import { BaseCommand } from '@adonisjs/core/ace'
import type { CommandOptions } from '@adonisjs/core/types/ace'
import { setTimeout as sleep } from 'node:timers/promises'
import { Prefetcher } from '#services/prefetcher'
import Planner from '#services/planner'
import FragmentMerger from '#services/fragment_merger'
import NntpPool from '#services/nntp_pool'

const TICK_MS = 2000
const PLAN_EVERY_MS = 60 * 60 * 1000
const MERGE_EVERY_MS = 60 * 1000
const MERGE_BUDGET_MS = 30 * 1000

/**
 * The coordinator's background work (REBUILD.md, part 1): the prefetcher,
 * merging fragments of finished ranges every minute, and planning ranges
 * for new articles every hour. The API (leases, stream,
 * batches) runs in the web server.
 */
export default class CoordinatorRun extends BaseCommand {
  static commandName = 'coordinator:run'
  static description = 'Prefetches ranges into the spool and plans new ones'
  static options: CommandOptions = { startApp: true, staysAlive: true }

  async run() {
    const prefetcher = new Prefetcher()
    let stopping = false
    let stopped: () => void
    const done = new Promise<void>((resolve) => (stopped = resolve))
    // bin/console turns SIGTERM into app.terminate: wait for the spooling in flight first.
    this.app.terminating(async () => {
      stopping = true
      prefetcher.stop()
      await done
    })
    let plannedAt = 0
    let mergedAt = 0
    this.logger.info('Coordinator started.')
    while (!stopping) {
      try {
        if (Date.now() - plannedAt >= PLAN_EVERY_MS) {
          plannedAt = Date.now()
          const { groups, ranges } = await Planner.planAll()
          if (ranges > 0) this.logger.info(`Planned ${ranges} ranges over ${groups} groups.`)
        }
        if (Date.now() - mergedAt >= MERGE_EVERY_MS) {
          mergedAt = Date.now()
          // Rounds until nothing more can be decided, or MERGE_BUDGET_MS.
          const totals = { completed: 0, incomplete: 0, waiting: 0 }
          while (!stopping && Date.now() - mergedAt < MERGE_BUDGET_MS) {
            const merged = await FragmentMerger.run()
            totals.completed += merged.completed
            totals.incomplete += merged.incomplete
            totals.waiting = merged.waiting
            if (merged.files === 0) break
          }
          if (totals.completed || totals.incomplete) this.logger.info(`Fragments: ${totals.completed} files completed, ${totals.incomplete} incomplete, ${totals.waiting} waiting.`)
        }
        await prefetcher.tick()
      } catch (error: any) {
        this.logger.error(`Coordinator round failed: ${error.message}`)
      }
      await sleep(TICK_MS)
    }
    while (prefetcher.active > 0) await sleep(200)
    await NntpPool.close()
    stopped!()
  }
}