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

import '../../core/cache/cached.dart';
import '../../core/widgets/async_value_view.dart';
import '../../core/widgets/stale_banner.dart';
import 'allocation_tab.dart';
import 'benchmarks_card.dart';
import 'holdings_tab.dart';
import 'providers.dart';

/// Портфель: позиции и аллокация as two tabs of one screen, sharing one scope.
///
/// They are tabs rather than two navigation destinations because they answer two halves of
/// the same question, and because a tenth item in the bottom bar would leave 40 px per
/// label on a phone.
///
/// One offline banner covers both tabs (`docs/ai/offline-cache.md`) — `TabBarView` builds
/// both eagerly anyway, so watching every provider here to compute it costs nothing extra.
class PortfolioPage extends ConsumerWidget {
  const PortfolioPage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final stale = oldestFetch([
      ref.watch(portfolioSummaryProvider).valueOrNull?.fetchedAt,
      ref.watch(holdingsProvider).valueOrNull?.fetchedAt,
      ref.watch(valueSeriesProvider).valueOrNull?.fetchedAt,
      ref.watch(portfolioReturnsProvider).valueOrNull?.fetchedAt,
      ref.watch(benchmarkRowsProvider).valueOrNull?.fetchedAt,
      ref.watch(allocationProvider).valueOrNull?.fetchedAt,
    ]);

    return DefaultTabController(
      length: 2,
      child: Scaffold(
        appBar: AppBar(
          title: const Text('Портфель'),
          actions: const [_ScopeSelector(), SizedBox(width: 8)],
          bottom: const TabBar(
            tabs: [Tab(text: 'Позиции'), Tab(text: 'Аллокация')],
          ),
        ),
        body: Column(
          children: [
            if (stale != null)
              Padding(
                padding: const EdgeInsets.fromLTRB(16, 12, 16, 0),
                child: StaleBanner(fetchedAt: stale),
              ),
            const Expanded(
              child: TabBarView(children: [HoldingsTab(), AllocationTab()]),
            ),
          ],
        ),
      ),
    );
  }
}

/// Switches every portfolio screen at once. Hidden while there is nothing to choose
/// between — a dropdown with one option is furniture, not a control.
class _ScopeSelector extends ConsumerWidget {
  const _ScopeSelector();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final scopes = ref.watch(scopesProvider);
    final current = ref.watch(scopeProvider);

    return AsyncValueView<List<ScopeOut>>(
      value: scopes,
      data: (rows) {
        if (rows.length < 2) return const SizedBox.shrink();
        final known = rows.any((s) => s.scope == current) ? current : rows.first.scope;
        return DropdownButtonHideUnderline(
          child: DropdownButton<String>(
            value: known,
            borderRadius: BorderRadius.circular(8),
            items: [
              for (final s in rows)
                DropdownMenuItem(
                  value: s.scope,
                  child: Text(s.name, overflow: TextOverflow.ellipsis),
                ),
            ],
            onChanged: (value) {
              if (value != null) ref.read(scopeProvider.notifier).state = value;
            },
          ),
        );
      },
    );
  }
}