From 31b4eca24d3df7005545afe70279b5c4dd04a319 Mon Sep 17 00:00:00 2001
From: John Roesler <johnrroesler@gmail.com>
Date: Fri, 3 Jan 2025 10:34:58 -0600
Subject: [PATCH] working to handle edge cases where a job can be run twice,
 unexpectedly

---
 job.go       |  8 ++++----
 scheduler.go | 11 ++++++++++-
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/job.go b/job.go
index 2ea8e91..2974733 100644
--- a/job.go
+++ b/job.go
@@ -818,7 +818,7 @@ func (d dailyJob) next(lastRun time.Time) time.Time {
 	}
 	firstPass = false
 
-	startNextDay := time.Date(lastRun.Year(), lastRun.Month(), lastRun.Day()+int(d.interval), 0, 0, 0, lastRun.Nanosecond(), lastRun.Location())
+	startNextDay := time.Date(lastRun.Year(), lastRun.Month(), lastRun.Day()+int(d.interval), 0, 0, 0, 0, lastRun.Location())
 	return d.nextDay(startNextDay, firstPass)
 }
 
@@ -826,7 +826,7 @@ func (d dailyJob) nextDay(lastRun time.Time, firstPass bool) time.Time {
 	for _, at := range d.atTimes {
 		// sub the at time hour/min/sec onto the lastScheduledRun's values
 		// to use in checks to see if we've got our next run time
-		atDate := time.Date(lastRun.Year(), lastRun.Month(), lastRun.Day(), at.Hour(), at.Minute(), at.Second(), lastRun.Nanosecond(), lastRun.Location())
+		atDate := time.Date(lastRun.Year(), lastRun.Month(), lastRun.Day(), at.Hour(), at.Minute(), at.Second(), 0, lastRun.Location())
 
 		if firstPass && atDate.After(lastRun) {
 			// checking to see if it is after i.e. greater than,
@@ -872,7 +872,7 @@ func (w weeklyJob) nextWeekDayAtTime(lastRun time.Time, firstPass bool) time.Tim
 			for _, at := range w.atTimes {
 				// sub the at time hour/min/sec onto the lastScheduledRun's values
 				// to use in checks to see if we've got our next run time
-				atDate := time.Date(lastRun.Year(), lastRun.Month(), lastRun.Day()+int(weekDayDiff), at.Hour(), at.Minute(), at.Second(), lastRun.Nanosecond(), lastRun.Location())
+				atDate := time.Date(lastRun.Year(), lastRun.Month(), lastRun.Day()+int(weekDayDiff), at.Hour(), at.Minute(), at.Second(), 0, lastRun.Location())
 
 				if firstPass && atDate.After(lastRun) {
 					// checking to see if it is after i.e. greater than,
@@ -940,7 +940,7 @@ func (m monthlyJob) nextMonthDayAtTime(lastRun time.Time, days []int, firstPass
 			for _, at := range m.atTimes {
 				// sub the day, and the at time hour/min/sec onto the lastScheduledRun's values
 				// to use in checks to see if we've got our next run time
-				atDate := time.Date(lastRun.Year(), lastRun.Month(), day, at.Hour(), at.Minute(), at.Second(), lastRun.Nanosecond(), lastRun.Location())
+				atDate := time.Date(lastRun.Year(), lastRun.Month(), day, at.Hour(), at.Minute(), at.Second(), 0, lastRun.Location())
 
 				if atDate.Month() != lastRun.Month() {
 					// this check handles if we're setting a day not in the current month
diff --git a/scheduler.go b/scheduler.go
index 9827f0c..19864c6 100644
--- a/scheduler.go
+++ b/scheduler.go
@@ -331,7 +331,7 @@ func (s *scheduler) selectExecJobsOutForRescheduling(id uuid.UUID) {
 		return
 	}
 
-	scheduleFrom := j.lastRun
+	var scheduleFrom time.Time
 	if len(j.nextScheduled) > 0 {
 		// always grab the last element in the slice as that is the furthest
 		// out in the future and the time from which we want to calculate
@@ -362,6 +362,15 @@ func (s *scheduler) selectExecJobsOutForRescheduling(id uuid.UUID) {
 		}
 	}
 
+	if slices.Contains(j.nextScheduled, next) {
+		// if the next value is a duplicate of what's already in the nextScheduled slice, for example:
+		// - the job is being rescheduled off the same next run value as before
+		// increment to the next, next value
+		for slices.Contains(j.nextScheduled, next) {
+			next = j.next(next)
+		}
+	}
+
 	// Clean up any existing timer to prevent leaks
 	if j.timer != nil {
 		j.timer.Stop()