WIP to allow mediter handlers to be subscribed to

2024-05-14 22:49:16 +01:00
parent 32829d1cf3
commit 7e57c0d28d
15 changed files with 81 additions and 83 deletions
@@ -0,0 +1,81 @@
+using System.Reactive.Disposables;
+
+namespace Toolkit.Foundation;
+
+public class Subscription(SubscriptionCollection subscriptions,
+    IDisposer disposer) :
+    ISubscription
+{
+    public void Add(object subscriber)
+    {
+        Type handlerType = subscriber.GetType();
+        object? key = GetKeyFromHandler(subscriber);
+        foreach (Type interfaceType in GetHandlerInterfaces(handlerType))
+        {
+            if (interfaceType.GetGenericArguments().FirstOrDefault() is Type argumentType)
+            {
+                string subscriptionKey = $"{(key is not null ? $"{key}:" : "")}{argumentType}";
+                subscriptions.AddOrUpdate(subscriptionKey, _ => new List<WeakReference> { new(subscriber) }, (_, collection) =>
+                {
+                    collection.Add(new WeakReference(subscriber));
+                    return collection;
+                });
+
+                disposer.Add(subscriber, Disposable.Create(() => RemoveSubscriber(subscriber, argumentType)));
+            }
+        }
+    }
+
+    public void Remove(object subscriber)
+    {
+        Type handlerType = subscriber.GetType();
+        object? key = GetKeyFromHandler(subscriber);
+        foreach (Type interfaceType in GetHandlerInterfaces(handlerType))
+        {
+            if (interfaceType.GetGenericArguments().FirstOrDefault() is Type argumentType)
+            {
+                string subscriptionKey = $"{(key is not null ? $"{key}:" : "")}{argumentType}";
+                if (subscriptions.TryGetValue(subscriptionKey, out List<WeakReference>? subscribers))
+                {
+                    for (int i = subscribers.Count - 1; i >= 0; i--)
+                    {
+                        if (!subscribers[i].IsAlive || subscribers[i].Target == subscriber)
+                        {
+                            subscribers.RemoveAt(i);
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+
+    private void RemoveSubscriber(object subscriber,
+        Type argumentType)
+    {
+        string subscriptionKey = $"{argumentType}";
+        if (subscriptions.TryGetValue(subscriptionKey, out List<WeakReference>? subscribers))
+        {
+            for (int i = subscribers.Count - 1; i >= 0; i--)
+            {
+                if (subscribers[i].Target == subscriber)
+                {
+                    subscribers.RemoveAt(i);
+                }
+            }
+
+            if (subscribers.Count == 0)
+            {
+                subscriptions.TryRemove(subscriptionKey, out _);
+            }
+        }
+    }
+
+    private object? GetKeyFromHandler(object handler) =>
+        handler.GetAttribute<NotificationAttribute>() is NotificationAttribute attribute
+            ? handler.GetPropertyValue(() => attribute.Key) is { } value ? value : attribute.Key : null;
+
+    private IEnumerable<Type> GetHandlerInterfaces(Type handlerType) =>
+        handlerType.GetInterfaces().Where(interfaceType => interfaceType.IsGenericType &&
+            interfaceType.GetGenericTypeDefinition() == typeof(INotificationHandler<>));
+}