added check on veichle identification number uniqueness

src/main/java/io/horizen/lambo/CarRegistryApplicationState.java

@@ -15,8 +15,9 @@
 import scala.util.Try;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
-
+import scala.collection.JavaConverters;
 
 public class CarRegistryApplicationState implements ApplicationState {
 
@@ -29,16 +30,29 @@ public CarRegistryApplicationState(CarInfoDBService carInfoDbService) {
 
     @Override
     public boolean validate(SidechainStateReader stateReader, SidechainBlock block) {
-	    return true;
-    }
+        //We check that there are no multiple transactions declaring the same VIN inside the block
+        Set<String> vinList = new HashSet<>();
+        for (BoxTransaction<Proposition, Box<Proposition>> t :  JavaConverters.seqAsJavaList(block.transactions())){
+            if (t instanceof CarDeclarationTransaction){
+                for (String currentVin :  carInfoDbService.extractVinFromBoxes(t.newBoxes())){
+                    if (vinList.contains(currentVin)){
+                        return false;
+                    }else{
+                        vinList.add(currentVin);
+                    }
+                }
+            }
+        }
+        return true;
+	}
 
     @Override
     public boolean validate(SidechainStateReader stateReader, BoxTransaction<Proposition, Box<Proposition>> transaction) {
         // we go though all CarDeclarationTransactions and verify that each CarBox reflects to unique Car.
-        if (CarDeclarationTransaction.class.isAssignableFrom(transaction.getClass())){
+        if (transaction instanceof CarDeclarationTransaction){
             Set<String> vinList = carInfoDbService.extractVinFromBoxes(transaction.newBoxes());
             for (String vin : vinList) {
-                if (! carInfoDbService.validateVin(vin, null)){
+                if (! carInfoDbService.validateVin(vin, Optional.empty())){
                     return false;
                 }
             }

src/main/java/io/horizen/lambo/car/api/CarApi.java

@@ -99,7 +99,7 @@ private ApiResponse createCar(SidechainNodeView view, CreateCarBoxRequest ent) {
                     .parseBytes(BytesUtils.fromHexString(ent.proposition));
 
             //check that the vin is unique (both in local veichle store and in mempool)
-            if (! carInfoDBService.validateVin(ent.vin, view.getNodeMemoryPool())){
+            if (! carInfoDBService.validateVin(ent.vin, Optional.of(view.getNodeMemoryPool()))){
                 throw new IllegalStateException("Vehicle identification number already present in blockchain");
             }
 

src/main/java/io/horizen/lambo/car/services/CarInfoDBService.java

@@ -13,12 +13,8 @@
 import io.horizen.lambo.car.box.CarSellOrderBox;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-
-import java.nio.ByteBuffer;
-import java.util.Set;
-import java.util.HashSet;
-import java.util.List;
-import java.util.ArrayList;
+import scorex.crypto.hash.Blake2b256;
+import java.util.*;
 
 /**
  * This service manages a local db with the list of all veichle identification numbers (vin) declared on the chain.
@@ -57,13 +53,13 @@ public void updateVin(byte[] version, Set<String> vinToAdd,  Set<String> vinToRe
      * @param memoryPool if not null, the vin is checked also against the mempool transactions
      * @return true if the vin is valid (not already declared)
      */
-    public boolean validateVin(String vin, NodeMemoryPool memoryPool){
+    public boolean validateVin(String vin,  Optional<NodeMemoryPool> memoryPool){
         if (carInfoStorage.get(buildDBElement(vin).getKey()).isPresent()){
             return false;
         }
         //in the vin is not found, and the mempool was provided, we check also there
-        if (memoryPool != null) {
-            for (BoxTransaction<Proposition, Box<Proposition>> transaction : memoryPool.getTransactions()) {
+        if (memoryPool.isPresent()) {
+            for (BoxTransaction<Proposition, Box<Proposition>> transaction : memoryPool.get().getTransactions()) {
                 Set<String> vinInMempool = extractVinFromBoxes(transaction.newBoxes());
                 if (vinInMempool.contains(vin)){
                     return false;
@@ -99,10 +95,9 @@ public Set<String> extractVinFromBoxes(List<Box<Proposition>> boxes){
 
 
     private Pair<ByteArrayWrapper, ByteArrayWrapper> buildDBElement(String vin){
-        //we use a fixed key size of 32, which is the default of iohk.iodb used as underline storage
-        ByteBuffer keyBuffer = ByteBuffer.allocate(32).put(vin.getBytes());
-        ByteArrayWrapper keyWrapper = new ByteArrayWrapper(keyBuffer.array());
-        //the value is not important (we need just a key set, each key is a vin)
+        //we hash the vin to be sure the key has a  fixed size of 32, which is the default of iohk.iodb used as underline storage
+        ByteArrayWrapper keyWrapper = new ByteArrayWrapper(Blake2b256.hash(vin));
+        //the value is not important (we need just a key set, each key is a vin hash)
         ByteArrayWrapper valueWrapper = new ByteArrayWrapper(new byte[1]);
         return new Pair<>(keyWrapper, valueWrapper);
     }

src/main/java/io/horizen/lambo/car/transaction/CarDeclarationTransaction.java

@@ -27,10 +27,9 @@
 // As outputs it contains possible RegularBoxes(to pay fee and change) and new CarBox entry.
 // No specific unlockers to parent class logic, but has specific new box.
 // TODO: add specific mempool incompatibility checker to deprecate keeping in the Mempool txs that declare the same Car.
-public final class CarDeclarationTransaction extends AbstractRegularTransaction {
+public final class CarDeclarationTransaction<P extends Proposition, B extends NoncedBox<P>> extends AbstractRegularTransaction {
 
     private final CarBoxData outputCarBoxData;
-
     private List<NoncedBox<Proposition>> newBoxes;
 
     public CarDeclarationTransaction(List<byte[]> inputRegularBoxIds,