pragma solidity ^0.4.17;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // assert(b > 0); // Solidity automatically throws when dividing by 0
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}

/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;

    /**
      * @dev The Ownable constructor sets the original `owner` of the contract to the sender
      * account.
      */
    function Ownable() public {
        owner = msg.sender;
    }

    /**
      * @dev Throws if called by any account other than the owner.
      */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
    * @dev Allows the current owner to transfer control of the contract to a newOwner.
    * @param newOwner The address to transfer ownership to.
    */
    function transferOwnership(address newOwner) public onlyOwner {
        if (newOwner != address(0)) {
            owner = newOwner;
        }
    }

}

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20Basic {
    uint public _totalSupply;
    function totalSupply() public constant returns (uint);
    function balanceOf(address who) public constant returns (uint);
    function transfer(address to, uint value) public;
    event Transfer(address indexed from, address indexed to, uint value);
}

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) public constant returns (uint);
    function transferFrom(address from, address to, uint value) public;
    function approve(address spender, uint value) public;
    event Approval(address indexed owner, address indexed spender, uint value);
}

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is Ownable, ERC20Basic {
    using SafeMath for uint;

    mapping(address => uint) public balances;

    // additional variables for use if transaction fees ever became necessary
    uint public basisPointsRate = 0;
    uint public maximumFee = 0;

    /**
    * @dev Fix for the ERC20 short address attack.
    */
    modifier onlyPayloadSize(uint size) {
        require(!(msg.data.length < size + 4));
        _;
    }

    /**
    * @dev transfer token for a specified address
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transfer(address _to, uint _value) public onlyPayloadSize(2 * 32) {
        uint fee = (_value.mul(basisPointsRate)).div(10000);
        if (fee > maximumFee) {
            fee = maximumFee;
        }
        uint sendAmount = _value.sub(fee);
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(sendAmount);
        if (fee > 0) {
            balances[owner] = balances[owner].add(fee);
            Transfer(msg.sender, owner, fee);
        }
        Transfer(msg.sender, _to, sendAmount);
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _owner The address to query the the balance of.
    * @return An uint representing the amount owned by the passed address.
    */
    function balanceOf(address _owner) public constant returns (uint balance) {
        return balances[_owner];
    }

}

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based oncode by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is BasicToken, ERC20 {

    mapping (address => mapping (address => uint)) public allowed;

    uint public constant MAX_UINT = 2**256 - 1;

    /**
    * @dev Transfer tokens from one address to another
    * @param _from address The address which you want to send tokens from
    * @param _to address The address which you want to transfer to
    * @param _value uint the amount of tokens to be transferred
    */
    function transferFrom(address _from, address _to, uint _value) public onlyPayloadSize(3 * 32) {
        var _allowance = allowed[_from][msg.sender];

        // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
        // if (_value > _allowance) throw;

        uint fee = (_value.mul(basisPointsRate)).div(10000);
        if (fee > maximumFee) {
            fee = maximumFee;
        }
        if (_allowance < MAX_UINT) {
            allowed[_from][msg.sender] = _allowance.sub(_value);
        }
        uint sendAmount = _value.sub(fee);
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(sendAmount);
        if (fee > 0) {
            balances[owner] = balances[owner].add(fee);
            Transfer(_from, owner, fee);
        }
        Transfer(_from, _to, sendAmount);
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    * @param _spender The address which will spend the funds.
    * @param _value The amount of tokens to be spent.
    */
    function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {

        // To change the approve amount you first have to reduce the addresses`
        //  allowance to zero by calling `approve(_spender, 0)` if it is not
        //  already 0 to mitigate the race condition described here:
        //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        require(!((_value != 0) && (allowed[msg.sender][_spender] != 0)));

        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
    }

    /**
    * @dev Function to check the amount of tokens than an owner allowed to a spender.
    * @param _owner address The address which owns the funds.
    * @param _spender address The address which will spend the funds.
    * @return A uint specifying the amount of tokens still available for the spender.
    */
    function allowance(address _owner, address _spender) public constant returns (uint remaining) {
        return allowed[_owner][_spender];
    }

}


/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is Ownable {
  event Pause();
  event Unpause();

  bool public paused = false;


  /**
   * @dev Modifier to make a function callable only when the contract is not paused.
   */
  modifier whenNotPaused() {
    require(!paused);
    _;
  }

  /**
   * @dev Modifier to make a function callable only when the contract is paused.
   */
  modifier whenPaused() {
    require(paused);
    _;
  }

  /**
   * @dev called by the owner to pause, triggers stopped state
   */
  function pause() onlyOwner whenNotPaused public {
    paused = true;
    Pause();
  }

  /**
   * @dev called by the owner to unpause, returns to normal state
   */
  function unpause() onlyOwner whenPaused public {
    paused = false;
    Unpause();
  }
}

contract BlackList is Ownable, BasicToken {

    /////// Getters to allow the same blacklist to be used also by other contracts (including upgraded Tether) ///////
    function getBlackListStatus(address _maker) external constant returns (bool) {
        return isBlackListed[_maker];
    }

    function getOwner() external constant returns (address) {
        return owner;
    }

    mapping (address => bool) public isBlackListed;
    
    function addBlackList (address _evilUser) public onlyOwner {
        isBlackListed[_evilUser] = true;
        AddedBlackList(_evilUser);
    }

    function removeBlackList (address _clearedUser) public onlyOwner {
        isBlackListed[_clearedUser] = false;
        RemovedBlackList(_clearedUser);
    }

    function destroyBlackFunds (address _blackListedUser) public onlyOwner {
        require(isBlackListed[_blackListedUser]);
        uint dirtyFunds = balanceOf(_blackListedUser);
        balances[_blackListedUser] = 0;
        _totalSupply -= dirtyFunds;
        DestroyedBlackFunds(_blackListedUser, dirtyFunds);
    }

    event DestroyedBlackFunds(address _blackListedUser, uint _balance);

    event AddedBlackList(address _user);

    event RemovedBlackList(address _user);

}

contract UpgradedStandardToken is StandardToken{
    // those methods are called by the legacy contract
    // and they must ensure msg.sender to be the contract address
    function transferByLegacy(address from, address to, uint value) public;
    function transferFromByLegacy(address sender, address from, address spender, uint value) public;
    function approveByLegacy(address from, address spender, uint value) public;
}

contract TetherToken is Pausable, StandardToken, BlackList {

    string public name;
    string public symbol;
    uint public decimals;
    address public upgradedAddress;
    bool public deprecated;

    //  The contract can be initialized with a number of tokens
    //  All the tokens are deposited to the owner address
    //
    // @param _balance Initial supply of the contract
    // @param _name Token Name
    // @param _symbol Token symbol
    // @param _decimals Token decimals
    function TetherToken(uint _initialSupply, string _name, string _symbol, uint _decimals) public {
        _totalSupply = _initialSupply;
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        balances[owner] = _initialSupply;
        deprecated = false;
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function transfer(address _to, uint _value) public whenNotPaused {
        require(!isBlackListed[msg.sender]);
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).transferByLegacy(msg.sender, _to, _value);
        } else {
            return super.transfer(_to, _value);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function transferFrom(address _from, address _to, uint _value) public whenNotPaused {
        require(!isBlackListed[_from]);
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).transferFromByLegacy(msg.sender, _from, _to, _value);
        } else {
            return super.transferFrom(_from, _to, _value);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function balanceOf(address who) public constant returns (uint) {
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).balanceOf(who);
        } else {
            return super.balanceOf(who);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {
        if (deprecated) {
            return UpgradedStandardToken(upgradedAddress).approveByLegacy(msg.sender, _spender, _value);
        } else {
            return super.approve(_spender, _value);
        }
    }

    // Forward ERC20 methods to upgraded contract if this one is deprecated
    function allowance(address _owner, address _spender) public constant returns (uint remaining) {
        if (deprecated) {
            return StandardToken(upgradedAddress).allowance(_owner, _spender);
        } else {
            return super.allowance(_owner, _spender);
        }
    }

    // deprecate current contract in favour of a new one
    function deprecate(address _upgradedAddress) public onlyOwner {
        deprecated = true;
        upgradedAddress = _upgradedAddress;
        Deprecate(_upgradedAddress);
    }

    // deprecate current contract if favour of a new one
    function totalSupply() public constant returns (uint) {
        if (deprecated) {
            return StandardToken(upgradedAddress).totalSupply();
        } else {
            return _totalSupply;
        }
    }

    // Issue a new amount of tokens
    // these tokens are deposited into the owner address
    //
    // @param _amount Number of tokens to be issued
    function issue(uint amount) public onlyOwner {
        require(_totalSupply + amount > _totalSupply);
        require(balances[owner] + amount > balances[owner]);

        balances[owner] += amount;
        _totalSupply += amount;
        Issue(amount);
    }

    // Redeem tokens.
    // These tokens are withdrawn from the owner address
    // if the balance must be enough to cover the redeem
    // or the call will fail.
    // @param _amount Number of tokens to be issued
    function redeem(uint amount) public onlyOwner {
        require(_totalSupply >= amount);
        require(balances[owner] >= amount);

        _totalSupply -= amount;
        balances[owner] -= amount;
        Redeem(amount);
    }

    function setParams(uint newBasisPoints, uint newMaxFee) public onlyOwner {
        // Ensure transparency by hardcoding limit beyond which fees can never be added
        require(newBasisPoints < 20);
        require(newMaxFee < 50);

        basisPointsRate = newBasisPoints;
        maximumFee = newMaxFee.mul(10**decimals);

        Params(basisPointsRate, maximumFee);
    }

    // Called when new token are issued
    event Issue(uint amount);

    // Called when tokens are redeemed
    event Redeem(uint amount);

    // Called when contract is deprecated
    event Deprecate(address newAddress);

    // Called if contract ever adds fees
    event Params(uint feeBasisPoints, uint maxFee);
}

// SPDX-License-Identifier: AGPL-3.0-or-later
/// vat.sol -- Usdd CDP database
// Copyright (C) 2018 Rain <[email protected]>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
pragma solidity ^0.6.12;
contract Vat {
    // --- Events ---
    event Rely(address usr);
    event Deny(address usr);
    event Hope(address usr);
    event Nope(address usr);
    event Init(bytes32 ilk);
    event File(bytes32 what, uint data);
    event File(bytes32 ilk, bytes32 what, uint data);
    event Cage();
    event Slip(bytes32 ilk, address usr, int256 wad);
    event Flux(bytes32 ilk, address src, address dst, uint256 wad);
    event Move(address src, address dst, uint256 rad);
    event Frob(bytes32 ilk, address urn, address v, address w, int dink, int dart);
    event Fork(bytes32 ilk, address src, address dst, int dink, int dart);
    event Grab(bytes32 i, address u, address v, address w, int dink, int dart);
    event Heal(uint rad);
    event Suck(address u, address v, uint rad);
    event Fold(bytes32 i, address u, int rate);
    // --- Auth ---
    mapping (address => uint) public wards;
    function rely(address usr) external auth { require(live == 1, "Vat/not-live"); wards[usr] = 1; emit Rely(usr); }
    function deny(address usr) external auth { require(live == 1, "Vat/not-live"); wards[usr] = 0; emit Deny(usr); }
    modifier auth {
        require(wards[msg.sender] == 1, "Vat/not-authorized");
        _;
    }
    mapping(address => mapping (address => uint)) public can;
    function hope(address usr) external { can[msg.sender][usr] = 1; emit Hope(usr); }
    function nope(address usr) external { can[msg.sender][usr] = 0; emit Nope(usr); }
    function wish(address bit, address usr) internal view returns (bool) {
        return either(bit == usr, can[bit][usr] == 1);
    }
    // --- Data ---
    struct Ilk {
        uint256 Art;   // Total Normalised Debt     [wad]
        uint256 rate;  // Accumulated Rates         [ray]
        uint256 spot;  // Price with Safety Margin  [ray]
        uint256 line;  // Debt Ceiling              [rad]
        uint256 dust;  // Urn Debt Floor            [rad]
    }
    struct Urn {
        uint256 ink;   // Locked Collateral  [wad]
        uint256 art;   // Normalised Debt    [wad]
    }
    mapping (bytes32 => Ilk)                       public ilks;
    mapping (bytes32 => mapping (address => Urn )) public urns;
    mapping (bytes32 => mapping (address => uint)) public gem;  // [wad]
    mapping (address => uint256)                   public usdd;  // [rad]
    mapping (address => uint256)                   public sin;  // [rad]
    uint256 public debt;  // Total Usdd Issued    [rad]
    uint256 public vice;  // Total Unbacked Usdd  [rad]
    uint256 public Line;  // Total Debt Ceiling  [rad]
    uint256 public live;  // Active Flag
    // --- Init ---
    constructor() public {
        wards[msg.sender] = 1;
        live = 1;
    }
    // --- Math ---
    function _add(uint x, int y) internal pure returns (uint z) {
        z = x + uint(y);
        require(y >= 0 || z <= x);
        require(y <= 0 || z >= x);
    }
    function _sub(uint x, int y) internal pure returns (uint z) {
        z = x - uint(y);
        require(y <= 0 || z <= x);
        require(y >= 0 || z >= x);
    }
    function _mul(uint x, int y) internal pure returns (int z) {
        z = int(x) * y;
        require(int(x) >= 0);
        require(y == 0 || z / y == int(x));
    }
    function _add(uint x, uint y) internal pure returns (uint z) {
        require((z = x + y) >= x);
    }
    function _sub(uint x, uint y) internal pure returns (uint z) {
        require((z = x - y) <= x);
    }
    function _mul(uint x, uint y) internal pure returns (uint z) {
        require(y == 0 || (z = x * y) / y == x);
    }
    // --- Administration ---
    function init(bytes32 ilk) external auth {
        require(ilks[ilk].rate == 0, "Vat/ilk-already-init");
        ilks[ilk].rate = 10 ** 27;
        emit Init(ilk);
    }
    function file(bytes32 what, uint data) external auth {
        require(live == 1, "Vat/not-live");
        if (what == "Line") Line = data;
        else revert("Vat/file-unrecognized-param");
        emit File(what, data);
    }
    function file(bytes32 ilk, bytes32 what, uint data) external auth {
        require(live == 1, "Vat/not-live");
        if (what == "spot") ilks[ilk].spot = data;
        else if (what == "line") ilks[ilk].line = data;
        else if (what == "dust") ilks[ilk].dust = data;
        else revert("Vat/file-unrecognized-param");
        emit File(ilk, what, data);
    }
    function cage() external auth {
        live = 0;
        emit Cage();
    }
    // --- Fungibility ---
    function slip(bytes32 ilk, address usr, int256 wad) external auth {
        gem[ilk][usr] = _add(gem[ilk][usr], wad);
        emit Slip(ilk, usr, wad);
    }
    function flux(bytes32 ilk, address src, address dst, uint256 wad) external {
        require(wish(src, msg.sender), "Vat/not-allowed");
        gem[ilk][src] = _sub(gem[ilk][src], wad);
        gem[ilk][dst] = _add(gem[ilk][dst], wad);
        emit Flux(ilk, src, dst, wad);
    }
    function move(address src, address dst, uint256 rad) external {
        require(wish(src, msg.sender), "Vat/not-allowed");
        usdd[src] = _sub(usdd[src], rad);
        usdd[dst] = _add(usdd[dst], rad);
        emit Move(src, dst, rad);
    }
    function either(bool x, bool y) internal pure returns (bool z) {
        assembly{ z := or(x, y)}
    }
    function both(bool x, bool y) internal pure returns (bool z) {
        assembly{ z := and(x, y)}
    }
    // --- CDP Manipulation ---
    function frob(bytes32 i, address u, address v, address w, int dink, int dart) external {
        // system is live
        require(live == 1, "Vat/not-live");
        Urn memory urn = urns[i][u];
        Ilk memory ilk = ilks[i];
        // ilk has been initialised
        require(ilk.rate != 0, "Vat/ilk-not-init");
        urn.ink = _add(urn.ink, dink);
        urn.art = _add(urn.art, dart);
        ilk.Art = _add(ilk.Art, dart);
        int dtab = _mul(ilk.rate, dart);
        uint tab = _mul(ilk.rate, urn.art);
        debt     = _add(debt, dtab);
        // either debt has decreased, or debt ceilings are not exceeded
        require(either(dart <= 0, both(_mul(ilk.Art, ilk.rate) <= ilk.line, debt <= Line)), "Vat/ceiling-exceeded");
        // urn is either less risky than before, or it is safe
        require(either(both(dart <= 0, dink >= 0), tab <= _mul(urn.ink, ilk.spot)), "Vat/not-safe");
        // urn is either more safe, or the owner consents
        require(either(both(dart <= 0, dink >= 0), wish(u, msg.sender)), "Vat/not-allowed-u");
        // collateral src consents
        require(either(dink <= 0, wish(v, msg.sender)), "Vat/not-allowed-v");
        // debt dst consents
        require(either(dart >= 0, wish(w, msg.sender)), "Vat/not-allowed-w");
        // urn has no debt, or a non-dusty amount
        require(either(urn.art == 0, tab >= ilk.dust), "Vat/dust");
        gem[i][v] = _sub(gem[i][v], dink);
        usdd[w]    = _add(usdd[w],    dtab);
        urns[i][u] = urn;
        ilks[i]    = ilk;
        emit Frob(i, u, v, w, dink, dart);
    }
    // --- CDP Fungibility ---
    function fork(bytes32 ilk, address src, address dst, int dink, int dart) external {
        Urn storage u = urns[ilk][src];
        Urn storage v = urns[ilk][dst];
        Ilk storage i = ilks[ilk];
        u.ink = _sub(u.ink, dink);
        u.art = _sub(u.art, dart);
        v.ink = _add(v.ink, dink);
        v.art = _add(v.art, dart);
        uint utab = _mul(u.art, i.rate);
        uint vtab = _mul(v.art, i.rate);
        // both sides consent
        require(both(wish(src, msg.sender), wish(dst, msg.sender)), "Vat/not-allowed");
        // both sides safe
        require(utab <= _mul(u.ink, i.spot), "Vat/not-safe-src");
        require(vtab <= _mul(v.ink, i.spot), "Vat/not-safe-dst");
        // both sides non-dusty
        require(either(utab >= i.dust, u.art == 0), "Vat/dust-src");
        require(either(vtab >= i.dust, v.art == 0), "Vat/dust-dst");
        emit Fork(ilk, src, dst, dink, dart);
    }
    // --- CDP Confiscation ---
    function grab(bytes32 i, address u, address v, address w, int dink, int dart) external auth {
        Urn storage urn = urns[i][u];
        Ilk storage ilk = ilks[i];
        urn.ink = _add(urn.ink, dink);
        urn.art = _add(urn.art, dart);
        ilk.Art = _add(ilk.Art, dart);
        int dtab = _mul(ilk.rate, dart);
        gem[i][v] = _sub(gem[i][v], dink);
        sin[w]    = _sub(sin[w],    dtab);
        vice      = _sub(vice,      dtab);
        emit Grab(i, u, v, w, dink, dart);
    }
    // --- Settlement ---
    function heal(uint rad) external {
        address u = msg.sender;
        sin[u] = _sub(sin[u], rad);
        usdd[u] = _sub(usdd[u], rad);
        vice   = _sub(vice,   rad);
        debt   = _sub(debt,   rad);
        emit Heal(rad);
    }
    function suck(address u, address v, uint rad) external auth {
        sin[u] = _add(sin[u], rad);
        usdd[v] = _add(usdd[v], rad);
        vice   = _add(vice,   rad);
        debt   = _add(debt,   rad);
        emit Suck(u, v, rad);
    }
    // --- Rates ---
    function fold(bytes32 i, address u, int rate) external auth {
        require(live == 1, "Vat/not-live");
        Ilk storage ilk = ilks[i];
        ilk.rate = _add(ilk.rate, rate);
        int rad  = _mul(ilk.Art, rate);
        usdd[u]   = _add(usdd[u], rad);
        debt     = _add(debt,   rad);
        emit Fold(i, u, rate);
    }
}

// SPDX-License-Identifier: AGPL-3.0-or-later
/// usdd.sol -- Usdd Stablecoin ERC-20 Token
// Copyright (C) 2017, 2018, 2019 dbrock, rain, mrchico
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
pragma solidity ^0.6.12;
contract Usdd {
    // --- Auth ---
    mapping (address => uint) public wards;
    function rely(address guy) external auth { wards[guy] = 1; }
    function deny(address guy) external auth { wards[guy] = 0; }
    modifier auth {
        require(wards[msg.sender] == 1, "Usdd/not-authorized");
        _;
    }
    // --- ERC20 Data ---
    string  public constant name     = "Usdd Stablecoin";
    string  public constant symbol   = "USDD";
    string  public constant version  = "1";
    uint8   public constant decimals = 18;
    uint256 public totalSupply;
    mapping (address => uint)                      public balanceOf;
    mapping (address => mapping (address => uint)) public allowance;
    mapping (address => uint)                      public nonces;
    event Approval(address indexed src, address indexed guy, uint wad);
    event Transfer(address indexed src, address indexed dst, uint wad);
    // --- Math ---
    function add(uint x, uint y) internal pure returns (uint z) {
        require((z = x + y) >= x);
    }
    function sub(uint x, uint y) internal pure returns (uint z) {
        require((z = x - y) <= x);
    }
    // --- EIP712 niceties ---
    bytes32 public DOMAIN_SEPARATOR;
    // bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address holder,address spender,uint256 nonce,uint256 expiry,bool allowed)");
    bytes32 public constant PERMIT_TYPEHASH = 0xea2aa0a1be11a07ed86d755c93467f4f82362b452371d1ba94d1715123511acb;
    constructor(uint256 chainId_) public {
        wards[msg.sender] = 1;
        DOMAIN_SEPARATOR = keccak256(abi.encode(
            keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
            keccak256(bytes(name)),
            keccak256(bytes(version)),
            chainId_,
            address(this)
        ));
    }
    // --- Token ---
    function transfer(address dst, uint wad) external returns (bool) {
        return transferFrom(msg.sender, dst, wad);
    }
    function transferFrom(address src, address dst, uint wad)
        public returns (bool)
    {
        require(balanceOf[src] >= wad, "Usdd/insufficient-balance");
        if (src != msg.sender && allowance[src][msg.sender] != uint(-1)) {
            require(allowance[src][msg.sender] >= wad, "Usdd/insufficient-allowance");
            allowance[src][msg.sender] = sub(allowance[src][msg.sender], wad);
        }
        balanceOf[src] = sub(balanceOf[src], wad);
        balanceOf[dst] = add(balanceOf[dst], wad);
        emit Transfer(src, dst, wad);
        return true;
    }
    function mint(address usr, uint wad) external auth {
        balanceOf[usr] = add(balanceOf[usr], wad);
        totalSupply    = add(totalSupply, wad);
        emit Transfer(address(0), usr, wad);
    }
    function burn(address usr, uint wad) external {
        require(balanceOf[usr] >= wad, "Usdd/insufficient-balance");
        if (usr != msg.sender && allowance[usr][msg.sender] != uint(-1)) {
            require(allowance[usr][msg.sender] >= wad, "Usdd/insufficient-allowance");
            allowance[usr][msg.sender] = sub(allowance[usr][msg.sender], wad);
        }
        balanceOf[usr] = sub(balanceOf[usr], wad);
        totalSupply    = sub(totalSupply, wad);
        emit Transfer(usr, address(0), wad);
    }
    function approve(address usr, uint wad) external returns (bool) {
        allowance[msg.sender][usr] = wad;
        emit Approval(msg.sender, usr, wad);
        return true;
    }
    // --- Alias ---
    function push(address usr, uint wad) external {
        transferFrom(msg.sender, usr, wad);
    }
    function pull(address usr, uint wad) external {
        transferFrom(usr, msg.sender, wad);
    }
    function move(address src, address dst, uint wad) external {
        transferFrom(src, dst, wad);
    }
    // --- Approve by signature ---
    function permit(address holder, address spender, uint256 nonce, uint256 expiry,
                    bool allowed, uint8 v, bytes32 r, bytes32 s) external
    {
        bytes32 digest =
            keccak256(abi.encodePacked(
                "\\x19\\x01",
                DOMAIN_SEPARATOR,
                keccak256(abi.encode(PERMIT_TYPEHASH,
                                     holder,
                                     spender,
                                     nonce,
                                     expiry,
                                     allowed))
        ));
        require(holder != address(0), "Usdd/invalid-address-0");
        require(holder == ecrecover(digest, v, r, s), "Usdd/invalid-permit");
        require(expiry == 0 || now <= expiry, "Usdd/permit-expired");
        require(nonce == nonces[holder]++, "Usdd/invalid-nonce");
        uint wad = allowed ? uint(-1) : 0;
        allowance[holder][spender] = wad;
        emit Approval(holder, spender, wad);
    }
}

// SPDX-License-Identifier: AGPL-3.0-or-later
/// join.sol -- Basic token adapters
// Copyright (C) 2018 Rain <[email protected]>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
pragma solidity ^0.6.12;
interface GemLike {
    function decimals() external view returns (uint);
    function transfer(address,uint) external returns (bool);
    function transferFrom(address,address,uint) external returns (bool);
}
interface DSTokenLike {
    function mint(address,uint) external;
    function burn(address,uint) external;
}
interface VatLike {
    function slip(bytes32,address,int) external;
    function move(address,address,uint) external;
}
/*
    Here we provide *adapters* to connect the Vat to arbitrary external
    token implementations, creating a bounded context for the Vat. The
    adapters here are provided as working examples:
      - `GemJoin`: For well behaved ERC20 tokens, with simple transfer
                   semantics.
      - `ETHJoin`: For native ETH.
      - `UsddJoin`: For connecting internal Usdd balances to an external
                   `DSToken` implementation.
    In practice, adapter implementations will be varied and specific to
    individual collateral types, accounting for different transfer
    semantics and token standards.
    Adapters need to implement two basic methods:
      - `join`: enter collateral into the system
      - `exit`: remove collateral from the system
*/
contract GemJoin {
    // --- Auth ---
    mapping (address => uint) public wards;
    function rely(address usr) external auth {
        wards[usr] = 1;
        emit Rely(usr);
    }
    function deny(address usr) external auth {
        wards[usr] = 0;
        emit Deny(usr);
    }
    modifier auth {
        require(wards[msg.sender] == 1, "GemJoin/not-authorized");
        _;
    }
    VatLike public vat;   // CDP Engine
    bytes32 public ilk;   // Collateral Type
    GemLike public gem;
    uint    public dec;
    uint    public live;  // Active Flag
    // Events
    event Rely(address indexed usr);
    event Deny(address indexed usr);
    event Join(address indexed usr, uint256 wad);
    event Exit(address indexed usr, uint256 wad);
    event Cage();
    constructor(address vat_, bytes32 ilk_, address gem_) public {
        wards[msg.sender] = 1;
        live = 1;
        vat = VatLike(vat_);
        ilk = ilk_;
        gem = GemLike(gem_);
        dec = gem.decimals();
        emit Rely(msg.sender);
    }
    function cage() external auth {
        live = 0;
        emit Cage();
    }
    function join(address usr, uint wad) external {
        require(live == 1, "GemJoin/not-live");
        require(int(wad) >= 0, "GemJoin/overflow");
        vat.slip(ilk, usr, int(wad));
        require(gem.transferFrom(msg.sender, address(this), wad), "GemJoin/failed-transfer");
        emit Join(usr, wad);
    }
    function exit(address usr, uint wad) external {
        require(wad <= 2 ** 255, "GemJoin/overflow");
        vat.slip(ilk, msg.sender, -int(wad));
        require(gem.transfer(usr, wad), "GemJoin/failed-transfer");
        emit Exit(usr, wad);
    }
}
contract ETHJoin {
    // --- Auth ---
    mapping (address => uint) public wards;
    function rely(address usr) external auth {
        wards[usr] = 1;
        emit Rely(usr);
    }
    function deny(address usr) external auth {
        wards[usr] = 0;
        emit Deny(usr);
    }
    modifier auth {
        require(wards[msg.sender] == 1, "ETHJoin/not-authorized");
        _;
    }
    // Events
    event Rely(address indexed usr);
    event Deny(address indexed usr);
    event Join(address indexed usr, uint256 wad);
    event Exit(address indexed usr, uint256 wad);
    event Cage();
    VatLike public vat;
    bytes32 public ilk;
    uint    public live;  // Access Flag
    constructor(address vat_, bytes32 ilk_) public {
        wards[msg.sender] = 1;
        live = 1;
        vat = VatLike(vat_);
        ilk = ilk_;
    }
    function cage() external auth {
        live = 0;
        emit Cage();
    }
    function join(address usr) external payable {
        require(live == 1, "ETHJoin/not-live");
        require(int(msg.value) >= 0, "ETHJoin/overflow");
        vat.slip(ilk, usr, int(msg.value));
        emit Join(usr, msg.value);
    }
    function exit(address payable usr, uint wad) external {
        require(int(wad) >= 0, "ETHJoin/overflow");
        vat.slip(ilk, msg.sender, -int(wad));
        usr.transfer(wad);
        emit Exit(usr, wad);
    }
}
contract UsddJoin {
    // --- Auth ---
    mapping (address => uint) public wards;
    function rely(address usr) external auth {
        wards[usr] = 1;
        emit Rely(usr);
    }
    function deny(address usr) external auth {
        wards[usr] = 0;
        emit Deny(usr);
    }
    modifier auth {
        require(wards[msg.sender] == 1, "UsddJoin/not-authorized");
        _;
    }
    VatLike public vat;      // CDP Engine
    DSTokenLike public usdd;  // Stablecoin Token
    uint    public live;     // Active Flag
    // Events
    event Rely(address indexed usr);
    event Deny(address indexed usr);
    event Join(address indexed usr, uint256 wad);
    event Exit(address indexed usr, uint256 wad);
    event Cage();
    constructor(address vat_, address usdd_) public {
        wards[msg.sender] = 1;
        live = 1;
        vat = VatLike(vat_);
        usdd = DSTokenLike(usdd_);
    }
    function cage() external auth {
        live = 0;
        emit Cage();
    }
    uint constant ONE = 10 ** 27;
    function mul(uint x, uint y) internal pure returns (uint z) {
        require(y == 0 || (z = x * y) / y == x);
    }
    function join(address usr, uint wad) external {
        vat.move(address(this), usr, mul(ONE, wad));
        usdd.burn(msg.sender, wad);
        emit Join(usr, wad);
    }
    function exit(address usr, uint wad) external {
        require(live == 1, "UsddJoin/not-live");
        vat.move(msg.sender, address(this), mul(ONE, wad));
        usdd.mint(usr, wad);
        emit Exit(usr, wad);
    }
}