roulette.exs

defmodule Roulette do
  @min_bet 0.1

  def minimum_bet, do: @min_bet

  def print_score(game) do
    IO.puts("R: #{game.rounds}\tL: #{game.last_number}\t$#{game.cash}\tB$#{game.bet}\tH: #{game.hits}\tM: #{game.misses}\tH/M: #{h_to_m(game)}")
  end

  def h_to_m(%{hits: hits, misses: misses} = game) do
    hits / misses
  end

  def play_round(game) do
    game = %{game | cash: game.cash - game.bet}
    game = %{game | last_number: next_number()}
    game = case bet_won(game) do
      true -> %{game | hits: game.hits + 1, cash: game.cash + game.bet * 2, bet: @min_bet, bet_on: next_bet(game.bet_on)}
      false -> %{game | misses: game.misses + 1, bet: game.bet * 2}
    end
    game = %{game | rounds: game.rounds + 1}
    print_score(game)
    if(game.cash < 0, do: Kernel.exit(:shutdown))
    play_round(game)
  end

  def bet_won(game) do
    if(game.bet_on == :black, do: number_black?(game.last_number), else: number_red?(game.last_number))
  end

  def next_bet(current_bet) do
    case current_bet do
      :black -> :red
      :red -> :black
    end
  end

  def number_black?(number) do
    case number do
      x when x in 1..10 -> Integer.mod(x, 2) == 0
      x when x in 19..28 -> Integer.mod(x, 2) == 0
      x when x in 11..18 -> Integer.mod(x, 2) != 0
      x when x in 29..36 -> Integer.mod(x, 2) != 0
      _ -> false
    end
  end

  def number_red?(number) do
    case number do
      x when x in 1..10 -> Integer.mod(x, 2) != 0
      x when x in 19..28 -> Integer.mod(x, 2) != 0
      x when x in 11..18 -> Integer.mod(x, 2) == 0
      x when x in 29..36 -> Integer.mod(x, 2) == 0
      _ -> false
    end
  end

  def next_number() do
    :rand.uniform(36)
  end
end

game = %{cash: 100.0, hits: 0, misses: 0, rounds: 0, bet_on: :black, bet: Roulette.minimum_bet, last_number: nil}

Roulette.play_round(game)