feat: finish working on account transaction webhook

src/card/services/account.service.ts

@@ -1,4 +1,4 @@
-import { Injectable } from '@nestjs/common';
+import { Injectable, UnprocessableEntityException } from '@nestjs/common';
 import { Account } from '../entities/account.entity';
 import { AccountRepository } from '../repositories/account.repository';
 
@@ -9,4 +9,30 @@ export class AccountService {
   createAccount(accountId: string): Promise<Account> {
     return this.accountRepository.createAccount(accountId);
   }
+
+  async getAccountByReferenceNumber(accountReference: string): Promise<Account> {
+    const account = await this.accountRepository.getAccountByReferenceNumber(accountReference);
+    if (!account) {
+      throw new UnprocessableEntityException('ACCOUNT.NOT_FOUND');
+    }
+    return account;
+  }
+
+  async creditAccountBalance(accountReference: string, amount: number) {
+    return this.accountRepository.topUpAccountBalance(accountReference, amount);
+  }
+
+  async decreaseAccountBalance(accountReference: string, amount: number) {
+    const account = await this.getAccountByReferenceNumber(accountReference);
+    /**
+     * While there is no need to check for insufficient balance  because this is a webhook handler,
+     * I just added this check to ensure we don't have corruption in our data especially if this service is used elsewhere.
+     */
+
+    if (account.balance < amount) {
+      throw new UnprocessableEntityException('ACCOUNT.INSUFFICIENT_BALANCE');
+    }
+
+    return this.accountRepository.decreaseAccountBalance(accountReference, amount);
+  }
 }