StreamNameMapper.cs

namespace Core.Events;

public class StreamNameMapper
{
    private static readonly StreamNameMapper Instance = new();

    private readonly ConcurrentDictionary<Type, string> TypeNameMap = new();

    public static void AddCustomMap<TStream>(string mappedStreamName) =>
        AddCustomMap(typeof(TStream), mappedStreamName);

    public static void AddCustomMap(Type streamType, string mappedStreamName)
    {
        Instance.TypeNameMap.AddOrUpdate(streamType, mappedStreamName, (_, _) => mappedStreamName);
    }

    public static string ToStreamPrefix<TStream>() => ToStreamPrefix(typeof(TStream));

    public static string ToStreamPrefix(Type streamType) => Instance.TypeNameMap.GetOrAdd(streamType, _ =>
    {
        var modulePrefix = streamType.Namespace!.Split('.').First();
        return $"{modulePrefix}_{streamType.Name}";
    });

    public static string ToStreamId<TStream>(object aggregateId, object? tenantId = null) =>
        ToStreamId(typeof(TStream), aggregateId);

    /// <summary>
    /// Generates a stream id in the canonical `{category}-{aggregateId}` format.
    /// It can be expanded to the `{module}_{streamType}-{tenantId}_{aggregateId}` format
    /// </summary>
    /// <param name="streamType"></param>
    /// <param name="aggregateId"></param>
    /// <param name="tenantId"></param>
    /// <returns></returns>
    public static string ToStreamId(Type streamType, object aggregateId, object? tenantId = null)
    {
        var tenantPrefix = tenantId != null ? $"{tenantId}_"  : "";
        var streamCategory = ToStreamPrefix(streamType);

        // (Out-of-the box, the category projection treats anything before a `-` separator as the category name)
        // For this reason, we place the "{tenantId}_" bit (if present) on the right hand side of the '-'
        return $"{streamCategory}-{tenantPrefix}{aggregateId}";
    }

}