TRACKS = {
  Links = {
    left = true,
    right = false
  },
  Mitte = {
    left = false,
    right = true
  },
  Rechts = {
    left = false,
    right = false
  }
}

TRACK_KEYS = {}
TRACK_COUNT = 0

for k, v in pairs(TRACKS) do
  TRACK_COUNT = TRACK_COUNT + 1
  TRACK_KEYS[TRACK_COUNT] = k
end

monitor = peripheral.wrap('monitor_0')

function updateMonitor()
  monitor.setCursorPos(1, 1)
  monitor.clearLine()
  monitor.write('Strecken:')
  for i = 1, TRACK_COUNT do
    monitor.setCursorPos(1, i + 1)
    monitor.clearLine()
    active = true
    for side, expectedValue in pairs(TRACKS[TRACK_KEYS[i]]) do
      active = active and (rs.getOutput(side) == expectedValue)
    end
    line = tostring(i)
    if active then
      line = line .. ')'
    else
      line = line .. '.'
    end

    line = line .. ' ' .. TRACK_KEYS[i]
    monitor.write(line)
  end
end

function chooseTrack(digit)
  if digit > TRACK_COUNT then
    print('Unknown track')
  end

  print('Activating track #' .. tostring(digit))

  for side, value in pairs(TRACKS[TRACK_KEYS[digit]]) do
    rs.setOutput(side, value)
  end

  updateMonitor()
end

updateMonitor()

while true do
  local event, key, is_held = os.pullEvent('key_up')

  digit = -1
  if key == keys.one or key == keys.numPad1 then
    digit = 1
  elseif key == keys.two or key == keys.numPad2 then
    digit = 2
  elseif key == keys.three or key == keys.numPad3 then
    digit = 3
  elseif key == keys.four or key == keys.numPad4 then
    digit = 4
  elseif key == keys.five or key == keys.numPad5 then
    digit = 5
  elseif key == keys.six or key == keys.numPad6 then
    digit = 6
  elseif key == keys.seven or key == keys.numPad7 then
    digit = 7
  elseif key == keys.eight or key == keys.numPad8 then
    digit = 8
  elseif key == keys.nine or key == keys.numPad9 then
    digit = 9
  end

  if digit > -1 then
    chooseTrack(digit)
  end
end