import React, { useState } from 'react';
import Snackbar from '@mui/material/Snackbar';
import Alert from '@mui/material/Alert';

// 模块级单例：admin 任意处调用 showSnack，由 AdminLayout 内的 SnackHost 消费
let showFn = null;

export function showSnack(msg, severity = 'success') {
  if (showFn) showFn(msg, severity);
  else window.alert(msg);
}

export default function SnackHost() {
  const [open, setOpen] = useState(false);
  const [msg, setMsg] = useState('');
  const [severity, setSeverity] = useState('success');

  showFn = (m, s) => { setMsg(m); setSeverity(s || 'success'); setOpen(true); };

  return (
    <Snackbar
      open={open}
      autoHideDuration={2500}
      onClose={() => setOpen(false)}
      anchorOrigin={{ vertical: 'bottom', horizontal: 'center' }}
    >
      <Alert severity={severity} variant="filled" onClose={() => setOpen(false)}>{msg}</Alert>
    </Snackbar>
  );
}