Catel - Part 4 of n: Unit testing with Catel

// --------------------------------------------------------------------------------------------------------------------
// <copyright file="ManagedViewModel.cs" company="Catel development team">
//   Copyright (c) 2008 - 2011 Catel development team. All rights reserved.
// </copyright>
// <summary>
//   Represents a managed view model. A managed view model is watched for property changes. As soon as a change occurs in one of the
//   managed view models, all other interested view models are notified of the changes.
// </summary>
// --------------------------------------------------------------------------------------------------------------------

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

namespace Catel.MVVM
{
	/// <summary>
	/// Represents a managed view model. A managed view model is watched for property changes. As soon as a change occurs in one of the
	/// managed view models, all other interested view models are notified of the changes.
	/// </summary>
	internal class ManagedViewModel
	{
		#region Variables
        /// <summary>
        /// The <see cref="ILog">log</see> object.
        /// </summary>
		private static readonly ILog Log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        /// <summary>
        /// List of alive view model instances.
        /// </summary>
        private readonly List<IViewModel> _viewModelInstances = new List<IViewModel>();

        /// <summary>
        /// List of alive view model instances that are interested in other view models.
        /// </summary>
        private readonly List<IViewModel> _interestedViewModels = new List<IViewModel>();
		#endregion

		#region Constructor & destructor
		/// <summary>
		/// Initializes a new instance of the <see cref="ManagedViewModel"/> class.
		/// </summary>
		/// <param name="viewModelType">Type of the view model.</param>
		public ManagedViewModel(Type viewModelType)
		{
			ViewModelType = viewModelType;
		}
		#endregion

		#region Properties
		/// <summary>
		/// Gets the type of the view model.
		/// </summary>
		/// <value>The type of the view model.</value>
		public Type ViewModelType { get; private set; }
		#endregion

		#region Methods
		/// <summary>
		/// Adds a view model instance to the list of instances.
		/// </summary>
		/// <param name="viewModel">The view model instance to add.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
		/// <exception cref="WrongViewModelTypeException">When <paramref name="viewModel"/> is not of the right type.</exception>
        public void AddViewModelInstance(IViewModel viewModel)
		{
			if (viewModel == null)
			{
			    throw new ArgumentNullException("viewModel");
			}

			if (viewModel.GetType() != ViewModelType)
			{
			    throw new WrongViewModelTypeException(viewModel.GetType(), ViewModelType);
			}

			lock (_viewModelInstances)
			{
				if (!_viewModelInstances.Contains(viewModel))
				{
					_viewModelInstances.Add(viewModel);

					viewModel.PropertyChanged += ViewModel_PropertyChanged;

					Log.Debug(TraceMessages.AddedViewModelInstance, _viewModelInstances.Count, ViewModelType);
				}
			}
		}

		/// <summary>
		/// Removes a view model instance from the list of instances.
		/// </summary>
		/// <param name="viewModel">The view model instance to remove.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        public void RemoveViewModelInstance(IViewModel viewModel)
		{
			if (viewModel == null)
			{
			    throw new ArgumentNullException("viewModel");
			}

			lock (_viewModelInstances)
			{
				viewModel.PropertyChanged -= ViewModel_PropertyChanged;

				_viewModelInstances.Remove(viewModel);

				Log.Debug(TraceMessages.RemovedViewModelInstance, _viewModelInstances.Count, ViewModelType);
			}
		}

		/// <summary>
		/// Adds a view model to the list of interested view models for this view model type.
		/// </summary>
		/// <param name="viewModel">The view model instance that is interested in changes.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        public void AddInterestedViewModel(IViewModel viewModel)
		{
			if (viewModel == null)
			{
			    throw new ArgumentNullException("viewModel");
			}

			lock (_interestedViewModels)
			{
				_interestedViewModels.Add(viewModel);

				viewModel.Closed += InterestedViewModel_Closed;

				Log.Debug(TraceMessages.AddedInterestedViewModel, viewModel.GetType(), ViewModelType, _interestedViewModels.Count);
			}
		}

		/// <summary>
		/// Removes a view model from the list of interested view models for this view model type.
		/// </summary>
		/// <param name="viewModel">The view model instance that is interested in changes.</param>
		/// <exception cref="ArgumentNullException">When <paramref name="viewModel"/> is <c>null</c>.</exception>
        public void RemoveInterestedViewModel(IViewModel viewModel)
		{
			if (viewModel == null)
			{
			    throw new ArgumentNullException("viewModel");
			}

			lock (_interestedViewModels)
			{
				viewModel.Closed -= InterestedViewModel_Closed;

				_interestedViewModels.Remove(viewModel);

				Log.Debug(TraceMessages.RemovedInterestedViewModel, viewModel.GetType(), ViewModelType, _interestedViewModels.Count);
			}
		}

		/// <summary>
		/// Handles the PropertyChanged event of the ViewModel instances.
		/// </summary>
		/// <param name="sender">The source of the event.</param>
		/// <param name="e">The <see cref="System.ComponentModel.PropertyChangedEventArgs"/> instance containing the event data.</param>
		private void ViewModel_PropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			lock (_interestedViewModels)
			{
				foreach (ViewModelBaseWithoutServices viewModel in _interestedViewModels)
				{
					try
					{
						viewModel.ViewModelPropertyChanged((IViewModel)sender, e.PropertyName);
					}
					catch (Exception ex)
					{
						Log.Error(ex, TraceMessages.FailedToInformInterestedViewModelOfAViewModelChange);
					}	
				}
			}
		}

		/// <summary>
		/// Handles the Closed event of the InterestedViewModel instances.
		/// </summary>
		/// <param name="sender">The source of the event.</param>
		/// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param>
		private void InterestedViewModel_Closed(object sender, EventArgs e)
		{
            RemoveInterestedViewModel((IViewModel)sender);
		}
		#endregion
	}
}