import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:nfc_manager/nfc_manager.dart';
import 'package:nfc_manager/ndef_record.dart';
import 'package:nfc_manager/nfc_manager_android.dart';
import 'package:nfc_manager/nfc_manager_ios.dart';
import 'package:nfc_manager_ndef/nfc_manager_ndef.dart';

class NfcTestPage extends StatefulWidget {
  const NfcTestPage({Key? key}) : super(key: key);

  @override
  _NfcTestPageState createState() => _NfcTestPageState();
}

class _NfcTestPageState extends State<NfcTestPage> {
  String _nfcData = '未扫描到标签。';
  bool _scanning = false;

  void _safeSetState(String data) {
    if (!mounted) return;
    setState(() => _nfcData = data);
  }

  Future<void> _startNfcSession() async {
    setState(() {
      _scanning = true;
      _nfcData = '扫描中...';
    });

    final available = await NfcManager.instance.isAvailable();
    if (!available) {
      _safeSetState('此设备不支持 NFC');
      setState(() => _scanning = false);
      return;
    }

    NfcManager.instance.startSession(
      onDiscovered: (NfcTag tag) async {
        String text = '未知';

        try {
          final ndef = Ndef.from(tag);
          if (ndef == null) {
            _safeSetState('标签不支持 NDEF');
          } else {
            final msg = ndef.cachedMessage;
            if (msg == null || msg.records.isEmpty) {
              _safeSetState('未找到任何 NDEF 记录');
            } else {
              // 第一条记录
              final record = msg.records.first;
              text = _parseTextRecord(record);
              _safeSetState('读取到文本: "$text"');

            }
          }
          String uid = '未知';
          try {
            if (Platform.isAndroid) {
              final nfcA = NfcAAndroid.from(tag);
              if (nfcA != null) {
                // 正确地通过 nfcA.tag.identifier 拿到 List<int>
                final bytes = nfcA.tag.id;
                uid = bytes
                    .map((b) => b.toRadixString(16).padLeft(2, '0'))
                    .join(':')
                    .toUpperCase();
              }
            } else if (Platform.isIOS) {
              // iOS 平台，用 MiFareIos（对于大多数 ISO14443-A，也可以用 Iso7816Ios）
              final mifare = MiFareIos.from(tag);
              final bytes = mifare!.identifier;
              uid = bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join(':').toUpperCase();
            }
          } catch (e) {
            debugPrint('取 UID 错误: $e');
          } finally {
            setState(() => _nfcData = '标签 UID: $uid' + '\n读取到文本: "$text"');
            await NfcManager.instance.stopSession();
          }
        } catch (e) {
          _safeSetState('解析时出错: $e');
        } finally {
          await NfcManager.instance.stopSession();
          if (mounted) setState(() => _scanning = false);
        }
      },
      pollingOptions: {NfcPollingOption.iso14443},
    );
  }

  /// 解析一个 NDEF Text 记录的 payload，返回纯文本内容
  String _parseTextRecord(NdefRecord record) {
    final payload = record.payload;
    if (payload.isEmpty) return '';

    final statusByte = payload[0];
    final langCodeLen = statusByte & 0x3F;
    // 文本数据开始的位置
    final textBytes = payload.sublist(1 + langCodeLen);

    try {
      return utf8.decode(textBytes);  // 默认 UTF‑8
    } catch (e) {
      // 解码失败时，退回到直接展示 bytes
      return String.fromCharCodes(textBytes);
    }
  }

  @override
  void dispose() {
    NfcManager.instance.stopSession();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('NFC 测试')),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            ElevatedButton(
              onPressed: _scanning ? null : _startNfcSession,
              child: Text(_scanning ? '扫描中...' : '开始扫描 NFC'),
            ),
            const SizedBox(height: 24),
            Expanded(
              child: SingleChildScrollView(
                child: Text(_nfcData, style: const TextStyle(fontSize: 16)),
              ),
            ),
          ],
        ),
      ),
    );
  }
}