// SPDX-License-Identifier: MIT
// Sources flattened with hardhat v2.16.1 https://hardhat.org

// File @openzeppelin/contracts/utils/Context.sol@v4.7.0

// 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;
    }
}


// File @openzeppelin/contracts/access/Ownable.sol@v4.7.0

// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}


// File @openzeppelin/contracts/token/ERC20/IERC20.sol@v4.7.0

// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

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


// File @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol@v4.7.0

// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

/**
 * @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);
}


// File @openzeppelin/contracts/token/ERC20/ERC20.sol@v4.7.0

// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;



/**
 * @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:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, 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}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, 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}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, 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) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, 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) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * 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:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
        }
        _balances[to] += amount;

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, 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 Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    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);
            }
        }
    }

    /**
     * @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 {}
}


// File @openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol@v4.7.0

// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}


// File @openzeppelin/contracts/utils/Address.sol@v4.7.0

// OpenZeppelin Contracts (last updated v4.7.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}


// File @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol@v4.7.0

// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;



/**
 * @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));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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");
        }
    }
}


// File @openzeppelin/contracts/utils/cryptography/MerkleProof.sol@v4.7.0

// OpenZeppelin Contracts (last updated v4.7.0) (utils/cryptography/MerkleProof.sol)

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Tree proofs.
 *
 * The proofs can be generated using the JavaScript library
 * https://github.com/miguelmota/merkletreejs[merkletreejs].
 * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
 *
 * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
 *
 * WARNING: You should avoid using leaf values that are 64 bytes long prior to
 * hashing, or use a hash function other than keccak256 for hashing leaves.
 * This is because the concatenation of a sorted pair of internal nodes in
 * the merkle tree could be reinterpreted as a leaf value.
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Calldata version of {verify}
     *
     * _Available since v4.7._
     */
    function verifyCalldata(
        bytes32[] calldata proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProofCalldata(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merkle tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Calldata version of {processProof}
     *
     * _Available since v4.7._
     */
    function processProofCalldata(bytes32[] calldata proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Returns true if the `leaves` can be proved to be a part of a Merkle tree defined by
     * `root`, according to `proof` and `proofFlags` as described in {processMultiProof}.
     *
     * _Available since v4.7._
     */
    function multiProofVerify(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProof(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Calldata version of {multiProofVerify}
     *
     * _Available since v4.7._
     */
    function multiProofVerifyCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProofCalldata(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Returns the root of a tree reconstructed from `leaves` and the sibling nodes in `proof`,
     * consuming from one or the other at each step according to the instructions given by
     * `proofFlags`.
     *
     * _Available since v4.7._
     */
    function processMultiProof(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuild the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        require(leavesLen + proof.length - 1 == totalHashes, "MerkleProof: invalid multiproof");

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value for the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i] ? leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++] : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            return hashes[totalHashes - 1];
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    /**
     * @dev Calldata version of {processMultiProof}
     *
     * _Available since v4.7._
     */
    function processMultiProofCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuild the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        require(leavesLen + proof.length - 1 == totalHashes, "MerkleProof: invalid multiproof");

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value for the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i] ? leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++] : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            return hashes[totalHashes - 1];
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    function _hashPair(bytes32 a, bytes32 b) private pure returns (bytes32) {
        return a < b ? _efficientHash(a, b) : _efficientHash(b, a);
    }

    function _efficientHash(bytes32 a, bytes32 b) private pure returns (bytes32 value) {
        /// @solidity memory-safe-assembly
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}


// File @openzeppelin/contracts/security/ReentrancyGuard.sol@v4.7.0

// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @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 making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}


// File contracts/IFFundable.sol

pragma solidity 0.8.9;




/**
  @title Abstract contract providing funder related functions in a sale
  @notice To be implemented by IFSale.
 */
abstract contract IFFundable is Ownable, ReentrancyGuard {
    using SafeERC20 for ERC20;

    // --- CONSTANTS

    // number of decimals of sale price
    uint64 constant SALE_PRICE_DECIMALS = 10**18;
    uint64 private constant ONE_HOUR = 3600;
    uint64 private constant ONE_YEAR = 31556926;
    uint64 private constant FIVE_YEARS = 157784630;
    uint64 private constant TEN_YEARS = 315742060;

    // --- OPERATOR ADDRESSES

    address public funder;
    // optional casher (settable by owner)
    address public casher;

    // --- SALE INFO

    // start timestamp when sale is active (inclusive)
    uint256 public immutable startTime;
    // end timestamp when sale is active (inclusive)
    uint256 public immutable endTime;
    // payment token
    ERC20 private immutable paymentToken;
    // sale token
    ERC20 private immutable saleToken;
    // withdraw/cash delay timestamp (inclusive)
    uint24 public withdrawDelay;
    // tracks whether user has already successfully withdrawn
    mapping(address => bool) public hasWithdrawn;

    // --- STATS

    // amount of sale token to sell
    uint256 public saleAmount;
    // tracks whether sale has been cashed
    bool public hasCashed;
    // total payment received for sale
    uint256 public totalPaymentReceived;
    // counter of unique withdrawers (doesn't count "cash"ing)
    uint32 public withdrawerCount;

    // --- CONSTRUCTOR

    constructor(
        ERC20 _paymentToken,
        ERC20 _saleToken,
        uint256 _startTime,
        uint256 _endTime,
        address _funder
    ) {
        // saleToken shouldn't be the same as paymentToken
        require(_saleToken != _paymentToken, 'saleToken = paymentToken');
        // when salePrice != 0, paymentToken and maxTotalPayment shouldn't be 0
        // sale token cannot be 0
        require(address(_saleToken) != address(0), '0x0 saleToken');
        // start timestamp must be in future
        require(block.timestamp < _startTime, 'start timestamp too early');
        require(_startTime - ONE_YEAR < block.timestamp, 'start time has to be within 1 year');
        // end timestamp must be after start timestamp
        require(_startTime < _endTime, 'end timestamp must be after start timestamp');
        require(_endTime - TEN_YEARS < _startTime, 'end time has to be within 10 years');

        require(_funder != address(0), '0x0 funder');
        funder = _funder;

        paymentToken = _paymentToken; // can be 0 (for giveaway)
        saleToken = _saleToken;
        startTime = _startTime;
        endTime = _endTime;
    }

    // --- MODIFIERS

    // Throws if called by any account other than the funder.
    modifier onlyFunder() {
        require(_msgSender() == funder, 'caller not funder');
        _;
    }

    // Throws if called by any account other than the casher.
    modifier onlyCasherOrOwner() {
        require(
            _msgSender() == casher || _msgSender() == owner(),
            'caller not casher or owner'
        );
        _;
    }

    // Throws if called during or after sale
    modifier onlyBeforeSale() {
        require(block.timestamp < startTime, 'sale already started');
        _;
    }

    // Throws if called outside of claim period
    modifier onlyAfterSale {
        require(block.timestamp > endTime + withdrawDelay, "can't withdraw before claim is started");
        _;
    }

    // Throws if called outside of sale period
    modifier onlyDuringSale {
        require(startTime <= block.timestamp, 'sale has not begun');
        require(block.timestamp <= endTime, 'sale over');
        _;
    }

    // --- EVENTS

    event SetCasher(address indexed casher);
    event SetFunder(address indexed funder);
    event Fund(address indexed sender, uint256 amount);
    event SetWithdrawDelay(uint24 indexed withdrawDelay);
    event Cash(
        address indexed sender,
        uint256 paymentTokenBalance,
        uint256 saleTokenBalance
    );
    event EmergencyTokenRetrieve(address indexed sender, uint256 amount);
    event Withdraw(address indexed sender, uint256 amount);

    // --- SETTER

    // Function for owner to set an optional, separate casher
    function setCasher(address _casher) public onlyOwner {
        casher = _casher;

        emit SetCasher(_casher);
    }

    function setFunder(address _funder) public onlyOwner {
        require(_funder != address(0), '0x0 funder');
        funder = _funder;

        emit SetFunder(_funder);
    }

    // Function for owner to set a withdraw delay
    function setWithdrawDelay(uint24 _withdrawDelay) virtual public onlyOwner onlyBeforeSale{
        require(_withdrawDelay < FIVE_YEARS, "withdrawDelay has to be within 5 years");
        withdrawDelay = _withdrawDelay;

        emit SetWithdrawDelay(_withdrawDelay);
    }

    // --- FUNDER'S LOGIC

    // Virtual function to be implemented by IFSale.
    //   To calculate the amount of cashable tokens.
    function getSaleTokensSold() internal virtual returns (uint256 amount);

    // Function for funding sale with sale token (called by project team)
    function fund(uint256 amount) public onlyFunder onlyBeforeSale{
        // transfer specified amount from funder to this contract
        saleToken.safeTransferFrom(_msgSender(), address(this), amount);

        // increase tracked sale amount
        saleAmount += amount;

        emit Fund(_msgSender(), amount);
    }


    // Function for funder to cash in payment token and unsold sale token
    function cash() external onlyCasherOrOwner onlyAfterSale {
        // prevent repeat cash
        require(!hasCashed, 'already cashed');

        hasCashed = true;

        // get amount of payment token received
        uint256 paymentTokenBal = paymentToken.balanceOf(address(this));

        // transfer all
        paymentToken.safeTransfer(_msgSender(), paymentTokenBal);

        // get amount of sale token on contract
        uint256 saleTokenBal = saleToken.balanceOf(address(this));

        // get amount of sold token
        uint256 totalTokensSold = getSaleTokensSold();

        // get principal (whichever is bigger between sale amount or amount on contract)
        uint256 principal = saleAmount < saleTokenBal
            ? saleTokenBal
            : saleAmount;

        // calculate amount of unsold sale token
        uint256 amountUnsold = principal - totalTokensSold;

        // transfer unsold
        saleToken.safeTransfer(_msgSender(), amountUnsold);

        emit Cash(_msgSender(), paymentTokenBal, amountUnsold);
    }

    function cashPaymentToken(uint256 amount) external onlyCasherOrOwner {
        // Get amount of payment token received
        uint256 paymentTokenBal = paymentToken.balanceOf(address(this));

        // Ensure there's enough payment tokens to cash
        require(paymentTokenBal >= amount, "No enough payment tokens to cash");

        // Transfer payment tokens to the caller
        paymentToken.safeTransfer(_msgSender(), amount);

        // Emit an event for this cashing
        emit Cash(_msgSender(), amount, 0);
    }


    // Retrieve tokens erroneously sent in to this address
    function emergencyTokenRetrieve(address token) public onlyOwner onlyAfterSale {
        // cannot be sale tokens
        require(token != address(saleToken));

        uint256 tokenBalance = ERC20(token).balanceOf(address(this));

        // transfer all
        ERC20(token).safeTransfer(_msgSender(), tokenBalance);

        emit EmergencyTokenRetrieve(_msgSender(), tokenBalance);
    }

    // Function for withdrawing purchased sale token after sale end
    function withdraw() virtual public nonReentrant {}   

    function _withdraw(uint256 saleTokenOwed) virtual internal {
        require(saleTokenOwed != 0, 'no token to be withdrawn');

        // increment withdrawer count
        if (!hasWithdrawn[_msgSender()]) {
            withdrawerCount += 1;
            // set withdrawn to true
            hasWithdrawn[_msgSender()] = true;
        }

        saleToken.safeTransfer(_msgSender(), saleTokenOwed);

        emit Withdraw(_msgSender(), saleTokenOwed);
    }
}


// File contracts/IFPurchasable.sol

pragma solidity 0.8.9;




/**
  @dev Abstract contract containing sale logics.
        To be implemented by IFSale.
  @notice Include virtual functions for regular and whitelisted purchase
  @notice Include virtual functions for whitelisted free token giveaway
  @notice Include sale state variables
  @notice Implemneted sale state variables changes on purchase and withdraw
 */
abstract contract IFPurchasable is Ownable, ReentrancyGuard {
    using SafeERC20 for ERC20;

    // --- SALE INFO

    // payment token
    ERC20 public immutable paymentToken;
    // price of the sale token
    uint256 public salePrice;
    // max for payment token amount
    uint256 public maxTotalPayment;
    // current purchased amount
    uint256 public saleTokenPurchased;
    // optional min for payment token amount
    uint256 public minTotalPayment;
    // optional max for total purchasable amount, default is 0 if there's no limit
    // assuming all users buy the token on the same price
    uint256 public maxTotalPurchasable;
    // halt purchase if true. default is false
    bool public isPurchaseHalted = false;


    // --- USER INFO

    // tracks amount purchased by each address
    // user address => purchased amount
    mapping(address => uint256) public paymentReceived;
    // track amount purchased with code by each address
    // user address => purchased amount with code
    mapping(address => uint256) public paymentReceivedWithCode;
    // track amount purchased with each code by each address
    // user address => code => purchased amount with each code
    mapping(address => mapping(string => uint256)) public paymentReceivedWithEachCode;
    // track promo code used by each address
    // user address => promo codes
    mapping(address => string[]) public promoCodesPerUser;
    // track if a promo code is used by an address
    // user address => promo code => bool
    mapping(address => mapping(string => bool)) public hasUsedCode;

    // -- PROMO CODE

    // all promo codes  
    string[] public codes;
    // track if a promo code is stored
    mapping(string => bool) isCodeStored;
    // amount received per promo code
    mapping(string => uint256) public amountPerCode;
    // unique use per promo code
    mapping(string => uint256) public uniqueUsePerCode;
    // max amount of promo code per user
    uint256 public maxPromoCodePerUser = 50;


    // --- STAT

    // counter of unique purchasers
    uint32 public purchaserCount;

    event Purchase(address indexed sender, uint256 paymentAmount);
    event PurchaseWithCode(address indexed sender, uint256 paymentAmount, string code);
    event SetMinTotalPayment(uint256 indexed minTotalPayment);
    event SetMaxTotalPurchasable(uint256 indexed _maxTotalPurchasable);
    event SetIsPurchaseHalted(bool indexed isPurchaseHalted);

    constructor(
        ERC20 _paymentToken,
        uint256 _salePrice,
        uint256 _maxTotalPayment
    ) {
        require(
            _salePrice == 0 ||
                (_salePrice != 0 &&
                    address(_paymentToken) != address(0) &&
                    _maxTotalPayment >= _salePrice),
            'paymentToken or maxTotalPayment should not be 0 when salePrice is not 0'
        );
        salePrice = _salePrice; // can be 0 (for giveaway)
        paymentToken = _paymentToken; // can be 0 (for giveaway)
        maxTotalPayment = _maxTotalPayment; // can be 0 (for giveaway)
    }


    function setIsPurchaseHalted(bool _isPurchaseHalted) public onlyOwner {
        isPurchaseHalted = _isPurchaseHalted;

        emit SetIsPurchaseHalted(_isPurchaseHalted);
    }

    // Function for owner to set an optional, minTotalPayment
    function setMinTotalPayment(uint256 _minTotalPayment) public onlyOwner {
        minTotalPayment = _minTotalPayment;

        emit SetMinTotalPayment(_minTotalPayment);
    }


    // Function for owner to set an optional, maxTotalPurchasable
    // The amount is calculated on salePrice. 
    function setMaxTotalPurchasable(uint256 _maxTotalPurchasable) virtual public onlyOwner {
        maxTotalPurchasable = _maxTotalPurchasable * salePrice;

        require(maxTotalPurchasable >= saleTokenPurchased, 'Max purchasable should not be lower than the amount of token purchased');

        emit SetMaxTotalPurchasable(_maxTotalPurchasable);
    }

    // --- PURCHASE

    function purchase(uint256 paymentAmount) virtual public {}

    // Internal function for making purchase
    // Used by public functions `purchase`
    function _purchase(uint256 paymentAmount, uint256 remaining) virtual internal nonReentrant {
        require(!isPurchaseHalted, 'purchase is halted');
        require(salePrice > 0, 'sale price is zero');
        // amount must be greater than minTotalPayment
        // by default, minTotalPayment is 0 unless otherwise set
        require(paymentAmount >= minTotalPayment, 'amount below min');

        // payment must not exceed remaining
        require(paymentAmount <= remaining, 'exceeds max payment');
        require(paymentAmount != 0, 'zero payment amount');

        saleTokenPurchased += paymentAmount;
        require(maxTotalPurchasable == 0 || maxTotalPurchasable >= saleTokenPurchased, 'exceed max purchasable');

        // if user is paying for the first time to this contract, increase counter
        if (paymentReceived[_msgSender()] == 0) purchaserCount += 1;

        // increase payment received amount
        paymentReceived[_msgSender()] += paymentAmount;

        // transfer specified amount from user to this contract
        paymentToken.safeTransferFrom(_msgSender(), address(this), paymentAmount);

        emit Purchase(_msgSender(), paymentAmount);
    }

    function _purchaseWithCode(uint256 paymentAmount, uint256 remaining, string memory code) virtual internal {
        // check if code is not empty
        require(bytes(code).length > 0, 'code is empty');
        // check if code is too long
        require(bytes(code).length <= 64, 'code is too long');

        // This needs to be before anything else
        // ===
        _purchase(paymentAmount, remaining);
        // ====

        if (!isCodeStored[code]) {
            isCodeStored[code] = true;
            codes.push(code);
        }

        if (!hasUsedCode[_msgSender()][code]) {
            require(promoCodesPerUser[_msgSender()].length < maxPromoCodePerUser, 'max promo code per user reached');
            hasUsedCode[_msgSender()][code] = true;
            promoCodesPerUser[_msgSender()].push(code);
        }

        amountPerCode[code] += paymentAmount;

        if (paymentReceivedWithEachCode[_msgSender()][code] == 0) {
            uniqueUsePerCode[code] += 1;
        }
        paymentReceivedWithCode[_msgSender()] += paymentAmount;
        paymentReceivedWithEachCode[_msgSender()][code] += paymentAmount;

        emit PurchaseWithCode(_msgSender(), paymentAmount, code);
    }
}


// File @openzeppelin/contracts/utils/math/Math.sol@v4.7.0

// OpenZeppelin Contracts (last updated v4.7.0) (utils/math/Math.sol)

pragma solidity ^0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    enum Rounding {
        Down, // Toward negative infinity
        Up, // Toward infinity
        Zero // Toward zero
    }

    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow.
        return (a & b) + (a ^ b) / 2;
    }

    /**
     * @dev Returns the ceiling of the division of two numbers.
     *
     * This differs from standard division with `/` in that it rounds up instead
     * of rounding down.
     */
    function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b - 1) / b can overflow on addition, so we distribute.
        return a == 0 ? 0 : (a - 1) / b + 1;
    }

    /**
     * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
     * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
     * with further edits by Uniswap Labs also under MIT license.
     */
    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 denominator
    ) internal pure returns (uint256 result) {
        unchecked {
            // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
            // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
            // variables such that product = prod1 * 2^256 + prod0.
            uint256 prod0; // Least significant 256 bits of the product
            uint256 prod1; // Most significant 256 bits of the product
            assembly {
                let mm := mulmod(x, y, not(0))
                prod0 := mul(x, y)
                prod1 := sub(sub(mm, prod0), lt(mm, prod0))
            }

            // Handle non-overflow cases, 256 by 256 division.
            if (prod1 == 0) {
                return prod0 / denominator;
            }

            // Make sure the result is less than 2^256. Also prevents denominator == 0.
            require(denominator > prod1);

            ///////////////////////////////////////////////
            // 512 by 256 division.
            ///////////////////////////////////////////////

            // Make division exact by subtracting the remainder from [prod1 prod0].
            uint256 remainder;
            assembly {
                // Compute remainder using mulmod.
                remainder := mulmod(x, y, denominator)

                // Subtract 256 bit number from 512 bit number.
                prod1 := sub(prod1, gt(remainder, prod0))
                prod0 := sub(prod0, remainder)
            }

            // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
            // See https://cs.stackexchange.com/q/138556/92363.

            // Does not overflow because the denominator cannot be zero at this stage in the function.
            uint256 twos = denominator & (~denominator + 1);
            assembly {
                // Divide denominator by twos.
                denominator := div(denominator, twos)

                // Divide [prod1 prod0] by twos.
                prod0 := div(prod0, twos)

                // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                twos := add(div(sub(0, twos), twos), 1)
            }

            // Shift in bits from prod1 into prod0.
            prod0 |= prod1 * twos;

            // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
            // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
            // four bits. That is, denominator * inv = 1 mod 2^4.
            uint256 inverse = (3 * denominator) ^ 2;

            // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
            // in modular arithmetic, doubling the correct bits in each step.
            inverse *= 2 - denominator * inverse; // inverse mod 2^8
            inverse *= 2 - denominator * inverse; // inverse mod 2^16
            inverse *= 2 - denominator * inverse; // inverse mod 2^32
            inverse *= 2 - denominator * inverse; // inverse mod 2^64
            inverse *= 2 - denominator * inverse; // inverse mod 2^128
            inverse *= 2 - denominator * inverse; // inverse mod 2^256

            // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
            // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
            // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
            // is no longer required.
            result = prod0 * inverse;
            return result;
        }
    }

    /**
     * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
     */
    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 denominator,
        Rounding rounding
    ) internal pure returns (uint256) {
        uint256 result = mulDiv(x, y, denominator);
        if (rounding == Rounding.Up && mulmod(x, y, denominator) > 0) {
            result += 1;
        }
        return result;
    }

    /**
     * @dev Returns the square root of a number. It the number is not a perfect square, the value is rounded down.
     *
     * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
     */
    function sqrt(uint256 a) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }

        // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
        // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
        // `msb(a) <= a < 2*msb(a)`.
        // We also know that `k`, the position of the most significant bit, is such that `msb(a) = 2**k`.
        // This gives `2**k < a <= 2**(k+1)` → `2**(k/2) <= sqrt(a) < 2 ** (k/2+1)`.
        // Using an algorithm similar to the msb conmputation, we are able to compute `result = 2**(k/2)` which is a
        // good first aproximation of `sqrt(a)` with at least 1 correct bit.
        uint256 result = 1;
        uint256 x = a;
        if (x >> 128 > 0) {
            x >>= 128;
            result <<= 64;
        }
        if (x >> 64 > 0) {
            x >>= 64;
            result <<= 32;
        }
        if (x >> 32 > 0) {
            x >>= 32;
            result <<= 16;
        }
        if (x >> 16 > 0) {
            x >>= 16;
            result <<= 8;
        }
        if (x >> 8 > 0) {
            x >>= 8;
            result <<= 4;
        }
        if (x >> 4 > 0) {
            x >>= 4;
            result <<= 2;
        }
        if (x >> 2 > 0) {
            result <<= 1;
        }

        // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
        // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
        // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
        // into the expected uint128 result.
        unchecked {
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            return min(result, a / result);
        }
    }

    /**
     * @notice Calculates sqrt(a), following the selected rounding direction.
     */
    function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
        uint256 result = sqrt(a);
        if (rounding == Rounding.Up && result * result < a) {
            result += 1;
        }
        return result;
    }
}


// File contracts/IFVestable.sol

pragma solidity 0.8.9;


/**
  @dev Abstract contract containing vesting logics.
        To be implemented by IFSale.
  @notice There are two vesting types: linear and cliff
  @notice Can only set one vesting type
  @notice Once one of the vesting type is set, another one will be reset
  @notice Linear vesting unlocks tokens at a linear scale. Calculated by vesting end time
  @notice Cliff vesting unlocks tokens at a series of specific time. According to cliff period
 */
abstract contract IFVestable is Ownable {
    uint64 private constant TEN_YEARS = 315742060;

    // --- VESTING

    // Allow vesting to be editable after sale
    bool public vestingEditableOverride;

    // withdraw/cash delay timestamp (inclusive)
    uint256 public withdrawTime;
    // the most recent time the user claimed the saleToken
    mapping(address => uint256) public latestClaimTime;

    event OptInBuyback(address indexed user);

    // --- LINEAR VESTING

    // the time where the user can take all of the vested saleToken
    uint256 public linearVestingEndTime;
    event SetLinearVestingEndTime(uint256 indexed linearVestingEndTime);

    // --- CLIFF VESTING

    // store how many percentage of the token can be claimed at a certain cliff date
    struct Cliff {
        // the date when the percentage of token can be claimed
        uint256 claimTime;
        // the percentage token that can be claimed
        uint8 pct;
    }
    // cliff vesting time and percentage
    Cliff[] public cliffPeriod;
    event SetCliffVestingPeriod(Cliff[] indexed cliffPeriod);

    function getCliffPeriod() public view returns (Cliff[] memory){
        return cliffPeriod;
    }

    // --- CONSTRUCTOR

    constructor(
        uint256 _withdrawTime
    ) {
        // withdrawal delay is by default 0
        // it can be set using setWithdrawDelay
        withdrawTime = _withdrawTime;
    }

    // --- SETTER

    function setVestingEditable(bool _vestingEditableOverride) public onlyOwner {
        vestingEditableOverride = _vestingEditableOverride;
    }

    function setWithdrawTime(uint256 _withdrawTime) internal {
        withdrawTime = _withdrawTime;
    }

    // Function for owner to set a vesting end time
    function setLinearVestingEndTime(uint256 _linearVestingEndTime) virtual public onlyOwner {
        require(vestingEditableOverride || block.timestamp < withdrawTime, "Can't edit vesting after sale");
        require(_linearVestingEndTime > withdrawTime, "vesting end time has to be after withdrawal start time");
        require(withdrawTime > _linearVestingEndTime - TEN_YEARS, "vesting end time has to be within 10 years");
        linearVestingEndTime = _linearVestingEndTime;

        // unset cliff vesting
        delete cliffPeriod;
        emit SetLinearVestingEndTime(_linearVestingEndTime);
    }

    function setCliffPeriod(uint256[] calldata claimTimes, uint8[] calldata pct) virtual public onlyOwner {
        require(vestingEditableOverride || block.timestamp < withdrawTime, "Can't edit vesting after sale");
        require(claimTimes.length == pct.length, "dates and pct doesn't match");
        require(claimTimes.length > 0, "input is empty");
        require(claimTimes.length <= 100, "input length cannot exceed 100");

        // clear the past entry
        delete cliffPeriod;

        uint256 maxDate;
        uint8 totalPct;
        require(claimTimes[0] > withdrawTime, "first claim time is before end time + withdraw delay");
        for (uint i = 0; i < claimTimes.length; i++) {
            require(maxDate < claimTimes[i], "dates not in ascending order");
            maxDate = claimTimes[i];
            totalPct += pct[i];
            cliffPeriod.push(Cliff(claimTimes[i], pct[i]));
        }
        require(withdrawTime > maxDate - TEN_YEARS, "vesting end time has to be within 10 years");
        // pct is the release percentage, with a precision of 1%. Thus, the sum of all elements of pct must be equal to 100
        require(totalPct == 100, "total input percentage doesn't equal to 100");

        // unset linear vesting
        linearVestingEndTime = 0;
    }

    // --- VESTING LOGIC

    /**
      @notice Get the amount of token unlocked
      @param totalPurchased Total tokens purchased
      @param user Address of the user claiming the tokens
     */
    function getUnlockedToken(uint256 totalPurchased, uint256 claimable, address user) virtual public view returns (uint256) {
        // linear vesting
        if (linearVestingEndTime > block.timestamp) {
            // current claimable = total purchased * (now - last claimed time) / (total vesting time)
            return totalPurchased * (block.timestamp - Math.max(latestClaimTime[user], withdrawTime)) / (linearVestingEndTime - withdrawTime);
        }

        // cliff vesting
        uint256 cliffPeriodLength = cliffPeriod.length;
        if (cliffPeriodLength != 0 && (cliffPeriod[cliffPeriodLength - 1].claimTime > block.timestamp)) {
            uint8 claimablePct;
            for (uint8 i; i < cliffPeriodLength; i++) {
                // if the cliff timestamp has been passed, add the claimable percentage
                if (cliffPeriod[i].claimTime > block.timestamp) { break; }
                if (latestClaimTime[user] < cliffPeriod[i].claimTime) {
                    claimablePct += cliffPeriod[i].pct;
                }
            }
            // current claimable = total * claimiable percentage
            if (claimablePct == 0) {
                return 0;
            }
            return totalPurchased * claimablePct / 100;
        }

        // When vesting end, claim all of the remaining tokens.
        // Since all of the above calculations return a lower rounded number,
        // users will get a little bit less tokens.
        // Keeping track and returning the total remaining claimable makes sure the users will get the exact amount.
        return claimable;
    }
}


// File contracts/IFWhitelistable.sol

pragma solidity 0.8.9;


abstract contract IFWhitelistable is Ownable, ReentrancyGuard {
    // optional whitelist setter (settable by owner)
    address public whitelistSetter;

    // whitelist merkle root; if not set, then sale is open to everyone that has allocation
    bytes32 public whitelistRootHash;

    event SetWhitelistSetter(address indexed whitelistSetter);
    event SetWhitelist(bytes32 indexed whitelistRootHash);

    constructor() {
        whitelistSetter = _msgSender();
    }


    // Throws if called by any account other than the whitelist setter.
    modifier onlyWhitelistSetterOrOwner() {
        require(
            _msgSender() == whitelistSetter || _msgSender() == owner(),
            'caller not whitelist setter or owner'
        );
        _;
    }

    // Function for owner to set an optional, separate whitelist setter
    function setWhitelistSetter(address _whitelistSetter) public onlyOwner {
        whitelistSetter = _whitelistSetter;

        emit SetWhitelistSetter(_whitelistSetter);
    }

    // Function for owner or whitelist setter to set a whitelist; if not set, then everyone allowed
    function setWhitelist(bytes32 _whitelistRootHash)
        public
        onlyWhitelistSetterOrOwner
    {
        whitelistRootHash = _whitelistRootHash;

        emit SetWhitelist(_whitelistRootHash);
    }

    // purchase function when there is a whitelist
    function whitelistedPurchase(uint256 paymentAmount, bytes32[] calldata merkleProof) virtual public {}

    function withdrawGiveaway(bytes32[] calldata merkleProof) virtual public nonReentrant {}
}


// File contracts/IFSale.sol

pragma solidity 0.8.9;







/**
  @dev Vanilla Sale contract compositing vesting, funding, and whitelisting functions.
  @notice Features:
  @notice 1. Funder related actions like fund and cash
  @notice 2. Regular and whitelisted purchase
  @notice 3. Whitelisted free token giveaway
  @notice 4. Vest tokens in linear or cliff mode
 */
contract IFSale is IFPurchasable, IFVestable, IFFundable, IFWhitelistable {
    // tracks amount of tokens owed to each address
    mapping(address => uint256) public claimable;
    // tracks amount of tokens purchased by each address
    mapping(address => uint256) public totalPurchased;
    // flag to enable integer sale
    bool public isIntegerSale = false;

    // --- CONSTRUCTOR

    constructor(
        address _funder,
        uint256 _salePrice,
        ERC20 _paymentToken,
        ERC20 _saleToken,
        uint256 _startTime,
        uint256 _endTime,
        uint256 _maxTotalPayment
    ) 
        IFPurchasable(_paymentToken, _salePrice, _maxTotalPayment)
        IFVestable(_endTime)
        IFFundable(_paymentToken, _saleToken, _startTime, _endTime, _funder)
        IFWhitelistable()
    {}

    // --- SETTERS

    function setWithdrawDelay(uint24 _withdrawDelay) override public onlyOwner onlyBeforeSale {
        setWithdrawTime(endTime + _withdrawDelay);
        super.setWithdrawDelay(_withdrawDelay);
    }

    function setLinearVestingEndTime(uint256 _vestingEndTime) override public onlyOwner onlyBeforeSale {
        super.setLinearVestingEndTime(_vestingEndTime);
    }

    function setCliffPeriod(uint256[] calldata claimTimes, uint8[] calldata pct) override public onlyOwner onlyBeforeSale {
        super.setCliffPeriod(claimTimes, pct);
    }

    function setIsIntegerSale(bool _isIntegerSale) public onlyOwner onlyBeforeSale {
        isIntegerSale = _isIntegerSale;
    }

    // --- PURCHASE

    function purchase(uint256 paymentAmount) virtual override public onlyDuringSale {
        require(whitelistRootHash == 0, 'use whitelistedPurchase');
        _purchase(paymentAmount, maxTotalPayment);
    }

    // purchase function when there is a whitelist
    function whitelistedPurchase(
        uint256 paymentAmount,
        bytes32[] calldata merkleProof
    ) virtual override public onlyDuringSale {
        // the user has to be whitelisted
        require(checkWhitelist(_msgSender(), merkleProof), 'proof invalid');
        _purchase(paymentAmount, maxTotalPayment);
    }

    // --- WITHDRAW

    function withdraw() virtual override public onlyAfterSale nonReentrant {
        // must not be a zero price sale
        require(salePrice != 0, 'use withdrawGiveaway');

        address user = _msgSender();

        uint256 tokenOwed = getCurrentClaimableToken(user);
        require(tokenOwed != 0, 'no token to be withdrawn');
        // send token and update states
        _withdraw(tokenOwed);
    }   

    // Function to withdraw (redeem) tokens from a zero cost "giveaway" sale
    function withdrawGiveaway(bytes32[] calldata merkleProof) virtual override public onlyAfterSale nonReentrant
    {
        revert("Not implemented");
    }

    // --- UPDATE SALE STATES

    function _purchase(uint256 paymentAmount, uint256 remaining) override internal {
        if (isIntegerSale) {
            require(isIntegerPayment(paymentAmount), 'can only buy integer amount of sale tokens');
        }
        totalPaymentReceived += paymentAmount;
        super._purchase(paymentAmount, remaining);
        // Update vesting variables
        uint256 tokenPurchased = (paymentReceived[_msgSender()] * SALE_PRICE_DECIMALS) / salePrice;
        totalPurchased[_msgSender()] = tokenPurchased;
        claimable[_msgSender()] = tokenPurchased;
    }

    function _withdraw(uint256 tokenOwed) override internal {
        // Update vesting variables
        latestClaimTime[_msgSender()] = block.timestamp;
        claimable[_msgSender()] -= tokenOwed;
        super._withdraw(tokenOwed);
    }

    // --- HELPER FUNCTIONS

    function getSaleTokensSold() override internal view returns (uint256 amount) {
        // if salePrice is 0, no tokens will be sold
        if (salePrice == 0) {
            return 0;
        } else {
            return totalPaymentReceived * SALE_PRICE_DECIMALS / salePrice;
        }
    }

    // A helper function to get the amount of unlocked token by providing user's address
    function getCurrentClaimableToken (address user) public view returns (uint256) {
        return getUnlockedToken(totalPurchased[user], claimable[user], user);
    }

    // Returns true if user is on whitelist, otherwise false
    function checkWhitelist(address user, bytes32[] calldata merkleProof) virtual public view returns (bool)
    {
        // compute merkle leaf from input
        bytes32 leaf = keccak256(abi.encodePacked(user));

        // verify merkle proof
        return MerkleProof.verify(merkleProof, whitelistRootHash, leaf);
    }

    // a function to check if the payment amount can buy integer amount of sale tokens, accounting the token decimals
    function isIntegerPayment(uint256 paymentAmount) public view returns (bool) {
        return (
            // has to at least purchase 1 token
            paymentAmount % salePrice == 0
            && paymentAmount >= salePrice
        );
    }

    // Override the renounceOwnership function to disable it
    function renounceOwnership() public pure override{
        revert("ownership renunciation is disabled");
    }

}


// File contracts/IFFixedSaleV12.sol

pragma solidity 0.8.9;


/**
  @title Sale contract with user's allocation stored in merkle root
  @notice Regular purchase from IFSale is disabled here
  @notice Apart from merkle proof, users or the frontend has to supply allocation amount for verification
  @notice That means functions having `merkleProof` as param will also need `allocation`
 */
contract IFFixedSaleV12 is IFSale {
    // --- CONSTRUCTOR

    constructor(
        uint256 _salePrice,
        address _funder,
        ERC20 _paymentToken,
        ERC20 _saleToken,
        uint256 _startTime,
        uint256 _endTime,
        uint256 _maxTotalPayment
    ) 
        IFSale(
            _funder,
            _salePrice,
            _paymentToken,
            _saleToken,
            _startTime,
            _endTime,
            _maxTotalPayment
        )
    {}

    bool public isVestedGiveaway = false;

    // allocation when the user is not whitelisted
    // note that any user can get publicAllocation regardless of their whitelisted allocation
    uint256 public publicAllocation = 0;

    // --- SETTER FUNCTIONS
    function setVestedGiveaway(bool _isVestedGiveaway) public onlyOwner onlyBeforeSale {
        isVestedGiveaway = _isVestedGiveaway;
    }

    function setPublicAllocation(uint256 _publicAllocation) public onlyWhitelistSetterOrOwner onlyBeforeSale {
        publicAllocation = _publicAllocation;
    }

    function setMaxTotalPurchasable(uint256 _maxTotalPurchasable) override public onlyWhitelistSetterOrOwner {
        maxTotalPurchasable = _maxTotalPurchasable * salePrice;

        require(maxTotalPurchasable >= saleTokenPurchased, 'Max purchasable should not be lower than the amount of token purchased');

        emit SetMaxTotalPurchasable(_maxTotalPurchasable);
    }

    // --- DISABLED FUNCTIONS

    function purchase(uint256) virtual override public {
        revert("Use whitelistedPurchase(uint256 paymentAmount, bytes32[] calldata merkleProof, uint256 allocation)");
    }

    function whitelistedPurchase(uint256, bytes32[] calldata) override public pure {
        revert("Use whitelistedPurchase(uint256 paymentAmount, bytes32[] calldata merkleProof, uint256 allocation)");
    }

    function withdrawGiveaway(bytes32[] calldata) override public pure {
        revert("Use withdrawGiveaway(bytes32[] calldata merkleProof, uint256 allocation)");
    }

    // --- WHITELISTED ACTIONS

    // purchase with code function when there is a whitelist
    function whitelistedPurchaseWithCode(
        uint256 paymentAmount,
        bytes32[] calldata merkleProof,
        uint256 _allocation,
        string calldata code
    ) public onlyDuringSale {
        uint256 allocation = publicAllocation;
        if (merkleProof.length > 0) {
            // require that user is whitelisted by checking proof
            require(checkWhitelist(_msgSender(), merkleProof, _allocation), 'proof invalid');
            if (_allocation > publicAllocation) {
                allocation = _allocation;
            }
        }

        uint256 remaining = getMaxPayment(_msgSender(), allocation);
        _purchaseWithCode(paymentAmount, remaining, code);
    }

    // purchase function when there is a whitelist
    function whitelistedPurchase(
        uint256 paymentAmount,
        bytes32[] calldata merkleProof,
        uint256 _allocation
    ) public onlyDuringSale {
        uint256 allocation = publicAllocation;
        if (merkleProof.length > 0) {
            // require that user is whitelisted by checking proof
            require(checkWhitelist(_msgSender(), merkleProof, _allocation), 'proof invalid');
            if (_allocation > publicAllocation) {
                allocation = _allocation;
            }
        }

        uint256 remaining = getMaxPayment(_msgSender(), allocation);
        _purchase(paymentAmount, remaining);
    }

    // Function to withdraw (redeem) tokens from a zero cost "giveaway" sale
    function withdrawGiveaway(bytes32[] calldata merkleProof, uint256 allocation)
        external
        nonReentrant
        onlyAfterSale
    {
        address user = _msgSender();
        // not vested giveaway
        require(isVestedGiveaway == false, 'use withdrawGiveawayVested');
        // must be a zero price sale
        require(salePrice == 0, 'not a giveaway');
        // can withdraw only once
        require(hasWithdrawn[user] == false, 'already withdrawn');
        // require that user is whitelisted by checking proof
        require(checkWhitelist(user, merkleProof, allocation), 'proof invalid');

        uint256 saleTokenOwed = 0;
        // initialize claimable before the first time of withdrawal
        if (!hasWithdrawn[user]) {
            // each participant in the zero cost "giveaway" gets a flat amount of sale token
            saleTokenOwed = allocation;
            claimable[user] = allocation;
            totalPurchased[user] = allocation;
        }

        // sale token owed must be greater than 0
        require(saleTokenOwed != 0, 'withdraw giveaway amount 0');

        // send token and update states
        _withdraw(saleTokenOwed);
    }

    // Function to withdraw (redeem) tokens from a zero cost "giveaway" sale
    function withdrawGiveawayVested(bytes32[] calldata merkleProof, uint256 allocation)
        external
        nonReentrant
        onlyAfterSale
    {
        address user = _msgSender();

        // not vested giveaway
        require(isVestedGiveaway == true, 'use withdrawGiveaway');
        // must be a zero price sale
        require(salePrice == 0, 'not a giveaway');
        // require that user is whitelisted by checking proof
        require(checkWhitelist(user, merkleProof, allocation), 'proof invalid');

        // initialize claimable before the first time of withdrawal
        if (!hasWithdrawn[user]) {
            claimable[user] = allocation;
            totalPurchased[user] = allocation;
        }

        uint256 tokenOwed = getCurrentClaimableToken(user);

        // sale token owed must be greater than 0
        require(tokenOwed != 0, 'withdraw giveaway amount 0');

        // send token and update states
        _withdraw(tokenOwed);
    }

    // --- HELPER FUNCTIONS

    // Returns true if user's allocation matches the one in merkle root, otherwise false
    function checkWhitelist(address user, bytes32[] calldata merkleProof, uint256 allocation)
        public
        view
        returns (bool)
    {
        // compute merkle leaf from input
        bytes32 leaf = keccak256(abi.encodePacked(user, allocation));

        // verify merkle proof
        return MerkleProof.verify(merkleProof, whitelistRootHash, leaf);
    }

    // @dev get max payment from allocation
    function getMaxPayment(address user, uint256 allocation) public view returns (uint256) {
        // get the maximum total payment for a user
        uint256 max = (salePrice * allocation) / SALE_PRICE_DECIMALS;
        if (maxTotalPayment < max) {
            max = maxTotalPayment;
        }

        // calculate and return remaining
        return max - paymentReceived[user];
    }
}

{
  "compilationTarget": {
    "IFFixedSaleV12.sol": "IFFixedSaleV12"
  },
  "evmVersion": "london",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}