// File: contracts/harvest/OETHDripper.sol



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

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

/**
 * @title OETH Dripper Contract
 * @author Origin Protocol Inc
 */
contract OETHDripper is Dripper {
    constructor(address _vault, address _token) Dripper(_vault, _token) {}
}

// File: contracts/harvest/Dripper.sol



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

import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import { Governable } from "../governance/Governable.sol";
import { IVault } from "../interfaces/IVault.sol";

/**
 * @title OUSD Dripper
 *
 * The dripper contract smooths out the yield from point-in-time yield events
 * and spreads the yield out over a configurable time period. This ensures a
 * continuous per block yield to makes users happy as their next rebase
 * amount is always moving up. Also, this makes historical day to day yields
 * smooth, rather than going from a near zero day, to a large APY day, then
 * back to a near zero day again.
 *
 *
 * Design notes
 * - USDT has a smaller resolution than the number of seconds
 * in a week, which can make per block payouts have a rounding error. However
 * the total effect is not large - cents per day, and this money is
 * not lost, just distributed in the future. While we could use a higher
 * decimal precision for the drip perBlock, we chose simpler code.
 * - By calculating the changing drip rates on collects only, harvests and yield
 * events don't have to call anything on this contract or pay any extra gas.
 * Collect() is already be paying for a single write, since it has to reset
 * the lastCollect time.
 * - By having a collectAndRebase method, and having our external systems call
 * that, the OUSD vault does not need any changes, not even to know the address
 * of the dripper.
 * - A rejected design was to retro-calculate the drip rate on each collect,
 * based on the balance at the time of the collect. While this would have
 * required less state, and would also have made the contract respond more quickly
 * to new income, it would break the predictability that is this contract's entire
 * purpose. If we did this, the amount of fundsAvailable() would make sharp increases
 * when funds were deposited.
 * - When the dripper recalculates the rate, it targets spending the balance over
 * the duration. This means that every time that collect is is called, if no
 * new funds have been deposited the duration is being pushed back and the
 * rate decreases. This is expected, and ends up following a smoother but
 * longer curve the more collect() is called without incoming yield.
 *
 */

contract Dripper is Governable {
    using SafeERC20 for IERC20;

    struct Drip {
        uint64 lastCollect; // overflows 262 billion years after the sun dies
        uint192 perBlock; // drip rate per block
    }

    address immutable vault; // OUSD vault
    address immutable token; // token to drip out
    uint256 public dripDuration; // in seconds
    Drip public drip; // active drip parameters

    constructor(address _vault, address _token) {
        vault = _vault;
        token = _token;
    }

    /// @notice How much funds have dripped out already and are currently
    //   available to be sent to the vault.
    /// @return The amount that would be sent if a collect was called
    function availableFunds() external view returns (uint256) {
        uint256 balance = IERC20(token).balanceOf(address(this));
        return _availableFunds(balance, drip);
    }

    /// @notice Collect all dripped funds and send to vault.
    ///  Recalculate new drip rate.
    function collect() external {
        _collect();
    }

    /// @notice Collect all dripped funds, send to vault, recalculate new drip
    ///  rate, and rebase OUSD.
    function collectAndRebase() external {
        _collect();
        IVault(vault).rebase();
    }

    /// @dev Change the drip duration. Governor only.
    /// @param _durationSeconds the number of seconds to drip out the entire
    ///  balance over if no collects were called during that time.
    function setDripDuration(uint256 _durationSeconds) external onlyGovernor {
        require(_durationSeconds > 0, "duration must be non-zero");
        dripDuration = _durationSeconds;
        _collect(); // duration change take immediate effect
    }

    /// @dev Transfer out ERC20 tokens held by the contract. Governor only.
    /// @param _asset ERC20 token address
    /// @param _amount amount to transfer
    function transferToken(address _asset, uint256 _amount)
        external
        onlyGovernor
    {
        IERC20(_asset).safeTransfer(governor(), _amount);
    }

    /// @dev Calculate available funds by taking the lower of either the
    ///  currently dripped out funds or the balance available.
    ///  Uses passed in parameters to calculate with for gas savings.
    /// @param _balance current balance in contract
    /// @param _drip current drip parameters
    function _availableFunds(uint256 _balance, Drip memory _drip)
        internal
        view
        returns (uint256)
    {
        uint256 elapsed = block.timestamp - _drip.lastCollect;
        uint256 allowed = (elapsed * _drip.perBlock);
        return (allowed > _balance) ? _balance : allowed;
    }

    /// @dev Sends the currently dripped funds to be vault, and sets
    ///  the new drip rate based on the new balance.
    function _collect() internal {
        // Calculate send
        uint256 balance = IERC20(token).balanceOf(address(this));
        uint256 amountToSend = _availableFunds(balance, drip);
        uint256 remaining = balance - amountToSend;
        // Calculate new drip perBlock
        //   Gas savings by setting entire struct at one time
        drip = Drip({
            perBlock: uint192(remaining / dripDuration),
            lastCollect: uint64(block.timestamp)
        });
        // Send funds
        IERC20(token).safeTransfer(vault, amountToSend);
    }
}

// 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/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: contracts/governance/Governable.sol



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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

        _;

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

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

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

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

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

// File: contracts/interfaces/IVault.sol



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

interface IVault {
    event AssetSupported(address _asset);
    event AssetDefaultStrategyUpdated(address _asset, address _strategy);
    event AssetAllocated(address _asset, address _strategy, uint256 _amount);
    event StrategyApproved(address _addr);
    event StrategyRemoved(address _addr);
    event Mint(address _addr, uint256 _value);
    event Redeem(address _addr, uint256 _value);
    event CapitalPaused();
    event CapitalUnpaused();
    event RebasePaused();
    event RebaseUnpaused();
    event VaultBufferUpdated(uint256 _vaultBuffer);
    event RedeemFeeUpdated(uint256 _redeemFeeBps);
    event PriceProviderUpdated(address _priceProvider);
    event AllocateThresholdUpdated(uint256 _threshold);
    event RebaseThresholdUpdated(uint256 _threshold);
    event StrategistUpdated(address _address);
    event MaxSupplyDiffChanged(uint256 maxSupplyDiff);
    event YieldDistribution(address _to, uint256 _yield, uint256 _fee);
    event TrusteeFeeBpsChanged(uint256 _basis);
    event TrusteeAddressChanged(address _address);

    // Governable.sol
    function transferGovernance(address _newGovernor) external;

    function claimGovernance() external;

    function governor() external view returns (address);

    // VaultAdmin.sol
    function setPriceProvider(address _priceProvider) external;

    function priceProvider() external view returns (address);

    function setRedeemFeeBps(uint256 _redeemFeeBps) external;

    function redeemFeeBps() external view returns (uint256);

    function setVaultBuffer(uint256 _vaultBuffer) external;

    function vaultBuffer() external view returns (uint256);

    function setAutoAllocateThreshold(uint256 _threshold) external;

    function autoAllocateThreshold() external view returns (uint256);

    function setRebaseThreshold(uint256 _threshold) external;

    function rebaseThreshold() external view returns (uint256);

    function setStrategistAddr(address _address) external;

    function strategistAddr() external view returns (address);

    function setMaxSupplyDiff(uint256 _maxSupplyDiff) external;

    function maxSupplyDiff() external view returns (uint256);

    function setTrusteeAddress(address _address) external;

    function trusteeAddress() external view returns (address);

    function setTrusteeFeeBps(uint256 _basis) external;

    function trusteeFeeBps() external view returns (uint256);

    function ousdMetaStrategy() external view returns (address);

    function supportAsset(address _asset, uint8 _supportsAsset) external;

    function approveStrategy(address _addr) external;

    function removeStrategy(address _addr) external;

    function setAssetDefaultStrategy(address _asset, address _strategy)
        external;

    function assetDefaultStrategies(address _asset)
        external
        view
        returns (address);

    function pauseRebase() external;

    function unpauseRebase() external;

    function rebasePaused() external view returns (bool);

    function pauseCapital() external;

    function unpauseCapital() external;

    function capitalPaused() external view returns (bool);

    function transferToken(address _asset, uint256 _amount) external;

    function priceUnitMint(address asset) external view returns (uint256);

    function priceUnitRedeem(address asset) external view returns (uint256);

    function withdrawAllFromStrategy(address _strategyAddr) external;

    function withdrawAllFromStrategies() external;

    function reallocate(
        address _strategyFromAddress,
        address _strategyToAddress,
        address[] calldata _assets,
        uint256[] calldata _amounts
    ) external;

    function withdrawFromStrategy(
        address _strategyFromAddress,
        address[] calldata _assets,
        uint256[] calldata _amounts
    ) external;

    function depositToStrategy(
        address _strategyToAddress,
        address[] calldata _assets,
        uint256[] calldata _amounts
    ) external;

    // VaultCore.sol
    function mint(
        address _asset,
        uint256 _amount,
        uint256 _minimumOusdAmount
    ) external;

    function mintForStrategy(uint256 _amount) external;

    function redeem(uint256 _amount, uint256 _minimumUnitAmount) external;

    function burnForStrategy(uint256 _amount) external;

    function redeemAll(uint256 _minimumUnitAmount) external;

    function allocate() external;

    function rebase() external;

    function totalValue() external view returns (uint256 value);

    function checkBalance(address _asset) external view returns (uint256);

    function calculateRedeemOutputs(uint256 _amount)
        external
        view
        returns (uint256[] memory);

    function getAssetCount() external view returns (uint256);

    function getAllAssets() external view returns (address[] memory);

    function getStrategyCount() external view returns (uint256);

    function getAllStrategies() external view returns (address[] memory);

    function isSupportedAsset(address _asset) external view returns (bool);

    function netOusdMintForStrategyThreshold() external view returns (uint256);

    function setOusdMetaStrategy(address _ousdMetaStrategy) external;

    function setNetOusdMintForStrategyThreshold(uint256 _threshold) external;

    function netOusdMintedForStrategy() external view returns (int256);
}

// 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);
            }
        }
    }
}