// File: contracts/PaymentStreamFactory.sol



//SPDX-License-Identifier: MIT

pragma solidity 0.8.3;

import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "./interfaces/IPaymentStreamFactory.sol";
import "./interfaces/ISwapManager.sol";
import "./PaymentStream.sol";

contract PaymentStreamFactory is IPaymentStreamFactory, Ownable {
  address[] private allStreams;
  mapping(address => bool) private isOurs;

  uint256 private constant TWAP_PERIOD = 1 hours;

  uint8 private constant MAX_PATH = 5;

  ISwapManager public swapManager;

  mapping(address => TokenSupport) public supportedTokens; // token address => TokenSupport

  constructor(address _swapManager) {
    swapManager = ISwapManager(_swapManager);
  }

  /**
   * @notice Creates a new payment stream
   * @dev Payer (_msgSender()) is set as admin of "pausableRole", so he can grant and revoke the "pausable" role later on
   * @param _payee address that receives the payment stream
   * @param _usdAmount uint256 total amount in USD (scaled to 18 decimals) to be distributed until endTime
   * @param _token address of the ERC20 token that payee receives as payment
   * @param _fundingAddress address used to withdraw the drip
   * @param _endTime timestamp that sets drip distribution end
   */
  function createStream(
    address _payee,
    uint256 _usdAmount,
    address _token,
    address _fundingAddress,
    uint256 _endTime
  ) external returns (address streamAddress) {
    require(supportedTokens[_token].path.length > 1, "token-not-supported");

    streamAddress = address(
      new PaymentStream(
        _msgSender(),
        _payee,
        _usdAmount,
        _token,
        _fundingAddress,
        _endTime
      )
    );

    allStreams.push(streamAddress);
    isOurs[streamAddress] = true;

    emit StreamCreated(
      allStreams.length - 1,
      streamAddress,
      _msgSender(),
      _payee,
      _usdAmount
    );
  }

  /**
   * @notice Updates Swap Manager contract address
   * @dev Only contract owner can change swapManager
   * @param _newAddress address of new Swap Manager instance
   */
  function updateSwapManager(address _newAddress) external override onlyOwner {
    require(_newAddress != address(0), "invalid-swap-manager-address");
    require(_newAddress != address(swapManager), "same-swap-manager-address");

    emit SwapManagerUpdated(address(swapManager), _newAddress);
    swapManager = ISwapManager(_newAddress);
  }

  /**
   * @notice If caller is contract owner it adds (or updates) Oracle price feed for given token
   * @param _tokenAddress address of the ERC20 token to add support to
   * @param _dex ID for choosing the DEX where prices will be retrieved (0 = Uniswap v2, 1 = Sushiswap)
   * @param _path path of tokens to reach a _tokenAddress from a USD stablecoin (e.g: [ USDC, WETH, VSP ])
   */
  function addToken(
    address _tokenAddress,
    uint8 _dex,
    address[] memory _path
  ) external override onlyOwner {
    TokenSupport memory _tokenSupport;

    uint256 _len = _path.length;

    require(_len > 1 && _len <= MAX_PATH, "invalid-path-length");

    _len--;

    for (uint256 i = 0; i < _len; i++) {
      swapManager.createOrUpdateOracle(
        _path[i],
        _path[i + 1],
        TWAP_PERIOD,
        _dex
      );
    }

    _tokenSupport.path = _path;
    _tokenSupport.dex = _dex;

    supportedTokens[_tokenAddress] = _tokenSupport;

    emit TokenAdded(_tokenAddress);
  }

  /**
   * @notice Converts given amount in usd to target token amount using oracle
   * @param _token address of target token
   * @param _amount amount in USD (scaled to 18 decimals)
   * @return lastPrice target token amount
   */
  function usdToTokenAmount(address _token, uint256 _amount)
    external
    view
    override
    returns (uint256 lastPrice)
  {
    TokenSupport memory _tokenSupport = supportedTokens[_token];

    // _amount is 18 decimals
    // some stablecoins like USDC has 6 decimals, so we scale the amount accordingly

    _amount =
      _amount /
      10**(18 - IERC20Metadata(_tokenSupport.path[0]).decimals());
    uint256 _len = _tokenSupport.path.length - 1;

    for (uint256 i = 0; i < _len; i++) {
      (uint256 amountOut, ) =
        swapManager.consultForFree(
          _tokenSupport.path[i],
          _tokenSupport.path[i + 1],
          (i == 0) ? _amount : lastPrice,
          TWAP_PERIOD,
          _tokenSupport.dex
        );
      lastPrice = amountOut;
    }
  }

  /**
   * @notice Updates price oracles for a given token
   * @param _token address of target token
   */
  function updateOracles(address _token) external override {
    TokenSupport memory _tokenSupport = supportedTokens[_token];

    uint256 _len = _tokenSupport.path.length - 1;

    address[] memory _oracles = new address[](_len);

    for (uint256 i = 0; i < _len; i++) {
      _oracles[i] = swapManager.getOracle(
        _tokenSupport.path[i],
        _tokenSupport.path[i + 1],
        TWAP_PERIOD,
        _tokenSupport.dex
      );
    }

    swapManager.updateOracles(_oracles);
  }

  /**
   * @notice Checks if a address belongs to this contract' streams
   */
  function ours(address _a) external view override returns (bool) {
    return isOurs[_a];
  }

  /**
   * @notice Returns no. of streams stored in contract
   */
  function getStreamsCount() external view override returns (uint256) {
    return allStreams.length;
  }

  /**
   * @notice Returns address of the stream located at given id
   */
  function getStream(uint256 _idx) external view override returns (address) {
    require(_idx < allStreams.length, "index-exceeds-list-length");
    return allStreams[_idx];
  }
}

// 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/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 () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), 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 {
        emit OwnershipTransferred(_owner, address(0));
        _owner = 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");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: contracts/interfaces/IPaymentStreamFactory.sol



//SPDX-License-Identifier: MIT
pragma solidity ^0.8.3;

interface IPaymentStreamFactory {
  struct TokenSupport {
    address[] path;
    uint256 dex;
  }

  event StreamCreated(
    uint256 id,
    address indexed stream,
    address indexed payer,
    address indexed payee,
    uint256 usdAmount
  );

  event TokenAdded(address indexed tokenAddress);

  event SwapManagerUpdated(
    address indexed previousSwapManager,
    address indexed newSwapManager
  );

  function updateSwapManager(address newAddress) external;

  function addToken(
    address _tokenAddress,
    uint8 _dex,
    address[] memory _path
  ) external;

  function updateOracles(address token) external;

  function usdToTokenAmount(address _token, uint256 _amount)
    external
    view
    returns (uint256);

  function ours(address _a) external view returns (bool);

  function getStreamsCount() external view returns (uint256);

  function getStream(uint256 _idx) external view returns (address);
}

// File: contracts/interfaces/ISwapManager.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.3;

import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol";

/* solhint-disable func-name-mixedcase */

interface ISwapManager {
  event OracleCreated(
    address indexed _sender,
    address indexed _newOracle,
    uint256 _period
  );

  function N_DEX() external view returns (uint256);

  function ROUTERS(uint256 i) external view returns (IUniswapV2Router02);

  function bestOutputFixedInput(
    address _from,
    address _to,
    uint256 _amountIn
  )
    external
    view
    returns (
      address[] memory path,
      uint256 amountOut,
      uint256 rIdx
    );

  function bestPathFixedInput(
    address _from,
    address _to,
    uint256 _amountIn,
    uint256 _i
  ) external view returns (address[] memory path, uint256 amountOut);

  function bestInputFixedOutput(
    address _from,
    address _to,
    uint256 _amountOut
  )
    external
    view
    returns (
      address[] memory path,
      uint256 amountIn,
      uint256 rIdx
    );

  function bestPathFixedOutput(
    address _from,
    address _to,
    uint256 _amountOut,
    uint256 _i
  ) external view returns (address[] memory path, uint256 amountIn);

  function safeGetAmountsOut(
    uint256 _amountIn,
    address[] memory _path,
    uint256 _i
  ) external view returns (uint256[] memory result);

  function unsafeGetAmountsOut(
    uint256 _amountIn,
    address[] memory _path,
    uint256 _i
  ) external view returns (uint256[] memory result);

  function safeGetAmountsIn(
    uint256 _amountOut,
    address[] memory _path,
    uint256 _i
  ) external view returns (uint256[] memory result);

  function unsafeGetAmountsIn(
    uint256 _amountOut,
    address[] memory _path,
    uint256 _i
  ) external view returns (uint256[] memory result);

  function comparePathsFixedInput(
    address[] memory pathA,
    address[] memory pathB,
    uint256 _amountIn,
    uint256 _i
  ) external view returns (address[] memory path, uint256 amountOut);

  function comparePathsFixedOutput(
    address[] memory pathA,
    address[] memory pathB,
    uint256 _amountOut,
    uint256 _i
  ) external view returns (address[] memory path, uint256 amountIn);

  function ours(address a) external view returns (bool);

  function oracleCount() external view returns (uint256);

  function oracleAt(uint256 idx) external view returns (address);

  function getOracle(
    address _tokenA,
    address _tokenB,
    uint256 _period,
    uint256 _i
  ) external view returns (address);

  function createOrUpdateOracle(
    address _tokenA,
    address _tokenB,
    uint256 _period,
    uint256 _i
  ) external returns (address oracleAddr);

  function consultForFree(
    address _from,
    address _to,
    uint256 _amountIn,
    uint256 _period,
    uint256 _i
  ) external view returns (uint256 amountOut, uint256 lastUpdatedAt);

  /// get the data we want and pay the gas to update
  function consult(
    address _from,
    address _to,
    uint256 _amountIn,
    uint256 _period,
    uint256 _i
  )
    external
    returns (
      uint256 amountOut,
      uint256 lastUpdatedAt,
      bool updated
    );

  function updateOracles() external returns (uint256 updated, uint256 expected);

  function updateOracles(address[] memory _oracleAddrs)
    external
    returns (uint256 updated, uint256 expected);
}

// File: contracts/PaymentStream.sol



//SPDX-License-Identifier: MIT
pragma solidity 0.8.3;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";
import "./interfaces/IPaymentStream.sol";
import "./interfaces/IPaymentStreamFactory.sol";

contract PaymentStream is AccessControl, IPaymentStream {
  using SafeERC20 for IERC20;

  address public payer;
  address public payee;
  address public token;
  address public fundingAddress;

  uint256 public usdAmount;
  uint256 public startTime;
  uint256 public secs;
  uint256 public usdPerSec;
  uint256 public claimed;

  bool public paused;

  IPaymentStreamFactory public immutable factory;

  bytes32 private constant ADMIN_ROLE = keccak256(abi.encodePacked("admin"));
  bytes32 private constant PAUSABLE_ROLE =
    keccak256(abi.encodePacked("pausable"));

  modifier onlyPayer() {
    require(_msgSender() == payer, "not-stream-owner");
    _;
  }

  modifier onlyPayerOrDelegated() {
    require(
      _msgSender() == payer || hasRole(PAUSABLE_ROLE, _msgSender()),
      "not-stream-owner-or-delegated"
    );
    _;
  }

  modifier onlyPayee() {
    require(_msgSender() == payee, "not-payee");
    _;
  }

  /**
   * @notice Creates a new payment stream
   * @dev Payer is set as admin of "PAUSABLE_ROLE", so he can grant and revoke the "pausable" role later on
   * @param _payer Owner of the stream
   * @param _payee address that receives the payment stream
   * @param _usdAmount uint256 total amount in USD (scaled to 18 decimals) to be distributed until endTime
   * @param _token address of the ERC20 token that payee receives as payment
   * @param _fundingAddress address used to withdraw the drip
   * @param _endTime timestamp that sets drip distribution end
   */
  constructor(
    address _payer,
    address _payee,
    uint256 _usdAmount,
    address _token,
    address _fundingAddress,
    uint256 _endTime
  ) {
    factory = IPaymentStreamFactory(_msgSender());

    require(_endTime > block.timestamp, "invalid-end-time");
    require(_payee != _fundingAddress, "payee-is-funding-address");
    require(
      _payee != address(0) && _fundingAddress != address(0),
      "payee-or-funding-address-is-0"
    );

    require(_usdAmount > 0, "usd-amount-is-0");

    payee = _payee;
    usdAmount = _usdAmount;
    token = _token;
    fundingAddress = _fundingAddress;
    payer = _payer;
    startTime = block.timestamp;
    secs = _endTime - block.timestamp;
    usdPerSec = _usdAmount / secs;

    _setupRole(ADMIN_ROLE, _payer);
    _setRoleAdmin(PAUSABLE_ROLE, ADMIN_ROLE);
  }

  /**
   * @notice Delegates pausable capability to new delegate
   * @dev Only RoleAdmin (Payer) can delegate this capability, tx will revert otherwise
   * @param _delegate address that receives the "PAUSABLE_ROLE"
   */
  function delegatePausable(address _delegate) external override {
    require(_delegate != address(0), "invalid-delegate");

    grantRole(PAUSABLE_ROLE, _delegate);
  }

  /**
   * @notice Revokes pausable capability of a delegate
   * @dev Only RoleAdmin (Payer) can revoke this capability, tx will revert otherwise
   * @param _delegate address that has its "PAUSABLE_ROLE" revoked
   */
  function revokePausable(address _delegate) external override {
    revokeRole(PAUSABLE_ROLE, _delegate);
  }

  /**
   * @notice Pauses a stream if caller is either the payer or a delegate of PAUSABLE_ROLE
   */
  function pauseStream() external override onlyPayerOrDelegated {
    paused = true;
    emit StreamPaused();
  }

  /**
   * @notice Unpauses a stream if caller is either the payer or a delegate of PAUSABLE_ROLE
   */
  function unpauseStream() external override onlyPayerOrDelegated {
    paused = false;
    emit StreamUnpaused();
  }

  /**
   * @notice If caller is the payer of the stream it sets a new address as receiver of the stream
   * @param _newPayee address of new payee
   */
  function updatePayee(address _newPayee) external override onlyPayer {
    require(_newPayee != address(0), "invalid-new-payee");
    require(_newPayee != payee, "same-new-payee");

    _claim();

    emit PayeeUpdated(payee, _newPayee);
    payee = _newPayee;
  }

  /**
   * @notice If caller is the payer of the stream it sets a new address used to withdraw the drip
   * @param _newFundingAddress new address used to withdraw the drip
   */
  function updateFundingAddress(address _newFundingAddress)
    external
    override
    onlyPayer
  {
    require(_newFundingAddress != address(0), "invalid-new-funding-address");
    require(_newFundingAddress != fundingAddress, "same-new-funding-address");

    emit FundingAddressUpdated(fundingAddress, _newFundingAddress);

    fundingAddress = _newFundingAddress;
  }

  /**
   * @notice If caller is the payer it increases or decreases a stream funding rate
   * @dev Any unclaimed drip amount remaining will be claimed on behalf of payee
   * @param _usdAmount uint256 total amount in USD (scaled to 18 decimals) to be distributed until endTime
   * @param _endTime timestamp that sets drip distribution end
   */
  function updateFundingRate(uint256 _usdAmount, uint256 _endTime)
    external
    override
    onlyPayer
  {
    require(_endTime > block.timestamp, "invalid-end-time");

    _claim();

    usdAmount = _usdAmount;
    startTime = block.timestamp;
    secs = _endTime - block.timestamp;
    usdPerSec = _usdAmount / secs;
    claimed = 0;

    emit StreamUpdated(_usdAmount, _endTime);
  }

  /**
   * @notice If caller is the payee of the stream it receives the accrued drip amount
   */
  function claim() external override onlyPayee {
    require(!paused, "stream-is-paused");
    _claim();
  }

  function claimable() external view override returns (uint256) {
    return _claimable();
  }

  /**
   * @notice Helper function, gets the accrued drip of given stream converted into target token amount
   * @return uint256 amount in target token
   */
  function claimableToken() external view override returns (uint256) {
    return factory.usdToTokenAmount(token, _claimable());
  }

  function _claim() internal {
    factory.updateOracles(token);

    uint256 _accumulated = _claimable();

    if (_accumulated == 0) return;

    uint256 _amount = factory.usdToTokenAmount(token, _accumulated);

    // if we get _amount = 0 it means payee called this function
    // before the oracles had time to update for the first time
    require(_amount > 0, "oracle-update-error");

    claimed += _accumulated;

    IERC20(token).safeTransferFrom(fundingAddress, payee, _amount);

    emit Claimed(_accumulated, _amount);
  }

  /**
   * @notice gets the accrued drip of given stream in USD
   * @return uint256 USD amount (scaled to 18 decimals)
   */
  function _claimable() internal view returns (uint256) {
    uint256 _elapsed = block.timestamp - startTime;

    if (_elapsed > secs) {
      return usdAmount - claimed; // no more drips to avoid floating point dust
    }

    return (usdPerSec * _elapsed) - claimed;
  }
}

// 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/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) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol



pragma solidity >=0.6.2;

import './IUniswapV2Router01.sol';

interface IUniswapV2Router02 is IUniswapV2Router01 {
    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountETH);
    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountETH);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable;
    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
}

// File: @uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router01.sol



pragma solidity >=0.6.2;

interface IUniswapV2Router01 {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint amountADesired,
        uint amountBDesired,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB, uint liquidity);
    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETH(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountToken, uint amountETH);
    function removeLiquidityWithPermit(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETHWithPermit(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountToken, uint amountETH);
    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapTokensForExactTokens(
        uint amountOut,
        uint amountInMax,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        payable
        returns (uint[] memory amounts);
    function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
        external
        returns (uint[] memory amounts);
    function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        returns (uint[] memory amounts);
    function swapETHForExactTokens(uint amountOut, address[] calldata path, address to, uint deadline)
        external
        payable
        returns (uint[] memory amounts);

    function quote(uint amountA, uint reserveA, uint reserveB) external pure returns (uint amountB);
    function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) external pure returns (uint amountOut);
    function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut) external pure returns (uint amountIn);
    function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
    function getAmountsIn(uint amountOut, address[] calldata path) external view returns (uint[] memory amounts);
}

// 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'
        // solhint-disable-next-line max-line-length
        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
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../utils/Context.sol";
import "../utils/Strings.sol";
import "../utils/introspection/ERC165.sol";

/**
 * @dev External interface of AccessControl declared to support ERC165 detection.
 */
interface IAccessControl {
    function hasRole(bytes32 role, address account) external view returns (bool);
    function getRoleAdmin(bytes32 role) external view returns (bytes32);
    function grantRole(bytes32 role, address account) external;
    function revokeRole(bytes32 role, address account) external;
    function renounceRole(bytes32 role, address account) external;
}

/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms. This is a lightweight version that doesn't allow enumerating role
 * members except through off-chain means by accessing the contract event logs. Some
 * applications may benefit from on-chain enumerability, for those cases see
 * {AccessControlEnumerable}.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControl is Context, IAccessControl, ERC165 {
    struct RoleData {
        mapping (address => bool) members;
        bytes32 adminRole;
    }

    mapping (bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Modifier that checks that an account has a specific role. Reverts
     * with a standardized message including the required role.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{20}) is missing role (0x[0-9a-f]{32})$/
     *
     * _Available since v4.1._
     */
    modifier onlyRole(bytes32 role) {
        _checkRole(role, _msgSender());
        _;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IAccessControl).interfaceId
            || super.supportsInterface(interfaceId);
    }

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view override returns (bool) {
        return _roles[role].members[account];
    }

    /**
     * @dev Revert with a standard message if `account` is missing `role`.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{20}) is missing role (0x[0-9a-f]{32})$/
     */
    function _checkRole(bytes32 role, address account) internal view {
        if(!hasRole(role, account)) {
            revert(string(abi.encodePacked(
                "AccessControl: account ",
                Strings.toHexString(uint160(account), 20),
                " is missing role ",
                Strings.toHexString(uint256(role), 32)
            )));
        }
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view override returns (bytes32) {
        return _roles[role].adminRole;
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
        _grantRole(role, account);
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
        _revokeRole(role, account);
    }

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) public virtual override {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");

        _revokeRole(role, account);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        emit RoleAdminChanged(role, getRoleAdmin(role), adminRole);
        _roles[role].adminRole = adminRole;
    }

    function _grantRole(bytes32 role, address account) private {
        if (!hasRole(role, account)) {
            _roles[role].members[account] = true;
            emit RoleGranted(role, account, _msgSender());
        }
    }

    function _revokeRole(bytes32 role, address account) private {
        if (hasRole(role, account)) {
            _roles[role].members[account] = false;
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// File: contracts/interfaces/IPaymentStream.sol



//SPDX-License-Identifier: MIT
pragma solidity ^0.8.3;

interface IPaymentStream {
  event Claimed(uint256 usdAmount, uint256 tokenAmount);
  event StreamPaused();
  event StreamUnpaused();
  event StreamUpdated(uint256 usdAmount, uint256 endTime);

  event FundingAddressUpdated(
    address indexed previousFundingAddress,
    address indexed newFundingAddress
  );
  event PayeeUpdated(address indexed previousPayee, address indexed newPayee);

  function claim() external;

  function pauseStream() external;

  function unpauseStream() external;

  function delegatePausable(address delegate) external;

  function revokePausable(address delegate) external;

  function updateFundingRate(uint256 usdAmount, uint256 endTime) external;

  function updateFundingAddress(address newFundingAddress) external;

  function updatePayee(address newPayee) external;

  function claimableToken() external view returns (uint256);

  function claimable() external view returns (uint256);
}

// 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;
        // solhint-disable-next-line no-inline-assembly
        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");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private 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

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant alphabet = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = alphabet[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }

}

// File: @openzeppelin/contracts/utils/introspection/ERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}