feat: implement rollback fallback mechanism with blockchain-specific …

internal/constants/blockchains.go

@@ -42,6 +42,45 @@ func BlockchainTypeToPB(bt wconstants.BlockchainType) commonv1.Blockchain {
 	}
 }
 
+// rollbackSafeDepth is the number of blocks to roll back when no recent incident is found.
+// Used as a fallback when the last rollback incident is older than rollbackIncidentMaxAge.
+const rollbackIncidentMaxAge = 2 * time.Hour
+
+var rollbackSafeDepth = map[wconstants.BlockchainType]int64{
+	// Tron
+	wconstants.BlockchainTypeTron: 20,
+
+	// EVM
+	wconstants.BlockchainTypeEthereum:          12,
+	wconstants.BlockchainTypeBinanceSmartChain: 20,
+	wconstants.BlockchainTypePolygon:           128,
+	wconstants.BlockchainTypeArbitrum:          20,
+	wconstants.BlockchainTypeOptimism:          20,
+	wconstants.BlockchainTypeLinea:             20,
+
+	// BTC Like
+	wconstants.BlockchainTypeBitcoin:     6,
+	wconstants.BlockchainTypeLitecoin:    6,
+	wconstants.BlockchainTypeBitcoinCash: 6,
+	wconstants.BlockchainTypeDogecoin:    6,
+}
+
+// RollbackFallbackBlock returns the safe block to revert to when no recent incident is found.
+func RollbackFallbackBlock(blockchain wconstants.BlockchainType, currentBlock int64) int64 {
+	depth, ok := rollbackSafeDepth[blockchain]
+	if !ok {
+		depth = 20
+	}
+	safe := currentBlock - depth
+	if safe < 0 {
+		return 0
+	}
+	return safe
+}
+
+// RollbackIncidentMaxAge is the maximum age of a rollback incident to be considered relevant.
+func RollbackIncidentMaxAge() time.Duration { return rollbackIncidentMaxAge }
+
 var minConfirmations = map[wconstants.BlockchainType]uint64{
 	// Tron
 	wconstants.BlockchainTypeTron: 19,

internal/eproxy/service.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"strings"
+	"time"
 
 	"github.com/dv-net/dv-processing/internal/interceptors"
 
@@ -256,23 +257,29 @@ func (s *Service) GetIncidents(ctx context.Context, blockchain wconstants.Blockc
 	return incidents.Msg.GetItems(), nil
 }
 
-// GetRollbackStartingBlock returns the block height to start parsing from after a rollback incident
-func (s *Service) GetRollbackStartingBlock(ctx context.Context, blockchain wconstants.BlockchainType) (uint64, error) {
-	incidents, err := s.GetIncidents(ctx, blockchain, 1)
-	if err != nil {
-		return 0, fmt.Errorf("get last incident for rollback recovery: %w", err)
-	}
+// GetRollbackStartingBlock returns the block height to start parsing from after a rollback.
+// It looks for a recent rollback incident (within rollbackIncidentMaxAge). If none is found,
+// it falls back to currentBlock - safeDepth, where safeDepth is blockchain-specific.
+func (s *Service) GetRollbackStartingBlock(ctx context.Context, blockchain wconstants.BlockchainType, currentBlock int64) (uint64, error) {
+	incidents, _ := s.GetIncidents(ctx, blockchain, 10)
 
-	if len(incidents) < 1 {
-		return 0, fmt.Errorf("no incidents found for blockchain %s", blockchain.String())
-	}
+	maxAge := constants.RollbackIncidentMaxAge()
+
+	for _, incident := range incidents {
+		if incident.GetType() != incidentsv2.IncidentType_INCIDENT_TYPE_ROLLBACK {
+			continue
+		}
+
+		if incident.GetCreatedAt() != nil && time.Since(incident.GetCreatedAt().AsTime()) > maxAge {
+			break // incidents are ordered newest-first; all further are older
+		}
 
-	incident := incidents[0]
-	if incident.GetType() != incidentsv2.IncidentType_INCIDENT_TYPE_ROLLBACK {
-		return 0, fmt.Errorf("last incident is not a rollback incident for blockchain %s", blockchain.String())
+		return incident.GetDataRollback().GetRevertToBlockHeight(), nil
 	}
 
-	return incident.GetDataRollback().GetRevertToBlockHeight(), nil
+	// No recent incident or API unavailable — fall back to safe depth per blockchain.
+	safeBlock := constants.RollbackFallbackBlock(blockchain, currentBlock)
+	return uint64(safeBlock), nil //nolint:gosec
 }
 
 type FindTransactionsParams struct {

internal/escanner/scanner.go

@@ -591,7 +591,7 @@ func (s *scanner) checksForEvent(event *transactionsv2.Event) []eventCheck {
 func (s *scanner) handleRollback(ctx context.Context) error {
 	s.logger.Infof("Handling rollback incident for blockchain %s", s.blockchain.String())
 
-	newStartingBlock, err := s.bs.EProxy().GetRollbackStartingBlock(ctx, s.blockchain)
+	newStartingBlock, err := s.bs.EProxy().GetRollbackStartingBlock(ctx, s.blockchain, s.lastParsedBlockHeight.Load())
 	if err != nil {
 		return fmt.Errorf("get rollback starting block: %w", err)
 	}