Implement NEP-17

src/neo/SmartContract/ApplicationEngine.Contract.cs

@@ -18,6 +18,7 @@ partial class ApplicationEngine
         public static readonly InteropDescriptor System_Contract_Create = Register("System.Contract.Create", nameof(CreateContract), 0, CallFlags.AllowModifyStates, false);
         public static readonly InteropDescriptor System_Contract_Update = Register("System.Contract.Update", nameof(UpdateContract), 0, CallFlags.AllowModifyStates, false);
         public static readonly InteropDescriptor System_Contract_Destroy = Register("System.Contract.Destroy", nameof(DestroyContract), 0_01000000, CallFlags.AllowModifyStates, false);
+        public static readonly InteropDescriptor System_Contract_MethodExists = Register("System.Contract.MethodExists", nameof(MethodExists), 0_01000000, CallFlags.AllowCall, false);
         public static readonly InteropDescriptor System_Contract_Call = Register("System.Contract.Call", nameof(CallContract), 0_01000000, CallFlags.AllowCall, false);
         public static readonly InteropDescriptor System_Contract_CallEx = Register("System.Contract.CallEx", nameof(CallContractEx), 0_01000000, CallFlags.AllowCall, false);
         public static readonly InteropDescriptor System_Contract_IsStandard = Register("System.Contract.IsStandard", nameof(IsStandardContract), 0_00030000, CallFlags.AllowStates, true);
@@ -118,6 +119,17 @@ protected internal void DestroyContract()
                     Snapshot.Storages.Delete(key);
         }
 
+        protected internal bool MethodExists(UInt160 contractHash, string method)
+        {
+            if (contractHash is null) return false;
+            if (string.IsNullOrEmpty(method)) return false;
+
+            ContractState contract = Snapshot.Contracts.TryGet(contractHash);
+            if (contract is null) return false;
+
+            return contract.Manifest.Abi.GetMethod(method) != null;
+        }
+
         protected internal void CallContract(UInt160 contractHash, string method, Array args)
         {
             CallContractEx(contractHash, method, args, CallFlags.All);

src/neo/SmartContract/Native/Tokens/Nep5Token.cs

@@ -68,7 +68,21 @@ internal protected virtual void Mint(ApplicationEngine engine, UInt160 account,
             state.Balance += amount;
             storage = engine.Snapshot.Storages.GetAndChange(CreateStorageKey(Prefix_TotalSupply), () => new StorageItem(BigInteger.Zero));
             storage.Add(amount);
-            engine.SendNotification(Hash, "Transfer", new Array { StackItem.Null, account.ToArray(), amount });
+            onPostTransfer(engine, null, account, amount);
+        }
+
+        private void onPostTransfer(ApplicationEngine engine, UInt160 from, UInt160 to, BigInteger amount)
+        {
+            // Send notification
+
+            engine.SendNotification(Hash, "Transfer",
+                new Array { from == null ? StackItem.Null : from.ToArray(), to == null ? StackItem.Null : to.ToArray(), amount });
+
+            if (!engine.MethodExists(to, "onPayment")) return;
+
+            // Call onPayment method if exists
+
+            engine.CallFromNativeContract(() => { }, to, "onPayment", new Array(engine.ReferenceCounter) { amount });
         }
 
         internal protected virtual void Burn(ApplicationEngine engine, UInt160 account, BigInteger amount)
@@ -86,7 +100,7 @@ internal protected virtual void Burn(ApplicationEngine engine, UInt160 account,
                 state.Balance -= amount;
             storage = engine.Snapshot.Storages.GetAndChange(CreateStorageKey(Prefix_TotalSupply));
             storage.Add(-amount);
-            engine.SendNotification(Hash, "Transfer", new Array { account.ToArray(), StackItem.Null, amount });
+            onPostTransfer(engine, account, null, amount);
         }
 
         [ContractMethod(0_01000000, CallFlags.AllowStates)]
@@ -105,7 +119,7 @@ public virtual BigInteger BalanceOf(StoreView snapshot, UInt160 account)
             return storage.GetInteroperable<TState>().Balance;
         }
 
-        [ContractMethod(0_08000000, CallFlags.AllowModifyStates)]
+        [ContractMethod(0_09000000, CallFlags.AllowModifyStates)]
         protected virtual bool Transfer(ApplicationEngine engine, UInt160 from, UInt160 to, BigInteger amount)
         {
             if (amount.Sign < 0) throw new ArgumentOutOfRangeException(nameof(amount));
@@ -146,7 +160,7 @@ protected virtual bool Transfer(ApplicationEngine engine, UInt160 from, UInt160
                     state_to.Balance += amount;
                 }
             }
-            engine.SendNotification(Hash, "Transfer", new Array { from.ToArray(), to.ToArray(), amount });
+            onPostTransfer(engine, from, to, amount);
             return true;
         }