import { useEffect, useRef } from 'react'
import { useRealtime } from './context'
import type { KenEventEnvelope } from './kenEvent'

export interface ResourceEventsSpec {
  topic: string
  tags: readonly string[]
  filter?: Record<string, string>
  /** 资源 id 缺失时不要订阅（例如详情尚未加载）。 */
  enabled?: boolean
  /** 事件到达后执行；默认按 150ms 合并同批事件。 */
  onEvent: (envelope: KenEventEnvelope) => void
  debounceMs?: number
}

/**
 * 订阅某个资源的若干 tag，事件到达后回调。引用计数与重放由 realtime 层负责，
 * 组件卸载即退订。回调只在合并窗口内触发一次，避免一次批量写库打爆请求。
 */
export function useResourceEvents({
  topic,
  tags,
  filter,
  enabled = true,
  onEvent,
  debounceMs = 150,
}: ResourceEventsSpec): void {
  const realtime = useRealtime()
  const handler = useRef(onEvent)
  useEffect(() => {
    handler.current = onEvent
  })
  const signature = `${topic}|${tags.join(',')}|${JSON.stringify(filter ?? {})}`
  const latest = useRef({ tags, filter })
  latest.current = { tags, filter }

  useEffect(() => {
    if (!enabled || !realtime.enabled) return
    const { tags, filter } = latest.current
    let timer: number | undefined
    let queued: KenEventEnvelope | null = null
    const flush = () => {
      timer = undefined
      if (!queued) return
      const envelope = queued
      queued = null
      handler.current(envelope)
    }
    const releases = tags.map((tag) => realtime.subscribe({ topic, tag, filter, key: `${topic}:${tag}:${signature}` }))
    const off = realtime.onEnvelope((envelope) => {
      if (envelope.topic !== topic) return
      if (!tags.includes(envelope.tag)) return
      queued = envelope
      if (timer === undefined) timer = window.setTimeout(flush, debounceMs)
    })
    return () => {
      off()
      for (const release of releases) release()
      if (timer !== undefined) window.clearTimeout(timer)
    }
  }, [realtime, signature, enabled, debounceMs, topic])
}