import { setTimeout as sleep } from 'node:timers/promises'

/** After a signal, give cleanup this long before exiting anyway. */
const FORCE_EXIT_MS = 25_000

/**
 * Graceful shutdown for the long-running commands. SIGTERM (docker stop) and
 * SIGINT wake up `wait()` and `sleep()`, so workers can finish their active
 * jobs and close their connections before the process exits.
 */
class Shutdown {
  private readonly controller = new AbortController()

  constructor() {
    for (const signal of ['SIGTERM', 'SIGINT'] as const) {
      process.once(signal, () => {
        this.controller.abort()
        setTimeout(() => process.exit(0), FORCE_EXIT_MS).unref()
      })
    }
  }

  get requested(): boolean {
    return this.controller.signal.aborted
  }

  /** Resolves when a shutdown signal arrives. */
  wait(): Promise<void> {
    if (this.requested) return Promise.resolve()
    return new Promise((resolve) =>
      this.controller.signal.addEventListener('abort', () => resolve(), { once: true })
    )
  }

  /** Sleeps, but returns early on shutdown. */
  async sleep(ms: number): Promise<void> {
    try {
      await sleep(ms, undefined, { signal: this.controller.signal })
    } catch {
      // aborted by a shutdown signal
    }
  }
}

export default new Shutdown()