tictactoe.ex

defmodule Tictactoe do

  @winning_positions [{0, 1, 2}, {0, 3, 6}, {0, 4, 8}, {1, 4, 7}, {2, 5, 8}, {3, 4, 5}, {6, 7, 8}, {2, 4, 6}]

  def winning_position?(board) do
    case winning?(board) do
      {false, _} -> {false, nil}
      winner -> winner
    end
  end

  defp winning?(board) do
    Enum.reduce(
      @winning_positions,
      {false, nil},
      fn({x, y, z}, acc) -> iterate_positions({x, y, z}, board, acc) end
    )
  end

  defp iterate_positions(_, _, {true, winner}), do: {true, winner}
  defp iterate_positions({x, y, z}, board, {false, _}) do
    case Enum.at(board, x) do
      "" -> {false, nil}
      nil -> {false, nil}
      _ -> {Enum.at(board, x) == Enum.at(board, y) and Enum.at(board, x) == Enum.at(board, z), Enum.at(board, x)}
    end
  end

end