import 'package:decimal/decimal.dart';

/// Weights travel as shares (`"0.60"` = 60 %) and are edited as percents. The conversion is
/// exact on both sides: `Decimal`, never `double`, so 33,33 % round-trips unchanged and a
/// set that sums to exactly 1 does not fail validation because of binary floating point.

final _hundred = Decimal.fromInt(100);

/// `"0.605"` → `"60,5"`; empty for anything unparseable.
String shareToPercentText(String? share) {
  final d = share == null ? null : Decimal.tryParse(share);
  if (d == null) return '';
  final p = d * _hundred;
  final text = p == p.truncate() ? p.truncate().toString() : p.toString();
  return text.replaceAll('.', ',');
}

/// `"60,5"` → `"0.605"`; null when the text is not a number.
String? percentTextToShare(String text) {
  final normalized = text.trim().replaceAll(',', '.').replaceAll(' ', '');
  if (normalized.isEmpty) return null;
  final d = Decimal.tryParse(normalized);
  if (d == null) return null;
  return (d / _hundred).toDecimal(scaleOnInfinitePrecision: 10).toString();
}

/// `"0.032"` → `"3,20 %"`, signed. Kept local to the rebalance screen because drift is a
/// share, not a return, and the portfolio helper would sign it the same way by accident.
String formatShareAsPercent(String? share, {bool signed = false, int digits = 2}) {
  final d = share == null ? null : Decimal.tryParse(share);
  if (d == null) return '—';
  final p = (d * _hundred).toDouble();
  final sign = signed && p > 0 ? '+' : '';
  return '$sign${p.toStringAsFixed(digits).replaceAll('.', ',')} %';
}