Killed history

NadekoBot.Core/Modules/Utility/Services/RunningRepeater.cs

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+using System;
+using NadekoBot.Core.Services.Database.Models;
+
+namespace NadekoBot.Modules.Utility.Services
+{
+    public sealed class RunningRepeater
+    {
+        public DateTime NextTime { get; private set; }
+        
+        public Repeater Repeater { get; }
+        public int ErrorCount { get; set; }
+        
+        public RunningRepeater(Repeater repeater)
+        {
+            this.Repeater = repeater;
+            NextTime = CalculateInitialExecution();
+        }
+
+        public void UpdateNextTime()
+        {
+            NextTime = DateTime.UtcNow + Repeater.Interval;
+        }
+        
+        private DateTime CalculateInitialExecution()
+        {
+            if (Repeater.StartTimeOfDay != null)
+            {
+                // if there was a start time of day
+                // calculate whats the next time of day repeat should trigger at
+                // based on teh dateadded
+
+                // i know this is not null because of the check in the query
+                var added = Repeater.DateAdded;
+
+                // initial trigger was the time of day specified by the command.
+                var initialTriggerTimeOfDay = Repeater.StartTimeOfDay.Value;
+
+                DateTime initialDateTime;
+
+                // if added timeofday is less than specified timeofday for initial trigger
+                // that means the repeater first ran that same day at that exact specified time
+                if (added.TimeOfDay <= initialTriggerTimeOfDay)
+                {
+                    // in that case, just add the difference to make sure the timeofday is the same
+                    initialDateTime = added + (initialTriggerTimeOfDay - added.TimeOfDay);
+                }
+                else
+                {
+                    // if not, then it ran at that time the following day
+                    // in other words; Add one day, and subtract how much time passed since that time of day
+                    initialDateTime = added + TimeSpan.FromDays(1) - (added.TimeOfDay - initialTriggerTimeOfDay);
+                }
+
+                return CalculateInitialInterval(initialDateTime);
+            }
+
+            // if repeater is not running daily, its initial time is the time it was Added at, plus the interval
+            return CalculateInitialInterval(Repeater.DateAdded + Repeater.Interval);
+        }
+
+        /// <summary>
+        /// Calculate when is the proper time to run the repeater again based on initial time repeater ran.
+        /// </summary>
+        /// <param name="repeaterter"></param>
+        /// <param name="initialDateTime">Initial time repeater ran at (or should run at).</param>
+        private DateTime CalculateInitialInterval(DateTime initialDateTime)
+        {
+            // if the initial time is greater than now, that means the repeater didn't still execute a single time.
+            // just schedule it
+            if (initialDateTime > DateTime.UtcNow)
+            {
+                return initialDateTime;
+            }
+            
+            // else calculate based on minutes difference
+
+            // get the difference
+            var diff = DateTime.UtcNow - initialDateTime;
+
+            // see how many times the repeater theoretically ran already
+            var triggerCount = diff / Repeater.Interval;
+
+            // ok lets say repeater was scheduled to run 10h ago.
+            // we have an interval of 2.4h
+            // repeater should've ran 4 times- that's 9.6h
+            // next time should be in 2h from now exactly
+            // 10/2.4 is 4.166
+            // 4.166 - Math.Truncate(4.166) is 0.166
+            // initial interval multiplier is 1 - 0.166 = 0.834
+            // interval (2.4h) * 0.834 is 2.0016 and that is the initial interval
+
+            var initialIntervalMultiplier = 1 - (triggerCount - Math.Truncate(triggerCount));
+            return DateTime.UtcNow + (Repeater.Interval * initialIntervalMultiplier);
+        }
+    }
+}