Mitigate race condition, introduce timeout and simplify code for property gets

Author: softworkz

src/ElectronNET.API/API/ApiBase.cs

@@ -1,15 +1,22 @@
 namespace ElectronNET.API
 {
+    using System;
     using System.Collections.Concurrent;
+    using System.Diagnostics;
     using System.Runtime.CompilerServices;
+    using System.Threading.Tasks;
     using ElectronNET.Common;
 
     public abstract class ApiBase
     {
         internal const int PropertyTimeout = 1000;
 
         private readonly string objectName;
+        private readonly ConcurrentDictionary<string, PropertyGetter> propertyGetters = new ConcurrentDictionary<string, PropertyGetter>();
+        private readonly ConcurrentDictionary<string, string> propertyEventNames = new ConcurrentDictionary<string, string>();
+        private readonly ConcurrentDictionary<string, string> propertyMessageNames = new ConcurrentDictionary<string, string>();
         private readonly ConcurrentDictionary<string, string> methodMessageNames = new ConcurrentDictionary<string, string>();
+        private readonly object objLock = new object();
 
         public virtual int Id
         {
@@ -82,5 +89,89 @@ protected void CallMethod3(object val1, object val2, object val3, [CallerMemberN
                 BridgeConnector.Socket.Emit(messageName, val1, val2, val3);
             }
         }
+
+        protected Task<T> GetPropertyAsync<T>([CallerMemberName] string callerName = null)
+        {
+            Debug.Assert(callerName != null, nameof(callerName) + " != null");
+
+            lock (this.objLock)
+            {
+                return this.propertyGetters.GetOrAdd(callerName, _ =>
+                {
+                    var getter = new PropertyGetter<T>(this, callerName, PropertyTimeout);
+
+                    getter.Task<T>().ContinueWith(_ =>
+                    {
+                        lock (this.objLock)
+                        {
+                            return this.propertyGetters.TryRemove(callerName, out var _);
+                        }
+                    });
+
+                    return getter;
+                }).Task<T>();
+            }
+        }
+
+        internal abstract class PropertyGetter
+        {
+            public abstract Task<T> Task<T>();
+        }
+
+        internal class PropertyGetter<T> : PropertyGetter
+        {
+            private readonly Task<T> tcsTask;
+            private TaskCompletionSource<T> tcs;
+
+            public PropertyGetter(ApiBase apiBase, string callerName, int timeoutMs)
+            {
+                this.tcs = new TaskCompletionSource<T>(TaskCreationOptions.RunContinuationsAsynchronously);
+                this.tcsTask = this.tcs.Task;
+
+                var eventName = apiBase.propertyEventNames.GetOrAdd(callerName, s => $"{apiBase.objectName}-{s.StripAsync().LowerFirst()}{apiBase.SocketEventCompleteSuffix}");
+                var messageName = apiBase.propertyMessageNames.GetOrAdd(callerName, s => apiBase.objectName + s.StripAsync());
+
+                BridgeConnector.Socket.On<T>(eventName, (result) =>
+                {
+                    BridgeConnector.Socket.Off(eventName);
+
+                    lock (this)
+                    {
+                        this.tcs?.SetResult(result);
+                        this.tcs = null;
+                    }
+                });
+
+                if (apiBase.Id >= 0)
+                {
+                    BridgeConnector.Socket.Emit(messageName, apiBase.Id);
+                }
+                else
+                {
+                    BridgeConnector.Socket.Emit(messageName);
+                }
+
+                System.Threading.Tasks.Task.Delay(ApiBase.PropertyTimeout).ContinueWith(_ =>
+                {
+                    if (this.tcs != null)
+                    {
+                        lock (this)
+                        {
+                            if (this.tcs != null)
+                            {
+                                var ex = new TimeoutException($"No response after {timeoutMs:D}ms trying to retrieve value {apiBase.objectName}.{callerName}()");
+                                this.tcs.TrySetException(ex);
+                                this.tcs = null;
+                            }
+                        }
+                    }
+                });
+            }
+
+            public override Task<T1> Task<T1>()
+            {
+                return this.tcsTask as Task<T1>;
+            }
+        }
     }
 }