb_time_watch(duration = 1)
  start = Time.now
  pre = nil
  avg = Hash.new
  i = 0
  fetch_next = -> cur do
    pre = cur.map(&:to_f)
    i += 1
    sleep duration
  end
  loop do
    cur = [ yield(i) ].flatten
    unless pre
      fetch_next.(cur)
      redo
    end
    expired = Time.now - start
    diffs = cur.zip(pre).map { |c, p| c - p }
    rates = diffs.map { |d| d / duration }
    durs = cur.zip(rates).each_with_index.map { |(c, r), i|
      if r < 0
        x = c.to_f / -r
        a = avg[i].to_f
        a -= a / 2
        a += x / 2
        d = Tins::Duration.new(a)
        ds = d.to_s
        ds.singleton_class { define_method(:to_f) { d.to_f } }
        avg[i] = ds
      end
      avg[i]
    }
    warn "#{expired} #{cur.zip(diffs, rates, durs) * ' '} 𝝙 / per sec."
    fetch_next.(cur)
    sleep duration
  end
end