From 70599d59b157e1ca654e3e57ee827b8c0dbca694 Mon Sep 17 00:00:00 2001
From: Victor Bodinaud <v.bodinaud@icloud.com>
Date: Thu, 8 Oct 2026 12:50:06 +0200
Subject: [PATCH] fix(sim): autoplay avoids unaffordable trades

---
 src/sim/autoplay.ts        | 16 +++++++++++-----
 tests/sim/autoplay.test.ts | 17 ++++++++++++++++-
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/sim/autoplay.ts b/src/sim/autoplay.ts
index a0cc25b..6597fc5 100644
--- a/src/sim/autoplay.ts
+++ b/src/sim/autoplay.ts
@@ -3,8 +3,8 @@ import { tick } from './clock';
 import { Customer, chooseShelfItem } from './customers';
 import { DayReport, endDay } from './day';
 import { demandWeight } from './demand';
-import { customerMinimumAsk, MONTHLY_RENT_CENTS, wholesaleCost } from './economy';
-import { itemKey, parseItemKey, stockSlot, totalQty } from './inventory';
+import { customerMinimumAsk, MONTHLY_RENT_CENTS, priceOf, wholesaleCost } from './economy';
+import { getSlot, itemKey, parseItemKey, stockSlot, totalQty } from './inventory';
 import { placeOrder } from './orders';
 import { CLOSE_MINUTES, GameState } from './state';
 import { buyBack, recordLostRequest, recordSatisfiedRequest, sell, trade } from './transactions';
@@ -25,7 +25,7 @@ export function restock(state: GameState): void {
   }
 }
 
-function serve(state: GameState, catalog: Catalog, customer: Customer): void {
+export function serveCustomer(state: GameState, catalog: Catalog, customer: Customer): void {
   switch (customer.intent) {
     case 'buy': {
       const slotId = chooseShelfItem(state, catalog, customer);
@@ -54,7 +54,13 @@ function serve(state: GameState, catalog: Catalog, customer: Customer): void {
       const slotId = chooseShelfItem(state, catalog, { ...customer, intent: 'buy' });
       if (!slotId) return;
       const game = getGame(catalog, customer.offered.gameId);
-      trade(state, catalog, customer, slotId, customerMinimumAsk(game, customer.offered.condition, 'trade'));
+      const credit = customerMinimumAsk(game, customer.offered.condition, 'trade');
+      const slotItem = getSlot(state.inventory, slotId).item;
+      if (slotItem && !customer.cardId) {
+        const diff = priceOf(state.prices, catalog, slotItem) - credit;
+        if (diff < 0 && -diff > state.cash) return;
+      }
+      trade(state, catalog, customer, slotId, credit);
       return;
     }
   }
@@ -77,7 +83,7 @@ export function autoplayDay(state: GameState, catalog: Catalog): DayReport {
   restock(state);
   while (state.minutes < CLOSE_MINUTES) {
     for (const event of tick(state, catalog, 60)) {
-      if (event.type === 'customer_arrived') serve(state, catalog, event.customer);
+      if (event.type === 'customer_arrived') serveCustomer(state, catalog, event.customer);
     }
   }
   autoOrder(state, catalog);
diff --git a/tests/sim/autoplay.test.ts b/tests/sim/autoplay.test.ts
index c176d96..58ac968 100644
--- a/tests/sim/autoplay.test.ts
+++ b/tests/sim/autoplay.test.ts
@@ -1,9 +1,11 @@
 import { describe, it, expect } from 'vitest';
-import { autoplayDay } from '../../src/sim/autoplay';
+import { autoplayDay, serveCustomer } from '../../src/sim/autoplay';
 import { createNewGame } from '../../src/sim/state';
 import { compareDates } from '../../src/sim/calendar';
 import { loadDefaultCatalog } from '../../src/sim/catalog';
 import { STARTING_CASH_CENTS } from '../../src/sim/economy';
+import { getSlot } from '../../src/sim/inventory';
+import { makeCustomer, stock, testCatalog } from './helpers';
 
 describe('autoplay', () => {
   it('plays one day end to end', () => {
@@ -32,4 +34,17 @@ describe('autoplay', () => {
       expect(s.reputation).toBeGreaterThan(0);
     }
   });
+
+  it('skips trades the shop cannot afford instead of throwing', () => {
+    const catalog = testCatalog();
+    const s = createNewGame(1);
+    const tetrisNew = { gameId: 'tetris', condition: 'new' as const };
+    stock(s, 'slot-0', tetrisNew, 1);
+    s.prices['tetris|new'] = 100;
+    s.cash = 0;
+    const customer = makeCustomer({ intent: 'trade', offered: { gameId: 'sml', condition: 'complete' } });
+    expect(() => serveCustomer(s, catalog, customer)).not.toThrow();
+    expect(getSlot(s.inventory, 'slot-0').qty).toBe(1);
+    expect(s.day.trades).toBe(0);
+  });
 });