import 'detection_result.dart';

double iou(DetectionResult a, DetectionResult b) {
  final x0 = a.left > b.left ? a.left : b.left;
  final y0 = a.top > b.top ? a.top : b.top;
  final x1 = a.right < b.right ? a.right : b.right;
  final y1 = a.bottom < b.bottom ? a.bottom : b.bottom;
  if (x1 <= x0 || y1 <= y0) return 0;
  final inter = (x1 - x0) * (y1 - y0);
  final union = a.width * a.height + b.width * b.height - inter;
  return union <= 0 ? 0 : inter / union;
}

/// 交叠/较小框面积（minIoU）：同一目标的一大一小两框时比 IoU 更能命中
/// （IoU = 小/大 会漏判；YOLO 同目标常输出大小两框，与 server 标注端
/// localAi.overlapThreshold 同思路，2026-09-01 用户实测修订）。
double boxOverlap(DetectionResult a, DetectionResult b) {
  final x0 = a.left > b.left ? a.left : b.left;
  final y0 = a.top > b.top ? a.top : b.top;
  final x1 = a.right < b.right ? a.right : b.right;
  final y1 = a.bottom < b.bottom ? a.bottom : b.bottom;
  if (x1 <= x0 || y1 <= y0) return 0;
  final inter = (x1 - x0) * (y1 - y0);
  final minArea = a.width * a.height < b.width * b.height
      ? a.width * a.height
      : b.width * b.height;
  return minArea <= 0 ? 0 : inter / minArea;
}

List<DetectionResult> nms(List<DetectionResult> boxes, double iouThreshold) {
  final sorted = [...boxes]..sort((a, b) => b.score.compareTo(a.score));
  final kept = <DetectionResult>[];
  for (final b in sorted) {
    if (!kept.any((k) => boxOverlap(b, k) > iouThreshold)) kept.add(b);
  }
  return kept;
}