digital_numbers.ex

defmodule DigitalNumbers do
  @moduledoc """
  DigitalNumbers module provides an API to convert integer to LCD styled string integer
  """

  @digital_numbers %{
    0 => """
          _
         | |
         |_|
         """,
    1 => """

           |
           |
         """,
    2 => """
          _
          _|
         |_
         """,
    3 => """
          _
          _|
          _|
         """,
    4 => """

         |_|
           |
         """,
    5 => """
          _
         |_
          _|
         """,
    6 => """
          _
         |_
         |_|
         """,
    7 => """
          _
           |
           |
         """,
    8 => """
          _
         |_|
         |_|
         """,
    9 => """
          _
         |_|
           |
         """,
  }

  @doc """
  Print in the console the input in a LCD clock fashion.
  """
  def print(input \\ 0) do
    input
    |> parse_and_split()
    |> Stream.map(&String.to_integer/1)
    |> Stream.map(&transform_input_to_digital/1)
    |> Enum.reduce([], fn number, acc -> [number | acc] end)
    |> Enum.reverse()
  end

  @doc ~S"""
  Parse the input as the key and get it from the Module attribute printing a string formated value.

  ## Examples

      iex> DigitalNumbers.transform_input_to_digital(2)
      " _\n _|\n|_\n"

      iex> DigitalNumbers.transform_input_to_digital("1221")
      "Feed me with number only..."

      iex> DigitalNumbers.transform_input_to_digital(:ok)
      "Feed me with number only..."
  """
  def transform_input_to_digital(input) when is_integer(input) and input >= 0 and input <= 9 do
    Map.get(@digital_numbers, input)
  end

  def transform_input_to_digital(_) do
    "Feed me with number only..."
  end

  @doc """
  Convert the number based input in list of string(s).
  """
  defp parse_and_split(input) do
    input
    |> Integer.to_string()
    |> String.split("", trim: true)
  end

end