Resolves #1

Author: joel-jeremy

Src/Xer.Cqrs.CommandStack.Extensions.Attributes/CommandHandlerAttributeMethod.Factories.cs

@@ -0,0 +1,190 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Xer.Cqrs.CommandStack.Extensions.Attributes
+{
+    public partial class CommandHandlerAttributeMethod
+    {
+        #region Factory Methods
+        
+        /// <summary>
+        /// Create CommandHandlerAttributeMethod from the method info.
+        /// </summary>
+        /// <param name="methodInfo">Method info that has CommandHandlerAttribute custom attribute.</param>
+        /// <param name="instanceFactory">Factory delegate that provides an instance of the method info's declaring type.</param>
+        /// <returns>Instance of CommandHandlerAttributeMethod.</returns>
+        public static CommandHandlerAttributeMethod FromMethodInfo(MethodInfo methodInfo, Func<object> instanceFactory)
+        {
+            Type commandType;
+            bool isAsyncMethod;
+
+            if (methodInfo == null)
+            {
+                throw new ArgumentNullException(nameof(methodInfo));
+            }
+
+            if (!IsValid(methodInfo))
+            {
+                throw new InvalidOperationException($"Method is not marked with [CommandHandler] attribute. {createCheckMethodMessage(methodInfo)}.");
+            }
+
+            // Get all method parameters.
+            ParameterInfo[] methodParameters = methodInfo.GetParameters();
+
+            // Get first method parameter that is a class (not struct). This assumes that the first parameter is the command.
+            ParameterInfo commandParameter = methodParameters.FirstOrDefault();
+            if (commandParameter != null)
+            {
+                // Check if parameter is a class.
+                if (!commandParameter.ParameterType.GetTypeInfo().IsClass)
+                {
+                    throw new InvalidOperationException($"Method's command parameter is not a reference type, only reference type commands are supported. {createCheckMethodMessage(methodInfo)}.");
+                }
+                           
+                // Set command type.
+                commandType = commandParameter.ParameterType;
+            }
+            else
+            {                
+                // Method has no parameter.
+                throw new InvalidOperationException($"Method must accept a command object as a parameter. {createCheckMethodMessage(methodInfo)}.");
+            }
+
+            // Only valid return types are Task/void.
+            if (methodInfo.ReturnType == typeof(Task))
+            {
+                isAsyncMethod = true;
+            }
+            else if (methodInfo.ReturnType == typeof(void))
+            {
+                isAsyncMethod = false;
+
+                // if(methodInfo.CustomAttributes.Any(p => p.AttributeType == typeof(AsyncStateMachineAttribute)))
+                // {
+                //     throw new InvalidOperationException($"Methods with async void signatures are not allowed. A Task may be used as return type instead of void. Check method: {methodInfo.ToString()}.");
+                // }
+            }
+            else
+            {
+                // Return type is not Task/void. Invalid.
+                throw new InvalidOperationException($"Method marked with [CommandHandler] can only have void or a Task as return value. {createCheckMethodMessage(methodInfo)}.");
+            }
+
+            bool supportsCancellation = methodParameters.Any(p => p.ParameterType == typeof(CancellationToken));
+
+            if (!isAsyncMethod && supportsCancellation)
+            {
+                throw new InvalidOperationException($"Cancellation token support is only available for async methods (methods returning a Task). {createCheckMethodMessage(methodInfo)}.");
+            }
+
+            return new CommandHandlerAttributeMethod(methodInfo, commandType, instanceFactory, isAsyncMethod, supportsCancellation);
+
+            // Local function.
+            string createCheckMethodMessage(MethodInfo method) => $"Check {methodInfo.DeclaringType.Name}'s {methodInfo.ToString()} method";
+        }
+
+        /// <summary>
+        /// Create CommandHandlerAttributeMethod from the method info.
+        /// </summary>
+        /// <param name="methodInfos">Method infos that have CommandHandlerAttribute custom attributes.</param>
+        /// <param name="instanceFactory">Factory delegate that provides an instance of a method info's declaring type.</param>
+        /// <returns>Instances of CommandHandlerAttributeMethod.</returns>
+        public static IEnumerable<CommandHandlerAttributeMethod> FromMethodInfos(IEnumerable<MethodInfo> methodInfos, Func<Type, object> instanceFactory)
+        {
+            if (methodInfos == null)
+            {
+                throw new ArgumentNullException(nameof(methodInfos));
+            }
+
+            return methodInfos.Select(m => FromMethodInfo(m, () => instanceFactory.Invoke(m.DeclaringType)));
+        }
+
+        /// <summary>
+        /// Detect methods marked with [CommandHandler] attribute and translate to CommandHandlerAttributeMethod instances.
+        /// </summary>
+        /// <typeparam name="T">Type to scan for methods marked with the [CommandHandler] attribute.</typeparam>
+        /// <param name="instanceFactory">Factory delegate that provides an instance of the specified type.</param>
+        /// <returns>List of all CommandHandlerAttributeMethod detected.</returns>
+        public static IEnumerable<CommandHandlerAttributeMethod> FromType<T>(Func<T> instanceFactory) where T : class
+        {
+            return FromType(typeof(T), instanceFactory);
+        }
+
+        /// <summary>
+        /// Detect methods marked with [CommandHandler] attribute and translate to CommandHandlerAttributeMethod instances.
+        /// </summary>
+        /// <param name="type">Type to scan for methods marked with the [CommandHandler] attribute.</param>
+        /// <param name="instanceFactory">Factory delegate that provides an instance of the specified type.</param>
+        /// <returns>List of all CommandHandlerAttributeMethod detected.</returns>
+        public static IEnumerable<CommandHandlerAttributeMethod> FromType(Type type, Func<object> instanceFactory)
+        {
+            if (type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            IEnumerable<MethodInfo> methods = type.GetTypeInfo().DeclaredMethods.Where(m => IsValid(m));
+
+            return FromMethodInfos(methods, _ => instanceFactory.Invoke());
+        }
+
+        /// <summary>
+        /// Detect methods marked with [CommandHandler] attribute and translate to CommandHandlerAttributeMethod instances.
+        /// </summary>
+        /// <param name="types">Types to scan for methods marked with the [CommandHandler] attribute.</param>
+        /// <param name="instanceFactory">Factory delegate that provides an instance of a given type.</param>
+        /// <returns>List of all CommandHandlerAttributeMethod detected.</returns>
+        public static IEnumerable<CommandHandlerAttributeMethod> FromTypes(IEnumerable<Type> types, Func<Type, object> instanceFactory)
+        {
+            if (types == null)
+            {
+                throw new ArgumentNullException(nameof(types));
+            }
+
+            return types.SelectMany(type => FromType(type, () => instanceFactory.Invoke(type)));
+        }
+
+        /// <summary>
+        /// Detect methods marked with [CommandHandler] attribute and translate to CommandHandlerAttributeMethod instances.
+        /// </summary>
+        /// <param name="commandHandlerAssembly">Assembly to scan for methods marked with the [CommandHandler] attribute.</param>
+        /// <param name="instanceFactory">Factory delegate that provides an instance of a type that has methods marked with [CommandHandler] attribute.</param>
+        /// <returns>List of all CommandHandlerAttributeMethod detected.</returns>
+        public static IEnumerable<CommandHandlerAttributeMethod> FromAssembly(Assembly commandHandlerAssembly, Func<Type, object> instanceFactory)
+        {
+            if (commandHandlerAssembly == null)
+            {
+                throw new ArgumentNullException(nameof(commandHandlerAssembly));
+            }
+
+            IEnumerable<MethodInfo> commandHandlerMethods = commandHandlerAssembly.DefinedTypes
+                                                                .Where(typeInfo => IsFoundInType(typeInfo))
+                                                                .SelectMany(typeInfo => typeInfo.DeclaredMethods.Where(method => 
+                                                                    IsValid(method)));
+            
+            return FromMethodInfos(commandHandlerMethods, instanceFactory);
+        }
+
+        /// <summary>
+        /// Detect methods marked with [CommandHandler] attribute and translate to CommandHandlerAttributeMethod instances.
+        /// </summary>
+        /// <param name="commandHandlerAssemblies">Assemblies to scan for methods marked with the [CommandHandler] attribute.</param>
+        /// <param name="instanceFactory">Factory delegate that provides an instance of a type that has methods marked with [CommandHandler] attribute.</param>
+        /// <returns>List of all CommandHandlerAttributeMethod detected.</returns>
+        public static IEnumerable<CommandHandlerAttributeMethod> FromAssemblies(IEnumerable<Assembly> commandHandlerAssemblies, Func<Type, object> instanceFactory)
+        {
+            if (commandHandlerAssemblies == null)
+            {
+                throw new ArgumentNullException(nameof(commandHandlerAssemblies));
+            }
+
+            return commandHandlerAssemblies.SelectMany(assembly => FromAssembly(assembly, instanceFactory));
+        }
+        
+        #endregion Factory Methods
+    }
+}