av-parser/tests/AvParser.UI.Tests/Fakes/FakeSettingsService.cs

using AvParser.Core.Settings;
using ReactiveUI.Primitives.Signals;

namespace AvParser.UI.Tests.Fakes;

/// <summary>In-memory settings, so tests never touch the developer's real profile.</summary>
internal sealed class FakeSettingsService(AppSettings? initial = null) : ISettingsService, IDisposable
{
    private readonly BehaviorSignal<AppSettings> _current = new(initial ?? new AppSettings());

    public AppSettings Current => _current.Value;

    public IObservable<AppSettings> Changes => _current;

    /// <summary>How many times <see cref="FlushAsync"/> was called.</summary>
    public int FlushCount { get; private set; }

    /// <summary>Every value the settings have taken, oldest first.</summary>
    public List<AppSettings> History { get; } = [];

    public void Update(Func<AppSettings, AppSettings> mutate)
    {
        var next = mutate(_current.Value);
        History.Add(next);
        _current.OnNext(next);
    }

    public Task FlushAsync(CancellationToken cancellationToken = default)
    {
        FlushCount++;
        return Task.CompletedTask;
    }

    public void Dispose() => _current.Dispose();
}