chore: Add BalancerSwapExecutor

evm/src/balancer-v2/BalancerSwapExecutor.sol

@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: UNLICENCED
+pragma solidity ^0.8.0;
+
+import "../interfaces/ISwapExecutor.sol";
+
+contract BalancerSwapExecutor is ISwapExecutor {
+    address private constant vaultAddress =
+        0xBA12222222228d8Ba445958a75a0704d566BF2C8;
+    bytes32 private constant swapSelector =
+        0x52bbbe2900000000000000000000000000000000000000000000000000000000;
+    bytes32 private constant maxUint256 =
+        0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF;
+
+    /**
+     * @dev Executes a Balancer swap.
+     * @param givenAmount how much of to swap, depending on exactOut either in-
+     * or outAmount.
+     * @param data the parameters of the swap. This data is roughly the packed
+     * encoding of
+     *     the struct below:
+     *  ```
+     *      struct Params {
+     *          // the token that the caller is selling
+     *          IERC20 tokenIn;
+     *
+     *          // the token that the caller is receiving in exchange
+     *          IERC20 tokenOut;
+     *
+     *          // the target pool id
+     *          bytes32 poolId;
+     *
+     *          // the receiver of `tokenOut`
+     *          address receiver;
+     *
+     *          // whether we want exactOut semantics
+     *          bool exactOut;
+     *
+     *          // whether we need to approve the pool to spend `tokenIn`
+     *          bool tokenApprovalNeeded;
+     *
+     *      }
+     *  ```
+     */
+    function swap(uint256 givenAmount, bytes calldata data)
+        external
+        payable
+        returns (uint256 calculatedAmount)
+    {
+        IERC20 tokenIn;
+        IERC20 tokenOut;
+        bytes32 poolId;
+        address receiver;
+        bool exactOut;
+        bool tokenApprovalNeeded;
+        assembly {
+            tokenIn := shr(96, calldataload(data.offset))
+            tokenOut := shr(96, calldataload(add(data.offset, 20)))
+            poolId := calldataload(add(data.offset, 40))
+            let dataLoad := calldataload(add(data.offset, 72))
+            receiver := shr(96, dataLoad)
+            exactOut := and(shr(88, dataLoad), 0xff)
+            tokenApprovalNeeded := and(shr(80, dataLoad), 0xff)
+
+            // Check if token approval is needed and perform the approval
+            if tokenApprovalNeeded {
+                // Prepare approve call
+                let approveCalldata := mload(0x40)
+                mstore(
+                    approveCalldata,
+                    0x095ea7b300000000000000000000000000000000000000000000000000000000
+                ) // approve selector
+                mstore(add(approveCalldata, 4), vaultAddress) // spender
+                mstore(add(approveCalldata, 36), maxUint256) // value
+                    // (maxUint256)
+
+                let success :=
+                    call(gas(), tokenIn, 0, approveCalldata, 68, 0, 0)
+                if iszero(success) {
+                    returndatacopy(0, 0, returndatasize())
+                    revert(0, returndatasize())
+                }
+            }
+
+            let ptr := mload(0x40)
+            mstore(ptr, swapSelector)
+            //limit: as it is always recalculated during the swap, we use the
+            // extremums 0 tokenOut or max(uint256) tokenIn.
+            let limit := 0
+            if exactOut { limit := maxUint256 }
+            // as the singleSwap struct contains a bytes, it's considered as
+            // dynamic.
+            // dynamic values are encoded at the end of the calldata and have a
+            // corresponding offset at the beginning
+            // we first need to encode the offset of the singleSwap struct
+            mstore(add(ptr, 4), 0xe0)
+            // fundManagement.sender: is always address(this)
+            mstore(add(ptr, 36), address())
+            // fundManagement.fromInternalBalance
+            mstore(add(ptr, 68), 0)
+            // fundManagement.receiver
+            mstore(add(ptr, 100), receiver)
+            // fundManagement.toInternalBalance
+            mstore(add(ptr, 132), 0)
+            // limit
+            mstore(add(ptr, 164), limit)
+            // deadline
+            mstore(add(ptr, 196), timestamp())
+            // singleSwap.poolId
+            mstore(add(ptr, 228), poolId)
+            // singleSwap.exactOut
+            mstore(add(ptr, 260), exactOut)
+            // singleSwap.assetIn
+            mstore(add(ptr, 292), tokenIn)
+            // singleSwap.assetOut
+            mstore(add(ptr, 324), tokenOut)
+            // singleSwap.amount
+            mstore(add(ptr, 356), givenAmount)
+            // singleSwap.userData offset
+            mstore(add(ptr, 388), 0xc0)
+            // singleSwap.userData lenght
+            mstore(add(ptr, 420), 0)
+
+            let success := call(gas(), vaultAddress, 0, ptr, 452, ptr, 32)
+            switch success
+            case 0 {
+                returndatacopy(0, 0, returndatasize())
+                revert(0, returndatasize())
+            }
+            default { calculatedAmount := mload(ptr) }
+        }
+    }
+}