import 'package:doormile_cx/ui/tokens.dart';
import 'package:doormile_cx/ui/widgets/chrome.dart';
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

/// The top bar's one piece of behaviour.
///
/// It reads the [ScrollNotificationObserver] that [Scaffold] installs, which is
/// a framework detail rather than something this app owns — so it is worth a
/// test. If a Flutter upgrade moves that observer, the bar silently goes back
/// to being a flat slab and nothing else in the suite would notice.
void main() {
  Color? barColour(WidgetTester tester) {
    final box = tester.widget<AnimatedContainer>(
      find
          .descendant(
            of: find.byType(DmTopBar),
            matching: find.byType(AnimatedContainer),
          )
          .first,
    );
    return (box.decoration as BoxDecoration?)?.color;
  }

  testWidgets('the bar lifts off the canvas once content is under it',
      (tester) async {
    await tester.pumpWidget(
      MaterialApp(
        home: Scaffold(
          backgroundColor: DmColors.canvas,
          appBar: const DmTopBar(title: 'Probe'),
          body: ListView(
            children: [
              for (var i = 0; i < 40; i++) const SizedBox(height: 40),
            ],
          ),
        ),
      ),
    );
    await tester.pumpAndSettle();

    // At rest it is the page: no line, no edge, nothing to notice.
    expect(barColour(tester), DmColors.canvas);

    await tester.drag(find.byType(ListView), const Offset(0, -300));
    await tester.pumpAndSettle();
    expect(barColour(tester), DmColors.surface);

    // And back again, so the top of a page is never wearing a line for
    // content that has scrolled away.
    await tester.drag(find.byType(ListView), const Offset(0, 600));
    await tester.pumpAndSettle();
    expect(barColour(tester), DmColors.canvas);
  });
}