#!/usr/bin/env ruby

def display
  STICKS.each do |stick|
    print "|"
    stick.each do |ring|
      print ring.to_s + " "
    end
    puts
  end
end

def valid_move?(from, to)
  range = 0..(STICKS.size-1)
  return [false, "no-op"] if from == to
  return [false, "from should be 0..2"] unless range.cover?(from)
  return [false, "to should be 0..2"] unless range.cover?(to)
  return [false, "no ring on stick #{from}"] if STICKS[from].size == 0

  ring = STICKS[from][-1]

  # Avoid a nil check
  return true if STICKS[to].empty?

  return [false, "invalid move"] if ring > STICKS[to][-1]

  true
end

print "Number of sticks: "
STICKS = gets.to_i.times.map { [] }
puts

print "Height of tower: "
STICKS[0] = (1..(gets.to_i)).to_a.reverse
puts

loop do
  display

  if STICKS[0].empty? && STICKS[1].empty?
    puts "you win!"
    exit 0
  end

  print "move: "
  from, to = gets.split(" ", 2)
  from = from.to_i
  to = to.to_i
  puts "Move rightmost ring from stick #{from.to_i} to stick #{to.to_i}"

  valid, error = valid_move?(from, to)
  if !valid
    puts "Invalid move! #{error}"
    next
  end

  STICKS[to].push(STICKS[from].pop)
end