feat(forwarders): add dandelion voting forwarders

contracts/forwarder/CrossExecutor.sol

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.17;
+
+import {Context} from "@openzeppelin/contracts/utils/Context.sol";
+import {IERC777Recipient} from "@openzeppelin/contracts/token/ERC777/IERC777Recipient.sol";
+import {IERC1820Registry} from "@openzeppelin/contracts/interfaces/IERC1820Registry.sol";
+import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
+
+error CallFailed(address target, bytes data);
+error InvalidCallParams(address[] targets, bytes[] data, address caller);
+error InvalidOriginAddress(address originAddress);
+error InvalidCaller(address caller, address expected);
+
+contract CrossExecutor is IERC777Recipient, Context, Ownable {
+    address public immutable token;
+    address public immutable sender;
+    mapping(address => bool) private _whitelistedOriginAddresses;
+
+    constructor(address _token, address _sender) {
+        IERC1820Registry(0x1820a4B7618BdE71Dce8cdc73aAB6C95905faD24).setInterfaceImplementer(
+            address(this),
+            keccak256("ERC777TokensRecipient"),
+            address(this)
+        );
+
+        token = _token;
+        sender = _sender; // set it to 0 on an host chain, vault address on a native chain
+    }
+
+    function tokensReceived(
+        address /*_operator*/,
+        address _from,
+        address /*_to,*/,
+        uint256 /*_amount*/,
+        bytes calldata _metaData,
+        bytes calldata /*_operatorData*/
+    ) external override {
+        if (_msgSender() == token && _from == sender) {
+            (, bytes memory callsAndTargets, , address originAddress, , , , ) = abi.decode(
+                _metaData,
+                (bytes1, bytes, bytes4, address, bytes4, address, bytes, bytes)
+            );
+
+            if (!_whitelistedOriginAddresses[originAddress]) {
+                revert InvalidOriginAddress(originAddress);
+            }
+
+            (address[] memory targets, bytes[] memory data) = abi.decode(callsAndTargets, (address[], bytes[]));
+
+            if (targets.length != data.length) {
+                revert InvalidCallParams(targets, data, originAddress);
+            }
+
+            for (uint256 i = 0; i < targets.length; ) {
+                (bool success, ) = targets[i].call(data[i]);
+                if (!success) {
+                    revert CallFailed(targets[i], data[i]);
+                }
+                unchecked {
+                    ++i;
+                }
+            }
+        }
+    }
+
+    function whitelistOriginAddress(address originAddress) external onlyOwner {
+        _whitelistedOriginAddresses[originAddress] = true;
+    }
+}

contracts/interfaces/external/IErc20Vault.sol

@@ -3,11 +3,28 @@
 pragma solidity ^0.8.17;
 
 interface IErc20Vault {
+    event PegIn(
+        address _tokenAddress,
+        address _tokenSender,
+        uint256 _tokenAmount,
+        string _destinationAddress,
+        bytes _userData,
+        bytes4 _originChainId,
+        bytes4 _destinationChainId
+    );
+
     function pegIn(
         uint256 tokenAmount,
         address tokenAddress,
         string memory destinationAddress,
         bytes memory userData,
         bytes4 destinationChainId
     ) external returns (bool);
+
+    function pegOut(
+        address payable _tokenRecipient,
+        address _tokenAddress,
+        uint256 _tokenAmount,
+        bytes calldata _userData
+    ) external returns (bool success);
 }

lib/metadata.js

@@ -0,0 +1,58 @@
+// Refs: https://github.com/pnetwork-association/ptokens-core/blob/master/common/metadata/src/metadata_encoders.rs#L24-L49
+const METADATA_TYPES = [
+  'bytes1', // version
+  'bytes', // userData
+  'bytes4', // sourceNetworkId
+  'address', // senderAddress
+  'bytes4', // destinationNetworkId
+  'address', // receiverAddress
+  'bytes', // protocolOptions
+  'bytes' // protocolReceipt
+]
+
+module.exports.decodeMetadata = (_ethers, _metadata) => {
+  const [
+    version,
+    userData,
+    sourceNetworkId,
+    senderAddress,
+    destinationNetworkId,
+    receiverAddress,
+    protocolOptions,
+    protocolReceipt
+  ] = _ethers.AbiCoder.defaultAbiCoder().decode(METADATA_TYPES, _metadata)
+  return {
+    version,
+    userData,
+    sourceNetworkId,
+    senderAddress,
+    destinationNetworkId,
+    receiverAddress,
+    protocolOptions,
+    protocolReceipt
+  }
+}
+
+module.exports.encodeMetadata = (
+  _ethers,
+  {
+    version = '0x02',
+    userData,
+    sourceNetworkId,
+    senderAddress,
+    destinationNetworkId,
+    receiverAddress,
+    protocolOptions = '0x',
+    protocolReceipt = '0x'
+  }
+) =>
+  _ethers.AbiCoder.defaultAbiCoder().encode(METADATA_TYPES, [
+    version,
+    userData,
+    sourceNetworkId,
+    senderAddress,
+    destinationNetworkId,
+    receiverAddress,
+    protocolOptions,
+    protocolReceipt
+  ])