Added item identity providers and converters

MediaBrowser.Controller/Providers/ItemIdentities.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MediaBrowser.Controller.Providers
+{
+    public interface IItemIdentity
+    {
+        string Type { get; }
+    }
+
+    public interface IHasIdentities<out TIdentity>
+        where TIdentity : IItemIdentity
+    {
+        IEnumerable<TIdentity> Identities { get; }
+
+        Task FindIdentities(IProviderManager providerManager, CancellationToken cancellationToken);
+    }
+
+    public interface IItemIdentityProvider : IHasOrder { }
+
+    public interface IItemIdentityProvider<in TLookupInfo, TIdentity> : IItemIdentityProvider
+        where TLookupInfo : ItemLookupInfo
+        where TIdentity : IItemIdentity
+    {
+        Task<TIdentity> FindIdentity(TLookupInfo info);
+    }
+
+    public interface IItemIdentityConverter : IHasOrder { }
+
+    public interface IItemIdentityConverter<TIdentity> : IItemIdentityConverter
+        where TIdentity : IItemIdentity
+    {
+        Task<TIdentity> Convert(TIdentity identity);
+
+        string SourceType { get; }
+
+        string ResultType { get; }
+    }
+}