observer/flutter_app/lib/camera/detection_overlay.dart

import 'dart:math' as math;

import 'package:flutter/material.dart';

import '../detection/coordinate_mapper.dart';
import '../detection/detection_result.dart';

/// 检测框绘制分级：
/// - 目标物种 confirmed：红色实线 3px（强证据）
/// - 目标物种 candidate：红色虚线 2px 半透明（待确认，弱提示）
/// - 疑似（生境预警）：黄色虚线 2px 半透明（常驻静态预警，弱化渲染）
/// 标签附带距离估计（针孔模型 焦距px×参考体型/框高px）。
/// 名称文本只取模型输出的 label（数据集训练决定，App 不内置物种名）。
class DetectionOverlay extends StatelessWidget {
  final List<DetectionResult> results;
  final int rotation;
  final int imageWidthPx;
  final int imageHeightPx;

  const DetectionOverlay({
    super.key,
    required this.results,
    required this.rotation,
    required this.imageWidthPx,
    required this.imageHeightPx,
  });

  @override
  Widget build(BuildContext context) {
    return IgnorePointer(
      child: CustomPaint(
        painter: _OverlayPainter(results, rotation, imageWidthPx, imageHeightPx),
        child: const SizedBox.expand(),
      ),
    );
  }
}

class _OverlayPainter extends CustomPainter {
  final List<DetectionResult> results;
  final int rotation;
  final int imageWidthPx;
  final int imageHeightPx;

  _OverlayPainter(this.results, this.rotation, this.imageWidthPx,
      this.imageHeightPx);

  // 仅保留通用「疑似」中文翻译；物种名由模型 labels 直接展示
  // （识别什么物种由训练好的模型决定，App 不内置物种名）
  static const _labels = {'suspect': '疑似'};

  /// 参考体型（米）：目标物种（class 0）身高 / suspect 植被高度
  static const double _refSizeSpeciesM = 0.45;
  static const double _refSizeSuspectM = 0.50;

  /// iPhone 13 主摄在 1280 高预览下的估算焦距 px（5.1mm / 5.30mm 传感器），
  /// 单目误差 ±30%，仅作参考
  static const double focalPx = 1230;
  static const double maxDistanceM = 120;

  @override
  void paint(Canvas canvas, Size size) {
    for (final r in results) {
      final rect = CoordinateMapper.mapToView(
        r.left,
        r.top,
        r.right,
        r.bottom,
        rotation,
        imageWidthPx,
        imageHeightPx,
        size.width,
        size.height,
      );
      // 颜色按类别索引而非 label 文本：模型类别名随数据集变化（物种中文名等），
      // class 0 恒为目标物种（红），其余类恒为 suspect（黄）
      final isSuspect = r.classId > 0 || r.label == 'suspect';
      final color = isSuspect ? Color(0xFFFDD835) : Color(0xFFE53935);
      final confirmed = r.confirmed && !isSuspect;
      final paint = Paint()
        ..color = color.withValues(alpha: confirmed ? 1.0 : 0.55)
        ..style = PaintingStyle.stroke
        ..strokeWidth = confirmed ? 3 : 2
        ..isAntiAlias = true;
      final box = Rect.fromLTRB(rect.left, rect.top, rect.right, rect.bottom);
      if (confirmed) {
        canvas.drawRect(box, paint);
      } else {
        _drawDashedRect(canvas, box, paint);
      }

      // 标签：框上方，含距离；多模型时标注来源模型名
      final dist = _distanceLabel(r);
      final modelTag = r.modelName.isNotEmpty
          ? '[${r.modelName}]'
          : '';
      final text =
          '${_labels[r.label] ?? r.label}$modelTag ${(r.score * 100).toInt()}%$dist';
      final textPainter = TextPainter(
        text: TextSpan(
          text: text,
          style: TextStyle(
            color: color.withValues(alpha: confirmed ? 1.0 : 0.8),
            fontSize: 14,
            fontWeight: FontWeight.w600,
            shadows: const [Shadow(color: Colors.black, blurRadius: 3)],
          ),
        ),
        textDirection: TextDirection.ltr,
      )..layout();
      final top = math.max(0.0, rect.top - 22);
      final left = math.max(0.0, rect.left);
      textPainter.paint(canvas, Offset(left + 4, top));
    }
  }

  String _distanceLabel(DetectionResult r) {
    final refH = (r.classId > 0 || r.label == 'suspect')
        ? _refSizeSuspectM
        : _refSizeSpeciesM;
    final hPx = r.height * imageHeightPx;
    if (hPx < 8) return '';
    final m = focalPx * refH / hPx;
    if (m > maxDistanceM) return '';
    return ' ≈${m.round()}m';
  }

  void _drawDashedRect(Canvas canvas, Rect r, Paint paint,
      {double dash = 10, double gap = 6}) {
    void dashLine(Offset a, Offset b) {
      final total = (b - a).distance;
      if (total <= 0) return;
      final dir = (b - a) / total;
      var d = 0.0;
      while (d < total) {
        final e = math.min(d + dash, total);
        canvas.drawLine(a + dir * d, a + dir * e, paint);
        d += dash + gap;
      }
    }

    dashLine(r.topLeft, r.topRight);
    dashLine(r.topRight, r.bottomRight);
    dashLine(r.bottomRight, r.bottomLeft);
    dashLine(r.bottomLeft, r.topLeft);
  }

  @override
  bool shouldRepaint(_OverlayPainter oldDelegate) =>
      oldDelegate.results != results ||
      oldDelegate.rotation != rotation ||
      oldDelegate.imageWidthPx != imageWidthPx ||
      oldDelegate.imageHeightPx != imageHeightPx;
}