Added validator class for NEP-17 contract

src/neoxp/Node/OfflineNode.cs

@@ -22,10 +22,10 @@
 using Neo.SmartContract;
 using Neo.SmartContract.Manifest;
 using Neo.SmartContract.Native;
-using Neo.VM;
 using Neo.Wallets;
 using NeoExpress.Commands;
 using NeoExpress.Models;
+using NeoExpress.Validators.Tokens;
 using System.Numerics;
 using static Neo.Ledger.Blockchain;
 
@@ -295,30 +295,14 @@ public Task<uint> GetTransactionHeightAsync(UInt256 txHash)
                 .Where(c => c.standard == TokenStandard.Nep17)
                 .ToList();
 
-            var addressArray = address.ToArray();
-            using var builder = new ScriptBuilder();
-            for (var i = contracts.Count; i-- > 0;)
-            {
-                builder.EmitDynamicCall(contracts[i].scriptHash, "symbol");
-                builder.EmitDynamicCall(contracts[i].scriptHash, "decimals");
-                builder.EmitDynamicCall(contracts[i].scriptHash, "balanceOf", addressArray);
-            }
-
             List<(TokenContract contract, BigInteger balance)> balances = new();
-            using var engine = builder.Invoke(neoSystem.Settings, snapshot);
-            if (engine.State != VMState.FAULT && engine.ResultStack.Count == contracts.Count * 3)
+            for (int i = contracts.Count; i-- > 0;)
             {
-                var resultStack = engine.ResultStack;
-                for (var i = 0; i < contracts.Count; i++)
-                {
-                    var index = i * 3;
-                    var symbol = resultStack.Peek(index + 2).GetString();
-                    if (symbol is null)
-                        continue;
-                    var decimals = (byte)resultStack.Peek(index + 1).GetInteger();
-                    var balance = resultStack.Peek(index).GetInteger();
-                    balances.Add((new TokenContract(symbol, decimals, contracts[i].scriptHash, contracts[i].standard), balance));
-                }
+                // Note: this will throw error NotSupportedException if NEP-17 is not compliant.
+                // A check maybe added for exception in future, if crashes because SupportStandard
+                // invalid.
+                var nep17Contract = new Nep17Token(ProtocolSettings, snapshot, contracts[i].scriptHash);
+                balances.Add((new TokenContract(nep17Contract.Symbol, nep17Contract.Decimals, contracts[i].scriptHash, contracts[i].standard), nep17Contract.BalanceOf(address)));
             }
 
             return balances;

src/neoxp/Validators/Tokens/Nep17Token.cs

@@ -0,0 +1,24 @@
+// Copyright (C) 2015-2023 The Neo Project.
+//
+// The neo is free software distributed under the MIT software license,
+// see the accompanying file LICENSE in the main directory of the
+// project or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using Neo;
+using Neo.Persistence;
+
+namespace NeoExpress.Validators.Tokens;
+
+internal class Nep17Token : TokenBase
+{
+    public Nep17Token(
+        ProtocolSettings protocolSettings,
+        DataCache snapshot,
+        UInt160 scriptHash) : base(protocolSettings, snapshot, scriptHash)
+    {
+    }
+}

src/neoxp/Validators/Tokens/TokenBase.cs

@@ -0,0 +1,71 @@
+// Copyright (C) 2015-2023 The Neo Project.
+//
+// The neo is free software distributed under the MIT software license,
+// see the accompanying file LICENSE in the main directory of the
+// project or http://www.opensource.org/licenses/mit-license.php
+// for more details.
+//
+// Redistribution and use in source and binary forms with or without
+// modifications are permitted.
+
+using Neo;
+using Neo.Persistence;
+using Neo.SmartContract;
+using Neo.VM;
+using System.Numerics;
+
+namespace NeoExpress.Validators.Tokens;
+
+internal abstract class TokenBase
+{
+    public UInt160 ScriptHash { get; private init; }
+    public string Symbol { get; private set; }
+    public byte Decimals { get; private set; }
+
+    protected readonly DataCache _snapshot;
+    protected readonly ProtocolSettings _protocolSettings;
+
+    public TokenBase(
+        ProtocolSettings protocolSettings,
+        DataCache snapshot,
+        UInt160 scriptHash)
+    {
+        _protocolSettings = protocolSettings;
+        _snapshot = snapshot;
+        ScriptHash = scriptHash;
+
+        using var builder = new ScriptBuilder();
+        builder.EmitDynamicCall(ScriptHash, "decimals");
+        builder.EmitDynamicCall(ScriptHash, "symbol");
+
+        using var engine = builder.Invoke(_protocolSettings, _snapshot);
+        if (engine.State != VMState.HALT)
+            throw new NotSupportedException($"{ScriptHash} is not NEP-17 compliant.");
+
+        var results = engine.ResultStack;
+        Symbol = results.Pop().GetString()!;
+        Decimals = checked((byte)results.Pop().GetInteger());
+    }
+
+    public BigInteger TotalSupply()
+    {
+        using var builder = new ScriptBuilder();
+        builder.EmitDynamicCall(ScriptHash, "totalSupply");
+
+        using var appEng = builder.Invoke(_protocolSettings, _snapshot);
+        if (appEng.State == VMState.HALT)
+            return appEng.ResultStack.Pop().GetInteger();
+        throw new InvalidOperationException();
+    }
+
+    public BigInteger BalanceOf(UInt160 owner)
+    {
+        using var builder = new ScriptBuilder();
+        builder.EmitDynamicCall(ScriptHash, "balanceOf", owner);
+
+        using var appEng = builder.Invoke(_protocolSettings, _snapshot);
+        if (appEng.State == VMState.HALT)
+            return appEng.ResultStack.Pop().GetInteger();
+        throw new InvalidOperationException();
+    }
+}