import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../providers/db_provider.dart';
import '../theme/app_theme.dart';

class BudgetScreen extends ConsumerWidget {
  const BudgetScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final groups = ref.watch(categoryGroupsProvider).valueOrNull ?? [];
    final catsByGroup = ref.watch(categoriesByGroupProvider);

    return ListView(
      padding: const EdgeInsets.fromLTRB(16, 8, 16, 90),
      children: [
        Card(
          child: Padding(
            padding: const EdgeInsets.all(20),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text('Budget du mois', style: Theme.of(context).textTheme.titleMedium),
                const SizedBox(height: 4),
                Text('Juillet 2026', style: Theme.of(context).textTheme.bodySmall),
              ],
            ),
          ),
        ),
        const SizedBox(height: 16),
        ...groups.map((group) {
          final cats = catsByGroup[group.id] ?? [];
          if (cats.isEmpty) return const SizedBox.shrink();
          return _CategoryGroupTile(group: group, categoryIds: cats.map((c) => c.id).toList());
        }),
      ],
    );
  }
}

class _CategoryGroupTile extends ConsumerWidget {
  final CategoryGroup group;
  final List<int> categoryIds;

  const _CategoryGroupTile({required this.group, required this.categoryIds});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final expanded = ref.watch(_expandedGroupProvider(group.id));
    final cats = ref.watch(categoriesByGroupProvider)[group.id] ?? [];

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        InkWell(
          onTap: () => ref.read(_expandedGroupProvider(group.id).notifier).toggle(),
          borderRadius: BorderRadius.circular(8),
          child: Padding(
            padding: const EdgeInsets.symmetric(vertical: 12, horizontal: 4),
            child: Row(
              children: [
                Icon(
                  expanded ? Icons.keyboard_arrow_down : Icons.keyboard_arrow_right,
                  size: 18,
                  color: Theme.of(context).colorScheme.onSurfaceVariant,
                ),
                const SizedBox(width: 8),
                Text(group.name,
                    style: Theme.of(context)
                        .textTheme
                        .titleSmall
                        ?.copyWith(fontWeight: FontWeight.w600)),
                const Spacer(),
                Text(
                  formatCurrency(
                    cats.fold(0.0, (s, c) => s + ref.watch(categoryRemainingProvider(c.id))),
                  ),
                  style: Theme.of(context).textTheme.bodySmall,
                ),
              ],
            ),
          ),
        ),
        if (expanded)
          ...cats.map((c) => _CategoryRow(categoryId: c.id)),
        const Divider(height: 1),
      ],
    );
  }
}

class _CategoryRow extends ConsumerWidget {
  final int categoryId;

  const _CategoryRow({required this.categoryId});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final cats = ref.watch(categoriesByGroupProvider);
    final category = cats.values
        .expand((list) => list)
        .firstWhere((c) => c.id == categoryId, orElse: () => throw StateError('missing'));

    final budgeted = ref.watch(monthlyBudgetProvider(categoryId)) ?? 0.0;
    final spent = ref.watch(categorySpentProvider(categoryId));
    final remaining = ref.watch(categoryRemainingProvider(categoryId));
    final pct = budgeted > 0 ? ((budgeted + spent) / budgeted).clamp(0.0, 1.0) : 0.0;

    return Padding(
      padding: const EdgeInsets.only(left: 8, bottom: 4),
      child: Card(
        margin: EdgeInsets.zero,
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 10),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Row(
                children: [
                  Expanded(
                    child: Text(category.name, style: Theme.of(context).textTheme.bodyMedium),
                  ),
                  Text(
                    formatCurrency(remaining),
                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                          fontWeight: FontWeight.w600,
                          color: remaining >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
                        ),
                  ),
                ],
              ),
              const SizedBox(height: 4),
              ClipRRect(
                borderRadius: BorderRadius.circular(4),
                child: LinearProgressIndicator(
                  value: pct,
                  backgroundColor: Theme.of(context).colorScheme.outlineVariant,
                  valueColor: AlwaysStoppedAnimation<Color>(
                    remaining >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
                  ),
                  minHeight: 4,
                ),
              ),
              const SizedBox(height: 2),
              Row(
                children: [
                  Text('Budget: ${formatCurrency(budgeted)}',
                      style: Theme.of(context).textTheme.bodySmall),
                  const SizedBox(width: 12),
                  Text('Dépensé: ${formatCurrency(spent.abs())}',
                      style: Theme.of(context).textTheme.bodySmall),
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class _ExpandedGroupNotifier extends StateNotifier<bool> {
  _ExpandedGroupNotifier() : super(true);

  void toggle() => state = !state;
}

final _expandedGroupProvider =
    StateNotifierProvider.family<_ExpandedGroupNotifier, bool, int>(
        (ref, id) => _ExpandedGroupNotifier());