import 'package:flutter_test/flutter_test.dart';
import 'package:worldhopper/models/entry.dart';
import 'package:worldhopper/models/feed.dart';
import 'package:worldhopper/providers/series_navigation_provider.dart';

Entry _entry(String id, String title) => Entry(id: id, title: title);

Feed _feedWith(List<Entry> entries) =>
    Feed(id: 'feed-1', title: 'Series', entries: entries);

/// Extracts the next-in-series logic from the provider for unit testing.
/// This mirrors the logic in nextInSeriesProvider without needing Riverpod.
Entry? _findNextInSeries(Feed feed, String currentEntryId) {
  final entries = feed.entries;
  for (var i = 0; i < entries.length; i++) {
    if (entries[i].id == currentEntryId) {
      if (i + 1 < entries.length) {
        return entries[i + 1];
      }
      return null;
    }
  }
  return null;
}

void main() {
  group('nextInSeriesProvider', () {
    test('returns next entry when current is in the middle', () {
      final feed = _feedWith([
        _entry('ch1', 'Chapter 1'),
        _entry('ch2', 'Chapter 2'),
        _entry('ch3', 'Chapter 3'),
      ]);

      final result = _findNextInSeries(feed, 'ch1');

      expect(result, isNotNull);
      expect(result!.id, 'ch2');
      expect(result.title, 'Chapter 2');
    });

    test('returns next entry when current is second-to-last', () {
      final feed = _feedWith([
        _entry('ch1', 'Chapter 1'),
        _entry('ch2', 'Chapter 2'),
        _entry('ch3', 'Chapter 3'),
      ]);

      final result = _findNextInSeries(feed, 'ch2');

      expect(result, isNotNull);
      expect(result!.id, 'ch3');
    });

    test('returns null when current entry is the last', () {
      final feed = _feedWith([
        _entry('ch1', 'Chapter 1'),
        _entry('ch2', 'Chapter 2'),
        _entry('ch3', 'Chapter 3'),
      ]);

      final result = _findNextInSeries(feed, 'ch3');

      expect(result, isNull);
    });

    test('returns null when current entry is not found in feed', () {
      final feed = _feedWith([
        _entry('ch1', 'Chapter 1'),
        _entry('ch2', 'Chapter 2'),
      ]);

      final result = _findNextInSeries(feed, 'unknown-id');

      expect(result, isNull);
    });

    test('returns null for an empty feed', () {
      final feed = _feedWith([]);

      final result = _findNextInSeries(feed, 'ch1');

      expect(result, isNull);
    });

    test('returns null for single-entry feed', () {
      final feed = _feedWith([_entry('ch1', 'Only Chapter')]);

      final result = _findNextInSeries(feed, 'ch1');

      expect(result, isNull);
    });
  });

  group('NextInSeriesRequest equality', () {
    test('equal requests have same hashCode', () {
      const a = NextInSeriesRequest(
        serverId: 's1',
        feedUrl: '/feed',
        currentEntryId: 'ch1',
      );
      const b = NextInSeriesRequest(
        serverId: 's1',
        feedUrl: '/feed',
        currentEntryId: 'ch1',
      );

      expect(a, equals(b));
      expect(a.hashCode, equals(b.hashCode));
    });

    test('different requests are not equal', () {
      const a = NextInSeriesRequest(
        serverId: 's1',
        feedUrl: '/feed',
        currentEntryId: 'ch1',
      );
      const b = NextInSeriesRequest(
        serverId: 's1',
        feedUrl: '/feed',
        currentEntryId: 'ch2',
      );

      expect(a, isNot(equals(b)));
    });
  });
}