ersatztv/ErsatzTV.Infrastructure/Locking/EntityLocker.cs

using System.Collections.Concurrent;
using ErsatzTV.Core.Interfaces.Locking;
using ErsatzTV.Core.Notifications;
using MediatR;
using Microsoft.Extensions.Logging;

namespace ErsatzTV.Infrastructure.Locking;

public class EntityLocker(IMediator mediator, ILogger<EntityLocker> logger) : IEntityLocker
{
    private readonly ConcurrentDictionary<int, byte> _lockedLibraries = new();
    private readonly ConcurrentDictionary<int, byte> _lockedPlayouts = new();
    private readonly ConcurrentDictionary<Type, byte> _lockedRemoteMediaSourceTypes = new();

    // 0 = unlocked, 1 = locked. Mutated only via Interlocked.CompareExchange so the caller that wins
    // the 0 -> 1 transition is the sole owner and the only one that fires the change event
    // (see docs/decisions.md 2026-07-11, issue #231).
    private int _embyCollections;
    private int _jellyfinCollections;
    private int _plex;
    private int _plexCollections;
    private int _trakt;
    private int _troubleshootingPlayback;

    public event EventHandler OnLibraryChanged;
    public event EventHandler OnPlexChanged;
    public event EventHandler<Type> OnRemoteMediaSourceChanged;
    public event EventHandler OnTraktChanged;
    public event EventHandler OnEmbyCollectionsChanged;
    public event EventHandler OnJellyfinCollectionsChanged;
    public event EventHandler OnPlexCollectionsChanged;
    public event EventHandler OnTroubleshootingPlaybackChanged;

    public bool LockLibrary(int libraryId)
    {
        if (_lockedLibraries.TryAdd(libraryId, 0))
        {
            OnLibraryChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        return false;
    }

    public bool UnlockLibrary(int libraryId)
    {
        if (_lockedLibraries.TryRemove(libraryId, out byte _))
        {
            OnLibraryChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        logger.LogWarning(
            "UnlockLibrary called for library {LibraryId} that was not locked (double-release or non-owner release)",
            libraryId);
        return false;
    }

    public bool IsLibraryLocked(int libraryId) =>
        _lockedLibraries.ContainsKey(libraryId);

    public bool LockPlex()
    {
        if (Interlocked.CompareExchange(ref _plex, 1, 0) == 0)
        {
            OnPlexChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        return false;
    }

    public bool UnlockPlex()
    {
        if (Interlocked.CompareExchange(ref _plex, 0, 1) == 1)
        {
            OnPlexChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        logger.LogWarning("UnlockPlex called but Plex was not locked (double-release or non-owner release)");
        return false;
    }

    public bool IsPlexLocked() => Volatile.Read(ref _plex) == 1;

    public bool IsRemoteMediaSourceLocked<TMediaSource>() =>
        _lockedRemoteMediaSourceTypes.ContainsKey(typeof(TMediaSource));

    public bool LockRemoteMediaSource<TMediaSource>()
    {
        Type mediaSourceType = typeof(TMediaSource);

        if (_lockedRemoteMediaSourceTypes.TryAdd(mediaSourceType, 0))
        {
            OnRemoteMediaSourceChanged?.Invoke(this, mediaSourceType);
            return true;
        }

        return false;
    }

    public bool UnlockRemoteMediaSource<TMediaSource>()
    {
        Type mediaSourceType = typeof(TMediaSource);

        if (_lockedRemoteMediaSourceTypes.TryRemove(mediaSourceType, out byte _))
        {
            OnRemoteMediaSourceChanged?.Invoke(this, mediaSourceType);
            return true;
        }

        logger.LogWarning(
            "UnlockRemoteMediaSource called for {MediaSourceType} that was not locked (double-release or non-owner release)",
            mediaSourceType.Name);
        return false;
    }

    public bool LockTrakt()
    {
        if (Interlocked.CompareExchange(ref _trakt, 1, 0) == 0)
        {
            OnTraktChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        return false;
    }

    public bool UnlockTrakt()
    {
        if (Interlocked.CompareExchange(ref _trakt, 0, 1) == 1)
        {
            OnTraktChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        logger.LogWarning("UnlockTrakt called but Trakt was not locked (double-release or non-owner release)");
        return false;
    }

    public bool IsTraktLocked() => Volatile.Read(ref _trakt) == 1;

    public bool LockEmbyCollections()
    {
        if (Interlocked.CompareExchange(ref _embyCollections, 1, 0) == 0)
        {
            OnEmbyCollectionsChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        return false;
    }

    public bool UnlockEmbyCollections()
    {
        if (Interlocked.CompareExchange(ref _embyCollections, 0, 1) == 1)
        {
            OnEmbyCollectionsChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        logger.LogWarning(
            "UnlockEmbyCollections called but Emby collections were not locked (double-release or non-owner release)");
        return false;
    }

    public bool AreEmbyCollectionsLocked() => Volatile.Read(ref _embyCollections) == 1;

    public bool LockJellyfinCollections()
    {
        if (Interlocked.CompareExchange(ref _jellyfinCollections, 1, 0) == 0)
        {
            OnJellyfinCollectionsChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        return false;
    }

    public bool UnlockJellyfinCollections()
    {
        if (Interlocked.CompareExchange(ref _jellyfinCollections, 0, 1) == 1)
        {
            OnJellyfinCollectionsChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        logger.LogWarning(
            "UnlockJellyfinCollections called but Jellyfin collections were not locked (double-release or non-owner release)");
        return false;
    }

    public bool AreJellyfinCollectionsLocked() => Volatile.Read(ref _jellyfinCollections) == 1;

    public bool LockPlexCollections()
    {
        if (Interlocked.CompareExchange(ref _plexCollections, 1, 0) == 0)
        {
            OnPlexCollectionsChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        return false;
    }

    public bool UnlockPlexCollections()
    {
        if (Interlocked.CompareExchange(ref _plexCollections, 0, 1) == 1)
        {
            OnPlexCollectionsChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        logger.LogWarning(
            "UnlockPlexCollections called but Plex collections were not locked (double-release or non-owner release)");
        return false;
    }

    public bool ArePlexCollectionsLocked() => Volatile.Read(ref _plexCollections) == 1;

    public async Task<bool> LockPlayout(int playoutId)
    {
        if (_lockedPlayouts.TryAdd(playoutId, 0))
        {
            await mediator.Publish(new PlayoutUpdatedNotification(playoutId, true));
            return true;
        }

        return false;
    }

    public async Task<bool> UnlockPlayout(int playoutId)
    {
        if (_lockedPlayouts.TryRemove(playoutId, out byte _))
        {
            await mediator.Publish(new PlayoutUpdatedNotification(playoutId, false));
            return true;
        }

        logger.LogWarning(
            "UnlockPlayout called for playout {PlayoutId} that was not locked (double-release or non-owner release)",
            playoutId);
        return false;
    }

    public bool IsPlayoutLocked(int playoutId) => _lockedPlayouts.ContainsKey(playoutId);

    public bool LockTroubleshootingPlayback()
    {
        if (Interlocked.CompareExchange(ref _troubleshootingPlayback, 1, 0) == 0)
        {
            OnTroubleshootingPlaybackChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        return false;
    }

    public bool UnlockTroubleshootingPlayback()
    {
        if (Interlocked.CompareExchange(ref _troubleshootingPlayback, 0, 1) == 1)
        {
            OnTroubleshootingPlaybackChanged?.Invoke(this, EventArgs.Empty);
            return true;
        }

        logger.LogWarning(
            "UnlockTroubleshootingPlayback called but troubleshooting playback was not locked (double-release or non-owner release)");
        return false;
    }

    public bool IsTroubleshootingPlaybackLocked() => Volatile.Read(ref _troubleshootingPlayback) == 1;
}