import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:intl/intl.dart';

import '../domain/bracket.dart';
import '../infrastructure/brackets_repository.dart';
import 'widgets/bracket_tree_widget.dart';

/// Top-level Brackets tab.
///
/// Routing behavior:
///   * No brackets → empty state.
///   * Exactly one bracket → render its tree inline (the common case for the
///     MVP, where each event has a single main draw).
///   * Multiple brackets → list view, tap to drill into `/brackets/:id`.
class BracketsScreen extends ConsumerWidget {
  const BracketsScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final bracketsAsync = ref.watch(bracketsStreamProvider);

    return Scaffold(
      appBar: AppBar(title: const Text('Brackets')),
      body: bracketsAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (error, _) => _ErrorState(
          message: error.toString(),
          onRetry: () => ref.invalidate(bracketsStreamProvider),
        ),
        data: (brackets) {
          if (brackets.isEmpty) {
            return const _EmptyState();
          }
          if (brackets.length == 1) {
            return _SingleBracketView(bracket: brackets.first);
          }
          return _BracketsList(brackets: brackets);
        },
      ),
    );
  }
}

class _SingleBracketView extends StatelessWidget {
  const _SingleBracketView({required this.bracket});

  final Bracket bracket;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final scheme = theme.colorScheme;

    return Column(
      children: [
        Padding(
          padding: const EdgeInsets.fromLTRB(16, 12, 16, 8),
          child: Row(
            children: [
              Icon(Icons.emoji_events, color: scheme.primary),
              const SizedBox(width: 8),
              Expanded(
                child: Text(
                  bracket.name,
                  style: theme.textTheme.titleMedium?.copyWith(
                    fontWeight: FontWeight.w700,
                  ),
                ),
              ),
            ],
          ),
        ),
        Expanded(
          child: Center(child: BracketTreeWidget(bracket: bracket)),
        ),
        Container(
          width: double.infinity,
          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 10),
          decoration: BoxDecoration(
            color: scheme.surfaceContainerHighest,
            border: Border(top: BorderSide(color: scheme.outlineVariant)),
          ),
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Icon(
                Icons.swap_horiz,
                size: 18,
                color: scheme.onSurfaceVariant,
              ),
              const SizedBox(width: 6),
              Text(
                'Scroll horizontally to see all rounds',
                style: theme.textTheme.bodySmall?.copyWith(
                  color: scheme.onSurfaceVariant,
                ),
              ),
            ],
          ),
        ),
      ],
    );
  }
}

class _BracketsList extends StatelessWidget {
  const _BracketsList({required this.brackets});

  final List<Bracket> brackets;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final scheme = theme.colorScheme;
    final dateFormat = DateFormat('MMM d, y');

    return ListView.separated(
      padding: const EdgeInsets.symmetric(vertical: 8),
      itemCount: brackets.length,
      separatorBuilder: (_, _) => const SizedBox(height: 4),
      itemBuilder: (context, index) {
        final bracket = brackets[index];
        final totalMatches =
            bracket.rounds.fold<int>(0, (sum, r) => sum + r.matches.length);
        return Card(
          margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 4),
          clipBehavior: Clip.antiAlias,
          child: InkWell(
            onTap: () => context.go('/brackets/${bracket.id}'),
            child: Padding(
              padding: const EdgeInsets.all(16),
              child: Row(
                children: [
                  CircleAvatar(
                    backgroundColor: scheme.primaryContainer,
                    foregroundColor: scheme.onPrimaryContainer,
                    child: const Icon(Icons.emoji_events),
                  ),
                  const SizedBox(width: 12),
                  Expanded(
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text(
                          bracket.name,
                          style: theme.textTheme.titleMedium?.copyWith(
                            fontWeight: FontWeight.w700,
                          ),
                        ),
                        const SizedBox(height: 4),
                        Text(
                          '${bracket.rounds.length} rounds  ·  '
                          '$totalMatches matches  ·  '
                          'Created ${dateFormat.format(bracket.createdAt)}',
                          style: theme.textTheme.bodySmall?.copyWith(
                            color: scheme.onSurfaceVariant,
                          ),
                        ),
                      ],
                    ),
                  ),
                  Icon(Icons.chevron_right, color: scheme.onSurfaceVariant),
                ],
              ),
            ),
          ),
        );
      },
    );
  }
}

class _EmptyState extends StatelessWidget {
  const _EmptyState();

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(32),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(
              Icons.emoji_events_outlined,
              size: 64,
              color: theme.colorScheme.onSurfaceVariant,
            ),
            const SizedBox(height: 16),
            Text(
              'No brackets yet',
              style: theme.textTheme.titleMedium,
            ),
            const SizedBox(height: 8),
            Text(
              'Tournament brackets will appear here once an event reaches '
              'its draw stage.',
              textAlign: TextAlign.center,
              style: theme.textTheme.bodyMedium?.copyWith(
                color: theme.colorScheme.onSurfaceVariant,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _ErrorState extends StatelessWidget {
  const _ErrorState({required this.message, required this.onRetry});

  final String message;
  final VoidCallback onRetry;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(32),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(Icons.error_outline,
                size: 64, color: theme.colorScheme.error),
            const SizedBox(height: 16),
            Text(
              'Could not load brackets',
              style: theme.textTheme.titleMedium,
            ),
            const SizedBox(height: 8),
            Text(
              message,
              textAlign: TextAlign.center,
              style: theme.textTheme.bodySmall?.copyWith(
                color: theme.colorScheme.onSurfaceVariant,
              ),
            ),
            const SizedBox(height: 16),
            FilledButton.tonalIcon(
              onPressed: onRetry,
              icon: const Icon(Icons.refresh),
              label: const Text('Try again'),
            ),
          ],
        ),
      ),
    );
  }
}