/// Create / edit look-ahead recurring templates.
library;

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:provider/provider.dart';

import '../models/bank.dart';
import '../models/transaction_meta.dart';
import '../providers/bank_provider.dart';
import '../providers/tx_meta_provider.dart';
import '../utils/helpers.dart';
import '../utils/look_ahead.dart';

Future<void> showCreateRecurringTemplateSheet(BuildContext context) {
  return showModalBottomSheet<void>(
    context: context,
    isScrollControlled: true,
    useSafeArea: true,
    showDragHandle: true,
    builder: (context) => const _RecurringTemplateSheet(),
  );
}

Future<void> showEditRecurringTemplateSheet(
  BuildContext context, {
  required RecurringTemplate template,
}) {
  return showModalBottomSheet<void>(
    context: context,
    isScrollControlled: true,
    useSafeArea: true,
    showDragHandle: true,
    builder: (context) => _RecurringTemplateSheet(existing: template),
  );
}

class _RecurringTemplateSheet extends StatefulWidget {
  const _RecurringTemplateSheet({this.existing});

  final RecurringTemplate? existing;

  @override
  State<_RecurringTemplateSheet> createState() =>
      _RecurringTemplateSheetState();
}

class _RecurringTemplateSheetState extends State<_RecurringTemplateSheet> {
  late RecurringTemplateSource _source;
  late RecurringAmountRule _rule;
  late final TextEditingController _nameController;
  late final TextEditingController _dayController;
  late final TextEditingController _avgController;
  BankTransaction? _pickedTx;
  String? _labelId;
  String _currency = 'EUR';

  @override
  void initState() {
    super.initState();
    final existing = widget.existing;
    _source = existing?.source ?? RecurringTemplateSource.transaction;
    _rule = existing?.amountRule ?? RecurringAmountRule.lastValue;
    _nameController = TextEditingController(text: existing?.name ?? '');
    _dayController = TextEditingController(
      text: '${existing?.dayOfMonth ?? 1}',
    );
    _avgController = TextEditingController(
      text: '${existing?.avgCount ?? 5}',
    );
    _labelId = existing?.labelId;
    _currency = existing?.currency ?? 'EUR';

    if (existing?.sourceTxId != null) {
      final txs = context.read<BankController>().transactions;
      for (final tx in txs) {
        if (tx.id == existing!.sourceTxId) {
          _pickedTx = tx;
          break;
        }
      }
    }
  }

  @override
  void dispose() {
    _nameController.dispose();
    _dayController.dispose();
    _avgController.dispose();
    super.dispose();
  }

  int get _day {
    final v = int.tryParse(_dayController.text.trim()) ?? 1;
    return v.clamp(1, 28);
  }

  int get _avg {
    final v = int.tryParse(_avgController.text.trim()) ?? 5;
    return v.clamp(1, 36);
  }

  Future<void> _pickTransaction() async {
    final bank = context.read<BankController>();
    final picked = await showModalBottomSheet<BankTransaction>(
      context: context,
      isScrollControlled: true,
      useSafeArea: true,
      showDragHandle: true,
      builder: (context) => _TransactionPickerSheet(
        transactions: bank.transactions,
      ),
    );
    if (picked == null || !mounted) return;
    setState(() {
      _pickedTx = picked;
      _currency = picked.currency;
      _source = RecurringTemplateSource.transaction;
      if (_nameController.text.trim().isEmpty || widget.existing == null) {
        _nameController.text = picked.description;
      }
      _dayController.text =
          '${(DateTime.tryParse(picked.date)?.day ?? 1).clamp(1, 28)}';
      if (_rule == RecurringAmountRule.labelAvgMonths) {
        _rule = RecurringAmountRule.lastValue;
      }
    });
  }

  Future<void> _pickLabel() async {
    final meta = context.read<TxMetaController>();
    final labels = [...meta.allLabels]
      ..sort((a, b) => a.name.toLowerCase().compareTo(b.name.toLowerCase()));
    final picked = await showModalBottomSheet<TxLabel>(
      context: context,
      isScrollControlled: true,
      useSafeArea: true,
      showDragHandle: true,
      builder: (context) => _LabelPickerSheet(labels: labels),
    );
    if (picked == null || !mounted) return;
    setState(() {
      _labelId = picked.id;
      _source = RecurringTemplateSource.label;
      _rule = RecurringAmountRule.labelAvgMonths;
      if (_nameController.text.trim().isEmpty || widget.existing == null) {
        _nameController.text = picked.name;
      }
      if (_dayController.text.trim().isEmpty) {
        _dayController.text = '1';
      }
    });
  }

  void _save() {
    final name = _nameController.text.trim();
    if (name.isEmpty) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Enter a name')),
      );
      return;
    }

    if (_source == RecurringTemplateSource.transaction && _pickedTx == null) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Pick a transaction')),
      );
      return;
    }
    if ((_source == RecurringTemplateSource.label ||
            _rule == RecurringAmountRule.labelAvgMonths) &&
        (_labelId == null || _labelId!.isEmpty)) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Pick a label')),
      );
      return;
    }

    final existing = widget.existing;
    final id = existing?.id.isNotEmpty == true
        ? existing!.id
        : 'rt_${DateTime.now().microsecondsSinceEpoch.toRadixString(16)}';

    final tpl = RecurringTemplate(
      id: id,
      name: name,
      dayOfMonth: _day,
      currency: _currency,
      source: _source,
      amountRule: _source == RecurringTemplateSource.label
          ? RecurringAmountRule.labelAvgMonths
          : _rule,
      merchantKey: _pickedTx?.merchantKey ?? existing?.merchantKey ?? '',
      sourceTxId: _source == RecurringTemplateSource.transaction
          ? _pickedTx?.id
          : null,
      labelId: (_source == RecurringTemplateSource.label ||
              _rule == RecurringAmountRule.labelAvgMonths)
          ? _labelId
          : null,
      avgCount: _avg,
      autoFromRecurring: existing?.autoFromRecurring ?? false,
    );
    // Pop first so the sheet does not rebuild against the notify.
    final meta = context.read<TxMetaController>();
    Navigator.pop(context);
    meta.upsertRecurringTemplate(tpl);
  }

  void _delete() {
    final existing = widget.existing;
    if (existing == null) return;
    final meta = context.read<TxMetaController>();
    Navigator.pop(context);
    meta.removeRecurringTemplate(existing.id);
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colors = theme.colorScheme;
    final meta = context.read<TxMetaController>();
    final bank = context.read<BankController>();
    final media = MediaQuery.of(context);
    final label = meta.labelById(_labelId);

    final preview = resolveRecurringAmount(
      template: RecurringTemplate(
        id: 'preview',
        name: _nameController.text,
        dayOfMonth: _day,
        currency: _currency,
        source: _source,
        amountRule: _source == RecurringTemplateSource.label
            ? RecurringAmountRule.labelAvgMonths
            : _rule,
        merchantKey: _pickedTx?.merchantKey ?? '',
        sourceTxId: _pickedTx?.id,
        labelId: _labelId,
        avgCount: _avg,
      ),
      transactions: bank.transactions,
      isInternalTransfer: (tx) => meta.metaFor(tx).internalTransfer,
      labelIdsFor: meta.labelIdsFor,
    );

    return Padding(
      padding: EdgeInsets.only(bottom: media.viewInsets.bottom),
      child: SingleChildScrollView(
        padding: const EdgeInsets.fromLTRB(24, 4, 24, 24),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Text(
              widget.existing == null ? 'New recurring template' : 'Edit template',
              style: theme.textTheme.titleLarge,
            ),
            const SizedBox(height: 16),
            TextField(
              controller: _nameController,
              decoration: const InputDecoration(
                labelText: 'Name',
                isDense: true,
              ),
            ),
            const SizedBox(height: 12),
            TextField(
              controller: _dayController,
              keyboardType: TextInputType.number,
              inputFormatters: [FilteringTextInputFormatter.digitsOnly],
              decoration: const InputDecoration(
                labelText: 'Day of month (1–28)',
                isDense: true,
              ),
            ),
            const SizedBox(height: 16),
            Text('Based on', style: theme.textTheme.titleSmall),
            const SizedBox(height: 8),
            SegmentedButton<RecurringTemplateSource>(
              segments: const [
                ButtonSegment(
                  value: RecurringTemplateSource.transaction,
                  label: Text('Transaction'),
                  icon: Icon(Icons.receipt_long, size: 18),
                ),
                ButtonSegment(
                  value: RecurringTemplateSource.label,
                  label: Text('Label'),
                  icon: Icon(Icons.label_outline, size: 18),
                ),
              ],
              selected: {_source},
              onSelectionChanged: (next) {
                setState(() {
                  _source = next.first;
                  if (_source == RecurringTemplateSource.label) {
                    _rule = RecurringAmountRule.labelAvgMonths;
                  } else if (_rule == RecurringAmountRule.labelAvgMonths) {
                    _rule = RecurringAmountRule.lastValue;
                  }
                });
              },
            ),
            const SizedBox(height: 12),
            if (_source == RecurringTemplateSource.transaction) ...[
              OutlinedButton.icon(
                onPressed: _pickTransaction,
                icon: const Icon(Icons.search),
                label: Text(
                  _pickedTx == null
                      ? 'Pick transaction'
                      : _pickedTx!.description,
                  maxLines: 1,
                  overflow: TextOverflow.ellipsis,
                ),
              ),
              const SizedBox(height: 12),
              Text('Amount', style: theme.textTheme.titleSmall),
              const SizedBox(height: 8),
              Wrap(
                spacing: 8,
                runSpacing: 8,
                children: [
                  ChoiceChip(
                    label: const Text('Last value'),
                    selected: _rule == RecurringAmountRule.lastValue,
                    onSelected: (_) => setState(
                      () => _rule = RecurringAmountRule.lastValue,
                    ),
                  ),
                  ChoiceChip(
                    label: const Text('Avg last X matching'),
                    selected: _rule == RecurringAmountRule.avgLastTxs,
                    onSelected: (_) => setState(
                      () => _rule = RecurringAmountRule.avgLastTxs,
                    ),
                  ),
                  ChoiceChip(
                    label: const Text('Label avg'),
                    selected: _rule == RecurringAmountRule.labelAvgMonths,
                    onSelected: (_) => setState(
                      () => _rule = RecurringAmountRule.labelAvgMonths,
                    ),
                  ),
                ],
              ),
              if (_rule == RecurringAmountRule.avgLastTxs) ...[
                const SizedBox(height: 12),
                TextField(
                  controller: _avgController,
                  keyboardType: TextInputType.number,
                  inputFormatters: [FilteringTextInputFormatter.digitsOnly],
                  decoration: const InputDecoration(
                    labelText: 'Number of matching transactions',
                    helperText:
                        'Matches use the same merchant pattern and income/expense as the picked tx',
                    isDense: true,
                  ),
                  onChanged: (_) => setState(() {}),
                ),
              ],
              if (_rule == RecurringAmountRule.labelAvgMonths) ...[
                const SizedBox(height: 12),
                OutlinedButton.icon(
                  onPressed: _pickLabel,
                  icon: Icon(
                    label?.icon ?? Icons.label_outline,
                    color: label?.color,
                  ),
                  label: Text(label?.name ?? 'Pick label'),
                ),
                const SizedBox(height: 12),
                TextField(
                  controller: _avgController,
                  keyboardType: TextInputType.number,
                  inputFormatters: [FilteringTextInputFormatter.digitsOnly],
                  decoration: const InputDecoration(
                    labelText: 'Previous months',
                    isDense: true,
                  ),
                  onChanged: (_) => setState(() {}),
                ),
              ],
            ] else ...[
              OutlinedButton.icon(
                onPressed: _pickLabel,
                icon: Icon(
                  label?.icon ?? Icons.label_outline,
                  color: label?.color,
                ),
                label: Text(label?.name ?? 'Pick label'),
              ),
              const SizedBox(height: 12),
              TextField(
                controller: _avgController,
                keyboardType: TextInputType.number,
                inputFormatters: [FilteringTextInputFormatter.digitsOnly],
                decoration: const InputDecoration(
                  labelText: 'Previous months to average',
                  isDense: true,
                ),
                onChanged: (_) => setState(() {}),
              ),
            ],
            const SizedBox(height: 16),
            Text(
              'Preview: ${formatMoney(preview, _currency)}',
              style: theme.textTheme.bodyMedium?.copyWith(
                color: colors.onSurfaceVariant,
              ),
            ),
            const SizedBox(height: 20),
            FilledButton(
              onPressed: _save,
              child: Text(widget.existing == null ? 'Create' : 'Save'),
            ),
            if (widget.existing != null)
              TextButton(
                onPressed: _delete,
                child: Text(
                  'Delete',
                  style: TextStyle(color: colors.error),
                ),
              ),
            TextButton(
              onPressed: () => Navigator.pop(context),
              child: const Text('Cancel'),
            ),
          ],
        ),
      ),
    );
  }
}

class _TransactionPickerSheet extends StatefulWidget {
  const _TransactionPickerSheet({required this.transactions});

  final List<BankTransaction> transactions;

  @override
  State<_TransactionPickerSheet> createState() =>
      _TransactionPickerSheetState();
}

class _TransactionPickerSheetState extends State<_TransactionPickerSheet> {
  final _search = TextEditingController();

  @override
  void dispose() {
    _search.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final needle = _search.text.trim().toLowerCase();
    final txs = [
      for (final tx in widget.transactions)
        if (needle.isEmpty ||
            tx.description.toLowerCase().contains(needle) ||
            tx.merchantKey.contains(needle))
          tx,
    ].take(80).toList(growable: false);

    return SizedBox(
      height: MediaQuery.of(context).size.height * 0.75,
      child: Column(
        children: [
          Padding(
            padding: const EdgeInsets.fromLTRB(16, 0, 16, 8),
            child: TextField(
              controller: _search,
              decoration: const InputDecoration(
                hintText: 'Search transactions',
                prefixIcon: Icon(Icons.search),
                isDense: true,
              ),
              onChanged: (_) => setState(() {}),
            ),
          ),
          Expanded(
            child: ListView.separated(
              itemCount: txs.length,
              separatorBuilder: (_, _) => const Divider(height: 1),
              itemBuilder: (context, index) {
                final tx = txs[index];
                return ListTile(
                  title: Text(
                    tx.description,
                    maxLines: 1,
                    overflow: TextOverflow.ellipsis,
                  ),
                  subtitle: Text(
                    '${formatIsoDate(tx.date)} · ${formatMoney(tx.amount, tx.currency)}',
                  ),
                  onTap: () => Navigator.pop(context, tx),
                );
              },
            ),
          ),
        ],
      ),
    );
  }
}

class _LabelPickerSheet extends StatelessWidget {
  const _LabelPickerSheet({required this.labels});

  final List<TxLabel> labels;

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: MediaQuery.of(context).size.height * 0.6,
      child: ListView.separated(
        padding: const EdgeInsets.only(bottom: 16),
        itemCount: labels.length,
        separatorBuilder: (_, _) => const Divider(height: 1, indent: 56),
        itemBuilder: (context, index) {
          final label = labels[index];
          return ListTile(
            leading: Icon(label.icon, color: label.color),
            title: Text(label.name),
            onTap: () => Navigator.pop(context, label),
          );
        },
      ),
    );
  }
}