From c3d47f6b38ab4888a1d5935182db723e6e8bb39e Mon Sep 17 00:00:00 2001
From: Chris Cameron <chris.cameron@wedoresi.com>
Date: Mon, 2 Oct 2017 14:57:13 -0400
Subject: [PATCH] Tidying, validation, prevent ServiceProvider from being
 instantiated externally

---
 ICD.Common.Utils/Services/ServiceProvider.cs | 149 ++++++++++++++-----
 1 file changed, 108 insertions(+), 41 deletions(-)

diff --git a/ICD.Common.Utils/Services/ServiceProvider.cs b/ICD.Common.Utils/Services/ServiceProvider.cs
index 5eac93c..6ba2507 100644
--- a/ICD.Common.Utils/Services/ServiceProvider.cs
+++ b/ICD.Common.Utils/Services/ServiceProvider.cs
@@ -8,12 +8,60 @@ namespace ICD.Common.Services
 {
 	public sealed class ServiceProvider : IDisposable
 	{
-		#region Static
-
 		private static ServiceProvider s_Instance;
 
+		private readonly Dictionary<Type, object> m_Services;
+		private readonly SafeCriticalSection m_ServicesSection;
+
 		private static ServiceProvider Instance { get { return s_Instance ?? (s_Instance = new ServiceProvider()); } }
 
+		/// <summary>
+		/// Prevent external instantiation.
+		/// </summary>
+		private ServiceProvider()
+		{
+			m_Services = new Dictionary<Type, object>();
+			m_ServicesSection = new SafeCriticalSection();
+		}
+
+		#region IDisposable
+
+		/// <summary>
+		/// Release resources.
+		/// </summary>
+		public void Dispose()
+		{
+			try
+			{
+				m_ServicesSection.Enter();
+				foreach (object service in m_Services.Values.Distinct())
+				{
+					if (!(service is IDisposable))
+						continue;
+					((IDisposable)service).Dispose();
+				}
+				m_Services.Clear();
+			}
+			finally
+			{
+				m_ServicesSection.Leave();
+			}
+		}
+
+		/// <summary>
+		/// Release resources.
+		/// </summary>
+		public static void DisposeStatic()
+		{
+			if (s_Instance != null)
+				s_Instance.Dispose();
+			s_Instance = null;
+		}
+
+		#endregion
+
+		#region Methods
+
 		/// <summary>
 		/// Retrieves the registered service of the given type. Use this for required dependencies.
 		/// </summary>
@@ -37,6 +85,9 @@ namespace ICD.Common.Services
 		[NotNull]
 		public static object GetService(Type tService)
 		{
+			if (tService == null)
+				throw new ArgumentNullException("tService");
+
 			return Instance.GetServiceInstance(tService);
 		}
 
@@ -63,14 +114,10 @@ namespace ICD.Common.Services
 		[CanBeNull]
 		public static object TryGetService(Type tService)
 		{
-			try
-			{
-				return Instance.GetServiceInstance(tService);
-			}
-			catch (ServiceNotFoundException)
-			{
-				return null;
-			}
+			if (tService == null)
+				throw new ArgumentNullException("tService");
+
+			return Instance.TryGetServiceInstance(tService);
 		}
 
 		/// <summary>
@@ -81,6 +128,10 @@ namespace ICD.Common.Services
 		[PublicAPI]
 		public static void AddService<TService>(TService service)
 		{
+// ReSharper disable once CompareNonConstrainedGenericWithNull
+			if (service == null)
+				throw new ArgumentNullException("service");
+
 			AddService(typeof(TService), service);
 		}
 
@@ -92,26 +143,38 @@ namespace ICD.Common.Services
 		[PublicAPI]
 		public static void AddService(Type tService, object service)
 		{
+			if (tService == null)
+				throw new ArgumentNullException("tService");
+
+			if (service == null)
+				throw new ArgumentNullException("service");
+
 			Instance.AddServiceInstance(tService, service);
 		}
 
 		#endregion
 
-		private readonly Dictionary<Type, object> m_Services = new Dictionary<Type, object>();
-		private readonly SafeCriticalSection m_ServicesSection = new SafeCriticalSection();
+		#region Private Methods
 
-		#region Methods
-
-		private object GetServiceInstance(Type tService)
+		/// <summary>
+		/// Retrieves the registered service of the given type. Returns null if the service type was not found.
+		/// Use this for optional dependencies.
+		/// </summary>
+		/// <param name="tService">service type to retrieve</param>
+		/// <returns>requested service or null if that service type is not registered</returns>
+		[CanBeNull]
+		private object TryGetServiceInstance(Type tService)
 		{
+			if (tService == null)
+				throw new ArgumentNullException("tService");
+
 			try
 			{
 				m_ServicesSection.Enter();
 
 				object service;
-				if (m_Services.TryGetValue(tService, out service) && service != null)
-					return service;
-				throw new ServiceNotFoundException(tService);
+				m_Services.TryGetValue(tService, out service);
+				return service;
 			}
 			finally
 			{
@@ -119,30 +182,41 @@ namespace ICD.Common.Services
 			}
 		}
 
+		/// <summary>
+		/// Gets the service of the given type.
+		/// </summary>
+		/// <param name="tService"></param>
+		/// <returns></returns>
+		private object GetServiceInstance(Type tService)
+		{
+			if (tService == null)
+				throw new ArgumentNullException("tService");
+
+			object service = TryGetService(tService);
+			if (service != null)
+				return service;
+
+			throw new ServiceNotFoundException(tService);
+		}
+
+		/// <summary>
+		/// Adds the given service under the given type.
+		/// </summary>
+		/// <param name="tService"></param>
+		/// <param name="service"></param>
 		[PublicAPI]
 		private void AddServiceInstance(Type tService, object service)
 		{
-			m_ServicesSection.Enter();
-			m_Services[tService] = service;
-			m_ServicesSection.Leave();
-		}
+			if (tService == null)
+				throw new ArgumentNullException("tService");
 
-		#endregion
+			if (service == null)
+				throw new ArgumentNullException("service");
 
-		#region IDisposable
-
-		public void Dispose()
-		{
 			try
 			{
 				m_ServicesSection.Enter();
-				foreach (object service in m_Services.Values.Distinct())
-				{
-					if (!(service is IDisposable))
-						continue;
-					((IDisposable)service).Dispose();
-				}
-				m_Services.Clear();
+				m_Services.Add(tService, service);
 			}
 			finally
 			{
@@ -150,13 +224,6 @@ namespace ICD.Common.Services
 			}
 		}
 
-		public static void DisposeStatic()
-		{
-			if (s_Instance != null)
-				s_Instance.Dispose();
-			s_Instance = null;
-		}
-
 		#endregion
 	}
 }