// File: /contracts/Booster.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;


import "./interfaces/IStaker.sol";
import "./interfaces/IPoolRegistry.sol";
import "./interfaces/IProxyVault.sol";
import "./interfaces/IProxyOwner.sol";
import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol';


/*
Main interface for the whitelisted proxy contract.

**This contract is meant to be able to be replaced for upgrade purposes. use IVoterProxy.operator() to always reference the current booster

*/
contract Booster{
    using SafeERC20 for IERC20;

    address public constant fxs = address(0x3432B6A60D23Ca0dFCa7761B7ab56459D9C964D0);

    address public immutable proxy;
    address public immutable poolRegistry;
    address public immutable feeRegistry;
    address public owner;
    address public pendingOwner;
    address public poolManager;
    address public rewardManager;
    address public feeclaimer;
    bool public isShutdown;
    address public feeQueue;

    mapping(address=>mapping(address=>bool)) public feeClaimMap;

    mapping(address=>address) public proxyOwners;


    constructor(address _proxy, address _poolReg, address _feeReg) {
        proxy = _proxy;
        poolRegistry = _poolReg;
        feeRegistry = _feeReg;
        isShutdown = false;
        owner = msg.sender;
        rewardManager = msg.sender;
        poolManager = msg.sender;


        //TODO: consider moving to a module so dont have to set everything again if upgraded
        feeclaimer = address(0);//msg.sender;
        feeClaimMap[address(0xc6764e58b36e26b08Fd1d2AeD4538c02171fA872)][fxs] = true;
        emit FeeClaimPairSet(address(0xc6764e58b36e26b08Fd1d2AeD4538c02171fA872), fxs, true);
        feeQueue = address(0x4f3AD55D7b884CDC48ADD1e2451A13af17887F26);//stash for cvxfxs convex pool
        emit FeeQueueChanged(address(0x4f3AD55D7b884CDC48ADD1e2451A13af17887F26));

        //set our proxy as its own owner
        proxyOwners[_proxy] = _proxy;
    }

    /////// Owner Section /////////

    modifier onlyOwner() {
        require(owner == msg.sender, "!auth");
        _;
    }

    modifier onlyPoolManager() {
        require(poolManager == msg.sender, "!auth");
        _;
    }

    //set pending owner
    function setPendingOwner(address _po) external onlyOwner{
        pendingOwner = _po;
        emit SetPendingOwner(_po);
    }

    function _proxyCall(address _to, bytes memory _data) internal{
        (bool success,) = IStaker(proxy).execute(_to,uint256(0),_data);
        require(success, "Proxy Call Fail");
    }

    //claim ownership
    function acceptPendingOwner() external {
        require(pendingOwner != address(0) && msg.sender == pendingOwner, "!p_owner");

        owner = pendingOwner;
        pendingOwner = address(0);
        emit OwnerChanged(owner);
    }

    //set fee queue, a contract fees are moved to when claiming
    function setFeeQueue(address _queue) external onlyOwner{
        feeQueue = _queue;
        emit FeeQueueChanged(_queue);
    }

    //set who can call claim fees, 0x0 address will allow anyone to call
    function setFeeClaimer(address _claimer) external onlyOwner{
        feeclaimer = _claimer;
        emit FeeClaimerChanged(_claimer);
    }

    function setFeeClaimPair(address _claimAddress, address _token, bool _active) external onlyOwner{
        feeClaimMap[_claimAddress][_token] = _active;
        emit FeeClaimPairSet(_claimAddress, _token, _active);
    }

    function addProxyOwner(address _proxy, address _owner) external onlyOwner{
        proxyOwners[_proxy] = _owner;
        emit ProxyOwnerSet(_proxy, _owner);
    }

    //set a reward manager address that controls extra reward contracts for each pool
    function setRewardManager(address _rmanager) external onlyOwner{
        rewardManager = _rmanager;
        emit RewardManagerChanged(_rmanager);
    }

    //set pool manager
    function setPoolManager(address _pmanager) external onlyOwner{
        poolManager = _pmanager;
        emit PoolManagerChanged(_pmanager);
    }
    
    //shutdown this contract.
    function shutdownSystem() external onlyOwner{
        //This version of booster does not require any special steps before shutting down
        //and can just immediately be set.
        isShutdown = true;
        emit Shutdown();
    }

    //claim operator roles for certain systems for direct access
    function claimOperatorRoles() external onlyOwner{
        require(!isShutdown,"shutdown");

        //claim operator role of pool registry
        bytes memory data = abi.encodeWithSelector(bytes4(keccak256("setOperator(address)")), address(this));
        _proxyCall(poolRegistry,data);
    }

    //set fees on user vaults
    function setPoolFees(uint256 _cvxfxs, uint256 _cvx, uint256 _platform) external onlyOwner{
        require(!isShutdown,"shutdown");

        bytes memory data = abi.encodeWithSelector(bytes4(keccak256("setFees(uint256,uint256,uint256)")), _cvxfxs, _cvx, _platform);
        _proxyCall(feeRegistry,data);
    }

    //set fee deposit address for all user vaults
    function setPoolFeeDeposit(address _deposit) external onlyOwner{
        require(!isShutdown,"shutdown");

        bytes memory data = abi.encodeWithSelector(bytes4(keccak256("setDepositAddress(address)")), _deposit);
        _proxyCall(feeRegistry,data);
    }

    //add pool on registry
    function addPool(address _implementation, address _stakingAddress, address _stakingToken) external onlyPoolManager{
        IPoolRegistry(poolRegistry).addPool(_implementation, _stakingAddress, _stakingToken);
    }

    //set a new reward pool implementation for future pools
    function setPoolRewardImplementation(address _impl) external onlyPoolManager{
        IPoolRegistry(poolRegistry).setRewardImplementation(_impl);
    }

    //deactivate a pool
    function deactivatePool(uint256 _pid) external onlyPoolManager{
        IPoolRegistry(poolRegistry).deactivatePool(_pid);
    }

    //set extra reward contracts to be active when pools are created
    function setRewardActiveOnCreation(bool _active) external onlyPoolManager{
        IPoolRegistry(poolRegistry).setRewardActiveOnCreation(_active);
    }

    //vote for gauge weights
    function voteGaugeWeight(address _controller, address[] calldata _gauge, uint256[] calldata _weight) external onlyOwner{
        for(uint256 i = 0; i < _gauge.length; ){
            bytes memory data = abi.encodeWithSelector(bytes4(keccak256("vote_for_gauge_weights(address,uint256)")), _gauge[i], _weight[i]);
            _proxyCall(_controller,data);
            unchecked{ ++i; }
        }
    }

    //set voting delegate
    function setDelegate(address _delegateContract, address _delegate, bytes32 _space) external onlyOwner{
        bytes memory data = abi.encodeWithSelector(bytes4(keccak256("setDelegate(bytes32,address)")), _space, _delegate);
        _proxyCall(_delegateContract,data);
        emit DelegateSet(_delegate);
    }

    //recover tokens on this contract
    function recoverERC20(address _tokenAddress, uint256 _tokenAmount, address _withdrawTo) external onlyOwner{
        IERC20(_tokenAddress).safeTransfer(_withdrawTo, _tokenAmount);
        emit Recovered(_tokenAddress, _tokenAmount);
    }

    //manually set vefxs proxy for a given vault
    function setVeFXSProxy(address _vault, address _newproxy) external{
        require(!isShutdown,"shutdown");

        //get owner of vault
        address vaultOwner = IProxyVault(_vault).owner();

        //require vault owner or convex admin to call
        require(vaultOwner == msg.sender || owner == msg.sender, "!auth" );

        //require new proxy to be known
        require(proxyOwners[_newproxy] != address(0),"!proxy");
        
        //call checkpoint to checkpoint rewards with current boost
        bytes memory data = abi.encodeWithSelector(bytes4(keccak256("checkpointRewards()")));
        _proxyCall(_vault,data);

        //get current proxy
        address currentProxy = IProxyVault(_vault).usingProxy();

        //tell current proxy admin to remove
        if(currentProxy == proxy){
            //proxy is currently convex, call internal
            data = abi.encodeWithSelector(bytes4(keccak256("proxyToggleStaker(address)")), _vault);
            _proxyCall(IProxyVault(_vault).stakingAddress(),data);
        }else{
            //get proxy owner from list
            IProxyOwner(proxyOwners[currentProxy]).proxyToggleStaker(_vault);
        }

        //tell next proxy admin to add
        if(_newproxy == proxy){
            //new proxy is convex, call internal
            data = abi.encodeWithSelector(bytes4(keccak256("proxyToggleStaker(address)")), _vault);
            _proxyCall(IProxyVault(_vault).stakingAddress(),data);
        }else{
            //get proxy owner from list
            IProxyOwner(proxyOwners[_newproxy]).proxyToggleStaker(_vault);
        }


        //set proxy on vault
        data = abi.encodeWithSelector(bytes4(keccak256("setVeFXSProxy(address)")), _newproxy);
        _proxyCall(_vault,data);

        //call get rewards to checkpoint with new boosted weight
        //should be a bit cheaper than call above since there should be no token transfers in second call
        data = abi.encodeWithSelector(bytes4(keccak256("checkpointRewards()")));
        _proxyCall(_vault,data);

    }

    //recover tokens on the proxy
    function recoverERC20FromProxy(address _tokenAddress, uint256 _tokenAmount, address _withdrawTo) external onlyOwner{

        bytes memory data = abi.encodeWithSelector(bytes4(keccak256("transfer(address,uint256)")), _withdrawTo, _tokenAmount);
        _proxyCall(_tokenAddress,data);

        emit Recovered(_tokenAddress, _tokenAmount);
    }

    //////// End Owner Section ///////////


    function createVault(uint256 _pid) external returns (address){
    	//create minimal proxy vault for specified pool
        (address vault, address stakeAddress, address stakeToken, address rewards) = IPoolRegistry(poolRegistry).addUserVault(_pid, msg.sender);

    	//make voterProxy call proxyToggleStaker(vault) on the pool's stakingAddress to set it as a proxied child
        bytes memory data = abi.encodeWithSelector(bytes4(keccak256("proxyToggleStaker(address)")), vault);
        _proxyCall(stakeAddress,data);

    	//call proxy initialize
        IProxyVault(vault).initialize(msg.sender, stakeAddress, stakeToken, rewards);

        //set vault vefxs proxy
        data = abi.encodeWithSelector(bytes4(keccak256("setVeFXSProxy(address)")), proxy);
        _proxyCall(vault,data);

        return vault;
    }


    //claim fees - if set, move to a fee queue that rewards can pull from
    function claimFees(address _distroContract, address _token) external {
        require(feeclaimer == address(0) || feeclaimer == msg.sender, "!auth");
        require(feeClaimMap[_distroContract][_token],"!claimPair");

        uint256 bal;
        if(feeQueue != address(0)){
            bal = IStaker(proxy).claimFees(_distroContract, _token, feeQueue);
        }else{
            bal = IStaker(proxy).claimFees(_distroContract, _token, address(this));
        }
        emit FeesClaimed(bal);
    }

    //call vefxs checkpoint
    function checkpointFeeRewards(address _distroContract) external {
        require(feeclaimer == address(0) || feeclaimer == msg.sender, "!auth");

        IStaker(proxy).checkpointFeeRewards(_distroContract);
    }

    
    /* ========== EVENTS ========== */
    event SetPendingOwner(address indexed _address);
    event OwnerChanged(address indexed _address);
    event FeeQueueChanged(address indexed _address);
    event FeeClaimerChanged(address indexed _address);
    event FeeClaimPairSet(address indexed _address, address indexed _token, bool _value);
    event ProxyOwnerSet(address indexed _address, address _owner);
    event RewardManagerChanged(address indexed _address);
    event PoolManagerChanged(address indexed _address);
    event Shutdown();
    event DelegateSet(address indexed _address);
    event FeesClaimed(uint256 _amount);
    event Recovered(address indexed _token, uint256 _amount);
}
// File: /contracts/interfaces/IStaker.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

interface IStaker{
    function createLock(uint256, uint256) external returns (bool);
    function increaseAmount(uint256) external returns (bool);
    function increaseTime(uint256) external returns (bool);
    function release() external returns (bool);
    function checkpointFeeRewards(address) external;
    function claimFees(address,address,address) external returns (uint256);
    function voteGaugeWeight(address,uint256) external returns (bool);
    function operator() external view returns (address);
    function execute(address _to, uint256 _value, bytes calldata _data) external returns (bool, bytes memory);
}
// File: /contracts/interfaces/IProxyVault.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

interface IProxyVault {

    enum VaultType{
        Erc20Baic,
        UniV3,
        Convex,
        Erc20Joint
    }

    function initialize(address _owner, address _stakingAddress, address _stakingToken, address _rewardsAddress) external;
    function usingProxy() external returns(address);
    function owner() external returns(address);
    function stakingAddress() external returns(address);
    function rewards() external returns(address);
    function getReward() external;
    function getReward(bool _claim) external;
    function getReward(bool _claim, address[] calldata _rewardTokenList) external;
    function earned() external view returns (address[] memory token_addresses, uint256[] memory total_earned);
}
// File: /contracts/interfaces/IProxyOwner.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

interface IProxyOwner {
    function proxyToggleStaker(address _vault) external;
}
// File: /contracts/interfaces/IPoolRegistry.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

interface IPoolRegistry {
    function poolLength() external view returns(uint256);
    function poolInfo(uint256 _pid) external view returns(address, address, address, uint8);
    function vaultMap(uint256 _pid, address _user) external view returns(address vault);
    function addUserVault(uint256 _pid, address _user) external returns(address vault, address stakeAddress, address stakeToken, address rewards);
    function deactivatePool(uint256 _pid) external;
    function addPool(address _implementation, address _stakingAddress, address _stakingToken) external;
    function setRewardActiveOnCreation(bool _active) external;
    function setRewardImplementation(address _imp) external;
}
// 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/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/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);
}