zioinfo-mail/app/hooks/useOfflineCache.ts

import { useState, useEffect, useCallback } from 'react'
import * as SecureStore from 'expo-secure-store'
import NetInfo from '@react-native-community/netinfo'

interface CacheOptions {
  ttlMs?: number  // 캐시 유효 시간 (ms), 기본 5분
}

export function useOfflineCache<T>(
  cacheKey: string,
  fetcher: () => Promise<{ data: T }>,
  options: CacheOptions = {}
) {
  const { ttlMs = 5 * 60 * 1000 } = options
  const [data,     setData]     = useState<T | null>(null)
  const [isOffline, setOffline] = useState(false)
  const [loading,   setLoading] = useState(true)
  const [cachedAt,  setCachedAt] = useState<Date | null>(null)

  useEffect(() => {
    const unsub = NetInfo.addEventListener(state => {
      setOffline(!(state.isConnected ?? true))
    })
    return () => unsub()
  }, [])

  const load = useCallback(async () => {
    setLoading(true)
    try {
      if (!isOffline) {
        const result = await fetcher()
        setData(result.data)
        const now = new Date()
        setCachedAt(now)
        await SecureStore.setItemAsync(cacheKey, JSON.stringify({
          data: result.data, ts: now.toISOString(),
        }))
      } else {
        const raw = await SecureStore.getItemAsync(cacheKey)
        if (raw) {
          const { data: cached, ts } = JSON.parse(raw)
          const age = Date.now() - new Date(ts).getTime()
          setData(cached)
          setCachedAt(new Date(ts))
          if (age > ttlMs) {
            console.warn(`[OfflineCache] ${cacheKey} 캐시 만료 (${Math.floor(age / 60000)}분 전)`)
          }
        }
      }
    } catch {
      const raw = await SecureStore.getItemAsync(cacheKey)
      if (raw) {
        const { data: cached, ts } = JSON.parse(raw)
        setData(cached); setCachedAt(new Date(ts))
      }
    } finally { setLoading(false) }
  }, [cacheKey, fetcher, isOffline, ttlMs])

  useEffect(() => { load() }, [load])

  return { data, isOffline, loading, cachedAt, reload: load }
}