defmodule Bob do
  @spec hey(String.t()) :: String.t()
  def hey(input) do
    trimmed = String.trim(input)

    is_yell? = String.upcase(trimmed) == trimmed and String.downcase(trimmed) != trimmed
    is_question? = String.ends_with?(trimmed, "?")
    is_silence? = trimmed == ""

    cond do
      is_silence? ->
        "Fine. Be that way!"
      is_yell? and is_question? ->
        "Calm down, I know what I'm doing!"
      is_question? ->
        "Sure."
      is_yell? ->
        "Whoa, chill out!"
      true ->
        "Whatever."
    end
  end
end