using Microsoft.Extensions.Options;

namespace Marathon.UI.Tests.Support;

/// <summary>
/// Minimal in-memory <see cref="IOptionsMonitor{TOptions}"/> for tests.
/// </summary>
public sealed class TestOptionsMonitor<T> : IOptionsMonitor<T> where T : class, new()
{
    private T _value;
    private readonly List<Action<T, string?>> _listeners = new();

    public TestOptionsMonitor(T initial)
    {
        _value = initial;
    }

    public T CurrentValue => _value;

    public T Get(string? name) => _value;

    public IDisposable OnChange(Action<T, string?> listener)
    {
        _listeners.Add(listener);
        return new Subscription(() => _listeners.Remove(listener));
    }

    public void Set(T next)
    {
        _value = next;
        foreach (var listener in _listeners.ToList())
            listener(next, null);
    }

    private sealed class Subscription : IDisposable
    {
        private readonly Action _dispose;
        public Subscription(Action dispose) { _dispose = dispose; }
        public void Dispose() => _dispose();
    }
}