rpc: adjust NEP5 transfers amount JSON marshalling

This committ fixes the difference between Go and C# nodes:

Go:
```
{
   "jsonrpc" : "2.0",
   "result" : {
      "received" : [
         {
            "blockindex" : 65,
            "txhash" : "0x394f851cf167d664c0dbcf98e2e64f2da23022fd7943dcb914492529de20a945",
            "transfernotifyindex" : 0,
            "timestamp" : 1605535020126,
            "transferaddress" : "NUVPACMnKFhpuHjsRjhUvXz1XhqfGZYVtY",
            "amount" : "29999999",
            "assethash" : "0x668e0c1f9d7b70a99dd9e06eadd4c784d641afbc"
         }
      ],
      "address" : "NULwe3UAHckN2fzNdcVg31tDiaYtMDwANt",
      "sent" : []
   },
   "id" : 1
}
```

C#:
```
{
   "id" : 1,
   "result" : {
      "address" : "NULwe3UAHckN2fzNdcVg31tDiaYtMDwANt",
      "sent" : [],
      "received" : [
	 {
	    "transferaddress" : "NUVPACMnKFhpuHjsRjhUvXz1XhqfGZYVtY",
	    "timestamp" : 1605535020126,
	    "txhash" : "0x394f851cf167d664c0dbcf98e2e64f2da23022fd7943dcb914492529de20a945",
	    "blockindex" : 65,
	    "transfernotifyindex" : 0,
	    "amount" : "2999999900000000",
	    "assethash" : "0x668e0c1f9d7b70a99dd9e06eadd4c784d641afbc"
	 }
      ]
   },
   "jsonrpc" : "2.0"
}
```

pkg/rpc/server/server.go

@@ -554,16 +554,15 @@ func (s *Server) getNEP5Balances(ps request.Params) (interface{}, *response.Erro
 		Balances: []result.NEP5Balance{},
 	}
 	if as != nil {
-		cache := make(map[int32]decimals)
+		cache := make(map[int32]util.Uint160)
 		for id, bal := range as.Trackers {
-			dec, err := s.getDecimals(id, cache)
+			h, err := s.getHash(id, cache)
 			if err != nil {
 				continue
 			}
-			amount := amountToString(&bal.Balance, dec.Value)
 			bs.Balances = append(bs.Balances, result.NEP5Balance{
-				Asset:       dec.Hash,
+				Asset:       h,
-				Amount:      amount,
+				Amount:      bal.Balance.String(),
 				LastUpdated: bal.LastUpdatedBlock,
 			})
 		}
@@ -637,7 +636,7 @@ func (s *Server) getNEP5Transfers(ps request.Params) (interface{}, *response.Err
 		Received: []result.NEP5Transfer{},
 		Sent:     []result.NEP5Transfer{},
 	}
-	cache := make(map[int32]decimals)
+	cache := make(map[int32]util.Uint160)
 	var resCount, frameCount int
 	err = s.chain.ForEachNEP5Transfer(u, func(tr *state.NEP5Transfer) (bool, error) {
 		// Iterating from newest to oldest, not yet reached required
@@ -656,25 +655,25 @@ func (s *Server) getNEP5Transfers(ps request.Params) (interface{}, *response.Err
 			return true, nil
 		}
 
-		d, err := s.getDecimals(tr.Asset, cache)
+		h, err := s.getHash(tr.Asset, cache)
 		if err != nil {
 			return false, err
 		}
 
 		transfer := result.NEP5Transfer{
 			Timestamp: tr.Timestamp,
-			Asset:     d.Hash,
+			Asset:     h,
 			Index:     tr.Block,
 			TxHash:    tr.Tx,
 		}
 		if tr.Amount.Sign() > 0 { // token was received
-			transfer.Amount = amountToString(&tr.Amount, d.Value)
+			transfer.Amount = tr.Amount.String()
 			if !tr.From.Equals(util.Uint160{}) {
 				transfer.Address = address.Uint160ToString(tr.From)
 			}
 			bs.Received = append(bs.Received, transfer)
 		} else {
-			transfer.Amount = amountToString(new(big.Int).Neg(&tr.Amount), d.Value)
+			transfer.Amount = new(big.Int).Neg(&tr.Amount).String()
 			if !tr.To.Equals(util.Uint160{}) {
 				transfer.Address = address.Uint160ToString(tr.To)
 			}
@@ -694,68 +693,17 @@ func (s *Server) getNEP5Transfers(ps request.Params) (interface{}, *response.Err
 	return bs, nil
 }
 
-func amountToString(amount *big.Int, decimals int64) string {
+// getHash returns the hash of the contract by its ID using cache.
-	if decimals == 0 {
+func (s *Server) getHash(contractID int32, cache map[int32]util.Uint160) (util.Uint160, error) {
-		return amount.String()
-	}
-	pow := int64(math.Pow10(int(decimals)))
-	q, r := new(big.Int).DivMod(amount, big.NewInt(pow), new(big.Int))
-	if r.Sign() == 0 {
-		return q.String()
-	}
-	fs := fmt.Sprintf("%%d.%%0%dd", decimals)
-	return fmt.Sprintf(fs, q, r)
-}
-
-// decimals represents decimals value for the contract with the specified scripthash.
-type decimals struct {
-	Hash  util.Uint160
-	Value int64
-}
-
-func (s *Server) getDecimals(contractID int32, cache map[int32]decimals) (decimals, error) {
 	if d, ok := cache[contractID]; ok {
 		return d, nil
 	}
 	h, err := s.chain.GetContractScriptHash(contractID)
 	if err != nil {
-		return decimals{}, err
+		return util.Uint160{}, err
 	}
-	script, err := request.CreateFunctionInvocationScript(h, request.Params{
+	cache[contractID] = h
-		{
+	return h, nil
-			Type:  request.StringT,
-			Value: "decimals",
-		},
-		{
-			Type:  request.ArrayT,
-			Value: []request.Param{},
-		},
-	})
-	if err != nil {
-		return decimals{}, fmt.Errorf("can't create script: %w", err)
-	}
-	res := s.runScriptInVM(script, nil)
-	if res == nil {
-		return decimals{}, fmt.Errorf("execution error: no result")
-	}
-	if res.State != "HALT" {
-		return decimals{}, fmt.Errorf("execution error: bad VM state %s due to an error %s", res.State, res.FaultException)
-	}
-	if len(res.Stack) == 0 {
-		return decimals{}, fmt.Errorf("execution error: empty stack")
-	}
-
-	d := decimals{Hash: h}
-	bi, err := res.Stack[len(res.Stack)-1].TryInteger()
-	if err != nil {
-		return decimals{}, err
-	}
-	d.Value = bi.Int64()
-	if d.Value < 0 {
-		return d, errors.New("incorrect result: negative result")
-	}
-	cache[contractID] = d
-	return d, nil
 }
 
 func (s *Server) contractIDFromParam(param *request.Param) (int32, *response.Error) {

pkg/rpc/server/server_test.go

@@ -1246,7 +1246,7 @@ func checkNep5Balances(t *testing.T, e *executor, acc interface{}) {
 		Balances: []result.NEP5Balance{
 			{
 				Asset:       rubles,
-				Amount:      "8.77",
+				Amount:      "877",
 				LastUpdated: 6,
 			},
 			{
@@ -1256,7 +1256,7 @@ func checkNep5Balances(t *testing.T, e *executor, acc interface{}) {
 			},
 			{
 				Asset:       e.chain.UtilityTokenHash(),
-				Amount:      "800.09641770",
+				Amount:      "80009641770",
 				LastUpdated: 7,
 			}},
 		Address: testchain.PrivateKeyByID(0).GetScriptHash().StringLE(),
@@ -1327,7 +1327,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockDeploy2.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "", // burn
-				Amount:    amountToString(big.NewInt(txDeploy2.SystemFee+txDeploy2.NetworkFee), 8),
+				Amount:    big.NewInt(txDeploy2.SystemFee + txDeploy2.NetworkFee).String(),
 				Index:     7,
 				TxHash:    blockDeploy2.Hash(),
 			},
@@ -1335,7 +1335,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp:   blockSendRubles.Timestamp,
 				Asset:       rublesHash,
 				Address:     testchain.PrivateKeyByID(1).Address(),
-				Amount:      "1.23",
+				Amount:      "123",
 				Index:       6,
 				NotifyIndex: 0,
 				TxHash:      txSendRubles.Hash(),
@@ -1344,7 +1344,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockSendRubles.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "", // burn
-				Amount:    amountToString(big.NewInt(txSendRubles.SystemFee+txSendRubles.NetworkFee), 8),
+				Amount:    big.NewInt(txSendRubles.SystemFee + txSendRubles.NetworkFee).String(),
 				Index:     6,
 				TxHash:    blockSendRubles.Hash(),
 			},
@@ -1352,7 +1352,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockReceiveRubles.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "", // burn
-				Amount:    amountToString(big.NewInt(txReceiveRubles.SystemFee+txReceiveRubles.NetworkFee), 8),
+				Amount:    big.NewInt(txReceiveRubles.SystemFee + txReceiveRubles.NetworkFee).String(),
 				Index:     5,
 				TxHash:    blockReceiveRubles.Hash(),
 			},
@@ -1360,7 +1360,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockReceiveRubles.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "", // burn
-				Amount:    amountToString(big.NewInt(txInitCall.SystemFee+txInitCall.NetworkFee), 8),
+				Amount:    big.NewInt(txInitCall.SystemFee + txInitCall.NetworkFee).String(),
 				Index:     5,
 				TxHash:    blockReceiveRubles.Hash(),
 			},
@@ -1377,7 +1377,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockSendNEO.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "", // burn
-				Amount:    amountToString(big.NewInt(txSendNEO.SystemFee+txSendNEO.NetworkFee), 8),
+				Amount:    big.NewInt(txSendNEO.SystemFee + txSendNEO.NetworkFee).String(),
 				Index:     4,
 				TxHash:    blockSendNEO.Hash(),
 			},
@@ -1385,7 +1385,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockCtrInv1.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "", // burn has empty receiver
-				Amount:    amountToString(big.NewInt(txCtrInv1.SystemFee+txCtrInv1.NetworkFee), 8),
+				Amount:    big.NewInt(txCtrInv1.SystemFee + txCtrInv1.NetworkFee).String(),
 				Index:     3,
 				TxHash:    blockCtrInv1.Hash(),
 			},
@@ -1393,7 +1393,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockCtrDeploy.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "", // burn has empty receiver
-				Amount:    amountToString(big.NewInt(txCtrDeploy.SystemFee+txCtrDeploy.NetworkFee), 8),
+				Amount:    big.NewInt(txCtrDeploy.SystemFee + txCtrDeploy.NetworkFee).String(),
 				Index:     2,
 				TxHash:    blockCtrDeploy.Hash(),
 			},
@@ -1403,7 +1403,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp:   blockGASBounty.Timestamp,
 				Asset:       e.chain.UtilityTokenHash(),
 				Address:     "",
-				Amount:      "0.50000000",
+				Amount:      "50000000",
 				Index:       6,
 				NotifyIndex: 0,
 				TxHash:      blockGASBounty.Hash(),
@@ -1412,7 +1412,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp:   blockReceiveRubles.Timestamp,
 				Asset:       rublesHash,
 				Address:     address.Uint160ToString(rublesHash),
-				Amount:      "10",
+				Amount:      "1000",
 				Index:       5,
 				NotifyIndex: 0,
 				TxHash:      txReceiveRubles.Hash(),
@@ -1421,7 +1421,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp:   blockSendNEO.Timestamp,
 				Asset:       e.chain.UtilityTokenHash(),
 				Address:     "", // Minted GAS.
-				Amount:      "1.49998500",
+				Amount:      "149998500",
 				Index:       4,
 				NotifyIndex: 0,
 				TxHash:      txSendNEO.Hash(),
@@ -1430,7 +1430,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp:   blockReceiveGAS.Timestamp,
 				Asset:       e.chain.UtilityTokenHash(),
 				Address:     testchain.MultisigAddress(),
-				Amount:      "1000",
+				Amount:      "100000000000",
 				Index:       1,
 				NotifyIndex: 0,
 				TxHash:      txReceiveGAS.Hash(),
@@ -1448,7 +1448,7 @@ func checkNep5TransfersAux(t *testing.T, e *executor, acc interface{}, sent, rcv
 				Timestamp: blockGASBounty0.Timestamp,
 				Asset:     e.chain.UtilityTokenHash(),
 				Address:   "",
-				Amount:    "0.50000000",
+				Amount:    "50000000",
 				Index:     0,
 				TxHash:    blockGASBounty0.Hash(),
 			},