New: Health check for indexers with invalid download client

(cherry picked from commit 377fce6fe15c0875c4bd33f1371a31af79c9310c)

Closes #3959

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

@@ -0,0 +1,45 @@
+using System.Linq;
+using NzbDrone.Core.Download;
+using NzbDrone.Core.Indexers;
+using NzbDrone.Core.Localization;
+using NzbDrone.Core.ThingiProvider.Events;
+
+namespace NzbDrone.Core.HealthCheck.Checks
+{
+    [CheckOn(typeof(ProviderUpdatedEvent<IIndexer>))]
+    [CheckOn(typeof(ProviderDeletedEvent<IIndexer>))]
+    [CheckOn(typeof(ProviderUpdatedEvent<IDownloadClient>))]
+    [CheckOn(typeof(ProviderDeletedEvent<IDownloadClient>))]
+    public class IndexerDownloadClientCheck : HealthCheckBase
+    {
+        private readonly IIndexerFactory _indexerFactory;
+        private readonly IDownloadClientFactory _downloadClientFactory;
+
+        public IndexerDownloadClientCheck(IIndexerFactory indexerFactory,
+                                          IDownloadClientFactory downloadClientFactory,
+                                          ILocalizationService localizationService)
+            : base(localizationService)
+        {
+            _indexerFactory = indexerFactory;
+            _downloadClientFactory = downloadClientFactory;
+        }
+
+        public override HealthCheck Check()
+        {
+            var downloadClientsIds = _downloadClientFactory.All().Where(v => v.Enable).Select(v => v.Id).ToList();
+            var invalidIndexers = _indexerFactory.All()
+                .Where(v => v.Enable && v.DownloadClientId > 0 && !downloadClientsIds.Contains(v.DownloadClientId))
+                .ToList();
+
+            if (invalidIndexers.Any())
+            {
+                return new HealthCheck(GetType(),
+                    HealthCheckResult.Warning,
+                    string.Format(_localizationService.GetLocalizedString("IndexerDownloadClientHealthCheckMessage"), string.Join(", ", invalidIndexers.Select(v => v.Name).ToArray())),
+                    "#invalid-indexer-download-client-setting");
+            }
+
+            return new HealthCheck(GetType());
+        }
+    }
+}

src/NzbDrone.Core/Localization/Core/en.json

@@ -432,6 +432,7 @@
   "IncludeUnknownArtistItemsHelpText": "Show items without a artist in the queue, this could include removed artists, movies or anything else in Lidarr's category",
   "IncludeUnmonitored": "Include Unmonitored",
   "Indexer": "Indexer",
+  "IndexerDownloadClientHealthCheckMessage": "Indexers with invalid download clients: {0}.",
   "IndexerDownloadClientHelpText": "Specify which download client is used for grabs from this indexer",
   "IndexerIdHelpText": "Specify what indexer the profile applies to",
   "IndexerIdHelpTextWarning": "Using a specific indexer with preferred words can lead to duplicate releases being grabbed",