feat: implement WAL retentation management functionality

pkg/replication/primary.go

@@ -778,13 +778,51 @@ func (p *Primary) getSession(id string) *ReplicaSession {
 
 // maybeManageWALRetention checks if WAL retention management should be triggered
 func (p *Primary) maybeManageWALRetention() {
-	// This method would analyze all replica acknowledgments to determine
-	// the minimum acknowledged sequence across all replicas, then use that
-	// to decide which WAL files can be safely deleted.
-
-	// For now, this is a placeholder that would need to be connected to the
-	// actual WAL retention management logic
-	// TODO: Implement WAL retention management
+	p.mu.RLock()
+	
+	// Find minimum acknowledged sequence across all connected replicas
+	minAcknowledgedSeq := uint64(^uint64(0)) // Start with max value
+	activeReplicas := 0
+	
+	for id, session := range p.sessions {
+		if session.Connected && session.Active {
+			activeReplicas++
+			if session.LastAckSequence < minAcknowledgedSeq {
+				minAcknowledgedSeq = session.LastAckSequence
+			}
+			log.Info("Replica %s has acknowledged up to sequence %d", 
+				id, session.LastAckSequence)
+		}
+	}
+	p.mu.RUnlock()
+	
+	// Only proceed if we have valid data and active replicas
+	if minAcknowledgedSeq == uint64(^uint64(0)) || minAcknowledgedSeq == 0 {
+		log.Info("No minimum acknowledged sequence found, skipping WAL retention")
+		return
+	}
+	
+	log.Info("WAL retention: minimum acknowledged sequence across %d active replicas: %d", 
+		activeReplicas, minAcknowledgedSeq)
+	
+	// Apply the retention policy using the existing WAL API
+	config := wal.WALRetentionConfig{
+		MaxAge: time.Duration(p.retentionConfig.MaxAgeHours) * time.Hour,
+		MinSequenceKeep: minAcknowledgedSeq,
+	}
+	
+	filesDeleted, err := p.wal.ManageRetention(config)
+	if err != nil {
+		log.Error("Failed to manage WAL retention: %v", err)
+		return
+	}
+	
+	if filesDeleted > 0 {
+		log.Info("WAL retention: deleted %d files, min sequence kept: %d", 
+			filesDeleted, minAcknowledgedSeq)
+	} else {
+		log.Info("WAL retention: no files eligible for deletion")
+	}
 }
 
 // Close shuts down the primary, unregistering from WAL and cleaning up resources