import {
  Injectable,
  Logger,
  OnApplicationBootstrap,
  OnApplicationShutdown,
} from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { CommandBus } from '@nestjs/cqrs';
import {
  EmptyTrashCommand,
  TRASH_DAYS,
} from '@task-stream/api/tracker/application';

const HOUR = 3_600_000;

/**
 * Deletes for good what has been in the trash longer than TRASH_DAYS (30
 * by default), a few minutes after start and then every six hours.
 */
@Injectable()
export class TrashScheduler
  implements OnApplicationBootstrap, OnApplicationShutdown
{
  private readonly logger = new Logger(TrashScheduler.name);
  private timers: ReturnType<typeof setTimeout>[] = [];

  constructor(
    private readonly commandBus: CommandBus,
    private readonly config: ConfigService,
  ) {}

  onApplicationBootstrap(): void {
    const first = setTimeout(() => void this.run(), 5 * 60_000);
    const every = setInterval(() => void this.run(), 6 * HOUR);
    first.unref?.();
    every.unref?.();
    this.timers = [first, every];
  }

  onApplicationShutdown(): void {
    this.timers.forEach((timer) => clearTimeout(timer));
  }

  private async run(): Promise<void> {
    const days =
      Number(this.config.get('TRASH_DAYS') ?? TRASH_DAYS) || TRASH_DAYS;
    const before = new Date(Date.now() - days * 24 * HOUR).toISOString();
    try {
      const deleted: number = await this.commandBus.execute(
        new EmptyTrashCommand(before),
      );
      if (deleted)
        this.logger.log(`Deleted ${deleted} ticket(s) from the trash`);
    } catch (error) {
      this.logger.warn(
        `Emptying the trash failed: ${(error as Error).message}`,
      );
    }
  }
}