Added Chain type for chaining actions over instances of the same type

Author: jamesmcroft

src/MADE.Runtime/Actions/Chain.cs

@@ -0,0 +1,90 @@
+namespace MADE.Runtime.Actions
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+
+    /// <summary>
+    /// Defines an implementation for a chain of objects.
+    /// </summary>
+    /// <typeparam name="T">The type of object being chained.</typeparam>
+    public class Chain<T> : IChain<T>
+        where T : class
+    {
+        private readonly List<WeakReference<T>> chain = new List<WeakReference<T>>();
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Chain{T}"/> class with an instance.
+        /// </summary>
+        /// <param name="instance">The instance to begin the chain.</param>
+        public Chain(T instance)
+        {
+            this.chain.Add(new WeakReference<T>(instance));
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Chain{T}"/> class with a collection of instances.
+        /// </summary>
+        /// <param name="instances">The instances to begin the chain.</param>
+        public Chain(IEnumerable<T> instances)
+        {
+            this.chain.AddRange(instances.Select(i => new WeakReference<T>(i)));
+        }
+
+        /// <summary>
+        /// Concatenates the current instances in the chain with the specified instance.
+        /// </summary>
+        /// <param name="instance">The instance to chain.</param>
+        /// <returns>The updated <see cref="Chain{T}"/>.</returns>
+        public Chain<T> With(T instance)
+        {
+            this.chain.Add(new WeakReference<T>(instance));
+            return this;
+        }
+
+        /// <summary>
+        /// Concatenates the current instances in the chain with the specified instances.
+        /// </summary>
+        /// <param name="instances">The instances to chain.</param>
+        /// <returns>The updated <see cref="Chain{T}"/></returns>
+        public Chain<T> With(IEnumerable<T> instances)
+        {
+            this.chain.AddRange(instances.Select(i => new WeakReference<T>(i)));
+            return this;
+        }
+
+        /// <summary>
+        /// Invokes an action with the chain.
+        /// </summary>
+        /// <param name="func">The action to invoke.</param>
+        /// <exception cref="Exception">Potential exceptions thrown if delegate callback throws an exception.</exception>
+        public void Invoke(Action<T> func)
+        {
+            foreach (WeakReference<T> instance in this.chain)
+            {
+                if (instance.TryGetTarget(out T i))
+                {
+                    func(i);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Invokes an asynchronous action with the chain.
+        /// </summary>
+        /// <param name="func">The asynchronous action to invoke.</param>
+        /// <returns>An asynchronous operation.</returns>
+        /// <exception cref="Exception">Potential exceptions thrown if delegate callback throws an exception.</exception>
+        public async Task InvokeAsync(Func<T, Task> func)
+        {
+            foreach (WeakReference<T> instance in this.chain)
+            {
+                if (instance.TryGetTarget(out T i))
+                {
+                    await func(i);
+                }
+            }
+        }
+    }
+}

src/MADE.Runtime/Actions/IChain.cs

@@ -0,0 +1,41 @@
+namespace MADE.Runtime.Actions
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading.Tasks;
+
+    /// <summary>
+    /// Defines an interface for a chain of objects.
+    /// </summary>
+    /// <typeparam name="T">The type of object being chained.</typeparam>
+    public interface IChain<T>
+        where T : class
+    {
+        /// <summary>
+        /// Concatenates the current instances in the chain with the specified instance.
+        /// </summary>
+        /// <param name="instance">The instance to chain.</param>
+        /// <returns>The updated <see cref="Chain{T}"/>.</returns>
+        Chain<T> With(T instance);
+
+        /// <summary>
+        /// Concatenates the current instances in the chain with the specified instances.
+        /// </summary>
+        /// <param name="instances">The instances to chain.</param>
+        /// <returns>The updated <see cref="Chain{T}"/></returns>
+        Chain<T> With(IEnumerable<T> instances);
+
+        /// <summary>
+        /// Invokes an action with the chain.
+        /// </summary>
+        /// <param name="func">The action to invoke.</param>
+        void Invoke(Action<T> func);
+
+        /// <summary>
+        /// Invokes an asynchronous action with the chain.
+        /// </summary>
+        /// <param name="func">The asynchronous action to invoke.</param>
+        /// <returns>An asynchronous operation.</returns>
+        Task InvokeAsync(Func<T, Task> func);
+    }
+}