fix: craps felt and wager description cleanup

1 files changed, 46 insertions, 7 deletions

diff --git a/internal/casino/craps_rules.go b/internal/casino/craps_rules.go
index a9e52af..60a7c0f 100644
--- a/internal/casino/craps_rules.go
+++ b/internal/casino/craps_rules.go
@@ -47,6 +47,36 @@ func crapsTrueOdds(n int) (int, int) {
 		return 6, 5
 	}
 }
+
+// crapsVigUnit is the smallest stake whose true-odds profit AND 5% commission
+// are both whole credits. Buy bets pay 5% of the stake, so 20 is the base;
+// lay bets pay 5% of the profit, so the unit scales with the lay odds.
+func crapsVigUnit(kind string, n int) int {
+	if kind == "buy" {
+		return 20
+	}
+	num, den := crapsTrueOdds(n)
+	// Lay profit is stake*den/num; commission is stake*den/(20*num).
+	d := 20 * num
+	return d / gcd(den, d)
+}
+
+func gcd(a, b int) int {
+	for b != 0 {
+		a, b = b, a%b
+	}
+	return a
+}
+
+// roundUpTo returns the smallest multiple of unit that is at least n. A stake
+// that misses the exact payout/commission unit is nudged up rather than
+// rejected, since single-credit differences are noise at table stakes.
+func roundUpTo(n, unit int) int {
+	if unit <= 1 {
+		return n
+	}
+	return ((n + unit - 1) / unit) * unit
+}
 func (c CrapsConfig) oddsLimit(n int, against bool) int {
 	if c.Odds > 0 {
 		return c.Odds
@@ -66,6 +96,15 @@ func (c CrapsConfig) oddsLimit(n int, against bool) int {
 		return 5
 	}
 }
+
+// oddsDisplay is the felt label for the free-odds cap: a uniform Nx cap, or
+// the classic 3-4-5x schedule when the config leaves Odds unset.
+func (c CrapsConfig) oddsDisplay() string {
+	if c.Odds > 0 {
+		return fmt.Sprintf("%dx", c.Odds)
+	}
+	return "3x-4x-5x"
+}
 func (c TableConfig) CrapsRulesText() string {
 	r := c.Craps.Normalize()
 	if r.variant() != "bank" && r.variant() != "diceless" {
@@ -80,19 +119,19 @@ func (c TableConfig) CrapsRulesText() string {
 		odds = fmt.Sprintf("%dx", r.Odds)
 	}
 	return prefix + fmt.Sprintf("Bank Craps | Free odds %s | Field 12 pays %d:1\n"+
-		"bet <amount> on pass / dontpass / come / dontcome / field\n"+
-		"bet <amount> on place 6 / buy 4 / lay 10 / hard 8 / hop 2 3\n"+
-		"bet <amount> on seven / craps / eleven / ace-deuce / aces / boxcars / horn\n"+
-		"bet <amount> on odds pass / odds come 6 (also dontpass/dontcome)\n"+
-		"bet <amount> on fire / small / tall / all (before shooter's first roll only)\n"+
+		"bet <n> on pass / dontpass / come / dontcome / field\n"+
+		"bet <n> on place 6 / buy 4 / lay 10 / hard 8 / hop 2 3\n"+
+		"bet <n> on seven / craps / eleven / ace-deuce / aces / boxcars / horn\n"+
+		"bet <n> on odds pass / odds come 6 (also dontpass/dontcome)\n"+
+		"bet <n> on fire / small / tall / all (before shooter's first roll only)\n"+
 		"Pass/come 1:1; don't bars 12. Place 4/10 9:5, 5/9 7:5, 6/8 7:6.\n"+
-		"Buy/lay true odds; 5%% commission on buy STAKE / lay WIN, rounded up, wins only.\n"+
+		"Buy/lay true odds; 5%% commission on buy STAKE / lay WIN, rounded down, wins only.\n"+
 		"Field 2 pays 2:1; 3/4/9/10/11 pay 1:1. Hard 4/10 7:1; 6/8 9:1.\n"+
 		"Seven 4:1; craps 7:1; 11/3 15:1; 2/12 30:1; hop easy 15:1, hard 30:1.\n"+
 		"Horn splits equally across 2/3/11/12. Fire: 4/5/6 distinct made points pay 24/249/999:1.\n"+
 		"Small (2-6) / Tall (8-12) pay 34:1; All pays 175:1. Any 7 resets ATS.\n"+
 		"Place/buy/hard and come odds are OFF on come-out; lay and don't odds work.\n"+
-		"Exact payout units required; no fractional-credit rounding except commission.\n"+
+		"Stakes round up to the next exact payout/vig unit; commission never rounds up.\n"+
 		"Solo: roll anytime. Multiplayer: 10 ticks to bet, then 60 ticks for the shooter.\n"+
 		"Bets remain open until the roll. Dice rotate on seven-out.\n"+
 		"autoroll: repeat every 3 ticks on your turn (multiplayer waits 10 ticks).\n"+