pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;
import "./Bridge.sol";
contract MainnetBridge is Bridge {
 
  // The mainnet bridge isn't altered at all.
  // However we need to call the _deposit and _executeProposal functions
  // that have been made internal.
  constructor (uint8 chainID, address[] memory initialRelayers, uint initialRelayerThreshold, uint256 fee, uint256 expiry, address forwarder) Bridge(chainID, initialRelayers, initialRelayerThreshold, fee, expiry, forwarder) public {}
  function deposit(uint8 destinationChainID, bytes32 resourceID, bytes calldata data) external whenNotPaused {
    _deposit(destinationChainID, resourceID, data);
  }
  function executeProposal(uint8 chainID, uint64 depositNonce, bytes calldata data, bytes32 resourceID) external onlyRelayers whenNotPaused {
    _executeProposal(chainID, depositNonce, data, resourceID);
  }
}// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
import "@openzeppelin/contracts/math/SafeMath.sol";
////
// NOTE: This has been edited to use OZ's SafeMath while
// preserving the ability to inherit from it.
// This is a shim to keep most of Chainbridge's code intact.
////
import "@openzeppelin/contracts/math/SafeMath.sol";
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * note that this is a stripped down version of open zeppelin's safemath
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/SafeMath.sol
 */
contract SafeMathBase {
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
      return SafeMath.sub(a, b);
    }
}// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;
/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This is a stripped down version of Open zeppelin's Pausable contract.
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/EnumerableSet.sol
 *
 */
contract Pausable {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);
    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);
    bool private _paused;
    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor () internal {
        _paused = false;
    }
    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view returns (bool) {
        return _paused;
    }
    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        _whenNotPaused();
        _;
    }
    function _whenNotPaused() private view {
        require(!_paused, "Pausable: paused");
    }
    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenPaused() {
        _whenPaused();
        _;
    }
    function _whenPaused() private view {
        require(_paused, "Pausable: not paused");
    }
    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(msg.sender);
    }
    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(msg.sender);
    }
}// This code was taken from the chainbridge-solidity project listed below,
// licensed under MIT. Slight modifications (downgraded to 0.6.0), branched from
// the v4.0.1 tag. 
// 
// https://github.com/OpenZeppelin/openzeppelin-contracts/
pragma solidity ^0.6.0;
import "@openzeppelin/contracts/utils/Context.sol";
/*
 * @dev Context variant with ERC2771 support.
 */
contract ERC2771Context is Context {
    address immutable _trustedForwarder;
    constructor(address trustedForwarder) internal {
        _trustedForwarder = trustedForwarder;
    }
    function isTrustedForwarder(address forwarder) public view virtual returns(bool) {
        return forwarder == _trustedForwarder;
    }
    function _msgSender() internal view virtual override(Context) returns (address payable sender) {
        if (isTrustedForwarder(msg.sender)) {
            // The assembly code is more direct than the Solidity version using `abi.decode`.
            assembly { sender := shr(96, calldataload(sub(calldatasize(), 20))) }
        } else {
            return super._msgSender();
        }
    }
    function _msgData() internal view virtual override(Context) returns (bytes memory) {
        if (isTrustedForwarder(msg.sender)) {
            return bytes(msg.data[:msg.data.length-20]);
        } else {
            return super._msgData();
        }
    }
}// This code was taken from the chainbridge-solidity project listed below,
// licensed under MIT. Branched from the v3.0.1 tag.
// We've replaced use of msgSender with msg.sender everywhere. We need to do this because we use access control in the 
// constructor of Bridge.sol but _msgSender() cannot be called from a constructor as it accesses `immutable` vars.
// https://forum.openzeppelin.com/t/erc2771context-typeerror-immutable-variables-cannot-be-read-during-contract-creation-time/8513
// Also removed inheritance of Context.sol since we dont need it now.
// Note that since we've replaced _msgSender with msg.sender in here care should
// be take when using a Forwarder contract to call functions in this method. In this
// case the msg.sender will be the Forwarder contract instead of the admin. 
// 
// https://github.com/OpenZeppelin/openzeppelin-contracts/
pragma solidity ^0.6.0;
import "@openzeppelin/contracts/utils/EnumerableSet.sol";
import "@openzeppelin/contracts/utils/Address.sol";
/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * 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 {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;
    struct RoleData {
        EnumerableSet.AddressSet members;
        bytes32 adminRole;
    }
    mapping (bytes32 => RoleData) private _roles;
    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
    /**
     * @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 Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }
    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }
    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }
    /**
     * @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 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 {
        require(hasRole(_roles[role].adminRole, msg.sender), "AccessControl: sender must be an admin to grant");
        _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 {
        require(hasRole(_roles[role].adminRole, msg.sender), "AccessControl: sender must be an admin to revoke");
        _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 {
        require(account == msg.sender, "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.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        _roles[role].adminRole = adminRole;
    }
    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, msg.sender);
        }
    }
    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, msg.sender);
        }
    }
}// This code was taken from the chainbridge-solidity project listed below,
// licensed under GPL v3. We've made slight modifications, branched from
// the v1.0.0 tag. 
// 
// https://github.com/ChainSafe/chainbridge-solidity.git
pragma solidity ^0.6.0;
/**
    @title Interface for handler that handles generic deposits and deposit executions.
    @author ChainSafe Systems.
 */
interface IGenericHandler {
    /**
        @notice Correlates {resourceID} with {contractAddress}, {depositFunctionSig}, and {executeFunctionSig}.
        @param resourceID ResourceID to be used when making deposits.
        @param contractAddress Address of contract to be called when a deposit is made and a deposited is executed.
        @param depositFunctionSig Function signature of method to be called in {contractAddress} when a deposit is made.
        @param executeFunctionSig Function signature of method to be called in {contractAddress} when a deposit is executed.
     */
    function setResource(bytes32 resourceID, address contractAddress, bytes4 depositFunctionSig, bytes4 executeFunctionSig) external;
}// This code was taken from the chainbridge-solidity project listed below,
// licensed under GPL v3. We've made slight modifications, branched from
// the v1.0.0 tag. 
// 
// https://github.com/ChainSafe/chainbridge-solidity.git
pragma solidity ^0.6.0;
/**
    @title Interface to be used with handlers that support ERC20s and ERC721s.
    @author ChainSafe Systems.
 */
interface IERCHandler {
    /**
        @notice Correlates {resourceID} with {contractAddress}.
        @param resourceID ResourceID to be used when making deposits.
        @param contractAddress Address of contract to be called when a deposit is made and a deposited is executed.
     */
    function setResource(bytes32 resourceID, address contractAddress) external;
    /**
        @notice Marks {contractAddress} as mintable/burnable.
        @param contractAddress Address of contract to be used when making or executing deposits.
     */
    function setBurnable(address contractAddress) external;
    /**
        @notice Used to manually release funds from ERC safes.
        @param tokenAddress Address of token contract to release.
        @param recipient Address to release tokens to.
        @param amountOrTokenID Either the amount of ERC20 tokens or the ERC721 token ID to release.
     */
    function withdraw(address tokenAddress, address recipient, uint256 amountOrTokenID) external;
}
// This code was taken from the chainbridge-solidity project listed below,
// licensed under GPL v3. We've made slight modifications, branched from
// the v1.0.0 tag. 
// 
// https://github.com/ChainSafe/chainbridge-solidity.git
pragma solidity ^0.6.0;
/**
    @title Interface for handler contracts that support deposits and deposit executions.
    @author ChainSafe Systems.
 */
interface IDepositExecute {
    /**
        @notice It is intended that deposit are made using the Bridge contract.
        @param destinationChainID Chain ID deposit is expected to be bridged to.
        @param depositNonce This value is generated as an ID by the Bridge contract.
        @param depositer Address of account making the deposit in the Bridge contract.
        @param data Consists of additional data needed for a specific deposit.
     */
    function deposit(bytes32 resourceID, uint8 destinationChainID, uint64 depositNonce, address depositer, bytes calldata data) external;
    /**
        @notice It is intended that proposals are executed by the Bridge contract.
        @param data Consists of additional data needed for a specific deposit execution.
     */
    function executeProposal(bytes32 resourceID, bytes calldata data) external;
}
// This code was taken from the chainbridge-solidity project listed below,
// licensed under GPL v3. We've made slight modifications, branched from
// the v1.0.0 tag. 
// 
// https://github.com/ChainSafe/chainbridge-solidity.git
pragma solidity ^0.6.0;
/**
    @title Interface for Bridge contract.
    @author ChainSafe Systems.
 */
interface IBridge {
    /**
        @notice Exposing getter for {_chainID} instead of forcing the use of call.
        @return uint8 The {_chainID} that is currently set for the Bridge contract.
     */
    function _chainID() external returns (uint8);
}// This code was taken from the chainbridge-solidity project listed below,
// licensed under GPL v3. We've made slight modifications, branched from
// the v1.0.0 tag. 
// 
// https://github.com/ChainSafe/chainbridge-solidity.git
pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;
import "./utils/AccessControl.sol";
import "./utils/SafeMathBase.sol";
import "./utils/Pausable.sol";
import "./utils/ERC2771Context.sol";
import "./interfaces/IDepositExecute.sol";
import "./interfaces/IBridge.sol";
import "./interfaces/IERCHandler.sol";
import "./interfaces/IGenericHandler.sol";
/**
    @title Facilitates deposits, creation and votiing of deposit proposals, and deposit executions.
    @author ChainSafe Systems.
 */
contract Bridge is Pausable, AccessControl, SafeMathBase, ERC2771Context {
    uint8   public _chainID;
    uint256 public _relayerThreshold;
    uint256 public _totalRelayers;
    uint256 public _totalProposals;
    uint256 public _fee;
    uint256 public _expiry;
    enum Vote {No, Yes}
    enum ProposalStatus {Inactive, Active, Passed, Executed, Cancelled}
    struct Proposal {
        bytes32 _resourceID;
        bytes32 _dataHash;
        address[] _yesVotes;
        address[] _noVotes;
        ProposalStatus _status;
        uint256 _proposedBlock;
    }
    // destinationChainID => number of deposits
    mapping(uint8 => uint64) public _depositCounts;
    // resourceID => handler address
    mapping(bytes32 => address) public _resourceIDToHandlerAddress;
    // depositNonce => destinationChainID => bytes
    mapping(uint64 => mapping(uint8 => bytes)) public _depositRecords;
    // destinationChainID + depositNonce => dataHash => Proposal
    mapping(uint72 => mapping(bytes32 => Proposal)) public _proposals;
    // destinationChainID + depositNonce => dataHash => relayerAddress => bool
    mapping(uint72 => mapping(bytes32 => mapping(address => bool))) public _hasVotedOnProposal;
    event RelayerThresholdChanged(uint indexed newThreshold);
    event RelayerAdded(address indexed relayer);
    event RelayerRemoved(address indexed relayer);
    event Deposit(
        uint8   indexed destinationChainID,
        bytes32 indexed resourceID,
        uint64  indexed depositNonce
    );
    event ProposalEvent(
        uint8           indexed originChainID,
        uint64          indexed depositNonce,
        ProposalStatus  indexed status,
        bytes32 resourceID,
        bytes32 dataHash
    );
    event ProposalVote(
        uint8   indexed originChainID,
        uint64  indexed depositNonce,
        ProposalStatus indexed status,
        bytes32 resourceID
    );
    bytes32 public constant RELAYER_ROLE = keccak256("RELAYER_ROLE");
    modifier onlyAdmin() {
        _onlyAdmin();
        _;
    }
    modifier onlyAdminOrRelayer() {
        _onlyAdminOrRelayer();
        _;
    }
    modifier onlyRelayers() {
        _onlyRelayers();
        _;
    }
    function _onlyAdminOrRelayer() private {
        require(hasRole(DEFAULT_ADMIN_ROLE, _msgSender()) || hasRole(RELAYER_ROLE, _msgSender()),
            "sender is not relayer or admin");
    }
    function _onlyAdmin() private {
        require(hasRole(DEFAULT_ADMIN_ROLE, _msgSender()), "sender doesn't have admin role");
    }
    function _onlyRelayers() private {
        require(hasRole(RELAYER_ROLE, _msgSender()), "sender doesn't have relayer role");
    }
    /**
        @notice Initializes Bridge, creates and grants {msg.sender} the admin role,
        creates and grants {initialRelayers} the relayer role.
        @param chainID ID of chain the Bridge contract exists on.
        @param initialRelayers Addresses that should be initially granted the relayer role.
        @param initialRelayerThreshold Number of votes needed for a deposit proposal to be considered passed.
     */
    constructor (
        uint8 chainID, 
        address[] memory initialRelayers, 
        uint initialRelayerThreshold, 
        uint256 fee, 
        uint256 expiry,
        address forwarder
    ) ERC2771Context(forwarder) public {
        _chainID = chainID;
        _relayerThreshold = initialRelayerThreshold;
        _fee = fee;
        _expiry = expiry;
        _setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
        _setRoleAdmin(RELAYER_ROLE, DEFAULT_ADMIN_ROLE);
        for (uint i; i < initialRelayers.length; i++) {
            grantRole(RELAYER_ROLE, initialRelayers[i]);
            _totalRelayers++;
        }
    }
    /**
        @notice Returns true if {relayer} has the relayer role.
        @param relayer Address to check.
     */
    function isRelayer(address relayer) external view returns (bool) {
        return hasRole(RELAYER_ROLE, relayer);
    }
    /**
        @notice Removes admin role from {_msgSender()} and grants it to {newAdmin}.
        @notice Only callable by an address that currently has the admin role.
        @param newAdmin Address that admin role will be granted to.
     */
    function renounceAdmin(address newAdmin) external onlyAdmin {
        grantRole(DEFAULT_ADMIN_ROLE, newAdmin);
        renounceRole(DEFAULT_ADMIN_ROLE, _msgSender());
    }
    /**
        @notice Pauses deposits, proposal creation and voting, and deposit executions.
        @notice Only callable by an address that currently has the admin role.
     */
    function adminPauseTransfers() external onlyAdmin {
        _pause();
    }
    /**
        @notice Unpauses deposits, proposal creation and voting, and deposit executions.
        @notice Only callable by an address that currently has the admin role.
     */
    function adminUnpauseTransfers() external onlyAdmin {
        _unpause();
    }
    /**
        @notice Modifies the number of votes required for a proposal to be considered passed.
        @notice Only callable by an address that currently has the admin role.
        @param newThreshold Value {_relayerThreshold} will be changed to.
        @notice Emits {RelayerThresholdChanged} event.
     */
    function adminChangeRelayerThreshold(uint newThreshold) external onlyAdmin {
        _relayerThreshold = newThreshold;
        emit RelayerThresholdChanged(newThreshold);
    }
    /**
        @notice Grants {relayerAddress} the relayer role and increases {_totalRelayer} count.
        @notice Only callable by an address that currently has the admin role.
        @param relayerAddress Address of relayer to be added.
        @notice Emits {RelayerAdded} event.
     */
    function adminAddRelayer(address relayerAddress) external onlyAdmin {
        require(!hasRole(RELAYER_ROLE, relayerAddress), "addr already has relayer role!");
        grantRole(RELAYER_ROLE, relayerAddress);
        emit RelayerAdded(relayerAddress);
        _totalRelayers++;
    }
    /**
        @notice Removes relayer role for {relayerAddress} and decreases {_totalRelayer} count.
        @notice Only callable by an address that currently has the admin role.
        @param relayerAddress Address of relayer to be removed.
        @notice Emits {RelayerRemoved} event.
     */
    function adminRemoveRelayer(address relayerAddress) external onlyAdmin {
        require(hasRole(RELAYER_ROLE, relayerAddress), "addr doesn't have relayer role!");
        revokeRole(RELAYER_ROLE, relayerAddress);
        emit RelayerRemoved(relayerAddress);
        _totalRelayers--;
    }
    /**
        @notice Sets a new resource for handler contracts that use the IERCHandler interface,
        and maps the {handlerAddress} to {resourceID} in {_resourceIDToHandlerAddress}.
        @notice Only callable by an address that currently has the admin role.
        @param handlerAddress Address of handler resource will be set for.
        @param resourceID ResourceID to be used when making deposits.
        @param tokenAddress Address of contract to be called when a deposit is made and a deposited is executed.
     */
    function adminSetResource(address handlerAddress, bytes32 resourceID, address tokenAddress) external onlyAdmin {
        _resourceIDToHandlerAddress[resourceID] = handlerAddress;
        IERCHandler handler = IERCHandler(handlerAddress);
        handler.setResource(resourceID, tokenAddress);
    }
    /**
        @notice Sets a new resource for handler contracts that use the IGenericHandler interface,
        and maps the {handlerAddress} to {resourceID} in {_resourceIDToHandlerAddress}.
        @notice Only callable by an address that currently has the admin role.
        @param handlerAddress Address of handler resource will be set for.
        @param resourceID ResourceID to be used when making deposits.
        @param contractAddress Address of contract to be called when a deposit is made and a deposited is executed.
     */
    function adminSetGenericResource(
        address handlerAddress,
        bytes32 resourceID,
        address contractAddress,
        bytes4 depositFunctionSig,
        bytes4 executeFunctionSig
    ) external onlyAdmin {
        _resourceIDToHandlerAddress[resourceID] = handlerAddress;
        IGenericHandler handler = IGenericHandler(handlerAddress);
        handler.setResource(resourceID, contractAddress, depositFunctionSig, executeFunctionSig);
    }
    /**
        @notice Sets a resource as burnable for handler contracts that use the IERCHandler interface.
        @notice Only callable by an address that currently has the admin role.
        @param handlerAddress Address of handler resource will be set for.
        @param tokenAddress Address of contract to be called when a deposit is made and a deposited is executed.
     */
    function adminSetBurnable(address handlerAddress, address tokenAddress) external onlyAdmin {
        IERCHandler handler = IERCHandler(handlerAddress);
        handler.setBurnable(tokenAddress);
    }
    /**
        @notice Returns a proposal.
        @param originChainID Chain ID deposit originated from.
        @param depositNonce ID of proposal generated by proposal's origin Bridge contract.
        @param dataHash Hash of data to be provided when deposit proposal is executed.
        @return Proposal which consists of:
        - _dataHash Hash of data to be provided when deposit proposal is executed.
        - _yesVotes Number of votes in favor of proposal.
        - _noVotes Number of votes against proposal.
        - _status Current status of proposal.
     */
    function getProposal(uint8 originChainID, uint64 depositNonce, bytes32 dataHash) external view returns (Proposal memory) {
        uint72 nonceAndID = (uint72(depositNonce) << 8) | uint72(originChainID);
        return _proposals[nonceAndID][dataHash];
    }
    /**
        @notice Changes deposit fee.
        @notice Only callable by admin.
        @param newFee Value {_fee} will be updated to.
     */
    function adminChangeFee(uint newFee) external onlyAdmin {
        require(_fee != newFee, "Current fee is equal to new fee");
        _fee = newFee;
    }
    /**
        @notice Used to manually withdraw funds from ERC safes.
        @param handlerAddress Address of handler to withdraw from.
        @param tokenAddress Address of token to withdraw.
        @param recipient Address to withdraw tokens to.
        @param amountOrTokenID Either the amount of ERC20 tokens or the ERC721 token ID to withdraw.
     */
    function adminWithdraw(
        address handlerAddress,
        address tokenAddress,
        address recipient,
        uint256 amountOrTokenID
    ) external onlyAdmin {
        IERCHandler handler = IERCHandler(handlerAddress);
        handler.withdraw(tokenAddress, recipient, amountOrTokenID);
    }
    /**
        @notice Initiates a transfer using a specified handler contract.
        @notice Only callable when Bridge is not paused.
        @param destinationChainID ID of chain deposit will be bridged to.
        @param resourceID ResourceID used to find address of handler to be used for deposit.
        @param data Additional data to be passed to specified handler.
        @notice Emits {Deposit} event.
     */
    function _deposit(uint8 destinationChainID, bytes32 resourceID, bytes memory data) internal whenNotPaused {
        require(msg.value == _fee, "Incorrect fee supplied");
        address handler = _resourceIDToHandlerAddress[resourceID];
        require(handler != address(0), "resourceID not mapped to handler");
        uint64 depositNonce = ++_depositCounts[destinationChainID];
        _depositRecords[depositNonce][destinationChainID] = data;
        IDepositExecute depositHandler = IDepositExecute(handler);
        depositHandler.deposit(resourceID, destinationChainID, depositNonce, _msgSender(), data);
        emit Deposit(destinationChainID, resourceID, depositNonce);
    }
    /**
        @notice When called, {_msgSender()} will be marked as voting in favor of proposal.
        @notice Only callable by relayers when Bridge is not paused.
        @param chainID ID of chain deposit originated from.
        @param depositNonce ID of deposited generated by origin Bridge contract.
        @param dataHash Hash of data provided when deposit was made.
        @notice Proposal must not have already been passed or executed.
        @notice {_msgSender()} must not have already voted on proposal.
        @notice Emits {ProposalEvent} event with status indicating the proposal status.
        @notice Emits {ProposalVote} event.
     */
    function voteProposal(uint8 chainID, uint64 depositNonce, bytes32 resourceID, bytes32 dataHash) external onlyRelayers whenNotPaused {
        uint72 nonceAndID = (uint72(depositNonce) << 8) | uint72(chainID);
        Proposal storage proposal = _proposals[nonceAndID][dataHash];
        address msgSender = _msgSender();
        require(_resourceIDToHandlerAddress[resourceID] != address(0), "no handler for resourceID");
        require(uint(proposal._status) <= 1, "proposal already passed/executed/cancelled");
        require(!_hasVotedOnProposal[nonceAndID][dataHash][msgSender], "relayer already voted");
        if (uint(proposal._status) == 0) {
            ++_totalProposals;
            _proposals[nonceAndID][dataHash] = Proposal({
                _resourceID : resourceID,
                _dataHash : dataHash,
                _yesVotes : new address[](1),
                _noVotes : new address[](0),
                _status : ProposalStatus.Active,
                _proposedBlock : block.number
                });
            proposal._yesVotes[0] = msgSender;
            emit ProposalEvent(chainID, depositNonce, ProposalStatus.Active, resourceID, dataHash);
        } else {
            if (sub(block.number, proposal._proposedBlock) > _expiry) {
                // if the number of blocks that has passed since this proposal was
                // submitted exceeds the expiry threshold set, cancel the proposal
                proposal._status = ProposalStatus.Cancelled;
                emit ProposalEvent(chainID, depositNonce, ProposalStatus.Cancelled, resourceID, dataHash);
            } else {
                require(dataHash == proposal._dataHash, "datahash mismatch");
                proposal._yesVotes.push(msgSender);
            }
        }
        if (proposal._status != ProposalStatus.Cancelled) {
            _hasVotedOnProposal[nonceAndID][dataHash][msgSender] = true;
            emit ProposalVote(chainID, depositNonce, proposal._status, resourceID);
            // If _depositThreshold is set to 1, then auto finalize
            // or if _relayerThreshold has been exceeded
            if (_relayerThreshold <= 1 || proposal._yesVotes.length >= _relayerThreshold) {
                proposal._status = ProposalStatus.Passed;
                emit ProposalEvent(chainID, depositNonce, ProposalStatus.Passed, resourceID, dataHash);
            }
        }
    }
    /**
        @notice Executes a deposit proposal that is considered passed using a specified handler contract.
        @notice Only callable by relayers when Bridge is not paused.
        @param chainID ID of chain deposit originated from.
        @param depositNonce ID of deposited generated by origin Bridge contract.
        @param dataHash Hash of data originally provided when deposit was made.
        @notice Proposal must be past expiry threshold.
        @notice Emits {ProposalEvent} event with status {Cancelled}.
     */
    function cancelProposal(uint8 chainID, uint64 depositNonce, bytes32 dataHash) public onlyAdminOrRelayer {
        uint72 nonceAndID = (uint72(depositNonce) << 8) | uint72(chainID);
        Proposal storage proposal = _proposals[nonceAndID][dataHash];
        require(proposal._status != ProposalStatus.Cancelled, "Proposal already cancelled");
        require(sub(block.number, proposal._proposedBlock) > _expiry, "Proposal not at expiry threshold");
        proposal._status = ProposalStatus.Cancelled;
        emit ProposalEvent(chainID, depositNonce, ProposalStatus.Cancelled, proposal._resourceID, proposal._dataHash);
    }
    /**
        @notice Executes a deposit proposal that is considered passed using a specified handler contract.
        @notice Only callable by relayers when Bridge is not paused.
        @param chainID ID of chain deposit originated from.
        @param resourceID ResourceID to be used when making deposits.
        @param depositNonce ID of deposited generated by origin Bridge contract.
        @param data Data originally provided when deposit was made.
        @notice Proposal must have Passed status.
        @notice Hash of {data} must equal proposal's {dataHash}.
        @notice Emits {ProposalEvent} event with status {Executed}.
     */
    function _executeProposal(uint8 chainID, uint64 depositNonce, bytes memory data, bytes32 resourceID) internal onlyRelayers whenNotPaused {
        address handler = _resourceIDToHandlerAddress[resourceID];
        uint72 nonceAndID = (uint72(depositNonce) << 8) | uint72(chainID);
        bytes32 dataHash = keccak256(abi.encodePacked(handler, data));
        Proposal storage proposal = _proposals[nonceAndID][dataHash];
        require(proposal._status != ProposalStatus.Inactive, "proposal is not active");
        require(proposal._status == ProposalStatus.Passed, "proposal already transferred");
        require(dataHash == proposal._dataHash, "data doesn't match datahash");
        proposal._status = ProposalStatus.Executed;
        IDepositExecute depositHandler = IDepositExecute(_resourceIDToHandlerAddress[proposal._resourceID]);
        depositHandler.executeProposal(proposal._resourceID, data);
        emit ProposalEvent(chainID, depositNonce, proposal._status, proposal._resourceID, proposal._dataHash);
    }
    /**
        @notice Transfers eth in the contract to the specified addresses. The parameters addrs and amounts are mapped 1-1.
        This means that the address at index 0 for addrs will receive the amount (in WEI) from amounts at index 0.
        @param addrs Array of addresses to transfer {amounts} to.
        @param amounts Array of amonuts to transfer to {addrs}.
     */
    function transferFunds(address payable[] calldata addrs, uint[] calldata amounts) external onlyAdmin {
        for (uint i = 0; i < addrs.length; i++) {
            addrs[i].transfer(amounts[i]);
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.
    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];
        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.
            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;
            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.
            bytes32 lastvalue = set._values[lastIndex];
            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based
            // Delete the slot where the moved value was stored
            set._values.pop();
            // Delete the index for the deleted slot
            delete set._indexes[value];
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }
    // Bytes32Set
    struct Bytes32Set {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }
    // AddressSet
    struct AddressSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }
    // UintSet
    struct UintSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <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 GSN 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 payable) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.2 <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);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;
import "../interfaces/IDepositExecute.sol";
import "./HandlerHelpers.sol";
import "../ERC20Safe.sol";
import "@openzeppelin/contracts/presets/ERC20PresetMinterPauser.sol";
/**
    @title Handles ERC20 deposits and deposit executions.
    @author ChainSafe Systems.
    @notice This contract is intended to be used with the Bridge contract.
 */
contract ERC20Handler is IDepositExecute, HandlerHelpers, ERC20Safe {
    struct DepositRecord {
        address _tokenAddress;
        uint8    _lenDestinationRecipientAddress;
        uint8   _destinationChainID;
        bytes32 _resourceID;
        bytes   _destinationRecipientAddress;
        address _depositer;
        uint    _amount;
    }
    // depositNonce => Deposit Record
    mapping (uint8 => mapping(uint64 => DepositRecord)) public _depositRecords;
    /**
        @param bridgeAddress Contract address of previously deployed Bridge.
        @param initialResourceIDs Resource IDs are used to identify a specific contract address.
        These are the Resource IDs this contract will initially support.
        @param initialContractAddresses These are the addresses the {initialResourceIDs} will point to, and are the contracts that will be
        called to perform various deposit calls.
        @param burnableContractAddresses These addresses will be set as burnable and when {deposit} is called, the deposited token will be burned.
        When {executeProposal} is called, new tokens will be minted.
        @dev {initialResourceIDs} and {initialContractAddresses} must have the same length (one resourceID for every address).
        Also, these arrays must be ordered in the way that {initialResourceIDs}[0] is the intended resourceID for {initialContractAddresses}[0].
     */
    constructor(
        address          bridgeAddress,
        bytes32[] memory initialResourceIDs,
        address[] memory initialContractAddresses,
        address[] memory burnableContractAddresses
    ) public {
        require(initialResourceIDs.length == initialContractAddresses.length,
            "initialResourceIDs and initialContractAddresses len mismatch");
        _bridgeAddress = bridgeAddress;
        for (uint256 i = 0; i < initialResourceIDs.length; i++) {
            _setResource(initialResourceIDs[i], initialContractAddresses[i]);
        }
        for (uint256 i = 0; i < burnableContractAddresses.length; i++) {
            _setBurnable(burnableContractAddresses[i]);
        }
    }
    /**
        @param depositNonce This ID will have been generated by the Bridge contract.
        @param destId ID of chain deposit will be bridged to.
        @return DepositRecord which consists of:
        - _tokenAddress Address used when {deposit} was executed.
        - _destinationChainID ChainID deposited tokens are intended to end up on.
        - _resourceID ResourceID used when {deposit} was executed.
        - _lenDestinationRecipientAddress Used to parse recipient's address from {_destinationRecipientAddress}
        - _destinationRecipientAddress Address tokens are intended to be deposited to on desitnation chain.
        - _depositer Address that initially called {deposit} in the Bridge contract.
        - _amount Amount of tokens that were deposited.
    */
    function getDepositRecord(uint64 depositNonce, uint8 destId) external view returns (DepositRecord memory) {
        return _depositRecords[destId][depositNonce];
    }
    /**
        @notice A deposit is initiatied by making a deposit in the Bridge contract.
        @param destinationChainID Chain ID of chain tokens are expected to be bridged to.
        @param depositNonce This value is generated as an ID by the Bridge contract.
        @param depositer Address of account making the deposit in the Bridge contract.
        @param data Consists of: {resourceID}, {amount}, {lenRecipientAddress}, and {recipientAddress}
        all padded to 32 bytes.
        @notice Data passed into the function should be constructed as follows:
        amount                      uint256     bytes   0 - 32
        recipientAddress length     uint256     bytes  32 - 64
        recipientAddress            bytes       bytes  64 - END
        @dev Depending if the corresponding {tokenAddress} for the parsed {resourceID} is
        marked true in {_burnList}, deposited tokens will be burned, if not, they will be locked.
     */
    function deposit(
        bytes32 resourceID,
        uint8   destinationChainID,
        uint64  depositNonce,
        address depositer,
        bytes   calldata data
    ) external override onlyBridge {
        bytes   memory recipientAddress;
        uint256        amount;
        uint256        lenRecipientAddress;
        assembly {
            amount := calldataload(0xC4)
            recipientAddress := mload(0x40)
            lenRecipientAddress := calldataload(0xE4)
            mstore(0x40, add(0x20, add(recipientAddress, lenRecipientAddress)))
            calldatacopy(
                recipientAddress, // copy to destinationRecipientAddress
                0xE4, // copy from calldata @ 0x104
                sub(calldatasize(), 0xE) // copy size (calldatasize - 0x104)
            )
        }
        address tokenAddress = _resourceIDToTokenContractAddress[resourceID];
        require(_contractWhitelist[tokenAddress], "provided tokenAddress is not whitelisted");
        if (_burnList[tokenAddress]) {
            burnERC20(tokenAddress, depositer, amount);
        } else {
            lockERC20(tokenAddress, depositer, address(this), amount);
        }
        _depositRecords[destinationChainID][depositNonce] = DepositRecord(
            tokenAddress,
            uint8(lenRecipientAddress),
            destinationChainID,
            resourceID,
            recipientAddress,
            depositer,
            amount
        );
    }
    /**
        @notice Proposal execution should be initiated when a proposal is finalized in the Bridge contract.
        by a relayer on the deposit's destination chain.
        @param data Consists of {resourceID}, {amount}, {lenDestinationRecipientAddress},
        and {destinationRecipientAddress} all padded to 32 bytes.
        @notice Data passed into the function should be constructed as follows:
        amount                                 uint256     bytes  0 - 32
        destinationRecipientAddress length     uint256     bytes  32 - 64
        destinationRecipientAddress            bytes       bytes  64 - END
     */
    function executeProposal(bytes32 resourceID, bytes calldata data) external override onlyBridge {
        uint256       amount;
        bytes  memory destinationRecipientAddress;
        assembly {
            amount := calldataload(0x64)
            destinationRecipientAddress := mload(0x40)
            let lenDestinationRecipientAddress := calldataload(0x84)
            mstore(0x40, add(0x20, add(destinationRecipientAddress, lenDestinationRecipientAddress)))
            // in the calldata the destinationRecipientAddress is stored at 0xC4 after accounting for the function signature and length declaration
            calldatacopy(
                destinationRecipientAddress, // copy to destinationRecipientAddress
                0x84, // copy from calldata @ 0x84
                sub(calldatasize(), 0x84) // copy size to the end of calldata
            )
        }
        bytes20 recipientAddress;
        address tokenAddress = _resourceIDToTokenContractAddress[resourceID];
        assembly {
            recipientAddress := mload(add(destinationRecipientAddress, 0x20))
        }
        require(_contractWhitelist[tokenAddress], "provided tokenAddress is not whitelisted");
        if (_burnList[tokenAddress]) {
            mintERC20(tokenAddress, address(recipientAddress), amount);
        } else {
            releaseERC20(tokenAddress, address(recipientAddress), amount);
        }
    }
    /**
        @notice Used to manually release ERC20 tokens from ERC20Safe.
        @param tokenAddress Address of token contract to release.
        @param recipient Address to release tokens to.
        @param amount The amount of ERC20 tokens to release.
     */
    function withdraw(address tokenAddress, address recipient, uint amount) external override onlyBridge {
        releaseERC20(tokenAddress, recipient, amount);
    }
}
// This code was taken from the chainbridge-solidity project listed below,
// licensed under GPL v3. We've made slight modifications, branched from
// the v1.0.0 tag. 
// 
// https://github.com/ChainSafe/chainbridge-solidity.git
pragma solidity ^0.6.0;
/**
    @title Interface to be used with handlers that support ERC20s and ERC721s.
    @author ChainSafe Systems.
 */
interface IERCHandler {
    /**
        @notice Correlates {resourceID} with {contractAddress}.
        @param resourceID ResourceID to be used when making deposits.
        @param contractAddress Address of contract to be called when a deposit is made and a deposited is executed.
     */
    function setResource(bytes32 resourceID, address contractAddress) external;
    /**
        @notice Marks {contractAddress} as mintable/burnable.
        @param contractAddress Address of contract to be used when making or executing deposits.
     */
    function setBurnable(address contractAddress) external;
    /**
        @notice Used to manually release funds from ERC safes.
        @param tokenAddress Address of token contract to release.
        @param recipient Address to release tokens to.
        @param amountOrTokenID Either the amount of ERC20 tokens or the ERC721 token ID to release.
     */
    function withdraw(address tokenAddress, address recipient, uint256 amountOrTokenID) external;
}
// This code was taken from the chainbridge-solidity project listed below,
// licensed under GPL v3. We've made slight modifications, branched from
// the v1.0.0 tag. 
// 
// https://github.com/ChainSafe/chainbridge-solidity.git
pragma solidity ^0.6.0;
/**
    @title Interface for handler contracts that support deposits and deposit executions.
    @author ChainSafe Systems.
 */
interface IDepositExecute {
    /**
        @notice It is intended that deposit are made using the Bridge contract.
        @param destinationChainID Chain ID deposit is expected to be bridged to.
        @param depositNonce This value is generated as an ID by the Bridge contract.
        @param depositer Address of account making the deposit in the Bridge contract.
        @param data Consists of additional data needed for a specific deposit.
     */
    function deposit(bytes32 resourceID, uint8 destinationChainID, uint64 depositNonce, address depositer, bytes calldata data) external;
    /**
        @notice It is intended that proposals are executed by the Bridge contract.
        @param data Consists of additional data needed for a specific deposit execution.
     */
    function executeProposal(bytes32 resourceID, bytes calldata data) external;
}
pragma solidity 0.6.12;
import "../interfaces/IERCHandler.sol";
/**
    @title Function used across handler contracts.
    @author ChainSafe Systems.
    @notice This contract is intended to be used with the Bridge contract.
 */
contract HandlerHelpers is IERCHandler {
    address public _bridgeAddress;
    // resourceID => token contract address
    mapping (bytes32 => address) public _resourceIDToTokenContractAddress;
    // token contract address => resourceID
    mapping (address => bytes32) public _tokenContractAddressToResourceID;
    // token contract address => is whitelisted
    mapping (address => bool) public _contractWhitelist;
    // token contract address => is burnable
    mapping (address => bool) public _burnList;
    modifier onlyBridge() {
        _onlyBridge();
        _;
    }
    function _onlyBridge() private {
        require(msg.sender == _bridgeAddress, "sender must be bridge contract");
    }
    /**
        @notice First verifies {_resourceIDToContractAddress}[{resourceID}] and
        {_contractAddressToResourceID}[{contractAddress}] are not already set,
        then sets {_resourceIDToContractAddress} with {contractAddress},
        {_contractAddressToResourceID} with {resourceID},
        and {_contractWhitelist} to true for {contractAddress}.
        @param resourceID ResourceID to be used when making deposits.
        @param contractAddress Address of contract to be called when a deposit is made and a deposited is executed.
     */
    function setResource(bytes32 resourceID, address contractAddress) external override onlyBridge {
        _setResource(resourceID, contractAddress);
    }
    /**
        @notice First verifies {contractAddress} is whitelisted, then sets {_burnList}[{contractAddress}]
        to true.
        @param contractAddress Address of contract to be used when making or executing deposits.
     */
    function setBurnable(address contractAddress) external override onlyBridge{
        _setBurnable(contractAddress);
    }
    /**
        @notice Used to manually release funds from ERC safes.
        @param tokenAddress Address of token contract to release.
        @param recipient Address to release tokens to.
        @param amountOrTokenID Either the amount of ERC20 tokens or the ERC721 token ID to release.
     */
    function withdraw(address tokenAddress, address recipient, uint256 amountOrTokenID) external virtual override {}
    function _setResource(bytes32 resourceID, address contractAddress) internal {
        _resourceIDToTokenContractAddress[resourceID] = contractAddress;
        _tokenContractAddressToResourceID[contractAddress] = resourceID;
        _contractWhitelist[contractAddress] = true;
    }
    function _setBurnable(address contractAddress) internal {
        require(_contractWhitelist[contractAddress], "provided contract is not whitelisted");
        _burnList[contractAddress] = true;
    }
}
pragma solidity 0.6.12;
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/presets/ERC20PresetMinterPauser.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20Burnable.sol";
/**
    @title Manages deposited ERC20s.
    @author ChainSafe Systems.
    @notice This contract is intended to be used with ERC20Handler contract.
 */
contract ERC20Safe {
    using SafeMath for uint256;
    /**
        @notice Used to transfer tokens into the safe to fund proposals.
        @param tokenAddress Address of ERC20 to transfer.
        @param owner Address of current token owner.
        @param amount Amount of tokens to transfer.
     */
    function fundERC20(address tokenAddress, address owner, uint256 amount) public {
        IERC20 erc20 = IERC20(tokenAddress);
        _safeTransferFrom(erc20, owner, address(this), amount);
    }
    /**
        @notice Used to gain custody of deposited token.
        @param tokenAddress Address of ERC20 to transfer.
        @param owner Address of current token owner.
        @param recipient Address to transfer tokens to.
        @param amount Amount of tokens to transfer.
     */
    function lockERC20(address tokenAddress, address owner, address recipient, uint256 amount) internal {
        IERC20 erc20 = IERC20(tokenAddress);
        _safeTransferFrom(erc20, owner, recipient, amount);
    }
    /**
        @notice Transfers custody of token to recipient.
        @param tokenAddress Address of ERC20 to transfer.
        @param recipient Address to transfer tokens to.
        @param amount Amount of tokens to transfer.
     */
    function releaseERC20(address tokenAddress, address recipient, uint256 amount) internal {
        IERC20 erc20 = IERC20(tokenAddress);
        _safeTransfer(erc20, recipient, amount);
    }
    /**
        @notice Used to create new ERC20s.
        @param tokenAddress Address of ERC20 to transfer.
        @param recipient Address to mint token to.
        @param amount Amount of token to mint.
     */
    function mintERC20(address tokenAddress, address recipient, uint256 amount) internal {
        ERC20PresetMinterPauser erc20 = ERC20PresetMinterPauser(tokenAddress);
        erc20.mint(recipient, amount);
    }
    /**
        @notice Used to burn ERC20s.
        @param tokenAddress Address of ERC20 to burn.
        @param owner Current owner of tokens.
        @param amount Amount of tokens to burn.
     */
    function burnERC20(address tokenAddress, address owner, uint256 amount) internal {
        ERC20Burnable erc20 = ERC20Burnable(tokenAddress);
        erc20.burnFrom(owner, amount);
    }
    /**
        @notice used to transfer ERC20s safely
        @param token Token instance to transfer
        @param to Address to transfer token to
        @param value Amount of token to transfer
     */
    function _safeTransfer(IERC20 token, address to, uint256 value) private {
        _safeCall(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }
    /**
        @notice used to transfer ERC20s safely
        @param token Token instance to transfer
        @param from Address to transfer token from
        @param to Address to transfer token to
        @param value Amount of token to transfer
     */
    function _safeTransferFrom(IERC20 token, address from, address to, uint256 value) private {
        _safeCall(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }
    /**
        @notice used to make calls to ERC20s safely
        @param token Token instance call targets
        @param data encoded call data
     */
    function _safeCall(IERC20 token, bytes memory data) private {        
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "ERC20: call failed");
        if (returndata.length > 0) {
            require(abi.decode(returndata, (bool)), "ERC20: operation did not succeed");
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "./Context.sol";
/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);
    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);
    bool private _paused;
    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor () internal {
        _paused = false;
    }
    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }
    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }
    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }
    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }
    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.
    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];
        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.
            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;
            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.
            bytes32 lastvalue = set._values[lastIndex];
            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based
            // Delete the slot where the moved value was stored
            set._values.pop();
            // Delete the index for the deleted slot
            delete set._indexes[value];
            return true;
        } else {
            return false;
        }
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }
    // Bytes32Set
    struct Bytes32Set {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }
    // AddressSet
    struct AddressSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }
    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }
    // UintSet
    struct UintSet {
        Set _inner;
    }
    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }
    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }
    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }
    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }
   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <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 GSN 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 payable) {
        return msg.sender;
    }
    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.2 <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);
            }
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <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);
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "./ERC20.sol";
import "../../utils/Pausable.sol";
/**
 * @dev ERC20 token with pausable token transfers, minting and burning.
 *
 * Useful for scenarios such as preventing trades until the end of an evaluation
 * period, or having an emergency switch for freezing all token transfers in the
 * event of a large bug.
 */
abstract contract ERC20Pausable is ERC20, Pausable {
    /**
     * @dev See {ERC20-_beforeTokenTransfer}.
     *
     * Requirements:
     *
     * - the contract must not be paused.
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override {
        super._beforeTokenTransfer(from, to, amount);
        require(!paused(), "ERC20Pausable: token transfer while paused");
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "../../utils/Context.sol";
import "./ERC20.sol";
/**
 * @dev Extension of {ERC20} that allows token holders to destroy both their own
 * tokens and those that they have an allowance for, in a way that can be
 * recognized off-chain (via event analysis).
 */
abstract contract ERC20Burnable is Context, ERC20 {
    using SafeMath for uint256;
    /**
     * @dev Destroys `amount` tokens from the caller.
     *
     * See {ERC20-_burn}.
     */
    function burn(uint256 amount) public virtual {
        _burn(_msgSender(), amount);
    }
    /**
     * @dev Destroys `amount` tokens from `account`, deducting from the caller's
     * allowance.
     *
     * See {ERC20-_burn} and {ERC20-allowance}.
     *
     * Requirements:
     *
     * - the caller must have allowance for ``accounts``'s tokens of at least
     * `amount`.
     */
    function burnFrom(address account, uint256 amount) public virtual {
        uint256 decreasedAllowance = allowance(account, _msgSender()).sub(amount, "ERC20: burn amount exceeds allowance");
        _approve(account, _msgSender(), decreasedAllowance);
        _burn(account, amount);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "../../utils/Context.sol";
import "./IERC20.sol";
import "../../math/SafeMath.sol";
/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;
    mapping (address => uint256) private _balances;
    mapping (address => mapping (address => uint256)) private _allowances;
    uint256 private _totalSupply;
    string private _name;
    string private _symbol;
    uint8 private _decimals;
    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }
    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual returns (string memory) {
        return _name;
    }
    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual returns (string memory) {
        return _symbol;
    }
    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual returns (uint8) {
        return _decimals;
    }
    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }
    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }
    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }
    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }
    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }
    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }
    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }
    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }
    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");
        _beforeTokenTransfer(sender, recipient, amount);
        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }
    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");
        _beforeTokenTransfer(address(0), account, amount);
        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }
    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");
        _beforeTokenTransfer(account, address(0), amount);
        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }
    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }
    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "../access/AccessControl.sol";
import "../utils/Context.sol";
import "../token/ERC20/ERC20.sol";
import "../token/ERC20/ERC20Burnable.sol";
import "../token/ERC20/ERC20Pausable.sol";
/**
 * @dev {ERC20} token, including:
 *
 *  - ability for holders to burn (destroy) their tokens
 *  - a minter role that allows for token minting (creation)
 *  - a pauser role that allows to stop all token transfers
 *
 * This contract uses {AccessControl} to lock permissioned functions using the
 * different roles - head to its documentation for details.
 *
 * The account that deploys the contract will be granted the minter and pauser
 * roles, as well as the default admin role, which will let it grant both minter
 * and pauser roles to other accounts.
 */
contract ERC20PresetMinterPauser is Context, AccessControl, ERC20Burnable, ERC20Pausable {
    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
    bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");
    /**
     * @dev Grants `DEFAULT_ADMIN_ROLE`, `MINTER_ROLE` and `PAUSER_ROLE` to the
     * account that deploys the contract.
     *
     * See {ERC20-constructor}.
     */
    constructor(string memory name, string memory symbol) public ERC20(name, symbol) {
        _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
        _setupRole(MINTER_ROLE, _msgSender());
        _setupRole(PAUSER_ROLE, _msgSender());
    }
    /**
     * @dev Creates `amount` new tokens for `to`.
     *
     * See {ERC20-_mint}.
     *
     * Requirements:
     *
     * - the caller must have the `MINTER_ROLE`.
     */
    function mint(address to, uint256 amount) public virtual {
        require(hasRole(MINTER_ROLE, _msgSender()), "ERC20PresetMinterPauser: must have minter role to mint");
        _mint(to, amount);
    }
    /**
     * @dev Pauses all token transfers.
     *
     * See {ERC20Pausable} and {Pausable-_pause}.
     *
     * Requirements:
     *
     * - the caller must have the `PAUSER_ROLE`.
     */
    function pause() public virtual {
        require(hasRole(PAUSER_ROLE, _msgSender()), "ERC20PresetMinterPauser: must have pauser role to pause");
        _pause();
    }
    /**
     * @dev Unpauses all token transfers.
     *
     * See {ERC20Pausable} and {Pausable-_unpause}.
     *
     * Requirements:
     *
     * - the caller must have the `PAUSER_ROLE`.
     */
    function unpause() public virtual {
        require(hasRole(PAUSER_ROLE, _msgSender()), "ERC20PresetMinterPauser: must have pauser role to unpause");
        _unpause();
    }
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override(ERC20, ERC20Pausable) {
        super._beforeTokenTransfer(from, to, amount);
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }
    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }
    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }
    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}
// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
import "../utils/EnumerableSet.sol";
import "../utils/Address.sol";
import "../utils/Context.sol";
/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms.
 *
 * 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 {
    using EnumerableSet for EnumerableSet.AddressSet;
    using Address for address;
    struct RoleData {
        EnumerableSet.AddressSet 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 Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view returns (bool) {
        return _roles[role].members.contains(account);
    }
    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view returns (uint256) {
        return _roles[role].members.length();
    }
    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view returns (address) {
        return _roles[role].members.at(index);
    }
    /**
     * @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 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 {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to grant");
        _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 {
        require(hasRole(_roles[role].adminRole, _msgSender()), "AccessControl: sender must be an admin to revoke");
        _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 {
        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, _roles[role].adminRole, adminRole);
        _roles[role].adminRole = adminRole;
    }
    function _grantRole(bytes32 role, address account) private {
        if (_roles[role].members.add(account)) {
            emit RoleGranted(role, account, _msgSender());
        }
    }
    function _revokeRole(bytes32 role, address account) private {
        if (_roles[role].members.remove(account)) {
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// hevm: flattened sources of /nix/store/8xb41r4qd0cjb63wcrxf1qmfg88p0961-dss-6fd7de0/src/dai.sol
pragma solidity =0.5.12;

////// /nix/store/8xb41r4qd0cjb63wcrxf1qmfg88p0961-dss-6fd7de0/src/lib.sol
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU 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 General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

/* pragma solidity 0.5.12; */

contract LibNote {
    event LogNote(
        bytes4   indexed  sig,
        address  indexed  usr,
        bytes32  indexed  arg1,
        bytes32  indexed  arg2,
        bytes             data
    ) anonymous;

    modifier note {
        _;
        assembly {
            // log an 'anonymous' event with a constant 6 words of calldata
            // and four indexed topics: selector, caller, arg1 and arg2
            let mark := msize                         // end of memory ensures zero
            mstore(0x40, add(mark, 288))              // update free memory pointer
            mstore(mark, 0x20)                        // bytes type data offset
            mstore(add(mark, 0x20), 224)              // bytes size (padded)
            calldatacopy(add(mark, 0x40), 0, 224)     // bytes payload
            log4(mark, 288,                           // calldata
                 shl(224, shr(224, calldataload(0))), // msg.sig
                 caller,                              // msg.sender
                 calldataload(4),                     // arg1
                 calldataload(36)                     // arg2
                )
        }
    }
}

////// /nix/store/8xb41r4qd0cjb63wcrxf1qmfg88p0961-dss-6fd7de0/src/dai.sol
// 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 0.5.12; */

/* import "./lib.sol"; */

contract Dai is LibNote {
    // --- Auth ---
    mapping (address => uint) public wards;
    function rely(address guy) external note auth { wards[guy] = 1; }
    function deny(address guy) external note auth { wards[guy] = 0; }
    modifier auth {
        require(wards[msg.sender] == 1, "Dai/not-authorized");
        _;
    }

    // --- ERC20 Data ---
    string  public constant name     = "Dai Stablecoin";
    string  public constant symbol   = "DAI";
    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, "Dai/insufficient-balance");
        if (src != msg.sender && allowance[src][msg.sender] != uint(-1)) {
            require(allowance[src][msg.sender] >= wad, "Dai/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, "Dai/insufficient-balance");
        if (usr != msg.sender && allowance[usr][msg.sender] != uint(-1)) {
            require(allowance[usr][msg.sender] >= wad, "Dai/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), "Dai/invalid-address-0");
        require(holder == ecrecover(digest, v, r, s), "Dai/invalid-permit");
        require(expiry == 0 || now <= expiry, "Dai/permit-expired");
        require(nonce == nonces[holder]++, "Dai/invalid-nonce");
        uint wad = allowed ? uint(-1) : 0;
        allowance[holder][spender] = wad;
        emit Approval(holder, spender, wad);
    }
}