refactor stages list initialization based on the sync mode

api/service/stagedstreamsync/default_stages.go

@@ -8,7 +8,57 @@ type ForwardOrder []SyncStageID
 type RevertOrder []SyncStageID
 type CleanUpOrder []SyncStageID
 
-var DefaultForwardOrder = ForwardOrder{
+var (
+	StagesForwardOrder ForwardOrder
+	StagesRevertOrder  RevertOrder
+	StagesCleanUpOrder CleanUpOrder
+)
+
+func initStagesOrder(syncMode SyncMode) {
+	switch syncMode {
+	case FullSync:
+		initFullSyncStagesOrder()
+	case FastSync:
+		initFastSyncStagesOrder()
+	default:
+		panic("not supported sync mode")
+	}
+}
+
+func initFullSyncStagesOrder() {
+	StagesForwardOrder = ForwardOrder{
+		Heads,
+		SyncEpoch,
+		ShortRange,
+		BlockBodies,
+		States,
+		LastMile,
+		Finish,
+	}
+
+	StagesRevertOrder = RevertOrder{
+		Finish,
+		LastMile,
+		States,
+		BlockBodies,
+		ShortRange,
+		SyncEpoch,
+		Heads,
+	}
+
+	StagesCleanUpOrder = CleanUpOrder{
+		Finish,
+		LastMile,
+		States,
+		BlockBodies,
+		ShortRange,
+		SyncEpoch,
+		Heads,
+	}
+}
+
+func initFastSyncStagesOrder() {
+	StagesForwardOrder = ForwardOrder{
 		Heads,
 		SyncEpoch,
 		ShortRange,
@@ -18,9 +68,9 @@ var DefaultForwardOrder = ForwardOrder{
 		Receipts,
 		LastMile,
 		Finish,
-}
+	}
 
-var DefaultRevertOrder = RevertOrder{
+	StagesRevertOrder = RevertOrder{
 		Finish,
 		LastMile,
 		Receipts,
@@ -30,9 +80,9 @@ var DefaultRevertOrder = RevertOrder{
 		ShortRange,
 		SyncEpoch,
 		Heads,
-}
+	}
 
-var DefaultCleanUpOrder = CleanUpOrder{
+	StagesCleanUpOrder = CleanUpOrder{
 		Finish,
 		LastMile,
 		Receipts,
@@ -42,6 +92,7 @@ var DefaultCleanUpOrder = CleanUpOrder{
 		ShortRange,
 		SyncEpoch,
 		Heads,
+	}
 }
 
 func DefaultStages(ctx context.Context,

api/service/stagedstreamsync/staged_stream_sync.go

@@ -268,8 +268,21 @@ func New(
 	logger zerolog.Logger,
 ) *StagedStreamSync {
 
+	// init stages order based on sync mode
+	initStagesOrder(config.SyncMode)
+
+	forwardStages := make([]*Stage, len(stagesList))
+	for i, stageIndex := range StagesForwardOrder {
+		for _, s := range stagesList {
+			if s.ID == stageIndex {
+				forwardStages[i] = s
+				break
+			}
+		}
+	}
+
 	revertStages := make([]*Stage, len(stagesList))
-	for i, stageIndex := range DefaultRevertOrder {
+	for i, stageIndex := range StagesRevertOrder {
 		for _, s := range stagesList {
 			if s.ID == stageIndex {
 				revertStages[i] = s
@@ -277,8 +290,9 @@ func New(
 			}
 		}
 	}
+
 	pruneStages := make([]*Stage, len(stagesList))
-	for i, stageIndex := range DefaultCleanUpOrder {
+	for i, stageIndex := range StagesCleanUpOrder {
 		for _, s := range stagesList {
 			if s.ID == stageIndex {
 				pruneStages[i] = s