/// Bottom sheet to add or edit a priced line item.
library;

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

import '../models/line_item.dart';
import '../utils/money.dart';

Future<LineItem?> showItemEditSheet(BuildContext context, {LineItem? item}) {
  return showModalBottomSheet<LineItem>(
    context: context,
    isScrollControlled: true,
    showDragHandle: true,
    builder: (context) => ItemEditSheet(item: item),
  );
}

class ItemEditSheet extends StatefulWidget {
  const ItemEditSheet({super.key, this.item});

  final LineItem? item;

  @override
  State<ItemEditSheet> createState() => _ItemEditSheetState();
}

class _ItemEditSheetState extends State<ItemEditSheet> {
  late final TextEditingController _nameController;
  late final TextEditingController _quantityController;
  late final TextEditingController _unitPriceController;
  late final TextEditingController _totalController;
  String? _error;
  bool _syncing = false;

  @override
  void initState() {
    super.initState();
    final item = widget.item;
    final quantity = item?.quantity ?? 1;
    final total = item?.price;
    final unit = item?.unitPrice ??
        (total != null && quantity > 0 ? roundMoney(total / quantity) : null);

    _nameController = TextEditingController(text: item?.name ?? '');
    _quantityController = TextEditingController(text: '$quantity');
    _unitPriceController = TextEditingController(
      text: unit == null ? '' : unit.toStringAsFixed(2),
    );
    _totalController = TextEditingController(
      text: total == null ? '' : total.toStringAsFixed(2),
    );

    _quantityController.addListener(_onQuantityChanged);
    _unitPriceController.addListener(_onUnitPriceChanged);
    _totalController.addListener(_onTotalChanged);
  }

  @override
  void dispose() {
    _quantityController.removeListener(_onQuantityChanged);
    _unitPriceController.removeListener(_onUnitPriceChanged);
    _totalController.removeListener(_onTotalChanged);
    _nameController.dispose();
    _quantityController.dispose();
    _unitPriceController.dispose();
    _totalController.dispose();
    super.dispose();
  }

  int? get _quantity {
    final raw = _quantityController.text.trim();
    if (raw.isEmpty) return null;
    return int.tryParse(raw);
  }

  void _setText(TextEditingController controller, String value) {
    if (controller.text == value) return;
    controller.value = TextEditingValue(
      text: value,
      selection: TextSelection.collapsed(offset: value.length),
    );
  }

  void _onQuantityChanged() {
    if (_syncing) return;
    final quantity = _quantity;
    if (quantity == null || quantity <= 0) {
      setState(() {});
      return;
    }
    final unit = tryParsePrice(_unitPriceController.text);
    final total = tryParsePrice(_totalController.text);
    _syncing = true;
    if (unit != null) {
      _setText(_totalController, roundMoney(quantity * unit).toStringAsFixed(2));
    } else if (total != null) {
      _setText(
        _unitPriceController,
        roundMoney(total / quantity).toStringAsFixed(2),
      );
    }
    _syncing = false;
    setState(() {});
  }

  void _onUnitPriceChanged() {
    if (_syncing) return;
    final quantity = _quantity;
    final unit = tryParsePrice(_unitPriceController.text);
    if (quantity == null || quantity <= 0 || unit == null) {
      setState(() {});
      return;
    }
    _syncing = true;
    _setText(_totalController, roundMoney(quantity * unit).toStringAsFixed(2));
    _syncing = false;
    setState(() {});
  }

  void _onTotalChanged() {
    if (_syncing) return;
    final quantity = _quantity;
    final total = tryParsePrice(_totalController.text);
    if (quantity == null || quantity <= 0 || total == null) {
      setState(() {});
      return;
    }
    _syncing = true;
    _setText(
      _unitPriceController,
      roundMoney(total / quantity).toStringAsFixed(2),
    );
    _syncing = false;
    setState(() {});
  }

  void _save() {
    final name = _nameController.text.trim();
    final quantity = _quantity;
    final unit = tryParsePrice(_unitPriceController.text);
    final total = tryParsePrice(_totalController.text);

    if (name.isEmpty) {
      setState(() => _error = 'Enter a product name.');
      return;
    }
    if (quantity == null || quantity <= 0) {
      setState(() => _error = 'Enter a quantity of at least 1.');
      return;
    }
    if (total == null && unit == null) {
      setState(() => _error = 'Enter a unit price or a total.');
      return;
    }

    final resolvedTotal = total ?? roundMoney(quantity * unit!);
    final resolvedUnit = unit ?? roundMoney(resolvedTotal / quantity);
    final hasMulti = quantity > 1;

    Navigator.of(context).pop(
      LineItem(
        id:
            widget.item?.id ??
            'manual-${DateTime.now().microsecondsSinceEpoch}',
        name: name,
        price: roundMoney(resolvedTotal),
        quantity: hasMulti ? quantity : null,
        unitPrice: hasMulti ? roundMoney(resolvedUnit) : null,
        discount: widget.item?.price == roundMoney(resolvedTotal)
            ? widget.item?.discount ?? 0
            : 0,
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    final bottom = MediaQuery.viewInsetsOf(context).bottom;
    final quantity = _quantity;
    final unit = tryParsePrice(_unitPriceController.text);
    final preview = quantity != null && quantity > 1 && unit != null
        ? '$quantity × ${formatEuro(unit)}'
        : null;

    return Padding(
      padding: EdgeInsets.fromLTRB(16, 0, 16, 16 + bottom),
      child: Column(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Text(
            widget.item == null ? 'Add item' : 'Edit item',
            style: Theme.of(context).textTheme.titleLarge,
          ),
          const SizedBox(height: 16),
          TextField(
            controller: _nameController,
            textCapitalization: TextCapitalization.sentences,
            decoration: const InputDecoration(labelText: 'Product name'),
            autofocus: widget.item == null,
          ),
          const SizedBox(height: 12),
          Row(
            children: [
              SizedBox(
                width: 88,
                child: TextField(
                  controller: _quantityController,
                  keyboardType: TextInputType.number,
                  inputFormatters: [FilteringTextInputFormatter.digitsOnly],
                  decoration: const InputDecoration(labelText: 'Qty'),
                ),
              ),
              const SizedBox(width: 12),
              Expanded(
                child: TextField(
                  controller: _unitPriceController,
                  keyboardType: const TextInputType.numberWithOptions(
                    decimal: true,
                  ),
                  decoration: const InputDecoration(labelText: 'Unit price'),
                ),
              ),
            ],
          ),
          const SizedBox(height: 12),
          TextField(
            controller: _totalController,
            keyboardType: const TextInputType.numberWithOptions(decimal: true),
            decoration: InputDecoration(
              labelText: 'Total price',
              helperText: preview,
            ),
          ),
          if (_error != null) ...[
            const SizedBox(height: 8),
            Text(
              _error!,
              style: TextStyle(color: Theme.of(context).colorScheme.error),
            ),
          ],
          const SizedBox(height: 16),
          FilledButton(onPressed: _save, child: const Text('Save')),
        ],
      ),
    );
  }
}