import 'package:decimal/decimal.dart';
import 'package:fintracker_api/fintracker_api.dart';
import 'package:fl_chart/fl_chart.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/theme/chart_colors.dart';
import '../../core/utils/ru_date.dart';
import '../../core/widgets/async_value_view.dart';
import '../../core/widgets/empty_state.dart';
import '../../core/widgets/money_text.dart';
import '../../core/widgets/stale_banner.dart';
import 'providers.dart';

const _incomeColor = ChartColors.income;
const _expenseColor = ChartColors.expense;

double _d(String s) => Decimal.parse(s).toDouble();

/// Потоки: 24 months of cashflow, a grouped bar chart on top and the full
/// breakdown as a scrollable table below. Tapping a row opens Категории for
/// that month.
class CashflowPage extends ConsumerWidget {
  const CashflowPage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final monthly = ref.watch(cashflowMonthly24Provider);
    final stale = oldestFetch([monthly.valueOrNull?.fetchedAt]);

    return Scaffold(
      appBar: AppBar(title: const Text('Потоки')),
      body: RefreshIndicator(
        onRefresh: () async => ref.invalidate(cashflowMonthly24Provider),
        child: AsyncValueView(
          value: monthly,
          onRetry: () => ref.invalidate(cashflowMonthly24Provider),
          data: (cached) {
            final rows = cached.data;
            if (rows.isEmpty) {
              return ListView(
                children: const [
                  EmptyState(
                    icon: Icons.swap_horiz_outlined,
                    message: 'Данных о потоках ещё нет — нужна синхронизация.',
                  ),
                ],
              );
            }
            return ListView(
              padding: const EdgeInsets.all(16),
              children: [
                if (stale != null) StaleBanner(fetchedAt: stale),
                const _Legend(),
                const SizedBox(height: 8),
                SizedBox(
                  height: 240,
                  child: SingleChildScrollView(
                    scrollDirection: Axis.horizontal,
                    reverse: true,
                    child: SizedBox(
                      width: (rows.length * 56).toDouble().clamp(320, double.infinity),
                      child: _CashflowChart(rows: rows),
                    ),
                  ),
                ),
                const SizedBox(height: 24),
                _Table(rows: rows),
              ],
            );
          },
        ),
      ),
    );
  }
}

class _Legend extends StatelessWidget {
  const _Legend();

  @override
  Widget build(BuildContext context) {
    return Row(
      children: const [
        _LegendDot(color: _incomeColor, label: 'Доход'),
        SizedBox(width: 16),
        _LegendDot(color: _expenseColor, label: 'Расход'),
      ],
    );
  }
}

class _LegendDot extends StatelessWidget {
  const _LegendDot({required this.color, required this.label});
  final Color color;
  final String label;

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisSize: MainAxisSize.min,
      children: [
        Container(width: 10, height: 10, decoration: BoxDecoration(color: color, shape: BoxShape.circle)),
        const SizedBox(width: 6),
        Text(label, style: Theme.of(context).textTheme.bodySmall),
      ],
    );
  }
}

class _CashflowChart extends StatelessWidget {
  const _CashflowChart({required this.rows});

  final List<CashFlowMonth> rows;

  @override
  Widget build(BuildContext context) {
    final maxY = rows.fold<double>(
      0,
      (m, r) => [m, _d(r.incomeRub), _d(r.expenseRub)].reduce((a, b) => a > b ? a : b),
    );
    return BarChart(
      BarChartData(
        maxY: maxY * 1.1,
        gridData: const FlGridData(drawVerticalLine: false),
        borderData: FlBorderData(show: false),
        titlesData: FlTitlesData(
          topTitles: const AxisTitles(sideTitles: SideTitles(showTitles: false)),
          rightTitles: const AxisTitles(sideTitles: SideTitles(showTitles: false)),
          leftTitles: const AxisTitles(sideTitles: SideTitles(showTitles: false)),
          bottomTitles: AxisTitles(
            sideTitles: SideTitles(
              showTitles: true,
              getTitlesWidget: (value, meta) {
                final i = value.toInt();
                if (i < 0 || i >= rows.length) return const SizedBox.shrink();
                return Padding(
                  padding: const EdgeInsets.only(top: 6),
                  child: Text(ruMonthYearShort(rows[i].month), style: const TextStyle(fontSize: 10)),
                );
              },
            ),
          ),
        ),
        barTouchData: BarTouchData(
          touchTooltipData: BarTouchTooltipData(
            getTooltipItem: (group, groupIndex, rod, rodIndex) {
              final label = rodIndex == 0 ? 'Доход' : 'Расход';
              return BarTooltipItem(
                '$label\n${MoneyText.format(rod.toY.toStringAsFixed(2), 'RUB')}',
                const TextStyle(color: Colors.white, fontSize: 12),
              );
            },
          ),
        ),
        barGroups: [
          for (var i = 0; i < rows.length; i++)
            BarChartGroupData(
              x: i,
              barRods: [
                BarChartRodData(toY: _d(rows[i].incomeRub), color: _incomeColor, width: 8),
                BarChartRodData(toY: _d(rows[i].expenseRub), color: _expenseColor, width: 8),
              ],
              barsSpace: 2,
            ),
        ],
      ),
    );
  }
}

class _Table extends StatelessWidget {
  const _Table({required this.rows});

  final List<CashFlowMonth> rows;

  @override
  Widget build(BuildContext context) {
    final headerStyle = Theme.of(context).textTheme.labelMedium;
    return SingleChildScrollView(
      scrollDirection: Axis.horizontal,
      child: DataTable(
        columns: [
          DataColumn(label: Text('Месяц', style: headerStyle)),
          DataColumn(label: Text('Доход', style: headerStyle), numeric: true),
          DataColumn(label: Text('Расход', style: headerStyle), numeric: true),
          DataColumn(label: Text('Базовые', style: headerStyle), numeric: true),
          DataColumn(label: Text('Разовые', style: headerStyle), numeric: true),
          DataColumn(label: Text('В сбережения', style: headerStyle), numeric: true),
          DataColumn(label: Text('Норма сбер., %', style: headerStyle), numeric: true),
        ],
        rows: [
          for (final r in rows.reversed)
            DataRow(
              onSelectChanged: (_) => context.go('/categories?month=${monthKey(r.month)}'),
              cells: [
                DataCell(Text(ruMonthYearShort(r.month))),
                DataCell(MoneyText(r.incomeRub, currency: 'RUB')),
                DataCell(MoneyText(r.expenseRub, currency: 'RUB')),
                DataCell(MoneyText(r.baselineRub, currency: 'RUB')),
                DataCell(MoneyText(r.oneOffRub, currency: 'RUB')),
                DataCell(MoneyText(r.savingsTransferRub, currency: 'RUB')),
                DataCell(Text(r.savingsRate == null
                    ? '—'
                    : '${(_d(r.savingsRate!) * 100).toStringAsFixed(1)}%')),
              ],
            ),
        ],
      ),
    );
  }
}