AT transactions now either have null message or null amount&assetId.

AT transaction transformer changed to refuse to deserialize AT transactions,
as they should never appear on the wire.

Ditto for GENESIS transactions.

src/main/java/org/qortal/at/QortalATAPI.java

@@ -376,7 +376,7 @@ public class QortalATAPI extends API {
 
 		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, Group.NO_GROUP, reference, NullAccount.PUBLIC_KEY, 0L, null);
 		ATTransactionData atTransactionData = new ATTransactionData(baseTransactionData, this.atData.getATAddress(),
-				recipient.getAddress(), amount, this.atData.getAssetId(), new byte[0]);
+				recipient.getAddress(), amount, this.atData.getAssetId());
 		AtTransaction atTransaction = new AtTransaction(this.repository, atTransactionData);
 
 		// Add to our transactions
@@ -393,7 +393,7 @@ public class QortalATAPI extends API {
 
 		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, Group.NO_GROUP, reference, NullAccount.PUBLIC_KEY, 0L, null);
 		ATTransactionData atTransactionData = new ATTransactionData(baseTransactionData, this.atData.getATAddress(),
-				recipient.getAddress(), 0L, this.atData.getAssetId(), message);
+				recipient.getAddress(), message);
 		AtTransaction atTransaction = new AtTransaction(this.repository, atTransactionData);
 
 		// Add to our transactions
@@ -422,7 +422,7 @@ public class QortalATAPI extends API {
 
 		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, Group.NO_GROUP, reference, NullAccount.PUBLIC_KEY, 0L, null);
 		ATTransactionData atTransactionData = new ATTransactionData(baseTransactionData, this.atData.getATAddress(),
-				creator.getAddress(), finalBalance, this.atData.getAssetId(), new byte[0]);
+				creator.getAddress(), finalBalance, this.atData.getAssetId());
 		AtTransaction atTransaction = new AtTransaction(this.repository, atTransactionData);
 
 		// Add to our transactions

src/main/java/org/qortal/data/transaction/ATTransactionData.java

@@ -29,6 +29,7 @@ public class ATTransactionData extends TransactionData {
 	// Not always present
 	private Long assetId;
 
+	// Not always present
 	private byte[] message;
 
 	// Constructors
@@ -42,7 +43,7 @@ public class ATTransactionData extends TransactionData {
 		this.creatorPublicKey = NullAccount.PUBLIC_KEY;
 	}
 
-	/** From repository */
+	/** Constructing from repository */
 	public ATTransactionData(BaseTransactionData baseTransactionData, String atAddress, String recipient, Long amount, Long assetId, byte[] message) {
 		super(TransactionType.AT, baseTransactionData);
 
@@ -54,6 +55,16 @@ public class ATTransactionData extends TransactionData {
 		this.message = message;
 	}
 
+	/** Constructing a new MESSAGE-type AT transaction */
+	public ATTransactionData(BaseTransactionData baseTransactionData, String atAddress, String recipient, byte[] message) {
+		this(baseTransactionData, atAddress, recipient, null, null, message);
+	}
+
+	/** Constructing a new PAYMENT-type AT transaction */
+	public ATTransactionData(BaseTransactionData baseTransactionData, String atAddress, String recipient, long amount, long assetId) {
+		this(baseTransactionData, atAddress, recipient, amount, assetId, null);
+	}
+
 	// Getters/Setters
 
 	public String getATAddress() {

src/main/java/org/qortal/transaction/AtTransaction.java

@@ -87,27 +87,27 @@ public class AtTransaction extends Transaction {
 			return ValidationResult.INVALID_ADDRESS;
 
 		Long amount = this.atTransactionData.getAmount();
+		Long assetId = this.atTransactionData.getAssetId();
 		byte[] message = this.atTransactionData.getMessage();
 
-		// We can only have either message or amount
+		boolean hasPayment = amount != null && assetId != null;
-		boolean amountIsNull = amount == null;
+		boolean hasMessage = message != null; // empty message OK
-		boolean messageIsEmpty = message == null || message.length == 0;
 
-		if ((messageIsEmpty && amountIsNull) || (!messageIsEmpty && !amountIsNull))
+		// We can only have either message or payment, not both, nor neither
+		if ((hasMessage && hasPayment) || (!hasMessage && !hasPayment))
 			return ValidationResult.INVALID_AT_TRANSACTION;
 
-		if (!messageIsEmpty && message.length > MAX_DATA_SIZE)
+		if (hasMessage && message.length > MAX_DATA_SIZE)
 			return ValidationResult.INVALID_DATA_LENGTH;
 
 		// If we have no payment then we're done
-		if (amountIsNull)
+		if (!hasPayment)
 			return ValidationResult.OK;
 
 		// Check amount is zero or positive
 		if (amount < 0)
 			return ValidationResult.NEGATIVE_AMOUNT;
 
-		long assetId = this.atTransactionData.getAssetId();
 		AssetData assetData = this.repository.getAssetRepository().fromAssetId(assetId);
 		// Check asset even exists
 		if (assetData == null)

src/main/java/org/qortal/transform/transaction/AtTransactionTransformer.java

@@ -14,25 +14,18 @@ import com.google.common.primitives.Longs;
 
 public class AtTransactionTransformer extends TransactionTransformer {
 
-	private static final int SENDER_LENGTH = ADDRESS_LENGTH;
-	private static final int RECIPIENT_LENGTH = ADDRESS_LENGTH;
-	private static final int DATA_SIZE_LENGTH = INT_LENGTH;
-
-	private static final int EXTRAS_LENGTH = SENDER_LENGTH + RECIPIENT_LENGTH + AMOUNT_LENGTH + ASSET_ID_LENGTH + DATA_SIZE_LENGTH;
-
 	protected static final TransactionLayout layout = null;
 
 	// Property lengths
 	public static TransactionData fromByteBuffer(ByteBuffer byteBuffer) throws TransformationException {
-		throw new TransformationException("Serialized AT Transactions should not exist!");
+		throw new TransformationException("Serialized AT transactions should not exist!");
 	}
 
 	public static int getDataLength(TransactionData transactionData) throws TransformationException {
-		ATTransactionData atTransactionData = (ATTransactionData) transactionData;
+		throw new TransformationException("Serialized AT transactions should not exist!");
-
-		return getBaseLength(transactionData) + EXTRAS_LENGTH + atTransactionData.getMessage().length;
 	}
 
+	// Used for generating fake transaction signatures
 	public static byte[] toBytes(TransactionData transactionData) throws TransformationException {
 		try {
 			ATTransactionData atTransactionData = (ATTransactionData) transactionData;
@@ -47,18 +40,16 @@ public class AtTransactionTransformer extends TransactionTransformer {
 
 			Serialization.serializeAddress(bytes, atTransactionData.getRecipient());
 
-			// Only emit amount if greater than zero (safer than checking assetId)
-			if (atTransactionData.getAmount() > 0) {
-				bytes.write(Longs.toByteArray(atTransactionData.getAmount()));
-				bytes.write(Longs.toByteArray(atTransactionData.getAssetId()));
-			}
-
 			byte[] message = atTransactionData.getMessage();
-			if (message.length > 0) {
+
+			if (message != null) {
+				// MESSAGE-type
 				bytes.write(Ints.toByteArray(message.length));
 				bytes.write(message);
 			} else {
-				bytes.write(Ints.toByteArray(0));
+				// PAYMENT-type
+				bytes.write(Longs.toByteArray(atTransactionData.getAssetId()));
+				bytes.write(Longs.toByteArray(atTransactionData.getAmount()));
 			}
 
 			bytes.write(Longs.toByteArray(atTransactionData.getFee()));

src/main/java/org/qortal/transform/transaction/GenesisTransactionTransformer.java

@@ -4,12 +4,8 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 
-import org.qortal.account.NullAccount;
-import org.qortal.data.transaction.BaseTransactionData;
 import org.qortal.data.transaction.GenesisTransactionData;
 import org.qortal.data.transaction.TransactionData;
-import org.qortal.group.Group;
-import org.qortal.transaction.Transaction.TransactionType;
 import org.qortal.transform.TransformationException;
 import org.qortal.utils.Serialization;
 
@@ -18,43 +14,17 @@ import com.google.common.primitives.Longs;
 
 public class GenesisTransactionTransformer extends TransactionTransformer {
 
-	// Note that Genesis transactions don't require reference, fee or signature
+	protected static final TransactionLayout layout = null;
-
-	// Property lengths
-	private static final int RECIPIENT_LENGTH = ADDRESS_LENGTH;
-
-	private static final int TOTAL_LENGTH = TYPE_LENGTH + TIMESTAMP_LENGTH + RECIPIENT_LENGTH + AMOUNT_LENGTH + ASSET_ID_LENGTH;
-
-	protected static final TransactionLayout layout;
-
-	static {
-		layout = new TransactionLayout();
-		layout.add("txType: " + TransactionType.GENESIS.valueString, TransformationType.INT);
-		layout.add("timestamp", TransformationType.TIMESTAMP);
-		layout.add("recipient", TransformationType.ADDRESS);
-		layout.add("amount", TransformationType.AMOUNT);
-		layout.add("asset ID", TransformationType.LONG);
-		layout.add("signature", TransformationType.SIGNATURE);
-	}
 
 	public static TransactionData fromByteBuffer(ByteBuffer byteBuffer) throws TransformationException {
-		long timestamp = byteBuffer.getLong();
+		throw new TransformationException("Serialized GENESIS transactions should not exist!");
-
-		String recipient = Serialization.deserializeAddress(byteBuffer);
-
-		long amount = byteBuffer.getLong();
-
-		long assetId = byteBuffer.getLong();
-
-		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, Group.NO_GROUP, null, NullAccount.PUBLIC_KEY, 0L, null);
-
-		return new GenesisTransactionData(baseTransactionData, recipient, amount, assetId);
 	}
 
 	public static int getDataLength(TransactionData transactionData) throws TransformationException {
-		return TOTAL_LENGTH;
+		throw new TransformationException("Serialized GENESIS transactions should not exist!");
 	}
 
+	// Used when generating fake signatures for genesis block
 	public static byte[] toBytes(TransactionData transactionData) throws TransformationException {
 		try {
 			GenesisTransactionData genesisTransactionData = (GenesisTransactionData) transactionData;