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

import 'package:intl/intl.dart';

import '../generated/i18n/app_localizations.dart';

/// Birthday entry with a canonical date string at the profile boundary.
class BirthField extends StatefulWidget {
  const BirthField({
    super.key,
    required this.value,
    required this.onChanged,
    this.enabled = true,
  });

  final String value;
  final ValueChanged<String> onChanged;
  final bool enabled;

  @override
  State<BirthField> createState() => _BirthFieldState();
}

class _BirthFieldState extends State<BirthField> {
  final _day = TextEditingController();
  final _year = TextEditingController();
  final _monthField = GlobalKey<FormFieldState<int>>();
  int? _month;
  late String _emitted;

  @override
  void initState() {
    super.initState();
    _readValue();
  }

  @override
  void didUpdateWidget(BirthField oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.value != _emitted) {
      _readValue();
      _monthField.currentState?.didChange(_month);
    }
  }

  void _readValue() {
    _emitted = widget.value;
    final parts = RegExp(r'^(\d{4})-(\d{2})-(\d{2})$').firstMatch(widget.value);
    _year.text = parts?.group(1) ?? '';
    final month = int.tryParse(parts?.group(2) ?? '');
    _month = month != null && month >= 1 && month <= 12 ? month : null;
    _day.text = parts?.group(3) ?? '';
  }

  DateTime? get _date {
    final day = int.tryParse(_day.text);
    final year = int.tryParse(_year.text);
    if (day == null ||
        year == null ||
        year < 1 ||
        _year.text.length != 4 ||
        _month == null) {
      return null;
    }
    final date = DateTime(year, _month!, day);
    return date.year == year && date.month == _month && date.day == day
        ? date
        : null;
  }

  bool _future(DateTime date) =>
      date.isAfter(DateUtils.dateOnly(DateTime.now()));

  void _change() {
    setState(() {});
    final date = _date;
    _emitted = date == null || _future(date)
        ? ''
        : '${_year.text}-${_month.toString().padLeft(2, '0')}-'
              '${_day.text.padLeft(2, '0')}';
    widget.onChanged(_emitted);
  }

  @override
  void dispose() {
    _day.dispose();
    _year.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final l = AppLocalizations.of(context)!;
    final date = _date;
    final complete =
        _day.text.isNotEmpty && _month != null && _year.text.length == 4;
    final error = !complete
        ? null
        : date == null
        ? l.kycBirthInvalid
        : _future(date)
        ? l.kycBirthFuture
        : null;
    final months = DateFormat.MMMM(Localizations.localeOf(context).toString());
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        Text(l.kycBirth, style: Theme.of(context).textTheme.labelLarge),
        const SizedBox(height: 8),
        LayoutBuilder(
          builder: (context, constraints) {
            final day = _number(
              key: 'birth-day',
              controller: _day,
              label: l.kycBirthDay,
              length: 2,
              autofill: AutofillHints.birthdayDay,
            );
            final month = DropdownButtonFormField<int>(
              key: _monthField,
              initialValue: _month,
              isExpanded: true,
              decoration: InputDecoration(labelText: l.kycBirthMonth),
              items: [
                for (var month = 1; month <= 12; month++)
                  DropdownMenuItem(
                    value: month,
                    child: Text(months.format(DateTime(2000, month))),
                  ),
              ],
              onChanged: !widget.enabled
                  ? null
                  : (value) {
                      _month = value;
                      _change();
                    },
            );
            final year = _number(
              key: 'birth-year',
              controller: _year,
              label: l.kycBirthYear,
              length: 4,
              autofill: AutofillHints.birthdayYear,
            );
            final scale = MediaQuery.textScalerOf(context).scale(16) / 16;
            if (constraints.maxWidth < 400 * scale) {
              return Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  day,
                  const SizedBox(height: 16),
                  month,
                  const SizedBox(height: 16),
                  year,
                ],
              );
            }
            return Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Expanded(flex: 2, child: day),
                const SizedBox(width: 12),
                Expanded(flex: 4, child: month),
                const SizedBox(width: 12),
                Expanded(flex: 3, child: year),
              ],
            );
          },
        ),
        if (error != null)
          Padding(
            padding: const EdgeInsets.only(top: 8),
            child: Semantics(
              liveRegion: true,
              child: Text(
                error,
                style: TextStyle(color: Theme.of(context).colorScheme.error),
              ),
            ),
          ),
      ],
    );
  }

  Widget _number({
    required String key,
    required TextEditingController controller,
    required String label,
    required int length,
    required String autofill,
  }) => TextFormField(
    key: ValueKey(key),
    controller: controller,
    enabled: widget.enabled,
    keyboardType: TextInputType.number,
    textInputAction: TextInputAction.next,
    autofillHints: [autofill],
    inputFormatters: [
      FilteringTextInputFormatter.digitsOnly,
      LengthLimitingTextInputFormatter(length),
    ],
    decoration: InputDecoration(labelText: label),
    onChanged: (_) => _change(),
  );
}