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Contract Source Code:

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }

        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);

        _afterTokenTransfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Address.sol)

pragma solidity ^0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/math/SafeCast.sol)

pragma solidity ^0.8.0;

/**
 * @dev Wrappers over Solidity's uintXX/intXX casting operators with added overflow
 * checks.
 *
 * Downcasting from uint256/int256 in Solidity does not revert on overflow. This can
 * easily result in undesired exploitation or bugs, since developers usually
 * assume that overflows raise errors. `SafeCast` restores this intuition by
 * reverting the transaction when such an operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 *
 * Can be combined with {SafeMath} and {SignedSafeMath} to extend it to smaller types, by performing
 * all math on `uint256` and `int256` and then downcasting.
 */
library SafeCast {
    /**
     * @dev Returns the downcasted uint224 from uint256, reverting on
     * overflow (when the input is greater than largest uint224).
     *
     * Counterpart to Solidity's `uint224` operator.
     *
     * Requirements:
     *
     * - input must fit into 224 bits
     */
    function toUint224(uint256 value) internal pure returns (uint224) {
        require(value <= type(uint224).max, "SafeCast: value doesn't fit in 224 bits");
        return uint224(value);
    }

    /**
     * @dev Returns the downcasted uint128 from uint256, reverting on
     * overflow (when the input is greater than largest uint128).
     *
     * Counterpart to Solidity's `uint128` operator.
     *
     * Requirements:
     *
     * - input must fit into 128 bits
     */
    function toUint128(uint256 value) internal pure returns (uint128) {
        require(value <= type(uint128).max, "SafeCast: value doesn't fit in 128 bits");
        return uint128(value);
    }

    /**
     * @dev Returns the downcasted uint96 from uint256, reverting on
     * overflow (when the input is greater than largest uint96).
     *
     * Counterpart to Solidity's `uint96` operator.
     *
     * Requirements:
     *
     * - input must fit into 96 bits
     */
    function toUint96(uint256 value) internal pure returns (uint96) {
        require(value <= type(uint96).max, "SafeCast: value doesn't fit in 96 bits");
        return uint96(value);
    }

    /**
     * @dev Returns the downcasted uint64 from uint256, reverting on
     * overflow (when the input is greater than largest uint64).
     *
     * Counterpart to Solidity's `uint64` operator.
     *
     * Requirements:
     *
     * - input must fit into 64 bits
     */
    function toUint64(uint256 value) internal pure returns (uint64) {
        require(value <= type(uint64).max, "SafeCast: value doesn't fit in 64 bits");
        return uint64(value);
    }

    /**
     * @dev Returns the downcasted uint32 from uint256, reverting on
     * overflow (when the input is greater than largest uint32).
     *
     * Counterpart to Solidity's `uint32` operator.
     *
     * Requirements:
     *
     * - input must fit into 32 bits
     */
    function toUint32(uint256 value) internal pure returns (uint32) {
        require(value <= type(uint32).max, "SafeCast: value doesn't fit in 32 bits");
        return uint32(value);
    }

    /**
     * @dev Returns the downcasted uint16 from uint256, reverting on
     * overflow (when the input is greater than largest uint16).
     *
     * Counterpart to Solidity's `uint16` operator.
     *
     * Requirements:
     *
     * - input must fit into 16 bits
     */
    function toUint16(uint256 value) internal pure returns (uint16) {
        require(value <= type(uint16).max, "SafeCast: value doesn't fit in 16 bits");
        return uint16(value);
    }

    /**
     * @dev Returns the downcasted uint8 from uint256, reverting on
     * overflow (when the input is greater than largest uint8).
     *
     * Counterpart to Solidity's `uint8` operator.
     *
     * Requirements:
     *
     * - input must fit into 8 bits.
     */
    function toUint8(uint256 value) internal pure returns (uint8) {
        require(value <= type(uint8).max, "SafeCast: value doesn't fit in 8 bits");
        return uint8(value);
    }

    /**
     * @dev Converts a signed int256 into an unsigned uint256.
     *
     * Requirements:
     *
     * - input must be greater than or equal to 0.
     */
    function toUint256(int256 value) internal pure returns (uint256) {
        require(value >= 0, "SafeCast: value must be positive");
        return uint256(value);
    }

    /**
     * @dev Returns the downcasted int128 from int256, reverting on
     * overflow (when the input is less than smallest int128 or
     * greater than largest int128).
     *
     * Counterpart to Solidity's `int128` operator.
     *
     * Requirements:
     *
     * - input must fit into 128 bits
     *
     * _Available since v3.1._
     */
    function toInt128(int256 value) internal pure returns (int128) {
        require(value >= type(int128).min && value <= type(int128).max, "SafeCast: value doesn't fit in 128 bits");
        return int128(value);
    }

    /**
     * @dev Returns the downcasted int64 from int256, reverting on
     * overflow (when the input is less than smallest int64 or
     * greater than largest int64).
     *
     * Counterpart to Solidity's `int64` operator.
     *
     * Requirements:
     *
     * - input must fit into 64 bits
     *
     * _Available since v3.1._
     */
    function toInt64(int256 value) internal pure returns (int64) {
        require(value >= type(int64).min && value <= type(int64).max, "SafeCast: value doesn't fit in 64 bits");
        return int64(value);
    }

    /**
     * @dev Returns the downcasted int32 from int256, reverting on
     * overflow (when the input is less than smallest int32 or
     * greater than largest int32).
     *
     * Counterpart to Solidity's `int32` operator.
     *
     * Requirements:
     *
     * - input must fit into 32 bits
     *
     * _Available since v3.1._
     */
    function toInt32(int256 value) internal pure returns (int32) {
        require(value >= type(int32).min && value <= type(int32).max, "SafeCast: value doesn't fit in 32 bits");
        return int32(value);
    }

    /**
     * @dev Returns the downcasted int16 from int256, reverting on
     * overflow (when the input is less than smallest int16 or
     * greater than largest int16).
     *
     * Counterpart to Solidity's `int16` operator.
     *
     * Requirements:
     *
     * - input must fit into 16 bits
     *
     * _Available since v3.1._
     */
    function toInt16(int256 value) internal pure returns (int16) {
        require(value >= type(int16).min && value <= type(int16).max, "SafeCast: value doesn't fit in 16 bits");
        return int16(value);
    }

    /**
     * @dev Returns the downcasted int8 from int256, reverting on
     * overflow (when the input is less than smallest int8 or
     * greater than largest int8).
     *
     * Counterpart to Solidity's `int8` operator.
     *
     * Requirements:
     *
     * - input must fit into 8 bits.
     *
     * _Available since v3.1._
     */
    function toInt8(int256 value) internal pure returns (int8) {
        require(value >= type(int8).min && value <= type(int8).max, "SafeCast: value doesn't fit in 8 bits");
        return int8(value);
    }

    /**
     * @dev Converts an unsigned uint256 into a signed int256.
     *
     * Requirements:
     *
     * - input must be less than or equal to maxInt256.
     */
    function toInt256(uint256 value) internal pure returns (int256) {
        // Note: Unsafe cast below is okay because `type(int256).max` is guaranteed to be positive
        require(value <= uint256(type(int256).max), "SafeCast: value doesn't fit in an int256");
        return int256(value);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

/**
 * @title Base for contracts that are managed by the Origin Protocol's Governor.
 * @dev Copy of the openzeppelin Ownable.sol contract with nomenclature change
 *      from owner to governor and renounce methods removed. Does not use
 *      Context.sol like Ownable.sol does for simplification.
 * @author Origin Protocol Inc
 */
contract Governable {
    // Storage position of the owner and pendingOwner of the contract
    // keccak256("OUSD.governor");
    bytes32 private constant governorPosition =
        0x7bea13895fa79d2831e0a9e28edede30099005a50d652d8957cf8a607ee6ca4a;

    // keccak256("OUSD.pending.governor");
    bytes32 private constant pendingGovernorPosition =
        0x44c4d30b2eaad5130ad70c3ba6972730566f3e6359ab83e800d905c61b1c51db;

    // keccak256("OUSD.reentry.status");
    bytes32 private constant reentryStatusPosition =
        0x53bf423e48ed90e97d02ab0ebab13b2a235a6bfbe9c321847d5c175333ac4535;

    // See OpenZeppelin ReentrancyGuard implementation
    uint256 constant _NOT_ENTERED = 1;
    uint256 constant _ENTERED = 2;

    event PendingGovernorshipTransfer(
        address indexed previousGovernor,
        address indexed newGovernor
    );

    event GovernorshipTransferred(
        address indexed previousGovernor,
        address indexed newGovernor
    );

    /**
     * @dev Initializes the contract setting the deployer as the initial Governor.
     */
    constructor() {
        _setGovernor(msg.sender);
        emit GovernorshipTransferred(address(0), _governor());
    }

    /**
     * @notice Returns the address of the current Governor.
     */
    function governor() public view returns (address) {
        return _governor();
    }

    /**
     * @dev Returns the address of the current Governor.
     */
    function _governor() internal view returns (address governorOut) {
        bytes32 position = governorPosition;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            governorOut := sload(position)
        }
    }

    /**
     * @dev Returns the address of the pending Governor.
     */
    function _pendingGovernor()
        internal
        view
        returns (address pendingGovernor)
    {
        bytes32 position = pendingGovernorPosition;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            pendingGovernor := sload(position)
        }
    }

    /**
     * @dev Throws if called by any account other than the Governor.
     */
    modifier onlyGovernor() {
        require(isGovernor(), "Caller is not the Governor");
        _;
    }

    /**
     * @notice Returns true if the caller is the current Governor.
     */
    function isGovernor() public view returns (bool) {
        return msg.sender == _governor();
    }

    function _setGovernor(address newGovernor) internal {
        bytes32 position = governorPosition;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(position, newGovernor)
        }
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        bytes32 position = reentryStatusPosition;
        uint256 _reentry_status;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            _reentry_status := sload(position)
        }

        // On the first call to nonReentrant, _notEntered will be true
        require(_reentry_status != _ENTERED, "Reentrant call");

        // Any calls to nonReentrant after this point will fail
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(position, _ENTERED)
        }

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(position, _NOT_ENTERED)
        }
    }

    function _setPendingGovernor(address newGovernor) internal {
        bytes32 position = pendingGovernorPosition;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            sstore(position, newGovernor)
        }
    }

    /**
     * @notice Transfers Governance of the contract to a new account (`newGovernor`).
     * Can only be called by the current Governor. Must be claimed for this to complete
     * @param _newGovernor Address of the new Governor
     */
    function transferGovernance(address _newGovernor) external onlyGovernor {
        _setPendingGovernor(_newGovernor);
        emit PendingGovernorshipTransfer(_governor(), _newGovernor);
    }

    /**
     * @notice Claim Governance of the contract to a new account (`newGovernor`).
     * Can only be called by the new Governor.
     */
    function claimGovernance() external {
        require(
            msg.sender == _pendingGovernor(),
            "Only the pending Governor can complete the claim"
        );
        _changeGovernor(msg.sender);
    }

    /**
     * @dev Change Governance of the contract to a new account (`newGovernor`).
     * @param _newGovernor Address of the new Governor
     */
    function _changeGovernor(address _newGovernor) internal {
        require(_newGovernor != address(0), "New Governor is address(0)");
        emit GovernorshipTransferred(_governor(), _newGovernor);
        _setGovernor(_newGovernor);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import { OUSD } from "./OUSD.sol";

/**
 * @title Origin Sonic (OS) token on Sonic
 * @author Origin Protocol Inc
 */
contract OSonic is OUSD {
    function symbol() external pure override returns (string memory) {
        return "OS";
    }

    function name() external pure override returns (string memory) {
        return "Origin Sonic";
    }
}

// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;

/**
 * @title OUSD Token Contract
 * @dev ERC20 compatible contract for OUSD
 * @dev Implements an elastic supply
 * @author Origin Protocol Inc
 */
import { Governable } from "../governance/Governable.sol";
import { SafeCast } from "@openzeppelin/contracts/utils/math/SafeCast.sol";

contract OUSD is Governable {
    using SafeCast for int256;
    using SafeCast for uint256;

    /// @dev Event triggered when the supply changes
    /// @param totalSupply Updated token total supply
    /// @param rebasingCredits Updated token rebasing credits
    /// @param rebasingCreditsPerToken Updated token rebasing credits per token
    event TotalSupplyUpdatedHighres(
        uint256 totalSupply,
        uint256 rebasingCredits,
        uint256 rebasingCreditsPerToken
    );
    /// @dev Event triggered when an account opts in for rebasing
    /// @param account Address of the account
    event AccountRebasingEnabled(address account);
    /// @dev Event triggered when an account opts out of rebasing
    /// @param account Address of the account
    event AccountRebasingDisabled(address account);
    /// @dev Emitted when `value` tokens are moved from one account `from` to
    ///      another `to`.
    /// @param from Address of the account tokens are moved from
    /// @param to Address of the account tokens are moved to
    /// @param value Amount of tokens transferred
    event Transfer(address indexed from, address indexed to, uint256 value);
    /// @dev Emitted when the allowance of a `spender` for an `owner` is set by
    ///      a call to {approve}. `value` is the new allowance.
    /// @param owner Address of the owner approving allowance
    /// @param spender Address of the spender allowance is granted to
    /// @param value Amount of tokens spender can transfer
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    /// @dev Yield resulting from {changeSupply} that a `source` account would
    ///      receive is directed to `target` account.
    /// @param source Address of the source forwarding the yield
    /// @param target Address of the target receiving the yield
    event YieldDelegated(address source, address target);
    /// @dev Yield delegation from `source` account to the `target` account is
    ///      suspended.
    /// @param source Address of the source suspending yield forwarding
    /// @param target Address of the target no longer receiving yield from `source`
    ///        account
    event YieldUndelegated(address source, address target);

    enum RebaseOptions {
        NotSet,
        StdNonRebasing,
        StdRebasing,
        YieldDelegationSource,
        YieldDelegationTarget
    }

    uint256[154] private _gap; // Slots to align with deployed contract
    uint256 private constant MAX_SUPPLY = type(uint128).max;
    /// @dev The amount of tokens in existence
    uint256 public totalSupply;
    mapping(address => mapping(address => uint256)) private allowances;
    /// @dev The vault with privileges to execute {mint}, {burn}
    ///     and {changeSupply}
    address public vaultAddress;
    mapping(address => uint256) internal creditBalances;
    // the 2 storage variables below need trailing underscores to not name collide with public functions
    uint256 private rebasingCredits_; // Sum of all rebasing credits (creditBalances for rebasing accounts)
    uint256 private rebasingCreditsPerToken_;
    /// @dev The amount of tokens that are not rebasing - receiving yield
    uint256 public nonRebasingSupply;
    mapping(address => uint256) internal alternativeCreditsPerToken;
    /// @dev A map of all addresses and their respective RebaseOptions
    mapping(address => RebaseOptions) public rebaseState;
    mapping(address => uint256) private __deprecated_isUpgraded;
    /// @dev A map of addresses that have yields forwarded to. This is an
    ///      inverse mapping of {yieldFrom}
    /// Key Account forwarding yield
    /// Value Account receiving yield
    mapping(address => address) public yieldTo;
    /// @dev A map of addresses that are receiving the yield. This is an
    ///      inverse mapping of {yieldTo}
    /// Key Account receiving yield
    /// Value Account forwarding yield
    mapping(address => address) public yieldFrom;

    uint256 private constant RESOLUTION_INCREASE = 1e9;
    uint256[34] private __gap; // including below gap totals up to 200

    /// @dev Initializes the contract and sets necessary variables.
    /// @param _vaultAddress Address of the vault contract
    /// @param _initialCreditsPerToken The starting rebasing credits per token.
    function initialize(address _vaultAddress, uint256 _initialCreditsPerToken)
        external
        onlyGovernor
    {
        require(_vaultAddress != address(0), "Zero vault address");
        require(vaultAddress == address(0), "Already initialized");

        rebasingCreditsPerToken_ = _initialCreditsPerToken;
        vaultAddress = _vaultAddress;
    }

    /// @dev Returns the symbol of the token, a shorter version
    ///      of the name.
    function symbol() external pure virtual returns (string memory) {
        return "OUSD";
    }

    /// @dev Returns the name of the token.
    function name() external pure virtual returns (string memory) {
        return "Origin Dollar";
    }

    /// @dev Returns the number of decimals used to get its user representation.
    function decimals() external pure virtual returns (uint8) {
        return 18;
    }

    /**
     * @dev Verifies that the caller is the Vault contract
     */
    modifier onlyVault() {
        require(vaultAddress == msg.sender, "Caller is not the Vault");
        _;
    }

    /**
     * @return High resolution rebasingCreditsPerToken
     */
    function rebasingCreditsPerTokenHighres() external view returns (uint256) {
        return rebasingCreditsPerToken_;
    }

    /**
     * @return Low resolution rebasingCreditsPerToken
     */
    function rebasingCreditsPerToken() external view returns (uint256) {
        return rebasingCreditsPerToken_ / RESOLUTION_INCREASE;
    }

    /**
     * @return High resolution total number of rebasing credits
     */
    function rebasingCreditsHighres() external view returns (uint256) {
        return rebasingCredits_;
    }

    /**
     * @return Low resolution total number of rebasing credits
     */
    function rebasingCredits() external view returns (uint256) {
        return rebasingCredits_ / RESOLUTION_INCREASE;
    }

    /**
     * @notice Gets the balance of the specified address.
     * @param _account Address to query the balance of.
     * @return A uint256 representing the amount of base units owned by the
     *         specified address.
     */
    function balanceOf(address _account) public view returns (uint256) {
        RebaseOptions state = rebaseState[_account];
        if (state == RebaseOptions.YieldDelegationSource) {
            // Saves a slot read when transferring to or from a yield delegating source
            // since we know creditBalances equals the balance.
            return creditBalances[_account];
        }
        uint256 baseBalance = (creditBalances[_account] * 1e18) /
            _creditsPerToken(_account);
        if (state == RebaseOptions.YieldDelegationTarget) {
            // creditBalances of yieldFrom accounts equals token balances
            return baseBalance - creditBalances[yieldFrom[_account]];
        }
        return baseBalance;
    }

    /**
     * @notice Gets the credits balance of the specified address.
     * @dev Backwards compatible with old low res credits per token.
     * @param _account The address to query the balance of.
     * @return (uint256, uint256) Credit balance and credits per token of the
     *         address
     */
    function creditsBalanceOf(address _account)
        external
        view
        returns (uint256, uint256)
    {
        uint256 cpt = _creditsPerToken(_account);
        if (cpt == 1e27) {
            // For a period before the resolution upgrade, we created all new
            // contract accounts at high resolution. Since they are not changing
            // as a result of this upgrade, we will return their true values
            return (creditBalances[_account], cpt);
        } else {
            return (
                creditBalances[_account] / RESOLUTION_INCREASE,
                cpt / RESOLUTION_INCREASE
            );
        }
    }

    /**
     * @notice Gets the credits balance of the specified address.
     * @param _account The address to query the balance of.
     * @return (uint256, uint256, bool) Credit balance, credits per token of the
     *         address, and isUpgraded
     */
    function creditsBalanceOfHighres(address _account)
        external
        view
        returns (
            uint256,
            uint256,
            bool
        )
    {
        return (
            creditBalances[_account],
            _creditsPerToken(_account),
            true // all accounts have their resolution "upgraded"
        );
    }

    // Backwards compatible view
    function nonRebasingCreditsPerToken(address _account)
        external
        view
        returns (uint256)
    {
        return alternativeCreditsPerToken[_account];
    }

    /**
     * @notice Transfer tokens to a specified address.
     * @param _to the address to transfer to.
     * @param _value the amount to be transferred.
     * @return true on success.
     */
    function transfer(address _to, uint256 _value) external returns (bool) {
        require(_to != address(0), "Transfer to zero address");

        _executeTransfer(msg.sender, _to, _value);

        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
     * @notice Transfer tokens from one address to another.
     * @param _from The address you want to send tokens from.
     * @param _to The address you want to transfer to.
     * @param _value The amount of tokens to be transferred.
     * @return true on success.
     */
    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) external returns (bool) {
        require(_to != address(0), "Transfer to zero address");
        uint256 userAllowance = allowances[_from][msg.sender];
        require(_value <= userAllowance, "Allowance exceeded");

        unchecked {
            allowances[_from][msg.sender] = userAllowance - _value;
        }

        _executeTransfer(_from, _to, _value);

        emit Transfer(_from, _to, _value);
        return true;
    }

    function _executeTransfer(
        address _from,
        address _to,
        uint256 _value
    ) internal {
        (
            int256 fromRebasingCreditsDiff,
            int256 fromNonRebasingSupplyDiff
        ) = _adjustAccount(_from, -_value.toInt256());
        (
            int256 toRebasingCreditsDiff,
            int256 toNonRebasingSupplyDiff
        ) = _adjustAccount(_to, _value.toInt256());

        _adjustGlobals(
            fromRebasingCreditsDiff + toRebasingCreditsDiff,
            fromNonRebasingSupplyDiff + toNonRebasingSupplyDiff
        );
    }

    function _adjustAccount(address _account, int256 _balanceChange)
        internal
        returns (int256 rebasingCreditsDiff, int256 nonRebasingSupplyDiff)
    {
        RebaseOptions state = rebaseState[_account];
        int256 currentBalance = balanceOf(_account).toInt256();
        if (currentBalance + _balanceChange < 0) {
            revert("Transfer amount exceeds balance");
        }
        uint256 newBalance = (currentBalance + _balanceChange).toUint256();

        if (state == RebaseOptions.YieldDelegationSource) {
            address target = yieldTo[_account];
            uint256 targetOldBalance = balanceOf(target);
            uint256 targetNewCredits = _balanceToRebasingCredits(
                targetOldBalance + newBalance
            );
            rebasingCreditsDiff =
                targetNewCredits.toInt256() -
                creditBalances[target].toInt256();

            creditBalances[_account] = newBalance;
            creditBalances[target] = targetNewCredits;
        } else if (state == RebaseOptions.YieldDelegationTarget) {
            uint256 newCredits = _balanceToRebasingCredits(
                newBalance + creditBalances[yieldFrom[_account]]
            );
            rebasingCreditsDiff =
                newCredits.toInt256() -
                creditBalances[_account].toInt256();
            creditBalances[_account] = newCredits;
        } else {
            _autoMigrate(_account);
            uint256 alternativeCreditsPerTokenMem = alternativeCreditsPerToken[
                _account
            ];
            if (alternativeCreditsPerTokenMem > 0) {
                nonRebasingSupplyDiff = _balanceChange;
                if (alternativeCreditsPerTokenMem != 1e18) {
                    alternativeCreditsPerToken[_account] = 1e18;
                }
                creditBalances[_account] = newBalance;
            } else {
                uint256 newCredits = _balanceToRebasingCredits(newBalance);
                rebasingCreditsDiff =
                    newCredits.toInt256() -
                    creditBalances[_account].toInt256();
                creditBalances[_account] = newCredits;
            }
        }
    }

    function _adjustGlobals(
        int256 _rebasingCreditsDiff,
        int256 _nonRebasingSupplyDiff
    ) internal {
        if (_rebasingCreditsDiff != 0) {
            rebasingCredits_ = (rebasingCredits_.toInt256() +
                _rebasingCreditsDiff).toUint256();
        }
        if (_nonRebasingSupplyDiff != 0) {
            nonRebasingSupply = (nonRebasingSupply.toInt256() +
                _nonRebasingSupplyDiff).toUint256();
        }
    }

    /**
     * @notice Function to check the amount of tokens that _owner has allowed
     *      to `_spender`.
     * @param _owner The address which owns the funds.
     * @param _spender The address which will spend the funds.
     * @return The number of tokens still available for the _spender.
     */
    function allowance(address _owner, address _spender)
        external
        view
        returns (uint256)
    {
        return allowances[_owner][_spender];
    }

    /**
     * @notice Approve the passed address to spend the specified amount of
     *      tokens on behalf of msg.sender.
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     * @return true on success.
     */
    function approve(address _spender, uint256 _value) external returns (bool) {
        allowances[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * @notice Creates `_amount` tokens and assigns them to `_account`,
     *     increasing the total supply.
     */
    function mint(address _account, uint256 _amount) external onlyVault {
        require(_account != address(0), "Mint to the zero address");

        // Account
        (
            int256 toRebasingCreditsDiff,
            int256 toNonRebasingSupplyDiff
        ) = _adjustAccount(_account, _amount.toInt256());
        // Globals
        _adjustGlobals(toRebasingCreditsDiff, toNonRebasingSupplyDiff);
        totalSupply = totalSupply + _amount;

        require(totalSupply < MAX_SUPPLY, "Max supply");
        emit Transfer(address(0), _account, _amount);
    }

    /**
     * @notice Destroys `_amount` tokens from `_account`,
     *     reducing the total supply.
     */
    function burn(address _account, uint256 _amount) external onlyVault {
        require(_account != address(0), "Burn from the zero address");
        if (_amount == 0) {
            return;
        }

        // Account
        (
            int256 toRebasingCreditsDiff,
            int256 toNonRebasingSupplyDiff
        ) = _adjustAccount(_account, -_amount.toInt256());
        // Globals
        _adjustGlobals(toRebasingCreditsDiff, toNonRebasingSupplyDiff);
        totalSupply = totalSupply - _amount;

        emit Transfer(_account, address(0), _amount);
    }

    /**
     * @dev Get the credits per token for an account. Returns a fixed amount
     *      if the account is non-rebasing.
     * @param _account Address of the account.
     */
    function _creditsPerToken(address _account)
        internal
        view
        returns (uint256)
    {
        uint256 alternativeCreditsPerTokenMem = alternativeCreditsPerToken[
            _account
        ];
        if (alternativeCreditsPerTokenMem != 0) {
            return alternativeCreditsPerTokenMem;
        } else {
            return rebasingCreditsPerToken_;
        }
    }

    /**
     * @dev Auto migrate contracts to be non rebasing,
     *     unless they have opted into yield.
     * @param _account Address of the account.
     */
    function _autoMigrate(address _account) internal {
        bool isContract = _account.code.length > 0;
        // In previous code versions, contracts would not have had their
        // rebaseState[_account] set to RebaseOptions.NonRebasing when migrated
        // therefore we check the actual accounting used on the account instead.
        if (
            isContract &&
            rebaseState[_account] == RebaseOptions.NotSet &&
            alternativeCreditsPerToken[_account] == 0
        ) {
            _rebaseOptOut(_account);
        }
    }

    /**
     * @dev Calculates credits from contract's global rebasingCreditsPerToken_, and
     *      also balance that corresponds to those credits. The latter is important
     *      when adjusting the contract's global nonRebasingSupply to circumvent any
     *      possible rounding errors.
     *
     * @param _balance Balance of the account.
     */
    function _balanceToRebasingCredits(uint256 _balance)
        internal
        view
        returns (uint256 rebasingCredits)
    {
        // Rounds up, because we need to ensure that accounts always have
        // at least the balance that they should have.
        // Note this should always be used on an absolute account value,
        // not on a possibly negative diff, because then the rounding would be wrong.
        return ((_balance) * rebasingCreditsPerToken_ + 1e18 - 1) / 1e18;
    }

    /**
     * @notice The calling account will start receiving yield after a successful call.
     * @param _account Address of the account.
     */
    function governanceRebaseOptIn(address _account) external onlyGovernor {
        require(_account != address(0), "Zero address not allowed");
        _rebaseOptIn(_account);
    }

    /**
     * @notice The calling account will start receiving yield after a successful call.
     */
    function rebaseOptIn() external {
        _rebaseOptIn(msg.sender);
    }

    function _rebaseOptIn(address _account) internal {
        uint256 balance = balanceOf(_account);

        // prettier-ignore
        require(
            alternativeCreditsPerToken[_account] > 0 ||
                // Accounts may explicitly `rebaseOptIn` regardless of
                // accounting if they have a 0 balance.
                creditBalances[_account] == 0
            ,
            "Account must be non-rebasing"
        );
        RebaseOptions state = rebaseState[_account];
        // prettier-ignore
        require(
            state == RebaseOptions.StdNonRebasing ||
                state == RebaseOptions.NotSet,
            "Only standard non-rebasing accounts can opt in"
        );

        uint256 newCredits = _balanceToRebasingCredits(balance);

        // Account
        rebaseState[_account] = RebaseOptions.StdRebasing;
        alternativeCreditsPerToken[_account] = 0;
        creditBalances[_account] = newCredits;
        // Globals
        _adjustGlobals(newCredits.toInt256(), -balance.toInt256());

        emit AccountRebasingEnabled(_account);
    }

    /**
     * @notice The calling account will no longer receive yield
     */
    function rebaseOptOut() external {
        _rebaseOptOut(msg.sender);
    }

    function _rebaseOptOut(address _account) internal {
        require(
            alternativeCreditsPerToken[_account] == 0,
            "Account must be rebasing"
        );
        RebaseOptions state = rebaseState[_account];
        require(
            state == RebaseOptions.StdRebasing || state == RebaseOptions.NotSet,
            "Only standard rebasing accounts can opt out"
        );

        uint256 oldCredits = creditBalances[_account];
        uint256 balance = balanceOf(_account);

        // Account
        rebaseState[_account] = RebaseOptions.StdNonRebasing;
        alternativeCreditsPerToken[_account] = 1e18;
        creditBalances[_account] = balance;
        // Globals
        _adjustGlobals(-oldCredits.toInt256(), balance.toInt256());

        emit AccountRebasingDisabled(_account);
    }

    /**
     * @notice Distribute yield to users. This changes the exchange rate
     *  between "credits" and OUSD tokens to change rebasing user's balances.
     * @param _newTotalSupply New total supply of OUSD.
     */
    function changeSupply(uint256 _newTotalSupply) external onlyVault {
        require(totalSupply > 0, "Cannot increase 0 supply");

        if (totalSupply == _newTotalSupply) {
            emit TotalSupplyUpdatedHighres(
                totalSupply,
                rebasingCredits_,
                rebasingCreditsPerToken_
            );
            return;
        }

        totalSupply = _newTotalSupply > MAX_SUPPLY
            ? MAX_SUPPLY
            : _newTotalSupply;

        uint256 rebasingSupply = totalSupply - nonRebasingSupply;
        // round up in the favour of the protocol
        rebasingCreditsPerToken_ =
            (rebasingCredits_ * 1e18 + rebasingSupply - 1) /
            rebasingSupply;

        require(rebasingCreditsPerToken_ > 0, "Invalid change in supply");

        emit TotalSupplyUpdatedHighres(
            totalSupply,
            rebasingCredits_,
            rebasingCreditsPerToken_
        );
    }

    /*
     * @notice Send the yield from one account to another account.
     *         Each account keeps its own balances.
     */
    function delegateYield(address _from, address _to) external onlyGovernor {
        require(_from != address(0), "Zero from address not allowed");
        require(_to != address(0), "Zero to address not allowed");

        require(_from != _to, "Cannot delegate to self");
        require(
            yieldFrom[_to] == address(0) &&
                yieldTo[_to] == address(0) &&
                yieldFrom[_from] == address(0) &&
                yieldTo[_from] == address(0),
            "Blocked by existing yield delegation"
        );
        RebaseOptions stateFrom = rebaseState[_from];
        RebaseOptions stateTo = rebaseState[_to];

        require(
            stateFrom == RebaseOptions.NotSet ||
                stateFrom == RebaseOptions.StdNonRebasing ||
                stateFrom == RebaseOptions.StdRebasing,
            "Invalid rebaseState from"
        );

        require(
            stateTo == RebaseOptions.NotSet ||
                stateTo == RebaseOptions.StdNonRebasing ||
                stateTo == RebaseOptions.StdRebasing,
            "Invalid rebaseState to"
        );

        if (alternativeCreditsPerToken[_from] == 0) {
            _rebaseOptOut(_from);
        }
        if (alternativeCreditsPerToken[_to] > 0) {
            _rebaseOptIn(_to);
        }

        uint256 fromBalance = balanceOf(_from);
        uint256 toBalance = balanceOf(_to);
        uint256 oldToCredits = creditBalances[_to];
        uint256 newToCredits = _balanceToRebasingCredits(
            fromBalance + toBalance
        );

        // Set up the bidirectional links
        yieldTo[_from] = _to;
        yieldFrom[_to] = _from;

        // Local
        rebaseState[_from] = RebaseOptions.YieldDelegationSource;
        alternativeCreditsPerToken[_from] = 1e18;
        creditBalances[_from] = fromBalance;
        rebaseState[_to] = RebaseOptions.YieldDelegationTarget;
        creditBalances[_to] = newToCredits;

        // Global
        int256 creditsChange = newToCredits.toInt256() -
            oldToCredits.toInt256();
        _adjustGlobals(creditsChange, -(fromBalance).toInt256());
        emit YieldDelegated(_from, _to);
    }

    /*
     * @notice Stop sending the yield from one account to another account.
     */
    function undelegateYield(address _from) external onlyGovernor {
        // Require a delegation, which will also ensure a valid delegation
        require(yieldTo[_from] != address(0), "Zero address not allowed");

        address to = yieldTo[_from];
        uint256 fromBalance = balanceOf(_from);
        uint256 toBalance = balanceOf(to);
        uint256 oldToCredits = creditBalances[to];
        uint256 newToCredits = _balanceToRebasingCredits(toBalance);

        // Remove the bidirectional links
        yieldFrom[to] = address(0);
        yieldTo[_from] = address(0);

        // Local
        rebaseState[_from] = RebaseOptions.StdNonRebasing;
        // alternativeCreditsPerToken[from] already 1e18 from `delegateYield()`
        creditBalances[_from] = fromBalance;
        rebaseState[to] = RebaseOptions.StdRebasing;
        // alternativeCreditsPerToken[to] already 0 from `delegateYield()`
        creditBalances[to] = newToCredits;

        // Global
        int256 creditsChange = newToCredits.toInt256() -
            oldToCredits.toInt256();
        _adjustGlobals(creditsChange, fromBalance.toInt256());
        emit YieldUndelegated(_from, to);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import { ERC4626 } from "../../lib/openzeppelin/contracts/token/ERC20/extensions/ERC4626.sol";
import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { IERC20Metadata } from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

import { Governable } from "../governance/Governable.sol";
import { Initializable } from "../utils/Initializable.sol";
import { OSonic } from "./OSonic.sol";

/**
 * @title Wrapped Origin Sonic (wOS) token on Sonic
 * @author Origin Protocol Inc
 */
contract WOSonic is ERC4626, Governable, Initializable {
    using SafeERC20 for IERC20;

    constructor(
        ERC20 underlying_,
        string memory name_,
        string memory symbol_
    ) ERC20(name_, symbol_) ERC4626(underlying_) Governable() {}

    /**
     * @notice Enable Origin Sonic rebasing for this contract
     */
    function initialize() external onlyGovernor initializer {
        OSonic(address(asset())).rebaseOptIn();
    }

    function name()
        public
        view
        virtual
        override(ERC20, IERC20Metadata)
        returns (string memory)
    {
        return "Wrapped Origin Sonic";
    }

    function symbol()
        public
        view
        virtual
        override(ERC20, IERC20Metadata)
        returns (string memory)
    {
        return "wOS";
    }

    /**
     * @notice Transfer token to governor. Intended for recovering tokens stuck in
     *      contract, i.e. mistaken sends. Cannot transfer Origin S
     * @param asset_ Address for the asset
     * @param amount_ Amount of the asset to transfer
     */
    function transferToken(address asset_, uint256 amount_)
        external
        onlyGovernor
    {
        require(asset_ != address(asset()), "Cannot collect OS");
        IERC20(asset_).safeTransfer(governor(), amount_);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

/**
 * @title Base contract any contracts that need to initialize state after deployment.
 * @author Origin Protocol Inc
 */
abstract contract Initializable {
    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private initializing;

    /**
     * @dev Modifier to protect an initializer function from being invoked twice.
     */
    modifier initializer() {
        require(
            initializing || !initialized,
            "Initializable: contract is already initialized"
        );

        bool isTopLevelCall = !initializing;
        if (isTopLevelCall) {
            initializing = true;
            initialized = true;
        }

        _;

        if (isTopLevelCall) {
            initializing = false;
        }
    }

    uint256[50] private ______gap;
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import { IERC4626 } from "../../../../interfaces/IERC4626.sol";
import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import { IERC20Metadata } from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";

// From Open Zeppelin draft PR commit:
// fac43034dca85ff539db3fc8aa2a7084b843d454
// https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3171

abstract contract ERC4626 is ERC20, IERC4626 {
    IERC20Metadata private immutable _asset;

    constructor(IERC20Metadata __asset) {
        _asset = __asset;
    }

    /** @dev See {IERC4262-asset} */
    function asset() public view virtual override returns (address) {
        return address(_asset);
    }

    /** @dev See {IERC4262-totalAssets} */
    function totalAssets() public view virtual override returns (uint256) {
        return _asset.balanceOf(address(this));
    }

    /**
     * @dev See {IERC4262-convertToShares}
     *
     * Will revert if asserts > 0, totalSupply > 0 and totalAssets = 0. That corresponds to a case where any asset
     * would represent an infinite amout of shares.
     */
    function convertToShares(uint256 assets) public view virtual override returns (uint256 shares) {
        uint256 supply = totalSupply();

        return
            (assets == 0 || supply == 0)
                ? (assets * 10**decimals()) / 10**_asset.decimals()
                : (assets * supply) / totalAssets();
    }

    /** @dev See {IERC4262-convertToAssets} */
    function convertToAssets(uint256 shares) public view virtual override returns (uint256 assets) {
        uint256 supply = totalSupply();

        return (supply == 0) ? (shares * 10**_asset.decimals()) / 10**decimals() : (shares * totalAssets()) / supply;
    }

    /** @dev See {IERC4262-maxDeposit} */
    function maxDeposit(address) public view virtual override returns (uint256) {
        return type(uint256).max;
    }

    /** @dev See {IERC4262-maxMint} */
    function maxMint(address) public view virtual override returns (uint256) {
        return type(uint256).max;
    }

    /** @dev See {IERC4262-maxWithdraw} */
    function maxWithdraw(address owner) public view virtual override returns (uint256) {
        return convertToAssets(balanceOf(owner));
    }

    /** @dev See {IERC4262-maxRedeem} */
    function maxRedeem(address owner) public view virtual override returns (uint256) {
        return balanceOf(owner);
    }

    /** @dev See {IERC4262-previewDeposit} */
    function previewDeposit(uint256 assets) public view virtual override returns (uint256) {
        return convertToShares(assets);
    }

    /** @dev See {IERC4262-previewMint} */
    function previewMint(uint256 shares) public view virtual override returns (uint256) {
        uint256 assets = convertToAssets(shares);
        return assets + (convertToShares(assets) < shares ? 1 : 0);
    }

    /** @dev See {IERC4262-previewWithdraw} */
    function previewWithdraw(uint256 assets) public view virtual override returns (uint256) {
        uint256 shares = convertToShares(assets);
        return shares + (convertToAssets(shares) < assets ? 1 : 0);
    }

    /** @dev See {IERC4262-previewRedeem} */
    function previewRedeem(uint256 shares) public view virtual override returns (uint256) {
        return convertToAssets(shares);
    }

    /** @dev See {IERC4262-deposit} */
    function deposit(uint256 assets, address receiver) public virtual override returns (uint256) {
        require(assets <= maxDeposit(receiver), "ERC4626: deposit more then max");

        address caller = _msgSender();
        uint256 shares = previewDeposit(assets);

        // if _asset is ERC777, transferFrom can call reenter BEFORE the transfer happens through
        // the tokensToSend hook, so we need to transfer before we mint to keep the invariants.
        SafeERC20.safeTransferFrom(_asset, caller, address(this), assets);
        _mint(receiver, shares);

        emit Deposit(caller, receiver, assets, shares);

        return shares;
    }

    /** @dev See {IERC4262-mint} */
    function mint(uint256 shares, address receiver) public virtual override returns (uint256) {
        require(shares <= maxMint(receiver), "ERC4626: mint more then max");

        address caller = _msgSender();
        uint256 assets = previewMint(shares);

        // if _asset is ERC777, transferFrom can call reenter BEFORE the transfer happens through
        // the tokensToSend hook, so we need to transfer before we mint to keep the invariants.
        SafeERC20.safeTransferFrom(_asset, caller, address(this), assets);
        _mint(receiver, shares);

        emit Deposit(caller, receiver, assets, shares);

        return assets;
    }

    /** @dev See {IERC4262-withdraw} */
    function withdraw(
        uint256 assets,
        address receiver,
        address owner
    ) public virtual override returns (uint256) {
        require(assets <= maxWithdraw(owner), "ERC4626: withdraw more then max");

        address caller = _msgSender();
        uint256 shares = previewWithdraw(assets);

        if (caller != owner) {
            _spendAllowance(owner, caller, shares);
        }

        // if _asset is ERC777, transfer can call reenter AFTER the transfer happens through
        // the tokensReceived hook, so we need to transfer after we burn to keep the invariants.
        _burn(owner, shares);
        SafeERC20.safeTransfer(_asset, receiver, assets);

        emit Withdraw(caller, receiver, owner, assets, shares);

        return shares;
    }

    /** @dev See {IERC4262-redeem} */
    function redeem(
        uint256 shares,
        address receiver,
        address owner
    ) public virtual override returns (uint256) {
        require(shares <= maxRedeem(owner), "ERC4626: redeem more then max");

        address caller = _msgSender();
        uint256 assets = previewRedeem(shares);

        if (caller != owner) {
            _spendAllowance(owner, caller, shares);
        }

        // if _asset is ERC777, transfer can call reenter AFTER the transfer happens through
        // the tokensReceived hook, so we need to transfer after we burn to keep the invariants.
        _burn(owner, shares);
        SafeERC20.safeTransfer(_asset, receiver, assets);

        emit Withdraw(caller, receiver, owner, assets, shares);

        return assets;
    }

    // Included here, since this method was not yet present in
    // the version of Open Zeppelin ERC20 code we use.
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import { IERC20Metadata } from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";

interface IERC4626 is IERC20, IERC20Metadata {
    event Deposit(address indexed caller, address indexed owner, uint256 assets, uint256 shares);

    event Withdraw(
        address indexed caller,
        address indexed receiver,
        address indexed owner,
        uint256 assets,
        uint256 shares
    );

    /**
     * @dev Returns the address of the underlying token used for the Vault for accounting, depositing, and withdrawing.
     *
     * - MUST be an ERC-20 token contract.
     * - MUST NOT revert.
     */
    function asset() external view returns (address assetTokenAddress);

    /**
     * @dev Returns the total amount of the underlying asset that is “managed” by Vault.
     *
     * - SHOULD include any compounding that occurs from yield.
     * - MUST be inclusive of any fees that are charged against assets in the Vault.
     * - MUST NOT revert.
     */
    function totalAssets() external view returns (uint256 totalManagedAssets);

    /**
     * @dev Returns the amount of shares that the Vault would exchange for the amount of assets provided, in an ideal
     * scenario where all the conditions are met.
     *
     * - MUST NOT be inclusive of any fees that are charged against assets in the Vault.
     * - MUST NOT show any variations depending on the caller.
     * - MUST NOT reflect slippage or other on-chain conditions, when performing the actual exchange.
     * - MUST NOT revert.
     *
     * NOTE: This calculation MAY NOT reflect the “per-user” price-per-share, and instead should reflect the
     * “average-user’s” price-per-share, meaning what the average user should expect to see when exchanging to and
     * from.
     */
    function convertToShares(uint256 assets) external view returns (uint256 shares);

    /**
     * @dev Returns the amount of assets that the Vault would exchange for the amount of shares provided, in an ideal
     * scenario where all the conditions are met.
     *
     * - MUST NOT be inclusive of any fees that are charged against assets in the Vault.
     * - MUST NOT show any variations depending on the caller.
     * - MUST NOT reflect slippage or other on-chain conditions, when performing the actual exchange.
     * - MUST NOT revert.
     *
     * NOTE: This calculation MAY NOT reflect the “per-user” price-per-share, and instead should reflect the
     * “average-user’s” price-per-share, meaning what the average user should expect to see when exchanging to and
     * from.
     */
    function convertToAssets(uint256 shares) external view returns (uint256 assets);

    /**
     * @dev Returns the maximum amount of the underlying asset that can be deposited into the Vault for the receiver,
     * through a deposit call.
     *
     * - MUST return a limited value if receiver is subject to some deposit limit.
     * - MUST return 2 ** 256 - 1 if there is no limit on the maximum amount of assets that may be deposited.
     * - MUST NOT revert.
     */
    function maxDeposit(address receiver) external view returns (uint256 maxAssets);

    /**
     * @dev Allows an on-chain or off-chain user to simulate the effects of their deposit at the current block, given
     * current on-chain conditions.
     *
     * - MUST return as close to and no more than the exact amount of Vault shares that would be minted in a deposit
     *   call in the same transaction. I.e. deposit should return the same or more shares as previewDeposit if called
     *   in the same transaction.
     * - MUST NOT account for deposit limits like those returned from maxDeposit and should always act as though the
     *   deposit would be accepted, regardless if the user has enough tokens approved, etc.
     * - MUST be inclusive of deposit fees. Integrators should be aware of the existence of deposit fees.
     * - MUST NOT revert.
     *
     * NOTE: any unfavorable discrepancy between convertToShares and previewDeposit SHOULD be considered slippage in
     * share price or some other type of condition, meaning the depositor will lose assets by depositing.
     */
    function previewDeposit(uint256 assets) external view returns (uint256 shares);

    /**
     * @dev Mints shares Vault shares to receiver by depositing exactly amount of underlying tokens.
     *
     * - MUST emit the Deposit event.
     * - MAY support an additional flow in which the underlying tokens are owned by the Vault contract before the
     *   deposit execution, and are accounted for during deposit.
     * - MUST revert if all of assets cannot be deposited (due to deposit limit being reached, slippage, the user not
     *   approving enough underlying tokens to the Vault contract, etc).
     *
     * NOTE: most implementations will require pre-approval of the Vault with the Vault’s underlying asset token.
     */
    function deposit(uint256 assets, address receiver) external returns (uint256 shares);

    /**
     * @dev Returns the maximum amount of the Vault shares that can be minted for the receiver, through a mint call.
     * - MUST return a limited value if receiver is subject to some mint limit.
     * - MUST return 2 ** 256 - 1 if there is no limit on the maximum amount of shares that may be minted.
     * - MUST NOT revert.
     */
    function maxMint(address receiver) external view returns (uint256 maxShares);

    /**
     * @dev Allows an on-chain or off-chain user to simulate the effects of their mint at the current block, given
     * current on-chain conditions.
     *
     * - MUST return as close to and no fewer than the exact amount of assets that would be deposited in a mint call
     *   in the same transaction. I.e. mint should return the same or fewer assets as previewMint if called in the
     *   same transaction.
     * - MUST NOT account for mint limits like those returned from maxMint and should always act as though the mint
     *   would be accepted, regardless if the user has enough tokens approved, etc.
     * - MUST be inclusive of deposit fees. Integrators should be aware of the existence of deposit fees.
     * - MUST NOT revert.
     *
     * NOTE: any unfavorable discrepancy between convertToAssets and previewMint SHOULD be considered slippage in
     * share price or some other type of condition, meaning the depositor will lose assets by minting.
     */
    function previewMint(uint256 shares) external view returns (uint256 assets);

    /**
     * @dev Mints exactly shares Vault shares to receiver by depositing amount of underlying tokens.
     *
     * - MUST emit the Deposit event.
     * - MAY support an additional flow in which the underlying tokens are owned by the Vault contract before the mint
     *   execution, and are accounted for during mint.
     * - MUST revert if all of shares cannot be minted (due to deposit limit being reached, slippage, the user not
     *   approving enough underlying tokens to the Vault contract, etc).
     *
     * NOTE: most implementations will require pre-approval of the Vault with the Vault’s underlying asset token.
     */
    function mint(uint256 shares, address receiver) external returns (uint256 assets);

    /**
     * @dev Returns the maximum amount of the underlying asset that can be withdrawn from the owner balance in the
     * Vault, through a withdraw call.
     *
     * - MUST return a limited value if owner is subject to some withdrawal limit or timelock.
     * - MUST NOT revert.
     */
    function maxWithdraw(address owner) external view returns (uint256 maxAssets);

    /**
     * @dev Allows an on-chain or off-chain user to simulate the effects of their withdrawal at the current block,
     * given current on-chain conditions.
     *
     * - MUST return as close to and no fewer than the exact amount of Vault shares that would be burned in a withdraw
     *   call in the same transaction. I.e. withdraw should return the same or fewer shares as previewWithdraw if
     *   called
     *   in the same transaction.
     * - MUST NOT account for withdrawal limits like those returned from maxWithdraw and should always act as though
     *   the withdrawal would be accepted, regardless if the user has enough shares, etc.
     * - MUST be inclusive of withdrawal fees. Integrators should be aware of the existence of withdrawal fees.
     * - MUST NOT revert.
     *
     * NOTE: any unfavorable discrepancy between convertToShares and previewWithdraw SHOULD be considered slippage in
     * share price or some other type of condition, meaning the depositor will lose assets by depositing.
     */
    function previewWithdraw(uint256 assets) external view returns (uint256 shares);

    /**
     * @dev Burns shares from owner and sends exactly assets of underlying tokens to receiver.
     *
     * - MUST emit the Withdraw event.
     * - MAY support an additional flow in which the underlying tokens are owned by the Vault contract before the
     *   withdraw execution, and are accounted for during withdraw.
     * - MUST revert if all of assets cannot be withdrawn (due to withdrawal limit being reached, slippage, the owner
     *   not having enough shares, etc).
     *
     * Note that some implementations will require pre-requesting to the Vault before a withdrawal may be performed.
     * Those methods should be performed separately.
     */
    function withdraw(
        uint256 assets,
        address receiver,
        address owner
    ) external returns (uint256 shares);

    /**
     * @dev Returns the maximum amount of Vault shares that can be redeemed from the owner balance in the Vault,
     * through a redeem call.
     *
     * - MUST return a limited value if owner is subject to some withdrawal limit or timelock.
     * - MUST return balanceOf(owner) if owner is not subject to any withdrawal limit or timelock.
     * - MUST NOT revert.
     */
    function maxRedeem(address owner) external view returns (uint256 maxShares);

    /**
     * @dev Allows an on-chain or off-chain user to simulate the effects of their redeemption at the current block,
     * given current on-chain conditions.
     *
     * - MUST return as close to and no more than the exact amount of assets that would be withdrawn in a redeem call
     *   in the same transaction. I.e. redeem should return the same or more assets as previewRedeem if called in the
     *   same transaction.
     * - MUST NOT account for redemption limits like those returned from maxRedeem and should always act as though the
     *   redemption would be accepted, regardless if the user has enough shares, etc.
     * - MUST be inclusive of withdrawal fees. Integrators should be aware of the existence of withdrawal fees.
     * - MUST NOT revert.
     *
     * NOTE: any unfavorable discrepancy between convertToAssets and previewRedeem SHOULD be considered slippage in
     * share price or some other type of condition, meaning the depositor will lose assets by redeeming.
     */
    function previewRedeem(uint256 shares) external view returns (uint256 assets);

    /**
     * @dev Burns exactly shares from owner and sends assets of underlying tokens to receiver.
     *
     * - MUST emit the Withdraw event.
     * - MAY support an additional flow in which the underlying tokens are owned by the Vault contract before the
     *   redeem execution, and are accounted for during redeem.
     * - MUST revert if all of shares cannot be redeemed (due to withdrawal limit being reached, slippage, the owner
     *   not having enough shares, etc).
     *
     * NOTE: some implementations will require pre-requesting to the Vault before a withdrawal may be performed.
     * Those methods should be performed separately.
     */
    function redeem(
        uint256 shares,
        address receiver,
        address owner
    ) external returns (uint256 assets);
}

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