Amazon.SellingPartnerApi.API/Amazon.SellingPartnerApiSDK/Misc/RateLimits.cs

using System;
using System.Threading.Tasks;

namespace Amazon.SellingPartnerApiSDK.Misc
{
    internal class RateLimits
    {
        internal RateLimits(decimal rate, int burst)
        {
            Rate = rate;
            Burst = burst;
            LastRequest = DateTime.UtcNow;
            RequestsSent = 0;
        }

        internal decimal Rate { get; set; }
        internal int Burst { get; set; }
        internal DateTime LastRequest { get; set; }
        internal int RequestsSent { get; set; }

        private int GetRatePeriodMs()
        {
            return (int)(1 / Rate * 1000 / 1);
        }

        public RateLimits NextRate(RateLimitType rateLimitType)
        {
            if (RequestsSent < 0)
                RequestsSent = 0;

            var ratePeriodMs = GetRatePeriodMs();

            var nextRequestsSent = RequestsSent + 1;
            var nextRequestsSentTxt = nextRequestsSent > Burst ? "FULL" : nextRequestsSent.ToString();
            if (AmazonCredential.DebugMode)
            {
                string output =
                    $"[RateLimits ,{rateLimitType,15}]: {DateTime.UtcNow.ToString(),10}\t Request/Burst: {nextRequestsSentTxt}/{Burst}\t Rate: {Rate}/{ratePeriodMs}ms";
                Console.WriteLine(output);
            }

            if (RequestsSent >= Burst)
            {
                var lastRequestTime = LastRequest;
                while (true)
                {
                    lastRequestTime = lastRequestTime.AddMilliseconds(ratePeriodMs);
                    if (lastRequestTime > DateTime.UtcNow)
                        break;
                    else
                        RequestsSent -= 1;

                    if (RequestsSent <= 0)
                    {
                        RequestsSent = 0;
                        break;
                    }
                }
            }

            if (RequestsSent >= Burst)
            {
                LastRequest = LastRequest.AddMilliseconds(ratePeriodMs);
                var tempLastRequest = LastRequest;
                while (tempLastRequest >= DateTime.UtcNow)
                    Task.Delay(100).Wait();
            }

            if (RequestsSent + 1 <= Burst)
                RequestsSent += 1;
            LastRequest = DateTime.UtcNow;

            return this;
        }

        internal void SetRateLimit(decimal rate)
        {
            Rate = rate;
        }

        internal void Delay()
        {
            Task.Delay(GetRatePeriodMs()).Wait();
        }
    }
}