// File: contracts/staking.sol




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

import "staking/contracts/StakingERC20.sol";

/**
 * @dev Handles staking erc20 tokens
*/
contract Staking is StakingERC20 {

    constructor(
        IERC20 token,
        IERC20 rewardToken
    ) StakingERC20(token, rewardToken, 9) {

    }
}
// File: staking/contracts/StakingERC20.sol



// SPDX-License-Identifier: NONE
pragma solidity ^0.8.0;

import '@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol';
import "./Distribute.sol";
import "./interfaces/IERC900.sol";

/**
 * An IERC900 staking contract
 */
contract StakingERC20 is IERC900  {
    using SafeERC20 for IERC20;

    /// @dev handle to access ERC20 token token contract to make transfers
    IERC20 private _token;
    Distribute immutable public staking_contract_eth;
    Distribute immutable public staking_contract_token;

    event ProfitToken(uint256 amount);
    event ProfitEth(uint256 amount);
    event StakeChanged(uint256 total, uint256 timestamp);

    constructor(IERC20 stake_token, IERC20 reward_token, uint256 decimals) {
        _token = stake_token;
        staking_contract_eth = new Distribute(decimals, IERC20(address(0)));
        staking_contract_token = new Distribute(decimals, reward_token);
    }

    function distribute_eth() payable external {
        staking_contract_eth.distribute{value : msg.value}(0, msg.sender);
        emit ProfitEth(msg.value);
    }

    function distribute(uint256 amount) external {
        staking_contract_token.distribute(amount, msg.sender);
        emit ProfitToken(amount);
    }
    
    /**
        @dev Stakes a certain amount of tokens, this MUST transfer the given amount from the account
        @param amount Amount of ERC20 token to stake
        @param data Additional data as per the EIP900
    */
    function stake(uint256 amount, bytes calldata data) external override {
        stakeFor(msg.sender, amount, data);
    }

    /**
        @dev Stakes a certain amount of tokens, this MUST transfer the given amount from the caller
        @param account Address who will own the stake afterwards
        @param amount Amount of ERC20 token to stake
        @param data Additional data as per the EIP900
    */
    function stakeFor(address account, uint256 amount, bytes calldata data) public override {
        //transfer the ERC20 token from the account, he must have set an allowance of {amount} tokens
        _token.safeTransferFrom(msg.sender, address(this), amount);
        staking_contract_eth.stakeFor(account, amount);
        staking_contract_token.stakeFor(account, amount);
        emit Staked(account, amount, totalStakedFor(account), data);
        emit StakeChanged(staking_contract_eth.totalStaked(), block.timestamp);
    }

    /**
        @dev Unstakes a certain amount of tokens, this SHOULD return the given amount of tokens to the account, if unstaking is currently not possible the function MUST revert
        @param amount Amount of ERC20 token to remove from the stake
        @param data Additional data as per the EIP900
    */
    function unstake(uint256 amount, bytes calldata data) external override {
        staking_contract_eth.unstakeFrom(payable(msg.sender), amount);
        staking_contract_token.unstakeFrom(payable(msg.sender), amount);
        _token.safeTransfer(msg.sender, amount);
        emit Unstaked(msg.sender, amount, totalStakedFor(msg.sender), data);
        emit StakeChanged(staking_contract_eth.totalStaked(), block.timestamp);
    }

     /**
        @dev Withdraws rewards (basically unstake then restake)
        @param amount Amount of ERC20 token to remove from the stake
    */
    function withdraw(uint256 amount) external {
        staking_contract_eth.withdrawFrom(payable(msg.sender), amount);
        staking_contract_token.withdrawFrom(payable(msg.sender),amount);
    }

    /**
        @dev Returns the current total of tokens staked for an address
        @param account address owning the stake
        @return the total of staked tokens of this address
    */
    function totalStakedFor(address account) public view override returns (uint256) {
        return staking_contract_eth.totalStakedFor(account);
    }
    
    /**
        @dev Returns the current total of tokens staked
        @return the total of staked tokens
    */
    function totalStaked() external view override returns (uint256) {
        return staking_contract_eth.totalStaked();
    }

    /**
        @dev returns the total rewards stored for token and eth
    */
    function totalReward() external view returns (uint256 token, uint256 eth) {
        token = staking_contract_token.getTotalReward();
        eth = staking_contract_eth.getTotalReward();
    }

    /**
        @dev Address of the token being used by the staking interface
        @return ERC20 token token address
    */
    function token() external view override returns (address) {
        return address(_token);
    }

    /**
        @dev MUST return true if the optional history functions are implemented, otherwise false
        We dont want this
    */
    function supportsHistory() external pure override returns (bool) {
        return false;
    }

    /**
        @dev Returns how much ETH the user can withdraw currently
        @param account Address of the user to check reward for
        @return _eth the amount of ETH the account will perceive if he unstakes now
        @return __token the amount of tokens the account will perceive if he unstakes now
    */
    function getReward(address account) public view returns (uint256 _eth, uint256 __token) {
        _eth = staking_contract_eth.getReward(account);
        __token = staking_contract_token.getReward(account);
    }
}
// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// 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");
        }
    }
}

// File: staking/contracts/Distribute.sol



// SPDX-License-Identifier: NONE
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import '@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol';
import '@openzeppelin/contracts/access/Ownable.sol';
import '@openzeppelin/contracts/security/ReentrancyGuard.sol';

/**
 * staking contract for ERC20 tokens or ETH
 */
contract Distribute is Ownable, ReentrancyGuard {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    /**
     @dev This value is very important because if the number of bonds is too great
     compared to the distributed value, then the bond increase will be zero
     therefore this value depends on the number of decimals
     of the distributed token and I suggest it to be the same
     For example if the token has 18 decimals, then the precision should also have 18 decimals

    */
    uint256 immutable public PRECISION;

    uint256 public constant INITIAL_BOND_VALUE = 1000000;

    uint256 public bond_value = INITIAL_BOND_VALUE;
    //just for info
    uint256 public investor_count;

    uint256 private _total_staked;
    uint256 private _temp_pool;
    // the amount of dust left to distribute after the bond value has been updated
    uint256 public to_distribute;
    mapping(address => uint256) private _bond_value_addr;
    mapping(address => uint256) private _stakes;

    /// @dev token to distribute
    IERC20 immutable public reward_token;

    /**
        @dev Initialize the contract
        @param decimals Number of decimals of the reward token
        @param _reward_token The token used for rewards. Set to 0 for ETH
    */
    constructor(uint256 decimals, IERC20 _reward_token) Ownable() ReentrancyGuard() {
        reward_token = _reward_token;
        PRECISION = 10**decimals;
    }

    /**
        @dev Stakes a certain amount, this MUST transfer the given amount from the caller
        @param account Address who will own the stake afterwards
        @param amount Amount to stake
    */
    function stakeFor(address account, uint256 amount) public onlyOwner nonReentrant {
        require(account != address(0), "Distribute: Invalid account");
        require(amount > 0, "Distribute: Amount must be greater than zero");
        _total_staked = _total_staked.add(amount);
        if(_stakes[account] == 0) {
            investor_count++;
        }
        uint256 accumulated_reward = getReward(account);
        _stakes[account] = _stakes[account].add(amount);

        uint256 new_bond_value = accumulated_reward * PRECISION / _stakes[account];
        _bond_value_addr[account] = bond_value - new_bond_value;
    }

    /**
        @dev unstakes a certain amounts, if unstaking is currently not possible the function MUST revert
        @param account From whom
        @param amount Amount to remove from the stake
    */
    function unstakeFrom(address payable account, uint256 amount) public onlyOwner nonReentrant {
        require(account != address(0), "Distribute: Invalid account");
        require(amount > 0, "Distribute: Amount must be greater than zero");
        require(amount <= _stakes[account], "Distribute: Dont have enough staked");
        uint256 to_reward = _getReward(account, amount);
        _total_staked -= amount;
        _stakes[account] -= amount;
        if(_stakes[account] == 0) {
            investor_count--;
        }

        if(to_reward == 0) return;
        //take into account dust error during payment too
        if(address(reward_token) != address(0)) {
            reward_token.safeTransfer(account, to_reward);
        }
        else {
            Address.sendValue(account, to_reward);
        }
    }

     /**
        @dev Withdraws rewards (basically unstake then restake)
        @param account From whom
        @param amount Amount to remove from the stake
    */
    function withdrawFrom(address payable account, uint256 amount) external onlyOwner {
        unstakeFrom(account, amount);
        stakeFor(account, amount);
    }

    /**
        @dev Called contracts to distribute dividends
        Updates the bond value
        @param amount Amount of token to distribute
        @param from Address from which to take the token
    */
    function distribute(uint256 amount, address from) external payable onlyOwner nonReentrant {
        if(address(reward_token) != address(0)) {
            if(amount == 0) return;
            reward_token.safeTransferFrom(from, address(this), amount);
            require(msg.value == 0, "Distribute: Illegal distribution");
        } else {
            amount = msg.value;
        }

        if(_total_staked == 0) {
            // no stakes yet, put into temp pool
            _temp_pool = _temp_pool.add(amount);
            return;
        }

        // if a temp pool existed, add it to the current distribution
        if(_temp_pool > 0) {
            amount = amount.add(_temp_pool);
            _temp_pool = 0;
        }
        
        uint256 temp_to_distribute = to_distribute + amount;
        uint256 total_bonds = _total_staked / PRECISION;
        uint256 bond_increase = temp_to_distribute / total_bonds;
        uint256 distributed_total = total_bonds.mul(bond_increase);
        bond_value += bond_increase;
        //collect the dust because of the PRECISION used for bonds
        //it will be reinjected into the next distribution
        to_distribute = temp_to_distribute - distributed_total;
    }

    /**
        @dev Returns the current total staked for an address
        @param account address owning the stake
        @return the total staked for this account
    */
    function totalStakedFor(address account) external view returns (uint256) {
        return _stakes[account];
    }
    
    /**
        @return current staked token
    */
    function totalStaked() external view returns (uint256) {
        return _total_staked;
    }

    /**
        @dev Returns how much the user can withdraw currently
        @param account Address of the user to check reward for
        @return the amount account will perceive if he unstakes now
    */
    function getReward(address account) public view returns (uint256) {
        return _getReward(account,_stakes[account]);
    }

    /**
        @dev returns the total amount of stored rewards
    */
    function getTotalReward() external view returns (uint256) {
        if(address(reward_token) != address(0)) {
            return reward_token.balanceOf(address(this));
        } else {
            return address(this).balance;
        }
    }

    /**
        @dev Returns how much the user can withdraw currently
        @param account Address of the user to check reward for
        @param amount Number of stakes
        @return the amount account will perceive if he unstakes now
    */
    function _getReward(address account, uint256 amount) internal view returns (uint256) {
        return amount.mul(bond_value.sub(_bond_value_addr[account])) / PRECISION;
    }
}

// File: staking/contracts/interfaces/IERC900.sol



// SPDX-License-Identifier: NONE
pragma solidity ^0.8.0;

//https://github.com/ethereum/EIPs/blob/master/EIPS/eip-900.md
interface IERC900 {
    event Staked(address indexed addr, uint256 amount, uint256 total, bytes data);
    event Unstaked(address indexed addr, uint256 amount, uint256 total, bytes data);

    function stake(uint256 amount, bytes calldata data) external;
    function stakeFor(address addr, uint256 amount, bytes calldata data) external;
    function unstake(uint256 amount, bytes calldata data) external;
    function totalStakedFor(address addr) external view returns (uint256);
    function totalStaked() external view returns (uint256);
    function token() external view returns (address);
    function supportsHistory() external pure returns (bool);

    // optional
    //function lastStakedFor(address addr) public view returns (uint256);
    //function totalStakedForAt(address addr, uint256 blockNumber) public view returns (uint256);
    //function totalStakedAt(uint256 blockNumber) public view returns (uint256);
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// 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);
}

// File: @openzeppelin/contracts/utils/Address.sol



// 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);
            }
        }
    }
}

// File: @openzeppelin/contracts/utils/math/SafeMath.sol



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

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        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/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// 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: @openzeppelin/contracts/utils/Context.sol



// 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;
    }
}