feat: Sonic fragment

contracts/partners/tokenWrappers/SonicFragment.sol

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-3.0
+
+pragma solidity ^0.8.17;
+
+import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+import { IERC20 } from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
+
+import { IAccessControlManager } from "../../interfaces/IAccessControlManager.sol";
+import { Errors } from "../../utils/Errors.sol";
+
+/// @title SonicFragment
+/// @notice Contract for Sonic fragments which can be converted upon activation into S tokens
+/// @author Angle Labs, Inc.
+contract SonicFragment is ERC20 {
+    using SafeERC20 for IERC20;
+
+    /// @notice Contract handling access control
+    IAccessControlManager public immutable accessControlManager;
+    /// @notice Address for the S token
+    address public immutable sToken;
+
+    /// @notice Amount of S tokens sent on the contract at the activation of redemption
+    /// @dev Used to compute the exchange rate between fragments and S tokens
+    uint128 public sTokenAmount;
+    /// @notice Total supply of the contract
+    /// @dev Needs to be stored to compute the exchange rate between fragments and sTokens
+    uint120 public supply;
+    /// @notice Whether redemption for S tokens has been activated or not
+    uint8 public contractSettled;
+
+    constructor(
+        address _accessControlManager,
+        address recipient,
+        address _sToken,
+        uint256 _totalSupply,
+        string memory _name,
+        string memory _symbol
+    ) ERC20(_name, _symbol) {
+        // Zero address check
+        if (_sToken == address(0)) revert Errors.ZeroAddress();
+        IAccessControlManager(_accessControlManager).isGovernor(msg.sender);
+        sToken = _sToken;
+        accessControlManager = IAccessControlManager(_accessControlManager);
+        supply = uint120(_totalSupply);
+        _mint(recipient, _totalSupply);
+    }
+
+    // ================================= MODIFIERS =================================
+
+    /// @notice Checks whether the `msg.sender` has the governor role
+    modifier onlyGovernor() {
+        if (!accessControlManager.isGovernor(msg.sender)) revert Errors.NotAllowed();
+        _;
+    }
+
+    /// @notice Activates the contract settlement and enables redemption of fragments into S
+    /// @dev Can only be called once
+    function settleContract(uint256 _sTokenAmount) external onlyGovernor {
+        if (contractSettled > 0) revert Errors.NotAllowed();
+        contractSettled = 1;
+        IERC20(sToken).safeTransferFrom(msg.sender, address(this), sTokenAmount);
+        sTokenAmount = uint128(_sTokenAmount);
+    }
+
+    /// @notice Recovers leftover tokens after sometime
+    function recover(uint256 amount, address recipient) external onlyGovernor {
+        IERC20(sToken).safeTransfer(recipient, amount);
+        sTokenAmount = 0;
+    }
+
+    /// @notice Redeems fragments against S based on a predefined exchange rate
+    function redeem(uint256 amount, address recipient) external returns (uint256 amountToSend) {
+        uint128 _sTokenAmount = sTokenAmount;
+        if (_sTokenAmount == 0) revert Errors.NotAllowed();
+        _burn(msg.sender, amount);
+        amountToSend = (amount * _sTokenAmount) / supply;
+        IERC20(sToken).safeTransfer(recipient, amountToSend);
+    }
+}