Fix error before M7

apps/api/src/infrastructure/redis/redis.service.ts

@@ -94,6 +94,18 @@ export class RedisService implements OnModuleDestroy {
     return value;
   }
 
+  /**
+   * Claims a key only if nobody holds it. Returns false when someone already does.
+   *
+   * `SET … NX` is atomic, which is the entire point: a read-then-write claim is
+   * exactly the race the claim exists to prevent. Two simultaneous retries of
+   * the same request must not both believe they are first.
+   */
+  async setIfAbsent(key: string, value: unknown, ttlSeconds: number): Promise<boolean> {
+    const result = await this.client.set(key, JSON.stringify(value), 'EX', ttlSeconds, 'NX');
+    return result === 'OK';
+  }
+
   /**
    * Atomic fixed-window counter. Returns the count after increment so callers
    * can decide to reject.

apps/api/src/modules/checkout/checkout.controller.ts

@@ -1,11 +1,23 @@
-import { Body, Controller, Get, Inject, Param, Post, Query, Req, Res } from '@nestjs/common';
-import { ApiOperation, ApiTags } from '@nestjs/swagger';
+import {
+  Body,
+  Controller,
+  Get,
+  Headers,
+  Inject,
+  Param,
+  Post,
+  Query,
+  Req,
+  Res,
+} from '@nestjs/common';
+import { ApiHeader, ApiOperation, ApiTags } from '@nestjs/swagger';
 import type { Request, Response } from 'express';
 
 import type { Cart, Locale, Order } from '@sport/types';
 import { placeOrderSchema, type PlaceOrderInput } from '@sport/validation';
 
 import { Public } from '@/common/decorators/public.decorator';
+import { AppException } from '@/common/errors/app.exception';
 import { RequestLocale } from '@/common/i18n/locale.decorator';
 import { ZodValidationPipe } from '@/common/pipes/zod-validation.pipe';
 import { APP_CONFIG } from '@/config/app-config.module';
@@ -42,16 +54,34 @@ export class CheckoutController {
     return this.service.quote(token, locale);
   }
 
+  /**
+   * `Idempotency-Key` is required, not optional.
+   *
+   * This endpoint creates an order and reserves stock. A client that cannot be
+   * retried safely is a client that will eventually double-charge someone, and
+   * making the header optional means the one caller that forgets it is the one
+   * that does. Requiring it is a contract the storefront already honours.
+   */
   @Post('orders')
+  @ApiHeader({ name: 'Idempotency-Key', required: true, description: 'Unique per attempt' })
   @ApiOperation({ summary: 'Place the order and reserve stock' })
   async placeOrder(
     @Body(new ZodValidationPipe(placeOrderSchema)) body: PlaceOrderInput,
+    @Headers('idempotency-key') idempotencyKey: string | undefined,
     @Req() request: Request,
     @Res({ passthrough: true }) response: Response,
     @RequestLocale() locale: Locale,
   ): Promise<Order> {
+    const key = idempotencyKey?.trim();
+
+    if (!key || key.length < 8 || key.length > 128) {
+      throw AppException.badRequest(
+        'An Idempotency-Key header of 8–128 characters is required to place an order.',
+      );
+    }
+
     const { token } = resolveCartToken(request);
-    const order = await this.service.placeOrder(token, body, locale);
+    const order = await this.service.placeOrder(token, key, body, locale);
 
     // The bag is gone, so the cookie naming it should go too — otherwise the
     // next visit reads an empty cart under a stale token forever.

apps/api/src/modules/checkout/checkout.service.ts

@@ -5,9 +5,17 @@ import type { PlaceOrderInput } from '@sport/validation';
 
 import { AppException } from '@/common/errors/app.exception';
 import { PrismaService } from '@/infrastructure/prisma/prisma.service';
+import { CACHE_KEYS, CACHE_TTL } from '@/infrastructure/redis/cache-keys';
+import { RedisService } from '@/infrastructure/redis/redis.service';
 import { CartsService } from '@/modules/carts/public';
 import { OrdersService } from '@/modules/orders/public';
 
+/** What a claimed idempotency key holds while and after a placement runs. */
+interface IdempotencyRecord {
+  /** Set once the order is durably committed; absent means still in flight. */
+  orderId?: string;
+}
+
 /**
  * Turns a bag into an order.
  *
@@ -25,6 +33,7 @@ export class CheckoutService {
 
   constructor(
     private readonly prisma: PrismaService,
+    private readonly redis: RedisService,
     private readonly carts: CartsService,
     private readonly orders: OrdersService,
   ) {}
@@ -34,7 +43,61 @@ export class CheckoutService {
     return this.carts.resolveForCheckout(cartToken, locale);
   }
 
-  async placeOrder(cartToken: string, input: PlaceOrderInput, locale: Locale): Promise<Order> {
+  /**
+   * Places an order exactly once per idempotency key.
+   *
+   * The window this closes is real and unavoidable without it: the transaction
+   * commits, and then the response is lost to a dropped connection or a reload.
+   * The shopper sees a failure, presses the button again, and buys everything
+   * twice. Nothing inside the transaction can prevent that, because the problem
+   * happens after it succeeds.
+   *
+   * The key is claimed atomically before any work starts:
+   *   - claim succeeds  -> this is the first attempt; place the order and
+   *                        record its id against the key
+   *   - claim fails, id recorded -> a retry of a request that already
+   *                        succeeded; return the same order rather than a new one
+   *   - claim fails, no id yet   -> the original attempt is still running;
+   *                        refuse instead of racing it
+   *
+   * On failure the claim is released, so a genuine retry after a genuine error
+   * is not locked out for the next 24 hours.
+   */
+  async placeOrder(
+    cartToken: string,
+    idempotencyKey: string,
+    input: PlaceOrderInput,
+    locale: Locale,
+  ): Promise<Order> {
+    const key = CACHE_KEYS.idempotency('checkout', idempotencyKey);
+    const claimed = await this.redis.setIfAbsent(key, {}, CACHE_TTL.idempotency);
+
+    if (!claimed) {
+      const existing = await this.redis.get<IdempotencyRecord>(key);
+
+      if (existing?.orderId) {
+        this.logger.log(`Replaying order ${existing.orderId} for idempotency key`);
+        return this.orders.getById(existing.orderId);
+      }
+
+      throw AppException.conflict('This order is already being placed. Give it a moment.');
+    }
+
+    try {
+      return await this.place(cartToken, key, input, locale);
+    } catch (error) {
+      // Release, so the shopper can fix whatever went wrong and try again.
+      await this.redis.delete(key);
+      throw error;
+    }
+  }
+
+  private async place(
+    cartToken: string,
+    idempotencyCacheKey: string,
+    input: PlaceOrderInput,
+    locale: Locale,
+  ): Promise<Order> {
     const cart = await this.carts.resolveForCheckout(cartToken, locale);
 
     // A cart that had to correct itself is not one to charge against — the
@@ -134,9 +197,31 @@ export class CheckoutService {
       return order.id;
     });
 
-    // Only once the order is durably committed. Clearing first would lose a
-    // shopper's bag to a failed transaction.
-    await this.carts.clear(cartToken);
+    /**
+     * Record the id before anything else can fail.
+     *
+     * From here the order exists, so every later step has to be survivable. A
+     * retry that arrives after this point replays rather than duplicating.
+     */
+    await this.redis.set(idempotencyCacheKey, { orderId }, CACHE_TTL.idempotency);
+
+    /**
+     * Clearing the bag must not fail the request.
+     *
+     * The order is committed. Throwing here would report failure for something
+     * that succeeded, and the shopper's retry would be the exact double-order
+     * this method exists to prevent. A bag that outlives its order is a cosmetic
+     * problem; an order the customer was told failed is not.
+     */
+    try {
+      await this.carts.clear(cartToken);
+    } catch (error) {
+      this.logger.error(
+        `Order ${orderId} placed but its cart could not be cleared: ${
+          error instanceof Error ? error.message : String(error)
+        }`,
+      );
+    }
 
     this.logger.log(`Order ${orderId} placed with ${cart.lines.length} line(s)`);
     return this.orders.getById(orderId);

apps/api/src/modules/orders/order-fulfillment.spec.ts

@@ -0,0 +1,44 @@
+import { FULFILLMENT_STATUSES, ORDER_STATUSES, type OrderStatus } from '@sport/types';
+
+import { fulfillmentFor } from './orders.service';
+
+/**
+ * `status` and `fulfillmentStatus` are separate columns because they answer
+ * separate questions — an order can be paid and unshipped, or shipped and
+ * unpaid. Two combinations are still contradictions, and this pins them.
+ *
+ * The bug this replaces was live: fulfilling an order shipped the reserved
+ * stock and wrote a `SALE` ledger entry while leaving `fulfillmentStatus` on
+ * UNFULFILLED, so the database held orders reading "FULFILLED / UNFULFILLED".
+ * Nothing failed loudly — it just quietly disagreed with the ledger.
+ */
+describe('fulfillment status derivation', () => {
+  it('marks anything that shipped as fulfilled', () => {
+    for (const status of [ORDER_STATUSES.FULFILLED, ORDER_STATUSES.COMPLETED]) {
+      expect(fulfillmentFor(status)).toEqual({
+        fulfillmentStatus: FULFILLMENT_STATUSES.FULFILLED,
+      });
+    }
+  });
+
+  it('leaves fulfilment alone for states where nothing shipped', () => {
+    for (const status of [
+      ORDER_STATUSES.PENDING,
+      ORDER_STATUSES.CONFIRMED,
+      // Cancelling releases a reservation; it never ships anything, so
+      // UNFULFILLED stays the truth rather than being overwritten.
+      ORDER_STATUSES.CANCELLED,
+    ]) {
+      expect(fulfillmentFor(status)).toEqual({});
+    }
+  });
+
+  it('covers every status, so a new one cannot slip through untested', () => {
+    const all = Object.values(ORDER_STATUSES) as OrderStatus[];
+    expect(all).toHaveLength(5);
+
+    for (const status of all) {
+      expect(() => fulfillmentFor(status)).not.toThrow();
+    }
+  });
+});

apps/api/src/modules/orders/orders.service.ts

@@ -2,7 +2,9 @@ import { Injectable } from '@nestjs/common';
 import { Prisma } from '@prisma/client';
 
 import {
+  FULFILLMENT_STATUSES,
   ORDER_STATUSES,
+  type FulfillmentStatus,
   type OffsetPaginated,
   type Order,
   type OrderListItem,
@@ -149,6 +151,7 @@ export class OrdersService {
         where: { id, status: from },
         data: {
           status: to,
+          ...fulfillmentFor(to),
           ...(to === ORDER_STATUSES.CONFIRMED ? { confirmedAt: new Date() } : {}),
           ...(to === ORDER_STATUSES.CANCELLED
             ? { cancelledAt: new Date(), cancelReason: input.reason?.trim() ?? null }
@@ -251,3 +254,26 @@ export class OrdersService {
     }
   }
 }
+
+/**
+ * Keeps `fulfillmentStatus` honest about `status`.
+ *
+ * These are separate columns because they answer separate questions — an order
+ * can be paid and unshipped, or shipped and unpaid — but two of the values are
+ * not independent. Moving to FULFILLED physically ships the reserved stock and
+ * writes a `SALE` ledger entry; leaving `fulfillmentStatus` on UNFULFILLED
+ * afterwards produced orders reading "FULFILLED / UNFULFILLED", which is not an
+ * unusual state, it is a contradiction.
+ *
+ * CANCELLED is deliberately absent: cancelling releases a reservation and ships
+ * nothing, so UNFULFILLED remains the truth.
+ */
+export function fulfillmentFor(status: OrderStatus): { fulfillmentStatus?: FulfillmentStatus } {
+  switch (status) {
+    case ORDER_STATUSES.FULFILLED:
+    case ORDER_STATUSES.COMPLETED:
+      return { fulfillmentStatus: FULFILLMENT_STATUSES.FULFILLED };
+    default:
+      return {};
+  }
+}

apps/storefront/src/components/commerce/checkout-form.tsx

@@ -57,6 +57,17 @@ export function CheckoutForm({ locale }: { locale: Locale }) {
   const [submitting, setSubmitting] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
+  /**
+   * One key per checkout attempt, generated once and kept for the life of this
+   * form.
+   *
+   * That lifetime is exactly right. Pressing "Place order" again after a
+   * dropped response reuses it, so the server replays the order it already
+   * created instead of making a second one. Reloading the page mints a new key,
+   * which is a genuinely new attempt.
+   */
+  const [idempotencyKey] = useState(() => crypto.randomUUID());
+
   function set(key: keyof Fields, value: string) {
     setFields((current) => ({ ...current, [key]: value }));
   }
@@ -67,7 +78,7 @@ export function CheckoutForm({ locale }: { locale: Locale }) {
     setError(null);
 
     try {
-      const order = await browserApi.commerce.placeOrder(locale, {
+      const order = await browserApi.commerce.placeOrder(locale, idempotencyKey, {
         email: fields.email,
         shippingAddress: {
           fullName: fields.fullName,