path: root/internal/casino/blackjack.go

package casino

import (
	"fmt"
	"math"
	"math/rand"
	"strings"
	"sync"
)

type blackjackPhase string

const (
	blackjackWaiting   blackjackPhase = "waiting"
	blackjackBetting   blackjackPhase = "betting"
	blackjackInsurance blackjackPhase = "insurance"
	blackjackPlaying   blackjackPhase = "playing"
)

type blackjackHand struct {
	cards       []card
	bet         int
	fromSplit   bool
	doubled     bool
	stood       bool
	bust        bool
	surrendered bool
}

func (h *blackjackHand) total() (int, bool) {
	total, aces := 0, 0
	for _, c := range h.cards {
		total += c.blackjackValue()
		if c.rank == "A" {
			aces++
		}
	}
	for total > 21 && aces > 0 {
		total -= 10
		aces--
	}
	soft := aces > 0
	return total, soft
}

func (h *blackjackHand) blackjack(rules BlackjackConfig) bool {
	total, _ := h.total()
	return len(h.cards) == 2 && !h.fromSplit && total == 21 || rules.CountsDoubleSplitBlackjack() && h.fromSplit && h.doubled && total == 21
}

type blackjackPlayer struct {
	Participant
	hands             []*blackjackHand
	insurance         int
	declinedInsurance bool
	lastBet           int
}

func (p *blackjackPlayer) participantPtr() *Participant { return &p.Participant }

type blackjackTable struct {
	mu sync.Mutex
	tableBase
	Rules        BlackjackConfig
	players      seatSet[*blackjackPlayer]
	phase        blackjackPhase
	window       bettingWindow
	timer        countdown
	activePlayer int
	activeHand   int
	dealer       blackjackHand
	shoe         *shoe
}

func newBlackjackTable(roomID int, cfg TableConfig, rng *rand.Rand) *blackjackTable {
	cfg = cfg.Normalize()
	rules := cfg.Blackjack.Normalize()
	return &blackjackTable{
		tableBase: tableBase{RoomID: roomID, Config: cfg}, Rules: rules,
		players: newSeatSet[*blackjackPlayer](), phase: blackjackWaiting,
		shoe: newShoe(rules.Decks, rules.ShuffleAt, rng),
	}
}

func (t *blackjackTable) menuEvent(name string) Event {
	e := t.private(name, t.menu())
	e.Color = "casino_menu"
	e.Menu = &MenuView{Kind: MenuBlackjackBet, Commands: []MenuCommand{
		{Command: "bet", Desc: "Place a wager (min/max accepted)"},
		{Command: "bet <amount>", Desc: "Place a specific wager"},
		{Command: "stop", Desc: "Leave the table"},
	}}
	return e
}

func (t *blackjackTable) join(name string) []Event {
	t.mu.Lock()
	defer t.mu.Unlock()
	if t.players.has(name) {
		return []Event{t.menuEvent(name)}
	}
	if t.players.count() >= t.Config.MaxPlayers {
		return []Event{t.private(name, "That blackjack table is full.")}
	}
	t.players.add(name, &blackjackPlayer{Participant: Participant{Name: name, Connected: true}})
	events := []Event{t.playerAction(name, fmt.Sprintf("%s sits down.", name), "You sit down.")}
	events = append(events, t.menuEvent(name))
	return events
}

func (t *blackjackTable) leave(name string) []Event {
	t.mu.Lock()
	defer t.mu.Unlock()
	if !t.players.has(name) {
		return nil
	}
	if t.phase != blackjackWaiting {
		return []Event{t.private(name, "You're in the middle of a blackjack round!")}
	}
	t.players.remove(name)
	events := []Event{t.playerAction(name, fmt.Sprintf("%s stands up.", name), "You stand up.")}
	if t.players.count() == 0 {
		events = append(events, t.event("The blackjack table closes.", true))
	}
	return events
}

func (t *blackjackTable) bet(name, spot string, amount int, wallet Wallet) []Event {
	t.mu.Lock()
	defer t.mu.Unlock()
	p := t.players.get(name)
	if p == nil {
		return []Event{t.private(name, "You aren't playing blackjack.")}
	}
	if spot != "" {
		return []Event{t.private(name, "Blackjack bets don't take a bet target.")}
	}
	if t.phase != blackjackWaiting && t.phase != blackjackBetting {
		return []Event{t.private(name, "That blackjack table isn't accepting bets.")}
	}
	if p.HasBet {
		return []Event{t.private(name, "You have already bet this round.")}
	}
	if amount < t.Config.MinBet || amount > t.Config.MaxBet {
		return []Event{t.private(name, fmt.Sprintf("Blackjack bets must be between %d and %d.", t.Config.MinBet, t.Config.MaxBet))}
	}
	wager, ok := wallet.Wager(amount)
	if !ok {
		return []Event{t.private(name, "You don't have enough chips and credits for that bet.")}
	}
	p.HasBet, p.Wager, p.Wallet, p.lastBet = true, wager, wallet, amount
	events := []Event{t.playerAction(name, fmt.Sprintf("%s bets %d credits.", name, amount), fmt.Sprintf("You bet %d credits.", amount))}
	if t.players.count() > 1 && t.phase == blackjackWaiting {
		t.phase = blackjackBetting
		t.window.open(t.Config.BettingTicks)
		events = append(events, t.event(fmt.Sprintf("Blackjack betting is open for %d ticks.", t.Config.BettingTicks), true))
	}
	if allBet(t.players.participants()) {
		events = append(events, t.startRound()...)
	}
	return events
}

func (t *blackjackTable) tick() []Event {
	t.mu.Lock()
	defer t.mu.Unlock()
	switch t.phase {
	case blackjackBetting:
		sitOuts, resolve, pending := t.window.advance(t.players.participants())
		if pending {
			return nil
		}
		var events []Event
		for _, name := range sitOuts {
			events = append(events, t.event(fmt.Sprintf("%s sits out this blackjack round.", name), true))
		}
		if resolve {
			events = append(events, t.startRound()...)
		} else {
			t.resetRound()
		}
		return events
	case blackjackInsurance:
		if t.insuranceSettled() {
			return t.finishInsurance()
		}
		t.timer.tick()
		if !t.timer.expired() {
			return nil
		}
		return t.finishInsurance()
	case blackjackPlaying:
		name := t.activeName()
		if name == "" {
			return nil
		}
		active := t.players.get(name)
		if active == nil {
			// Unreachable while mid-round leaves are blocked; keep the game moving.
			t.activePlayer++
			return t.finishHand()
		}
		if active.Connected && t.bettorCount() <= 1 {
			// A lone connected player is never timed out. A disconnected
			// active player always is, so the table can never stall.
			return nil
		}
		t.timer.tick()
		if !t.timer.expired() {
			return nil
		}
		active.hands[t.activeHand].stood = true
		events := []Event{t.private(name, "Your action timed out; standing.")}
		events = append(events, t.finishHand()...)
		return events
	default:
		return nil
	}
}

func (t *blackjackTable) action(name, action string) []Event {
	t.mu.Lock()
	defer t.mu.Unlock()
	if t.phase == blackjackInsurance {
		return t.insuranceAction(name, action)
	}
	if t.phase != blackjackPlaying || t.activeName() != name {
		return []Event{t.private(name, "It's not your turn.")}
	}
	p := t.players.get(name)
	hand := p.hands[t.activeHand]
	t.timer.start(t.Rules.ActionTicks)
	switch action {
	case "hit":
		if fromSplitAces(hand) {
			return []Event{t.private(name, "Split aces cannot be hit.")}
		}
		hand.cards = append(hand.cards, t.shoe.draw())
		total, _ := hand.total()
		if total > 21 {
			hand.bust = true
		}
		e := t.playerAction(name, fmt.Sprintf("%s hits and receives %s.", name, hand.cards[len(hand.cards)-1]), fmt.Sprintf("You hit and receive %s.", hand.cards[len(hand.cards)-1]))
		e.Blackjack = t.snapshot(false)
		events := []Event{e}
		if total >= 21 {
			events = append(events, t.finishHand()...)
		} else {
			events = append(events, t.prompt()...)
		}
		return events
	case "stand":
		hand.stood = true
		return t.finishHand()
	case "double":
		if len(hand.cards) != 2 || hand.doubled || hand.surrendered || fromSplitAces(hand) || (hand.fromSplit && !t.Rules.AllowsDoubleAfterSplit()) {
			return []Event{t.private(name, "You can only double a qualifying hand.")}
		}
		if _, ok := p.Wallet.Wager(hand.bet); !ok {
			return []Event{t.private(name, "You don't have enough chips and credits to double that hand.")}
		}
		hand.bet *= 2
		hand.doubled = true
		hand.stood = true
		hand.cards = append(hand.cards, t.shoe.draw())
		if total, _ := hand.total(); total > 21 {
			hand.bust = true
		}
		e := t.playerAction(name, fmt.Sprintf("%s doubles down.", name), "You double down.")
		e.Blackjack = t.snapshot(false)
		return append([]Event{e}, t.finishHand()...)
	case "split":
		return t.splitHand(name, p, hand)
	case "surrender":
		if !t.Rules.AllowsSurrender() || hand.fromSplit || len(hand.cards) != 2 {
			return []Event{t.private(name, "Surrender is not available for this hand.")}
		}
		hand.surrendered = true
		return t.finishHand()
	default:
		return []Event{t.private(name, "Unknown blackjack action.")}
	}
}

// insuranceAction handles commands during the insurance offer window:
// "insurance" buys cover for half the base bet; any other action declines.
func (t *blackjackTable) insuranceAction(name, action string) []Event {
	p := t.players.get(name)
	if p == nil || !p.HasBet {
		return []Event{t.private(name, "Insurance is only offered to players with a bet this round.")}
	}
	if p.insurance > 0 || p.declinedInsurance {
		return []Event{t.private(name, "You have already decided about insurance.")}
	}
	var events []Event
	if action == "insurance" {
		amount := p.hands[0].bet / 2
		if amount <= 0 {
			return []Event{t.private(name, "Your bet is too small to insure.")}
		}
		if _, ok := p.Wallet.Wager(amount); !ok {
			return []Event{t.private(name, "You don't have enough chips and credits for insurance.")}
		}
		p.insurance = amount
		events = append(events, t.playerAction(name, fmt.Sprintf("%s takes insurance.", name), fmt.Sprintf("You place %d credits on insurance.", amount)))
	} else {
		p.declinedInsurance = true
		events = append(events, t.private(name, "You decline insurance."))
	}
	if t.insuranceSettled() {
		events = append(events, t.finishInsurance()...)
	}
	return events
}

// insuranceSettled reports whether every connected bettor has taken or
// declined insurance.
func (t *blackjackTable) insuranceSettled() bool {
	for _, p := range t.players.ordered() {
		if !p.HasBet || !p.Connected {
			continue
		}
		if p.insurance == 0 && !p.declinedInsurance {
			return false
		}
	}
	return true
}

// finishInsurance resolves the insurance window: a dealer blackjack settles
// the round immediately, otherwise play begins.
func (t *blackjackTable) finishInsurance() []Event {
	if t.dealerBlackjack() {
		return t.settle()
	}
	t.beginPlay()
	return t.finishHand()
}

func (t *blackjackTable) splitHand(name string, p *blackjackPlayer, hand *blackjackHand) []Event {
	if len(hand.cards) != 2 || len(p.hands) >= t.Rules.MaxSplitHands || !splitCompatible(hand.cards[0], hand.cards[1], t.Rules.AllowsUnlikeTenSplit()) {
		return []Event{t.private(name, "That hand cannot be split.")}
	}
	if hand.cards[0].rank == "A" && hand.fromSplit && !t.Rules.AllowsResplitAces() {
		return []Event{t.private(name, "Aces cannot be re-split at this table.")}
	}
	if _, ok := p.Wallet.Wager(hand.bet); !ok {
		return []Event{t.private(name, "You don't have enough chips and credits to split that hand.")}
	}
	left := &blackjackHand{cards: []card{hand.cards[0]}, bet: hand.bet, fromSplit: true}
	right := &blackjackHand{cards: []card{hand.cards[1]}, bet: hand.bet, fromSplit: true}
	left.cards = append(left.cards, t.shoe.draw())
	right.cards = append(right.cards, t.shoe.draw())
	index := t.activeHand
	p.hands = append(p.hands[:index], append([]*blackjackHand{left, right}, p.hands[index+1:]...)...)
	e := t.playerAction(name, fmt.Sprintf("%s splits the hand.", name), "You split the hand.")
	e.Blackjack = t.snapshot(false)
	events := []Event{e}
	if left.cards[0].rank == "A" {
		left.stood = !(t.Rules.AllowsResplitAces() && left.cards[1].rank == "A")
		right.stood = !(t.Rules.AllowsResplitAces() && right.cards[1].rank == "A")
		events = append(events, t.finishHand()...)
	} else {
		events = append(events, t.prompt()...)
	}
	return events
}

func splitCompatible(a, b card, unlikeTens bool) bool {
	if a.rank == b.rank {
		return true
	}
	return unlikeTens && a.blackjackValue() == 10 && b.blackjackValue() == 10
}

func (t *blackjackTable) startRound() []Event {
	t.dealer = blackjackHand{cards: []card{t.shoe.draw(), t.shoe.draw()}}
	for _, p := range t.players.ordered() {
		if !p.HasBet {
			continue
		}
		p.hands = []*blackjackHand{{cards: []card{t.shoe.draw(), t.shoe.draw()}, bet: p.Wager.Total}}
		if p.hands[0].bet/2 <= 0 {
			// A half-bet that rounds to zero cannot be insured.
			p.declinedInsurance = true
		}
	}
	roundEvent := t.event("", true)
	roundEvent.Blackjack = t.snapshot(false)
	events := []Event{roundEvent}
	if t.dealer.cards[1].rank == "A" {
		t.phase = blackjackInsurance
		t.timer.start(t.Rules.ActionTicks)
		events = append(events, t.event("The dealer shows an ace. Insurance is on offer.", true))
		for _, p := range t.players.ordered() {
			if !p.HasBet || !p.Connected || p.declinedInsurance {
				continue
			}
			events = append(events, t.private(p.Name, fmt.Sprintf("Insure your %d-credit bet for %d credits? Type \"insurance\" to buy, or any other action to decline.", p.hands[0].bet, p.hands[0].bet/2)))
		}
		if t.insuranceSettled() {
			events = append(events, t.finishInsurance()...)
		}
		return events
	}
	if t.dealerBlackjack() {
		events = append(events, t.settle()...)
		return events
	}
	t.beginPlay()
	return append(events, t.finishHand()...)
}

func (t *blackjackTable) beginPlay() {
	t.phase = blackjackPlaying
	t.timer.start(t.Rules.ActionTicks)
	t.activePlayer, t.activeHand = 0, 0
}

func (t *blackjackTable) prompt() []Event {
	name := t.activeName()
	if name == "" {
		return t.settle()
	}
	p := t.players.get(name)
	h := p.hands[t.activeHand]
	ranks := make([]string, len(h.cards))
	for i, card := range h.cards {
		ranks[i] = card.rank
	}
	actions := t.availableActions(p, h)
	e := t.private(name, fmt.Sprintf("Your turn (%s).\nActions: %s", strings.Join(ranks, ","), strings.Join(actions, ", ")))
	e.Color = "casino_menu"
	e.Menu = &MenuView{Kind: MenuBlackjackTurn, Title: fmt.Sprintf("Your turn (%s)", strings.Join(ranks, ",")), Actions: actions, Commands: blackjackActionCommands(actions)}
	return []Event{e}
}

func blackjackActionCommands(actions []string) []MenuCommand {
	descriptions := map[string]string{
		"hit":       "Take another card",
		"stand":     "Hold your total",
		"double":    "Double your bet and take one card",
		"split":     "Split your pair into two hands",
		"surrender": "Forfeit half your bet",
	}
	commands := make([]MenuCommand, 0, len(actions))
	for _, action := range actions {
		commands = append(commands, MenuCommand{Command: action, Desc: descriptions[action]})
	}
	return commands
}

func (t *blackjackTable) availableActions(p *blackjackPlayer, hand *blackjackHand) []string {
	if fromSplitAces(hand) {
		// Split aces receive one card each and may only be re-split.
		actions := []string{"stand"}
		if len(hand.cards) == 2 && len(p.hands) < t.Rules.MaxSplitHands && t.Rules.AllowsResplitAces() &&
			splitCompatible(hand.cards[0], hand.cards[1], t.Rules.AllowsUnlikeTenSplit()) {
			actions = append(actions, "split")
		}
		return actions
	}
	actions := []string{"hit", "stand"}
	if len(hand.cards) == 2 && !hand.doubled && (!hand.fromSplit || t.Rules.AllowsDoubleAfterSplit()) {
		actions = append(actions, "double")
	}
	if len(hand.cards) == 2 && len(p.hands) < t.Rules.MaxSplitHands && splitCompatible(hand.cards[0], hand.cards[1], t.Rules.AllowsUnlikeTenSplit()) &&
		!(hand.cards[0].rank == "A" && hand.fromSplit && !t.Rules.AllowsResplitAces()) {
		actions = append(actions, "split")
	}
	if t.Rules.AllowsSurrender() && !hand.fromSplit && len(hand.cards) == 2 {
		actions = append(actions, "surrender")
	}
	return actions
}

func fromSplitAces(hand *blackjackHand) bool {
	return hand.fromSplit && len(hand.cards) > 0 && hand.cards[0].rank == "A"
}

func (t *blackjackTable) finishHand() []Event {
	t.skipCompletedHands()
	if t.activeName() == "" {
		return t.settle()
	}
	return t.prompt()
}

func (t *blackjackTable) skipCompletedHands() {
	for t.activePlayer < t.players.count() {
		p := t.players.get(t.players.nameAt(t.activePlayer))
		if p == nil || !p.HasBet {
			t.activePlayer++
			t.activeHand = 0
			continue
		}
		for t.activeHand < len(p.hands) {
			h := p.hands[t.activeHand]
			total, _ := h.total()
			if h.stood || h.bust || h.surrendered || total >= 21 || h.blackjack(t.Rules) {
				t.activeHand++
				continue
			}
			return
		}
		t.activePlayer++
		t.activeHand = 0
	}
}

func (t *blackjackTable) activeName() string {
	return t.players.nameAt(t.activePlayer)
}

func (t *blackjackTable) dealerBlackjack() bool {
	return t.dealer.blackjack(t.Rules)
}

func (t *blackjackTable) settle() []Event {
	for {
		total, soft := t.dealer.total()
		if total > 17 || total == 17 && (!soft || !t.Rules.DealerHitsSoft17()) {
			break
		}
		t.dealer.cards = append(t.dealer.cards, t.shoe.draw())
	}
	dealerTotal, _ := t.dealer.total()
	dealerEvent := t.event("", true)
	dealerEvent.Blackjack = t.snapshot(true)
	events := []Event{dealerEvent}
	dealerBlackjack := t.dealerBlackjack()
	for _, p := range t.players.ordered() {
		if !p.HasBet {
			continue
		}
		for _, hand := range p.hands {
			result, payout := settleHand(hand, dealerTotal, dealerBlackjack, t.Rules)
			if payout > 0 && p.Wallet != nil {
				p.Wallet.PayCredits(payout)
			}
			publicResult, privateResult := blackjackResultMessages(p.Name, result, payout)
			settlement := t.playerAction(p.Name, publicResult, privateResult)
			if result == "blackjack" {
				settlement.Color = "casino_jackpot_win"
			} else if result == "win" {
				settlement.Color = "casino_big_win"
			}
			events = append(events, settlement)
		}
		if p.insurance > 0 {
			insurancePayout := 0
			if dealerBlackjack {
				insurancePayout = int(math.Floor(float64(p.insurance) * (1 + t.Rules.InsurancePayout)))
			}
			if insurancePayout > 0 {
				p.Wallet.PayCredits(insurancePayout)
			}
			events = append(events, t.private(p.Name, fmt.Sprintf("Insurance pays %d credits.", insurancePayout)))
		}
	}
	t.resetRound()
	for _, p := range t.players.ordered() {
		if p.Connected {
			events = append(events, t.menuEvent(p.Name))
		}
	}
	return events
}

func settleHand(hand *blackjackHand, dealerTotal int, dealerBlackjack bool, rules BlackjackConfig) (string, int) {
	total, _ := hand.total()
	if hand.surrendered {
		return "surrender", hand.bet / 2
	}
	if hand.bust {
		return "bust", 0
	}
	playerBlackjack := hand.blackjack(rules)
	if playerBlackjack && dealerBlackjack {
		return "push", hand.bet
	}
	if dealerBlackjack {
		return "dealer blackjack", 0
	}
	if playerBlackjack {
		// Winnings round down to whole credits; never bet less than two.
		return "blackjack", hand.bet + int(math.Floor(float64(hand.bet)*rules.BlackjackPayout))
	}
	if total > 21 || dealerTotal > total && dealerTotal <= 21 {
		return "loss", 0
	}
	if dealerTotal == total {
		return "push", hand.bet
	}
	if dealerTotal > 21 {
		return "win", hand.bet * 2
	}
	return "win", hand.bet * 2
}

func (t *blackjackTable) resetRound() {
	t.phase = blackjackWaiting
	t.window.close()
	t.timer.stop()
	for _, p := range t.players.ordered() {
		p.HasBet, p.Wager, p.hands, p.insurance, p.declinedInsurance = false, Wager{}, nil, 0, false
	}
}

func (t *blackjackTable) rebet(name string) (string, int) {
	if p := t.players.get(name); p != nil && p.lastBet > 0 {
		return "", p.lastBet
	}
	return "", t.Config.MinBet
}

func (t *blackjackTable) bettorCount() int {
	count := 0
	for _, p := range t.players.ordered() {
		if p.HasBet {
			count++
		}
	}
	return count
}

func (t *blackjackTable) snapshot(revealDealer bool) *BlackjackSnapshot {
	snapshot := &BlackjackSnapshot{}
	for i, card := range t.dealer.cards {
		if i == 0 && !revealDealer {
			snapshot.Dealer = append(snapshot.Dealer, CardView{Rank: "?", Hidden: true})
			continue
		}
		snapshot.Dealer = append(snapshot.Dealer, CardView{Rank: card.rank, Suit: card.suit})
	}
	for _, p := range t.players.ordered() {
		if !p.HasBet {
			continue
		}
		for _, hand := range p.hands {
			view := BlackjackPlayerView{Name: p.Name, Score: handScore(hand)}
			for _, card := range hand.cards {
				view.Cards = append(view.Cards, CardView{Rank: card.rank, Suit: card.suit})
			}
			snapshot.Players = append(snapshot.Players, view)
		}
	}
	if len(t.dealer.cards) > 1 {
		snapshot.DealerShownScore = handScore(&blackjackHand{cards: []card{t.dealer.cards[1]}})
	}
	snapshot.DealerScore = handScore(&t.dealer)
	snapshot.DealerRevealed = revealDealer
	return snapshot
}

func (t *blackjackTable) menu() string {
	return "New blackjack hand! Place your bet."
}

func handScore(hand *blackjackHand) string {
	total, soft := hand.total()
	if !soft || total == 21 {
		return fmt.Sprintf("%d", total)
	}
	return fmt.Sprintf("%d or %d", total-10, total)
}

func blackjackResultMessages(name, result string, payout int) (string, string) {
	switch result {
	case "win", "blackjack":
		return name + " wins!", fmt.Sprintf("You win! +%d credits", payout)
	case "push":
		return name + " pushes.", fmt.Sprintf("You push. +%d credits", payout)
	default:
		return name + " loses.", "You lose!"
	}
}

// markDisconnected removes the player from the table, forfeiting any wager
// they committed (settle only pays seated bettors). Removing a seat shifts
// the seat indices the active turn points into, so mid-round play is fixed
// up and handed to the next bettor (or settled) immediately.
func (t *blackjackTable) markDisconnected(name string) []Event {
	t.mu.Lock()
	defer t.mu.Unlock()
	index := t.players.indexOf(name)
	if index < 0 {
		return nil
	}
	t.players.remove(name)
	events := []Event{t.event(fmt.Sprintf("%s stands up.", name), true)}
	if t.players.count() == 0 {
		events = append(events, t.event("The blackjack table closes.", true))
	}
	if t.phase != blackjackPlaying {
		// Betting and insurance resolve against the remaining seats on the
		// next tick; waiting has no round in flight.
		return events
	}
	switch {
	case index < t.activePlayer:
		// The same player stays active, one seat earlier.
		t.activePlayer--
	case index == t.activePlayer:
		// The next bettor slides into the active seat.
		t.activeHand = 0
	}
	t.timer.start(t.Rules.ActionTicks)
	return append(events, t.finishHand()...)
}

func (t *blackjackTable) hasParticipant(name string) bool {
	t.mu.Lock()
	defer t.mu.Unlock()
	return t.players.has(name)
}