3374f79ea11b.diff

3374f79ea11b.diff

 -1,11 +1,15 @@
 import { Injectable } from '@nestjs/common';
 import { BookRepository } from './book-repository.port';
+import { BookAlreadyExistsError } from './book-already-exists.error';

 @Injectable()
 export class AddBookUseCase {
   constructor(private readonly bookRepository: BookRepository) {}

-  execute(book: { title: string }) {
+  async execute(book: { title: string }) {
+    if (await this.bookRepository.doesBookExist(book.title)) {
+      throw new BookAlreadyExistsError(book.title);
+    }
     return this.bookRepository.save(book);
   }
 }