either of cron or loop can be set and unset, mark invalids as invalid and unfinish

server/ajax/ajax.go

@@ -128,24 +128,30 @@ func (a *Ajax) loopTasks() (time.Time, error) {
 			if task.Loop == 0 && task.Cron == "" {
 				continue
 			}
-			nextLoopTrigger := task.Completed.Add(task.Loop)
-			if task.Loop == 0 {
-				nextLoopTrigger2 := task.Cron.Next(task.Completed)
-				if nextLoopTrigger2.Before(nextLoopTrigger) {
-					nextLoopTrigger = nextLoopTrigger2
+			var nextTask time.Time
+			if task.Loop > 0 {
+				nextTask = task.Completed.Add(task.Loop)
+			}
+			if string(task.Cron) != "" {
+				nextTask2 := task.Cron.Next(task.Completed)
+				if nextTask2 != (time.Time{}) && (nextTask == (time.Time{}) || nextTask2.Before(nextTask)) {
+					nextTask = nextTask2
 				}
 			}
-			if time.Now().Before(nextLoopTrigger) {
-				if nextLoopTrigger.Before(nextDue) {
-					nextDue = nextLoopTrigger
-				}
-				continue
-			}
+			if time.Now().After(nextTask) {
 				task.Complete = false
 				task.Completed = time.Time{}
+				if nextTask == (time.Time{}) {
+					task.Title += " !!!INVALID CRON/LOOP!!!"
+				}
 				if err := a.storageSetTask(list.UUID, task); err != nil {
 					return nextDue, err
 				}
+			} else {
+				if nextTask.Before(nextDue) {
+					nextDue = nextTask
+				}
+			}
 		}
 	}
 	return nextDue, nil

server/ajax/form/cron.go

@@ -1,6 +1,7 @@
 package form
 
 import (
+	"log"
 	"time"
 
 	"github.com/robfig/cron/v3"
@@ -11,6 +12,7 @@ type Cron string
 func (c Cron) Next(since time.Time) time.Time {
 	schedule, err := cron.ParseStandard(string(c))
 	if err != nil {
+		log.Printf("failed to parse cron %q: %v", string(c), err)
 		return time.Time{}
 	}
 	return schedule.Next(since)