Refactor: extract link between session and purchase to stripe session control

src/controller/buy.controller.ts

@@ -1,4 +1,4 @@
-import { Body, Controller, Get, Post, Redirect } from '@nestjs/common';
+import { Body, Controller, Get, Logger, Param, Post, Redirect } from '@nestjs/common';
 import { PurchaseService } from '../service/purchase.service';
 import { UserService } from '../service/user.service';
 import { PurchaseItem } from '../dto/purchase-item';
@@ -7,6 +7,8 @@ import { PurchaseStatus } from 'src/dto/purchase-status';
 
 @Controller('/buy')
 export class BuyController {
+  private readonly logger = new Logger(BuyController.name);
+
   constructor(
     private readonly purchaseService: PurchaseService,
     private readonly userService: UserService,
@@ -24,22 +26,21 @@ export class BuyController {
       PurchaseItem.PAELLA,
       quantity,
     );
-    const session = await this.stripeService.createStripeSession(
+    const { sessionUrl } = await this.stripeService.createStripeSession(
       user,
       purchase,
     );
-    this.purchaseService.attachStripeSessionToPurchase(session.id, purchase.id);
-    console.log(session);
-    return { url: session.url };
+    this.logger.debug(`Redirecting to ${sessionUrl}`);
+    return { url: sessionUrl };
   }
 
   @Post('/complete')
   public async complete(@Body('userId') userId: number) {
     const user = this.userService.getUserById(userId);
-    const session = await this.stripeService.getStripeSessionForCustomer(user);
-    const isPaid = session.payment_status == 'paid';
-    this.purchaseService.findAndTransitionPurchaseStatus(
-      session.id,
+    const { isPaid, purchaseId } =
+      await this.stripeService.getStripeSessionForCustomer(user);
+    this.purchaseService.transitionPurchaseStatus(
+      purchaseId,
       isPaid ? PurchaseStatus.COMPLETED : PurchaseStatus.IN_PROGRESS,
     );
     return { url: '/signup' };

src/dto/purchase.ts

@@ -8,5 +8,4 @@ export class Purchase {
   purchasedProduct: PurchaseItem;
   purchasedUnits: number;
   status: PurchaseStatus;
-  stripeSessionId?: string;
 }

src/dto/stripe-session.ts

@@ -0,0 +1,5 @@
+export class StripeSession {
+  sessionId: string;
+  userId: number;
+  purchaseId: number;
+}

src/service/purchase.service.ts

@@ -28,26 +28,12 @@ export class PurchaseService {
     return purchase;
   }
 
-  public attachStripeSessionToPurchase(
-    sessionId: string,
+  public transitionPurchaseStatus(
     purchaseId: number,
-  ): void {
-    const purchase = this.purchases.find(
-      (purchase) => purchase.id === purchaseId,
-    );
-    if (!purchase) {
-      throw new NotFoundException();
-    }
-
-    purchase.stripeSessionId = sessionId;
-  }
-
-  public findAndTransitionPurchaseStatus(
-    sessionId: string,
     purchaseStatus: PurchaseStatus,
   ) {
     const purchase = this.purchases.find(
-      (purchase) => purchase.stripeSessionId === sessionId,
+      (purchase) => purchase.id === purchaseId,
     );
     if (!purchase) {
       throw new NotFoundException();

src/service/stripe.service.ts

@@ -2,22 +2,20 @@ import { Injectable, NotFoundException } from '@nestjs/common';
 import { Purchase } from '../dto/purchase';
 import Stripe from 'stripe';
 import { User } from '../dto/user';
-import { NotFoundError } from 'rxjs';
+import { StripeSession } from 'src/dto/stripe-session';
 
 @Injectable()
 export class StripeService {
   private readonly stripe: Stripe;
-  private readonly stripeSessions: Map<number, string> = new Map();
+  private readonly stripeSessions: StripeSession[] = [];
 
   constructor() {
     const stripePrivateKey = process.env.STRIPE_PRIVATE_KEY!;
     this.stripe = new Stripe(stripePrivateKey);
   }
 
-  public async createStripeSession(
-    user: User,
-    purchase: Purchase,
-  ): Promise<Stripe.Response<Stripe.Checkout.Session>> {
+  public async createStripeSession(user: User, purchase: Purchase) {
+    const redirectUrl = `http://localhost:5173/buy/return?purchaseId=${purchase.id}`
     const session = await this.stripe.checkout.sessions.create({
       line_items: [
         {
@@ -26,21 +24,36 @@ export class StripeService {
         },
       ],
       mode: 'payment',
-      success_url: 'http://localhost:5173/buy/return',
-      cancel_url: 'http://localhost:5173/buy/return',
+      success_url: redirectUrl,
+      cancel_url: redirectUrl,
       payment_method_types: ['card', 'paypal'],
     });
-    this.stripeSessions.set(user.id, session.id);
-    return session;
+    const stripeSession: StripeSession = {
+      sessionId: session.id,
+      userId: user.id,
+      purchaseId: purchase.id,
+    };
+
+    this.stripeSessions.push(stripeSession);
+    return {
+      sessionUrl: session.url,
+    };
   }
 
-  public getStripeSessionForCustomer(
-    user: User,
-  ): Promise<Stripe.Response<Stripe.Checkout.Session>> {
-    const sessionId = this.stripeSessions.get(user.id);
-    if (!sessionId) {
+  public async getStripeSessionForCustomer(user: User) {
+    const stripeSession = this.stripeSessions.find(
+      (session) => session.userId === user.id,
+    );
+    if (!stripeSession) {
       throw new NotFoundException();
     }
-    return this.stripe.checkout.sessions.retrieve(sessionId);
+
+    const session = await this.stripe.checkout.sessions.retrieve(
+      stripeSession.sessionId,
+    );
+    return {
+      isPaid: session.payment_status === 'paid',
+      purchaseId: stripeSession.purchaseId,
+    };
   }
 }