namespace Prefab.Domain.Common;

/// <summary>
/// Base implementation for aggregate entities that support domain events.
/// </summary>
/// <typeparam name="T">Entity identifier type.</typeparam>
public abstract class Entity<T> : IEntity<T>, IHasDomainEvents
{
    private readonly List<Event> _events = [];

    /// <inheritdoc />
    public T Id { get; set; } = default!;

    /// <inheritdoc />
    public IReadOnlyCollection<Event> Events => _events.AsReadOnly();

    /// <inheritdoc />
    public void AddEvent(Event e) => _events.Add(e);

    /// <inheritdoc />
    public void RemoveEvent(Event e) => _events.Remove(e);

    /// <inheritdoc />
    public void ClearEvents() => _events.Clear();

    /// <summary>
    /// Generates a UUIDv7 identifier using the supplied timestamp, primarily for testing scenarios.
    /// </summary>
    /// <param name="timestamp">The timestamp used to seed the UUID generator.</param>
    /// <exception cref="InvalidOperationException">Thrown when the entity identifier type is not <see cref="Guid"/>.</exception>
    protected void GenerateIdWithTimestamp(DateTime timestamp)
    {
        Id = typeof(T) == typeof(Guid)
            ? (T)(object)Guid.CreateVersion7(timestamp)
            : throw new InvalidOperationException("Cannot generate a UUIDv7 for a non-Guid entity.");
    }
}