New: Show health warning if system time is off expected time

Co-Authored-By: Mark McDowall <markus101@users.noreply.github.com>

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

@@ -0,0 +1,49 @@
+using System;
+using NLog;
+using NzbDrone.Common.Cloud;
+using NzbDrone.Common.Http;
+using NzbDrone.Common.Serializer;
+using NzbDrone.Core.Localization;
+
+namespace NzbDrone.Core.HealthCheck.Checks
+{
+    public class SystemTimeCheck : HealthCheckBase
+    {
+        private readonly IHttpClient _client;
+        private readonly IHttpRequestBuilderFactory _cloudRequestBuilder;
+        private readonly Logger _logger;
+
+        public SystemTimeCheck(IHttpClient client, IRadarrCloudRequestBuilder cloudRequestBuilder, ILocalizationService localizationService, Logger logger)
+            : base(localizationService)
+        {
+            _client = client;
+            _cloudRequestBuilder = cloudRequestBuilder.Services;
+            _logger = logger;
+        }
+
+        public override HealthCheck Check()
+        {
+            var request = _cloudRequestBuilder.Create()
+                                              .Resource("/time")
+                                              .Build();
+
+            var response = _client.Execute(request);
+            var result = Json.Deserialize<ServiceTimeResponse>(response.Content);
+            var systemTime = DateTime.UtcNow;
+
+            // +/- more than 1 day
+            if (Math.Abs(result.DateTimeUtc.Subtract(systemTime).TotalDays) >= 1)
+            {
+                _logger.Error("System time mismatch. SystemTime: {0} Expected Time: {1}. Update system time", systemTime, result.DateTimeUtc);
+                return new HealthCheck(GetType(), HealthCheckResult.Error, _localizationService.GetLocalizedString("SystemTimeCheckMessage"));
+            }
+
+            return new HealthCheck(GetType());
+        }
+    }
+
+    public class ServiceTimeResponse
+    {
+        public DateTime DateTimeUtc { get; set; }
+    }
+}