import 'package:flutter/widgets.dart';

/// Creates a primary scroll controller that will
/// scroll to the top when tapped on the status bar
///
class PrimaryScrollStatusBarHandler extends StatefulWidget {
  final Widget child;

  const PrimaryScrollStatusBarHandler({Key key, this.child}) : super(key: key);

  @override
  _PrimaryScrollWidgetState createState() => _PrimaryScrollWidgetState();
}

class _PrimaryScrollWidgetState extends State<PrimaryScrollStatusBarHandler> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      fit: StackFit.expand,
      children: [
        widget.child,
        Positioned(
          top: 0,
          left: 0,
          right: 0,
          height: MediaQuery.of(context).padding.top,
          child: Builder(
            builder: (context) => GestureDetector(
              behavior: HitTestBehavior.opaque,
              onTap: () => _handleStatusBarTap(context),
              // iOS accessibility automatically adds scroll-to-top to the clock in the status bar
              excludeFromSemantics: true,
            ),
          ),
        ),
      ],
    );
  }

  void _handleStatusBarTap(BuildContext context) {
    final controller = PrimaryScrollController.of(context);
    if (controller != null && controller.hasClients) {
      controller.animateTo(
        0.0,
        duration: const Duration(milliseconds: 300),
        curve: Curves.linear, // TODO(ianh): Use a more appropriate curve.
      );
    }
  }
}