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 '../../core/theme/chart_colors.dart';
import '../../core/widgets/async_value_view.dart';
import '../../core/widgets/empty_state.dart';
import '../../core/widgets/money_text.dart';
import 'labels.dart';
import 'providers.dart';

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

/// Fixed categorical order — slot colours assigned by position in the sorted buckets, never
/// by rank across dimensions, so a bucket keeps its colour as the portfolio moves.
const _palette = [
  ChartColors.slot1Blue,
  ChartColors.slot2Orange,
  ChartColors.slot3Aqua,
  ChartColors.slot4Yellow,
  ChartColors.slot5Magenta,
];

/// Аллокация: one donut per dimension, each over the same total (securities plus cash).
class AllocationTab extends ConsumerWidget {
  const AllocationTab({super.key});

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

    return RefreshIndicator(
      onRefresh: () async => ref.invalidate(allocationProvider),
      child: AsyncValueView(
        value: allocation,
        onRetry: () => ref.invalidate(allocationProvider),
        data: (rows) {
          if (rows.isEmpty) {
            return ListView(
              children: const [
                EmptyState(
                  icon: Icons.donut_large_outlined,
                  message: 'Аллокации ещё нет — нужен пересчёт метрик.',
                ),
              ],
            );
          }
          final byDimension = <AllocationDimension, List<AllocationBucket>>{};
          for (final row in rows) {
            byDimension.putIfAbsent(row.dimension, () => []).add(row);
          }
          return ListView(
            padding: const EdgeInsets.all(16),
            children: [
              for (final entry in byDimension.entries) ...[
                _DimensionCard(dimension: entry.key, buckets: entry.value),
                const SizedBox(height: 16),
              ],
            ],
          );
        },
      ),
    );
  }
}

class _DimensionCard extends StatelessWidget {
  const _DimensionCard({required this.dimension, required this.buckets});

  final AllocationDimension dimension;
  final List<AllocationBucket> buckets;

  @override
  Widget build(BuildContext context) {
    final onlyUnknown = buckets.every((b) => b.bucket == 'unknown' || b.bucket == 'cash');
    return Card(
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(dimensionLabel(dimension), style: Theme.of(context).textTheme.titleMedium),
            if (onlyUnknown) ...[
              const SizedBox(height: 4),
              Text(
                'Атрибут не заполнен у инструментов — разрез пустой, а не нулевой.',
                style: Theme.of(context)
                    .textTheme
                    .bodySmall
                    ?.copyWith(color: Theme.of(context).hintColor),
              ),
            ],
            const SizedBox(height: 12),
            LayoutBuilder(
              builder: (context, constraints) {
                final donut = SizedBox(
                  height: 200,
                  child: _Donut(dimension: dimension, buckets: buckets),
                );
                final legend = _Legend(dimension: dimension, buckets: buckets);
                if (constraints.maxWidth >= 640) {
                  return Row(
                    crossAxisAlignment: CrossAxisAlignment.center,
                    children: [
                      SizedBox(width: 220, child: donut),
                      const SizedBox(width: 24),
                      Expanded(child: legend),
                    ],
                  );
                }
                return Column(children: [donut, const SizedBox(height: 12), legend]);
              },
            ),
          ],
        ),
      ),
    );
  }
}

class _Donut extends StatelessWidget {
  const _Donut({required this.dimension, required this.buckets});

  final AllocationDimension dimension;
  final List<AllocationBucket> buckets;

  @override
  Widget build(BuildContext context) {
    // a negative bucket (a short, an overdrawn balance) has no slice: a pie cannot draw one,
    // and the legend still lists it with its real value
    final positive = buckets.where((b) => _d(b.valueRub) > 0).toList();
    if (positive.isEmpty) {
      return const EmptyState(icon: Icons.donut_large_outlined, message: 'Нечего показать.');
    }
    return PieChart(
      PieChartData(
        sectionsSpace: 2,
        centerSpaceRadius: 48,
        sections: [
          for (var i = 0; i < positive.length; i++)
            PieChartSectionData(
              value: _d(positive[i].valueRub),
              color: _palette[i % _palette.length],
              title: _d(positive[i].weight) >= 0.06
                  ? formatPercent(positive[i].weight, signed: false)
                  : '',
              titleStyle: const TextStyle(
                fontSize: 11,
                fontWeight: FontWeight.w600,
                color: Colors.white,
              ),
              radius: 52,
            ),
        ],
      ),
    );
  }
}

class _Legend extends StatelessWidget {
  const _Legend({required this.dimension, required this.buckets});

  final AllocationDimension dimension;
  final List<AllocationBucket> buckets;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Column(
      children: [
        for (var i = 0; i < buckets.length; i++)
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 4),
            child: Row(
              children: [
                Container(
                  width: 10,
                  height: 10,
                  decoration: BoxDecoration(
                    color: _palette[i % _palette.length],
                    shape: BoxShape.circle,
                  ),
                ),
                const SizedBox(width: 8),
                Expanded(
                  child: Text(
                    bucketLabel(dimension, buckets[i].bucket),
                    overflow: TextOverflow.ellipsis,
                  ),
                ),
                if (buckets[i].holdingCount > 0)
                  Padding(
                    padding: const EdgeInsets.only(right: 8),
                    child: Text('${buckets[i].holdingCount}',
                        style: theme.textTheme.bodySmall?.copyWith(color: theme.hintColor)),
                  ),
                MoneyText(buckets[i].valueRub, currency: 'RUB', style: theme.textTheme.bodyMedium),
                const SizedBox(width: 12),
                SizedBox(
                  width: 56,
                  child: Text(
                    formatPercent(buckets[i].weight, signed: false),
                    textAlign: TextAlign.right,
                    style: theme.textTheme.bodyMedium,
                  ),
                ),
              ],
            ),
          ),
      ],
    );
  }
}