// tools/function_plotter.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import '../curve_plot.dart';
import '../expr_syntax.dart';
import '../symja.dart';

/// 函数图像绘制：把一个或多个 y = f(x) 交给 Symja 采样，再用项目自己的
/// [CurvePlot] 画出来。
///
/// 为什么改成按钮触发的异步绘制：Symja 的求值都跑在原生侧的专用线程上，只能
/// 异步拿结果；旧的 `math_expressions` 是同步的，才能每次 build 都重算一遍。
/// 现在按下「绘制」采样一次，采样期间禁用按钮并显示忙碌状态。
class FunctionPlotterPage extends StatefulWidget {
  const FunctionPlotterPage({super.key});

  @override
  State<FunctionPlotterPage> createState() => _FunctionPlotterPageState();
}

class _FunctionPlotterPageState extends State<FunctionPlotterPage> {
  static const int _maxCurves = 5;

  /// 每条曲线的固定颜色，下标与输入框一一对应（沿用旧版配色）。
  static const List<Color> _curveColors = <Color>[
    Colors.blue,
    Colors.red,
    Colors.green,
    Colors.orange,
    Colors.purple,
  ];

  final List<TextEditingController> _exprs = <TextEditingController>[
    TextEditingController(text: 'x^2'),
  ];
  final TextEditingController _xMin = TextEditingController(text: '-5');
  final TextEditingController _xMax = TextEditingController(text: '5');
  final TextEditingController _yMin = TextEditingController(text: '-10');
  final TextEditingController _yMax = TextEditingController(text: '10');

  List<CurveSeries> _series = const <CurveSeries>[];

  /// 上一次绘制实际使用的 y 范围（没绘制过就是 null，交给 CurvePlot 自动定界）。
  double? _plotYMin;
  double? _plotYMax;

  /// 每个输入框的错误信息，与 [_exprs] 下标对齐；null 表示该项正常。
  List<String?> _errors = const <String?>[];

  /// 坐标范围本身的错误（与某条曲线无关），显示在绘图区。
  String? _rangeError;

  bool _busy = false;

  @override
  void initState() {
    super.initState();
    // 首帧后再绘制：context.read 需要 element 已经挂载到 Provider 之下。
    WidgetsBinding.instance.addPostFrameCallback((_) => _plot());
  }

  @override
  void dispose() {
    for (final c in _exprs) {
      c.dispose();
    }
    _xMin.dispose();
    _xMax.dispose();
    _yMin.dispose();
    _yMax.dispose();
    super.dispose();
  }

  void _addCurve() {
    if (_exprs.length >= _maxCurves) return;
    setState(() => _exprs.add(TextEditingController()));
  }

  void _removeCurve(int index) {
    if (_exprs.length <= 1) return;
    setState(() => _exprs.removeAt(index).dispose());
  }

  Future<void> _plot() async {
    if (_busy) return;

    final xMin = double.tryParse(_xMin.text.trim());
    final xMax = double.tryParse(_xMax.text.trim());
    final yMin = double.tryParse(_yMin.text.trim());
    final yMax = double.tryParse(_yMax.text.trim());

    if (xMin == null || xMax == null || yMin == null || yMax == null) {
      setState(() => _rangeError = '请输入有效的坐标范围');
      return;
    }
    if (xMin >= xMax || yMin >= yMax) {
      setState(() => _rangeError = '最小值必须小于最大值');
      return;
    }

    final session = context.read<SymjaSession>();
    setState(() {
      _busy = true;
      _rangeError = null;
      _plotYMin = yMin;
      _plotYMax = yMax;
      // 每次重绘都重建，长度与输入框对齐，旧错误自然被清掉。
      _errors = List<String?>.filled(_exprs.length, null);
    });

    final result = <CurveSeries>[];
    // 逐条采样：一条失败不影响其它条，错误只挂到它自己那一栏。
    for (var i = 0; i < _exprs.length; i++) {
      final raw = _exprs[i].text.trim();
      if (raw.isEmpty) continue;
      try {
        // 用户可能沿用旧的小写括号语法，先转成 Symja 语法再采样。
        final expr = toSymjaSyntax(raw);
        final s = await session.sample(
          expr,
          variable: 'x',
          from: xMin,
          to: xMax,
          count: 240,
        );
        if (!mounted) return;
        result.add(CurveSeries(
          label: raw,
          color: _curveColors[i],
          // 非有限值（极点处的 ComplexInfinity 等）原样保留，
          // CurvePlot 会把它们当成抬笔断点，这里不做过滤。
          points: <Offset>[
            for (var k = 0; k < s.ys.length; k++) Offset(s.xAt(k), s.ys[k]),
          ],
        ));
      } on SymjaException catch (e) {
        if (!mounted) return;
        _errors[i] = '$e';
      }
    }

    if (!mounted) return;
    setState(() {
      _series = result;
      _busy = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('函数图像绘制', style: TextStyle(color: Colors.black)),
        backgroundColor: Colors.white,
        elevation: 1,
        actions: [
          IconButton(
            icon: const Icon(Icons.refresh),
            onPressed: _busy ? null : _plot,
            tooltip: '重新绘制',
          ),
        ],
      ),
      body: SingleChildScrollView(
        child: Padding(
          padding: const EdgeInsets.all(16),
          child: Column(
            children: [
              _buildInputs(),
              const SizedBox(height: 16),
              SizedBox(
                height: MediaQuery.of(context).size.height * 0.5,
                child: _buildPlotArea(),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildInputs() {
    return Card(
      elevation: 4,
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const Text(
              '函数表达式 (使用 x 作为变量)',
              style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
            ),
            const SizedBox(height: 10),
            const Text(
              '支持: +, -, *, /, ^, sin, cos, tan, ln, sqrt, pi, e',
              style: TextStyle(fontSize: 12, color: Colors.grey),
            ),
            const SizedBox(height: 10),
            LayoutBuilder(
              builder: (context, constraints) {
                final fields = <Widget>[
                  _buildRangeField(_xMin, 'x最小值'),
                  _buildRangeField(_xMax, 'x最大值'),
                  _buildRangeField(_yMin, 'y最小值'),
                  _buildRangeField(_yMax, 'y最大值'),
                ];
                // 窄屏竖向排，宽屏横向排。
                if (constraints.maxWidth < 600) {
                  return Column(
                    children: [
                      for (var i = 0; i < fields.length; i++) ...[
                        if (i > 0) const SizedBox(height: 10),
                        fields[i],
                      ],
                    ],
                  );
                }
                return Row(
                  children: [
                    for (var i = 0; i < fields.length; i++) ...[
                      if (i > 0) const SizedBox(width: 10),
                      Expanded(child: fields[i]),
                    ],
                  ],
                );
              },
            ),
            const SizedBox(height: 4),
            const Text(
              '注: x 范围决定采样区间，y 范围决定显示窗口；图上还能双指缩放、拖动、双击复位。',
              style: TextStyle(fontSize: 11, color: Colors.grey),
            ),
            const SizedBox(height: 10),
            Container(
              constraints: const BoxConstraints(maxHeight: 240),
              child: ListView.builder(
                shrinkWrap: true,
                itemCount: _exprs.length,
                itemBuilder: _buildExprRow,
              ),
            ),
            const SizedBox(height: 10),
            Row(
              children: [
                if (_exprs.length < _maxCurves)
                  OutlinedButton.icon(
                    onPressed: _busy ? null : _addCurve,
                    icon: const Icon(Icons.add),
                    label: const Text('添加函数'),
                  ),
                const Spacer(),
                ElevatedButton.icon(
                  onPressed: _busy ? null : _plot,
                  icon: _busy
                      ? const SizedBox(
                          width: 16,
                          height: 16,
                          child: CircularProgressIndicator(strokeWidth: 2),
                        )
                      : const Icon(Icons.show_chart),
                  label: Text(_busy ? '绘制中…' : '绘制图像'),
                  style: ElevatedButton.styleFrom(
                    backgroundColor: Colors.blue,
                    foregroundColor: Colors.white,
                  ),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildExprRow(BuildContext context, int index) {
    final raw = _exprs[index].text.trim();
    // 只有在语法真的被改写时才提示，避免对已经正确的输入刷屏。
    final rewrite = raw.isEmpty ? null : symjaRewriteOf(raw);
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 5),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Container(
            width: 20,
            height: 20,
            margin: const EdgeInsets.only(top: 16),
            decoration: BoxDecoration(
              color: _curveColors[index],
              shape: BoxShape.circle,
            ),
          ),
          const SizedBox(width: 10),
          Expanded(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                TextField(
                  controller: _exprs[index],
                  // 输入时重建，让下面的语法转换提示实时更新。
                  onChanged: (_) => setState(() {}),
                  decoration: InputDecoration(
                    hintText: '例如: x^2, sin(x), Sin[x]',
                    border: const OutlineInputBorder(),
                    errorText: index < _errors.length ? _errors[index] : null,
                  ),
                ),
                if (rewrite != null)
                  Padding(
                    padding: const EdgeInsets.only(top: 4, left: 4),
                    child: Text(
                      '已按 Symja 语法解释为: $rewrite',
                      style: TextStyle(fontSize: 11, color: Colors.grey[600]),
                    ),
                  ),
              ],
            ),
          ),
          const SizedBox(width: 10),
          if (_exprs.length > 1)
            IconButton(
              icon: const Icon(Icons.remove, color: Colors.red),
              tooltip: '删除该函数',
              onPressed: () => _removeCurve(index),
            ),
        ],
      ),
    );
  }

  Widget _buildRangeField(TextEditingController controller, String label) {
    return TextField(
      controller: controller,
      decoration: InputDecoration(
        labelText: label,
        border: const OutlineInputBorder(),
        contentPadding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
      ),
      keyboardType: TextInputType.numberWithOptions(
        signed: true,
        decimal: true,
      ),
    );
  }

  Widget _buildPlotArea() {
    return Card(
      elevation: 4,
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          children: [
            const Text(
              '函数图像',
              style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
            ),
            const SizedBox(height: 10),
            Expanded(child: _buildPlot()),
          ],
        ),
      ),
    );
  }

  Widget _buildPlot() {
    if (_busy) {
      return const Center(child: CircularProgressIndicator());
    }
    if (_rangeError != null) {
      return Center(
        child: Text(_rangeError!, style: const TextStyle(color: Colors.red)),
      );
    }
    if (_series.isEmpty) {
      return Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: const [
            Icon(Icons.functions, size: 50, color: Colors.grey),
            SizedBox(height: 10),
            Text('暂无函数图像可显示', style: TextStyle(color: Colors.grey)),
            Text(
              '请输入函数表达式后点击「绘制图像」',
              style: TextStyle(color: Colors.grey, fontSize: 12),
            ),
          ],
        ),
      );
    }
    return CurvePlot(series: _series, yMin: _plotYMin, yMax: _plotYMax);
  }
}