09_deck/main.go

package deck

import (
	"fmt"
	"math/rand"
	"sort"
)

//go:generate stringer -type=Suit,Rank

// Suit represents the suit of a card:
// one of Spades, Diamonds, Clubs, Hearts,
// or Joker
type Suit uint8

const (
	Spades Suit = iota
	Diamonds
	Clubs
	Hearts
	Joker
)

// Rank represents the rank of a card:
// Ace, Two... Ten, Jack... King
type Rank uint8

const (
	_ Rank = iota
	Ace
	Two
	Three
	Four
	Five
	Six
	Seven
	Eight
	Nine
	Ten
	Jack
	Queen
	King
)

// Card contains both a Suit and a Rank.
// In the special case that Suit=Joker,
// Rank is often not relevant.
type Card struct {
	Suit Suit
	Rank Rank
}

// Formats the Card type as a string
func (c Card) String() string {
	if c.Suit == Joker {
		return "Joker"
	}
	return fmt.Sprintf("%s of %s", c.Rank, c.Suit)
}

// Generates a new deck (slice of Cards) which contains
// a full playing card deck sorted by Suit with
// no jokers.
// The function accepts functional arguments to
// modify the deck during creation
func New(opts ...func([]Card) []Card) []Card {
	deck := make([]Card, 52, 52)
	i := 0
	for s := 0; s < 4; s++ {
		for v := 1; v < 14; v++ {
			deck[i] = Card{Suit: Suit(s), Rank: Rank(v)}
			i++
		}
	}
	for _, opt := range opts {
		deck = opt(deck)
	}
	return deck
}

func lessBySuit(c1 Card, c2 Card) bool {
	if c1.Suit < c2.Suit {
		return true
	}
	if c1.Suit == c2.Suit && c1.Rank < c2.Rank {
		return true
	}
	return false
}

func lessByRank(c1 Card, c2 Card) bool {
	if c1.Rank < c2.Rank {
		return true
	}
	if c1.Rank == c2.Rank && c1.Suit < c2.Suit {
		return true
	}
	return false
}

// Sorts the deck (slice of Cards) by Suit, then by Rank
func SortBySuit(deck []Card) []Card {
	sort.Slice(deck, func(i, j int) bool {
		return lessBySuit(deck[i], deck[j])
	})
	return deck
}

// Sorts the deck (slice of Cards) by Rank, then by Suit
func SortByRank(deck []Card) []Card {
	sort.Slice(deck, func(i, j int) bool {
		return lessByRank(deck[i], deck[j])
	})
	return deck
}

// This returns a closure that adds n joker cards to the end
// of a deck (slice of Cards). The returned function
// can be passed as an option into New()
func AddNJokers(n int) func(deck []Card) []Card {
	return func(deck []Card) []Card {
		toAdd := make([]Card, n, n)
		for i, _ := range toAdd {
			toAdd[i] = Card{Suit: Joker}
		}
		return append(deck, toAdd...)
	}
}

// Shuffle randomizes the order of cards in a slice
func Shuffle(deck []Card) []Card {
	rand.Shuffle(len(deck), func(i, j int) {
		deck[i], deck[j] = deck[j], deck[i]
	})
	return deck
}

// RemoveCards takes Card arguments, and returns a closure
// that will remove all Cards matching one of the arguments
// from the deck (slice of Cards).
// The returned function can be passed as an option into New()
func RemoveCards(cards ...Card) func([]Card) []Card {
	return func(deck []Card) []Card {
		output := make([]Card, 0, len(deck))
		badKeys := make(map[Card]struct{})
		for _, card := range cards {
			badKeys[card] = struct{}{}
		}
		for _, card := range deck {
			if _, ok := badKeys[card]; !ok {
				output = append(output, card)
			}
		}
		return output
	}
}

// RemoveSuit takes Suit arguments, and returns a closure
// that will remove all Cards with a Suit equal to one of the
// arguments from the deck (slice of Cards).
// The returned function can be passed as an option into New()
func RemoveSuit(suits ...Suit) func([]Card) []Card {
	return func(deck []Card) []Card {
		output := make([]Card, 0, len(deck))
		badKeys := make(map[Suit]struct{})
		for _, suit := range suits {
			badKeys[suit] = struct{}{}
		}
		for _, card := range deck {
			if _, ok := badKeys[card.Suit]; !ok {
				output = append(output, card)
			}
		}
		return output
	}
}

// RemoveRank takes Rank arguments, and returns a closure
// that will remove all Cards with a Rank equal to one of the
// arguments from the deck (slice of Cards).
// The returned function can be passed as an option into New()
func RemoveRank(ranks ...Rank) func([]Card) []Card {
	return func(deck []Card) []Card {
		output := make([]Card, 0, len(deck))
		badKeys := make(map[Rank]struct{})
		for _, rank := range ranks {
			badKeys[rank] = struct{}{}
		}
		for _, card := range deck {
			if _, ok := badKeys[card.Rank]; !ok {
				output = append(output, card)
			}
		}
		return output
	}
}

// AddDeck appends a default deck to the deck passed in by the user
// (slice ef Cards), where the default deck is that created by New()
// with no options.
func AddDeck(deck []Card) []Card {
	newDeck := New()
	deck = append(deck, newDeck...)
	return deck
}

// Draw takes the top card from deck and appends it to hand, returning the
// hand and the deck as they are after the card is moved.
func Draw(hand []Card, deck []Card) (newHand []Card, newDeck []Card) {
	topCard := deck[0]
	newHand = append(hand, topCard)
	newDeck = deck[1:]
	return newHand, newDeck
}