refactor: some optimize

Signed-off-by: MASDXI <sirawitt42@gmail.com>

Author: MASDXI

contracts/abstracts/ForestToken.sol

@@ -13,7 +13,7 @@ import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
  */
 abstract contract ForestToken is ERC20, IForest {
     using Forest for Forest.DAG;
-
+    
     Forest.DAG private _dag;
 
     /**

contracts/abstracts/UTXOToken.sol

@@ -54,12 +54,11 @@ abstract contract UTXOToken is ERC20, IUTXO {
             revert UTXOTransferOverTransactionValue(txvalue, value);
         }
         _UTXO.spendTx(UTXO.TxInput(tokenId, signature), from);
-        uint256 change = txvalue - value;
-        if (change != 0) {
+        txvalue = txvalue - value;
+        if (txvalue != 0) {
             _UTXO.createTx(
                 UTXO.TxOutput(value, to),
                 tokenId,
-                UTXO.calcTxHash(from, _UTXO.getTxCount(from)),
                 from,
                 extraData
             );
@@ -77,7 +76,6 @@ abstract contract UTXOToken is ERC20, IUTXO {
         _UTXO.createTx(
             UTXO.TxOutput(value, account),
             bytes32(0),
-            UTXO.calcTxHash(address(0), _UTXO.getTxCount(address(0))),
             address(0),
             extraData
         );
@@ -95,11 +93,11 @@ abstract contract UTXOToken is ERC20, IUTXO {
         if (value == _UTXO.getTxValue(tokenId)) {
             _UTXO.consumeTx(tokenId);
         } else {
+            // @TODO handling not allow value greater than tx value.
             _UTXO.consumeTx(tokenId);
             _UTXO.createTx(
                 UTXO.TxOutput(value, account),
                 tokenId,
-                UTXO.calcTxHash(account, _UTXO.getTxCount(account)),
                 account,
                 extraData
             );

contracts/libraries/UTXO.sol

@@ -119,25 +119,24 @@ library UnspentTransactionOutput {
      * @param self The UTXO storage.
      * @param txOutput The transaction output details.
      * @param input The input identifier of the transaction.
-     * @param id The identifier of the transaction.
      * @param creator The creator of the transaction.
      */
     function createTx(
         UTXO storage self,
         TxOutput memory txOutput,
         bytes32 input,
-        bytes32 id,
         address creator,
         bytes32 extraData
     ) internal {
         if (txOutput.value == 0) {
             revert TransactionZeroValue();
         }
-        if (_transactionExist(self, id)) {
-            revert TransactionExist();
-        }
+        uint256 nonce = self.nonces[creator];
+        bytes32 id = calcTxHash(creator, self.nonces[creator]);
         self.txs[id] = Tx(input, txOutput.value, txOutput.account, false, extraData);
-        self.nonces[creator]++;
+        unchecked {
+            self.nonces[creator] = nonce++;
+        }
 
         emit TransactionCreated(id, creator, txOutput.account);
     }
@@ -167,7 +166,7 @@ library UnspentTransactionOutput {
     }
 
     /**
-     * @notice Consumes (marks as spent) a transaction in the UTXO.
+     * @notice Consumes (marks as spent without require signature) a transaction in the UTXO.
      * @param self The UTXO storage.
      * @param id The identifier of the transaction to consume.
      */