Improve indexer health check messages (#1015)

* Improve indexer health check messages

Fixed: Improve health check message when all enabled indexers are disabled due to failures
Closes #1551

* Fixed: Health check failing and preventing others from running

* Fixed Indexer Health Checks and tests.

src/NzbDrone.Core/HealthCheck/Checks/IndexerSearchCheck.cs

@@ -0,0 +1,35 @@
+using System.Linq;
+using NzbDrone.Common.Extensions;
+using NzbDrone.Core.Indexers;
+
+namespace NzbDrone.Core.HealthCheck.Checks
+{
+    public class IndexerSearchCheck : HealthCheckBase
+    {
+        private readonly IIndexerFactory _indexerFactory;
+
+        public IndexerSearchCheck(IIndexerFactory indexerFactory)
+        {
+            _indexerFactory = indexerFactory;
+        }
+
+        public override HealthCheck Check()
+        {
+            var enabled = _indexerFactory.SearchEnabled(false);
+
+            if (enabled.Empty())
+            {
+                return new HealthCheck(GetType(), HealthCheckResult.Warning, "No indexers available with Search enabled, Sonarr will not provide any search results");
+            }
+
+            var active = _indexerFactory.SearchEnabled(true);
+
+            if (active.Empty())
+            {
+                return new HealthCheck(GetType(), HealthCheckResult.Warning, "All search-capable indexers are temporarily unavailable due to recent indexer errors");
+            }
+
+            return new HealthCheck(GetType());
+        }
+    }
+}