Allows parallel actions call

RateLimiter/CallCountByIntervalAwaitableConstraint.cs

@@ -0,0 +1,121 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace RateLimiter
+{
+    /// <summary>
+    /// Provide an awaitable constraint based on number of times per duration
+    /// </summary>
+    public class CallCountByIntervalAwaitableConstraint : IAwaitableConstraint
+    {
+        /// <summary>
+        /// List of the last time stamps
+        /// </summary>
+        public IReadOnlyList<DateTime> TimeStamps => _TimeStamps.ToList();
+
+        /// <summary>
+        /// Stack of the last time stamps
+        /// </summary>
+        protected LimitedSizeStack<DateTime> _TimeStamps { get; }
+
+        private int _Count { get; }
+        private TimeSpan _TimeSpan { get; }
+        private SemaphoreSlim _Semaphore { get; } = new SemaphoreSlim(1, 1);
+        private ITime _Time { get; }
+
+        /// <summary>
+        /// Constructs a new AwaitableConstraint based on number of times per duration
+        /// </summary>
+        /// <param name="count"></param>
+        /// <param name="timeSpan"></param>
+        public CallCountByIntervalAwaitableConstraint(int count, TimeSpan timeSpan) : this(count, timeSpan, TimeSystem.StandardTime)
+        {
+        }
+
+        internal CallCountByIntervalAwaitableConstraint(int count, TimeSpan timeSpan, ITime time)
+        {
+            if (count <= 0)
+                throw new ArgumentException("count should be strictly positive", nameof(count));
+
+            if (timeSpan.TotalMilliseconds <= 0)
+                throw new ArgumentException("timeSpan should be strictly positive", nameof(timeSpan));
+
+            _Count = count;
+            _TimeSpan = timeSpan;
+            _TimeStamps = new LimitedSizeStack<DateTime>(_Count);
+            _Time = time;
+        }
+
+        /// <summary>
+        /// returns a task that will complete once the constraint is fulfilled
+        /// </summary>
+        /// <param name="cancellationToken">
+        /// Cancel the wait
+        /// </param>
+        /// <returns>
+        /// A disposable that should be disposed upon task completion
+        /// </returns>
+        public async Task<IDisposable> WaitForReadiness(CancellationToken cancellationToken)
+        {
+            try
+            {
+
+                await _Semaphore.WaitAsync(cancellationToken);
+                var count = 0;
+                var now = _Time.GetNow();
+                var target = now - _TimeSpan;
+                LinkedListNode<DateTime> element = _TimeStamps.First, last = null;
+                while ((element != null) && (element.Value > target))
+                {
+                    last = element;
+                    element = element.Next;
+                    count++;
+                }
+
+                if (count >= _Count)
+                {
+                    var timeToWait = last.Value.Add(_TimeSpan) - now;
+                    now = now.Add(timeToWait);
+                    Debug.Assert(element == null);
+                    Debug.Assert(last != null);
+                    await _Time.GetDelay(timeToWait, cancellationToken);
+                }
+                _TimeStamps.Push(now);
+                _Semaphore.Release();
+
+                return new DisposeAction(OnEnded);
+            }
+            catch (Exception)
+            {
+                _Semaphore.Release();
+                throw;
+            }
+        }
+
+        /// <summary>
+        /// Clone CallCountByIntervalAwaitableConstraint
+        /// </summary>
+        /// <returns></returns>
+        public IAwaitableConstraint Clone()
+        {
+            return new CallCountByIntervalAwaitableConstraint(_Count, _TimeSpan, _Time);
+        }
+
+        private void OnEnded()
+        {
+            OnEnded(TimeSystem.StandardTime.GetNow());
+        }
+
+        /// <summary>
+        /// Called when action has been executed
+        /// </summary>
+        /// <param name="now"></param>
+        protected virtual void OnEnded(DateTime now)
+        {
+        }
+    }
+}

RateLimiter/TimeLimiter.cs

@@ -164,6 +164,16 @@ public static TimeLimiter GetFromMaxCountByInterval(int maxCount, TimeSpan timeS
             return new TimeLimiter(new CountByIntervalAwaitableConstraint(maxCount, timeSpan));
         }
 
+        /// <summary>
+        /// Returns a TimeLimiter based on a maximum number of parallel calls
+        /// </summary>
+        /// <param name="maxCount"></param>
+        /// <param name="timeSpan"></param>
+        /// <returns></returns>
+        public static TimeLimiter GetFromMaxCallCountByInterval(int maxCount, TimeSpan timeSpan)
+        {
+            return new TimeLimiter(new CallCountByIntervalAwaitableConstraint(maxCount, timeSpan));
+        }
         /// <summary>
         /// Create <see cref="TimeLimiter"/> that will save state using action passed through <paramref name="saveStateAction"/> parameter.
         /// </summary>