Add StackItem.ToJson()

src/neo/IO/ReferenceEqualityComparer.cs

@@ -0,0 +1,25 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+namespace Neo.IO
+{
+    internal sealed class ReferenceEqualityComparer : IEqualityComparer, IEqualityComparer<object>
+    {
+        public static readonly ReferenceEqualityComparer Default = new ReferenceEqualityComparer();
+
+        private ReferenceEqualityComparer()
+        {
+        }
+
+        public new bool Equals(object x, object y)
+        {
+            return x == y;
+        }
+
+        public int GetHashCode(object obj)
+        {
+            return RuntimeHelpers.GetHashCode(obj);
+        }
+    }
+}

src/neo/VM/Helper.cs

@@ -1,5 +1,6 @@
 using Neo.Cryptography.ECC;
 using Neo.IO;
+using Neo.IO.Json;
 using Neo.SmartContract;
 using Neo.VM.Types;
 using System;
@@ -219,6 +220,52 @@ public static byte[] MakeScript(this UInt160 scriptHash, string operation, param
             }
         }
 
+        public static JObject ToJson(this StackItem item)
+        {
+            return ToJson(item, null);
+        }
+
+        private static JObject ToJson(StackItem item, HashSet<StackItem> context)
+        {
+            JObject json = new JObject();
+            json["type"] = item.Type;
+            switch (item)
+            {
+                case Array array:
+                    context ??= new HashSet<StackItem>(ReferenceEqualityComparer.Default);
+                    if (!context.Add(array)) throw new InvalidOperationException();
+                    json["value"] = new JArray(array.Select(p => ToJson(p, context)));
+                    break;
+                case Boolean boolean:
+                    json["value"] = boolean.ToBoolean();
+                    break;
+                case Buffer buffer:
+                    json["value"] = Convert.ToBase64String(buffer.InnerBuffer);
+                    break;
+                case ByteString byteString:
+                    json["value"] = Convert.ToBase64String(byteString.Span);
+                    break;
+                case Integer integer:
+                    json["value"] = integer.ToBigInteger().ToString();
+                    break;
+                case Map map:
+                    context ??= new HashSet<StackItem>(ReferenceEqualityComparer.Default);
+                    if (!context.Add(map)) throw new InvalidOperationException();
+                    json["value"] = new JArray(map.Select(p =>
+                    {
+                        JObject item = new JObject();
+                        item["key"] = ToJson(p.Key, context);
+                        item["value"] = ToJson(p.Value, context);
+                        return item;
+                    }));
+                    break;
+                case Pointer pointer:
+                    json["value"] = pointer.Position;
+                    break;
+            }
+            return json;
+        }
+
         public static ContractParameter ToParameter(this StackItem item)
         {
             return ToParameter(item, null);

tests/neo.UnitTests/VM/UT_Helper.cs

@@ -26,6 +26,27 @@ public void TestEmit()
             CollectionAssert.AreEqual(new[] { (byte)OpCode.PUSH0 }, sb.ToArray());
         }
 
+        [TestMethod]
+        public void TestToJson()
+        {
+            var item = new VM.Types.Array();
+            item.Add(5);
+            item.Add("hello world");
+            item.Add(new byte[] { 1, 2, 3 });
+            item.Add(true);
+
+            Assert.AreEqual("{\"type\":\"Integer\",\"value\":\"5\"}", item[0].ToJson().ToString());
+            Assert.AreEqual("{\"type\":\"ByteString\",\"value\":\"aGVsbG8gd29ybGQ=\"}", item[1].ToJson().ToString());
+            Assert.AreEqual("{\"type\":\"ByteString\",\"value\":\"AQID\"}", item[2].ToJson().ToString());
+            Assert.AreEqual("{\"type\":\"Boolean\",\"value\":true}", item[3].ToJson().ToString());
+            Assert.AreEqual("{\"type\":\"Array\",\"value\":[{\"type\":\"Integer\",\"value\":\"5\"},{\"type\":\"ByteString\",\"value\":\"aGVsbG8gd29ybGQ=\"},{\"type\":\"ByteString\",\"value\":\"AQID\"},{\"type\":\"Boolean\",\"value\":true}]}", item.ToJson().ToString());
+
+            var item2 = new VM.Types.Map();
+            item2[1] = new Pointer(new Script(new byte[0]), 0);
+
+            Assert.AreEqual("{\"type\":\"Map\",\"value\":[{\"key\":{\"type\":\"Integer\",\"value\":\"1\"},\"value\":{\"type\":\"Pointer\",\"value\":0}}]}", item2.ToJson().ToString());
+        }
+
         [TestMethod]
         public void TestEmitAppCall1()
         {