Addressed PR comments

Signed-off-by: Albert Callarisa <albert@diagrid.io>

Author: acroca

api/helpers/task.go

@@ -1,16 +1,20 @@
 package helpers
 
 import (
-	"fmt"
 	"reflect"
 	"runtime"
+	"strconv"
 	"strings"
 )
 
 // GenerateChildWorkflowInstanceID generates a deterministic instance ID for a
 // child workflow based on the parent instance ID and the action's sequence number.
 func GenerateChildWorkflowInstanceID(parentInstanceID string, actionID int32) string {
-	return fmt.Sprintf("%s:%04x", parentInstanceID, actionID)
+	// Adding 0x10000 guarantees at least 5 hex digits (e.g. 0 → "10000"),
+	// so taking the last 4 gives a zero-padded result (e.g. "0000").
+	hex := strconv.FormatInt(0x10000+int64(actionID), 16)
+	hex = hex[len(hex)-4:]
+	return parentInstanceID + ":" + hex
 }
 
 func GetTaskFunctionName(f any) string {

backend/runtimestate/applier.go

@@ -151,22 +151,17 @@ func (a *Applier) Actions(s *protos.WorkflowRuntimeState, customStatus *wrappers
 				FireAt: timerAction.FireAt,
 				Name:   timerAction.Name,
 			}
-			if externalEvent := timerAction.GetExternalEvent(); externalEvent != nil {
-				timerCreated.Origin = &protos.TimerCreatedEvent_ExternalEvent{
-					ExternalEvent: externalEvent,
-				}
-			} else if ct := timerAction.GetCreateTimer(); ct != nil {
-				timerCreated.Origin = &protos.TimerCreatedEvent_CreateTimer{
-					CreateTimer: ct,
-				}
-			} else if ar := timerAction.GetActivityRetry(); ar != nil {
-				timerCreated.Origin = &protos.TimerCreatedEvent_ActivityRetry{
-					ActivityRetry: ar,
-				}
-			} else if cwr := timerAction.GetChildWorkflowRetry(); cwr != nil {
-				timerCreated.Origin = &protos.TimerCreatedEvent_ChildWorkflowRetry{
-					ChildWorkflowRetry: cwr,
-				}
+			switch o := timerAction.GetOrigin().(type) {
+			case *protos.CreateTimerAction_CreateTimer:
+				timerCreated.Origin = &protos.TimerCreatedEvent_CreateTimer{CreateTimer: o.CreateTimer}
+			case *protos.CreateTimerAction_ExternalEvent:
+				timerCreated.Origin = &protos.TimerCreatedEvent_ExternalEvent{ExternalEvent: o.ExternalEvent}
+			case *protos.CreateTimerAction_ActivityRetry:
+				timerCreated.Origin = &protos.TimerCreatedEvent_ActivityRetry{ActivityRetry: o.ActivityRetry}
+			case *protos.CreateTimerAction_ChildWorkflowRetry:
+				timerCreated.Origin = &protos.TimerCreatedEvent_ChildWorkflowRetry{ChildWorkflowRetry: o.ChildWorkflowRetry}
+			default:
+				return false, fmt.Errorf("unknown timer origin type: %T", timerAction.GetOrigin())
 			}
 			_ = AddEvent(s, &protos.HistoryEvent{
 				EventId:   action.Id,