inabox/InABox.Avalonia/Converters/EnumToStringConverter.cs

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

namespace InABox.Avalonia.Converters;

public class EnumToStringConverter : IValueConverter
{
    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
    {
        if (value is null)
            return "";
        
        if (value.GetType().IsEnum)
            return ((Enum)value).ToDescription();
        
        throw new ArgumentException("Convert:Value must be an enum.");
    }
    
    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
    {
        if (value is null)
            return targetType.GetTypeInfo().IsValueType ? Activator.CreateInstance(targetType) : null;
        if (value is EnumDescription _enumDescription)
            return _enumDescription.Value;
        throw new ArgumentException("ConvertBack:EnumDescription must be an enum.");
    }
}

public record EnumDescription
{
    public object Value { get; set; }

    public string Description { get; set; }
    
    public string Help { get; set; }
    
    public override string ToString()
    {
        return Description;
    }
}

public static class EnumUtils
{
    
    public static IEnumerable<EnumDescription> ToDescriptions(Type t)
    {
        if (!t.IsEnum)
            throw new ArgumentException($"{nameof(t)} must be an enum type");
    
        return Enum.GetValues(t).Cast<Enum>().Select(ToDescription).ToList();
    }
    
    public static EnumDescription ToDescription(this Enum value)
    {
        string description;
        string help = null;
        
        var attributes = value.GetType().GetField(value.ToString()).GetCustomAttributes(typeof(DescriptionAttribute), false);
        if (attributes.Any())
        {
            description = (attributes.First() as DescriptionAttribute)?.Description;
        }
        else
        {
            TextInfo ti = CultureInfo.CurrentCulture.TextInfo;
            description = ti.ToTitleCase(ti.ToLower(value.ToString().Replace("_", " ")));
        }
        
        if(description.IndexOf(';') is var index && index != -1)
        {
            help = description.Substring(index + 1);
            description = description.Substring(0, index);
        }

        return new EnumDescription() { Value = value, Description = description, Help = help };
    }

    // public static string GetStringValue(Enum value)
    // {
    //     string output = null;
    //     Type type = value.GetType();
    //     FieldInfo fi = type.GetField(value.ToString());
    //     if (fi.GetCustomAttributes(typeof(StringValue),
    //             false) is StringValue[] { Length: > 0 } attrs)
    //     {
    //         output = attrs[0].Value;
    //     }
    //     return output;
    // }

    public static T? Parse<T>(string input) where T : struct
    {
        if (!typeof(T).IsEnum)
        {
            throw new ArgumentException("Generic Type 'T' must be an Enum.");
        }
        if (string.IsNullOrEmpty(input)) return null;
        if (Enum.GetNames(typeof(T)).Any(
                e => e.Trim().ToUpperInvariant() == input.Trim().ToUpperInvariant()))
        {
            return (T)Enum.Parse(typeof(T), input, true);
        }
        return null;
    }
}