fix: harden engine across casino, economy, concurrency, security, and content

1 files changed, 27 insertions, 4 deletions

diff --git a/internal/casino/cards.go b/internal/casino/cards.go
index b1c2cbb..27da8aa 100644
--- a/internal/casino/cards.go
+++ b/internal/casino/cards.go
@@ -68,12 +68,17 @@ func (s *shoe) shuffle() {
 	s.rng.Shuffle(len(s.cards), func(i, j int) { s.cards[i], s.cards[j] = s.cards[j], s.cards[i] })
 }
 
+// remaining reports the cards left in the shoe.
+func (s *shoe) remaining() int { return len(s.cards) }
+
 func (s *shoe) draw() card {
 	if len(s.cards) == 0 {
-		// The shoe ran dry mid-round (only possible when the configured
-		// deck count is very small relative to the table): rebuild it
-		// rather than panic. The cut-card reshuffle itself happens
-		// between rounds via shuffleIfDue, never per draw.
+		// Shuffle-through: if the shoe runs out mid-round it is rebuilt from
+		// all decks, so a card already dealt this round can reappear. This
+		// matches real blackjack, where an exhausted shoe is shuffled through
+		// mid-round; ensureForRound makes it rare by reshuffling at round
+		// boundaries, and this keeps a directly-constructed table from
+		// panicking.
 		s.shuffle()
 	}
 	card := s.cards[len(s.cards)-1]
@@ -81,6 +86,24 @@ func (s *shoe) draw() card {
 	return card
 }
 
+// ensureForRound reshuffles when the shoe is unlikely to cover the round that
+// is about to be dealt. It MUST be called at a round boundary, before any card
+// of that round is dealt: a rebuild there cannot redeal a card the current
+// round already holds, which is exactly what draw()'s exhausted-shoe
+// shuffle-through does. need is a heuristic estimate of the cards one round
+// can consume (see blackjackRoundCards/baccaratRoundCards), not a certified
+// maximum, so coverage is best-effort.
+func (s *shoe) ensureForRound(need int) {
+	if s.decks <= 0 {
+		// No deck composition to refill from: this is a synthetic shoe with
+		// an explicit card script (tests), which must not be replaced.
+		return
+	}
+	if len(s.cards) < need {
+		s.shuffle()
+	}
+}
+
 // shuffleIfDue reshuffles the shoe once its remaining cards have fallen
 // to the shuffleAt fraction (the cut card). It must be called at round
 // boundaries only — shuffling between individual draws would let cards