Adding Multicast.

AsyncRx.NET/System.Reactive.Async/System/Reactive/Linq/Operators/Multicast.cs

@@ -0,0 +1,93 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information. 
+
+using System.Reactive.Disposables;
+using System.Reactive.Subjects;
+using System.Threading.Tasks;
+
+namespace System.Reactive.Linq
+{
+    partial class AsyncObservable
+    {
+        public static IConnectableAsyncObservable<TResult> Multicast<TSource, TResult>(this IAsyncObservable<TSource> source, IAsyncSubject<TSource, TResult> subject)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (subject == null)
+                throw new ArgumentNullException(nameof(subject));
+
+            return new ConnectableAsyncObservable<TSource, TResult>(source, subject);
+        }
+
+        public static IAsyncObservable<TSource> Multicast<TSource>(this IAsyncObservable<TSource> source, Func<IAsyncSubject<TSource>> subjectFactory)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (subjectFactory == null)
+                throw new ArgumentNullException(nameof(subjectFactory));
+
+            return Multicast<TSource, TSource, TSource>(source, () => Task.FromResult<IAsyncSubject<TSource, TSource>>(subjectFactory()), x => Task.FromResult(x));
+        }
+
+        public static IAsyncObservable<TSource> Multicast<TSource>(this IAsyncObservable<TSource> source, Func<Task<IAsyncSubject<TSource>>> subjectFactory)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (subjectFactory == null)
+                throw new ArgumentNullException(nameof(subjectFactory));
+
+            return Multicast<TSource, TSource, TSource>(source, async () => await subjectFactory().ConfigureAwait(false), x => Task.FromResult(x));
+        }
+
+        public static IAsyncObservable<TResult> Multicast<TSource, TIntermediate, TResult>(this IAsyncObservable<TSource> source, Func<IAsyncSubject<TSource, TIntermediate>> subjectFactory, Func<IAsyncObservable<TIntermediate>, IAsyncObservable<TResult>> selector)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (subjectFactory == null)
+                throw new ArgumentNullException(nameof(subjectFactory));
+            if (selector == null)
+                throw new ArgumentNullException(nameof(selector));
+
+            return Multicast(source, () => Task.FromResult(subjectFactory()), x => Task.FromResult(selector(x)));
+        }
+
+        public static IAsyncObservable<TResult> Multicast<TSource, TIntermediate, TResult>(this IAsyncObservable<TSource> source, Func<Task<IAsyncSubject<TSource, TIntermediate>>> subjectFactory, Func<IAsyncObservable<TIntermediate>, Task<IAsyncObservable<TResult>>> selector)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (subjectFactory == null)
+                throw new ArgumentNullException(nameof(subjectFactory));
+            if (selector == null)
+                throw new ArgumentNullException(nameof(selector));
+
+            return Create<TResult>(async observer =>
+            {
+                var observable = default(IAsyncObservable<TResult>);
+                var connectable = default(IConnectableAsyncObservable<TIntermediate>);
+
+                try
+                {
+                    var subject = await subjectFactory().ConfigureAwait(false);
+                    connectable = new ConnectableAsyncObservable<TSource, TIntermediate>(source, subject);
+                    observable = await selector(connectable).ConfigureAwait(false);
+                }
+                catch (Exception ex)
+                {
+                    await observer.OnErrorAsync(ex).ConfigureAwait(false);
+                    return AsyncDisposable.Nop;
+                }
+
+                var d = new CompositeAsyncDisposable();
+
+                var subscription = await observable.SubscribeAsync(observer).ConfigureAwait(false);
+                await d.AddAsync(subscription).ConfigureAwait(false);
+
+                var connection = await connectable.ConnectAsync().ConfigureAwait(false);
+                await d.AddAsync(connection).ConfigureAwait(false);
+
+                return d;
+            });
+        }
+    }
+}