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

import '../../core/utils/json.dart';
import '../../core/widgets/async_value_view.dart';
import '../../core/widgets/section_card.dart';
import '../portfolio/labels.dart' show assetClassLabels;
import 'data/rebalance_api.dart';
import 'labels.dart';
import 'providers.dart';
import 'weights.dart';

/// Целевые веса: the editable target set for one dimension.
///
/// The sum of the weights is shown permanently and Save is blocked whenever it differs from
/// 100 % by more than 0,01 pp. The server answers 422 in that case — but a user should see
/// the problem while typing, not after a round trip.
class TargetsTab extends ConsumerStatefulWidget {
  const TargetsTab({super.key});

  @override
  ConsumerState<TargetsTab> createState() => _TargetsTabState();
}

class _TargetsTabState extends ConsumerState<TargetsTab> {
  /// Local draft. Seeded from the server set and reseeded whenever the portfolio or the
  /// dimension changes — editing one dimension must never leak into another.
  List<TargetWeight>? _draft;
  String? _seededFor;
  bool _saving = false;
  bool _dirty = false;

  void _seed(TargetSet set, String key) {
    if (_seededFor == key) return;
    _seededFor = key;
    _draft = [...set.targets];
    _dirty = false;
  }

  Decimal get _sum => sumDecimals((_draft ?? const []).map((t) => t.targetWeight));

  bool get _sumIsValid => (_sum - Decimal.one).abs() <= Decimal.parse('0.0001');

  Future<void> _save() async {
    final portfolioId = ref.read(selectedPortfolioProvider);
    final dimension = ref.read(targetDimensionProvider);
    final draft = _draft;
    if (portfolioId == null || draft == null) return;

    setState(() => _saving = true);
    try {
      await ref
          .read(rebalanceApiProvider)
          .putTargets(portfolioId, TargetSet(dimension: dimension, targets: draft));
      if (!mounted) return;
      _dirty = false;
      _seededFor = null; // refetch reseeds the draft from the saved set
      invalidateRebalanceProviders(ref);
      ScaffoldMessenger.of(context)
          .showSnackBar(const SnackBar(content: Text('Целевые веса сохранены')));
    } catch (e) {
      if (!mounted) return;
      ScaffoldMessenger.of(context)
          .showSnackBar(SnackBar(content: Text(apiErrorMessage(e))));
    } finally {
      if (mounted) setState(() => _saving = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final portfolioId = ref.watch(selectedPortfolioProvider);
    final dimension = ref.watch(targetDimensionProvider);
    final targets = ref.watch(targetsProvider);

    return AsyncValueView(
      value: targets,
      onRetry: () => ref.invalidate(targetsProvider),
      data: (set) {
        _seed(set, '$portfolioId/$dimension');
        final draft = _draft ?? const <TargetWeight>[];
        return ListView(
          padding: const EdgeInsets.fromLTRB(16, 16, 16, 88),
          children: [
            _SumBanner(sum: _sum, valid: _sumIsValid, serverSum: set.weightsSum),
            const SizedBox(height: 12),
            SectionCard(
              title: 'Целевые веса',
              subtitle: 'Вес — доля портфеля; допуск (band) — ширина коридора, '
                  'внутри которого сделки не предлагаются.',
              child: Column(
                children: [
                  for (var i = 0; i < draft.length; i++)
                    _TargetRow(
                      key: ValueKey('${_seededFor}_$i'),
                      dimension: dimension,
                      target: draft[i],
                      onChanged: (t) => setState(() {
                        _draft![i] = t;
                        _dirty = true;
                      }),
                      onRemove: () => setState(() {
                        _draft!.removeAt(i);
                        _dirty = true;
                      }),
                    ),
                  if (draft.isEmpty)
                    const Padding(
                      padding: EdgeInsets.symmetric(vertical: 16),
                      child: Text('Целевые веса ещё не заданы.'),
                    ),
                  const SizedBox(height: 8),
                  Align(
                    alignment: Alignment.centerLeft,
                    child: TextButton.icon(
                      onPressed: () => setState(() {
                        _draft = [
                          ...draft,
                          const TargetWeight(bucket: '', targetWeight: '0', band: '0.05'),
                        ];
                        _dirty = true;
                      }),
                      icon: const Icon(Icons.add),
                      label: const Text('Добавить группу'),
                    ),
                  ),
                ],
              ),
            ),
            const SizedBox(height: 16),
            Row(
              children: [
                FilledButton.icon(
                  onPressed: _saving || !_sumIsValid || draft.any((t) => t.bucket.isEmpty)
                      ? null
                      : _save,
                  icon: _saving
                      ? const SizedBox(
                          width: 16, height: 16, child: CircularProgressIndicator(strokeWidth: 2))
                      : const Icon(Icons.save_outlined),
                  label: const Text('Сохранить'),
                ),
                const SizedBox(width: 12),
                if (_dirty)
                  TextButton(
                    onPressed: () => setState(() {
                      _seededFor = null;
                      _seed(set, '$portfolioId/$dimension');
                    }),
                    child: const Text('Отменить изменения'),
                  ),
              ],
            ),
            const SizedBox(height: 8),
            if (!_sumIsValid)
              Text(
                'Сохранение заблокировано: сумма весов должна быть ровно 100 %. '
                'Сервер не нормализует веса — сумма 90 % означает, что 10 % портфеля '
                'не отнесены ни к одной группе, а не что доли надо растянуть.',
                style: Theme.of(context).textTheme.bodySmall,
              )
            else if (draft.any((t) => t.bucket.isEmpty))
              Text(
                'У одной из групп пустое имя — сохранить нельзя.',
                style: Theme.of(context).textTheme.bodySmall,
              ),
          ],
        );
      },
    );
  }
}

class _SumBanner extends StatelessWidget {
  const _SumBanner({required this.sum, required this.valid, this.serverSum});

  final Decimal sum;
  final bool valid;
  final String? serverSum;

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;
    return Card(
      color: valid ? scheme.secondaryContainer : scheme.errorContainer,
      child: ListTile(
        leading: Icon(valid ? Icons.check_circle_outline : Icons.error_outline),
        title: Text('Сумма весов: ${formatShareAsPercent(sum.toString())}'),
        subtitle: Text(
          valid
              ? 'Набор можно сохранить.'
              : 'Нужно ровно 100 %. Разница: '
                  '${formatShareAsPercent((sum - Decimal.one).toString(), signed: true)}',
        ),
        trailing: serverSum == null
            ? null
            : Tooltip(
                message: 'Последняя сумма, сохранённая на сервере',
                child: Text(formatShareAsPercent(serverSum)),
              ),
      ),
    );
  }
}

class _TargetRow extends StatefulWidget {
  const _TargetRow({
    required this.dimension,
    required this.target,
    required this.onChanged,
    required this.onRemove,
    super.key,
  });

  final String dimension;
  final TargetWeight target;
  final ValueChanged<TargetWeight> onChanged;
  final VoidCallback onRemove;

  @override
  State<_TargetRow> createState() => _TargetRowState();
}

class _TargetRowState extends State<_TargetRow> {
  late final TextEditingController _weight =
      TextEditingController(text: shareToPercentText(widget.target.targetWeight));
  late final TextEditingController _band =
      TextEditingController(text: shareToPercentText(widget.target.band));
  late final TextEditingController _bucket =
      TextEditingController(text: widget.target.bucket);

  @override
  void dispose() {
    _weight.dispose();
    _band.dispose();
    _bucket.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    // The known asset classes are offered as a list; every other dimension (sector, country,
    // currency) has an open set of buckets that only the data knows, so those stay free text.
    final knownBuckets = widget.dimension == 'asset_class'
        ? [...assetClassLabels.keys, 'cash']
        : const <String>[];

    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 6),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Expanded(
            flex: 3,
            child: knownBuckets.isEmpty
                ? TextField(
                    controller: _bucket,
                    decoration: const InputDecoration(labelText: 'Группа', isDense: true),
                    onChanged: (v) => widget.onChanged(widget.target.copyWith(bucket: v)),
                  )
                : DropdownButtonFormField<String>(
                    initialValue:
                        knownBuckets.contains(widget.target.bucket) ? widget.target.bucket : null,
                    isExpanded: true,
                    decoration: const InputDecoration(labelText: 'Группа', isDense: true),
                    items: [
                      for (final b in knownBuckets)
                        DropdownMenuItem(value: b, child: Text(bucketLabelForKey('asset_class', b))),
                    ],
                    onChanged: (v) =>
                        widget.onChanged(widget.target.copyWith(bucket: v ?? '')),
                  ),
          ),
          const SizedBox(width: 12),
          Expanded(
            flex: 2,
            child: TextField(
              controller: _weight,
              keyboardType: const TextInputType.numberWithOptions(decimal: true),
              decoration: const InputDecoration(labelText: 'Вес, %', isDense: true),
              onChanged: (v) {
                final share = percentTextToShare(v);
                widget.onChanged(widget.target.copyWith(targetWeight: share ?? '0'));
              },
            ),
          ),
          const SizedBox(width: 12),
          Expanded(
            flex: 2,
            child: TextField(
              controller: _band,
              keyboardType: const TextInputType.numberWithOptions(decimal: true),
              decoration: const InputDecoration(labelText: 'Допуск, %', isDense: true),
              onChanged: (v) =>
                  widget.onChanged(widget.target.copyWith(band: percentTextToShare(v))),
            ),
          ),
          IconButton(
            tooltip: 'Удалить группу',
            onPressed: widget.onRemove,
            icon: const Icon(Icons.delete_outline),
          ),
        ],
      ),
    );
  }
}