/**
 * PushNotificationToggle - 推送通知开关组件
 *
 * 显示当前推送订阅状态，提供订阅/取消订阅的切换按钮。
 * 可在设置页面或任意位置嵌入使用。
 *
 * 交互流程：
 * 1. 检查浏览器支持 → 不支持则显示提示
 * 2. 检查通知权限 → 未授权则引导用户授权
 * 3. 检查当前订阅状态 → 显示对应按钮
 * 4. 点击按钮 → 执行订阅/取消订阅 + 后端同步
 */

import React, { useState, useEffect, useCallback } from 'react'
import { useTranslation } from '../i18n'
import {
  isPushSupported,
  getNotificationPermission,
  requestNotificationPermission,
  subscribeToPush,
  unsubscribeFromPush,
  getPushSubscription,
  registerSubscriptionWithBackend,
  unregisterSubscriptionFromBackend,
} from '../utils/pushNotifications'

// ================================================================
// 状态枚举
// ================================================================

type SubscriptionStatus =
  | 'unsupported'   // 浏览器不支持 Push
  | 'loading'       // 正在检查/执行操作
  | 'denied'        // 通知权限被拒绝
  | 'unsubscribed'  // 未订阅
  | 'subscribed'    // 已订阅

// ================================================================
// PushNotificationToggle 组件
// ================================================================

export default function PushNotificationToggle() {
  const { t } = useTranslation()
  const [status, setStatus] = useState<SubscriptionStatus>('loading')
  const [error, setError] = useState<string | null>(null)
  const [subscriptionEndpoint, setSubscriptionEndpoint] =
    useState<string | null>(null)

  // ----------------------------------------------------------
  // 初始化：检查当前状态
  // ----------------------------------------------------------

  useEffect(() => {
    checkStatus()
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [])

  const checkStatus = useCallback(async () => {
    setError(null)

    // 1. 检查浏览器支持
    if (!isPushSupported()) {
      setStatus('unsupported')
      return
    }

    // 2. 检查通知权限
    const permission = getNotificationPermission()
    if (permission === 'denied') {
      setStatus('denied')
      return
    }

    // 3. 检查当前订阅
    setStatus('loading')
    try {
      const sub = await getPushSubscription()
      if (sub) {
        setSubscriptionEndpoint(sub.endpoint || null)
        setStatus('subscribed')
      } else {
        setSubscriptionEndpoint(null)
        setStatus('unsubscribed')
      }
    } catch {
      setSubscriptionEndpoint(null)
      setStatus('unsubscribed')
    }
  }, [])

  // ----------------------------------------------------------
  // 开启通知
  // ----------------------------------------------------------

  const handleEnable = useCallback(async () => {
    setError(null)
    setStatus('loading')

    try {
      console.log('[PushToggle] 开始开启推送通知...')

      // 先请求通知权限（如果尚未授予）
      let permission = getNotificationPermission()
      if (permission !== 'granted') {
        permission = await requestNotificationPermission()
      }

      if (permission !== 'granted') {
        console.warn('[PushToggle] 通知权限未授予')
        setStatus('denied')
        setError(t('components.push.permissionNotGranted'))
        return
      }

      // 订阅 Push（调用浏览器 PushManager.subscribe）
      console.log('[PushToggle] 调用 subscribeToPush...')
      const subscription = await subscribeToPush()
      console.log('[PushToggle] 浏览器订阅成功:', subscription.endpoint)

      // 立刻更新 UI 状态为已订阅（不等后端同步完成）
      setSubscriptionEndpoint(subscription.endpoint || null)
      setStatus('subscribed')
      console.log('[PushToggle] UI 已切换为已订阅状态')

      // 后台同步到后端（不阻塞 UI）
      try {
        console.log('[PushToggle] 同步订阅到后端...')
        await registerSubscriptionWithBackend(subscription)
        console.log('[PushToggle] 后端订阅注册成功')
      } catch (backendErr) {
        console.warn('[PushToggle] 后端同步失败（浏览器订阅已生效）:', backendErr)
        setError(t('components.push.backendSyncFailed'))
      }
    } catch (err) {
      console.error('[PushToggle] 开启失败:', err)
      const message =
        err instanceof Error ? err.message : t('components.push.enableFailed')
      setError(message)
      // 回退到检查当前实际订阅状态
      await checkStatus()
    }
  }, [checkStatus])

  // ----------------------------------------------------------
  // 关闭通知
  // ----------------------------------------------------------

  const handleDisable = useCallback(async () => {
    setError(null)
    setStatus('loading')

    try {
      // 获取当前端点用于后端取消注册
      const sub = await getPushSubscription()
      const endpoint = sub?.endpoint || subscriptionEndpoint

      // 取消浏览器 Push 订阅
      await unsubscribeFromPush()

      // 从后端取消注册
      if (endpoint) {
        try {
          await unregisterSubscriptionFromBackend(endpoint)
        } catch {
          // 后端取消失败不影响前端状态
          console.warn('[PushToggle] 后端取消订阅失败，已在前端取消')
        }
      }

      setSubscriptionEndpoint(null)
      setStatus('unsubscribed')
    } catch (err) {
      const message =
        err instanceof Error ? err.message : t('components.push.disableFailed')
      setError(message)
      await checkStatus()
    }
  }, [subscriptionEndpoint, checkStatus])

  // ----------------------------------------------------------
  // 渲染：不支持
  // ----------------------------------------------------------

  if (status === 'unsupported') {
    return (
      <div className="card p-4">
        <div className="flex items-start gap-3">
          <div className="shrink-0 mt-0.5">
            <svg
              className="w-5 h-5 text-surface-400"
              fill="none"
              stroke="currentColor"
              strokeWidth={2}
              viewBox="0 0 24 24"
            >
              <path
                strokeLinecap="round"
                strokeLinejoin="round"
                d="M18.364 18.364A9 9 0 005.636 5.636m12.728 12.728A9 9 0 015.636 5.636m12.728 12.728L5.636 5.636"
              />
            </svg>
          </div>
          <div>
            <p className="text-sm font-medium text-gray-700">{t('components.push.notSupported')}</p>
            <p className="text-xs text-surface-400 mt-0.5">
              {t('components.push.browserNotSupported')}
            </p>
          </div>
        </div>
      </div>
    )
  }

  // ----------------------------------------------------------
  // 渲染：加载中
  // ----------------------------------------------------------

  if (status === 'loading') {
    return (
      <div className="card p-4">
        <div className="flex items-center gap-3">
          <div className="w-5 h-5 border-2 border-emerald-500 border-t-transparent rounded-full animate-spin" />
          <p className="text-sm text-surface-400">{t('components.push.checking')}</p>
        </div>
      </div>
    )
  }

  // ----------------------------------------------------------
  // 渲染：权限被拒绝
  // ----------------------------------------------------------

  if (status === 'denied') {
    return (
      <div className="card p-4">
        <div className="flex items-start gap-3">
          <div className="shrink-0 mt-0.5">
            <svg
              className="w-5 h-5 text-amber-500"
              fill="none"
              stroke="currentColor"
              strokeWidth={2}
              viewBox="0 0 24 24"
            >
              <path
                strokeLinecap="round"
                strokeLinejoin="round"
                d="M12 9v2m0 4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"
              />
            </svg>
          </div>
          <div className="flex-1 min-w-0">
            <p className="text-sm font-medium text-gray-700">
              {t('components.push.permissionDenied')}
            </p>
            <p className="text-xs text-surface-400 mt-0.5">
              {t('components.push.permissionDeniedHint')}
            </p>
          </div>
        </div>
      </div>
    )
  }

  // ----------------------------------------------------------
  // 渲染：已订阅 / 未订阅
  // ----------------------------------------------------------

  return (
    <div className="card p-4">
      {/* 标题行 */}
      <div className="flex items-center justify-between">
        <div className="flex items-center gap-3">
          {/* 状态图标 */}
          {status === 'subscribed' ? (
            <div className="w-5 h-5 rounded-full bg-emerald-100 flex items-center justify-center">
              <svg
                className="w-3 h-3 text-emerald-600"
                fill="none"
                stroke="currentColor"
                strokeWidth={3}
                viewBox="0 0 24 24"
              >
                <path
                  strokeLinecap="round"
                  strokeLinejoin="round"
                  d="M5 13l4 4L19 7"
                />
              </svg>
            </div>
          ) : (
            <div className="w-5 h-5 rounded-full bg-surface-100 flex items-center justify-center">
              <svg
                className="w-3 h-3 text-surface-400"
                fill="none"
                stroke="currentColor"
                strokeWidth={2}
                viewBox="0 0 24 24"
              >
                <path
                  strokeLinecap="round"
                  strokeLinejoin="round"
                  d="M15.536 8.464a5 5 0 010 7.072m2.828-9.9a9 9 0 010 12.728M5.586 15H4a1 1 0 01-1-1v-4a1 1 0 011-1h1.586l4.707-4.707C10.923 3.663 12 4.109 12 5v14c0 .891-1.077 1.337-1.707.707L5.586 15z"
                />
              </svg>
            </div>
          )}

          {/* 状态文字 */}
          <div>
            <p className="text-sm font-medium text-gray-700">
              {status === 'subscribed' ? t('components.push.enabled') : t('components.push.disabled')}
            </p>
            <p className="text-xs text-surface-400 mt-0.5">
              {status === 'subscribed'
                ? t('components.push.enabledDesc')
                : t('components.push.disabledDesc')}
            </p>
          </div>
        </div>

        {/* 切换按钮 */}
        {status === 'subscribed' ? (
          <button
            type="button"
            onClick={handleDisable}
            className="btn-danger text-xs px-3 py-1.5"
          >
            {t('components.push.disableButton')}
          </button>
        ) : (
          <button
            type="button"
            onClick={handleEnable}
            className="btn-primary text-xs px-3 py-1.5"
          >
            {t('components.push.enableButton')}
          </button>
        )}
      </div>

      {/* 错误提示 */}
      {error && (
        <div className="mt-3 px-3 py-2 bg-red-50 border border-red-200 rounded-lg">
          <p className="text-xs text-red-600">{error}</p>
        </div>
      )}
    </div>
  )
}