type Rank = | Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Knight | Queen | King | Ace
type Suit = Hearts | Spades | Diamonds | Clubs
type Card = Card of (Rank * Suit)
let ranks = [Two ; Three ; Four ; Five ; Six ; Seven ; Eight ; Nine ; Ten ; Knight ; Queen ; King ; Ace]
let suits = [Hearts; Spades; Diamonds; Clubs]

let getValue r =
  match r with
  | Two -> 2
  | Three -> 3
  | Four -> 4
  | Five -> 5
  | Six -> 6
  | Seven -> 7
  | Eight -> 8
  | Nine -> 9
  | Ten | Knight | Queen | King -> 10
  | Ace -> 11

//Creates the deck of 52 cards. Like a customized zip function.
let zipCards suits ranks =
  let rec go l1 l2 result =
    match (l1, l2) with
    | l1 :: l1s, l2 :: l2s -> go (l1 :: l1s) l2s (Card (l2,l1) :: result)
    | l1 :: l1s, [] -> go l1s ranks result
    | _,_ -> result
  go suits ranks []

//This is the full deck of cards
let fullDeck = (zipCards suits ranks)

//Counts the given list of cards. If the value is above 21 and it contains ace, the ace turns into a 1 instead of 11 by subtracting 10 from the end result
let countHand hand =
  let countCards = hand |> List.fold (fun acc (r,_) -> acc + (getValue r)) 0
  let containsAce = List.map (fun (r,_) -> r = Ace) hand |> List.contains true
  if countCards > 21 && containsAce then countCards - 10 else countCards

//Take a random card from the list. Return the card, and the list without the card.
let takeRandomCard (cards: Card list) =
  let random = System.Random()
  let card = List.item (random.Next(cards.Length)) cards
  let newCards = List.except [card] cards
  (newCards, card)