super-auto-pets-board-game/internal/game/battle.go

package game

import (
	"fmt"
	"slices"
)

// BattleUnit is a pet in play with its attached foods applied. Power
// (attack) is unaffected by damage; a unit dies when Damage >= Power.
type BattleUnit struct {
	Card   Card   `json:"card"`
	Foods  []Card `json:"foods,omitempty"`
	Bonus  int    `json:"bonus"`  // total power added by foods, eating, auras
	Damage int    `json:"damage"` // damage markers accumulated this battle
	// Shields are this pet's own full-hit blocks, newest last. Each carries
	// its source so the log can name it (Gorilla's innate block, or a Melon
	// perk) and the client can drop the spent card.
	Shields []shieldCharge
	// afterAttackUsed gates once-per-battle After-Attack effects (Bulldog).
	afterAttackUsed bool
	// hitPrevent are this pet's own one-shot partial damage preventions
	// (Potato perk: two charges of 2). Consumed before any side-level charge.
	hitPrevent []int
}

// shieldCharge is one full-hit block a pet carries. source is the granting
// item's display name (e.g. "Melon"); an empty source is the pet's own innate
// shield (Gorilla). card, when set, is the food to remove from the play area
// once the charge is spent.
type shieldCharge struct {
	source string
	card   *Card
}

// shieldBlock describes a hit that a shield just absorbed, for the caller to
// narrate and clean up: source names the shield (empty = innate), and release
// is the field card to remove — a Melon food or a set-aside Turtle — or nil.
type shieldBlock struct {
	source  string
	release *Card
}

// preventInfo describes a partial damage prevention a hit just consumed (Cone
// Snail): amount is the damage shaved off, release is the set-aside card to
// remove from the board. The caller narrates it after its own hit event so the
// replay order stays correct.
type preventInfo struct {
	amount  int
	release *Card
}

func (u *BattleUnit) Power() int  { return u.Card.Power + u.Bonus }
func (u *BattleUnit) Alive() bool { return u.Damage < u.Power() }

// activePerk returns the perk this unit benefits from: only the
// last-applied perk counts when several are attached.
func (u *BattleUnit) activePerk() *Card {
	for i := len(u.Foods) - 1; i >= 0; i-- {
		if u.Foods[i].Perk {
			return &u.Foods[i]
		}
	}
	return nil
}

// effects returns the unit's live effects: its own plus its active perk's.
func (u *BattleUnit) effects() []Effect {
	effs := u.Card.Effects
	if perk := u.activePerk(); perk != nil {
		effs = append(append([]Effect(nil), effs...), perk.Effects...)
	}
	return effs
}

// prevention totals the unit's passive per-attack damage reduction (Garlic).
func (u *BattleUnit) prevention() int {
	total := 0
	for _, e := range u.effects() {
		if e.Trigger == TriggerPassive && e.Action == ActionPreventDamage {
			total += e.count()
		}
	}
	return total
}

// hasKnockout reports whether the unit's clash attacks KO (Scorpion).
func (u *BattleUnit) hasKnockout() bool {
	for _, e := range u.effects() {
		if e.Trigger == TriggerPassive && e.Action == ActionKnockout {
			return true
		}
	}
	return false
}

// appleCount counts apples among the given foods.
func appleCount(foods []Card) int {
	n := 0
	for _, f := range foods {
		if f.Food == FoodApple {
			n++
		}
	}
	return n
}

// isBee reports whether a card is a summoned Bee.
func isBee(c Card) bool { return c.IsPet() && c.Name == "Bee" }

// BattleEvent is one step of the battle, in order, for clients to animate.
type BattleEvent struct {
	// "prep":   Card starts the battle already in play for Seat (Monkey).
	// "reveal": Seat flipped Card off their stack (food or pet).
	// "summon": an effect put Card on top of Seat's stack.
	// "mill":   Card was discarded off the top of Seat's stack (Chili).
	// "rock":   Seat's pet threw rocks at Target's pet in play.
	// "clash":  the pets in play traded blows.
	// "shield": Seat's pet blocked a hit entirely.
	// "strip":  Seat's pet discarded all of Target's pet's foods (Skunk).
	// "steal":  Seat's pet stole Count apples from Target's pet (Wolverine).
	// "eat":    Seat's pet ate apples; Bonus is its new total.
	// "heal":   Seat's pet healed; DamageAfter is its new damage total.
	// "setaside": Card (a fainted pet) enters Seat's set-aside zone with a
	//           pending effect (Blowfish, Badger, Snake, Crocodile, Turtle,
	//           Turkey, Mammoth).
	// "release":  a set-aside Card left Seat's zone, its effect consumed
	//           (matched by Card.ID).
	Type string `json:"type"`
	// Seat/Target must NOT be omitempty: 0 is a valid seat (the first
	// player) and dropping it makes the client read sides[undefined].
	Seat   int   `json:"seat"`
	Target int   `json:"target"`
	Card   *Card `json:"card,omitempty"`
	Count  int   `json:"count,omitempty"`
	// clash: per-seat damage totals / deaths after the exchange.
	Damage []int  `json:"damage,omitempty"`
	Died   []bool `json:"died,omitempty"`
	// rock: individual die faces rolled (each 0, 1, or 2), for the dice
	// animation; Roll is their sum.
	Dice []int `json:"dice,omitempty"`
	// rock: dice total rolled; rock/strip/steal: target pet's fate.
	Roll        int  `json:"roll"`
	DamageAfter int  `json:"damageAfter"`
	TargetDied  bool `json:"targetDied,omitempty"`
	// eat: the pet's power bonus after eating.
	Bonus int `json:"bonus"`
	// Text is a human-readable description of this step for the event log,
	// e.g. "Ant's faint effect summons a Bee." Empty for steps not worth a
	// line (they still animate).
	Text string `json:"text,omitempty"`
}

// BattleResult is the full, public record of one round's battle.
type BattleResult struct {
	Round      int   `json:"round"`
	StackSizes []int `json:"stackSizes"` // starting deck size per seat
	// Lineups is each seat's arranged deck at battle start (top of deck
	// first). Public so players can review the whole matchup — including the
	// opponent's cards — during and after the fight.
	Lineups    [][]Card      `json:"lineups,omitempty"`
	Events     []BattleEvent `json:"events"`
	WinnerSeat int           `json:"winnerSeat"` // -1 = draw
	Trophies   int           `json:"trophies"`   // awarded to the winner
}

// setAsideRocks is a fainted pet's pending rock payout.
type setAsideRocks struct {
	dice     int
	everyone bool // Badger: hits every active pet, the owner's own included
	src      Card // the fainted pet, for the set-aside display
}

// lastPetVolley is Crocodile's set-aside: rocks that fire when the enemy plays
// the last pet in their deck.
type lastPetVolley struct {
	dice int
	src  Card // the fainted pet, for the set-aside display
}

// feedAside is Giant Isopod's set-aside: each time the owner plays a pet, spend
// one Trumpet to feed that pet `apples` apples.
type feedAside struct {
	apples int
	src    Card // the fainted pet, for the set-aside display
}

// battleSide is one seat's live state during the simulation.
type battleSide struct {
	stack       []Card // remaining face-down cards, top first
	pending     []Card // foods revealed (or prepped) waiting for a pet
	unit        *BattleUnit
	beesFainted int // friendly bees fainted so far (Dog)
	petsFainted int // friendly pets fainted so far (Shark)
	shields     int // Turtle charges: next friendly hit fully prevented
	beeBonus    int // Turkey aura: +power for later friendly bees
	petBonus    int // Mammoth aura: +power for later friendly pets

	oneShotRocks   []setAsideRocks // Badger/Blowfish: on next own pet play
	recurringRocks []setAsideRocks // Snake: on every own pet play
	lastPetRocks   []lastPetVolley // Crocodile: when the enemy plays their last pet
	shieldCards    []Card          // Turtle set-aside cards, parallel to shields

	// --- Golden pack ---
	trumpets     int           // ephemeral Trumpet pool (earned/spent in battle)
	faintedHats  map[Suit]bool // distinct suits among friendly fainted pets (Honduran White Bat)
	grSummoned   bool          // Golden Retriever already summoned this battle
	hitPrevent   []int         // Cone Snail: pending one-shot partial damage preventions
	preventCards []Card        // Cone Snail set-aside cards, parallel to hitPrevent
	beePlayRocks    []setAsideRocks // Poison Dart Frog: rocks each time a Bee is played
	feedOnPlay      []feedAside     // Giant Isopod: feed apples on each pet played
	petsPlayed      int             // pets fielded so far (Komodo's "first pet")
	retrieverGuards []int           // German Shepherd: damage the Golden Retriever prevents on its first hits
}

// hasPetInStack reports whether any pet remains face-down in the stack.
func (s *battleSide) hasPetInStack() bool {
	for _, c := range s.stack {
		if c.IsPet() {
			return true
		}
	}
	return false
}

// canField reports whether the side has, or can still produce, a pet to fight:
// one in play, a pet left in the stack, or a Golden Retriever waiting to be
// summoned. Used to decide the battle is over only after play effects (and any
// parting shots) have resolved.
func (s *battleSide) canField() bool {
	if s.unit != nil || s.hasPetInStack() {
		return true
	}
	return len(s.stack) == 0 && s.trumpets > 0 && !s.grSummoned
}

// queuedPlay is a play-time effect waiting to resolve after reveals.
type queuedPlay struct {
	seat     int
	unit     *BattleUnit // the unit whose play queued this; nil for set-asides
	effect   Effect
	everyone bool  // rock volley hits every active pet (Badger)
	release  *Card // set-aside card to release once this play resolves (Blowfish/Badger/Croc)
	source   *Card // set-aside pet credited as the effect's source (Blowfish/Badger/Croc/Snake)
}

// effectCount resolves an effect's final count: base × Per statistic,
// limited by Cap. enemy is the opposing side (for enemy-relative multipliers);
// it may be nil when the effect has no such Per.
func effectCount(e Effect, s *battleSide, u *BattleUnit, enemy *battleSide) int {
	n := e.count()
	switch e.Per {
	case PerFaintedBees:
		n *= s.beesFainted
	case PerFaintedPets:
		n *= s.petsFainted
	case PerEatenApples:
		n *= appleCount(u.Foods)
	case PerPower:
		n *= u.Power()
	case PerUniqueFaintedHats:
		n *= len(s.faintedHats)
	case PerEnemyFaintedPets:
		if enemy != nil {
			n *= enemy.petsFainted
		} else {
			n = 0
		}
	}
	if e.Cap > 0 && n > e.Cap {
		n = e.Cap
	}
	return n
}

// resolveBattle simulates the battle from the players' arranged decks,
// records the event log, awards trophies, and moves to PhaseBattle.
//
// The battle is a stack machine: each side reveals cards off the top of
// their deck until a pet is in play (foods along the way attach to it; only
// the last-applied perk counts). If anyone can no longer field a pet the
// battle ends. Otherwise play effects resolve (rocks, strips, steals,
// mills — any of which can faint a pet before the clash). Then the two pets
// deal their full Power to each other simultaneously as damage markers; a
// pet with Damage >= Power faints, firing Faint effects. Survivors that
// took damage fire Hurt effects. Shields (Turtle, Gorilla, Melon) block
// entire hits; Garlic shaves 1 from each; Scorpion KOs whatever its clash
// attack manages to hurt. A clash that changes nothing ends the battle as a
// stalemate.
//
// resolveBattle is the orchestrator: it re-runs the (deterministic) simulation
// from the recorded dice/decision tapes, publishing either a completed result
// or a suspended one awaiting a mid-battle decision (Golden pack: Nurse Shark).
func (g *Game) resolveBattle() {
	g.NextCardID = g.BattleCardBase
	g.battleRollCursor = 0
	g.battleDecisionCursor = 0
	res, pending := g.runBattle()
	g.Battle = res
	if pending != nil {
		g.PendingBattle = pending
		return
	}
	g.PendingBattle = nil
	g.finalizeBattle(res)
}

// finalizeBattle applies the persistent effects of a completed battle: trophies,
// the priority token hand-off, the result log line, and clearing the per-round
// apples-in-play bank. Deferred here (not inside runBattle) because runBattle
// may re-run several times before the battle actually completes.
func (g *Game) finalizeBattle(res *BattleResult) {
	n := len(g.Players)
	winner := res.WinnerSeat
	if winner >= 0 {
		g.Players[winner].Trophies += res.Trophies
		// Priority token: the winner hands it to the other player; a loser who
		// held it keeps it; a draw leaves it put. (Two-player rule.)
		if winner == g.PrioritySeat {
			g.PrioritySeat = (winner + 1) % n
		}
	}
	if winner < 0 {
		g.addLog(LogEntry{Seat: -1, Icon: "⚔️", Kind: LogResult,
			Text: fmt.Sprintf("Round %d battle ends in a draw.", g.Round)})
	} else {
		g.addLog(LogEntry{Seat: winner, Icon: "⚔️", Kind: LogResult,
			Text: fmt.Sprintf("%s wins the round %d battle (+%d🏆).", g.Players[winner].Name, g.Round, res.Trophies)})
	}
	for _, p := range g.Players {
		p.PendingApplesInPlay = 0
		p.PendingTrumpets = 0
	}
}

// runBattle plays the simulation to completion or until it needs a mid-battle
// decision, returning the (partial) result and a non-nil pending in the latter
// case. It mutates no persistent player state — that is finalizeBattle's job.
func (g *Game) runBattle() (*BattleResult, *PendingBattleDecision) {
	n := len(g.Players)
	res := &BattleResult{Round: g.Round, WinnerSeat: -1, StackSizes: make([]int, n), Lineups: make([][]Card, n)}
	var suspended *PendingBattleDecision
	sides := make([]*battleSide, n)
	emit := func(ev BattleEvent) { res.Events = append(res.Events, ev) }
	// pname is the owning player's display name for a seat, for log text.
	pname := func(seat int) string { return g.Players[seat].Name }

	for _, p := range g.Players {
		s := &battleSide{stack: append([]Card(nil), p.Deck...), faintedHats: map[Suit]bool{}}
		sides[p.Seat] = s
		res.StackSizes[p.Seat] = len(p.Deck)
		res.Lineups[p.Seat] = append([]Card(nil), p.Deck...)
	}
	// enemyOf returns the opposing side (two-player; generalizes later).
	enemyOf := func(seat int) *battleSide { return sides[(seat+1)%n] }
	// seatOrder resolves the priority-token holder first, then everyone else.
	// Reveals, queued play effects, and cross-side triggers all follow it, so
	// when two pets would act simultaneously (e.g. both throwing rocks) the
	// holder acts first — its rocks can faint the enemy pet before that pet's
	// own queued rocks resolve.
	seatOrder := make([]int, 0, n)
	seatOrder = append(seatOrder, g.PrioritySeat)
	for seat := range sides {
		if seat != g.PrioritySeat {
			seatOrder = append(seatOrder, seat)
		}
	}
	// startApple seeds one in-play apple onto a seat's first pet.
	startApple := func(seat int) {
		apple := g.newApple()
		sides[seat].pending = append(sides[seat].pending, apple)
		emit(BattleEvent{Type: "prep", Seat: seat, Card: &apple,
			Text: fmt.Sprintf("%s starts the battle with an apple in play.", pname(seat))})
	}
	// Battle-prep effects that start apples in play (Monkey): they attach
	// to the owner's first pet.
	for _, p := range g.Players {
		for _, c := range p.Deck {
			for _, e := range c.Effects {
				if e.Trigger == TriggerBattlePrep && e.Action == ActionApplesInPlay {
					for range e.count() {
						startApple(p.Seat)
					}
				}
			}
		}
		// Golden pack: apples-in-play banked by a sold Hercules Beetle this
		// round (read-only here; finalizeBattle clears it once the battle ends,
		// so re-runs bank the same amount).
		for range p.PendingApplesInPlay {
			startApple(p.Seat)
		}
		// Bird of Paradise: start the battle with Trumpets in the pool.
		if p.PendingTrumpets > 0 {
			sides[p.Seat].trumpets += p.PendingTrumpets
			emit(BattleEvent{Type: "trumpet", Seat: p.Seat, Count: p.PendingTrumpets,
				Text: fmt.Sprintf("%s starts with %d Trumpet%s.", pname(p.Seat), p.PendingTrumpets, plural(p.PendingTrumpets))})
		}
	}

	summon := func(seat int, c Card, cause string) {
		s := sides[seat]
		s.stack = append([]Card{c}, s.stack...)
		emit(BattleEvent{Type: "summon", Seat: seat, Card: &c,
			Text: fmt.Sprintf("%s summons %s %s.", cause, article(c.Name), c.Name)})
	}
	// summonBottom puts a card on the BOTTOM of a seat's stack (Bear).
	summonBottom := func(seat int, c Card, cause string) {
		s := sides[seat]
		s.stack = append(s.stack, c)
		emit(BattleEvent{Type: "summon", Seat: seat, Card: &c,
			Text: fmt.Sprintf("%s puts %s %s on the bottom of %s's deck.", cause, article(c.Name), c.Name, pname(seat))})
	}
	mintFor := func(kind string) Card {
		if kind == "bee" {
			return g.newBee()
		}
		return g.newApple()
	}
	// gainTrumpets adds trumpets to a side and narrates it.
	gainTrumpets := func(seat, n int, cause string) {
		if n <= 0 {
			return
		}
		sides[seat].trumpets += n
		emit(BattleEvent{Type: "trumpet", Seat: seat, Count: n,
			Text: fmt.Sprintf("%s gains %d Trumpet%s.", cause, n, plural(n))})
	}
	// spend pays an effect's Trumpet cost from a side's pool, narrating the
	// spend. Returns false (without paying) when the side can't afford it, so
	// the caller skips the effect. A zero-cost effect always "pays".
	spend := func(seat int, e Effect, cause string) bool {
		if e.CostTrumpet <= 0 {
			return true
		}
		if sides[seat].trumpets < e.CostTrumpet {
			return false
		}
		sides[seat].trumpets -= e.CostTrumpet
		emit(BattleEvent{Type: "trumpet", Seat: seat, Count: -e.CostTrumpet,
			Text: fmt.Sprintf("%s spends %d Trumpet%s.", cause, e.CostTrumpet, plural(e.CostTrumpet))})
		return true
	}

	// allowed gates battle-time effects on their conditions.
	allowed := func(e Effect, u *BattleUnit) bool {
		if g.Round < e.MinRound {
			return false
		}
		switch e.Condition {
		case ConditionHasPerk:
			return u != nil && u.activePerk() != nil
		case ConditionTripled:
			return false // shop-time condition; never true in battle
		}
		return true
	}

	// hitUnit applies one attack against a seat's pet: shields block the
	// whole hit, Garlic shaves per-attack damage. Returns the damage dealt and,
	// when a shield absorbed the hit, a shieldBlock describing it (nil
	// otherwise). A set-aside Turtle shield is spent before the pet's own
	// shields (Melon/Gorilla) so the borrowed card clears the board first.
	hitUnit := func(seat, amount int) (dealt int, block *shieldBlock, prevent *preventInfo) {
		u := sides[seat].unit
		if u == nil || amount <= 0 {
			return 0, nil, nil
		}
		if sides[seat].shields > 0 {
			sides[seat].shields--
			var card *Card
			source := ""
			if n := len(sides[seat].shieldCards); n > 0 {
				c := sides[seat].shieldCards[n-1]
				sides[seat].shieldCards = sides[seat].shieldCards[:n-1]
				card = &c
				source = c.Name
			}
			return 0, &shieldBlock{source: source, release: card}, nil
		}
		if n := len(u.Shields); n > 0 {
			sc := u.Shields[n-1]
			u.Shields = u.Shields[:n-1]
			return 0, &shieldBlock{source: sc.source, release: sc.card}, nil
		}
		reduce := u.prevention()
		// One partial-prevention charge per hit (whether or not it fully absorbs
		// the blow): the pet's own first (Potato), else a side-level set-aside
		// (Cone Snail).
		if len(u.hitPrevent) > 0 {
			amt := u.hitPrevent[0]
			u.hitPrevent = u.hitPrevent[1:]
			reduce += amt
			prevent = &preventInfo{amount: amt}
		} else if len(sides[seat].hitPrevent) > 0 {
			amt := sides[seat].hitPrevent[0]
			sides[seat].hitPrevent = sides[seat].hitPrevent[1:]
			reduce += amt
			prevent = &preventInfo{amount: amt}
			if len(sides[seat].preventCards) > 0 {
				c := sides[seat].preventCards[0]
				sides[seat].preventCards = sides[seat].preventCards[1:]
				prevent.release = &c
			}
		}
		dealt = max(0, amount-reduce)
		u.Damage += dealt
		return dealt, nil, prevent
	}

	// emitShield narrates a blocked hit — naming the source rather than a bare
	// "shield" — and removes the spent card (Melon food or set-aside Turtle)
	// from the play area.
	emitShield := func(seat int, petName string, block *shieldBlock) {
		txt := fmt.Sprintf("%s blocks the hit.", petName)
		if block.source != "" {
			txt = fmt.Sprintf("%s blocks the hit with a %s.", petName, block.source)
		}
		emit(BattleEvent{Type: "shield", Seat: seat, Text: txt})
		if block.release != nil {
			emit(BattleEvent{Type: "release", Seat: seat, Card: block.release})
		}
	}

	// emitPrevent narrates a Cone Snail partial prevention after the hit that
	// consumed it, and drops the spent set-aside card.
	emitPrevent := func(seat int, petName string, prev *preventInfo) {
		u := sides[seat].unit
		after := 0
		if u != nil {
			after = u.Damage
		}
		emit(BattleEvent{Type: "prevent", Seat: seat, Count: prev.amount, DamageAfter: after,
			Text: fmt.Sprintf("A set-aside Cone Snail shields %s, preventing %d damage.", petName, prev.amount)})
		if prev.release != nil {
			emit(BattleEvent{Type: "release", Seat: seat, Card: prev.release})
		}
	}

	// faint fires the unit's faint effects (its own and its perk's) in
	// effect order, updates faint counters, and notifies enemy pets
	// (Hippo's heal).
	var faint func(seat int, u *BattleUnit)
	faint = func(seat int, u *BattleUnit) {
		s := sides[seat]
		s.petsFainted++
		if isBee(u.Card) {
			s.beesFainted++
		}
		// Track distinct suits among friendly fainted pets (Honduran White
		// Bat). Bees and the Golden Retriever have no suit.
		if !isBee(u.Card) && u.Card.Suit != "" {
			s.faintedHats[u.Card.Suit] = true
		}
		// setAside marks the fainted pet as kept beside the arena with a
		// pending effect, so the client can show its card until it resolves.
		setAside := func() {
			c := u.Card
			emit(BattleEvent{Type: "setaside", Seat: seat, Card: &c,
				Text: fmt.Sprintf("%s is set aside.", c.Name)})
		}
		cause := fmt.Sprintf("%s's faint effect", u.Card.Name)
		for _, e := range u.effects() {
			if e.Trigger != TriggerFaint || !allowed(e, u) {
				continue
			}
			if !spend(seat, e, u.Card.Name) {
				continue
			}
			switch e.Action {
			case ActionSummonTop:
				target := seat
				if e.Target == "enemy" {
					target = (seat + 1) % n
				}
				for range effectCount(e, s, u, enemyOf(seat)) {
					summon(target, mintFor(e.Card), cause)
				}
			case ActionSummonBottom:
				for range effectCount(e, s, u, enemyOf(seat)) {
					if e.Target == "all" {
						for other := range sides {
							summonBottom(other, mintFor(e.Card), cause)
						}
					} else {
						summonBottom(seat, mintFor(e.Card), cause)
					}
				}
			case ActionGainTrumpet:
				gainTrumpets(seat, effectCount(e, s, u, enemyOf(seat)), cause)
			case ActionDrainTrumpet:
				es := enemyOf(seat)
				lost := min(e.count(), es.trumpets)
				if lost > 0 {
					es.trumpets -= lost
					emit(BattleEvent{Type: "trumpet", Seat: (seat + 1) % n, Count: -lost,
						Text: fmt.Sprintf("%s drains %d Trumpet%s from the enemy.", cause, lost, plural(lost))})
				}
			case ActionPreventNextHit:
				s.hitPrevent = append(s.hitPrevent, e.count())
				s.preventCards = append(s.preventCards, u.Card)
				setAside()
			case ActionRecycleApples:
				recycled := 0
				for _, f := range u.Foods {
					if f.Food == FoodApple && recycled < e.count() {
						summon(seat, f, fmt.Sprintf("%s's faint effect", u.Card.Name))
						recycled++
					}
				}
			case ActionRecyclePerkApples:
				// Macaque: recycle up to Count apples, then the active perk on
				// top (so the perk reveals first and re-attaches to the next pet).
				recycled := 0
				for _, f := range u.Foods {
					if f.Food == FoodApple && recycled < e.count() {
						summon(seat, f, cause)
						recycled++
					}
				}
				if perk := u.activePerk(); perk != nil {
					summon(seat, *perk, cause)
				}
			case ActionBeeRocks:
				s.beePlayRocks = append(s.beePlayRocks, setAsideRocks{dice: e.count(), src: u.Card})
				setAside()
			case ActionFeedOnPlay:
				s.feedOnPlay = append(s.feedOnPlay, feedAside{apples: e.count(), src: u.Card})
				setAside()
			case ActionGuardRetriever:
				s.retrieverGuards = append(s.retrieverGuards, e.count())
				setAside()
			case ActionDelayedRocks:
				s.oneShotRocks = append(s.oneShotRocks,
					setAsideRocks{dice: e.count(), everyone: e.Target == "all", src: u.Card})
				setAside()
			case ActionRecurringRocks:
				s.recurringRocks = append(s.recurringRocks,
					setAsideRocks{dice: e.count(), src: u.Card})
				setAside()
			case ActionEnemyLastPetRocks:
				s.lastPetRocks = append(s.lastPetRocks, lastPetVolley{dice: e.count(), src: u.Card})
				setAside()
			case ActionShieldNext:
				s.shields += e.count()
				s.shieldCards = append(s.shieldCards, u.Card)
				setAside()
			case ActionBeeAura:
				s.beeBonus += e.count()
				setAside()
			case ActionPetAura:
				s.petBonus += e.count()
				setAside()
			}
		}
		// Enemy Faints triggers on surviving pets elsewhere (Hippo).
		for other, os := range sides {
			if other == seat || os.unit == nil || !os.unit.Alive() {
				continue
			}
			for _, e := range os.unit.effects() {
				if e.Trigger != TriggerEnemyFaint || e.Action != ActionHeal || !allowed(e, os.unit) {
					continue
				}
				healed := min(effectCount(e, os, os.unit, sides[seat]), os.unit.Damage)
				if healed > 0 {
					os.unit.Damage -= healed
					emit(BattleEvent{Type: "heal", Seat: other, DamageAfter: os.unit.Damage,
						Text: fmt.Sprintf("%s heals %d after an enemy faints.", os.unit.Card.Name, healed)})
				}
			}
		}
	}

	// hurt fires Hurt effects on a pet that was damaged and survived.
	hurt := func(seat int, u *BattleUnit) {
		if !u.Alive() {
			return
		}
		for _, e := range u.effects() {
			if e.Trigger != TriggerHurt || !allowed(e, u) {
				continue
			}
			if !spend(seat, e, u.Card.Name) {
				continue
			}
			switch e.Action {
			case ActionEatApple:
				for range effectCount(e, sides[seat], u, enemyOf(seat)) {
					u.Foods = append(u.Foods, g.newApple())
					u.Bonus++
				}
				emit(BattleEvent{Type: "eat", Seat: seat, Bonus: u.Bonus,
					Text: fmt.Sprintf("%s eats an apple after being hurt (now +%d).", u.Card.Name, u.Bonus)})
			case ActionSummonTop:
				for range effectCount(e, sides[seat], u, enemyOf(seat)) {
					summon(seat, mintFor(e.Card), fmt.Sprintf("%s's hurt effect", u.Card.Name))
				}
			case ActionGainTrumpet:
				gainTrumpets(seat, effectCount(e, sides[seat], u, enemyOf(seat)), fmt.Sprintf("%s's hurt effect", u.Card.Name))
			case ActionShieldSelf:
				// Gorilla's own hurt-triggered block: innate, no card to drop.
				for range e.count() {
					u.Shields = append(u.Shields, shieldCharge{})
				}
			}
		}
	}

	// afterAttack fires After-Attack effects on a pet that survived a clash it
	// fought in (Bulldog eats an apple). Effects here are once per battle.
	afterAttack := func(seat int, u *BattleUnit) {
		if !u.Alive() || u.afterAttackUsed {
			return
		}
		for _, e := range u.effects() {
			if e.Trigger != TriggerAfterAttack || !allowed(e, u) {
				continue
			}
			if !spend(seat, e, u.Card.Name) {
				continue
			}
			switch e.Action {
			case ActionEatApple:
				for range effectCount(e, sides[seat], u, enemyOf(seat)) {
					u.Foods = append(u.Foods, g.newApple())
					u.Bonus++
				}
				emit(BattleEvent{Type: "eat", Seat: seat, Bonus: u.Bonus,
					Text: fmt.Sprintf("%s eats an apple after attacking (now +%d).", u.Card.Name, u.Bonus)})
			}
			u.afterAttackUsed = true
		}
	}

	// throwRocks rolls `dice` rock dice against one seat's pet. Rocks are
	// not "attacks with" the pet, so no knockout applies. Reports a kill.
	throwRocks := func(from, target, dice int, source *Card) (killed bool) {
		tu := sides[target].unit
		if tu == nil || dice <= 0 {
			// No target, or a Per-scaled volley that came out to zero (Royal
			// Flycatcher / Grizzly with no fainted pets): nothing to animate.
			return false
		}
		roll := 0
		faces := make([]int, dice)
		for i := range dice {
			faces[i] = g.rollRockDie()
			roll += faces[i]
		}
		dealt, block, prev := hitUnit(target, roll)
		died := !tu.Alive()
		// A set-aside pet (Snake/Blowfish/Badger/Croc) throws its rocks after a
		// different pet has been played, so credit `source` explicitly; only
		// fall back to the pet in play for direct throwers (Hedgehog/Rhino).
		var rockTxt string
		if source != nil {
			switch {
			case roll == 0:
				rockTxt = fmt.Sprintf("%s's set-aside rocks miss %s.", source.Name, tu.Card.Name)
			case died:
				rockTxt = fmt.Sprintf("%s's set-aside rocks pelt %s for %d — it faints.", source.Name, tu.Card.Name, roll)
			default:
				rockTxt = fmt.Sprintf("%s's set-aside rocks pelt %s for %d.", source.Name, tu.Card.Name, roll)
			}
		} else {
			thrower := pname(from)
			if su := sides[from].unit; su != nil {
				thrower = su.Card.Name
			}
			switch {
			case roll == 0:
				rockTxt = fmt.Sprintf("%s's rocks miss %s.", thrower, tu.Card.Name)
			case died:
				rockTxt = fmt.Sprintf("%s pelts %s for %d — it faints.", thrower, tu.Card.Name, roll)
			default:
				rockTxt = fmt.Sprintf("%s pelts %s for %d.", thrower, tu.Card.Name, roll)
			}
		}
		emit(BattleEvent{
			Type: "rock", Seat: from, Target: target, Roll: roll, Dice: faces,
			DamageAfter: tu.Damage, TargetDied: died, Text: rockTxt,
		})
		if block != nil {
			emitShield(target, tu.Card.Name, block)
		}
		if prev != nil {
			emitPrevent(target, tu.Card.Name, prev)
		}
		if died {
			faint(target, tu)
			sides[target].unit = nil
			return true
		}
		if dealt > 0 {
			hurt(target, tu)
		}
		return false
	}

	// nextTarget finds the seat whose pet a standard enemy-directed play
	// effect hits.
	nextTarget := func(from int) int {
		for off := 1; off < n; off++ {
			cand := (from + off) % n
			if sides[cand].unit != nil {
				return cand
			}
		}
		return -1
	}

	// The exchange loop terminates: every clash kills at least one pet or
	// is a detected stalemate, and summons/auras are finite. The guard is
	// just insurance as effects get richer.
	//
	// clashStreak counts how many times the current pair has clashed without
	// either fainting. Some effects (e.g. eat-an-apple-when-hurt) can make two
	// pets un-killable, looping forever; if they trade blows deadlockLimit
	// times in a row, both drop so the battle can proceed. It resets whenever
	// the matchup changes (a fresh pet enters).
	const deadlockLimit = 9
	clashStreak := 0
	for range 10_000 {
		// Reveal until every side has a pet in play or runs out. Play
		// effects queue up and resolve after all reveals (simultaneous).
		var plays []queuedPlay
		newlyPlayed := make([]bool, n)
		for _, seat := range seatOrder {
			s := sides[seat]
			for s.unit == nil && len(s.stack) > 0 {
				c := s.stack[0]
				s.stack = s.stack[1:]
				if c.IsFood() {
					emit(BattleEvent{Type: "reveal", Seat: seat, Card: &c,
						Text: fmt.Sprintf("%s's %s is set aside for the next pet.", pname(seat), c.Name)})
					s.pending = append(s.pending, c)
					continue
				}
				u := &BattleUnit{Card: c, Foods: s.pending}
				u.Bonus += appleCount(s.pending)
				u.Bonus += s.petBonus
				if isBee(c) {
					u.Bonus += s.beeBonus
				}
				// Pets carry their starting bonus (foods + auras) in the
				// reveal event so clients can display it directly.
				revealTxt := fmt.Sprintf("%s's %s enters the fray.", pname(seat), c.Name)
				if u.Bonus > 0 {
					revealTxt = fmt.Sprintf("%s's %s enters the fray (+%d).", pname(seat), c.Name, u.Bonus)
				}
				emit(BattleEvent{Type: "reveal", Seat: seat, Card: &c, Bonus: u.Bonus, Text: revealTxt})
				s.pending = nil
				s.unit = u
				s.petsPlayed++
				newlyPlayed[seat] = true
				// Set-aside payouts fire before the new pet's own play
				// effects.
				for _, r := range s.oneShotRocks {
					src := r.src
					plays = append(plays, queuedPlay{seat: seat, everyone: r.everyone,
						effect: Effect{Action: ActionThrowRock, Count: r.dice}, release: &src, source: &src})
				}
				s.oneShotRocks = nil
				for _, r := range s.recurringRocks {
					src := r.src
					plays = append(plays, queuedPlay{seat: seat,
						effect: Effect{Action: ActionThrowRock, Count: r.dice}, source: &src})
				}
				// Poison Dart Frog: rocks whenever a Bee is played.
				if isBee(c) {
					for _, r := range s.beePlayRocks {
						src := r.src
						plays = append(plays, queuedPlay{seat: seat,
							effect: Effect{Action: ActionThrowRock, Count: r.dice}, source: &src})
					}
				}
				// Giant Isopod: each set-aside spends one Trumpet (mandatory when
				// affordable) to feed the just-played pet its apples.
				for i := range s.feedOnPlay {
					if s.trumpets <= 0 {
						break
					}
					s.trumpets--
					src := s.feedOnPlay[i].src
					emit(BattleEvent{Type: "trumpet", Seat: seat, Count: -1,
						Text: fmt.Sprintf("%s spends 1 Trumpet.", src.Name)})
					for range s.feedOnPlay[i].apples {
						u.Foods = append(u.Foods, g.newApple())
						u.Bonus++
					}
					emit(BattleEvent{Type: "eat", Seat: seat, Bonus: u.Bonus,
						Text: fmt.Sprintf("%s feeds %s %d apples (now +%d).", src.Name, c.Name, s.feedOnPlay[i].apples, u.Bonus)})
				}
				// Walk the pet's own play effects, then its active perk's, so a
				// play-time shield knows its source (an innate pet block vs a
				// Melon perk that should be shown and later dropped).
				addPlay := func(e Effect, perk *Card) {
					if e.Trigger != TriggerPlay {
						return
					}
					// Shields apply the instant the pet enters play, ahead of
					// any queued rocks (Melon; Wildebeest, which pays Trumpets).
					if e.Action == ActionShieldSelf {
						if !spend(seat, e, u.Card.Name) {
							return
						}
						for range e.count() {
							ch := shieldCharge{}
							if perk != nil {
								food := *perk
								ch = shieldCharge{source: perk.Name, card: &food}
							}
							u.Shields = append(u.Shields, ch)
						}
						return
					}
					// Potato's partial preventions likewise arm on entry.
					if e.Action == ActionPreventSelf {
						for range max(e.Cap, 1) {
							u.hitPrevent = append(u.hitPrevent, e.count())
						}
						return
					}
					plays = append(plays, queuedPlay{seat: seat, unit: u, effect: e})
				}
				for _, e := range u.Card.Effects {
					addPlay(e, nil)
				}
				if perk := u.activePerk(); perk != nil {
					for _, e := range perk.Effects {
						addPlay(e, perk)
					}
				}
			}
			// Golden pack: a side that has run out of cards but still holds
			// Trumpets fields a one-time Golden Retriever, its Power equal to
			// those Trumpets. This happens before the "anyone out?" check so it
			// can still clash.
			if s.unit == nil && len(s.stack) == 0 && s.trumpets > 0 && !s.grSummoned {
				gr := g.newGoldenRetriever(s.trumpets)
				grUnit := &BattleUnit{Card: gr}
				// German Shepherd: each set-aside guards the Golden Retriever's
				// first hits (partial preventions).
				grUnit.hitPrevent = append(grUnit.hitPrevent, s.retrieverGuards...)
				s.unit = grUnit
				s.grSummoned = true
				s.petsPlayed++
				newlyPlayed[seat] = true
				emit(BattleEvent{Type: "reveal", Seat: seat, Card: &gr, Count: s.trumpets, Bonus: 0,
					Text: fmt.Sprintf("%s is out of cards — a Golden Retriever charges in with %d Trumpet%s (Power %d).",
						pname(seat), s.trumpets, plural(s.trumpets), s.trumpets)})
			}
		}
		// Cross-side play triggers: Rhino rocks anyone who just played;
		// Crocodile volleys when the enemy plays their last pet.
		for _, seat := range seatOrder {
			if !newlyPlayed[seat] {
				continue
			}
			for _, other := range seatOrder {
				os := sides[other]
				if other == seat {
					continue
				}
				if os.unit != nil {
					for _, e := range os.unit.effects() {
						if e.Trigger == TriggerEnemyPlay && e.Action == ActionThrowRock && allowed(e, os.unit) {
							plays = append(plays, queuedPlay{seat: other, unit: os.unit, effect: e})
						}
					}
				}
				if !sides[seat].hasPetInStack() {
					for _, v := range os.lastPetRocks {
						src := v.src
						plays = append(plays, queuedPlay{seat: other,
							effect: Effect{Action: ActionThrowRock, Count: v.dice}, release: &src, source: &src})
					}
					os.lastPetRocks = nil
				}
			}
		}

		// A fresh pet on either side is a new matchup, so the deadlock streak
		// starts over.
		for _, np := range newlyPlayed {
			if np {
				clashStreak = 0
				break
			}
		}

		// Resolve play effects. Any of these can faint a pet before the clash.
		// This runs before the "battle over" check so a parting shot fires even
		// when its own side is already out (Crocodile's last-pet volley).
		anyDeath := false
		for _, q := range plays {
			// Effects sourced from a specific unit fizzle if it's gone.
			if q.unit != nil && sides[q.seat].unit != q.unit {
				continue
			}
			if q.unit != nil && !allowed(q.effect, q.unit) {
				continue
			}
			costName := pname(q.seat)
			if q.unit != nil {
				costName = q.unit.Card.Name
			}
			if !spend(q.seat, q.effect, costName) {
				continue
			}
			switch q.effect.Action {
			case ActionThrowRock:
				dice := q.effect.count()
				if q.unit != nil {
					dice = effectCount(q.effect, sides[q.seat], q.unit, enemyOf(q.seat))
				}
				switch {
				case q.everyone:
					for seat := range sides {
						if throwRocks(q.seat, seat, dice, q.source) {
							anyDeath = true
						}
					}
				case q.effect.Target == "self":
					// Manatee pelts its own pet.
					if throwRocks(q.seat, q.seat, dice, q.source) {
						anyDeath = true
					}
				default:
					if t := nextTarget(q.seat); t >= 0 {
						if throwRocks(q.seat, t, dice, q.source) {
							anyDeath = true
						}
					}
				}
				if q.release != nil {
					emit(BattleEvent{Type: "release", Seat: q.seat, Card: q.release})
				}
			case ActionGainTrumpet:
				gainTrumpets(q.seat, effectCount(q.effect, sides[q.seat], q.unit, enemyOf(q.seat)), costName)
			case ActionDoubleTrumpets:
				gain := sides[q.seat].trumpets
				if q.effect.Cap > 0 && gain > q.effect.Cap {
					gain = q.effect.Cap
				}
				gainTrumpets(q.seat, gain, costName)
			case ActionStealPerk:
				t := nextTarget(q.seat)
				if t < 0 {
					continue
				}
				tu := sides[t].unit
				perk := tu.activePerk()
				if perk == nil {
					continue
				}
				stolen := *perk
				// Drop that perk food from the enemy pet (perks add no power, so
				// no bonus change) and put it on top of the thief's deck.
				for i := range tu.Foods {
					if tu.Foods[i].ID == stolen.ID {
						tu.Foods = append(tu.Foods[:i], tu.Foods[i+1:]...)
						break
					}
				}
				summon(q.seat, stolen, fmt.Sprintf("%s's ability", q.unit.Card.Name))
				emit(BattleEvent{Type: "strip", Seat: q.seat, Target: t,
					Text: fmt.Sprintf("%s snatches %s's %s.", q.unit.Card.Name, tu.Card.Name, stolen.Name)})
			case ActionStripApples:
				t := nextTarget(q.seat)
				if t < 0 {
					continue
				}
				tu := sides[t].unit
				apples := appleCount(tu.Foods)
				if apples == 0 {
					continue
				}
				kept := tu.Foods[:0]
				for _, f := range tu.Foods {
					if f.Food != FoodApple {
						kept = append(kept, f)
					}
				}
				tu.Foods = kept
				tu.Bonus -= apples
				died := !tu.Alive()
				emit(BattleEvent{Type: "strip", Seat: q.seat, Target: t, TargetDied: died,
					Text: fmt.Sprintf("%s discards %s's apples.", q.unit.Card.Name, tu.Card.Name)})
				if died {
					faint(t, tu)
					sides[t].unit = nil
					anyDeath = true
				}
			case ActionStripFoods:
				t := nextTarget(q.seat)
				if t < 0 {
					continue
				}
				tu := sides[t].unit
				tu.Bonus -= appleCount(tu.Foods)
				tu.Foods = nil
				died := !tu.Alive()
				emit(BattleEvent{Type: "strip", Seat: q.seat, Target: t, TargetDied: died,
					Text: fmt.Sprintf("%s strips %s's apples away.", q.unit.Card.Name, tu.Card.Name)})
				if died {
					faint(t, tu)
					sides[t].unit = nil
					anyDeath = true
				}
			case ActionStealApples:
				t := nextTarget(q.seat)
				if t < 0 {
					continue
				}
				tu := sides[t].unit
				steal := min(q.effect.count(), appleCount(tu.Foods))
				if steal == 0 {
					continue
				}
				moved := 0
				kept := tu.Foods[:0]
				for _, f := range tu.Foods {
					if f.Food == FoodApple && moved < steal {
						q.unit.Foods = append(q.unit.Foods, f)
						moved++
						continue
					}
					kept = append(kept, f)
				}
				tu.Foods = kept
				tu.Bonus -= moved
				q.unit.Bonus += moved
				died := !tu.Alive()
				emit(BattleEvent{Type: "steal", Seat: q.seat, Target: t, Count: moved, TargetDied: died,
					Text: fmt.Sprintf("%s steals %d apple%s from %s.", q.unit.Card.Name, moved, plural(moved), tu.Card.Name)})
				if died {
					faint(t, tu)
					sides[t].unit = nil
					anyDeath = true
				}
			case ActionMillEnemy:
				t := (q.seat + 1) % n
				ts := sides[t]
				for len(ts.stack) > 0 {
					top := ts.stack[0]
					if top.IsPet() && !isBee(top) {
						break
					}
					ts.stack = ts.stack[1:]
					emit(BattleEvent{Type: "mill", Seat: t, Card: &top,
						Text: fmt.Sprintf("%s burns %s off %s's deck.", q.unit.Card.Name, top.Name, pname(t))})
				}
			case ActionSummonTop:
				for range effectCount(q.effect, sides[q.seat], q.unit, enemyOf(q.seat)) {
					summon(q.seat, mintFor(q.effect.Card), fmt.Sprintf("%s's ability", q.unit.Card.Name))
				}
			case ActionEatApple:
				count := effectCount(q.effect, sides[q.seat], q.unit, enemyOf(q.seat))
				if count > 0 {
					for range count {
						q.unit.Foods = append(q.unit.Foods, g.newApple())
						q.unit.Bonus++
					}
					emit(BattleEvent{Type: "eat", Seat: q.seat, Bonus: q.unit.Bonus,
						Text: fmt.Sprintf("%s eats an apple (now +%d).", q.unit.Card.Name, q.unit.Bonus)})
				}
			case ActionShuffleApples:
				// Komodo: only if it's the side's first pet, shuffle apples into
				// random deck positions (deterministic via the battle draw tape).
				if q.effect.Condition == ConditionFirstPet && sides[q.seat].petsPlayed != 1 {
					continue
				}
				s := sides[q.seat]
				for range q.effect.count() {
					pos := g.battleDraw(len(s.stack) + 1)
					apple := g.newApple()
					s.stack = slices.Insert(s.stack, pos, apple)
					emit(BattleEvent{Type: "summon", Seat: q.seat, Card: &apple,
						Text: fmt.Sprintf("%s shuffles an apple into %s's deck.", q.unit.Card.Name, pname(q.seat))})
				}
			case ActionSpendRocks:
				// Nurse Shark: the owner chooses how many Trumpets (0..available,
				// capped at Count) to spend; each throws two rocks. This is the one
				// mid-battle decision — it may suspend the whole simulation.
				s := sides[q.seat]
				maxSpend := min(q.effect.count(), s.trumpets)
				choice, pending := g.decideBattle(PendingBattleDecision{
					Seat: q.seat, Kind: "nurseShark", PetName: q.unit.Card.Name,
					Min: 0, Max: maxSpend, Trumpets: s.trumpets,
				})
				if pending != nil {
					suspended = pending
					break
				}
				if choice > 0 {
					s.trumpets -= choice
					emit(BattleEvent{Type: "trumpet", Seat: q.seat, Count: -choice,
						Text: fmt.Sprintf("%s spends %d Trumpet%s.", q.unit.Card.Name, choice, plural(choice))})
					if t := nextTarget(q.seat); t >= 0 {
						if throwRocks(q.seat, t, 2*choice, nil) {
							anyDeath = true
						}
					}
				}
			}
			if suspended != nil {
				break // stop mid-plays; the battle re-runs once the choice is in
			}
		}
		// A pending decision unwinds the whole simulation; the events emitted so
		// far are a valid prefix the re-run reproduces exactly.
		if suspended != nil {
			return res, suspended
		}
		// Battle over? A side that can no longer field a pet is out (checked
		// after play effects so parting shots land, using canField so a pet that
		// will simply refill next reveal doesn't count as out).
		anyOut := false
		for _, s := range sides {
			if !s.canField() {
				anyOut = true
			}
		}
		if anyOut {
			break
		}
		if anyDeath {
			continue // refill before any clash
		}

		// Clash. Two-player for now; >2-player battle pairings come later
		// (the surrounding state is already per-seat).
		ua, ub := sides[0].unit, sides[1].unit
		powA, powB := ua.Power(), ub.Power()
		dealtA, blockA, prevA := hitUnit(0, powB)
		dealtB, blockB, prevB := hitUnit(1, powA)
		// Scorpion: a clash attack that hurts, KOs.
		if dealtA > 0 && ub.hasKnockout() {
			ua.Damage = max(ua.Damage, ua.Power())
		}
		if dealtB > 0 && ua.hasKnockout() {
			ub.Damage = max(ub.Damage, ub.Power())
		}
		// Deadlock guard: if the pair keeps surviving, count the exchanges and
		// force a mutual knockout once they hit the limit.
		deadlocked := false
		if ua.Alive() && ub.Alive() {
			clashStreak++
			if clashStreak >= deadlockLimit {
				deadlocked = true
				ua.Damage = max(ua.Damage, ua.Power())
				ub.Damage = max(ub.Damage, ub.Power())
			}
		} else {
			clashStreak = 0
		}
		clashTxt := fmt.Sprintf("%s's %s and %s's %s trade blows.",
			pname(0), ua.Card.Name, pname(1), ub.Card.Name)
		switch da, db := !ua.Alive(), !ub.Alive(); {
		case deadlocked:
			clashTxt = fmt.Sprintf("%s's %s and %s's %s are deadlocked after %d clashes — both faint.",
				pname(0), ua.Card.Name, pname(1), ub.Card.Name, deadlockLimit)
		case da && db:
			clashTxt += " Both faint."
		case da:
			clashTxt += fmt.Sprintf(" %s faints.", ua.Card.Name)
		case db:
			clashTxt += fmt.Sprintf(" %s faints.", ub.Card.Name)
		}
		emit(BattleEvent{
			Type:   "clash",
			Damage: []int{ua.Damage, ub.Damage},
			Died:   []bool{!ua.Alive(), !ub.Alive()},
			Text:   clashTxt,
		})
		if blockA != nil {
			emitShield(0, ua.Card.Name, blockA)
		}
		if blockB != nil {
			emitShield(1, ub.Card.Name, blockB)
		}
		if prevA != nil {
			emitPrevent(0, ua.Card.Name, prevA)
		}
		if prevB != nil {
			emitPrevent(1, ub.Card.Name, prevB)
		}
		if ua.Alive() && ub.Alive() && dealtA == 0 && dealtB == 0 &&
			blockA == nil && blockB == nil && prevA == nil && prevB == nil {
			break // stalemate: nothing can ever change
		}
		dealt := []int{dealtA, dealtB}
		for seat, u := range []*BattleUnit{ua, ub} {
			if !u.Alive() {
				faint(seat, u)
				sides[seat].unit = nil
			} else {
				if dealt[seat] > 0 {
					hurt(seat, u)
				}
				afterAttack(seat, u)
			}
		}
	}

	// A single side still holding a pet in play wins; anything else
	// (everyone out, or a stalemate with pets on both sides) is a draw.
	winner := -1
	for seat, s := range sides {
		if s.unit != nil {
			if winner >= 0 {
				winner = -1 // stalemate / >2-player safety
				break
			}
			winner = seat
		}
	}
	res.WinnerSeat = winner
	if winner >= 0 {
		res.Trophies = 1
		if g.Round == MaxRounds {
			res.Trophies = 2
		}
	}
	return res, nil
}