mathtool/lib/tools/parametric_plotter.dart

// tools/parametric_plotter.dart
import 'package:flutter/material.dart';
import 'package:math_expressions/math_expressions.dart';
import 'package:fl_chart/fl_chart.dart';

class ParametricPlotterPage extends StatefulWidget {
  @override
  _ParametricPlotterPageState createState() => _ParametricPlotterPageState();
}

class _ParametricPlotterPageState extends State<ParametricPlotterPage> {
  final TextEditingController xController = TextEditingController(text: 'cos(t)');
  final TextEditingController yController = TextEditingController(text: 'sin(t)');
  final TextEditingController tMinController = TextEditingController(text: '0');
  final TextEditingController tMaxController = TextEditingController(text: '6.3');
  final TextEditingController stepController = TextEditingController(text: '0.1');

  List<FlSpot> points = [];
  String errorMessage = '';
  bool isLoading = false;

  double minX = 0;
  double maxX = 0;
  double minY = 0;
  double maxY = 0;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _plotGraph();
    });
  }

  void _plotGraph() {
    setState(() {
      isLoading = true;
      errorMessage = '';
    });

    try {
      final tMin = double.parse(tMinController.text);
      final tMax = double.parse(tMaxController.text);
      final step = double.parse(stepController.text);

      if (tMin >= tMax) {
        throw Exception('t最小值必须小于t最大值');
      }
      if (step <= 0) {
        throw Exception('步长必须大于0');
      }

      final xExpr = _parseExpression(xController.text);
      final yExpr = _parseExpression(yController.text);

      List<FlSpot> newPoints = [];
      double currentMinX = double.infinity;
      double currentMaxX = -double.infinity;
      double currentMinY = double.infinity;
      double currentMaxY = -double.infinity;

      for (double t = tMin; t <= tMax; t += step) {
        try {
          final x = _evaluateExpression(xExpr, t);
          final y = _evaluateExpression(yExpr, t);

          if (x.isFinite && y.isFinite) {
            newPoints.add(FlSpot(x, y));
            currentMinX = x < currentMinX ? x : currentMinX;
            currentMaxX = x > currentMaxX ? x : currentMaxX;
            currentMinY = y < currentMinY ? y : currentMinY;
            currentMaxY = y > currentMaxY ? y : currentMaxY;
          }
        } catch (e) {
          // 跳过无效点
        }
      }

      if (newPoints.isEmpty) {
        throw Exception('未生成有效数据点，请检查参数方程');
      }

      setState(() {
        points = newPoints;
        minX = currentMinX;
        maxX = currentMaxX;
        minY = currentMinY;
        maxY = currentMaxY;
      });
    } catch (e) {
      setState(() {
        errorMessage = e.toString();
        points = [];
      });
    } finally {
      setState(() {
        isLoading = false;
      });
    }
  }

  Expression _parseExpression(String expression) {
  // 清理表达式中的空格
  String cleaned = expression.replaceAll(' ', '');
  
  // 将常见函数名转换为math_expressions识别的格式
  cleaned = cleaned.replaceAllMapped(RegExp(r'(\d)([a-zA-Z])'), (match) {
    return '${match.group(1)}*${match.group(2)}';
  });
  
  // 移除这行，因为math_expressions使用^作为幂运算符
  // cleaned = cleaned.replaceAll('^', '**');
  
  try {
    Parser p = Parser();
    return p.parse(cleaned);
  } catch (e) {
    throw Exception('表达式解析错误: $e');
  }
}

  double _evaluateExpression(Expression expr, double t) {
    ContextModel cm = ContextModel()
      ..bindVariable(Variable('t'), Number(t))
      ..bindVariable(Variable('pi'), Number(3.141592653589793))
      ..bindVariable(Variable('e'), Number(2.718281828459045));

    try {
      return expr.evaluate(EvaluationType.REAL, cm);
    } catch (e) {
      throw Exception('在 t=$t 时计算错误: $e');
    }
  }

  Widget _buildInputPanel() {
    return Card(
      elevation: 4,
      margin: EdgeInsets.all(16),
      child: Padding(
        padding: EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              '参数方程设置',
              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 16),
            TextField(
              controller: xController,
              decoration: InputDecoration(
                labelText: 'x = f(t)',
                hintText: '例如: cos(t), t^2, 2*t+1',
                border: OutlineInputBorder(),
              ),
            ),
            SizedBox(height: 12),
            TextField(
              controller: yController,
              decoration: InputDecoration(
                labelText: 'y = g(t)',
                hintText: '例如: sin(t), t^3, 3*t-2',
                border: OutlineInputBorder(),
              ),
            ),
            SizedBox(height: 16),
            Row(
              children: [
                Expanded(
                  child: TextField(
                    controller: tMinController,
                    decoration: InputDecoration(
                      labelText: 't最小值',
                      border: OutlineInputBorder(),
                    ),
                    keyboardType: TextInputType.numberWithOptions(decimal: true),
                  ),
                ),
                SizedBox(width: 12),
                Expanded(
                  child: TextField(
                    controller: tMaxController,
                    decoration: InputDecoration(
                      labelText: 't最大值',
                      border: OutlineInputBorder(),
                    ),
                    keyboardType: TextInputType.numberWithOptions(decimal: true),
                  ),
                ),
                SizedBox(width: 12),
                Expanded(
                  child: TextField(
                    controller: stepController,
                    decoration: InputDecoration(
                      labelText: '步长',
                      border: OutlineInputBorder(),
                    ),
                    keyboardType: TextInputType.numberWithOptions(decimal: true),
                  ),
                ),
              ],
            ),
            SizedBox(height: 16),
            if (errorMessage.isNotEmpty)
              Container(
                width: double.infinity,
                padding: EdgeInsets.all(12),
                decoration: BoxDecoration(
                  color: Colors.red[50],
                  borderRadius: BorderRadius.circular(8),
                  border: Border.all(color: Colors.red),
                ),
                child: Text(
                  errorMessage,
                  style: TextStyle(color: Colors.red),
                ),
              ),
            SizedBox(height: 16),
            ElevatedButton.icon(
              onPressed: _plotGraph,
              icon: Icon(Icons.show_chart),
              label: Text('绘制图像'),
              style: ElevatedButton.styleFrom(
                minimumSize: Size(double.infinity, 50),
              ),
            ),
          ],
        ),
      ),
    );
  }

 Widget _buildGraph() {
  if (points.isEmpty) {
    return Container(
      height: 300,
      child: Center(
        child: Text(
          '暂无数据',
          style: TextStyle(fontSize: 16, color: Colors.grey),
        ),
      ),
    );
  }

  // 计算坐标轴范围，确保x和y轴有相同的缩放比例
  double rangeX = maxX - minX;
  double rangeY = maxY - minY;
  double maxRange = rangeX > rangeY ? rangeX : rangeY;
  
  double centerX = (minX + maxX) / 2;
  double centerY = (minY + maxY) / 2;
  
  double adjustedMinX = centerX - maxRange / 2;
  double adjustedMaxX = centerX + maxRange / 2;
  double adjustedMinY = centerY - maxRange / 2;
  double adjustedMaxY = centerY + maxRange / 2;

  // 添加一些边距
  double margin = maxRange * 0.1;
  adjustedMinX -= margin;
  adjustedMaxX += margin;
  adjustedMinY -= margin;
  adjustedMaxY += margin;

  return Card(
    elevation: 4,
    margin: EdgeInsets.all(16),
    child: Padding(
      padding: EdgeInsets.all(16),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            '参数方程图像',
            style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
          ),
          SizedBox(height: 16),
          // 修复：使用 AspectRatio 确保图表始终保持正方形
          AspectRatio(
            aspectRatio: 1, // 强制宽高比为1:1
            child: Container(
              decoration: BoxDecoration(
                border: Border.all(color: Colors.grey[300]!),
                borderRadius: BorderRadius.circular(8),
              ),
              child: LineChart(
                LineChartData(
                  gridData: FlGridData(show: true),
                  titlesData: FlTitlesData(
                    show: true,
                    bottomTitles: AxisTitles(
                      sideTitles: SideTitles(showTitles: true),
                    ),
                    leftTitles: AxisTitles(
                      sideTitles: SideTitles(showTitles: true),
                    ),
                    rightTitles: AxisTitles(
                      sideTitles: SideTitles(showTitles: false),
                    ),
                    topTitles: AxisTitles(
                      sideTitles: SideTitles(showTitles: false),
                    ),
                  ),
                  borderData: FlBorderData(show: true),
                  minX: adjustedMinX,
                  maxX: adjustedMaxX,
                  minY: adjustedMinY,
                  maxY: adjustedMaxY,
                  lineTouchData: LineTouchData(enabled: false),
                  lineBarsData: [
                    LineChartBarData(
                      spots: points,
                      isCurved: true,
                      color: Colors.blue,
                      barWidth: 3,
                      dotData: FlDotData(show: false),
                      belowBarData: BarAreaData(show: false),
                    ),
                  ],
                ),
              ),
            ),
          ),
          SizedBox(height: 16),
          Text(
            '方程: x = ${xController.text}, y = ${yController.text}',
            style: TextStyle(fontSize: 14, color: Colors.grey[600]),
          ),
          Text(
            '参数范围: t ∈ [${tMinController.text}, ${tMaxController.text}], 步长: ${stepController.text}',
            style: TextStyle(fontSize: 14, color: Colors.grey[600]),
          ),
        ],
      ),
    ),
  );
}
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('参数方程绘图', style: TextStyle(color: Colors.black)),
        backgroundColor: Colors.white,
        elevation: 1,
      ),
      body: isLoading
          ? Center(child: CircularProgressIndicator())
          : SingleChildScrollView(
              child: Column(
                children: [
                  _buildInputPanel(),
                  _buildGraph(),
                  _buildExamples(),
                ],
              ),
            ),
    );
  }

  Widget _buildExamples() {
    return Card(
      elevation: 4,
      margin: EdgeInsets.all(16),
      child: Padding(
        padding: EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              '示例方程',
              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 12),
            Wrap(
              spacing: 8,
              runSpacing: 8,
              children: [
                // 删除了圆的示例
                _buildExampleChip('椭圆', '2*cos(t)', 'sin(t)', '0', '6.3'),
                _buildExampleChip('螺旋线', 't*cos(t)', 't*sin(t)', '0', '12.6'),
                _buildExampleChip('抛物线', 't', 't^2', '-2', '2'),
                _buildExampleChip('心形线', '2*cos(t)-cos(2*t)', '2*sin(t)-sin(2*t)', '0', '6.3'),
              ],
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildExampleChip(String title, String xExpr, String yExpr, String tMin, String tMax) {
    return ActionChip(
      label: Text(title),
      onPressed: () {
        setState(() {
          xController.text = xExpr;
          yController.text = yExpr;
          tMinController.text = tMin;
          tMaxController.text = tMax;
          stepController.text = '0.1';
        });
        _plotGraph();
      },
      backgroundColor: Colors.blue[50],
    );
  }
}