import { useEffect, useRef, useState, useCallback } from 'react'
import { useTabStore } from '../stores/tabStore'
import { useAutoSaveStore } from '../stores/autoSaveStore'
import { logError } from '../lib/errorHandler'

/** Debounce delay for auto-save (ms) */
const AUTO_SAVE_DELAY = 2000

/** 模块级 ref — 状态栏等外部组件通过此函数切换自动保存 */
let _toggleAutoSave: (() => void) | null = null
export function toggleAutoSaveExternal(): void {
  _toggleAutoSave?.()
}

/**
 * Auto-save hook: subscribes to Zustand tab store, debounces content changes
 * and saves automatically after a pause in editing for file-backed tabs.
 *
 * Uses `useTabStore.getState()` and `.subscribe()` so it doesn't need to
 * re-render on every keystroke — the effect is triggered once and runs
 * reactively via the store subscription.
 *
 * Captures the tabId at debounce start so the timeout always saves the
 * correct tab even if the user switches tabs during the debounce window.
 */
export function useAutoSave(): { isAutoSaving: boolean; autoSaveEnabled: boolean; toggleAutoSave: () => void } {
  const [isAutoSaving, setIsAutoSaving] = useState(false)
  const [autoSaveEnabled, setAutoSaveEnabled] = useState(true)
  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
  const isSavingRef = useRef(false)
  const enabledRef = useRef(true)
  const mountedRef = useRef(true)

  const toggleAutoSave = useCallback(() => {
    setAutoSaveEnabled(prev => {
      const next = !prev
      enabledRef.current = next
      if (!next && timerRef.current) {
        clearTimeout(timerRef.current)
        timerRef.current = null
      }
      return next
    })
  }, [])

  // 暴露给外部（状态栏按钮）
  _toggleAutoSave = toggleAutoSave

  useEffect(() => {
    mountedRef.current = true

    // Subscribe to Zustand store — fires on every state change
    const unsub = useTabStore.subscribe((state) => {
      if (!enabledRef.current) return

      const tab = state.getActiveTab()
      if (!tab || !tab.filePath || !tab.isModified) return

      // Capture the tabId so the timeout saves the correct tab
      const tabIdToSave = tab.id

      // Debounce: clear previous timer, start new one
      if (timerRef.current) {
        clearTimeout(timerRef.current)
      }

      timerRef.current = setTimeout(async () => {
        if (isSavingRef.current) return

        // Re-read latest state; verify the captured tab still exists and is modified
        const currentState = useTabStore.getState()
        const tabToSave = currentState.tabs.find(t => t.id === tabIdToSave)
        if (!tabToSave || !tabToSave.filePath || !tabToSave.isModified) return

        isSavingRef.current = true
        if (mountedRef.current) setIsAutoSaving(true)

        try {
          if (!window.electronAPI) return
          const result = await window.electronAPI.saveFile({
            filePath: tabToSave.filePath,
            content: tabToSave.content
          })
          if (result.success && mountedRef.current) {
            currentState.setModified(tabToSave.id, false)
          }
        } catch (error) {
          logError('自动保存失败', error)
        } finally {
          if (mountedRef.current) setIsAutoSaving(false)
          isSavingRef.current = false
        }
      }, AUTO_SAVE_DELAY)
    })

    return () => {
      mountedRef.current = false
      unsub()
      if (timerRef.current) {
        clearTimeout(timerRef.current)
        timerRef.current = null
      }
    }
  }, [])

  // 同步 autoSaveEnabled / isAutoSaving 到 autoSaveStore（供状态栏读取）
  useEffect(() => {
    useAutoSaveStore.getState().setState({ autoSaveEnabled })
  }, [autoSaveEnabled])

  useEffect(() => {
    useAutoSaveStore.getState().setState({ isAutoSaving })
  }, [isAutoSaving])

  return { isAutoSaving, autoSaveEnabled, toggleAutoSave }
}