MQTTnet/Source/MQTTnet.Server/Internal/TopicHashMaskSubscriptions.cs

namespace MQTTnet.Server.Internal;

/// <summary>
///     Helper class that stores subscriptions by their topic hash mask.
/// </summary>
public sealed class TopicHashMaskSubscriptions
{
    public Dictionary<ulong, HashSet<MqttSubscription>> SubscriptionsByHashMask { get; } = new Dictionary<ulong, HashSet<MqttSubscription>>();

    public void AddSubscription(MqttSubscription subscription)
    {
        if (!SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
        {
            subscriptions = new HashSet<MqttSubscription>();
            SubscriptionsByHashMask.Add(subscription.TopicHashMask, subscriptions);
        }
        subscriptions.Add(subscription);
    }

    public void RemoveSubscription(MqttSubscription subscription)
    {
        if (SubscriptionsByHashMask.TryGetValue(subscription.TopicHashMask, out var subscriptions))
        {
            subscriptions.Remove(subscription);
            if (subscriptions.Count == 0)
            {
                SubscriptionsByHashMask.Remove(subscription.TopicHashMask);
            }
        }
    }
}