feat: add wrapper

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This repository contains **Euler-CoW Protocol integration contracts** that enable leveraged position management (opening/closing) through CoW Protocol settlements combined with Ethereum Vault Connector (EVC) operations. The contracts act as "wrappers" that coordinate complex multi-step DeFi operations atomically.
+
+### Core Architecture
+
+**Wrapper Pattern**: The codebase uses a chaining wrapper pattern where solvers can execute wrapped settlements that perform custom logic before/during/after CoW Protocol settlements.
+
+- `CowWrapper.sol`: Base abstract contract providing the wrapper framework
+  - Validates callers are authenticated solvers
+  - Implements `wrappedSettle()` entry point
+  - Provides `_internalSettle()` for continuing the settlement chain
+  - Wrappers can be chained: Wrapper1 → Wrapper2 → Settlement
+
+- `CowWrapperHelpers.sol`: Helper utilities for wrapper data parsing and validation
+- The CowWrapper is designed to support reentrancy. Additionally, the CowWrapper is designed with gas efficiency in mind, so we only check if the previous contract was part of the trusted wrapper chain. Furthermore, any wrappers that will ever be approved exist will use `CowWrapper.sol` as a base, so its not possible to inject a unauthorized wrapper into the chain without it getting ultimately rejected by the time the settlement contract is reached.
+
+**Specialized Wrappers**: Two production wrappers implement specific EVC + CoW Protocol workflows:
+
+1. **`CowEvcOpenPositionWrapper.sol`**: Opens leveraged positions
+   - Enables collateral vault
+   - Enables controller (borrow vault)
+   - Deposits collateral
+   - Borrows assets
+   - Executes CoW settlement to swap borrowed assets → collateral
+   - All operations are atomic within EVC batch
+
+2. **`CowEvcClosePositionWrapper.sol`**: Closes leveraged positions
+   - Executes CoW settlement to swap collateral → repayment assets
+   - Repays debt to borrow vault
+   - Returns excess assets to user
+   - Disables collateral if full repayment
+   - All operations are atomic within EVC batch
+
+**Authorization Mechanisms**: Both wrappers support two authorization modes:
+- **EVC Permit**: One-time permit signature for specific operation
+- **Pre-Approved Hashes** (`PreApprovedHashes.sol`): Users pre-approve operation hashes on-chain (useful for EIP-7702 wallet interactions)
+
+### Key Dependencies
+
+- **Euler Vault Kit** (`lib/euler-vault-kit`): ERC4626 vault implementation with borrowing
+- **Ethereum Vault Connector (EVC)** (`lib/evc`): Batch transaction coordinator with account checking
+- **CoW Protocol** (`lib/cow`): DEX aggregator settlement contracts and order libraries
+
+## Development Commands
+
+### Build
+```bash
+forge build
+```
+
+### Test
+```bash
+# Run all tests (requires FORK_RPC_URL environment variable)
+forge test
+
+# Run specific test file
+forge test --match-path test/CowEvcOpenPositionWrapper.t.sol
+
+# Run specific test function
+forge test --match-test test_OpenPosition
+
+# Run with verbose output
+forge test -vvv
+```
+
+**Important**: Tests require mainnet fork. Set `FORK_RPC_URL` environment variable to a mainnet RPC endpoint.
+
+### Format
+```bash
+forge fmt
+```
+
+### Gas Snapshots
+```bash
+forge snapshot
+```
+
+## Testing Architecture
+
+**Base Test Contract**: `test/helpers/CowBaseTest.sol`
+- Sets up mainnet fork at block 22546006
+- Configures CoW Protocol settlement and authenticator
+- Deploys test solver contract
+- Sets up test vaults (eSUSDS, eWETH) and tokens
+- Provides helper functions for creating settlement data structures
+
+**Test Helpers**:
+- `MilkSwap.sol`: Simple test DEX for simulating swaps in settlements
+- `GPv2OrderHelper.sol`: Utilities for constructing CoW Protocol orders
+- `SignerECDSA.sol`: ECDSA signature utilities for tests
+- `EmptyWrapper.sol`: Minimal wrapper for testing wrapper chaining
+
+## Important Implementation Details
+
+### Wrapper Data Format
+Wrapper data is passed as a calldata slice with format:
+```
+[wrapper-specific-params][signature][next-wrapper-address (20 bytes)][remaining-wrapper-data]
+```
+
+The `parseWrapperData()` function must consume its portion and return the remainder.
+
+### EVC Integration
+Both wrappers execute operations within EVC batches to ensure atomicity and proper account health checks. The flow is:
+1. Wrapper validates authorization (permit or pre-approved hash)
+2. Build EVC.BatchItem[] array with all operations
+3. Call `EVC.batch()` - EVC ensures account is healthy at end
+
+### Settlement Execution Context
+- Wrappers use `evcInternalSettle()` as internal callback from EVC batch
+- This function can only be called by EVC during batch execution
+- Uses transient storage (`depth`, `settleCalls`) to prevent reentrancy
+
+### Authentication
+- Only authenticated CoW Protocol solvers can call `wrappedSettle()`
+- Authentication checked via `AUTHENTICATOR.isSolver(msg.sender)`
+- Wrappers themselves can be added to solver allowlist for testing
+
+## Foundry Configuration
+
+- Compiler optimization: enabled
+- IR compilation: enabled (`via_ir = true`)
+- Source directory: `src/`
+- Test directory: `test/`
+- Library dependencies managed via git submodules
+
+## Coding Style
+
+### Error Handling
+**Always use `require()` with custom errors instead of `if () { revert }`**. This pattern is used consistently throughout the codebase:
+
+```solidity
+// ✅ Preferred
+require(msg.sender == address(EVC), Unauthorized(msg.sender));
+require(depth > 0 && settleCalls == 0, Unauthorized(address(0)));
+
+// ❌ Avoid
+if (msg.sender != address(EVC)) {
+    revert Unauthorized(msg.sender);
+}
+```
+
+This approach is more concise and maintains consistency with the existing codebase style.
+
+## Remappings
+
+Key import remappings:
+- `cow/` → CoW Protocol contracts (`lib/cow/src/contracts`)
+- `evc/` → Ethereum Vault Connector (`lib/euler-vault-kit/lib/ethereum-vault-connector/src/`)
+- `euler-vault-kit/` → Euler vault implementation
+- `openzeppelin/` → OpenZeppelin contracts (via EVC dependency)
+
+
+## When Giving PR feedback
+* do not re-suggest or address feedback after it has already been given, either by you or other contributors who have commented.
+* be careful not to use too many inline comments. If there are already inline comments on the same line that you want to comment on, or if the inline comment is about something that has already been suggested, don't comment.

src/CowWrapper.sol

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+// SPDX-License-Identifier: MIT OR Apache-2.0
+pragma solidity >=0.7.6 <0.9.0;
+pragma abicoder v2;
+
+/**
+ * @title CoW Wrapper all-in-one integration file
+ * @author CoW Protocol Developers
+ * @notice This file is completely self-contained (ie no dependencies) and can be portably copied to whatever projects it is needed.
+ * It contains:
+ * * CowWrapper -- an abstract base contract which should be inherited by all wrappers
+ * * ICowWrapper -- the required interface for all wrappers
+ * * ICowSettlement -- A minimized interface and base structures for CoW Protocol settlement contract. From https://github.com/cowprotocol/contracts/blob/main/src/contracts/GPv2Settlement.sol
+ * * ICowAuthentication -- The authentication interface used by ICowSettlement. From https://github.com/cowprotocol/contracts/blob/main/src/contracts/interfaces/GPv2Authentication.sol
+ */
+
+/// @title CoW Protocol Authentication Interface
+/// @author CoW DAO developers
+interface ICowAuthentication {
+    /// @dev determines whether the provided address is an authenticated solver.
+    /// @param prospectiveSolver the address of prospective solver.
+    /// @return true when prospectiveSolver is an authenticated solver, otherwise false.
+    function isSolver(address prospectiveSolver) external view returns (bool);
+}
+
+/// @title CoW Protocol Settlement Interface
+/// @notice Minimal interface for CoW Protocol's settlement contract
+/// @dev Used for type-safe calls to the settlement contract's settle function
+interface ICowSettlement {
+    /// @notice Trade data structure matching GPv2Settlement
+    struct Trade {
+        uint256 sellTokenIndex;
+        uint256 buyTokenIndex;
+        address receiver;
+        uint256 sellAmount;
+        uint256 buyAmount;
+        uint32 validTo;
+        bytes32 appData;
+        uint256 feeAmount;
+        uint256 flags;
+        uint256 executedAmount;
+        bytes signature;
+    }
+
+    /// @notice Interaction data structure for pre/intra/post-settlement hooks
+    struct Interaction {
+        address target;
+        uint256 value;
+        bytes callData;
+    }
+
+    /// @notice Returns the authentication contract used by the settlement contract.
+    function authenticator() external returns (ICowAuthentication);
+
+    /// @notice Settles a batch of trades atomically
+    /// @param tokens Array of token addresses involved in the settlement
+    /// @param clearingPrices Array of clearing prices for each token
+    /// @param trades Array of trades to execute
+    /// @param interactions Array of three interaction arrays (pre, intra, post-settlement)
+    function settle(
+        address[] calldata tokens,
+        uint256[] calldata clearingPrices,
+        Trade[] calldata trades,
+        Interaction[][3] calldata interactions
+    ) external;
+}
+
+/// @title CoW Protocol Wrapper Interface
+/// @notice Interface for wrapper contracts that add custom logic around CoW settlements
+/// @dev Wrappers can be chained together to compose multiple settlement operations
+interface ICowWrapper {
+    /// @notice A human readable label for this wrapper. Used for display in explorer/analysis UIs
+    function name() external view returns (string memory);
+
+    /// @notice Initiates a wrapped settlement call
+    /// @dev This is the entry point for wrapped settlements. The wrapper will execute custom logic
+    ///      before calling the next wrapper or settlement contract in the chain.
+    /// @param settleData ABI-encoded call to ICowSettlement.settle()
+    /// @param wrapperData Encoded chain of wrapper-specific data followed by addresses of next wrappers/settlement
+    function wrappedSettle(bytes calldata settleData, bytes calldata wrapperData) external;
+}
+
+/// @title CoW Protocol Wrapper Base Contract
+/// @notice Abstract base contract for creating wrapper contracts around CoW Protocol settlements
+/// @dev A wrapper enables custom pre/post-settlement and context-setting logic and can be chained with other wrappers.
+///      Wrappers must:
+///      - Be approved by the ICowAuthentication contract
+///      - Verify the caller is an authenticated solver
+///      - Eventually call settle() on the approved ICowSettlement contract
+///      - Implement _wrap() for custom logic
+///      - Implement parseWrapperData() for validation of implementation-specific wrapperData
+abstract contract CowWrapper is ICowWrapper {
+    /// @notice Thrown when the caller is not an authenticated solver
+    /// @param unauthorized The address that attempted to call wrappedSettle
+    error NotASolver(address unauthorized);
+
+    /// @notice Thrown when settle data doesn't contain the correct function selector
+    /// @param invalidSettleData The invalid settle data that was provided
+    error InvalidSettleData(bytes invalidSettleData);
+
+    /// @notice The settlement contract
+    ICowSettlement public immutable SETTLEMENT;
+
+    /// @notice The authentication contract used to verify solvers
+    /// @dev This is derived from `SETTLEMENT.authenticator()`.
+    ICowAuthentication public immutable AUTHENTICATOR;
+
+    /// @notice Constructs a new CowWrapper
+    /// @param settlement_ The ICowSettlement contract to use at the end of the wrapper chain. Also used for wrapper authentication.
+    constructor(ICowSettlement settlement_) {
+        SETTLEMENT = settlement_;
+        AUTHENTICATOR = settlement_.authenticator();
+    }
+
+    /// @notice Initiates a wrapped settlement call
+    /// @dev Entry point for solvers to execute wrapped settlements. Verifies the caller is a solver,
+    ///      validates wrapper data, then delegates to _wrap() for custom logic.
+    /// @param settleData ABI-encoded call to ICowSettlement.settle() containing trade data
+    /// @param wrapperData Encoded data for this wrapper and the chain of next wrappers/settlement.
+    ///                    Format: [2-byte len][wrapper-specific-data][next-address]([2-byte len][wrapper-specific-data][next-address]...)
+    function wrappedSettle(bytes calldata settleData, bytes calldata wrapperData) external {
+        // Revert if not a valid solver
+        require(AUTHENTICATOR.isSolver(msg.sender), NotASolver(msg.sender));
+
+        // Find out how long the next wrapper data is supposed to be
+        // We use 2 bytes to decode the length of the wrapper data because it allows for up to 64KB of data for each wrapper.
+        // This should be plenty of length for all identified use-cases of wrappers in the forseeable future.
+        uint16 nextWrapperDataLen = uint16(bytes2(wrapperData[0:2]));
+
+        // Delegate to the wrapper's custom logic
+        _wrap(settleData, wrapperData[2:2 + nextWrapperDataLen], wrapperData[2 + nextWrapperDataLen:]);
+    }
+
+    /// @notice Internal function containing the wrapper's custom logic
+    /// @dev Must be implemented by concrete wrapper contracts. Should execute custom logic
+    ///      then eventually call _internalSettle() to continue the settlement chain.
+    /// @param settleData ABI-encoded call to ICowSettlement.settle()
+    /// @param wrapperData The wrapper data which should be consumed by this wrapper
+    /// @param remainingWrapperData Additional wrapper data needed by future wrappers. This should be passed unaltered to _internalSettle
+    function _wrap(bytes calldata settleData, bytes calldata wrapperData, bytes calldata remainingWrapperData)
+        internal
+        virtual;
+
+    /// @notice Continues the settlement chain by calling the next wrapper or settlement contract
+    /// @dev Extracts the next target address from wrapperData and either:
+    ///      - Calls ICowSettlement.settle() directly if no more wrappers remain, or
+    ///      - Calls the next CowWrapper.wrappedSettle() to continue the chain
+    /// @param settleData ABI-encoded call to ICowSettlement.settle()
+    /// @param remainingWrapperData Remaining wrapper data starting with the next target address (20 bytes)
+    function _internalSettle(bytes calldata settleData, bytes calldata remainingWrapperData) internal {
+        if (remainingWrapperData.length == 0) {
+            // No more wrapper data - we're calling the final settlement contract
+            // Verify the settle data has the correct function selector
+            require(bytes4(settleData[:4]) == ICowSettlement.settle.selector, InvalidSettleData(settleData));
+
+            // Call the settlement contract directly with the settle data
+            (bool success, bytes memory returnData) = address(SETTLEMENT).call(settleData);
+
+            if (!success) {
+                // Bubble up the revert reason from the settlement contract
+                assembly ("memory-safe") {
+                    revert(add(returnData, 0x20), mload(returnData))
+                }
+            }
+        } else {
+            // Extract the next wrapper address from the first 20 bytes of wrapperData
+            address nextWrapper = address(bytes20(remainingWrapperData[:20]));
+
+            // Skip past the address we just read
+            remainingWrapperData = remainingWrapperData[20:];
+
+            // More wrapper data remains - call the next wrapper in the chain
+            CowWrapper(nextWrapper).wrappedSettle(settleData, remainingWrapperData);
+        }
+    }
+}