music-collection/backend/src/album/middleware/uniqueAlbumTitle.middleware.ts

import { registerDecorator, ValidationOptions, ValidatorConstraint, ValidatorConstraintInterface } from 'class-validator';
import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';

@ValidatorConstraint({ async: true })
export class UniqueAlbumTitle implements ValidatorConstraintInterface {
  constructor(@InjectRepository(Album)
  private albumRepository: Repository<Album>
) {}

  validate(albumTitle: string) {
    return this.albumRepository.findOneBy({
      where: {
        id: title
      }).then((albumTitle) => {
      return albumTitle === undefined;
    });
  }
}

export function AlbumTitleUnique(validationOptions?: ValidationOptions) {
  return function (object: object, propertyName: string) {
    registerDecorator({
      target: object.constructor,
      propertyName: propertyName,
      options: validationOptions,
      constraints: [],
      validator: AlbumTitleUnique,
    });
  };
}