Improve Gateway API for sending tokens to Polkadot

contracts/src/Assets.sol

@@ -9,7 +9,7 @@ import {SafeTokenTransferFrom} from "./utils/SafeTransfer.sol";
 
 import {AssetsStorage} from "./storage/AssetsStorage.sol";
 import {SubstrateTypes} from "./SubstrateTypes.sol";
-import {ParaID} from "./Types.sol";
+import {ParaID, MultiAddress} from "./Types.sol";
 import {Address} from "./utils/Address.sol";
 
 /// @title Library for implementing Ethereum->Polkadot ERC20 transfers.
@@ -21,6 +21,7 @@ library Assets {
     error InvalidToken();
     error InvalidAmount();
     error InvalidDestination();
+    error Unsupported();
 
     // This library requires state which must be initialized in the gateway's storage.
     function initialize(uint256 registerTokenFee, uint256 sendTokenFee) external {
@@ -30,26 +31,17 @@ library Assets {
         $.sendTokenFee = sendTokenFee;
     }
 
-    function sendToken(
-        ParaID assetHubParaID,
-        address assetHubAgent,
-        address token,
-        address sender,
-        ParaID destinationChain,
-        bytes32 destinationAddress,
-        uint128 amount
-    ) external returns (bytes memory payload, uint256 extraFee) {
-        AssetsStorage.Layout storage $ = AssetsStorage.layout();
+    /// @dev transfer tokens from the sender to the specified
+    function _transferToAgent(address assetHubAgent, address token, address sender, uint128 amount) internal {
+        if (!token.isContract()) {
+            revert InvalidToken();
+        }
 
-        _transferToAgent(assetHubAgent, token, sender, amount);
-        if (destinationChain == assetHubParaID) {
-            payload = SubstrateTypes.SendToken(token, destinationAddress, amount);
-        } else {
-            payload = SubstrateTypes.SendToken(token, destinationChain, destinationAddress, amount);
+        if (amount == 0) {
+            revert InvalidAmount();
         }
-        extraFee = $.sendTokenFee;
 
-        emit IGateway.TokenSent(sender, token, destinationChain, abi.encodePacked(destinationAddress), amount);
+        IERC20(token).safeTransferFrom(sender, assetHubAgent, amount);
     }
 
     function sendToken(
@@ -58,34 +50,35 @@ library Assets {
         address token,
         address sender,
         ParaID destinationChain,
-        address destinationAddress,
+        MultiAddress calldata destinationAddress,
         uint128 amount
     ) external returns (bytes memory payload, uint256 extraFee) {
         AssetsStorage.Layout storage $ = AssetsStorage.layout();
-        if (destinationChain == assetHubParaID) {
-            // AssetHub parachain doesn't support Ethereum-style addresses
-            revert InvalidDestination();
-        }
 
         _transferToAgent(assetHubAgent, token, sender, amount);
 
-        payload = SubstrateTypes.SendToken(address(this), token, destinationChain, destinationAddress, amount);
-        extraFee = $.sendTokenFee;
-
-        emit IGateway.TokenSent(sender, token, destinationChain, abi.encodePacked(destinationAddress), amount);
-    }
-
-    /// @dev transfer tokens from the sender to the specified
-    function _transferToAgent(address assetHubAgent, address token, address sender, uint128 amount) internal {
-        if (!token.isContract()) {
-            revert InvalidToken();
-        }
-
-        if (amount == 0) {
-            revert InvalidAmount();
+        if (destinationChain == assetHubParaID) {
+            if (destinationAddress.isAddress32()) {
+                payload = SubstrateTypes.SendTokenToAssetHubAddress32(token, destinationAddress.asAddress32(), amount);
+            } else {
+                revert Unsupported();
+            }
+        } else {
+            if (destinationAddress.isAddress32()) {
+                payload = SubstrateTypes.SendTokenToAddress32(
+                    token, destinationChain, destinationAddress.asAddress32(), amount
+                );
+            } else if (destinationAddress.isAddress20()) {
+                payload = SubstrateTypes.SendTokenToAddress20(
+                    token, destinationChain, destinationAddress.asAddress20(), amount
+                );
+            } else {
+                revert Unsupported();
+            }
         }
+        extraFee = $.sendTokenFee;
 
-        IERC20(token).safeTransferFrom(sender, assetHubAgent, amount);
+        emit IGateway.TokenSent(sender, token, destinationChain, destinationAddress, amount);
     }
 
     /// @dev Enqueues a create native token message to substrate.

contracts/src/Gateway.sol

@@ -8,7 +8,7 @@ import {Verification} from "./Verification.sol";
 import {Assets} from "./Assets.sol";
 import {AgentExecutor} from "./AgentExecutor.sol";
 import {Agent} from "./Agent.sol";
-import {Channel, ChannelID, InboundMessage, OperatingMode, ParaID, Command} from "./Types.sol";
+import {Channel, ChannelID, InboundMessage, OperatingMode, ParaID, Command, MultiAddress} from "./Types.sol";
 import {IGateway} from "./interfaces/IGateway.sol";
 import {IInitializable} from "./interfaces/IInitializable.sol";
 import {ERC1967} from "./utils/ERC1967.sol";
@@ -454,22 +454,7 @@ contract Gateway is IGateway, IInitializable {
     }
 
     // Transfer ERC20 tokens to a Polkadot parachain
-    function sendToken(address token, ParaID destinationChain, bytes32 destinationAddress, uint128 amount)
-        external
-        payable
-    {
-        CoreStorage.Layout storage $ = CoreStorage.layout();
-        address assetHubAgent = $.agents[ASSET_HUB_AGENT_ID];
-
-        (bytes memory payload, uint256 extraFee) = Assets.sendToken(
-            ASSET_HUB_PARA_ID, assetHubAgent, token, msg.sender, destinationChain, destinationAddress, amount
-        );
-
-        _submitOutbound(ASSET_HUB_PARA_ID, payload, extraFee);
-    }
-
-    // Transfer ERC20 tokens to a Polkadot parachain
-    function sendToken(address token, ParaID destinationChain, address destinationAddress, uint128 amount)
+    function sendToken(address token, ParaID destinationChain, MultiAddress calldata destinationAddress, uint128 amount)
         external
         payable
     {

contracts/src/MultiAddress.sol

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2023 Snowfork <[email protected]>
+pragma solidity 0.8.22;
+
+using {isIndex, asIndex, isAddress32, asAddress32, isAddress20, asAddress20} for MultiAddress global;
+
+/// @dev An address for an on-chain account
+struct MultiAddress {
+    Kind kind;
+    bytes data;
+}
+
+enum Kind {
+    Index,
+    Address32,
+    Address20
+}
+
+function isIndex(MultiAddress calldata multiAddress) pure returns (bool) {
+    return multiAddress.kind == Kind.Index;
+}
+
+function asIndex(MultiAddress calldata multiAddress) pure returns (uint32) {
+    return abi.decode(multiAddress.data, (uint32));
+}
+
+function isAddress32(MultiAddress calldata multiAddress) pure returns (bool) {
+    return multiAddress.kind == Kind.Address32;
+}
+
+function asAddress32(MultiAddress calldata multiAddress) pure returns (bytes32) {
+    return bytes32(multiAddress.data);
+}
+
+function isAddress20(MultiAddress calldata multiAddress) pure returns (bool) {
+    return multiAddress.kind == Kind.Address20;
+}
+
+function asAddress20(MultiAddress calldata multiAddress) pure returns (bytes20) {
+    return bytes20(multiAddress.data);
+}
+
+function multiAddressFromUint32(uint32 id) pure returns (MultiAddress memory) {
+    return MultiAddress({kind: Kind.Index, data: abi.encode(id)});
+}
+
+function multiAddressFromBytes32(bytes32 id) pure returns (MultiAddress memory) {
+    return MultiAddress({kind: Kind.Address32, data: bytes.concat(id)});
+}
+
+function multiAddressFromBytes20(bytes20 id) pure returns (MultiAddress memory) {
+    return MultiAddress({kind: Kind.Address20, data: bytes.concat(id)});
+}

contracts/src/SubstrateTypes.sol

@@ -66,8 +66,12 @@ library SubstrateTypes {
      * @dev SCALE-encodes `router_primitives::inbound::VersionedMessage` containing payload
      * `NativeTokensMessage::Mint`
      */
-    // solhint-disable-next-line func-name-mixedcase
-    function SendToken(address token, bytes32 recipient, uint128 amount) internal view returns (bytes memory) {
+    // destination is AccountID32 address on AssetHub
+    function SendTokenToAssetHubAddress32(address token, bytes32 recipient, uint128 amount)
+        internal
+        view
+        returns (bytes memory)
+    {
         return bytes.concat(
             bytes1(0x00),
             ScaleCodec.encodeU64(uint64(block.chainid)),
@@ -79,7 +83,8 @@ library SubstrateTypes {
         );
     }
 
-    function SendToken(address token, ParaID paraID, bytes32 recipient, uint128 amount)
+    // destination is AccountID32 address
+    function SendTokenToAddress32(address token, ParaID paraID, bytes32 recipient, uint128 amount)
         internal
         view
         returns (bytes memory)
@@ -96,7 +101,8 @@ library SubstrateTypes {
         );
     }
 
-    function SendToken(address gateway, address token, ParaID paraID, address recipient, uint128 amount)
+    // destination is AccountID20 address
+    function SendTokenToAddress20(address token, ParaID paraID, bytes20 recipient, uint128 amount)
         internal
         view
         returns (bytes memory)
@@ -105,11 +111,10 @@ library SubstrateTypes {
             bytes1(0x00),
             ScaleCodec.encodeU64(uint64(block.chainid)),
             bytes1(0x01),
-            SubstrateTypes.H160(gateway),
             SubstrateTypes.H160(token),
             bytes1(0x02),
             ScaleCodec.encodeU32(uint32(ParaID.unwrap(paraID))),
-            abi.encodePacked(recipient),
+            recipient,
             ScaleCodec.encodeU128(amount)
         );
     }

contracts/src/Types.sol

@@ -2,6 +2,10 @@
 // SPDX-FileCopyrightText: 2023 Snowfork <[email protected]>
 pragma solidity 0.8.22;
 
+import {
+    MultiAddress, multiAddressFromUint32, multiAddressFromBytes32, multiAddressFromBytes20
+} from "./MultiAddress.sol";
+
 type ParaID is uint32;
 
 using {ParaIDEq as ==, ParaIDNe as !=, into} for ParaID global;

contracts/src/interfaces/IGateway.sol

@@ -2,7 +2,7 @@
 // SPDX-FileCopyrightText: 2023 Snowfork <[email protected]>
 pragma solidity 0.8.22;
 
-import {OperatingMode, InboundMessage, ParaID, ChannelID} from "../Types.sol";
+import {OperatingMode, InboundMessage, ParaID, ChannelID, MultiAddress} from "../Types.sol";
 import {Verification} from "../Verification.sol";
 
 interface IGateway {
@@ -65,7 +65,11 @@ interface IGateway {
 
     /// @dev Emitted once the funds are locked and an outbound message is successfully queued.
     event TokenSent(
-        address indexed token, address indexed sender, ParaID destinationChain, bytes destinationAddress, uint128 amount
+        address indexed token,
+        address indexed sender,
+        ParaID destinationChain,
+        MultiAddress destinationAddress,
+        uint128 amount
     );
 
     /// @dev Emitted when a command is sent to register a new wrapped token on AssetHub
@@ -79,12 +83,7 @@ interface IGateway {
     function registerToken(address token) external payable;
 
     /// @dev Send ERC20 tokens to parachain `destinationChain` and deposit into account `destinationAddress`
-    function sendToken(address token, ParaID destinationChain, bytes32 destinationAddress, uint128 amount)
-        external
-        payable;
-
-    /// @dev Send ERC20 tokens to parachain `destinationChain` and deposit into account `destinationAddress`
-    function sendToken(address token, ParaID destinationChain, address destinationAddress, uint128 amount)
+    function sendToken(address token, ParaID destinationChain, MultiAddress calldata destinationAddress, uint128 amount)
         external
         payable;
 }