// File: contracts/PandaClaim.sol



/*
 **                                                                                                                                                              
 **                                                                   dddddddd                                                                                   
 **  PPPPPPPPPPPPPPPPP                                                d::::::d                  DDDDDDDDDDDDD                  AAA                 OOOOOOOOO     
 **  P::::::::::::::::P                                               d::::::d                  D::::::::::::DDD              A:::A              OO:::::::::OO   
 **  P::::::PPPPPP:::::P                                              d::::::d                  D:::::::::::::::DD           A:::::A           OO:::::::::::::OO 
 **  PP:::::P     P:::::P                                             d:::::d                   DDD:::::DDDDD:::::D         A:::::::A         O:::::::OOO:::::::O
 **    P::::P     P:::::Paaaaaaaaaaaaa  nnnn  nnnnnnnn        ddddddddd:::::d   aaaaaaaaaaaaa     D:::::D    D:::::D       A:::::::::A        O::::::O   O::::::O
 **    P::::P     P:::::Pa::::::::::::a n:::nn::::::::nn    dd::::::::::::::d   a::::::::::::a    D:::::D     D:::::D     A:::::A:::::A       O:::::O     O:::::O
 **    P::::PPPPPP:::::P aaaaaaaaa:::::an::::::::::::::nn  d::::::::::::::::d   aaaaaaaaa:::::a   D:::::D     D:::::D    A:::::A A:::::A      O:::::O     O:::::O
 **    P:::::::::::::PP           a::::ann:::::::::::::::nd:::::::ddddd:::::d            a::::a   D:::::D     D:::::D   A:::::A   A:::::A     O:::::O     O:::::O
 **    P::::PPPPPPPPP      aaaaaaa:::::a  n:::::nnnn:::::nd::::::d    d:::::d     aaaaaaa:::::a   D:::::D     D:::::D  A:::::A     A:::::A    O:::::O     O:::::O
 **    P::::P            aa::::::::::::a  n::::n    n::::nd:::::d     d:::::d   aa::::::::::::a   D:::::D     D:::::D A:::::AAAAAAAAA:::::A   O:::::O     O:::::O
 **    P::::P           a::::aaaa::::::a  n::::n    n::::nd:::::d     d:::::d  a::::aaaa::::::a   D:::::D     D:::::DA:::::::::::::::::::::A  O:::::O     O:::::O
 **    P::::P          a::::a    a:::::a  n::::n    n::::nd:::::d     d:::::d a::::a    a:::::a   D:::::D    D:::::DA:::::AAAAAAAAAAAAA:::::A O::::::O   O::::::O
 **  PP::::::PP        a::::a    a:::::a  n::::n    n::::nd::::::ddddd::::::dda::::a    a:::::a DDD:::::DDDDD:::::DA:::::A             A:::::AO:::::::OOO:::::::O
 **  P::::::::P        a:::::aaaa::::::a  n::::n    n::::n d:::::::::::::::::da:::::aaaa::::::a D:::::::::::::::DDA:::::A               A:::::AOO:::::::::::::OO 
 **  P::::::::P         a::::::::::aa:::a n::::n    n::::n  d:::::::::ddd::::d a::::::::::aa:::aD::::::::::::DDD A:::::A                 A:::::A OO:::::::::OO   
 **  PPPPPPPPPP          aaaaaaaaaa  aaaa nnnnnn    nnnnnn   ddddddddd   ddddd  aaaaaaaaaa  aaaaDDDDDDDDDDDDD   AAAAAAA                   AAAAAAA  OOOOOOOOO     
 **  
*/
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";


contract PandaClaim is Ownable, ReentrancyGuard {
    using SafeERC20 for IERC20;

    
    address public immutable pandaToken;
    address public usdToken;
    mapping(address => uint256) public claimRecord;
    mapping(address => uint256) public pandaClaimSum;
    mapping(address => uint256) public usdClaimSum;
    mapping(address => uint256) public etherClaimSum;
    uint256 public claimCycle;
    bool public claimOpen;
    // bytes32 public merkleRoot;
    bytes32 public merkleRoot;
    uint256 public totalClaimPanda;
    uint256 public totalClaimUsd;
    uint256 public totalClaimEth;

    address public constant ZERO_ADDRESS = address(0);

    event MerkleRootChanged(bytes32 merkleRoot);
    event UsdTokenChanged(address usdToken);
    event ClaimPanda(address indexed claimant, uint256 amount, uint256 sumAmount, uint256 etherAmount, uint256 etherSumAmount, uint256 usdAmount, uint256 usdSumAmount);
    event WithdrawERC20(address recipient, address tokenAddress, uint256 tokenAmount);
    event WithdrawEther(address recipient, uint256 amount);
    event ClaimOpenChange(bool open);

    /**
     * ErrorCode:
     * PE1:PandaDAO:Zero address
     * PE2:PandaDAO:claim zore tokens!
     * PE3:PandaDAO:same _merkleRoot
     * PE4:PandaDAO:same usd Token!
     * PE5:PandaDAO:Valid claimCycle required.
     * PE6:PandaDAO:PandaCliam dont have enough $PANDA.
     * PE7:PandaDAO:Valid panda proof required.
     * PE8:PandaDAO:PandaDAO:claim close!
     * PE9:PandaDAO:transfer ether fail!
     * PE10:PandaDAO:invalid arguements
     * PE11:PandaDAO:withdrawEther fail!
     * PE12:PandaDAO: PandaDAO:claim open same
     * PE13:PandaDAO:PandaCliam dont have enough $ETH.
     * PE14:PandaDAO:PandaCliam dont have enough $USD.
     */

    modifier notZeroAddr(address addr_) {
        require(addr_ != ZERO_ADDRESS, "PE1");
        _;
    }



    /**
     * @dev Constructor.
     */
    constructor(
        address _pandaToken,
        address _usdToken
    )
    {
        pandaToken = _pandaToken;
        usdToken = _usdToken;
    }


    /**
     * @dev Claims  tokens.
     * @param amount The amount of panda.
     * @param etherAmount The amount of ether.
     * @param usdAmount The amount of usd.
     * @param merkleProof A merkle proof proving the claim is valid.
     */
    function claimPandaTokens(uint256 amount, uint256 etherAmount, uint256 usdAmount, bytes32[] calldata merkleProof) external nonReentrant {
        require(claimOpen, "PE8");
        //claimCycle check
        require(claimRecord[msg.sender] < claimCycle, "PE5");
        require(amount + etherAmount + usdAmount > 0, "PE2");

        //balance check
        require(IERC20(pandaToken).balanceOf(address(this)) >= amount, "PE6");
        require(address(this).balance >= etherAmount, "PE13");
        require(IERC20(usdToken).balanceOf(address(this)) >= usdAmount, "PE14");
        //merkle check
        bytes32 leaf = keccak256(abi.encodePacked(msg.sender, amount, etherAmount, usdAmount));
        bool valid = MerkleProof.verify(merkleProof, merkleRoot, leaf);
        require(valid, "PE7");
        //update claimCycle
        claimRecord[msg.sender] = claimCycle;

        //transfer token
        if(amount > 0) {
            IERC20(pandaToken).safeTransfer(msg.sender, amount);
        }
        if (etherAmount > 0) {
            (bool success,) = msg.sender.call{value:etherAmount}("");
            require(success, "PE9");
        }
        if (usdAmount > 0) {
            IERC20(usdToken).safeTransfer(msg.sender, usdAmount);
        }
        
        pandaClaimSum[msg.sender] += amount;
        etherClaimSum[msg.sender] += etherAmount;
        usdClaimSum[msg.sender] += usdAmount;
        totalClaimPanda += amount;
        totalClaimEth += etherAmount;
        totalClaimUsd += usdAmount;
        emit ClaimPanda(msg.sender, amount, pandaClaimSum[msg.sender], etherAmount, etherClaimSum[msg.sender], usdAmount, usdClaimSum[msg.sender]);
    }




    /**
     * @dev Sets the merkle root. Only callable if the root is not yet set.
     * @param _merkleRoot tokens claim merkle tree.
     */
    function setMerkleRoot(bytes32 _merkleRoot) external onlyOwner {
        merkleRoot = _merkleRoot;
        claimCycle++;
        emit MerkleRootChanged(_merkleRoot);
    }

    /**
     * @dev update the merkle root.
     * @param _merkleRoot tokens claim merkle tree.
     */
    function updateMerkleRoot(bytes32 _merkleRoot) external onlyOwner {
        require(merkleRoot != _merkleRoot, "PE3");
        merkleRoot = _merkleRoot;
        emit MerkleRootChanged(_merkleRoot);
    }

    /**
     * @dev set Usd Token Address
     * @param _token token address
     */
    function setUsdToken(address _token) external onlyOwner notZeroAddr(_token) {
        require(usdToken != _token, "PE4");
        usdToken = _token;
        emit UsdTokenChanged(_token);
    }

    /**
     * @dev set claim open ro not
     * @param _open true or false
     */
    function setClaimOpen(bool _open) external onlyOwner {
        require(_open != claimOpen, "PE12");
        claimOpen = _open;
        emit ClaimOpenChange(_open);
    }


    /**
     * @dev withdrawERC20  tokens.
     * @param recipient recipient
     * @param tokenAddress  token
     * @param tokenAmount amount
     */
    function withdrawERC20(
        address recipient,
        address tokenAddress, 
        uint256 tokenAmount
    ) external onlyOwner notZeroAddr(tokenAddress) 
    {
        IERC20(tokenAddress).safeTransfer(recipient, tokenAmount);

        emit WithdrawERC20(recipient, tokenAddress, tokenAmount);
    }

    

    /**
     * @dev withdraw Ether.
     * @param recipient recipient
     * @param amount amount
     */
    function withdrawEther(address payable recipient, uint256 amount) external onlyOwner {
        (bool success,) = recipient.call{value:amount}("");
        require(success, "PE11");
        emit WithdrawEther(recipient, amount);
    }

    fallback () external payable {}

    receive () external payable {}


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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (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 `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);

    /**
     * @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/cryptography/MerkleProof.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/cryptography/MerkleProof.sol)

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Trees 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.
 */
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 Returns the rebuilt hash obtained by traversing a Merklee 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++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = _efficientHash(computedHash, proofElement);
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = _efficientHash(proofElement, computedHash);
            }
        }
        return computedHash;
    }

    function _efficientHash(bytes32 a, bytes32 b) private pure returns (bytes32 value) {
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}

// 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/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: @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;
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (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

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