import { Queue, type DefaultJobOptions } from 'bullmq'
import queueConfig from '#config/queue'
import gcConfig from '#config/gc'

const defaultJobOptions: DefaultJobOptions = {
  // Transient NNTP errors (e.g. a pooled connection the server closed) are retried.
  attempts: 3,
  backoff: { type: 'exponential', delay: 2000 },
  removeOnComplete: {
    age: gcConfig.jobs.completedAgeSeconds,
    count: gcConfig.jobs.completedMaxCount,
  },
  removeOnFail: { age: gcConfig.jobs.failedAgeSeconds },
}

/**
 * Queues are created (and connect to Redis) on first use. Ace imports every
 * command at boot, so eager queues would keep one-off commands from exiting.
 */
class QueueService {
  private readonly queues = new Map<string, Queue>()

  private queue(name: string): Queue {
    let queue = this.queues.get(name)
    if (!queue) {
      queue = new Queue(name, { connection: queueConfig.connection, defaultJobOptions })
      this.queues.set(name, queue)
    }
    return queue
  }

  get nntpFetchQueue() {
    return this.queue('nntp-fetch-queue')
  }
  get fileQueue() {
    return this.queue('file-queue')
  }
  get bodyQueue() {
    return this.queue('body-queue')
  }
  get collectionQueue() {
    return this.queue('collection-queue')
  }
  /** Complete archive listings, at low priority (ArchiveWalkService). */
  get archiveWalkQueue() {
    return this.queue('archive-walk-queue')
  }

  /** Queues no longer used by the pipeline, kept here so GC can empty them. */
  get legacy(): Queue[] {
    return [this.queue('header-queue')]
  }

  get all(): Queue[] {
    return [this.nntpFetchQueue, this.fileQueue, this.bodyQueue, this.collectionQueue, this.archiveWalkQueue]
  }

  /** Closes the queues that were opened. */
  async closeAll() {
    await Promise.all([...this.queues.values()].map((queue) => queue.close()))
    this.queues.clear()
  }
}

export default new QueueService()