feat: EncryptedWETH

contracts/token/ERC20/EncryptedWETH.sol

@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: BSD-3-Clause-Clear
+pragma solidity ^0.8.24;
+
+import { EncryptedERC20 } from "./EncryptedERC20.sol";
+
+import "fhevm/lib/TFHE.sol";
+
+/**
+ * @title             EncryptedWETH
+ * @notice            This contract allows users to wrap/unwrap trustlessly
+ *                    ETH (or other native tokens) to EncryptedERC20 tokens.
+ */
+abstract contract EncryptedWETH is EncryptedERC20 {
+    /// @notice Returned if the amount is greater than 2**64.
+    error AmountTooHigh();
+
+    /// @notice Returned if ETH transfer fails.
+    error ETHTransferFail();
+
+    /// @notice Emitted when encrypted wrapped ether is unwrapped.
+    event Unwrap(address indexed to, uint64 amount);
+
+    /// @notice Emitted when ether is wrapped.
+    event Wrap(address indexed to, uint64 amount);
+
+    /**
+     * @notice         Deposit/withdraw ethers (or native tokens).
+     * @dev            The name/symbol are autogenerated.
+     */
+    constructor()
+        EncryptedERC20(string(abi.encodePacked("Encrypted Wrapped Ether")), string(abi.encodePacked("eWETH")))
+    {}
+
+    /**
+     * @notice         Unwrap EncryptedERC20 tokens to ether.
+     * @param amount   Amount to unwrap.
+     */
+    function unwrap(uint64 amount) public virtual {
+        _balances[msg.sender] = TFHE.sub(_balances[msg.sender], amount);
+        TFHE.allowThis(_balances[msg.sender]);
+        TFHE.allow(_balances[msg.sender], msg.sender);
+
+        _totalSupply -= amount;
+
+        /// @dev It does a supply adjustment.
+        uint256 amountUint256 = amount * (10 ** (18 - decimals()));
+
+        /* solhint-disable avoid-call-value*/
+        /* solhint-disable avoid-low-level-calls*/
+        (bool callSuccess, ) = msg.sender.call{ value: amountUint256 }("");
+
+        if (!callSuccess) {
+            revert ETHTransferFail();
+        }
+
+        emit Unwrap(msg.sender, amount);
+    }
+
+    /**
+     * @notice         Wrap ether to an encrypted format.
+     */
+    function wrap() public payable virtual {
+        if (msg.value > type(uint64).max) {
+            revert AmountTooHigh();
+        }
+
+        uint64 amountUint64 = uint64(msg.value / (10 ** (18 - decimals())));
+        _balances[msg.sender] = TFHE.add(_balances[msg.sender], amountUint64);
+
+        TFHE.allowThis(_balances[msg.sender]);
+        TFHE.allow(_balances[msg.sender], msg.sender);
+
+        _totalSupply += amountUint64;
+
+        emit Wrap(msg.sender, amountUint64);
+    }
+}