check for duplicates before storing

server/db/mongo/checkDuplicate.go

@@ -0,0 +1,25 @@
+package mongo
+
+import (
+	"context"
+	"fmt"
+	nostr "grain/server/types" // Adjust import path as needed
+
+	"go.mongodb.org/mongo-driver/bson"
+)
+
+// CheckDuplicateEvent checks if an event with the same ID already exists in the collection.
+func CheckDuplicateEvent(ctx context.Context, evt nostr.Event) (bool, error) {
+	collection := GetCollection(evt.Kind)
+	filter := bson.M{"id": evt.ID}
+
+	var existingEvent nostr.Event
+	err := collection.FindOne(ctx, filter).Decode(&existingEvent)
+	if err != nil {
+		if err.Error() == "mongo: no documents in result" {
+			return false, nil // No duplicate found
+		}
+		return false, fmt.Errorf("error checking for duplicate event: %v", err)
+	}
+	return true, nil // Duplicate found
+}

server/handlers/event.go

@@ -66,6 +66,19 @@ func HandleEvent(ws *websocket.Conn, message []interface{}) {
 		return
 	}
 
+	// Check for duplicate event
+	isDuplicate, err := mongo.CheckDuplicateEvent(context.TODO(), evt)
+	if err != nil {
+		fmt.Printf("Error checking for duplicate event: %v\n", err)
+		response.SendOK(ws, evt.ID, false, "error: internal server error during duplicate check")
+		return
+	}
+
+	if isDuplicate {
+		response.SendOK(ws, evt.ID, false, "blocked: the database already contains this event")
+		return
+	}
+
 	// Store the event in MongoDB or other storage
 	mongo.StoreMongoEvent(context.TODO(), evt, ws)
 	fmt.Println("Event processed:", evt.ID)