Relayer: query swap/join/exit (V2) (#2521)

pkg/interfaces/contracts/standalone-utils/IBalancerRelayer.sol

@@ -27,4 +27,6 @@ interface IBalancerRelayer {
     function getVault() external view returns (IVault);
 
     function multicall(bytes[] calldata data) external payable returns (bytes[] memory results);
+
+    function vaultActionsQueryMulticall(bytes[] calldata data) external returns (bytes[] memory results);
 }

pkg/standalone-utils/contracts/BatchRelayerQueryLibrary.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+pragma solidity ^0.7.0;
+pragma experimental ABIEncoderV2;
+
+import "./relayer/BaseRelayerLibraryCommon.sol";
+
+import "./relayer/VaultQueryActions.sol";
+
+/**
+ * @title Batch Relayer Library
+ * @notice This contract is not a relayer by itself and calls into it directly will fail.
+ * The associated relayer can be found by calling `getEntrypoint` on this contract.
+ */
+contract BatchRelayerQueryLibrary is BaseRelayerLibraryCommon, VaultQueryActions {
+    constructor(IVault vault) BaseRelayerLibraryCommon(vault) {
+        //solhint-disable-previous-line no-empty-blocks
+    }
+}

pkg/standalone-utils/contracts/relayer/BalancerRelayer.sol

@@ -49,6 +49,7 @@ contract BalancerRelayer is IBalancerRelayer, Version, ReentrancyGuard {
 
     IVault private immutable _vault;
     address private immutable _library;
+    address private immutable _queryLibrary;
 
     /**
      * @dev This contract is not meant to be deployed directly by an EOA, but rather during construction of a contract
@@ -57,10 +58,12 @@ contract BalancerRelayer is IBalancerRelayer, Version, ReentrancyGuard {
     constructor(
         IVault vault,
         address libraryAddress,
+        address queryLibrary,
         string memory version
     ) Version(version) {
         _vault = vault;
         _library = libraryAddress;
+        _queryLibrary = queryLibrary;
     }
 
     receive() external payable {
@@ -80,14 +83,30 @@ contract BalancerRelayer is IBalancerRelayer, Version, ReentrancyGuard {
     }
 
     function multicall(bytes[] calldata data) external payable override nonReentrant returns (bytes[] memory results) {
-        results = new bytes[](data.length);
-        for (uint256 i = 0; i < data.length; i++) {
+        uint256 numData = data.length;
+
+        results = new bytes[](numData);
+        for (uint256 i = 0; i < numData; i++) {
             results[i] = _library.functionDelegateCall(data[i]);
         }
 
         _refundETH();
     }
 
+    function vaultActionsQueryMulticall(bytes[] calldata data)
+        external
+        override
+        nonReentrant
+        returns (bytes[] memory results)
+    {
+        uint256 numData = data.length;
+
+        results = new bytes[](numData);
+        for (uint256 i = 0; i < numData; i++) {
+            results[i] = _queryLibrary.functionDelegateCall(data[i]);
+        }
+    }
+
     function _refundETH() private {
         uint256 remainingEth = address(this).balance;
         if (remainingEth > 0) {

pkg/standalone-utils/contracts/relayer/BaseRelayerLibrary.sol

@@ -20,6 +20,7 @@ import "@balancer-labs/v2-interfaces/contracts/vault/IVault.sol";
 import "@balancer-labs/v2-solidity-utils/contracts/openzeppelin/SafeERC20.sol";
 
 import "./IBaseRelayerLibrary.sol";
+import "../BatchRelayerQueryLibrary.sol";
 import "./BalancerRelayer.sol";
 
 /**
@@ -41,20 +42,19 @@ import "./BalancerRelayer.sol";
  * do not revert in a call involving ETH. This also applies to functions that do not alter the state and would be
  * usually labeled as `view`.
  */
-contract BaseRelayerLibrary is IBaseRelayerLibrary {
+contract BaseRelayerLibrary is BaseRelayerLibraryCommon {
     using Address for address;
     using SafeERC20 for IERC20;
 
     IVault private immutable _vault;
     IBalancerRelayer private immutable _entrypoint;
 
-    constructor(IVault vault, string memory version) IBaseRelayerLibrary(vault.WETH()) {
+    constructor(IVault vault, string memory version) BaseRelayerLibraryCommon(vault) {
         _vault = vault;
-        _entrypoint = new BalancerRelayer(vault, address(this), version);
-    }
 
-    function getVault() public view override returns (IVault) {
-        return _vault;
+        IBaseRelayerLibrary queryLibrary = new BatchRelayerQueryLibrary(vault);
+
+        _entrypoint = new BalancerRelayer(vault, address(this), address(queryLibrary), version);
     }
 
     function getEntrypoint() external view returns (IBalancerRelayer) {
@@ -77,151 +77,4 @@ contract BaseRelayerLibrary is IBaseRelayerLibrary {
 
         address(_vault).functionCall(data);
     }
-
-    /**
-     * @notice Approves the Vault to use tokens held in the relayer
-     * @dev This is needed to avoid having to send intermediate tokens back to the user
-     */
-    function approveVault(IERC20 token, uint256 amount) external payable override {
-        if (_isChainedReference(amount)) {
-            amount = _getChainedReferenceValue(amount);
-        }
-        // TODO: gas golf this a bit
-        token.safeApprove(address(getVault()), amount);
-    }
-
-    /**
-     * @notice Returns the amount referenced by chained reference `ref`.
-     * @dev It does not alter the reference (even if it's marked as temporary).
-     *
-     * This function does not alter the state in any way. It is not marked as view because it has to be `payable`
-     * in order to be used in a batch transaction.
-     *
-     * Use a static call to read the state off-chain.
-     */
-    function peekChainedReferenceValue(uint256 ref) external payable override returns (uint256 value) {
-        (, value) = _peekChainedReferenceValue(ref);
-    }
-
-    function _pullToken(
-        address sender,
-        IERC20 token,
-        uint256 amount
-    ) internal override {
-        if (amount == 0) return;
-        IERC20[] memory tokens = new IERC20[](1);
-        tokens[0] = token;
-        uint256[] memory amounts = new uint256[](1);
-        amounts[0] = amount;
-
-        _pullTokens(sender, tokens, amounts);
-    }
-
-    function _pullTokens(
-        address sender,
-        IERC20[] memory tokens,
-        uint256[] memory amounts
-    ) internal override {
-        IVault.UserBalanceOp[] memory ops = new IVault.UserBalanceOp[](tokens.length);
-        for (uint256 i; i < tokens.length; i++) {
-            ops[i] = IVault.UserBalanceOp({
-                asset: IAsset(address(tokens[i])),
-                amount: amounts[i],
-                sender: sender,
-                recipient: payable(address(this)),
-                kind: IVault.UserBalanceOpKind.TRANSFER_EXTERNAL
-            });
-        }
-
-        getVault().manageUserBalance(ops);
-    }
-
-    /**
-     * @dev Returns true if `amount` is not actually an amount, but rather a chained reference.
-     */
-    function _isChainedReference(uint256 amount) internal pure override returns (bool) {
-        // First 3 nibbles are enough to determine if it's a chained reference.
-        return
-            (amount & 0xfff0000000000000000000000000000000000000000000000000000000000000) ==
-            0xba10000000000000000000000000000000000000000000000000000000000000;
-    }
-
-    /**
-     * @dev Returns true if `ref` is temporary reference, i.e. to be deleted after reading it.
-     */
-    function _isTemporaryChainedReference(uint256 amount) internal pure returns (bool) {
-        // First 3 nibbles determine if it's a chained reference.
-        // If the 4th nibble is 0 it is temporary; otherwise it is considered read-only.
-        // In practice, we shall use '0xba11' for read-only references.
-        return
-            (amount & 0xffff000000000000000000000000000000000000000000000000000000000000) ==
-            0xba10000000000000000000000000000000000000000000000000000000000000;
-    }
-
-    /**
-     * @dev Stores `value` as the amount referenced by chained reference `ref`.
-     */
-    function _setChainedReferenceValue(uint256 ref, uint256 value) internal override {
-        bytes32 slot = _getStorageSlot(ref);
-
-        // Since we do manual calculation of storage slots, it is easier (and cheaper) to rely on internal assembly to
-        // access it.
-        // solhint-disable-next-line no-inline-assembly
-        assembly {
-            sstore(slot, value)
-        }
-    }
-
-    /**
-     * @dev Returns the amount referenced by chained reference `ref`.
-     * If the reference is temporary, it will be cleared after reading it, so they can each only be read once.
-     * If the reference is not temporary (i.e. read-only), it will not be cleared after reading it
-     * (see `_isTemporaryChainedReference` function).
-     */
-    function _getChainedReferenceValue(uint256 ref) internal override returns (uint256) {
-        (bytes32 slot, uint256 value) = _peekChainedReferenceValue(ref);
-
-        if (_isTemporaryChainedReference(ref)) {
-            // solhint-disable-next-line no-inline-assembly
-            assembly {
-                sstore(slot, 0)
-            }
-        }
-        return value;
-    }
-
-    /**
-     * @dev Returns the storage slot for reference `ref` as well as the amount referenced by it.
-     * It does not alter the reference (even if it's marked as temporary).
-     */
-    function _peekChainedReferenceValue(uint256 ref) private view returns (bytes32 slot, uint256 value) {
-        slot = _getStorageSlot(ref);
-
-        // Since we do manual calculation of storage slots, it is easier (and cheaper) to rely on internal assembly to
-        // access it.
-        // solhint-disable-next-line no-inline-assembly
-        assembly {
-            value := sload(slot)
-        }
-    }
-
-    // solhint-disable-next-line var-name-mixedcase
-    bytes32 private immutable _TEMP_STORAGE_SUFFIX = keccak256("balancer.base-relayer-library");
-
-    function _getStorageSlot(uint256 ref) private view returns (bytes32) {
-        // This replicates the mechanism Solidity uses to allocate storage slots for mappings, but using a hash as the
-        // mapping's storage slot, and subtracting 1 at the end. This should be more than enough to prevent collisions
-        // with other state variables this or derived contracts might use.
-        // See https://docs.soliditylang.org/en/v0.8.9/internals/layout_in_storage.html
-
-        return bytes32(uint256(keccak256(abi.encodePacked(_removeReferencePrefix(ref), _TEMP_STORAGE_SUFFIX))) - 1);
-    }
-
-    /**
-     * @dev Returns a reference without its prefix.
-     * Use this function to calculate the storage slot so that it's the same for temporary and read-only references.
-     */
-    function _removeReferencePrefix(uint256 ref) private pure returns (uint256) {
-        return (ref & 0x0000ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
-    }
 }