Catel - Part 4 of n: Unit testing with Catel

// --------------------------------------------------------------------------------------------------------------------
// <copyright file="ViewModelServiceManager.cs" company="Catel development team">
//   Copyright (c) 2008 - 2011 Catel development team. All rights reserved.
// </copyright>
// <summary>
//   Class that manages services available to view models.
// </summary>
// --------------------------------------------------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using Catel.Properties;

namespace Catel.MVVM.Services
{
	/// <summary>
	/// Class that manages services available to view models.
	/// </summary>
	public class ViewModelServiceManager : IServiceProvider
	{
		#region Variables
        /// <summary>
        /// Dictionary of services registered with this view model service manager.
        /// </summary>
		private readonly Dictionary<Type, object> _services = new Dictionary<Type, object>();

        /// <summary>
        /// Lock object for the services.
        /// </summary>
		private readonly object _servicesLock = new object();
		#endregion

		#region Constructor & destructor
        /// <summary>
        /// Initializes a new instance of the <see cref="ViewModelServiceManager"/> class.
        /// </summary>
        /// <remarks>
        /// For internal use only.
        /// </remarks>
        internal ViewModelServiceManager()
        {
        }
		#endregion

		#region Properties
		#endregion

		#region Methods
		/// <summary>
		/// Clears the services.
		/// </summary>
		public void Clear()
		{
			lock (_servicesLock)
			{
				_services.Clear();
			}
		}

		/// <summary>
		/// Adds a new service.
		/// </summary>
		/// <param name="serviceType">Type of the service.</param>
		/// <param name="serviceInstance">The service instance.</param>
		public void Add(Type serviceType, object serviceInstance)
		{
			if (serviceType == null)
			{
			    throw new ArgumentNullException("serviceType");
			}

			if (serviceInstance == null)
			{
			    throw new ArgumentNullException("serviceInstance");
			}

			lock (_servicesLock)
			{
				_services[serviceType] = serviceInstance;
			}
		}

		/// <summary>
		/// Removes the specified service.
		/// </summary>
		/// <param name="serviceType">Type of the service.</param>
		public void Remove(Type serviceType)
		{
			if (serviceType == null)
			{
			    throw new ArgumentNullException("serviceType");
			}

			lock (_servicesLock)
			{
				_services.Remove(serviceType);
			}
		}
		#endregion

		#region IServiceProvider Members
		/// <summary>
		/// Gets the service object of the specified type.
		/// </summary>
		/// <param name="serviceType">An object that specifies the type of service object to get.</param>
		/// <returns>
		/// A service object of type <paramref name="serviceType"/>.
		/// -or-
		/// null if there is no service object of type <paramref name="serviceType"/>.
		/// </returns>
		public object GetService(Type serviceType)
		{
			if (serviceType == null)
			{
			    throw new ArgumentNullException("serviceType");
			}

            if (!serviceType.IsInterface)
            {
                throw new ArgumentException(Exceptions.ParameterMustBeAnInterface, "serviceType");
            }

			lock (_servicesLock)
			{
				return _services.ContainsKey(serviceType) ? _services[serviceType] : null;
			}
		}

		/// <summary>
		/// Gets the service object of the specified type.
		/// </summary>
		/// <typeparam name="T">Type of the service to retrieve.</typeparam>
		/// <returns>
		/// A service object of the specified parameter type.
		/// -or-
		/// null if there is no service object of the specified parameter type.
		/// </returns>
		public T GetService<T>()
		{
			return (T)GetService(typeof(T));
		}
		#endregion
	}
}