From 614ad24b5c359870716ff1cdafec7d8220b5f454 Mon Sep 17 00:00:00 2001
From: Simon G <simon.gockner@gmail.com>
Date: Fri, 13 Nov 2020 13:17:34 +0100
Subject: [PATCH] - add GenericMethodCaller and matching exception

---
 .../GenericMethodNotFoundException.cs         |  24 ++++
 GBase/Helpers/GenericMethodCaller.cs          | 108 ++++++++++++++++++
 2 files changed, 132 insertions(+)
 create mode 100644 GBase/Exceptions/GenericMethodNotFoundException.cs
 create mode 100644 GBase/Helpers/GenericMethodCaller.cs

diff --git a/GBase/Exceptions/GenericMethodNotFoundException.cs b/GBase/Exceptions/GenericMethodNotFoundException.cs
new file mode 100644
index 0000000..45f6658
--- /dev/null
+++ b/GBase/Exceptions/GenericMethodNotFoundException.cs
@@ -0,0 +1,24 @@
+// Author: Gockner, Simon
+// Created: 2020-11-13
+// Copyright(c) 2020 SimonG. All Rights Reserved.
+
+using System;
+
+namespace GBase.Exceptions
+{
+    /// <summary>
+    /// Could not find generic method
+    /// </summary>
+    internal class GenericMethodNotFoundException : Exception
+    {
+        /// <summary>
+        /// Could not find generic method
+        /// </summary>
+        /// <param name="functionName">The name of the generic method</param>
+        public GenericMethodNotFoundException(string functionName)
+            : base($"Could not find function {functionName}")
+        {
+            
+        }
+    }
+}
\ No newline at end of file
diff --git a/GBase/Helpers/GenericMethodCaller.cs b/GBase/Helpers/GenericMethodCaller.cs
new file mode 100644
index 0000000..9ac3ed5
--- /dev/null
+++ b/GBase/Helpers/GenericMethodCaller.cs
@@ -0,0 +1,108 @@
+// Author: Gockner, Simon
+// Created: 2020-11-13
+// Copyright(c) 2020 SimonG. All Rights Reserved.
+
+using System;
+using System.Reflection;
+using System.Threading.Tasks;
+using GBase.Exceptions;
+
+namespace GBase.Helpers
+{
+    internal static class GenericMethodCaller
+    {
+        /// <summary>
+        /// Call a generic method without generic type parameters
+        /// </summary>
+        /// <param name="caller">The caller of the method</param>
+        /// <param name="functionName">The name of the method to call</param>
+        /// <param name="bindingFlags">The <see cref="BindingFlags"/> to find the method</param>
+        /// <param name="genericParameter">The generic parameter as <see cref="Type"/> parameter</param>
+        /// <param name="parameters">The parameters of the method</param>
+        /// <returns>The result of invoking the method</returns>
+        /// <exception cref="GenericMethodNotFoundException">Could not find the generic method</exception>
+        /// <exception cref="Exception">Any <see cref="Exception"/> thrown after invoking the generic method</exception>
+        public static object Call(object caller, string functionName, BindingFlags bindingFlags, Type genericParameter, params object[] parameters) => 
+            GetGenericMethod(caller, functionName, bindingFlags, genericParameter).InvokeGenericMethod(caller, parameters);
+
+        /// <summary>
+        /// Call a generic method without generic type parameters
+        /// </summary>
+        /// <param name="caller">The caller of the method</param>
+        /// <param name="functionName">The name of the method to call</param>
+        /// <param name="bindingFlags">The <see cref="BindingFlags"/> to find the method</param>
+        /// <param name="genericParameter">The generic parameter as <see cref="Type"/> parameter</param>
+        /// <param name="secondGenericParameter"></param>
+        /// <param name="parameters">The parameters of the method</param>
+        /// <returns>The result of invoking the method</returns>
+        /// <exception cref="GenericMethodNotFoundException">Could not find the generic method</exception>
+        /// <exception cref="Exception">Any <see cref="Exception"/> thrown after invoking the generic method</exception>
+        public static object Call(object caller, string functionName, BindingFlags bindingFlags, Type genericParameter, Type secondGenericParameter,params object[] parameters) => 
+            GetGenericMethod(caller, functionName, bindingFlags, genericParameter, secondGenericParameter).InvokeGenericMethod(caller, parameters);
+
+        /// <summary>
+        /// Call a generic method asynchronously without generic type parameters
+        /// </summary>
+        /// <param name="caller">The caller of the method</param>
+        /// <param name="functionName">The name of the method to call</param>
+        /// <param name="bindingFlags">The <see cref="BindingFlags"/> to find the method</param>
+        /// <param name="genericParameter">The generic parameter as <see cref="Type"/> parameter</param>
+        /// <param name="parameters">The parameters of the method</param>
+        /// <returns>The result of invoking the method</returns>
+        /// <exception cref="GenericMethodNotFoundException">Could not find the generic method</exception>
+        /// <exception cref="Exception">Any <see cref="Exception"/> thrown after invoking the generic method</exception>
+        public static async Task<object> CallAsync(object caller, string functionName, BindingFlags bindingFlags, Type genericParameter, params object[] parameters) => 
+            await GetGenericMethod(caller, functionName, bindingFlags, genericParameter).InvokeGenericMethodAsync(caller, parameters);
+
+        /// <summary>
+        /// Call a generic method asynchronously without generic type parameters
+        /// </summary>
+        /// <param name="caller">The caller of the method</param>
+        /// <param name="functionName">The name of the method to call</param>
+        /// <param name="bindingFlags">The <see cref="BindingFlags"/> to find the method</param>
+        /// <param name="genericParameter">The generic parameter as <see cref="Type"/> parameter</param>
+        /// <param name="secondGenericParameter"></param>
+        /// <param name="parameters">The parameters of the method</param>
+        /// <returns>The result of invoking the method</returns>
+        /// <exception cref="GenericMethodNotFoundException">Could not find the generic method</exception>
+        /// <exception cref="Exception">Any <see cref="Exception"/> thrown after invoking the generic method</exception>
+        public static async Task<object> CallAsync(object caller, string functionName, BindingFlags bindingFlags, Type genericParameter, Type secondGenericParameter, params object[] parameters) => 
+            await GetGenericMethod(caller, functionName, bindingFlags, genericParameter, secondGenericParameter).InvokeGenericMethodAsync(caller, parameters);
+
+        private static MethodInfo GetGenericMethod(object caller, string functionName, BindingFlags bindingFlags, params Type[] genericParameters)
+        {
+            MethodInfo genericMethod = caller.GetType().GetMethod(functionName, bindingFlags)?.MakeGenericMethod(genericParameters);
+            
+            if (genericMethod == null)
+                throw new GenericMethodNotFoundException(functionName);
+
+            return genericMethod;
+        }
+
+        private static object InvokeGenericMethod(this MethodInfo genericMethod, object caller, params object[] parameters)
+        {
+            try //exceptions thrown by methods called with invoke are wrapped into another exception, the exception thrown by the invoked method can be returned by `Exception.GetBaseException()`
+            {
+                return genericMethod.Invoke(caller, parameters);
+            }
+            catch (Exception ex)
+            {
+                throw ex.GetBaseException();
+            }
+        }
+
+        private static async Task<object> InvokeGenericMethodAsync(this MethodInfo genericMethod, object caller, params object[] parameters)
+        {
+            try //exceptions thrown by methods called with invoke are wrapped into another exception, the exception thrown by the invoked method can be returned by `Exception.GetBaseException()`
+            {
+                dynamic awaitable = genericMethod.Invoke(caller, parameters);
+                await awaitable;
+                return awaitable.GetAwaiter().GetResult();
+            }
+            catch (Exception ex)
+            {
+                throw ex.GetBaseException();
+            }
+        }
+    }
+}
\ No newline at end of file