import 'package:decimal/decimal.dart';
import 'package:fl_chart/fl_chart.dart';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.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/section_card.dart';
import '../portfolio/labels.dart' show formatPercent;
import 'data/income_api.dart';
import 'labels.dart';
import 'providers.dart';

/// Прогноз: expected income for the next N months, **always split by basis**.
///
/// The stacked bar and the table both carry the split rather than the total alone: a month
/// built entirely out of `history` is an extrapolation, and a month built out of `announced`
/// is nearly a fact. One number cannot say which.
class IncomeForecastTab extends ConsumerWidget {
  const IncomeForecastTab({super.key});

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

    return RefreshIndicator(
      onRefresh: () async => ref.invalidate(incomeForecastProvider),
      child: AsyncValueView(
        value: forecast,
        onRetry: () => ref.invalidate(incomeForecastProvider),
        data: (cached) {
          final data = cached.data;
          final bases = data.bases;
          return ListView(
            padding: const EdgeInsets.all(16),
            children: [
              const _HorizonChips(),
              const SizedBox(height: 12),
              Wrap(
                spacing: 12,
                runSpacing: 12,
                children: [
                  StatTile(
                    label: 'Ожидается всего',
                    value: MoneyText(data.totalRub, currency: 'RUB'),
                    note: 'за ${data.months.length} мес, до налога',
                  ),
                  StatTile(
                    label: 'Доходность к стоимости',
                    // null means "нет оценки стоимости" and must not read as 0 %
                    value: Text(formatPercent(data.annualYieldOnValue, signed: false)),
                    note: data.annualYieldOnValue == null
                        ? 'нет оценки текущей стоимости'
                        : 'ожидаемый доход / стоимость портфеля',
                  ),
                  for (final b in bases)
                    StatTile(
                      label: 'Основание: ${basisLabel(b)}',
                      value: MoneyText(_basisTotal(data, b).toString(), currency: 'RUB'),
                      note: basisDescription(b),
                      width: 220,
                    ),
                ],
              ),
              if (data.warnings.isNotEmpty) ...[
                const SizedBox(height: 16),
                _Warnings(warnings: data.warnings),
              ],
              const SizedBox(height: 16),
              if (data.months.isEmpty)
                const Padding(
                  padding: EdgeInsets.only(top: 48),
                  child: EmptyState(
                    icon: Icons.insights_outlined,
                    message: 'Прогнозировать нечего: ни объявленных выплат, ни истории.',
                  ),
                )
              else ...[
                SectionCard(
                  title: 'По месяцам',
                  subtitle: 'цвет столбца — основание прогноза',
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      _BasisLegend(bases: bases),
                      const SizedBox(height: 12),
                      SizedBox(
                        height: 220,
                        child: SingleChildScrollView(
                          scrollDirection: Axis.horizontal,
                          child: SizedBox(
                            width: (data.months.length * 52).toDouble().clamp(320, double.infinity),
                            child: _ForecastChart(months: data.months, bases: bases),
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
                const SizedBox(height: 16),
                SectionCard(
                  title: 'Разбивка по основанию',
                  child: _ForecastTable(months: data.months, bases: bases),
                ),
              ],
            ],
          );
        },
      ),
    );
  }
}

Decimal _basisTotal(IncomeForecast data, String basis) => data.months
    .map((m) => Decimal.tryParse(m.byBasis[basis] ?? '0') ?? Decimal.zero)
    .fold(Decimal.zero, (a, b) => a + b);

class _HorizonChips extends ConsumerWidget {
  const _HorizonChips();

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final months = ref.watch(forecastMonthsProvider);
    return Wrap(
      spacing: 8,
      children: [
        for (final m in const [6, 12, 24, 36])
          ChoiceChip(
            label: Text('$m мес'),
            selected: months == m,
            onSelected: (_) => ref.read(forecastMonthsProvider.notifier).state = m,
          ),
      ],
    );
  }
}

class _Warnings extends StatelessWidget {
  const _Warnings({required this.warnings});

  final List<String> warnings;

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;
    return Card(
      color: scheme.tertiaryContainer,
      child: Padding(
        padding: const EdgeInsets.all(12),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            for (final w in warnings)
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 2),
                child: Row(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    const Icon(Icons.warning_amber_outlined, size: 16),
                    const SizedBox(width: 8),
                    Expanded(child: Text(w)),
                  ],
                ),
              ),
          ],
        ),
      ),
    );
  }
}

class _BasisLegend extends StatelessWidget {
  const _BasisLegend({required this.bases});

  final List<String> bases;

  @override
  Widget build(BuildContext context) {
    return Wrap(
      spacing: 16,
      runSpacing: 6,
      children: [
        for (final b in bases)
          Tooltip(
            message: basisDescription(b),
            child: Row(
              mainAxisSize: MainAxisSize.min,
              children: [
                Container(
                  width: 10,
                  height: 10,
                  decoration: BoxDecoration(color: basisColor(b), shape: BoxShape.circle),
                ),
                const SizedBox(width: 6),
                Text(basisLabel(b), style: Theme.of(context).textTheme.bodySmall),
              ],
            ),
          ),
      ],
    );
  }
}

class _ForecastChart extends StatelessWidget {
  const _ForecastChart({required this.months, required this.bases});

  final List<ForecastMonth> months;
  final List<String> bases;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final maxY = months.fold<double>(0, (m, r) {
      final v = (Decimal.tryParse(r.amountRub) ?? Decimal.zero).toDouble();
      return v > m ? v : m;
    });

    return BarChart(
      BarChartData(
        maxY: maxY == 0 ? 1 : maxY * 1.15,
        gridData: const FlGridData(show: true, drawVerticalLine: false),
        borderData: FlBorderData(show: false),
        titlesData: FlTitlesData(
          topTitles: const AxisTitles(),
          rightTitles: const AxisTitles(),
          leftTitles: const AxisTitles(
            sideTitles: SideTitles(showTitles: true, reservedSize: 56),
          ),
          bottomTitles: AxisTitles(
            sideTitles: SideTitles(
              showTitles: true,
              reservedSize: 28,
              getTitlesWidget: (value, meta) {
                final i = value.round();
                if (i < 0 || i >= months.length) return const SizedBox.shrink();
                if (months.length > 14 && i.isOdd) return const SizedBox.shrink();
                final m = months[i].month;
                return Text(
                  m == null ? '—' : ruMonthYearShort(m),
                  style: theme.textTheme.bodySmall,
                );
              },
            ),
          ),
        ),
        barTouchData: BarTouchData(
          touchTooltipData: BarTouchTooltipData(
            getTooltipItem: (group, _, rod, _) {
              final m = months[group.x];
              final parts = [
                for (final b in bases)
                  if ((Decimal.tryParse(m.byBasis[b] ?? '0') ?? Decimal.zero) > Decimal.zero)
                    '${basisLabel(b)}: ${MoneyText.format(m.byBasis[b]!, 'RUB')}',
              ];
              return BarTooltipItem(
                '${m.month == null ? '—' : ruMonthYearShort(m.month!)}\n'
                '${MoneyText.format(m.amountRub, 'RUB')}'
                '${parts.isEmpty ? '' : '\n${parts.join('\n')}'}',
                theme.textTheme.bodySmall ?? const TextStyle(),
              );
            },
          ),
        ),
        barGroups: [
          for (var i = 0; i < months.length; i++)
            BarChartGroupData(x: i, barRods: [_stackedRod(months[i])]),
        ],
      ),
    );
  }

  /// One rod per month, stacked by basis: the height is the month's total, the segments are
  /// where that total came from.
  BarChartRodData _stackedRod(ForecastMonth m) {
    final stack = <BarChartRodStackItem>[];
    var from = 0.0;
    for (final b in bases) {
      final v = (Decimal.tryParse(m.byBasis[b] ?? '0') ?? Decimal.zero).toDouble();
      if (v <= 0) continue;
      stack.add(BarChartRodStackItem(from, from + v, basisColor(b)));
      from += v;
    }
    final total = (Decimal.tryParse(m.amountRub) ?? Decimal.zero).toDouble();
    return BarChartRodData(
      toY: from > 0 ? from : total,
      rodStackItems: stack,
      color: Colors.transparent,
      width: 16,
      borderRadius: const BorderRadius.vertical(top: Radius.circular(2)),
    );
  }
}

class _ForecastTable extends StatelessWidget {
  const _ForecastTable({required this.months, required this.bases});

  final List<ForecastMonth> months;
  final List<String> bases;

  @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)),
          for (final b in bases)
            DataColumn(
              label: Tooltip(
                message: basisDescription(b),
                child: Text(basisLabel(b), style: headerStyle),
              ),
              numeric: true,
            ),
          DataColumn(label: Text('Итого', style: headerStyle), numeric: true),
        ],
        rows: [
          for (final m in months)
            DataRow(
              cells: [
                DataCell(Text(m.month == null ? '—' : ruMonthYearShort(m.month!))),
                for (final b in bases)
                  DataCell(MoneyText(m.byBasis[b] ?? '0', currency: 'RUB')),
                DataCell(MoneyText(
                  m.amountRub,
                  currency: 'RUB',
                  style: Theme.of(context).textTheme.titleSmall,
                )),
              ],
            ),
        ],
      ),
    );
  }
}