feat: new cron trigger

internal/scheduling/cron.go

@@ -0,0 +1,43 @@
+package scheduling
+
+import (
+	"fmt"
+	"hash/fnv"
+	"time"
+
+	"github.com/robfig/cron/v3"
+)
+
+// CronTrigger represents a trigger based on a cron expression.
+type CronTrigger struct {
+	expression string // required for hash
+	schedule   cron.Schedule
+}
+
+// NewCronTrigger creates a new CronTrigger from a cron expression.
+func NewCronTrigger(expression string) (*CronTrigger, error) {
+	// Use the standard cron parser
+	parser := cron.NewParser(cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow)
+	schedule, err := parser.Parse(expression)
+	if err != nil {
+		return nil, fmt.Errorf("invalid cron expression: %w", err)
+	}
+
+	return &CronTrigger{
+		expression: expression,
+		schedule:   schedule,
+	}, nil
+}
+
+// NextTime calculates the next occurrence of this cron trigger after the given time.
+func (t *CronTrigger) NextTime(now time.Time) *time.Time {
+	next := t.schedule.Next(now)
+	return &next
+}
+
+// Hash returns a stable hash value for the CronTrigger.
+func (t *CronTrigger) Hash() uint64 {
+	h := fnv.New64()
+	fmt.Fprintf(h, "cron:%s", t.expression)
+	return h.Sum64()
+}