AEst userIo

local MAX_OPTIONS = 13

function promptForNumber()
  local value = nil
  while value == nil do
    io.write("> ")
    value = tonumber(io.read())

    if value == nil then
      print("ERROR: Invalid number. Please try again.")
    end
  end

  return value
end

function promptForNumberInRange(min, max)
  local value = nil
  while value == nil do
    local tValue = promptForNumber()

    if tValue < min  then
      print("ERROR: please enter a number >= " .. min)
    elseif tValue > max then
      print("ERROR: please neter a number <= " .. max)
    else
      value = tValue
    end
  end

  return value
end

function printOptions(options, banner)
  local page = 1
  local N = table.getn(options)
  local maxPage = math.ceil(N / MAX_OPTIONS)
  local viewing = true

  while viewing do
    print(banner)

    if N > MAX_OPTIONS then
      term.clear()
      term.setCursorPos(1, 1)

      print(banner)
      print()

      print(string.format(
        "Viewing %d items (%d/%d)",
        N,
        page,
        maxPage
      ))
      print("------------------------------------")
    end

    local start = (((page - 1) * MAX_OPTIONS) + 1)
    for i = start, math.min(N, (start + MAX_OPTIONS - 1)), 1 do
      local option = options[i]

      if type(option) == "table" then
        option = option.name
      end

      print(string.format("%d. %s", i, option))
    end

    if N <= MAX_OPTIONS then
      break
    else
      print("------------------------------------")
      io.write("[j] previous, [k] next, [Enter] done")

      while true do
        local sEvent, key = os.pullEvent("key")

        if key == keys.k then
          page = math.min(maxPage, page+1)
          break
        elseif key == keys.j then
          page = math.max(1, page-1)
          break
        elseif key == keys.enter then
          viewing = false
          break
        end
      end
    end

    if not viewing then
      print()
    end
  end
end

function chooseOption(options)
  printOptions(options)

  local option = promptForNumberInRange(1, table.getn(options))
  return options[option]
end