import 'package:flutter/material.dart';

/// 全屏/局部 loading 遮罩。
///
/// 用法：
/// ```dart
/// LoadingOverlay(
///   loading: _isLoading,
///   child: MyWidget(),
/// )
/// ```
class LoadingOverlay extends StatelessWidget {
  const LoadingOverlay({
    super.key,
    required this.child,
    this.loading = false,
    this.label,
  });

  final Widget child;
  final bool loading;
  final String? label;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        child,
        if (loading)
          Positioned.fill(
            child: ColoredBox(
              color: Colors.black26,
              child: Center(
                child: Card(
                  child: Padding(
                    padding: const EdgeInsets.symmetric(
                        horizontal: 32, vertical: 24),
                    child: Column(
                      mainAxisSize: MainAxisSize.min,
                      children: [
                        const CircularProgressIndicator(),
                        if (label != null) ...[
                          const SizedBox(height: 12),
                          Text(label!,
                              style: Theme.of(context).textTheme.bodySmall),
                        ],
                      ],
                    ),
                  ),
                ),
              ),
            ),
          ),
      ],
    );
  }
}