Pushing missing changes

MediaBrowser.UI/ViewModels/ItemCollectionViewModel.cs

@@ -0,0 +1,158 @@
+using MediaBrowser.Model.DTO;
+using System;
+using System.Threading;
+using System.Windows;
+
+namespace MediaBrowser.UI.ViewModels
+{
+    /// <summary>
+    /// Represents a view model that contains multiple items.
+    /// This should be used if you want to display a button or list item that holds more than one item, 
+    /// and cycle through them periodically.
+    /// </summary>
+    public class ItemCollectionViewModel : BaseViewModel, IDisposable
+    {
+        private int RotationPeriodMs { get; set; }
+
+        public ItemCollectionViewModel(int rotationPeriodMs = 10000, int rotationDevaiationMs = 2000)
+            : base()
+        {
+            if (rotationDevaiationMs > 0)
+            {
+                rotationPeriodMs += new Random(Guid.NewGuid().GetHashCode()).Next(0 - rotationDevaiationMs, rotationDevaiationMs);
+            }
+
+            RotationPeriodMs = rotationPeriodMs;
+        }
+
+        /// <summary>
+        /// Gets the timer that updates the current item
+        /// </summary>
+        private Timer CurrentItemTimer { get; set; }
+
+        private string _name;
+        /// <summary>
+        /// Gets or sets the name of the collection
+        /// </summary>
+        public string Name
+        {
+            get { return _name; }
+            set
+            {
+                _name = value;
+                OnPropertyChanged("Name");
+            }
+        }
+
+        private DtoBaseItem[] _items;
+        /// <summary>
+        /// Gets or sets the list of items
+        /// </summary>
+        public DtoBaseItem[] Items
+        {
+            get { return _items; }
+            set
+            {
+                _items = value ?? new DtoBaseItem[] { };
+                OnPropertyChanged("Items");
+                CurrentItemIndex = Items.Length == 0 ? -1 : 0;
+
+                ReloadTimer();
+            }
+        }
+
+        private int _currentItemIndex;
+        /// <summary>
+        /// Gets or sets the index of the current item
+        /// </summary>
+        public int CurrentItemIndex
+        {
+            get { return _currentItemIndex; }
+            set
+            {
+                _currentItemIndex = value;
+                OnPropertyChanged("CurrentItemIndex");
+                OnPropertyChanged("CurrentItem");
+                OnPropertyChanged("NextItem");
+            }
+        }
+
+        /// <summary>
+        /// Gets the current item
+        /// </summary>
+        public DtoBaseItem CurrentItem
+        {
+            get { return CurrentItemIndex == -1 ? null : Items[CurrentItemIndex]; }
+        }
+
+        /// <summary>
+        /// Gets the next item
+        /// </summary>
+        public DtoBaseItem NextItem
+        {
+            get
+            {
+                if (CurrentItem == null || CurrentItemIndex == -1)
+                {
+                    return null;
+                }
+                var index = CurrentItemIndex + 1;
+
+                if (index >= Items.Length)
+                {
+                    index = 0;
+                }
+
+                return Items[index];
+            }
+        }
+
+        /// <summary>
+        /// Disposes the timer
+        /// </summary>
+        private void DisposeTimer()
+        {
+            if (CurrentItemTimer != null)
+            {
+                CurrentItemTimer.Dispose();
+            }
+        }
+
+        /// <summary>
+        /// Reloads the timer
+        /// </summary>
+        private void ReloadTimer()
+        {
+            DisposeTimer();
+
+            // Don't bother unless there's at least two items
+            if (Items.Length > 1)
+            {
+                CurrentItemTimer = new Timer(state => Application.Current.Dispatcher.InvokeAsync(IncrementCurrentItemIndex), null, RotationPeriodMs, RotationPeriodMs);
+            }
+        }
+
+        /// <summary>
+        /// Increments current item index, or resets it back to zero if we're at the end of the list
+        /// </summary>
+        private void IncrementCurrentItemIndex()
+        {
+            var newIndex = CurrentItemIndex + 1;
+
+            if (newIndex >= Items.Length)
+            {
+                newIndex = 0;
+            }
+
+            CurrentItemIndex = newIndex;
+        }
+
+        /// <summary>
+        /// Disposes the collection
+        /// </summary>
+        public void Dispose()
+        {
+            DisposeTimer();
+        }
+    }
+}