Added tiered indexer requests to support fallback to wildcard queries.

src/NzbDrone.Core/Indexers/IndexerPageableRequestChain.cs

@@ -0,0 +1,51 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace NzbDrone.Core.Indexers
+{
+    public class IndexerPageableRequestChain
+    {
+        private List<List<IndexerPageableRequest>> _chains;
+
+        public IndexerPageableRequestChain()
+        {
+            _chains = new List<List<IndexerPageableRequest>>();
+            _chains.Add(new List<IndexerPageableRequest>());
+        }
+
+        public int Tiers
+        {
+            get { return _chains.Count; }
+        }
+
+        public IEnumerable<IndexerPageableRequest> GetAllTiers()
+        {
+            return _chains.SelectMany(v => v);
+        }
+
+        public IEnumerable<IndexerPageableRequest> GetTier(int index)
+        {
+            return _chains[index];
+        }
+
+        public void Add(IEnumerable<IndexerRequest> request)
+        {
+            if (request == null) return;
+
+            _chains.Last().Add(new IndexerPageableRequest(request));
+        }
+
+        public void AddTier(IEnumerable<IndexerRequest> request)
+        {
+            AddTier();
+            Add(request);
+        }
+
+        public void AddTier()
+        {
+            if (_chains.Last().Count == 0) return;
+
+            _chains.Add(new List<IndexerPageableRequest>());
+        }
+    }
+}