classlib/ExpenseTracker.Domain/Enums/Enumeration.cs

namespace ExpenseTracker.Domain.Enums;

using System.Reflection;

public abstract class Enumeration<TEnum> : IEquatable<Enumeration<TEnum>>
    where TEnum : Enumeration<TEnum>
{
    public static Dictionary<int, TEnum> Enumerations { get; private set; } = CreateEnumerations();

    protected Enumeration(int value, string name)
    {
        Value = value;
        Name = name;
    }

    public int Value { get; protected init; }

    public string Name { get; protected init; } = string.Empty;

    public static TEnum? FromValue(int value)
    {
        return 
            Enumerations.TryGetValue(value, out TEnum? enumeration) ?
            enumeration :
            default;
    }

    public static TEnum? FromName(string name)
    {
        return Enumerations.Values.SingleOrDefault(v => v.Name == name);
    }

    public bool Equals(Enumeration<TEnum>? other)
    {
        if (other is null)
        {
            return false;
        }

        return
            GetType() == other.GetType() &&
            Value == other.Value;
    }

    public override bool Equals(object? obj)
    {
        return
            obj is Enumeration<TEnum> other &&
            Equals(other);
    }

    public override int GetHashCode()
    {
        return Value.GetHashCode();
    }

    public override string ToString()
    {
        return Name;
    }

    private static Dictionary<int, TEnum> CreateEnumerations()
    {
        var enumerationType = typeof(TEnum);

        var fieldsForType = enumerationType
            .GetFields(
                BindingFlags.Public |
                BindingFlags.Static |
                BindingFlags.FlattenHierarchy)
            .Where(fieldInfo =>
                enumerationType.IsAssignableFrom(fieldInfo.FieldType))
            .Select(fieldInfo =>
                (TEnum) fieldInfo.GetValue(default)!);

        return fieldsForType.ToDictionary(x => x.Value);
    }
}