// Version: 1.0.0 | Created: 2026-07-04
// Deterministic test for the chat timeline's scroll-to-latest button.
// Playwright cannot drive scrolling on the Flutter CanvasKit surface, so the
// jump-to-latest behaviour is verified here against the real widget tree.

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:matrix/matrix.dart';

import 'package:m8chat_app/core/network/matrix_client.dart';
import 'package:m8chat_app/features/chat/domain/message_model.dart';
import 'package:m8chat_app/features/chat/presentation/chat_controller.dart';
import 'package:m8chat_app/features/chat/presentation/chat_screen.dart';

void main() {
  testWidgets(
    'jump-to-latest button appears when scrolled up and returns to bottom',
    (tester) async {
      const roomId = '!scrolltest:server';
      final base = DateTime(2026, 7, 4, 8);
      // Index 0 is the newest message (the timeline stream is newest-first).
      final messages = [
        for (var i = 40; i >= 1; i--)
          MessageModel(
            eventId: '\$e$i',
            roomId: roomId,
            senderId: '@me:server',
            senderDisplayName: 'Me',
            timestamp: base.add(Duration(seconds: i)),
            type: MessageType.text,
            body: 'Message $i',
            isMine: true,
          ),
      ];

      await tester.pumpWidget(
        ProviderScope(
          overrides: [
            matrixClientProvider.overrideWithValue(Client('test-client')),
            chatTimelineProvider(
              roomId,
            ).overrideWith((ref) => Stream.value(messages)),
          ],
          child: const MaterialApp(home: ChatScreen(roomId: roomId)),
        ),
      );
      await tester.pumpAndSettle();

      final listView = find.byType(ListView);
      expect(listView, findsOneWidget);

      double offset() =>
          tester.state<ScrollableState>(find.byType(Scrollable).first)
              .position
              .pixels;

      // Starts pinned to the newest message (offset 0 in a reverse list).
      expect(offset(), 0);

      // Scroll up toward older messages (reverse list: drag content down).
      await tester.drag(listView, const Offset(0, 900));
      await tester.pumpAndSettle();
      expect(
        offset(),
        greaterThan(400),
        reason: 'should have scrolled well past the button threshold',
      );

      // The jump-to-latest button is now shown; tap it.
      final jumpButton = find.byIcon(Icons.arrow_downward);
      expect(jumpButton, findsOneWidget);
      await tester.tap(jumpButton);
      await tester.pumpAndSettle();

      // Back at the newest message.
      expect(offset(), 0);
    },
  );
}