Provider Data on item and NeedsRefresh functionality for providers

MediaBrowser.Controller/Providers/BaseMetadataProvider.cs

@@ -1,11 +1,23 @@
 using MediaBrowser.Controller.Entities;
 using MediaBrowser.Controller.Library;
+using MediaBrowser.Common.Extensions;
 using System.Threading.Tasks;
+using System;
 
 namespace MediaBrowser.Controller.Providers
 {
     public abstract class BaseMetadataProvider
     {
+        protected Guid _id;
+        public virtual Guid Id
+        {
+            get
+            {
+                if (_id == null) _id = this.GetType().FullName.GetMD5();
+                return _id;
+            }
+        }
+
         public abstract bool Supports(BaseEntity item);
 
         public virtual bool RequiresInternet
@@ -16,6 +28,49 @@ namespace MediaBrowser.Controller.Providers
             }
         }
 
+        /// <summary>
+        /// Returns the last refresh time of this provider for this item. Providers that care should
+        /// call SetLastRefreshed to update this value.
+        /// </summary>
+        /// <param name="item"></param>
+        /// <returns></returns>
+        protected virtual DateTime LastRefreshed(BaseEntity item)
+        {
+            return (item.ProviderData[this.Id] ?? new BaseProviderInfo()).LastRefreshed;
+        }
+
+        /// <summary>
+        /// Sets the persisted last refresh date on the item for this provider.
+        /// </summary>
+        /// <param name="item"></param>
+        /// <param name="value"></param>
+        protected virtual void SetLastRefreshed(BaseEntity item, DateTime value)
+        {
+            var data = item.ProviderData[this.Id] ?? new BaseProviderInfo();
+            data.LastRefreshed = value;
+            item.ProviderData[this.Id] = data;
+        }
+
+        /// <summary>
+        /// Returns whether or not this provider should be re-fetched.  Default functionality can
+        /// compare a provided date with a last refresh time.  This can be overridden for more complex
+        /// determinations.
+        /// </summary>
+        /// <returns></returns>
+        public virtual bool NeedsRefresh(BaseEntity item)
+        {
+            return CompareDate(item) > LastRefreshed(item);
+        }
+
+        /// <summary>
+        /// Override this to return the date that should be compared to the last refresh date
+        /// to determine if this provider should be re-fetched.
+        /// </summary>
+        protected virtual DateTime CompareDate(BaseEntity item)
+        {
+            return DateTime.MinValue;
+        }
+            
         public abstract Task FetchAsync(BaseEntity item, ItemResolveEventArgs args);
 
         public abstract MetadataProviderPriority Priority { get; }