import {
  DataSource,
  EntitySubscriberInterface,
  EventSubscriber,
  RemoveEvent,
} from "typeorm";
import { Inject, Injectable, Logger } from "@nestjs/common";
import { InjectDataSource } from "@nestjs/typeorm";
import { LOGGER } from "../../log/log.constants";
import { LocalizedStringEntity } from "./localized-string.entity";
import { LocalizedMediaEntity } from "./localized-media.entity";

/**
 * LocaleSubscriber is an EntitySubscriber that listens to removal events
 * for entities that have relationships with LocalizedStringEntity or LocalizedMediaEntity.
 * When such an entity is removed, LocaleSubscriber will also remove
 * the associated LocalizedStringEntity or LocalizedMediaEntity instances.
 *
 * @example
 * class MyEntity {
 *   @ManyToMany(() => LocalizedStringEntity, { cascade: true })
 *   @JoinTable()
 *   firstName: LocalizedStringEntity[];
 * }
 *
 * const myEntity = new MyEntity();
 * entityManager.remove(myEntity); // will trigger LocaleSubscriber to remove related LocalizedStringEntity instances
 */
@Injectable()
@EventSubscriber()
export class LocaleSubscriber implements EntitySubscriberInterface {
  /**
   * Constructs a new LocaleSubscriber instance.
   *
   * @param logger - The Logger instance used for logging messages.
   * @param dataSource - The DataSource instance used to access the connection and its subscribers.
   */
  constructor(
    @Inject(LOGGER) protected readonly logger: Logger,
    @InjectDataSource() private readonly dataSource: DataSource,
  ) {
    dataSource.manager.connection.subscribers.push(this);
  }

  /**
   * The afterRemove event is triggered when an entity is removed.
   * If the removed entity has relationships with LocalizedStringEntity instances,
   * the related LocalizedStringEntity instances will also be removed.
   *
   * @param event - The RemoveEvent instance containing information about the removed entity.
   * @returns A Promise that resolves when the removal of related LocalizedStringEntity instances is complete.
   */
  async afterRemove(event: RemoveEvent<any>): Promise<void> {
    const entity = event.entity;
    if (!entity) {
      return;
    }
    const localizedStringProperties = Object.values(entity).filter((value) => {
      return (
        Array.isArray(value) &&
        value.length > 0 &&
        value[0] instanceof LocalizedStringEntity
      );
    });
    if (localizedStringProperties.length > 0) {
      this.logger.verbose(
        `Removing related LocalizedStringEntity entities for ${entity.constructor.name} with ID ${event.entityId}`,
      );
      for (const relatedEntities of localizedStringProperties as LocalizedStringEntity[][]) {
        for (const relatedEntity of relatedEntities) {
          this.logger.verbose(
            `Removing LocalizedStringEntity with ID ${relatedEntity.id}`,
          );
          await event.manager.remove(relatedEntity);
          this.logger.verbose(
            `LocalizedStringEntity with ID ${relatedEntity.id} removed`,
          );
        }
      }
    }

    const localizedMediaProperties = Object.values(entity).filter((value) => {
      return (
        Array.isArray(value) &&
        value.length > 0 &&
        value[0] instanceof LocalizedMediaEntity
      );
    });
    if (localizedMediaProperties.length > 0) {
      this.logger.verbose(
        `Removing related LocalizedMediaEntity entities for ${entity.constructor.name} with ID ${event.entityId}`,
      );
      for (const relatedEntities of localizedMediaProperties as LocalizedMediaEntity[][]) {
        for (const relatedEntity of relatedEntities) {
          this.logger.verbose(
            `Removing LocalizedMediaEntity with ID ${relatedEntity.id}`,
          );
          await event.manager.remove(relatedEntity);
          this.logger.verbose(
            `LocalizedMediaEntity with ID ${relatedEntity.id} removed`,
          );
        }
      }
    }
  }
}