feat: init simple vault spoke

src/dependencies/openzeppelin/ERC4626.sol

@@ -0,0 +1,301 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v5.4.0) (token/ERC20/extensions/ERC4626.sol)
+
+pragma solidity ^0.8.20;
+
+import {IERC20, IERC20Metadata, ERC20} from './ERC20.sol';
+import {SafeERC20} from './SafeERC20.sol';
+import {IERC4626} from './IERC4626.sol';
+import {Math} from './Math.sol';
+
+/**
+ * @dev Implementation of the ERC-4626 "Tokenized Vault Standard" as defined in
+ * https://eips.ethereum.org/EIPS/eip-4626[ERC-4626].
+ *
+ * This extension allows the minting and burning of "shares" (represented using the ERC-20 inheritance) in exchange for
+ * underlying "assets" through standardized {deposit}, {mint}, {redeem} and {burn} workflows. This contract extends
+ * the ERC-20 standard. Any additional extensions included along it would affect the "shares" token represented by this
+ * contract and not the "assets" token which is an independent contract.
+ *
+ * [CAUTION]
+ * ====
+ * In empty (or nearly empty) ERC-4626 vaults, deposits are at high risk of being stolen through frontrunning
+ * with a "donation" to the vault that inflates the price of a share. This is variously known as a donation or inflation
+ * attack and is essentially a problem of slippage. Vault deployers can protect against this attack by making an initial
+ * deposit of a non-trivial amount of the asset, such that price manipulation becomes infeasible. Withdrawals may
+ * similarly be affected by slippage. Users can protect against this attack as well as unexpected slippage in general by
+ * verifying the amount received is as expected, using a wrapper that performs these checks such as
+ * https://github.com/fei-protocol/ERC4626#erc4626router-and-base[ERC4626Router].
+ *
+ * Since v4.9, this implementation introduces configurable virtual assets and shares to help developers mitigate that risk.
+ * The `_decimalsOffset()` corresponds to an offset in the decimal representation between the underlying asset's decimals
+ * and the vault decimals. This offset also determines the rate of virtual shares to virtual assets in the vault, which
+ * itself determines the initial exchange rate. While not fully preventing the attack, analysis shows that the default
+ * offset (0) makes it non-profitable even if an attacker is able to capture value from multiple user deposits, as a result
+ * of the value being captured by the virtual shares (out of the attacker's donation) matching the attacker's expected gains.
+ * With a larger offset, the attack becomes orders of magnitude more expensive than it is profitable. More details about the
+ * underlying math can be found xref:ROOT:erc4626.adoc#inflation-attack[here].
+ *
+ * The drawback of this approach is that the virtual shares do capture (a very small) part of the value being accrued
+ * to the vault. Also, if the vault experiences losses, the users try to exit the vault, the virtual shares and assets
+ * will cause the first user to exit to experience reduced losses in detriment to the last users that will experience
+ * bigger losses. Developers willing to revert back to the pre-v4.9 behavior just need to override the
+ * `_convertToShares` and `_convertToAssets` functions.
+ *
+ * To learn more, check out our xref:ROOT:erc4626.adoc[ERC-4626 guide].
+ * ====
+ */
+abstract contract ERC4626 is ERC20, IERC4626 {
+  using Math for uint256;
+
+  IERC20 private immutable _asset;
+  uint8 private immutable _underlyingDecimals;
+
+  /**
+   * @dev Attempted to deposit more assets than the max amount for `receiver`.
+   */
+  error ERC4626ExceededMaxDeposit(address receiver, uint256 assets, uint256 max);
+
+  /**
+   * @dev Attempted to mint more shares than the max amount for `receiver`.
+   */
+  error ERC4626ExceededMaxMint(address receiver, uint256 shares, uint256 max);
+
+  /**
+   * @dev Attempted to withdraw more assets than the max amount for `receiver`.
+   */
+  error ERC4626ExceededMaxWithdraw(address owner, uint256 assets, uint256 max);
+
+  /**
+   * @dev Attempted to redeem more shares than the max amount for `receiver`.
+   */
+  error ERC4626ExceededMaxRedeem(address owner, uint256 shares, uint256 max);
+
+  /**
+   * @dev Set the underlying asset contract. This must be an ERC20-compatible contract (ERC-20 or ERC-777).
+   */
+  constructor(IERC20 asset_) {
+    (bool success, uint8 assetDecimals) = _tryGetAssetDecimals(asset_);
+    _underlyingDecimals = success ? assetDecimals : 18;
+    _asset = asset_;
+  }
+
+  /**
+   * @dev Attempts to fetch the asset decimals. A return value of false indicates that the attempt failed in some way.
+   */
+  function _tryGetAssetDecimals(IERC20 asset_) private view returns (bool ok, uint8 assetDecimals) {
+    (bool success, bytes memory encodedDecimals) = address(asset_).staticcall(
+      abi.encodeCall(IERC20Metadata.decimals, ())
+    );
+    if (success && encodedDecimals.length >= 32) {
+      uint256 returnedDecimals = abi.decode(encodedDecimals, (uint256));
+      if (returnedDecimals <= type(uint8).max) {
+        return (true, uint8(returnedDecimals));
+      }
+    }
+    return (false, 0);
+  }
+
+  /**
+   * @dev Decimals are computed by adding the decimal offset on top of the underlying asset's decimals. This
+   * "original" value is cached during construction of the vault contract. If this read operation fails (e.g., the
+   * asset has not been created yet), a default of 18 is used to represent the underlying asset's decimals.
+   *
+   * See {IERC20Metadata-decimals}.
+   */
+  function decimals() public view virtual override(IERC20Metadata, ERC20) returns (uint8) {
+    return _underlyingDecimals + _decimalsOffset();
+  }
+
+  /// @inheritdoc IERC4626
+  function asset() public view virtual returns (address) {
+    return address(_asset);
+  }
+
+  /// @inheritdoc IERC4626
+  function totalAssets() public view virtual returns (uint256) {
+    return IERC20(asset()).balanceOf(address(this));
+  }
+
+  /// @inheritdoc IERC4626
+  function convertToShares(uint256 assets) public view virtual returns (uint256) {
+    return _convertToShares(assets, Math.Rounding.Floor);
+  }
+
+  /// @inheritdoc IERC4626
+  function convertToAssets(uint256 shares) public view virtual returns (uint256) {
+    return _convertToAssets(shares, Math.Rounding.Floor);
+  }
+
+  /// @inheritdoc IERC4626
+  function maxDeposit(address) public view virtual returns (uint256) {
+    return type(uint256).max;
+  }
+
+  /// @inheritdoc IERC4626
+  function maxMint(address) public view virtual returns (uint256) {
+    return type(uint256).max;
+  }
+
+  /// @inheritdoc IERC4626
+  function maxWithdraw(address owner) public view virtual returns (uint256) {
+    return _convertToAssets(balanceOf(owner), Math.Rounding.Floor);
+  }
+
+  /// @inheritdoc IERC4626
+  function maxRedeem(address owner) public view virtual returns (uint256) {
+    return balanceOf(owner);
+  }
+
+  /// @inheritdoc IERC4626
+  function previewDeposit(uint256 assets) public view virtual returns (uint256) {
+    return _convertToShares(assets, Math.Rounding.Floor);
+  }
+
+  /// @inheritdoc IERC4626
+  function previewMint(uint256 shares) public view virtual returns (uint256) {
+    return _convertToAssets(shares, Math.Rounding.Ceil);
+  }
+
+  /// @inheritdoc IERC4626
+  function previewWithdraw(uint256 assets) public view virtual returns (uint256) {
+    return _convertToShares(assets, Math.Rounding.Ceil);
+  }
+
+  /// @inheritdoc IERC4626
+  function previewRedeem(uint256 shares) public view virtual returns (uint256) {
+    return _convertToAssets(shares, Math.Rounding.Floor);
+  }
+
+  /// @inheritdoc IERC4626
+  function deposit(uint256 assets, address receiver) public virtual returns (uint256) {
+    uint256 maxAssets = maxDeposit(receiver);
+    if (assets > maxAssets) {
+      revert ERC4626ExceededMaxDeposit(receiver, assets, maxAssets);
+    }
+
+    uint256 shares = previewDeposit(assets);
+    _deposit(_msgSender(), receiver, assets, shares);
+
+    return shares;
+  }
+
+  /// @inheritdoc IERC4626
+  function mint(uint256 shares, address receiver) public virtual returns (uint256) {
+    uint256 maxShares = maxMint(receiver);
+    if (shares > maxShares) {
+      revert ERC4626ExceededMaxMint(receiver, shares, maxShares);
+    }
+
+    uint256 assets = previewMint(shares);
+    _deposit(_msgSender(), receiver, assets, shares);
+
+    return assets;
+  }
+
+  /// @inheritdoc IERC4626
+  function withdraw(
+    uint256 assets,
+    address receiver,
+    address owner
+  ) public virtual returns (uint256) {
+    uint256 maxAssets = maxWithdraw(owner);
+    if (assets > maxAssets) {
+      revert ERC4626ExceededMaxWithdraw(owner, assets, maxAssets);
+    }
+
+    uint256 shares = previewWithdraw(assets);
+    _withdraw(_msgSender(), receiver, owner, assets, shares);
+
+    return shares;
+  }
+
+  /// @inheritdoc IERC4626
+  function redeem(
+    uint256 shares,
+    address receiver,
+    address owner
+  ) public virtual returns (uint256) {
+    uint256 maxShares = maxRedeem(owner);
+    if (shares > maxShares) {
+      revert ERC4626ExceededMaxRedeem(owner, shares, maxShares);
+    }
+
+    uint256 assets = previewRedeem(shares);
+    _withdraw(_msgSender(), receiver, owner, assets, shares);
+
+    return assets;
+  }
+
+  /**
+   * @dev Internal conversion function (from assets to shares) with support for rounding direction.
+   */
+  function _convertToShares(
+    uint256 assets,
+    Math.Rounding rounding
+  ) internal view virtual returns (uint256) {
+    return assets.mulDiv(totalSupply() + 10 ** _decimalsOffset(), totalAssets() + 1, rounding);
+  }
+
+  /**
+   * @dev Internal conversion function (from shares to assets) with support for rounding direction.
+   */
+  function _convertToAssets(
+    uint256 shares,
+    Math.Rounding rounding
+  ) internal view virtual returns (uint256) {
+    return shares.mulDiv(totalAssets() + 1, totalSupply() + 10 ** _decimalsOffset(), rounding);
+  }
+
+  /**
+   * @dev Deposit/mint common workflow.
+   */
+  function _deposit(
+    address caller,
+    address receiver,
+    uint256 assets,
+    uint256 shares
+  ) internal virtual {
+    // If asset() is ERC-777, `transferFrom` can trigger a reentrancy BEFORE the transfer happens through the
+    // `tokensToSend` hook. On the other hand, the `tokenReceived` hook, that is triggered after the transfer,
+    // calls the vault, which is assumed not malicious.
+    //
+    // Conclusion: we need to do the transfer before we mint so that any reentrancy would happen before the
+    // assets are transferred and before the shares are minted, which is a valid state.
+    // slither-disable-next-line reentrancy-no-eth
+    SafeERC20.safeTransferFrom(IERC20(asset()), caller, address(this), assets);
+    _mint(receiver, shares);
+
+    emit Deposit(caller, receiver, assets, shares);
+  }
+
+  /**
+   * @dev Withdraw/redeem common workflow.
+   */
+  function _withdraw(
+    address caller,
+    address receiver,
+    address owner,
+    uint256 assets,
+    uint256 shares
+  ) internal virtual {
+    if (caller != owner) {
+      _spendAllowance(owner, caller, shares);
+    }
+
+    // If asset() is ERC-777, `transfer` can trigger a reentrancy AFTER the transfer happens through the
+    // `tokensReceived` hook. On the other hand, the `tokensToSend` hook, that is triggered before the transfer,
+    // calls the vault, which is assumed not malicious.
+    //
+    // Conclusion: we need to do the transfer after the burn so that any reentrancy would happen after the
+    // shares are burned and after the assets are transferred, which is a valid state.
+    _burn(owner, shares);
+    SafeERC20.safeTransfer(IERC20(asset()), receiver, assets);
+
+    emit Withdraw(caller, receiver, owner, assets, shares);
+  }
+
+  function _decimalsOffset() internal view virtual returns (uint8) {
+    return 0;
+  }
+}