import 'package:flutter/material.dart';

void showAppointmentBottomSheet(
  BuildContext context, {
  required Widget Function(BuildContext context) header,
  required SliverChildListDelegate Function(BuildContext context) body,
}) {
  showModalBottomSheet<void>(
    context: context,
    isScrollControlled: true,
    useSafeArea: true,
    backgroundColor: Theme.of(context).colorScheme.surface,
    builder: (sheetContext) => DraggableScrollableSheet(
      expand: false,
      initialChildSize: 0.4,
      minChildSize: 0.2,
      maxChildSize: 0.7,
      snap: true,
      snapSizes: const [0.4],
      builder: (_, scrollController) => CustomScrollView(
        controller: scrollController,
        slivers: [
          SliverPersistentHeader(
            pinned: true,
            delegate: _StickyHeader(child: header(sheetContext)),
          ),
          SliverList(delegate: body(sheetContext)),
        ],
      ),
    ),
  );
}

class _StickyHeader extends SliverPersistentHeaderDelegate {
  _StickyHeader({required this.child});
  final Widget child;

  @override
  double get minExtent => 100;
  @override
  double get maxExtent => 100;

  @override
  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) => Material(
        color: Theme.of(context).colorScheme.surface,
        child: SizedBox.expand(child: child),
      );

  @override
  bool shouldRebuild(covariant _StickyHeader oldDelegate) => oldDelegate.child != child;
}