1 files changed, 131 insertions, 0 deletions
diff --git a/internal/casino/house_edge_baccarat.go b/internal/casino/house_edge_baccarat.go
new file mode 100644
index 0000000..1598fd6
--- /dev/null
+++ b/internal/casino/house_edge_baccarat.go
@@ -0,0 +1,131 @@
+package casino
+
+import (
+	"strings"
+	"sync"
+)
+
+type baccaratProbabilities struct {
+	player, banker, tie, dragon, panda, six float64
+}
+
+var baccaratEdgeCache sync.Map // deck count -> baccaratProbabilities
+
+func baccaratHouseEdge(cfg TableConfig, bet string) HouseEdge {
+	c := cfg.Baccarat.Normalize()
+	spot := strings.Fields(bet)
+	if len(spot) == 0 {
+		return unknownEdge("unrecognized baccarat target")
+	}
+	p := baccaratFreshProbabilities(c.Decks)
+	var e HouseEdge
+	switch spot[0] {
+	case "player":
+		e = edge(p.banker - p.player)
+	case "banker":
+		loss := p.player - c.BankerPayout*p.banker
+		if c.Variant == BaccaratSuper6 {
+			loss += .5 * p.six
+		}
+		if c.Variant == BaccaratEZ {
+			loss += p.dragon
+		}
+		e = edge(loss)
+	case "tie":
+		e = edge(1 - (1+c.TiePayout)*p.tie)
+	case "player_pair", "banker_pair":
+		e = edge(1 - 12*float64(4*c.Decks-1)/float64(52*c.Decks-1))
+	case "dragon_7":
+		e = edge(1 - 41*p.dragon)
+	case "panda_8":
+		e = edge(1 - 26*p.panda)
+	case "super_6":
+		e = edge(1 - 13*p.six)
+	default:
+		return unknownEdge("unrecognized baccarat target")
+	}
+	e.Note = "fresh shoe; before fractional-credit rounding"
+	return e
+}
+
+// Enumerate value sequences WITHOUT replacement from the configured shoe.
+// Tens/J/Q/K coalesce into value zero; rank-pair probability is separately
+// exact by symmetry. At most 10^6 branches, cached by deck count. Uses the
+// same banker tableau as playTableau; no sampled or generic casino rates.
+func baccaratFreshProbabilities(decks int) baccaratProbabilities {
+	if v, ok := baccaratEdgeCache.Load(decks); ok {
+		return v.(baccaratProbabilities)
+	}
+	var out baccaratProbabilities
+	counts := [10]int{}
+	for i := range counts {
+		counts[i] = 4 * decks
+	}
+	counts[0] = 16 * decks
+	var cards [6]int
+	var deal func(int, float64)
+	finish := func(pt, bt, pn, bn int, prob float64) {
+		switch {
+		case pt > bt:
+			out.player += prob
+			if pn == 3 && pt == 8 {
+				out.panda += prob
+			}
+		case bt > pt:
+			out.banker += prob
+			if bn == 3 && bt == 7 {
+				out.dragon += prob
+			}
+			if bt == 6 {
+				out.six += prob
+			}
+		default:
+			out.tie += prob
+		}
+	}
+	deal = func(n int, prob float64) {
+		if n >= 4 {
+			pt, bt := (cards[0]+cards[1])%10, (cards[2]+cards[3])%10
+			if pt >= 8 || bt >= 8 {
+				finish(pt, bt, 2, 2, prob)
+				return
+			}
+			playerDraw := pt <= 5
+			if playerDraw && n == 4 { // draw Player's third below
+			} else {
+				third, pn := -1, 2
+				if playerDraw {
+					third = cards[4]
+					pt = (pt + third) % 10
+					pn = 3
+				}
+				bankerDraw := (third < 0 && bt <= 5) || (third >= 0 && bankerDraws(bt, third))
+				if !bankerDraw {
+					finish(pt, bt, pn, 2, prob)
+					return
+				}
+				needed := 5
+				if playerDraw {
+					needed = 6
+				}
+				if n == needed {
+					finish(pt, (bt+cards[n-1])%10, pn, 3, prob)
+					return
+				}
+			}
+		}
+		remaining := float64(52*decks - n)
+		for value, count := range counts {
+			if count == 0 {
+				continue
+			}
+			counts[value]--
+			cards[n] = value
+			deal(n+1, prob*float64(count)/remaining)
+			counts[value]++
+		}
+	}
+	deal(0, 1)
+	baccaratEdgeCache.Store(decks, out)
+	return out
+}