Hyperbar/Hyperbar.Widget.MediaController.Windows/MediaControllerService.cs

using Microsoft.Extensions.Hosting;
using Windows.Media.Control;

namespace Hyperbar.Widget.MediaController.Windows;

public class MediaControllerService(IMediator mediator,
    IFactory<GlobalSystemMediaTransportControlsSession, MediaController> factory) :
    IHostedService
{
    private readonly AsyncLock asyncLock = new();
    private readonly List<KeyValuePair<GlobalSystemMediaTransportControlsSession, MediaController>> cache = [];
    private GlobalSystemMediaTransportControlsSessionManager? mediaTransportControlsSessionManager;

    public async Task StartAsync(CancellationToken cancellationToken)
    {
        mediaTransportControlsSessionManager = await GlobalSystemMediaTransportControlsSessionManager.RequestAsync();
        mediaTransportControlsSessionManager.SessionsChanged += OnSessionsChanged;

        IReadOnlyList<GlobalSystemMediaTransportControlsSession> sessions =
            mediaTransportControlsSessionManager.GetSessions();

        foreach (GlobalSystemMediaTransportControlsSession session in sessions)
        {
            await InitializeSessionAsync(session);
        }
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
       return Task.CompletedTask;
    }

    private async Task InitializeSessionAsync(GlobalSystemMediaTransportControlsSession session)
    {
        if (factory.Create(session) is MediaController mediaController)
        {
            await mediator.PublishAsync(new Create<MediaController>(mediaController));
            cache.Add(new KeyValuePair<GlobalSystemMediaTransportControlsSession, MediaController>(session, 
                mediaController));
        }
    }

    private async void OnSessionsChanged(GlobalSystemMediaTransportControlsSessionManager sender,
        SessionsChangedEventArgs args)
    {
        IReadOnlyList<GlobalSystemMediaTransportControlsSession> sessions =
        sender.GetSessions();

        using (await asyncLock)
        {
            foreach (KeyValuePair<GlobalSystemMediaTransportControlsSession, MediaController> session in
                cache.ToList())
            {
                if (!sessions.Any(x => x.SourceAppUserModelId == session.Key.SourceAppUserModelId))
                {
                    await mediator.PublishAsync(new Remove<MediaController>(session.Value));
                    cache.Remove(session);
                }
            }
        }

        using (await asyncLock)
        {
            foreach (GlobalSystemMediaTransportControlsSession session in sessions)
            {
                if (!cache.Any(x => x.Key.SourceAppUserModelId == session.SourceAppUserModelId))
                {
                    await InitializeSessionAsync(session);
                }
            }
        }
    }
}