mathtool2/lib/tools/vector_normal.dart

// tools/vector_normal.dart
//
// 计算部分走 Symja（符号计算库），不再用自研的 rationalsqrt2.dart。
// 那个自研的 √n 代数只能表示"有理数 × 一层根号 + 若干项之和"，遇到
// 坐标里出现两层根号、分数套根号、或者三角函数就得放弃；交给 CAS 之后
// 输入什么就能精确算什么。
import 'package:flutter/material.dart';
import 'package:flutter_math_fork/flutter_math.dart';
import 'package:provider/provider.dart';

import '../symja.dart';

class VectorNormalPage extends StatefulWidget {
  @override
  _VectorNormalPageState createState() => _VectorNormalPageState();
}

class _VectorNormalPageState extends State<VectorNormalPage> {
  final List<TextEditingController> _controllers = List.generate(9, (_) => TextEditingController());
  String _result = '';
  String? _resultTex;
  String? _error;
  bool _isCalculating = false;

  @override
  void dispose() {
    for (var controller in _controllers) {
      controller.dispose();
    }
    super.dispose();
  }

  // 计算法向量：AB × AC，全部交给 Symja 做符号运算
  Future<void> _calculateNormal() async {
    final session = context.read<SymjaSession>();
    setState(() {
      _isCalculating = true;
      _result = '';
      _resultTex = null;
      _error = null;
    });

    // 每个坐标先过一遍语法转换，这样用户沿用旧的 `2√3` 写法也能用
    String coord(int point, int axis) {
      final raw = _controllers[point * 3 + axis].text.trim();
      // 原样交给 Symja
      return raw.isEmpty ? '0' : raw;
    }

    // 边向量：to - from
    String vec(int from, int to) => '{'
        '(${coord(to, 0)} - ${coord(from, 0)}), '
        '(${coord(to, 1)} - ${coord(from, 1)}), '
        '(${coord(to, 2)} - ${coord(from, 2)})}';

    final expr = 'Cross[${vec(0, 1)}, ${vec(0, 2)}]';

    try {
      final r = await session.compute(expr);
      if (!mounted) return;
      setState(() {
        _result = r.text;
        _resultTex = r.tex;
      });
    } on SymjaException catch (e) {
      if (!mounted) return;
      setState(() => _error = '$e');
    } finally {
      if (mounted) setState(() => _isCalculating = false);
    }
  }

  // 清除所有输入
  void _clearAll() {
    for (var controller in _controllers) {
      controller.clear();
    }
    setState(() {
      _result = '';
      _resultTex = null;
      _error = null;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('三点法向量计算'),
        backgroundColor: Colors.white,
        elevation: 1,
      ),
      body: SingleChildScrollView(
        padding: EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            _buildInputSection('点A', 0),
            SizedBox(height: 16),
            _buildInputSection('点B', 3),
            SizedBox(height: 16),
            _buildInputSection('点C', 6),
            SizedBox(height: 24),
            _buildControlButtons(),
            SizedBox(height: 24),
            _buildResultSection(),
            SizedBox(height: 24),
            _buildInstructions(),
          ],
        ),
      ),
    );
  }

  Widget _buildInputSection(String title, int startIndex) {
    return Card(
      elevation: 2,
      child: Padding(
        padding: EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              title,
              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 12),
            Row(
              children: [
                _buildCoordinateInput('x', _controllers[startIndex]),
                SizedBox(width: 12),
                _buildCoordinateInput('y', _controllers[startIndex + 1]),
                SizedBox(width: 12),
                _buildCoordinateInput('z', _controllers[startIndex + 2]),
              ],
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildCoordinateInput(String label, TextEditingController controller) {
    return Expanded(
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            label,
            style: TextStyle(fontSize: 14, color: Colors.grey[600]),
          ),
          SizedBox(height: 4),
          TextField(
            controller: controller,
            decoration: InputDecoration(
              hintText: '0',
              border: OutlineInputBorder(),
              contentPadding: EdgeInsets.symmetric(horizontal: 12, vertical: 8),
            ),
            keyboardType: TextInputType.number,
          ),
        ],
      ),
    );
  }

  Widget _buildControlButtons() {
    return Row(
      children: [
        Expanded(
          flex: 3,
          child: ElevatedButton(
            onPressed: _isCalculating ? null : _calculateNormal,
            style: ElevatedButton.styleFrom(
              backgroundColor: Colors.blue,
              padding: EdgeInsets.symmetric(vertical: 12),
            ),
            child: _isCalculating
            ? SizedBox(
              width: 20,
              height: 20,
              child: CircularProgressIndicator(
                strokeWidth: 2,
                valueColor: AlwaysStoppedAnimation(Colors.white),
              ),
            )
            : Text(
              '计算法向量',
              style: TextStyle(fontSize: 16, color: Colors.white),
            ),
          ),
        ),
        SizedBox(width: 12),
        Expanded(
          flex: 2,
          child: OutlinedButton(
            onPressed: _clearAll,
            style: OutlinedButton.styleFrom(
              padding: EdgeInsets.symmetric(vertical: 12),
            ),
            child: Text('清除', style: TextStyle(fontSize: 16)),
          ),
        ),
      ],
    );
  }

  Widget _buildResultSection() {
    if (_error != null) {
      return Card(
        color: Colors.red[50],
        elevation: 2,
        child: Padding(
          padding: EdgeInsets.all(16),
          child: Row(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Icon(Icons.error_outline, color: Colors.red[700], size: 20),
              SizedBox(width: 8),
              Expanded(
                child: SelectableText(
                  '计算错误：$_error',
                  style: TextStyle(color: Colors.red[700], fontSize: 14),
                ),
              ),
            ],
          ),
        ),
      );
    }
    if (_result.isEmpty) return SizedBox();

    return Card(
      color: Colors.grey[50],
      elevation: 2,
      child: Padding(
        padding: EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              '计算结果',
              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 12),
            // 法向量是精确的符号结果（可能带根号、分数），用 LaTeX 排出来
            // 比纯文本好读得多。
            if (_resultTex != null)
              Math.tex(
                _resultTex!,
                mathStyle: MathStyle.display,
                textStyle: TextStyle(fontSize: 20, color: Colors.blue[800]),
                onErrorFallback: (_) => Text(
                  _result,
                  style: TextStyle(fontSize: 16, color: Colors.blue[700]),
                ),
              )
            else
              Text(
                _result,
                style: TextStyle(fontSize: 16, color: Colors.blue[700]),
              ),
            SizedBox(height: 8),
            // 纯文本那份留着，方便复制到别处
            SelectableText(
              _result,
              style: TextStyle(fontSize: 12, color: Colors.grey[700]),
            ),
            SizedBox(height: 8),
            Text(
              '说明：法向量是通过向量AB和向量AC的叉积计算得到',
              style: TextStyle(fontSize: 12, color: Colors.grey[600]),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildInstructions() {
    return Card(
      color: Colors.grey[50],
      elevation: 2,
      child: Padding(
        padding: EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              '使用说明',
              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 12),
            Text(
              '坐标按 Symja 语法输入，例如：\n'
              '  2/3      分数\n'
              '  Sqrt[2]  根号（也可写 √2）\n'
              '  Sqrt[2]/2、1 + Sqrt[3]、Pi\n'
              '\n'
              '结果是精确值：带根号、分数会原样保留，不会转成小数。\n'
              '如果已知两向量坐标，将一个点设为原点即可。',
              style: TextStyle(fontSize: 14, color: Colors.grey[700]),
            ),
          ],
        ),
      ),
    );
  }
}