commit 9cfa4b826cec1df11276d5432173704b3f18f946
Author: joshua <joshua@clement.tel>
Date:   Mon Jul 24 16:44:40 2023 +0200

    Init

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..981fc65
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.clement.tel/joshua/09_deck
+
+go 1.20
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..e69de29
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..81550d8
--- /dev/null
+++ b/main.go
@@ -0,0 +1,214 @@
+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
+}
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..628a0ed
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,129 @@
+package deck
+
+import (
+	"testing"
+	"fmt"
+)
+
+func showDeck(d []Card) {
+	fmt.Println("Showing whole deck")
+	for _, card := range d {
+		fmt.Println(card)
+	}
+}
+
+func TestPrintCard(t *testing.T) {
+	tests := []struct{
+		input Card
+		want string
+	}{
+		{Card{Hearts, Queen}, "Queen of Hearts"},
+		{Card{Suit: Joker}, "Joker"},
+	}
+	for _, test := range tests {
+		if test.input.String() != test.want {
+			t.Errorf("Got %s; wanted %s", test.input.String(), test.want)
+		}
+	}
+}
+
+func TestNew(t *testing.T) {
+	d := New()
+	c := Card{Diamonds, Six}
+	if d[18] != c {
+		t.Errorf("Deck's 5th card should be %s, is %s", c, d[18])
+		showDeck(d)
+	}
+}
+
+func TestSortByRank(t *testing.T) {
+	d := New(SortByRank)
+	c := Card{Clubs, Five}
+	if d[18] != c {
+		t.Errorf("Deck's 18th card should be %s, is %s", c, d[18])
+		showDeck(d)
+	}
+}
+
+func TestSortBySuit(t *testing.T) {
+	d := New()
+	d = SortByRank(d)
+	d = SortBySuit(d)
+	c := Card{Diamonds, Six}
+	if d[18] != c {
+		t.Errorf("Deck's 5th card should be %s, is %s", c, d[18])
+		showDeck(d)
+	}
+}
+
+func TestAddJokers(t *testing.T) {
+	d := New()
+	initLength := len(d)
+	d = AddNJokers(17)(d)
+	if initLength + 17 != len(d) {
+		t.Errorf("Wrong number of cards in deck after adding Jokers")
+		showDeck(d)
+	}
+}
+
+func TestRemoveCard(t *testing.T) {
+	d := New(RemoveCards(Card{Spades, Ace}))
+	for _, card := range d {
+		if card == (Card{Spades, Ace}) {
+			t.Error("The ace of spades is still in the deck after calling RemoveCard(Card{Spades, Ace})")
+		}
+	}
+	before := len(d)
+	d = RemoveCards(Card{Clubs, Jack})(d)
+	if len(d) != (before - 1) {
+		t.Error("Remove() didn't reduce card count by 1")
+	}
+}
+
+func TestRemoveRank(t *testing.T) {
+	d := New(RemoveRank(Seven))
+	for _, card := range d {
+		if card.Rank == Seven {
+			t.Error("There are still Sevens in the deck after calling RemoveRank(7)")
+		}
+	}
+}
+
+func TestRemoveSuit(t *testing.T) {
+	d := New(RemoveSuit(Hearts))
+	for _, card := range d {
+		if card.Suit == Hearts {
+			t.Error("There are still Hearts in the deck after calling RemoveSuit(Hearts)")
+		}
+	}
+}
+
+func TestAddDeck(t *testing.T) {
+	d := New()
+	before := len(d)
+	d = AddDeck(d)
+	if len(d) != before*2 {
+		t.Error("AddDeck didn't double default deck size")
+	}
+}
+
+func TestDraw(t *testing.T) {
+	d := New()
+	lenBefore := len(d)
+	firstTwo := d[0:2]
+	hand := make([]Card, 0, 5)
+	hand, d = Draw(hand, d)
+	hand, d = Draw(hand, d)
+	if firstTwo[0] != hand[0] {
+		t.Errorf("The first drawn card (got %s) should be the first in the deck (was %s)\n",
+		hand[0], firstTwo[0])
+	}
+	if firstTwo[1] != hand[1] {
+		t.Errorf("The second drawn card (got %s) should be the second in the deck (was %s)\n",
+			hand[0], firstTwo[0])
+	}
+	if len(d) != lenBefore - 2 {
+		t.Errorf(`Expected length of deck to be reduced by two when calling Draw() twice,
+length before is %d, and length after is %d`, lenBefore, len(d))
+	}
+}
diff --git a/suit_string.go b/suit_string.go
new file mode 100644
index 0000000..48da3ac
--- /dev/null
+++ b/suit_string.go
@@ -0,0 +1,57 @@
+// Code generated by "stringer -type=Suit,Rank"; DO NOT EDIT.
+
+package deck
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[Spades-0]
+	_ = x[Diamonds-1]
+	_ = x[Clubs-2]
+	_ = x[Hearts-3]
+	_ = x[Joker-4]
+}
+
+const _Suit_name = "SpadesDiamondsClubsHeartsJoker"
+
+var _Suit_index = [...]uint8{0, 6, 14, 19, 25, 30}
+
+func (i Suit) String() string {
+	if i >= Suit(len(_Suit_index)-1) {
+		return "Suit(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _Suit_name[_Suit_index[i]:_Suit_index[i+1]]
+}
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[Ace-1]
+	_ = x[Two-2]
+	_ = x[Three-3]
+	_ = x[Four-4]
+	_ = x[Five-5]
+	_ = x[Six-6]
+	_ = x[Seven-7]
+	_ = x[Eight-8]
+	_ = x[Nine-9]
+	_ = x[Ten-10]
+	_ = x[Jack-11]
+	_ = x[Queen-12]
+	_ = x[King-13]
+}
+
+const _Rank_name = "AceTwoThreeFourFiveSixSevenEightNineTenJackQueenKing"
+
+var _Rank_index = [...]uint8{0, 3, 6, 11, 15, 19, 22, 27, 32, 36, 39, 43, 48, 52}
+
+func (i Rank) String() string {
+	i -= 1
+	if i >= Rank(len(_Rank_index)-1) {
+		return "Rank(" + strconv.FormatInt(int64(i+1), 10) + ")"
+	}
+	return _Rank_name[_Rank_index[i]:_Rank_index[i+1]]
+}