// File: contracts/Presale.sol



import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Presale is Ownable, Pausable, ReentrancyGuard {
    using SafeERC20 for ERC20;
    /* ======== EVENTS ======== */

    event TokenAddress(address tokenAddress);
    event TokenGenerationEvent(uint256 TGE);
    event AvailableTokens(uint256 availableTokens);
    event PricePerToken(uint256 pricePerToken);
    event TotalClaimed(uint256 totalClaimed);
    event DeployedOnBlock(uint256 deployedOnBlock);
    event TokensSold(uint256 tokensSold);
    event MaxTokensPerWallet(uint256 maxTokensPerWallet);
    event BlockWaitForClaim(uint256 blockWaitForClaim);
    event ClaimedTokens(address user, uint256 amount);
    event BoughtTokens(address user, uint256 amountToPay, uint256 amountToReceive);
    event WithdrawTokens(address user, uint256 amount);
    event PurchaseDisabled(bool purchaseDisabled);
    event ClaimDisabled(bool claimDisabled);
    event MinPurchasePerTransaction(uint256 amount);
    event MaxQuantityPerTransaction(uint256 amount);
    event MaxClaimPerBlockWait(uint256 maxClaimPerBlockWait);
    event Treasury(address treasury);
    event EmergencyUpdateWallet(
        address user,
        uint256 hasClaimedInTotal,
        uint256 tokensBought
    );
    event UpdateReferral(string artist, uint256 amountInWei, bool disabled);
    event UpdatePayment(address token, uint8 tokenDecimal, uint256 pricePerToken, bool disabled);

    /* ======== VARS ======== */

    address public tokenAddress; // The token address the user claims
    address public treasury; // The treasury address

    uint256 public deployedOnBlock; // The block number the contract has been deployed on
    uint256 public TGE; // The first claim in x % for TGE
    uint256 public blockWaitForClaim; // Users have to wait x days before claim opens again
    uint256 public maxClaimPerBlockWait; // After TGE users can claim only a max of x %
    uint256 public totalClaimed = 0; // Total tokens that has been claimed
    uint256 public maxPurchasePerTx = 1000000; // The max tokens per tx
    uint256 public maxTokensPerWallet = 1000000 ether; // the max tokens per wallet
    uint256 public availableTokens; // Max tokens to sell
    uint256 public tokensSold = 0; // The amount of tokens already sold

    bool public purchaseDisabled = false; // enable and disable purchase
    bool public claimDisabled = false; // enable and disable claim

    /* ======== STRUCTS ======== */

    struct Presaler {
        uint256 tokensBought; // How many tokens the user has bought
        uint256 hasClaimedInTotal; // How many tokens the user has claimed already
    }

    struct Referral {
        string name; // The name of the artist
        uint256 amount; // The amount of tokens that has been bought with the referral link
        bool disabled; // Enable or disable the referall link
    }

    struct Payment {
        address token; // The address of the token
        uint8 tokenDecimal; // The token decimal
        uint256 pricePerToken; // the price for 1 token
        bool disabled; // Is the token disabled or enabled
    }

    /* ======== MAPPINGS ======== */

    mapping(address => Presaler) public presaler;
    mapping(address => Payment) public payment;
    mapping(string => Referral) public referral;

    /* ======== CONSTRUCTOR ======== */

    constructor(
        uint256 _TGE,
        uint256 _blockWaitForClaim,
        uint256 _maxClaimPerBlockWait,
        uint256 _availableTokens
    ) {
        setTokenGenerationEventAward(_TGE);
        setBlockWaitForClaim(_blockWaitForClaim);
        setMaxClaimPerBlockWait(_maxClaimPerBlockWait);
        setAvailableTokens(_availableTokens);
    }

    /* ======== MODIFIERS ======== */

    /**
     * @dev Throws if called by any account other than the treasury.
     */
    modifier onlyTreasury() {
        require(treasury == _msgSender(), "caller is not the treasury");
        _;
    }

    /**
     * @dev Throws if purchaseDisabled is disabled
     */
    modifier whenPurchaseNotDisabled() {
        require(!purchaseDisabled, "Purchase has been disabled");
        _;
    }

    /**
     * @dev Throws if purchaseDisabled is disabled
     */
    modifier whenClaimNotDisabled() {
        require(!claimDisabled, "Claim has been disabled");
        _;
    }

    /* ======== OWNER ONLY ======== */

    /**
     * @dev sets the new token address for users to claim.
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setTokenAddress(address _tokenAddress) public onlyOwner {
        tokenAddress = _tokenAddress;
        emit TokenAddress(_tokenAddress);
    }

    /**
     * @dev sets the new token address for users to claim.
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setPurchaseDisabled(bool _purchaseDisabled) public onlyOwner {
        purchaseDisabled = _purchaseDisabled;
        emit PurchaseDisabled(_purchaseDisabled);
    }

    /**
     * @dev sets the new token address for users to claim.
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setClaimDisabled(bool _claimDisabled) public onlyOwner {
        claimDisabled = _claimDisabled;
        emit ClaimDisabled(_claimDisabled);
    }

    /**
     * @dev sets the new percentage of max claim the user can do after `blockWaitForClaim` has passed
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setMaxClaimPerBlockWait(uint256 _maxClaimPerBlockWait)
        public
        onlyOwner
    {
        maxClaimPerBlockWait = _maxClaimPerBlockWait;
        emit MaxClaimPerBlockWait(_maxClaimPerBlockWait);
    }

    /**
     * @dev sets the new TGE claim percentage
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setTokenGenerationEventAward(uint256 _TGE) public onlyOwner {
        TGE = _TGE;
        emit TokenGenerationEvent(_TGE);
    }

    /**
     * @dev the amount of blocks the users needs to wait before the new claim can happen.
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setBlockWaitForClaim(uint256 _blockWaitForClaim) public onlyOwner {
        blockWaitForClaim = _blockWaitForClaim;
        emit BlockWaitForClaim(_blockWaitForClaim);
    }

    /**
     * @dev The max tokens per transaction that can be bought
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setMaxPurchasePerTx(uint256 _maxPurchasePerTx) public onlyOwner {
        maxPurchasePerTx = _maxPurchasePerTx;
        emit MaxQuantityPerTransaction(_maxPurchasePerTx);
    }

    /**
     * @dev Sets the new treasury address
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setTreasury(address _treasury) public onlyOwner {
        treasury = _treasury;
        emit Treasury(_treasury);
    }

    /**
     * @dev The max amount of tokens a wallet can hold
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setMaxTokensPerWallet(uint256 _maxTokensPerWallet)
        public
        onlyOwner
    {
        maxTokensPerWallet = _maxTokensPerWallet;
        emit MaxTokensPerWallet(_maxTokensPerWallet);
    }

    /**
     * @dev Sets the deployed block number.
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setDeployedOnBlock(uint256 _deployedOnBlock) public onlyOwner {
        deployedOnBlock = _deployedOnBlock;
        emit DeployedOnBlock(_deployedOnBlock);
    }

    /**
     * @dev Sets the available tokens for sell in the pre-sale
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setAvailableTokens(uint256 _availableTokens) public onlyOwner {
        availableTokens = _availableTokens;
        emit AvailableTokens(_availableTokens);
    }

    /**
     * @dev Add a referral link
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setReferral(
        string memory _artist,
        uint256 _amountInWei,
        bool _disabled
    ) public onlyOwner {
        referral[_artist] = Referral({
            name: _artist,
            amount: _amountInWei,
            disabled: _disabled
        });
        emit UpdateReferral(_artist, _amountInWei, _disabled);
    }

      /**
     * @dev Add a new payment
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setPayment(
        address _token,
        uint8 _tokenDecimal,
        uint256 _pricePerToken,
        bool _disabled
    ) public onlyOwner {
        payment[_token] = Payment({
            token: _token,
            tokenDecimal: _tokenDecimal,
            pricePerToken: _pricePerToken,
            disabled: _disabled
        });
        emit UpdatePayment(_token, _tokenDecimal, _pricePerToken, _disabled);
    }

    /**
     * @dev in case there is a bug where the presaler has wrong stats, we can set it to the correct numbers. Emergency ONLY
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setEmergencyPresalerClaimStats(
        address _user,
        uint256 _hasClaimedInTotal,
        uint256 _tokensBought
    ) public onlyOwner {
        presaler[_user] = Presaler({
            hasClaimedInTotal: _hasClaimedInTotal,
            tokensBought: _tokensBought
        });
        emit EmergencyUpdateWallet(_user, _hasClaimedInTotal, _tokensBought);
    }

    /**
     * @dev in case there is a bug where the total claimed is not right anymore, we can set it back to the correct number. Emergency ONLY
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setEmergencyTotalClaimed(uint256 _totalClaimed) public onlyOwner {
        totalClaimed = _totalClaimed;
        emit TotalClaimed(_totalClaimed);
    }

    /**
     * @dev in case there is a bug where the tokens sold is not right anymore, we can set it back to the correct number. Emergency ONLY
     *
     * Requirements:
     *
     * - Only the owner can call this function
     */
    function setEmergencyTokensSold(uint256 _tokensSold) public onlyOwner {
        tokensSold = _tokensSold;
        emit TokensSold(_tokensSold);
    }

    /**
     * @dev See {Pausable-_pause}.
     *
     * Requirements:
     *
     * - Only the owner can call this function
     * - The contract must not be paused.
     */
    function pause() public onlyOwner whenNotPaused {
        super._pause();
    }

    /**
     * @dev See {Pausable-_unpause}.
     *
     * Requirements:
     *
     * - Only the owner can call this function
     * - The contract must be paused.
     */
    function unpause() public onlyOwner whenPaused {
        super._unpause();
    }

    /**
     * @dev Withdraw the tokens in the contract if there is leftovers
     *
     * Requirements:
     *
     * - Only the owner can call this function
     * - The contract must be paused.
     * - See {ReentrancyGuard-nonReentrant}
     */
    function withdrawTokens() public whenPaused nonReentrant onlyOwner {
        require(
            ERC20(tokenAddress).balanceOf(address(this)) > 0,
            "Their is no tokens to withdraw"
        );
        ERC20(tokenAddress).approve(
            address(this),
            ERC20(tokenAddress).balanceOf(address(this))
        );
        ERC20(tokenAddress).transfer(
            _msgSender(),
            ERC20(tokenAddress).balanceOf(address(this))
        );

        emit WithdrawTokens(
            _msgSender(),
            ERC20(tokenAddress).balanceOf(address(this))
        );
    }

    /**
     * @dev Withdraw the ETH from the contract
     *
     * Requirements:
     *
     * - Only the owner can call this function
     * - See {ReentrancyGuard-nonReentrant}
     */
    function withdrawEth() external onlyTreasury nonReentrant {
        payable(address(treasury)).transfer(address(this).balance);
    }

    /* ======== PUBLIC ======== */

    /**
     * @dev Returns the token amount based on the rewardTokenCount and the rate
     */
    function getTokenAmount(uint256 _amount, Payment memory paymentCurrency) public pure returns (uint256, uint256) {
        uint256 amountToPay = _amount * paymentCurrency.pricePerToken;
        uint256 amountToReceive = _amount * (10 ** 18);
        return (amountToPay, amountToReceive);
    }

    /**
     * @dev Returns the claimable amount for a wallet
     */
    function getClaimable(address _buyer)
        public
        view
        returns (uint256, uint256)
    {
        Presaler memory user = presaler[_buyer];
        uint256 hasClaimedInTotal = 0;
        uint256 totalClaim = user.tokensBought;

        // calculate TGE
        hasClaimedInTotal += (totalClaim * TGE) / 100;
        
        // calculate claim amount over periods
        uint256 periodsToClaim = (block.number - deployedOnBlock) / blockWaitForClaim;
        hasClaimedInTotal += (totalClaim * (maxClaimPerBlockWait * periodsToClaim)) / 100;

        if (hasClaimedInTotal > totalClaim) {
            hasClaimedInTotal = totalClaim;
        }

        // substract amount already claimed
        uint256 claimableAmount = hasClaimedInTotal - user.hasClaimedInTotal;
        return (claimableAmount, hasClaimedInTotal);
    }

    /**
     * @dev Buy presale tokens
     *
     * Requirements:
     *
     * - Paused must be `false`
     * - `purchaseDisabled` must be `false`
     */
    function buyTokens(address _tokenAddress, uint256 _amount)
        public
        payable
        whenNotPaused
        whenPurchaseNotDisabled
    {
        require((availableTokens - _amount) >= 0, "Reached max tokens");

        Payment memory paymentCurrency = payment[_tokenAddress];

        require(address(0) != paymentCurrency.token, "Payment address does not exists");
        require(!paymentCurrency.disabled, "Payment is disabled");
        require(_amount > 0, "Amount must be higher than 0");

        (uint256 amountToPay, uint256 amountToReceive) = getTokenAmount(_amount, paymentCurrency);
        require(amountToPay > 0, "Amount to pay must be higher than 0");
        require(amountToReceive > 0, "Amount to receive must be higher than 0");

        require(_amount <= maxPurchasePerTx, "Must purchase below or equal to `maxPurchasePerTx`");
        require(ERC20(paymentCurrency.token).balanceOf(_msgSender()) >= amountToPay, "Not enough balance");

        Presaler memory user = presaler[_msgSender()];
        uint256 totalTokensBought = user.tokensBought + amountToReceive;
        require(totalTokensBought <= maxTokensPerWallet, "Reached max tokens per wallet");

        presaler[_msgSender()].tokensBought = totalTokensBought;

        tokensSold = tokensSold + _amount;
        availableTokens = availableTokens - _amount;

        ERC20(paymentCurrency.token).safeTransferFrom(_msgSender(), treasury, amountToPay);
        emit BoughtTokens(_msgSender(), amountToPay, amountToReceive);
    }

    /**
     * @dev Buy presale tokens with a valid referral code
     *
     * Requirements:
     *
     * - Paused must be `false`
     * - `purchaseDisabled` must be `false`
     */
    function buyTokensWithReferral(string memory _artist, address _tokenAddress, uint256 _amount)
        public
        payable
        whenNotPaused
        whenPurchaseNotDisabled
    {
        Referral memory ref = referral[_artist];
        require(bytes(ref.name).length > 0, "Referral link is invalid");
        require(!ref.disabled, "Referral link is disabled");

        buyTokens(_tokenAddress, _amount);

        Payment memory paymentCurrency = payment[_tokenAddress];
        (,uint256 amountToReceive) = getTokenAmount(_amount, paymentCurrency);
        referral[_artist].amount += amountToReceive;
    }

    /**
     * @dev Claim tokens periodically
     *
     * Requirements:
     *
     * - Paused must be `false`
     * - See {ReentrancyGuard-nonReentrant}
     */
    function claim() public whenNotPaused whenClaimNotDisabled nonReentrant {
        Presaler memory user = presaler[_msgSender()];
        require(deployedOnBlock > 0, "deployedOnBlock must be higher than 0");
        require(user.tokensBought > 0, "No tokens bought to claim");
        require(user.hasClaimedInTotal < user.tokensBought, "Already claimed total");
        require(ERC20(tokenAddress).balanceOf(address(this)) > 0, "No tokens left");

        (uint256 claimableAmount, uint256 hasClaimedInTotal) = getClaimable( _msgSender() );

        require(claimableAmount > 0, "Nothing to claim");
        require(ERC20(tokenAddress).balanceOf(address(this)) >= claimableAmount, "No tokens left");

        presaler[_msgSender()].hasClaimedInTotal = hasClaimedInTotal;
        totalClaimed += claimableAmount;

        // send amount to claim
        ERC20(tokenAddress).approve(address(this), claimableAmount);
        ERC20(tokenAddress).transferFrom(address(this), _msgSender(), claimableAmount);
        emit ClaimedTokens(_msgSender(), claimableAmount);
    }
}

// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT

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/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

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

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

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

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

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

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

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

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

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

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

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

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

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

        return true;
    }

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

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

        return true;
    }

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

        _beforeTokenTransfer(sender, recipient, amount);

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

        emit Transfer(sender, recipient, amount);

        _afterTokenTransfer(sender, recipient, amount);
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT

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() {
        _setOwner(_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 {
        _setOwner(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");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/security/Pausable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// File: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT

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 make 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/IERC20.sol



// SPDX-License-Identifier: MIT

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

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/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC20.sol";

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

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

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

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



// SPDX-License-Identifier: MIT

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;
    }
}