Catel - Part 4 of n: Unit testing with Catel

// --------------------------------------------------------------------------------------------------------------------
// <copyright file="ViewModelManager.cs" company="Catel development team">
//   Copyright (c) 2008 - 2011 Catel development team. All rights reserved.
// </copyright>
// <summary>
//   Manager for view models. Thanks to this manager, it is possible to subscribe to other view models and be able to respond
//   correctly to property changes in other views.
// </summary>
// --------------------------------------------------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using Catel.Properties;
using log4net;

namespace Catel.MVVM
{
	/// <summary>
	/// Manager for view models. Thanks to this manager, it is possible to subscribe to other view models and be able to respond
	/// correctly to property changes in other views.
	/// </summary>
	public class ViewModelManager
	{
		#region Variables
        /// <summary>
        /// The <see cref="ILog">log</see> object.
        /// </summary>
		private static readonly ILog Log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        /// <summary>
        /// Dictionary containing all the managed view models by this view model manager.
        /// </summary>
		private readonly Dictionary<Type, ManagedViewModel> _managedViewModels = new Dictionary<Type, ManagedViewModel>();
		#endregion

		#region Constructor & destructor
		/// <summary>
		/// Initializes a new instance of the <see cref="ViewModelManager"/> class.
		/// </summary>
		/// <remarks>
		/// The constructor is private because this is a singleton class.
		/// </remarks>
		internal ViewModelManager()
		{
			Log.Debug(TraceMessages.InstantiatedViewModelManager);
		}
		#endregion

		#region Properties
		#endregion

		#region Methods
		/// <summary>
		/// Registers a view model instance with the manager. All view models must register themselves to the manager.
		/// </summary>
		/// <param name="viewModel">The view model to register.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
		internal void RegisterViewModelInstance(IViewModel viewModel)
		{
			RegisterViewModelInstanceInternal(viewModel);
		}

		/// <summary>
		/// Registers a view model instance with the manager. All view models must register themselves to the manager.
		/// </summary>
		/// <param name="viewModel">The view model to register.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        private void RegisterViewModelInstanceInternal(IViewModel viewModel)
		{
			if (viewModel == null)
			{
			    throw new ArgumentNullException("viewModel");
			}

			var managedViewModel = GetManagedViewModel(viewModel.GetType());
			managedViewModel.AddViewModelInstance(viewModel);
		}

		/// <summary>
		/// Unregisters a view model instance from the manager. All view models must unregister themselves from the manager.
		/// </summary>
		/// <param name="viewModel">The view model to unregister.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        internal void UnregisterViewModelInstance(IViewModel viewModel)
		{
			UnregisterViewModelInstanceInternal(viewModel);
		}

		/// <summary>
		/// Unregisters a view model instance from the manager. All view models must unregister themselves from the manager.
		/// </summary>
		/// <param name="viewModel">The view model to unregister.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        private void UnregisterViewModelInstanceInternal(IViewModel viewModel)
		{
			if (viewModel == null)
			{
			    throw new ArgumentNullException("viewModel");
			}

			var managedViewModel = GetManagedViewModel(viewModel.GetType());
			managedViewModel.RemoveViewModelInstance(viewModel);
		}

		/// <summary>
        /// Adds an interested view model instance. The <see cref="IViewModel"/> class will automatically register
		/// itself to the manager by using this method when decorated with the <see cref="InterestedInAttribute"/>.
		/// </summary>
		/// <param name="viewModelType">Type of the view model the <paramref name="viewModel"/> is interested in.</param>
		/// <param name="viewModel">The view model instance.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModelType"/> is <c>null</c>.</exception>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        internal void AddInterestedViewModel(Type viewModelType, IViewModel viewModel)
		{
			AddInterestedViewModelInstanceInternal(viewModelType, viewModel);
		}

		/// <summary>
        /// Adds an interested view model instance. The <see cref="IViewModel"/> class will automatically register
		/// itself to the manager by using this method when decorated with the <see cref="InterestedInAttribute"/>.
		/// </summary>
		/// <param name="viewModelType">Type of the view model the <paramref name="viewModel"/> is interested in.</param>
		/// <param name="viewModel">The view model instance.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModelType"/> is <c>null</c>.</exception>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        private void AddInterestedViewModelInstanceInternal(Type viewModelType, IViewModel viewModel)
		{
			if (viewModel == null)
			{
			    throw new ArgumentNullException("viewModel");
			}

			var managedViewModel = GetManagedViewModel(viewModelType);
			managedViewModel.AddInterestedViewModel(viewModel);
		}

		/// <summary>
        /// Removes an interested view model instance. The <see cref="IViewModel"/> class will automatically unregister
		/// itself from the manager by using this method when decorated with the <see cref="InterestedInAttribute"/>.
		/// </summary>
		/// <param name="viewModelType">Type of the view model the <paramref name="viewModel"/> was interested in.</param>
		/// <param name="viewModel">The view model instance.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModelType"/> is <c>null</c>.</exception>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        internal void RemoveInterestedViewModelInstance(Type viewModelType, IViewModel viewModel)
		{
			RemoveInterestedViewModelInstanceInternal(viewModelType, viewModel);
		}

		/// <summary>
        /// Removes an interested view model instance. The <see cref="IViewModel"/> class will automatically unregister
		/// itself from the manager by using this method when decorated with the <see cref="InterestedInAttribute"/>.
		/// </summary>
		/// <param name="viewModelType">Type of the view model the <paramref name="viewModel"/> was interested in.</param>
		/// <param name="viewModel">The view model instance.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModelType"/> is <c>null</c>.</exception>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        private void RemoveInterestedViewModelInstanceInternal(Type viewModelType, IViewModel viewModel)
		{
			if (viewModelType == null)
			{
			    throw new ArgumentNullException("viewModelType");
			}

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

			var managedViewModel = GetManagedViewModel(viewModelType);
			managedViewModel.RemoveInterestedViewModel(viewModel);
		}

		/// <summary>
		/// Gets the managed view model for a specific view model type.
		/// </summary>
		/// <param name="viewModelType">Type of the view model.</param>
		/// <returns>The <see cref="ManagedViewModel"/> of the specified type.</returns>
		private ManagedViewModel GetManagedViewModel(Type viewModelType)
		{
			lock (_managedViewModels)
			{
				if (!_managedViewModels.ContainsKey(viewModelType))
				{
					_managedViewModels.Add(viewModelType, new ManagedViewModel(viewModelType));
				}

				return _managedViewModels[viewModelType];
			}
		}
		#endregion
	}
}