Changeset 0.27.2 (#169)

server/taskutil/cron.go

@@ -0,0 +1,49 @@
+package taskutil
+
+import (
+	"time"
+
+	"github.com/robfig/cron/v3"
+)
+
+// cronParser is a shared parser instance. Standard 5-field cron with
+// optional descriptors (@hourly, @daily, @weekly, @monthly, etc.).
+var cronParser = cron.NewParser(
+	cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow | cron.Descriptor,
+)
+
+// NextRunFromSchedule computes the next run time from a cron expression
+// and timezone. Returns nil for "once" schedules (one-shot tasks).
+//
+// Replaces the v0.27.1 hand-rolled parseDailyCron with full 5-field
+// cron support via robfig/cron/v3.
+func NextRunFromSchedule(schedule, timezone string) *time.Time {
+	if schedule == "once" {
+		return nil
+	}
+
+	now := time.Now()
+	if tz, err := time.LoadLocation(timezone); err == nil {
+		now = now.In(tz)
+	}
+
+	sched, err := cronParser.Parse(schedule)
+	if err != nil {
+		// Unparseable — log at call site, caller decides fallback
+		return nil
+	}
+
+	next := sched.Next(now).UTC()
+	return &next
+}
+
+// ValidateCron checks whether a cron expression is valid.
+// Returns nil for valid expressions, error describing the problem otherwise.
+// "once" is always valid (one-shot schedule).
+func ValidateCron(schedule string) error {
+	if schedule == "once" {
+		return nil
+	}
+	_, err := cronParser.Parse(schedule)
+	return err
+}