class ViewRect {
  final double left;
  final double top;
  final double right;
  final double bottom;

  const ViewRect(this.left, this.top, this.right, this.bottom);

  double get width => right - left;
  double get height => bottom - top;
  double get centerX => (left + right) / 2;
  double get centerY => (top + bottom) / 2;
}

/// 模型归一化坐标 → 预览视图坐标（含传感器旋转与 FIT_COVER 全屏裁剪）。
class CoordinateMapper {
  static ViewRect mapToView(
    double normLeft,
    double normTop,
    double normRight,
    double normBottom,
    int rotation,
    int imageW,
    int imageH,
    double viewW,
    double viewH,
  ) {
    // 1) 旋转校正：图像方向 → 竖屏视图方向（归一化坐标）
    late final double x0, y0, x1, y1;
    switch (rotation) {
      case 90:
        x0 = 1 - normBottom;
        y0 = normLeft;
        x1 = 1 - normTop;
        y1 = normRight;
      case 180:
        x0 = 1 - normRight;
        y0 = 1 - normBottom;
        x1 = 1 - normLeft;
        y1 = 1 - normTop;
      case 270:
        x0 = normTop;
        y0 = 1 - normRight;
        x1 = normBottom;
        y1 = 1 - normLeft;
      default:
        x0 = normLeft;
        y0 = normTop;
        x1 = normRight;
        y1 = normBottom;
    }
    // 2) 旋转后图像在竖屏方向上的尺寸
    final portrait = rotation == 90 || rotation == 270;
    final portW = portrait ? imageH : imageW;
    final portH = portrait ? imageW : imageH;
    // 3) FIT_COVER 缩放与居中裁剪：放大到铺满视图，溢出部分裁掉
    final scale = viewW / portW < viewH / portH
        ? viewH / portH
        : viewW / portW;
    final offsetX = (viewW - portW * scale) / 2;
    final offsetY = (viewH - portH * scale) / 2;
    return ViewRect(
      x0 * portW * scale + offsetX,
      y0 * portH * scale + offsetY,
      x1 * portW * scale + offsetX,
      y1 * portH * scale + offsetY,
    );
  }
}