ComputerCraft User Input

-- Prompts user for a non-nil value of a specified type, providing a specified default value
-- Returns a string, number, or boolean value
function promptt(msg, expType, default)
  msg = msg or ""
  expType = expType or "string"
  write(tostring(msg))
  local px, py = term.getCursorPos()

  while true do
    -- get user input
    local value
    if default then
      write(default)
      local _,key = os.pullEvent("key")
      if key == keys.enter then
        value = default
        print()
      else
        -- clear default value
        term.setCursorPos(px, py)
        write(string.rep(" ", string.len(default)))
        term.setCursorPos(px, py)
        value = read()
      end
    else
      value = read()
    end

    -- format value to correct type
    local strLen = string.len(value)
    if expType == "number" then
      value = tonumber(value)
    elseif expType == "boolean" then
      if string.upper(value) == "TRUE" then
        value = true
      elseif string.upper(value) == "FALSE" then
        value = false
      else
        value = nil
      end
    end

    if value == nil or value == "" then -- if not a valid type..
      -- clear user input
      term.setCursorPos(px, py)
      write(string.rep(" ", strLen))
      term.setCursorPos(px, py)
    else
      return value
    end
  end
end


-- Prompts user for a yes/no value
-- Returns true if "yes", false if "no"
function promptYesNo(msg)
  msg = msg or ""
  msg = msg.."(y/n): "
  write(msg)
  local px, py = term.getCursorPos()
  while true do
    local value = string.upper(read())
    if value == "Y" or value == "YES" then
      return true
    elseif value == "N" or value == "NO" then
      return false
    else
      -- clear input
      term.setCursorPos(px, py)
      write(string.rep(" ", string.len(value)))
      term.setCursorPos(px, py)
    end
  end
end


function main()
  local a = promptt("Enter a string: ")
  local b = promptt("Enter another string: ", "string", "ComputerCraft")
  local c = promptt("Enter a number: ", "number", "123456789")
  local d = promptt("Enter a boolean value: ", "boolean", "true")
  local e = promptYesNo("Having fun yet?")
  print(a)
  print(b)
  print(c)
  print(d)
  print(e)
end
main()