Synnefo » Pithos MS Client

using System;

namespace Hammock.Tasks

{

#if !SILVERLIGHT

    [Serializable]

#endif

    public class RateLimitingRule<T> : IRateLimitingRule<T>

    {

        private readonly RateLimitType _rateLimitType;

        public RateLimitingRule(Predicate<T> rateLimitIf)

        {

            _rateLimitType = RateLimitType.ByPredicate;

            RateLimitIf = rateLimitIf;

        }

        public RateLimitingRule(double percentOfTotal)

        {

            _rateLimitType = RateLimitType.ByPercent;

            LimitToPercentOfTotal = percentOfTotal;

        }

        public RateLimitingRule(Func<T> getRateLimitStatus, Predicate<T> rateLimitIf)

        {

            _rateLimitType = RateLimitType.ByPredicate;

            GetRateLimitStatus = getRateLimitStatus;

            RateLimitIf = rateLimitIf;

        }

        public RateLimitingRule(Func<T> getRateLimitStatus, double percentOfTotal)

        {

            _rateLimitType = RateLimitType.ByPercent;

            GetRateLimitStatus = getRateLimitStatus;

            LimitToPercentOfTotal = percentOfTotal;

        }

        #region IRateLimitingRule Members

        public virtual double? LimitToPercentOfTotal { get; private set; }

        public virtual RateLimitType RateLimitType

        {

            get { return _rateLimitType; }

        }

        public Func<T> GetRateLimitStatus { get; set; }

        public Predicate<T> RateLimitIf { get; private set; }

        #endregion

        public bool ShouldSkipForRateLimiting()

        {

            // [JD]: Only pre-skip via predicate; percentage based adjusts rate after the call

            if (RateLimitType != RateLimitType.ByPredicate)

            {

                return false;

            }

            if (RateLimitIf == null)

            {

                throw new InvalidOperationException("Rule is set to use predicate, but no predicate is defined.");

            }

            var status = default(T);

            if (GetRateLimitStatus != null)

            {

                status = GetRateLimitStatus();

            }

            return !RateLimitIf(status);

        }

        public TimeSpan? CalculateNewInterval()

        {

            if (RateLimitType != RateLimitType.ByPercent)

            {

                return null;

            }

            if (!LimitToPercentOfTotal.HasValue)

            {

                return null;

            }

            var currentRateLimit = (IRateLimitStatus)GetRateLimitStatus();

            if (currentRateLimit.RemainingUses == 0)

            {

                return currentRateLimit.NextReset - DateTime.Now;

            }

            var secondsUntilNextReset = (currentRateLimit.NextReset - DateTime.Now).TotalSeconds;

            var desiredRetriesBeforeReset = currentRateLimit.RemainingUses * LimitToPercentOfTotal.Value;

            var desiredInterval = (int)Math.Floor(secondsUntilNextReset / desiredRetriesBeforeReset);

            return new TimeSpan(0, 0, 0, desiredInterval);

        }

    }

}