From 06c3891045b3035cf0d2cc47a61049d31716b360 Mon Sep 17 00:00:00 2001
From: syntaxbullet <syntaxbullet@protonmail.com>
Date: Mon, 6 Apr 2026 14:50:40 +0200
Subject: [PATCH] fix: Correct PnL calculation by using betAmount in net profit
 computation

- Add betAmount field to BlackjackState to track the base bet
- Fix finishPlayerTurns: multiply hand.bet by state.betAmount for actual money bets
- Fix GameServer: roundPayouts are already gross payouts (not multipliers)
- Update cumulative PnL calculation to correctly subtract actual bet amount
- Add betAmount support to riggedState test helper
---
 api/src/games/GameServer.ts                     |  7 +++----
 shared/games/blackjack/blackjack.plugin.test.ts |  2 ++
 shared/games/blackjack/blackjack.plugin.ts      | 10 ++++++----
 shared/games/blackjack/blackjack.types.ts       |  2 ++
 4 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/api/src/games/GameServer.ts b/api/src/games/GameServer.ts
index b6ff568..92e12cd 100644
--- a/api/src/games/GameServer.ts
+++ b/api/src/games/GameServer.ts
@@ -95,10 +95,9 @@ export class GameServer {
             const gameName = gameRegistry.get(room.gameSlug)?.name ?? "Game";
             const payoutDetails: Record<string, { net: number }> = {};
 
-            for (const [playerId, multiplier] of Object.entries(roundPayouts)) {
-                if (multiplier <= 0) continue;
-                const grossPayout = Math.floor(betAmount * multiplier);
-                const netProfit = grossPayout - betAmount; // Calculate net profit (gross payout minus original bet)
+            for (const [playerId, grossPayout] of Object.entries(roundPayouts)) {
+                // roundPayout is already the gross payout amount (not a multiplier)
+                const netProfit = Math.floor(grossPayout) - betAmount; // Calculate net profit (gross payout minus original bet)
                 try {
                     await economyService.modifyUserBalance(
                         playerId,
diff --git a/shared/games/blackjack/blackjack.plugin.test.ts b/shared/games/blackjack/blackjack.plugin.test.ts
index 49da3c6..d44cfe1 100644
--- a/shared/games/blackjack/blackjack.plugin.test.ts
+++ b/shared/games/blackjack/blackjack.plugin.test.ts
@@ -34,6 +34,7 @@ function riggedState(overrides: {
     activePlayerIndex?: number;
     phase?: "betting" | "player_turns" | "resolved";
     roundNumber?: number;
+    betAmount?: number;
 }): BlackjackState {
     return {
         deck: overrides.deck ?? [makeCard("5"), makeCard("6"), makeCard("7"), makeCard("8"), makeCard("9"), makeCard("10")],
@@ -43,6 +44,7 @@ function riggedState(overrides: {
         activePlayerIndex: overrides.activePlayerIndex ?? 0,
         phase: overrides.phase ?? "player_turns",
         roundNumber: overrides.roundNumber ?? 1,
+        betAmount: overrides.betAmount ?? 0,
     };
 }
 
diff --git a/shared/games/blackjack/blackjack.plugin.ts b/shared/games/blackjack/blackjack.plugin.ts
index 447c65a..1725aa3 100644
--- a/shared/games/blackjack/blackjack.plugin.ts
+++ b/shared/games/blackjack/blackjack.plugin.ts
@@ -196,10 +196,10 @@ function finishPlayerTurns(state: BlackjackState): BlackjackState {
         
         // Then calculate PnL based on resolved hands
         const roundPayout = calculateRoundPayouts({ [id]: { ...seat, hands: resolvedHands } });
-        const roundPnl = roundPayout[id] ?? 0;
+        const roundPayoutMoney = roundPayout[id] ?? 0;
         // Subtract the total bet amount to get net profit/loss
-        const roundBetTotal = seat.hands.reduce((sum, h) => sum + h.bet, 0);
-        const roundNetPnl = roundPayout[id] ? roundPayout[id] - roundBetTotal : -roundBetTotal;
+        const roundBetTotal = seat.hands.reduce((sum, h) => sum + (h.bet * state.betAmount), 0);
+        const roundNetPnl = roundPayoutMoney ? roundPayoutMoney - roundBetTotal : -roundBetTotal;
         
         resolvedSeats[id] = {
             ...seat,
@@ -361,7 +361,8 @@ export const blackjackPlugin: GamePlugin<BlackjackState, BlackjackAction> = {
     maxPlayers: 6,
     manualStart: true,
 
-    createInitialState(players: string[], _options?: Record<string, unknown>): BlackjackState {
+    createInitialState(players: string[], options?: Record<string, unknown>): BlackjackState {
+        const betAmount = typeof options?.betAmount === 'number' ? options.betAmount : 0;
         const seats: Record<string, PlayerSeat> = {};
         for (const pid of players) {
             seats[pid] = {
@@ -380,6 +381,7 @@ export const blackjackPlugin: GamePlugin<BlackjackState, BlackjackAction> = {
             activePlayerIndex: -1,
             phase: "betting",
             roundNumber: 1,
+            betAmount,
         };
     },
 
diff --git a/shared/games/blackjack/blackjack.types.ts b/shared/games/blackjack/blackjack.types.ts
index 4066225..8850f10 100644
--- a/shared/games/blackjack/blackjack.types.ts
+++ b/shared/games/blackjack/blackjack.types.ts
@@ -41,6 +41,8 @@ export interface BlackjackState {
     activePlayerIndex: number;
     phase: "betting" | "player_turns" | "resolved";
     roundNumber: number;
+    /** The base bet amount for this game (0 for free play). */
+    betAmount: number;
 }
 
 // ── Actions ──