import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:marianum_mobile/widget/route_transition_gate.dart';

void main() {
  const gated = Key('gated-child');
  const placeholder = Key('gate-placeholder');

  Widget gatedPage() => Scaffold(
    body: RouteTransitionGate(
      placeholder: const SizedBox(key: placeholder),
      // Hit-testable like the real viewer, so pointer tracking sees it.
      builder: (_) => const ColoredBox(
        key: gated,
        color: Color(0x00000000),
        child: SizedBox.expand(),
      ),
    ),
  );

  Future<void> pumpApp(WidgetTester tester) async {
    await tester.pumpWidget(
      MaterialApp(home: Builder(builder: (_) => const Scaffold())),
    );
  }

  NavigatorState navigator(WidgetTester tester) =>
      tester.state<NavigatorState>(find.byType(Navigator));

  testWidgets('shows placeholder during push, child once settled', (
    tester,
  ) async {
    await pumpApp(tester);
    unawaited(
      navigator(
        tester,
      ).push(MaterialPageRoute<void>(builder: (_) => gatedPage())),
    );
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));

    expect(find.byKey(placeholder), findsOneWidget);
    expect(find.byKey(gated), findsNothing);

    await tester.pumpAndSettle();
    expect(find.byKey(gated), findsOneWidget);
    expect(find.byKey(placeholder), findsNothing);
  });

  testWidgets('swaps back to placeholder while the route pops', (tester) async {
    await pumpApp(tester);
    unawaited(
      navigator(
        tester,
      ).push(MaterialPageRoute<void>(builder: (_) => gatedPage())),
    );
    await tester.pumpAndSettle();
    expect(find.byKey(gated), findsOneWidget);

    navigator(tester).pop();
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));

    expect(find.byKey(gated), findsNothing);
    expect(find.byKey(placeholder), findsOneWidget);
  });

  testWidgets('gates during a secondary transition and recovers after pop', (
    tester,
  ) async {
    await pumpApp(tester);
    unawaited(
      navigator(
        tester,
      ).push(MaterialPageRoute<void>(builder: (_) => gatedPage())),
    );
    await tester.pumpAndSettle();
    expect(find.byKey(gated), findsOneWidget);

    unawaited(
      navigator(
        tester,
      ).push(MaterialPageRoute<void>(builder: (_) => const Scaffold())),
    );
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));
    // Mid secondary transition the fragile subtree must be unmounted.
    expect(find.byKey(gated), findsNothing);

    await tester.pumpAndSettle();
    navigator(tester).pop();
    await tester.pumpAndSettle();
    // Back at rest on the gated route: child is mounted again.
    expect(find.byKey(gated), findsOneWidget);
    expect(find.byKey(placeholder), findsNothing);
  });

  testWidgets('re-gates when the settled subtree moves under a fresh Transform', (
    tester,
  ) async {
    // Android's predictive back moves the route content (GlobalKey) under a
    // brand-new Transform.scale without any animation status change. The
    // padding changes the constraints so the moved subtree is laid out nested
    // under the transform's first layout, which is when `localToGlobal` throws.
    final subtree = GlobalKey();
    var wrapped = false;
    late StateSetter rebuild;
    await tester.pumpWidget(
      MaterialApp(
        home: StatefulBuilder(
          builder: (context, setState) {
            rebuild = setState;
            final child = KeyedSubtree(
              key: subtree,
              child: Scaffold(
                body: RouteTransitionGate(
                  placeholder: const SizedBox(key: placeholder),
                  builder: (_) => const _LocalToGlobalProbe(key: gated),
                ),
              ),
            );
            if (!wrapped) return child;
            return Padding(
              padding: const EdgeInsets.all(1),
              child: Transform.scale(scale: 1, child: child),
            );
          },
        ),
      ),
    );
    await tester.pump();
    await tester.pump();
    expect(find.byKey(gated), findsOneWidget);

    rebuild(() => wrapped = true);
    await tester.pump();
    expect(tester.takeException(), isNull);
    expect(find.byKey(placeholder), findsOneWidget);

    await tester.pump();
    expect(find.byKey(gated), findsOneWidget);
    expect(tester.takeException(), isNull);
  });

  testWidgets('keeps the child mounted while a back swipe drives the pop', (
    tester,
  ) async {
    // iOS back swipe: the edge detector is translucent, so the finger that
    // drives the pop animation is also down on the viewer. Unmounting it now
    // would route the next pointer move into a disposed State. (A programmatic
    // pop is harmless — the Navigator cancels active pointers first.)
    await pumpApp(tester);
    unawaited(
      navigator(
        tester,
      ).push(MaterialPageRoute<void>(builder: (_) => gatedPage())),
    );
    await tester.pumpAndSettle();
    expect(find.byKey(gated), findsOneWidget);

    final gesture = await tester.startGesture(const Offset(5, 300));
    await gesture.moveBy(const Offset(60, 0));
    await tester.pump();
    await gesture.moveBy(const Offset(60, 0));
    await tester.pump();
    // Pop animation is running (status reverse), finger still down.
    expect(find.byKey(gated), findsOneWidget);
    expect(find.byKey(placeholder), findsNothing);
    expect(tester.takeException(), isNull);

    await gesture.up();
    await tester.pump();
    expect(find.byKey(gated), findsNothing);
    await tester.pumpAndSettle();
    expect(tester.takeException(), isNull);
  }, variant: TargetPlatformVariant.only(TargetPlatform.iOS));

  testWidgets('holds the child back for one frame without a route animation', (
    tester,
  ) async {
    // The tab case: no route animation ever runs, but the ancestors (and any
    // freshly inserted tab-transition Transform) do their first layout in this
    // very frame, so the fragile subtree must not be part of it.
    await tester.pumpWidget(MaterialApp(home: gatedPage()));
    expect(find.byKey(placeholder), findsOneWidget);
    expect(find.byKey(gated), findsNothing);

    await tester.pump();
    expect(find.byKey(gated), findsOneWidget);
    expect(find.byKey(placeholder), findsNothing);
  });
}

/// Mimics SfPdfViewer: a stateful widget whose LayoutBuilder resolves a
/// child's global position during layout.
class _LocalToGlobalProbe extends StatefulWidget {
  const _LocalToGlobalProbe({super.key});

  @override
  State<_LocalToGlobalProbe> createState() => _LocalToGlobalProbeState();
}

class _LocalToGlobalProbeState extends State<_LocalToGlobalProbe> {
  final _viewport = GlobalKey();

  @override
  Widget build(BuildContext context) => LayoutBuilder(
    builder: (context, constraints) {
      final box = _viewport.currentContext?.findRenderObject() as RenderBox?;
      if (box != null && box.hasSize) box.localToGlobal(Offset.zero);
      return SizedBox.expand(key: _viewport);
    },
  );
}