import { useState, useEffect, useRef } from 'react';
import { useRouter } from 'next/router';
import { isLoggedIn, exportData, importData, logout as apiLogout } from '../lib/api';
import AppShell from '../components/AppShell';
import { Icon } from '../components/icons';
import { useToast } from '../components/ToastProvider';
import { useConfirm } from '../components/ConfirmProvider';

export default function Settings() {
  const router = useRouter();
  const fileInputRef = useRef(null);
  const { showToast } = useToast();
  const { confirm } = useConfirm();
  const [exporting, setExporting] = useState(false);
  const [importing, setImporting] = useState(false);
  const [loggingOut, setLoggingOut] = useState(false);

  useEffect(() => {
    if (!isLoggedIn()) {
      router.push('/login');
    }
  }, [router]);

  const handleLogout = async () => {
    const shouldLogout = await confirm({
      title: '退出当前账号？',
      description: '退出后需要重新登录才能继续使用。',
      confirmText: '退出登录',
      tone: 'info',
    });
    if (!shouldLogout) return;

    setLoggingOut(true);
    apiLogout();
    showToast('已退出登录', { tone: 'success' });
    router.push('/login');
  };

  const handleExport = async () => {
    setExporting(true);
    try {
      const data = await exportData();
      const blob = new Blob([JSON.stringify(data, null, 2)], { type: 'application/json' });
      const url = URL.createObjectURL(blob);
      const link = document.createElement('a');
      link.href = url;
      link.download = `accountbook_backup_${new Date().toISOString().split('T')[0]}.json`;
      link.click();
      URL.revokeObjectURL(url);
      showToast('导出成功', { tone: 'success' });
    } catch (err) {
      showToast(`导出失败: ${err.message}`, { tone: 'error' });
    } finally {
      setExporting(false);
    }
  };

  const handleImport = async (e) => {
    const file = e.target.files?.[0];
    if (!file) return;

    setImporting(true);
    try {
      const text = await file.text();
      const data = JSON.parse(text);
      await importData(data);
      showToast('导入成功', { tone: 'success' });
      e.target.value = '';
    } catch (err) {
      showToast(`导入失败: ${err.message}`, { tone: 'error' });
    } finally {
      setImporting(false);
    }
  };

  return (
    <AppShell title="设置" subtitle="数据、账号与应用信息" compactHeader>
      <section className="card settings-section settings-section--refresh">
        <div className="section-heading section-heading--compact">
          <div>
            <p className="eyebrow">数据管理</p>
            <h2>导入与导出</h2>
          </div>
        </div>
        <div className="settings-item">
          <div className="settings-info">
            <div className="settings-title">导出数据</div>
            <div className="settings-desc">将所有账目导出为 JSON 文件，方便备份。</div>
          </div>
          <button type="button" className="btn btn-primary btn-inline" onClick={handleExport} disabled={exporting || importing}>
            <span className="button-content">
              <Icon name="download" size={16} />
              {exporting ? '导出中...' : '导出'}
            </span>
          </button>
        </div>
        <div className="settings-item">
          <div className="settings-info">
            <div className="settings-title">导入数据</div>
            <div className="settings-desc">从 JSON 文件恢复账目数据。</div>
          </div>
          <button type="button" className="btn btn-secondary btn-inline" onClick={() => fileInputRef.current?.click()} disabled={exporting || importing}>
            <span className="button-content">
              <Icon name="upload" size={16} />
              {importing ? '导入中...' : '导入'}
            </span>
          </button>
          <input
            type="file"
            ref={fileInputRef}
            onChange={handleImport}
            accept=".json"
            style={{ display: 'none' }}
          />
        </div>
      </section>

      <section className="card settings-section settings-section--refresh">
        <div className="section-heading section-heading--compact">
          <div>
            <p className="eyebrow">账号</p>
            <h2>登录状态</h2>
          </div>
        </div>
        <div className="settings-item settings-item--stacked">
          <div className="settings-info">
            <div className="settings-title">退出登录</div>
            <div className="settings-desc">从当前设备安全退出，并返回登录页。</div>
          </div>
          <button type="button" className="btn btn-danger btn-inline" onClick={handleLogout} disabled={loggingOut}>
            <span className="button-content">
              <Icon name="logout" size={16} />
              {loggingOut ? '退出中...' : '退出登录'}
            </span>
          </button>
        </div>
      </section>

      <section className="card settings-section settings-section--refresh">
        <div className="section-heading section-heading--compact">
          <div>
            <p className="eyebrow">关于</p>
            <h2>应用信息</h2>
          </div>
        </div>
        <div className="about-info">
          <p>简易记账本 v1.0</p>
          <p className="sub">基于 React + Next.js 开发</p>
        </div>
      </section>
    </AppShell>
  );
}