//===================================================================================

// Microsoft patterns & practices

// Composite Application Guidance for Windows Presentation Foundation and Silverlight

//===================================================================================

// Copyright (c) Microsoft Corporation.  All rights reserved.

// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY

// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT

// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

// FITNESS FOR A PARTICULAR PURPOSE.

//===================================================================================

// The example companies, organizations, products, domain names,

// e-mail addresses, logos, people, places, and events depicted

// herein are fictitious.  No association with any real company,

// organization, product, domain name, email address, logo, person,

// places, or events is intended or should be inferred.

//===================================================================================

using System;

using System.ComponentModel;

using System.Windows;

using Microsoft.Practices.Composite.Presentation.Properties;

using Microsoft.Practices.Composite.Regions;



namespace Microsoft.Practices.Composite.Presentation.Regions.Behaviors

{

    /// <summary>

    /// Subscribes to a static event from the <see cref="RegionManager"/> in order to register the target <see cref="IRegion"/>

    /// in a <see cref="IRegionManager"/> when one is available on the host control by walking up the tree and finding

    /// a control whose <see cref="RegionManager.RegionManagerProperty"/> property is not <see langword="null"/>.

    /// </summary>

    public class RegionManagerRegistrationBehavior : RegionBehavior, IHostAwareRegionBehavior

    {

        /// <summary>

        /// The key of this behavior.

        /// </summary>

        public static readonly string BehaviorKey = "RegionManagerRegistration";



        private WeakReference attachedRegionManagerWeakReference;

        private DependencyObject hostControl;



        /// <summary>

        /// Initializes a new instance of <see cref="RegionManagerRegistrationBehavior"/>.

        /// </summary>

        public RegionManagerRegistrationBehavior()

        {

            this.RegionManagerAccessor = new DefaultRegionManagerAccessor();

        }



        /// <summary>

        /// Provides an abstraction on top of the RegionManager static members.

        /// </summary>

        public IRegionManagerAccessor RegionManagerAccessor { get; set; }



        /// <summary>

        /// Gets or sets the <see cref="DependencyObject"/> that the <see cref="IRegion"/> is attached to.

        /// </summary>

        /// <value>A <see cref="DependencyObject"/> that the <see cref="IRegion"/> is attached to.

        /// This is usually a <see cref="FrameworkElement"/> that is part of the tree.</value>

        /// <exception cref="InvalidOperationException">When this member is set after the <see cref="IRegionBehavior.Attach"/> method has being called.</exception>

        public DependencyObject HostControl

        {

            get

            {

                return hostControl;

            }

            set

            {

                if (IsAttached)

                {

                    throw new InvalidOperationException(Resources.HostControlCannotBeSetAfterAttach);

                }

                this.hostControl = value;

            }

        }



        /// <summary>

        /// When the <see cref="IRegion"/> has a name assigned, the behavior will start monitoring the ancestor controls in the element tree

        /// to look for an <see cref="IRegionManager"/> where to register the region in.

        /// </summary>

        protected override void OnAttach()

        {

            if (string.IsNullOrEmpty(this.Region.Name))

            {

                this.Region.PropertyChanged += this.Region_PropertyChanged;

            }

            else

            {

                this.StartMonitoringRegionManager();

            }

        }



        private void Region_PropertyChanged(object sender, PropertyChangedEventArgs e)

        {

            if (e.PropertyName == "Name" && !string.IsNullOrEmpty(this.Region.Name))

            {

                this.Region.PropertyChanged -= this.Region_PropertyChanged;

                this.StartMonitoringRegionManager();

            }

        }



        private void StartMonitoringRegionManager()

        {

            this.RegionManagerAccessor.UpdatingRegions += this.OnUpdatingRegions;

            this.TryRegisterRegion();

        }



        private void TryRegisterRegion()

        {

            DependencyObject targetElement = this.HostControl;

            if (targetElement.CheckAccess())

            {

                IRegionManager regionManager = this.FindRegionManager(targetElement);



                IRegionManager attachedRegionManager = this.GetAttachedRegionManager();



                if (regionManager != attachedRegionManager)

                {

                    if (attachedRegionManager != null)

                    {

                        this.attachedRegionManagerWeakReference = null;

                        attachedRegionManager.Regions.Remove(this.Region.Name);

                    }



                    if (regionManager != null)

                    {

                        this.attachedRegionManagerWeakReference = new WeakReference(regionManager);



                        regionManager.Regions.Add(this.Region);

                    }

                }

            }

        }



        /// <summary>

        /// This event handler gets called when a RegionManager is requering the instances of a region to be registered if they are not already.

        /// <remarks>Although this is a public method to support Weak Delegates in Silverlight, it should not be called by the user.</remarks>

        /// </summary>

        /// <param name="sender">The sender.</param>

        /// <param name="e">The arguments.</param>

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2109:ReviewVisibleEventHandlers", Justification = "This has to be public in order to work with weak references in partial trust or Silverlight environments.")]

        public void OnUpdatingRegions(object sender, EventArgs e)

        {

            this.TryRegisterRegion();

        }



        private IRegionManager FindRegionManager(DependencyObject dependencyObject)

        {

            var regionmanager = this.RegionManagerAccessor.GetRegionManager(dependencyObject);

            if (regionmanager != null)

            {

                return regionmanager;

            }



            DependencyObject parent = null;

#if SILVERLIGHT

            //parent = System.Windows.Media.VisualTreeHelper.GetParent(dependencyObject);

                    FrameworkElement frameworkElement = dependencyObject as FrameworkElement;

                    if (frameworkElement != null)

                    {

                        parent = frameworkElement.Parent;

                    }

#else

            parent = LogicalTreeHelper.GetParent(dependencyObject);

#endif

            if (parent != null)

            {

                return this.FindRegionManager(parent);

            }



            return null;

        }



        private IRegionManager GetAttachedRegionManager()

        {

            if (this.attachedRegionManagerWeakReference != null)

            {

                return this.attachedRegionManagerWeakReference.Target as IRegionManager;

            }



            return null;

        }

    }

}