Spiralizer.exs

# A B C D
# E F G H
# I J K L
# M N O P

# a b c d h l p o n m i e f g k j"
# top, right, bottom, left
#
defmodule Spiralizer do
  defp top(acc, []) do
    acc
  end

  defp top(acc, [head | tail]) do
    new_acc = Enum.concat(acc, head)
    right(new_acc, tail)
  end

  defp right(acc, []) do
    acc
  end

  defp right(acc, data) do
    new_acc = acc
      |> Enum.concat(data |> Enum.map(&(List.last(&1))))

    new_arr = Enum.map(data, fn(row) ->
      [head | tail] = Enum.reverse(row)
      Enum.reverse(tail)
    end)

    bottom(new_acc, new_arr)
  end

  defp bottom(acc, []) do
    acc
  end

  defp bottom(acc, data) do
    new_acc = acc
      |> Enum.concat(data |> Enum.reverse() |> List.first() |> Enum.reverse())
    [head | tail] = Enum.reverse(data)
    new_arr = Enum.reverse(tail)
    left(new_acc, new_arr)
  end

  defp left(acc, []) do
    acc
  end

  defp left(acc, data) do
    new_acc = acc
      |> Enum.concat(data |> Enum.map(&(List.first(&1))) |> Enum.reverse())
    new_arr = Enum.map(data, fn([_head | tail]) -> tail end)
    top(new_acc, new_arr)
  end

  def runner(data) do
    top([], data) |> Enum.map(&(String.downcase(&1))) |> Enum.join(" ")
  end
end