Amended registration of health check scheduled notifiers (email and Slack) to use a resolver method and allow others to be added without modifying core

src/Umbraco.Web/HealthCheck/HealthCheckNotificationMethodResolver.cs

@@ -0,0 +1,86 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Web;
+using Umbraco.Core;
+using Umbraco.Core.Logging;
+using Umbraco.Core.ObjectResolution;
+using Umbraco.Core.Persistence.SqlSyntax;
+using Umbraco.Web.HealthCheck.NotificationMethods;
+
+namespace Umbraco.Web.HealthCheck
+{
+    using System.Configuration;
+    using System.Reflection;
+
+    using Umbraco.Core.Configuration.HealthChecks;
+
+    /// <summary>
+    /// Resolves all health check instances
+    /// </summary>
+    /// <remarks>
+    /// Each instance scoped to the lifespan of the http request
+    /// </remarks>
+    internal class HealthCheckNotificationMethodResolver : LazyManyObjectsResolverBase<HealthCheckNotificationMethodResolver, IHealthCheckNotificatationMethod>, IHealthCheckNotificationMethodsResolver
+    {
+        public HealthCheckNotificationMethodResolver(ILogger logger, Func<IEnumerable<Type>> lazyTypeList)
+            : base(new HealthCheckNotificationMethodServiceProvider(), logger, lazyTypeList, ObjectLifetimeScope.Application)
+        {
+        }
+
+        /// <summary>
+        /// Returns all health check notification method instances
+        /// </summary>
+        public IEnumerable<IHealthCheckNotificatationMethod> NotificationMethods
+        {
+            get { return Values; }
+        }
+
+        /// <summary>
+        /// This will ctor the IHealthCheckNotificatationMethod instances
+        /// </summary>
+	    private class HealthCheckNotificationMethodServiceProvider : IServiceProvider
+        {
+            public object GetService(Type serviceType)
+            {
+                var ctor = serviceType.GetConstructors().FirstOrDefault();
+                if (ctor == null)
+                {
+                    return null;
+                }
+
+                // Load attribute from type in order to find alias for notification method
+                var attribute = serviceType.GetCustomAttributes(typeof(HealthCheckNotificationMethodAttribute), true)
+                    .FirstOrDefault() as HealthCheckNotificationMethodAttribute;
+                if (attribute == null)
+                {
+                    return null;
+                }
+
+                // Using alias, get related configuration
+                var healthCheckConfig = (HealthChecksSection)ConfigurationManager.GetSection("umbracoConfiguration/HealthChecks");
+                var notificationMethods = healthCheckConfig.NotificationSettings.NotificationMethods;
+                var notificationMethod = notificationMethods[attribute.Alias];
+                if (notificationMethod == null)
+                {
+                    return null;
+                }
+
+                // Create array for constructor paramenters.  Will consists of common ones that all notification methods have as well
+                // as those specific to this particular notification method.
+                var baseType = typeof(NotificationMethodBase);
+                var baseTypeCtor = baseType.GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance).First();
+                var baseTypeCtorParamNames = baseTypeCtor.GetParameters().Select(x => x.Name);
+                var ctorParams = new List<object> { notificationMethod.Enabled, notificationMethod.FailureOnly, notificationMethod.Verbosity };
+                ctorParams.AddRange(ctor.GetParameters()
+                    .Where(x => baseTypeCtorParamNames.Contains(x.Name) == false)
+                    .Select(x => notificationMethod.Settings[x.Name].Value));
+
+                // Instantiate the type with the constructor parameters
+                return Activator.CreateInstance(serviceType, ctorParams.ToArray());
+            }
+        }
+    }
+}