fin-tracker/app/lib/features/rebalance/rebalance_page.dart

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

import '../../core/cache/cached.dart';
import '../../core/widgets/async_value_view.dart';
import '../../core/widgets/empty_state.dart';
import '../../core/widgets/stale_banner.dart';
import '../portfolio/labels.dart' show dimensionLabels;
import '../portfolios/providers.dart' show portfolioListProvider;
import 'data/rebalance_api.dart';
import 'plan_tab.dart';
import 'providers.dart';
import 'targets_tab.dart';

/// Ребалансировка: the target weights on one tab, the resulting recommendations on the
/// other. Both are per portfolio and per dimension, so the pickers live in the app bar and
/// drive both tabs at once.
///
/// One offline banner covers both tabs (`docs/ai/offline-cache.md`) — both providers are
/// already watched by their own tab, so watching them again here to compute it costs
/// nothing extra. `portfoliosProvider` itself is a selector derived from the un-cached
/// `scopesProvider` (see `portfolio/providers.dart`) and does not contribute a `fetchedAt`.
class RebalancePage extends ConsumerWidget {
  const RebalancePage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final portfolios = ref.watch(portfoliosProvider);
    final stale = oldestFetch([
      ref.watch(targetsProvider).valueOrNull?.fetchedAt,
      ref.watch(rebalancePlanProvider).valueOrNull?.fetchedAt,
    ]);

    return DefaultTabController(
      length: 2,
      child: Scaffold(
        appBar: AppBar(
          title: const Text('Ребалансировка'),
          actions: [
            const _PortfolioSelector(),
            const _DimensionSelector(),
            IconButton(
              tooltip: 'Обновить',
              icon: const Icon(Icons.refresh),
              onPressed: () => invalidateRebalanceProviders(ref),
            ),
          ],
          bottom: const TabBar(
            tabs: [
              Tab(text: 'Целевые веса'),
              Tab(text: 'Рекомендации'),
            ],
          ),
        ),
        body: Column(
          children: [
            if (stale != null)
              Padding(
                padding: const EdgeInsets.fromLTRB(16, 12, 16, 0),
                child: StaleBanner(fetchedAt: stale),
              ),
            Expanded(
              child: AsyncValueView(
                value: portfolios,
                onRetry: () => ref.invalidate(portfoliosProvider),
                data: (list) {
                  if (list.isEmpty) {
                    // A portfolio can exist yet be absent here: this list comes from the
                    // analytics scopes, which only cover accounts that have ledger events.
                    final created =
                        ref
                            .watch(portfolioListProvider)
                            .valueOrNull
                            ?.isNotEmpty ??
                        false;
                    return Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: [
                        EmptyState(
                          icon: Icons.pie_chart_outline,
                          message: created
                              ? 'Портфели есть, но в них нет счетов с бумагами.\n'
                                    'Добавьте брокерские счета: у счетов ZenMoney нет сделок, '
                                    'считать по ним нечего.'
                              : 'Портфелей пока нет.\n'
                                    'Ребалансировка считается по портфелю — набору счетов.',
                        ),
                        FilledButton.icon(
                          onPressed: () => context.go('/portfolios'),
                          icon: Icon(created ? Icons.edit_outlined : Icons.add),
                          label: Text(
                            created ? 'Изменить портфели' : 'Создать портфель',
                          ),
                        ),
                      ],
                    );
                  }
                  final selected = ref.watch(selectedPortfolioProvider);
                  if (selected == null || !list.any((p) => p.id == selected)) {
                    // pick the first portfolio once, after the list is known
                    WidgetsBinding.instance.addPostFrameCallback((_) {
                      ref.read(selectedPortfolioProvider.notifier).state =
                          list.first.id;
                    });
                    return const Center(child: CircularProgressIndicator());
                  }
                  return const TabBarView(
                    children: [TargetsTab(), RebalancePlanTab()],
                  );
                },
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _PortfolioSelector extends ConsumerWidget {
  const _PortfolioSelector();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final portfolios =
        ref.watch(portfoliosProvider).valueOrNull ?? const <PortfolioRef>[];
    final selected = ref.watch(selectedPortfolioProvider);
    if (portfolios.length < 2 || selected == null)
      return const SizedBox.shrink();
    return DropdownButtonHideUnderline(
      child: DropdownButton<int>(
        value: portfolios.any((p) => p.id == selected)
            ? selected
            : portfolios.first.id,
        borderRadius: BorderRadius.circular(8),
        items: [
          for (final p in portfolios)
            DropdownMenuItem(
              value: p.id,
              child: Text(p.name, overflow: TextOverflow.ellipsis),
            ),
        ],
        onChanged: (v) {
          if (v != null) ref.read(selectedPortfolioProvider.notifier).state = v;
        },
      ),
    );
  }
}

class _DimensionSelector extends ConsumerWidget {
  const _DimensionSelector();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final current = ref.watch(targetDimensionProvider);
    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 8),
      child: DropdownButtonHideUnderline(
        child: DropdownButton<String>(
          value: current,
          borderRadius: BorderRadius.circular(8),
          items: [
            for (final d in targetDimensions)
              DropdownMenuItem(value: d, child: Text(dimensionLabels[d] ?? d)),
          ],
          onChanged: (v) {
            if (v != null) ref.read(targetDimensionProvider.notifier).state = v;
          },
        ),
      ),
    );
  }
}