import { useEffect, useState } from 'react'
import { useQueryClient } from '@tanstack/react-query'

import { Switch } from '@cfdm/ui/components/switch'
import { formatRelative } from '@/lib/format'
import { isLiveRefresh, setLiveRefresh } from '@/lib/live-refresh'

function useLatestDataUpdatedAt() {
  const queryClient = useQueryClient()
  const [updatedAt, setUpdatedAt] = useState(0)

  useEffect(() => {
    const cache = queryClient.getQueryCache()
    let queued = false
    let active = true
    const read = () => {
      let latest = 0
      for (const query of cache.getAll()) {
        if (query.getObserversCount() === 0) continue
        if (query.state.dataUpdatedAt > latest) latest = query.state.dataUpdatedAt
      }
      setUpdatedAt((prev) => (prev === latest ? prev : latest))
    }
    // Cache notifies synchronously while another route renders (observerAdded).
    const schedule = () => {
      if (queued) return
      queued = true
      queueMicrotask(() => {
        queued = false
        if (active) read()
      })
    }
    read()
    const unsubscribe = cache.subscribe(schedule)
    return () => {
      active = false
      unsubscribe()
    }
  }, [queryClient])

  return updatedAt
}

function formatUpdatedAt(updatedAt: number) {
  if (updatedAt === 0) return '—'
  return formatRelative(new Date(updatedAt).toISOString())
}

/** Компактный статус свежести слева от AppsMenu. */
export function DataFreshness() {
  const queryClient = useQueryClient()
  const updatedAt = useLatestDataUpdatedAt()
  const [live, setLive] = useState(() => isLiveRefresh())
  const [label, setLabel] = useState('—')

  useEffect(() => {
    const read = () => setLabel(formatUpdatedAt(updatedAt))
    read()
    if (updatedAt === 0) return
    const timer = window.setInterval(read, 15_000)
    return () => window.clearInterval(timer)
  }, [updatedAt])

  function handleCheckedChange(checked: boolean) {
    const next = Boolean(checked)
    setLiveRefresh(queryClient, next)
    setLive(next)
  }

  return (
    <div className="flex items-center gap-2">
      <p className="text-muted-foreground hidden items-center gap-1.5 text-xs sm:flex">
        <span className="tabular-nums">
          Обновлено{' '}
          <time dateTime={updatedAt ? new Date(updatedAt).toISOString() : undefined}>
            {label}
          </time>
        </span>
        <span aria-hidden="true">·</span>
        <span>{live ? 'Live' : 'Пауза'}</span>
      </p>
      <Switch
        size="sm"
        checked={live}
        onCheckedChange={handleCheckedChange}
        aria-label={live ? 'Выключить автообновление' : 'Включить автообновление'}
      />
    </div>
  )
}