Async HttpClient and list lookup

src/NzbDrone.Common/TPL/RateLimitService.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Concurrent;
+using System.Threading.Tasks;
 using NLog;
 using NzbDrone.Common.Cache;
 
@@ -8,6 +9,7 @@ namespace NzbDrone.Common.TPL
     public interface IRateLimitService
     {
         void WaitAndPulse(string key, TimeSpan interval);
+        Task WaitAndPulseAsync(string key, TimeSpan interval);
     }
 
     public class RateLimitService : IRateLimitService
@@ -23,13 +25,7 @@ namespace NzbDrone.Common.TPL
 
         public void WaitAndPulse(string key, TimeSpan interval)
         {
-            var waitUntil = _rateLimitStore.AddOrUpdate(key,
-                (s) => DateTime.UtcNow + interval,
-                (s, i) => new DateTime(Math.Max(DateTime.UtcNow.Ticks, i.Ticks), DateTimeKind.Utc) + interval);
-
-            waitUntil -= interval;
-
-            var delay = waitUntil - DateTime.UtcNow;
+            var delay = GetDelay(key, interval);
 
             if (delay.TotalSeconds > 0.0)
             {
@@ -37,5 +33,27 @@ namespace NzbDrone.Common.TPL
                 System.Threading.Thread.Sleep(delay);
             }
         }
+
+        public async Task WaitAndPulseAsync(string key, TimeSpan interval)
+        {
+            var delay = GetDelay(key, interval);
+
+            if (delay.TotalSeconds > 0.0)
+            {
+                _logger.Trace("Rate Limit triggered, delaying '{0}' for {1:0.000} sec", key, delay.TotalSeconds);
+                await Task.Delay(delay);
+            }
+        }
+
+        private TimeSpan GetDelay(string key, TimeSpan interval)
+        {
+            var waitUntil = _rateLimitStore.AddOrUpdate(key,
+                (s) => DateTime.UtcNow + interval,
+                (s, i) => new DateTime(Math.Max(DateTime.UtcNow.Ticks, i.Ticks), DateTimeKind.Utc) + interval);
+
+            waitUntil -= interval;
+
+            return waitUntil - DateTime.UtcNow;
+        }
     }
 }