path: root/internal/casino/pai_gow_rules.go

package casino

import (
	"fmt"
	"sort"
	"strings"
	"unicode"
)

const (
	PaiGowClassic = "classic"
	PaiGowEZ      = "ez"
	PaiGowNoPush  = "no_push"
	PaiGowFaceUp  = "face_up"
	// Two independently funded wagers plus all five Envy bonuses must fit
	// MaxCredits. 2000 conservatively exceeds the maximum combined multiplier.
	pgMaxWager = MaxCredits / 2000
)

type PaiGowConfig struct {
	Variant     string `yaml:"variant,omitempty"`
	Envy        bool   `yaml:"envy,omitempty"`
	PushAceHigh string `yaml:"push_ace_high,omitempty"` // Face Up only: 5_15_40 or 5_12_40
	ActionTicks int    `yaml:"action_ticks,omitempty"`
	// A2345SecondHighest makes the wheel the second-highest straight, below
	// Broadway and above a six-high straight. It defaults to true; only an
	// explicit false demotes A2345 to the lowest straight.
	A2345SecondHighest *bool `yaml:"a2345_second_highest,omitempty"`
}

func (c PaiGowConfig) A2345High() bool { return ruleBool(c.A2345SecondHighest, true) }

func (c PaiGowConfig) Normalize() PaiGowConfig {
	if c.Variant == "" {
		c.Variant = PaiGowClassic
	}
	if c.ActionTicks == 0 {
		c.ActionTicks = 60
	}
	return c
}

// pushAceRates returns the three published rates (plain/joker/both) for a
// Face Up table's configured schedule; ok is false on any other value.
func (c PaiGowConfig) pushAceRates() ([3]int, bool) {
	switch c.Normalize().PushAceHigh {
	case "5_15_40":
		return [3]int{5, 15, 40}, true
	case "5_12_40":
		return [3]int{5, 12, 40}, true
	}
	return [3]int{}, false
}
func validatePaiGow(c TableConfig) error {
	r := c.PaiGow.Normalize()
	if c.MinBet > pgMaxWager {
		return fmt.Errorf("pai_gow min_bet must not exceed %d", pgMaxWager)
	}
	if r.Variant != PaiGowClassic && r.Variant != PaiGowEZ && r.Variant != PaiGowNoPush && r.Variant != PaiGowFaceUp {
		return fmt.Errorf("pai_gow variant must be classic, ez, no_push, or face_up")
	}
	if c.MaxPlayers > 6 {
		return fmt.Errorf("pai gow allows at most six players")
	}
	if r.ActionTicks < 1 || r.ActionTicks > 600 {
		return fmt.Errorf("pai_gow action_ticks must be 1-600")
	}
	if r.PushAceHigh != "" {
		if r.Variant != PaiGowFaceUp {
			return fmt.Errorf("push_ace_high belongs on a face_up table")
		}
		if _, ok := r.pushAceRates(); !ok {
			return fmt.Errorf("push_ace_high must be 5_15_40 or 5_12_40")
		}
	}
	if r.Variant == PaiGowFaceUp && r.PushAceHigh == "" {
		return fmt.Errorf("face_up requires push_ace_high 5_15_40 or 5_12_40")
	}
	return nil
}
func (c PaiGowConfig) Label() string {
	switch c.Normalize().Variant {
	case PaiGowEZ:
		return "EZ Pai Gow Poker"
	case PaiGowNoPush:
		return "No Push Pai Gow Poker"
	case PaiGowFaceUp:
		return "Face Up Pai Gow Poker"
	}
	return "Pai Gow Poker"
}
func paiGowRules(c TableConfig) string {
	r := c.PaiGow.Normalize()
	wheel := "A2345 is the second-highest straight."
	if !r.A2345High() {
		wheel = "A2345 is the lowest straight."
	}
	s := r.Label() + "\nSeven cards from a fresh 53-card deck. Joker is an ace unless completing a straight, flush or straight flush. " + wheel + "\nSet two cards low and five high: 24 chooses low cards 2/4; 13456 chooses the high hand. High must strictly outrank low. Copies go to the dealer.\nBoth hands win: win; both lose: loss; one wins: push."
	switch r.Variant {
	case PaiGowClassic:
		s += " Wins pay 0.95:1 (profit rounded down, minimum one credit)."
	case PaiGowEZ:
		s += " No commission; dealer's best five-card hand exactly queen-high pushes all main bets."
	case PaiGowFaceUp:
		s += " No commission; dealer sets and reveals both hands before you set yours. Dealer's best five-card hand exactly ace-high automatically pushes all main bets; Fortune and Envy still settle."
	case PaiGowNoPush:
		s += " No commission; split results use two extra cards: player must beat dealer, ties lose; Joker is ace."
	}
	s += "\nHouse way: preserve the best high-hand category, maximize low within it; split two pair, full houses and trips-pairs when this improves low to a pair. Never foul. Use house or set <digits>; set locks your hand. Timeout/disconnect uses house way.\nBet main first, optionally bet <amount> fortune before dealing. Fortune uses all seven cards regardless of split; highest listed prize only, profit odds plus stake returned."
	if r.Envy {
		s += "\nEnvy: Fortune stake of at least 5 qualifies for fixed bonuses on OTHER active players' hands, never your own or dealer; multiple bonuses add."
	} else {
		s += "\nEnvy off: four of a kind pays 30:1 instead of 25:1 (custom enhancement)."
	}
	return s
}

// ParsePaiGowDigits accepts exactly two or five UNIQUE card positions; unlike
// video poker toggles, repeated digits are an error rather than silently ignored.
func ParsePaiGowDigits(s string) ([]int, bool) {
	var out []int
	var seen [7]bool
	for _, r := range s {
		if unicode.IsSpace(r) {
			continue
		}
		if r < '1' || r > '7' || seen[r-'1'] {
			return nil, false
		}
		seen[r-'1'] = true
		out = append(out, int(r-'1'))
	}
	return out, len(out) == 2 || len(out) == 5
}

// Lexicographic category and kickers. Zero padding permits comparisons between
// five and two cards without treating a two-card flush/straight as a hand.
type pgRank [6]int

func pgCompare(a, b pgRank) int {
	for i := range a {
		if a[i] > b[i] {
			return 1
		}
		if a[i] < b[i] {
			return -1
		}
	}
	return 0
}
// pgNatural keeps the default-rules entry point used by tests and callers that
// do not thread a table configuration. Production evaluation goes through
// pgNaturalRules.
//
//nolint:unused // default-rules entry point
func pgNatural(cards []card) pgRank { return pgNaturalRules(cards, true) }

func pgNaturalRules(cards []card, a2345High bool) pgRank {
	counts := [15]int{}
	flush := len(cards) == 5
	for _, c := range cards {
		counts[pokerRank(c)]++
		if c.suit != cards[0].suit {
			flush = false
		}
	}
	var ranks []int
	for r := 14; r >= 2; r-- {
		if counts[r] > 0 {
			ranks = append(ranks, r)
		}
	}
	sort.SliceStable(ranks, func(i, j int) bool { return counts[ranks[i]] > counts[ranks[j]] })
	straight := 0
	if len(cards) == 5 && len(ranks) == 5 {
		sorted := append([]int(nil), ranks...)
		sort.Ints(sorted)
		if sorted[4]-sorted[0] == 4 {
			straight = sorted[4]
		}
		if sorted[0] == 2 && sorted[1] == 3 && sorted[2] == 4 && sorted[3] == 5 && sorted[4] == 14 {
			if a2345High {
				straight = 15
			} else {
				straight = 5
			}
		}
		if straight == 14 {
			straight = 16
		}
	}
	out := pgRank{}
	switch {
	case counts[ranks[0]] == 5:
		out[0] = 9
	case straight > 0 && flush:
		out[0] = 8
		out[1] = straight
		return out
	case counts[ranks[0]] == 4:
		out[0] = 7
	case len(ranks) > 1 && counts[ranks[0]] == 3 && counts[ranks[1]] == 2:
		out[0] = 6
	case flush:
		out[0] = 5
	case straight > 0:
		out[0] = 4
		out[1] = straight
		return out
	case counts[ranks[0]] == 3:
		out[0] = 3
	case len(ranks) > 1 && counts[ranks[0]] == 2 && counts[ranks[1]] == 2:
		out[0] = 2
	case counts[ranks[0]] == 2:
		out[0] = 1
	}
	copy(out[1:], ranks)
	return out
}
func pgEvaluate(cards []card) pgRank { return pgEvaluateRules(cards, true) }

func pgEvaluateRules(cards []card, a2345High bool) pgRank {
	j := -1
	for i, c := range cards {
		if c.rank == "JK" {
			j = i
			break
		}
	}
	if j < 0 {
		return pgNaturalRules(cards, a2345High)
	}
	copyCards := append([]card(nil), cards...)
	copyCards[j] = card{"A", "joker"}
	best := pgNaturalRules(copyCards, a2345High)
	if len(cards) != 5 {
		return best
	}
	for _, s := range []string{"clubs", "diamonds", "hearts", "spades"} {
		for _, r := range []string{"2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"} {
			replacement := card{r, s}
			duplicate := false
			for i, c := range cards {
				if i != j && c == replacement {
					duplicate = true
				}
			}
			if duplicate {
				continue
			}
			copyCards[j] = replacement
			v := pgNaturalRules(copyCards, a2345High)
			if (v[0] == 4 || v[0] == 5 || v[0] == 8) && pgCompare(v, best) > 0 {
				best = v
			}
		}
	}
	return best
}

type pgSplit struct{ high, low []card }

func pgSet(cards []card, digits []int) pgSplit {
	var selected [7]bool
	for _, i := range digits {
		selected[i] = true
	}
	s := pgSplit{}
	for i, c := range cards {
		if selected[i] == (len(digits) == 2) {
			s.low = append(s.low, c)
		} else {
			s.high = append(s.high, c)
		}
	}
	return s
}
func (s pgSplit) valid() bool { return s.validRules(true) }

func (s pgSplit) validRules(a2345High bool) bool {
	return len(s.high) == 5 && len(s.low) == 2 && pgCompare(pgEvaluateRules(s.high, a2345High), pgEvaluateRules(s.low, a2345High)) > 0
}
func pgHouse(cards []card) pgSplit { return pgHouseRules(cards, true) }

func pgHouseRules(cards []card, a2345High bool) pgSplit {
	var options []pgSplit
	best := pgRank{}
	for i := 0; i < 7; i++ {
		for j := i + 1; j < 7; j++ {
			s := pgSet(cards, []int{i, j})
			if !s.validRules(a2345High) {
				continue
			}
			options = append(options, s)
			if pgCompare(pgEvaluateRules(s.high, a2345High), best) > 0 {
				best = pgEvaluateRules(s.high, a2345High)
			}
		}
	}
	var chosen pgSplit
	var low, high pgRank
	for _, s := range options {
		h, l := pgEvaluateRules(s.high, a2345High), pgEvaluateRules(s.low, a2345High)
		eligible := h[0] == best[0]
		// Split two pair/full house only for a paired front with at least a pair behind.
		if (best[0] == 2 || best[0] == 6) && l[0] == 1 && h[0] >= 1 {
			eligible = true
		}
		if !eligible {
			continue
		}
		if chosen.high == nil || pgCompare(l, low) > 0 || pgCompare(l, low) == 0 && pgCompare(h, high) > 0 {
			chosen, low, high = s, l, h
		}
	}
	return chosen
}

type FortuneRow struct {
	Hand       string
	Odds, Envy int
}

// Wizard of Odds Fortune table 8, the lowest-edge published fixed schedule
// among its eight tables. With Envy disabled, quads receive a custom +5.
func FortunePayTable(envy bool) []FortuneRow {
	rows := []FortuneRow{{"Natural seven-card straight flush", 1000, 500}, {"Royal flush + royal match", 750, 250}, {"Wild seven-card straight flush", 500, 150}, {"Five aces", 250, 100}, {"Royal flush", 150, 50}, {"Straight flush", 50, 20}, {"Four of a kind", 25, 5}, {"Full house", 5, 0}, {"Flush", 4, 0}, {"Three of a kind", 3, 0}, {"Straight", 2, 0}, {"Three pair", 1, 0}}
	if !envy {
		rows[6].Odds = 30
		for i := range rows {
			rows[i].Envy = 0
		}
	}
	return rows
}
func pgSevenFlush(cards []card) bool {
	suit := ""
	counts := [15]int{}
	wild := 0
	for _, c := range cards {
		if c.rank == "JK" {
			wild++
			continue
		}
		if suit == "" {
			suit = c.suit
		}
		if suit != c.suit {
			return false
		}
		counts[pokerRank(c)]++
	}
	for high := 7; high <= 14; high++ {
		missing := 0
		for r := high - 6; r <= high; r++ {
			v := r
			if v == 1 {
				v = 14
			}
			if counts[v] == 0 {
				missing++
			}
		}
		if missing == wild {
			return true
		}
	}
	return false
}
func pgFortune(cards []card, envy bool) (FortuneRow, bool) { return pgFortuneRules(cards, envy, true) }

func pgFortuneRules(cards []card, envy, a2345High bool) (FortuneRow, bool) {
	rows := FortunePayTable(envy)
	joker := false
	counts := [15]int{}
	for _, c := range cards {
		if c.rank == "JK" {
			joker = true
			counts[14]++
		} else {
			counts[pokerRank(c)]++
		}
	}
	if pgSevenFlush(cards) && !joker {
		return rows[0], true
	}
	bestIndex := len(rows)
	// Enumerate all 21 five-card subsets. Fortune ranks trips above straights,
	// so choose by pay-table priority, NOT conventional poker rank.
	for i := 0; i < 7; i++ {
		for j := i + 1; j < 7; j++ {
			s := pgSet(cards, []int{i, j})
			v := pgEvaluateRules(s.high, a2345High)
			index := len(rows)
			switch v[0] {
			case 9:
				index = 3
			case 8:
				if v[1] == 16 {
					index = 4
					if s.low[0].suit == s.low[1].suit && (s.low[0].rank == "K" && s.low[1].rank == "Q" || s.low[0].rank == "Q" && s.low[1].rank == "K") {
						index = 1
					}
				} else {
					index = 5
				}
			case 7:
				index = 6
			case 6:
				index = 7
			case 5:
				index = 8
			case 3:
				index = 9
			case 4:
				index = 10
			}
			if index < bestIndex {
				bestIndex = index
			}
		}
	}
	if joker && pgSevenFlush(cards) && bestIndex > 2 {
		bestIndex = 2
	}
	pairs := 0
	for _, n := range counts {
		if n >= 2 {
			pairs++
		}
	}
	if pairs >= 3 && bestIndex > 11 {
		bestIndex = 11
	}
	if bestIndex == len(rows) {
		return FortuneRow{Hand: "No Fortune win"}, false
	}
	return rows[bestIndex], true
}
// pgBest keeps the default-rules entry point used by tests and callers that do
// not thread a table configuration. Production evaluation goes through
// pgBestRules.
//
//nolint:unused // default-rules entry point
func pgBest(cards []card) pgRank { return pgBestRules(cards, true) }

func pgBestRules(cards []card, a2345High bool) pgRank {
	var best pgRank
	for i := 0; i < 7; i++ {
		for j := i + 1; j < 7; j++ {
			v := pgEvaluateRules(pgSet(cards, []int{i, j}).high, a2345High)
			if pgCompare(v, best) > 0 {
				best = v
			}
		}
	}
	return best
}

// Automatic pushes use the best of all seven dealer cards, not just the
// chosen high hand. Pair/straight/flush hands headed by an ace do not qualify.
func pgDealerPush(cards []card, variant string) string {
	return pgDealerPushRules(cards, variant, true)
}

func pgDealerPushRules(cards []card, variant string, a2345High bool) string {
	if variant != PaiGowEZ && variant != PaiGowFaceUp {
		return ""
	}
	v := pgBestRules(cards, a2345High)
	if v[0] == 0 {
		if variant == PaiGowEZ && v[1] == 12 {
			return "push (dealer queen-high)"
		}
		if variant == PaiGowFaceUp && v[1] == 14 {
			return "push (dealer ace-high)"
		}
	}
	return ""
}
func pgMainResult(player, dealer pgSplit, dealerCards []card, variant string, tie [2]card) string {
	return pgMainResultRules(player, dealer, dealerCards, variant, tie, true)
}

func pgMainResultRules(player, dealer pgSplit, dealerCards []card, variant string, tie [2]card, a2345High bool) string {
	if push := pgDealerPushRules(dealerCards, variant, a2345High); push != "" {
		return push
	}
	high := pgCompare(pgEvaluateRules(player.high, a2345High), pgEvaluateRules(dealer.high, a2345High)) > 0
	low := pgCompare(pgEvaluateRules(player.low, a2345High), pgEvaluateRules(dealer.low, a2345High)) > 0
	if high && low {
		return "win"
	}
	if !high && !low {
		return "loss"
	}
	if variant == PaiGowNoPush {
		rank := func(c card) int {
			if c.rank == "JK" {
				return 14
			}
			return pokerRank(c)
		}
		if rank(tie[0]) > rank(tie[1]) {
			return "win (tiebreaker)"
		}
		return "loss (tiebreaker)"
	}
	return "push"
}

// pgPushAceClass resolves Face Up's optional Push Ace High side bet.
// The dealer's seven cards decide the base event at reveal time; ace-high
// with a Joker pays 15:1, without a Joker 5:1, and both sides ace-high 40:1
type pgPushAce struct {
	klass string // "both", "joker", "plain", or "none"
	rate  int
	desc  string
}

func pgPushAceClass(dealer, player []card, rates [3]int) pgPushAce {
	return pgPushAceClassRules(dealer, player, rates, true)
}

func pgPushAceClassRules(dealer, player []card, rates [3]int, a2345High bool) pgPushAce {
	if pgBestRules(dealer, a2345High)[0] != 0 || pgBestRules(dealer, a2345High)[1] != 14 {
		return pgPushAce{klass: "none"}
	}
	for _, c := range dealer {
		if c.rank == "JK" {
			return pgPushAce{klass: "joker", rate: rates[1], desc: "dealer ace-high with Joker"}
		}
	}
	if pgBestRules(player, a2345High)[0] == 0 && pgBestRules(player, a2345High)[1] == 14 {
		return pgPushAce{klass: "both", rate: rates[2], desc: "both ace-high"}
	}
	return pgPushAce{klass: "plain", rate: rates[0], desc: "dealer ace-high without Joker"}
}

func pgMainPay(stake int, result, variant string) int {
	if strings.HasPrefix(result, "push") {
		return stake
	}
	if !strings.HasPrefix(result, "win") {
		return 0
	}
	if variant == PaiGowClassic {
		return stake + max(1, stake*95/100)
	}
	return stake * 2
}