modern-in-app-purchase

A modern, robust, and type-safe in-app purchase validation library for Apple and Google using their official SDKs (@apple/app-store-server-library and googleapis).

Installation

npm install modern-in-app-purchase

Usage with NestJS

This library is designed to be easily integrated into a NestJS application. Below is an example of how to wrap it in a NestJS Service and Module.

1. Create a Configuration Service or use ConfigModule

Ensure you have your Apple and Google credentials available in your environment variables.

2. Create the IAP Service

Create a service to wrap the library's functions.

// in-app-purchase.service.ts
import { Injectable, OnModuleInit } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import iap, { Platform, Receipt, ValidationResponse } from 'modern-in-app-purchase';

@Injectable()
export class InAppPurchaseService implements OnModuleInit {
  constructor(private readonly configService: ConfigService) {}

  onModuleInit() {
    // Configure the library once when the module initializes
    iap.config({
      apple: {
        issuerId: this.configService.get<string>('APPLE_ISSUER_ID'),
        keyId: this.configService.get<string>('APPLE_KEY_ID'),
        privateKey: this.configService.get<string>('APPLE_PRIVATE_KEY'),
        bundleId: this.configService.get<string>('APPLE_BUNDLE_ID'),
        environment: this.configService.get<'Sandbox' | 'Production'>('APPLE_ENVIRONMENT', 'Sandbox'),
      },
      google: {
        clientEmail: this.configService.get<string>('GOOGLE_CLIENT_EMAIL'),
        privateKey: this.configService.get<string>('GOOGLE_PRIVATE_KEY').replace(/\\n/g, '\n'),
      },
    });
  }

  /**
   * Validate a receipt for a given platform
   * @param platform 'apple' or 'google'
   * @param receipt The receipt data containing transactionId or purchaseToken
   */
  async validateReceipt(platform: Platform, receipt: Receipt): Promise<ValidationResponse> {
    return await iap.validate(platform, receipt);
  }

  /**
   * Check if a validation response indicates a valid subscription/purchase
   */
  isValid(response: ValidationResponse): boolean {
    return iap.isValid(response);
  }
}

3. Create the IAP Module

// in-app-purchase.module.ts
import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import { InAppPurchaseService } from './in-app-purchase.service';

@Module({
  imports: [ConfigModule],
  providers: [InAppPurchaseService],
  exports: [InAppPurchaseService],
})
export class InAppPurchaseModule {}

4. Use in your Resolver or Controller

// subscription.resolver.ts
import { Resolver, Mutation, Args } from '@nestjs/graphql';
import { InAppPurchaseService } from './in-app-purchase.service';
import { Platform } from 'modern-in-app-purchase';

@Resolver()
export class SubscriptionResolver {
  constructor(private readonly iapService: InAppPurchaseService) {}

  @Mutation(() => Boolean)
  async verifySubscription(
    @Args('platform') platform: Platform, // 'apple' or 'google'
    @Args('transactionId', { nullable: true }) transactionId?: string, // for Apple
    @Args('productId', { nullable: true }) productId?: string, // for Google
    @Args('purchaseToken', { nullable: true }) purchaseToken?: string, // for Google
  ) {
    // Validate the receipt
    const response = await this.iapService.validateReceipt(platform, {
      transactionId,
      productId,
      purchaseToken,
    });

    if (this.iapService.isValid(response)) {
      // The receipt is valid. Update the user's subscription status in your database.
      console.log('Subscription is valid!', response);
      return true;
    } else {
      // The receipt is invalid or expired.
      console.log('Subscription validation failed:', response.message);
      return false;
    }
  }
}

Types

This library provides full TypeScript support. You can import the types directly:

import { 
  ConfigOptions, 
  Platform, 
  Receipt, 
  ValidationResponse,
  APPLE, 
  GOOGLE 
} from 'modern-in-app-purchase';