using System.Globalization;
using Avalonia.Data;
using Avalonia.Data.Converters;

namespace ClaudeDo.Ui.Converters;

/// <summary>
/// For <c>NumericUpDown.Value</c> bound to a non-nullable numeric property. The control's Value is
/// <c>decimal?</c> and goes null the moment the text box is empty — which is exactly what happens
/// while the user clears a value to type a new one. Writing that null into an <c>int</c>/<c>decimal</c>
/// target throws <see cref="InvalidCastException"/>, so swallow it and leave the source untouched
/// until a real number arrives.
/// </summary>
public class KeepLastNumberConverter : IValueConverter
{
    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
        => value is null ? null : System.Convert.ToDecimal(value, culture);

    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
    {
        if (value is null) return BindingOperations.DoNothing;
        return System.Convert.ChangeType(value, Nullable.GetUnderlyingType(targetType) ?? targetType, culture);
    }
}