import { and, eq, lt } from 'drizzle-orm'
import { db } from '../../db/client.js'
import { notifications, topics } from '../../db/schema.js'
import { resolveRetentionDefaultDays } from '../admin/system-settings.js'

const CLEANUP_INTERVAL_MS = 60 * 60 * 1000 // 1 hour

// Per-topic retentionDays overrides the global default; 0 means "forever".
// See docs/phase1/03-database-model.md, "Retention cleanup".
export async function runRetentionCleanup(): Promise<number> {
  const topicRows = await db.select().from(topics)
  const retentionDefaultDays = await resolveRetentionDefaultDays()
  let totalDeleted = 0

  for (const topic of topicRows) {
    const retentionDays = topic.retentionDays ?? retentionDefaultDays
    if (retentionDays === 0) continue

    const cutoff = new Date(Date.now() - retentionDays * 24 * 60 * 60 * 1000)
    const deleted = await db
      .delete(notifications)
      .where(and(eq(notifications.topicId, topic.id), lt(notifications.createdAt, cutoff)))
      .returning({ id: notifications.id })

    totalDeleted += deleted.length
  }

  return totalDeleted
}

export function startRetentionCleanupJob(
  onError: (err: unknown) => void = console.error,
): NodeJS.Timeout {
  const run = () => {
    runRetentionCleanup().catch(onError)
  }
  run() // catch up on anything overdue from before this boot
  const timer = setInterval(run, CLEANUP_INTERVAL_MS)
  timer.unref() // never block process shutdown just to keep this alive
  return timer
}