tiku/tiku-client/lib/pages/export/export_page.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:path_provider/path_provider.dart';
import '../../services/api_service.dart';
import '../../providers/app_provider.dart';

const _channel = MethodChannel('com.tiku/file_picker');

class ExportPage extends ConsumerStatefulWidget {
  final int? cartId;
  final String? cartName;

  const ExportPage({super.key, this.cartId, this.cartName});

  @override
  ConsumerState<ExportPage> createState() => _ExportPageState();
}

class _ExportPageState extends ConsumerState<ExportPage> {
  bool _exporting = false;
  Map<String, dynamic>? _result;

  Future<void> _doExport() async {
    setState(() => _exporting = true);
    final api = ref.read(apiServiceProvider);
    try {
      Map<String, dynamic> data;
      if (widget.cartId != null) {
        data = await api.exportCart(widget.cartId!, widget.cartName ?? '试题篮导出');
      } else {
        data = await api.exportChapter(null, null, '全部导出');
      }
      setState(() { _result = data; _exporting = false; });
    } catch (e) {
      setState(() => _exporting = false);
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('导出失败: $e')),
        );
      }
    }
  }

  Future<void> _downloadFile(String filename, String label) async {
    final api = ref.read(apiServiceProvider);
    try {
      // Step 1: download to cache
      final dir = await getApplicationDocumentsDirectory();
      final tmpPath = '${dir.path}/$filename';
      await api.downloadExport(filename, tmpPath);

      // Step 2: let user choose save location
      final saved = await _channel.invokeMethod<bool>('saveFile', {
        'filePath': tmpPath,
        'fileName': filename,
      });

      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text(saved == true ? '$label 已保存' : '已取消'),
            duration: const Duration(seconds: 2),
          ),
        );
      }
    } catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('下载失败: $e')),
        );
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.cartName != null ? '导出: ${widget.cartName}' : '导出')),
      body: Center(
        child: Padding(
          padding: const EdgeInsets.all(32),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              if (_result == null) ...[
                const Icon(Icons.picture_as_pdf, size: 80, color: Colors.blue),
                const SizedBox(height: 24),
                const Text('将生成学生版和教师版两份 docx 文件'),
                const SizedBox(height: 24),
                SizedBox(
                  width: 200, height: 48,
                  child: FilledButton.icon(
                    onPressed: _exporting ? null : _doExport,
                    icon: _exporting
                        ? const SizedBox(width: 20, height: 20, child: CircularProgressIndicator(strokeWidth: 2))
                        : const Icon(Icons.file_download),
                    label: Text(_exporting ? '生成中...' : '导出 docx'),
                  ),
                ),
              ] else ...[
                const Icon(Icons.check_circle, size: 80, color: Colors.green),
                const SizedBox(height: 24),
                Text('导出成功！共 ${_result!['count']} 题'),
                const SizedBox(height: 16),
                FilledButton.tonal(
                  onPressed: () => _downloadFile(_result!['student'] as String, '学生版.docx'),
                  child: const Row(mainAxisSize: MainAxisSize.min, children: [
                    Icon(Icons.download, size: 18), SizedBox(width: 8), Text('学生版'),
                  ]),
                ),
                const SizedBox(height: 8),
                FilledButton.tonal(
                  onPressed: () => _downloadFile(_result!['teacher'] as String, '教师版.docx'),
                  child: const Row(mainAxisSize: MainAxisSize.min, children: [
                    Icon(Icons.download, size: 18), SizedBox(width: 8), Text('教师版'),
                  ]),
                ),
                const SizedBox(height: 16),
                TextButton(
                  onPressed: () => Navigator.pop(context),
                  child: const Text('返回'),
                ),
              ],
            ],
          ),
        ),
      ),
    );
  }
}