pragma solidity 0.7.0;
pragma experimental ABIEncoderV2;
import "@openzeppelin/contracts/access/AccessControl.sol";
import "./utils/Pausable.sol";
import "./utils/SafeMath.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, SafeMath {
    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, msg.sender) || hasRole(RELAYER_ROLE, msg.sender),
            "sender is not relayer or admin");
    }
    function _onlyAdmin() private {
        require(hasRole(DEFAULT_ADMIN_ROLE, msg.sender), "sender doesn't have admin role");
    }
    function _onlyRelayers() private {
        require(hasRole(RELAYER_ROLE, msg.sender), "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) public {
        _chainID = chainID;
        _relayerThreshold = initialRelayerThreshold;
        _fee = fee;
        _expiry = expiry;
        _setupRole(DEFAULT_ADMIN_ROLE, msg.sender);
        _setRoleAdmin(RELAYER_ROLE, DEFAULT_ADMIN_ROLE);
        uint initialRelayerCount = initialRelayers.length;
        for (uint i; i < initialRelayerCount; 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 {msg.sender} 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, msg.sender);
    }
    /**
        @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 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 adminSetDecimals(address handlerAddress, address tokenAddress, uint8 srcDecimals, uint8 destDecimals) external onlyAdmin {
        IERCHandler handler = IERCHandler(handlerAddress);
        handler.setDecimals(tokenAddress, srcDecimals, destDecimals);
    }
    /**
        @notice Sets a initial deposit nonce for dest chan, this is used to migrate to a new bridge contract.
        @param chainId Dest chain id.
        @param depositNonce Initial deposit nonce.
     */
    function adminSetDepositNonce(uint8 chainId, uint64 depositNonce) external onlyAdmin {
        _depositCounts[chainId] = depositNonce;
    }
    /**
        @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 calldata data) external payable 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, msg.sender, data);
        emit Deposit(destinationChainID, resourceID, depositNonce);
    }
    /**
        @notice When called, {msg.sender} 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 {msg.sender} 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];
        require(_resourceIDToHandlerAddress[resourceID] != address(0), "no handler for resourceID");
        require(uint(proposal._status) <= 1, "proposal already passed/executed/cancelled");
        require(!_hasVotedOnProposal[nonceAndID][dataHash][msg.sender], "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] = msg.sender;
            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(msg.sender);
            }
        }
        if (proposal._status != ProposalStatus.Cancelled) {
            _hasVotedOnProposal[nonceAndID][dataHash][msg.sender] = 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 calldata data, bytes32 resourceID) external 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.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 {
        require(addrs.length == amounts.length, "length of address and amounts dismatch");
        uint addrCount = addrs.length;
        for (uint i = 0; i < addrCount; 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;
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());
        }
    }
}
// SPDX-License-Identifier: MIT
pragma solidity 0.7.0;
/**
 * @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 SafeMath {
    /**
     * @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 _sub(a, b, "SafeMath: subtraction overflow");
    }
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * 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);
        uint256 c = a - b;
        return c;
    }
}// SPDX-License-Identifier: MIT
pragma solidity 0.7.0;
/**
 * @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 () {
        _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);
    }
}pragma solidity 0.7.0;
/**
    @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;
}pragma solidity 0.7.0;
/**
    @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 Set {contractAddress} decimals on dest chain.
        @param contractAddress Address of contract to be used when making or executing deposits.
        @param srcDecimals Decimals of this token on source chain
        @param destDecimals Decimals of this token on dest chain.
     */
    function setDecimals(address contractAddress, uint8 srcDecimals, uint8 destDecimals) 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;
}
pragma solidity 0.7.0;
/**
    @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 0.7.0;
/**
    @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);
}

pragma solidity 0.7.0;
pragma experimental ABIEncoderV2;
import "../interfaces/IDepositExecute.sol";
import "./HandlerHelpers.sol";
import "../ERC20Safe.sol";
import "@openzeppelin/contracts/presets/ERC20PresetMinterPauser.sol";
import "@openzeppelin/contracts/math/SafeMath.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 {
    using SafeMath for uint256;
    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;
    event Deposited(address indexed token, address indexed recipient, uint256 amount);
    event Withdrawn(address indexed token, address indexed depositer, uint256 amount);
    /**
        @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;
        uint256 initialCount = initialResourceIDs.length;
        for (uint256 i = 0; i < initialCount; i++) {
            _setResource(initialResourceIDs[i], initialContractAddresses[i]);
        }
        uint256 burnableCount = burnableContractAddresses.length;
        for (uint256 i = 0; i < burnableCount; 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(), 0xE4) // 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,
            toDestBalance(tokenAddress, amount)
        );
        emit Withdrawn(tokenAddress, 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), toSrcBalance(tokenAddress, amount));
        } else {
            releaseERC20(tokenAddress, address(recipientAddress), toSrcBalance(tokenAddress, amount));
        }
        emit Deposited(tokenAddress, address(recipientAddress), toSrcBalance(tokenAddress, 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);
    }
    function toDestBalance(address tokenAddress, uint256 amount) internal returns(uint256) {
        Decimals memory decimals = _decimals[tokenAddress];
        // We are not allowed decimals not set or not set correctly
        require(decimals.srcDecimals != 0 && decimals.destDecimals != 0, "Wrong decimals");
        if (decimals.destDecimals >= decimals.srcDecimals) {
            return amount.mul(10 ** (decimals.destDecimals - decimals.srcDecimals));
        } else {
            return amount.div(10 ** (decimals.srcDecimals - decimals.destDecimals));
        }
    }
    function toSrcBalance(address tokenAddress, uint256 amount) internal returns(uint256) {
        Decimals memory decimals = _decimals[tokenAddress];
        // We are not allowed decimals not set or not set correctly
        require(decimals.srcDecimals != 0 && decimals.destDecimals != 0, "Wrong decimals");
        if (decimals.destDecimals >= decimals.srcDecimals) {
            return amount.div(10 ** (decimals.destDecimals - decimals.srcDecimals));
        } else {
            return amount.mul(10 ** (decimals.srcDecimals - decimals.destDecimals));
        }
    }
}
// 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());
        }
    }
}
pragma solidity 0.7.0;
/**
    @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 Set {contractAddress} decimals on dest chain.
        @param contractAddress Address of contract to be used when making or executing deposits.
        @param srcDecimals Decimals of this token on source chain
        @param destDecimals Decimals of this token on dest chain.
     */
    function setDecimals(address contractAddress, uint8 srcDecimals, uint8 destDecimals) 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;
}
pragma solidity 0.7.0;
/**
    @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 0.7.0;
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 {
    struct Decimals {
        uint8 srcDecimals;
        uint8 destDecimals;
    }
    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;
    // token contract address => decimals
    mapping (address => Decimals) public _decimals;
    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 First verifies {contractAddress} is whitelisted, then sets {_decimals}[{contractAddress}]
        to it's decimals value.
        @param contractAddress Address of contract to be used when making or eexcuting deposits.
        @param srcDecimals Decimals of this token on source chain
        @param destDecimals Decimals of this token on dest chain.
     */
    function setDecimals(address contractAddress, uint8 srcDecimals, uint8 destDecimals) external override onlyBridge {
        _setDecimals(contractAddress, srcDecimals, destDecimals);
    }
    /**
        @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;
    }
    function _setDecimals(address contractAddress, uint8 srcDecimals, uint8 destDecimals) internal {
        require(_contractWhitelist[contractAddress], "provided contract is not whitelisted");
        _decimals[contractAddress] = Decimals({
            srcDecimals: srcDecimals,
            destDecimals: destDecimals
        });
    }
}
pragma solidity 0.7.0;
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 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");
        }
    }
}

pragma solidity ^0.5.0;


contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

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);
}

library SafeMath {
    /**
     * @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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @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) {
        // 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 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts 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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message 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.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts 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) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

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

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view 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 returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

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

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public 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 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 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 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 {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _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 {
        require(account != address(0), "ERC20: mint to the zero address");

        _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 {
        require(account != address(0), "ERC20: burn from the zero address");

        _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 is 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 {
        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 Destroys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See {_burn} and {_approve}.
     */
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
    }
}

contract ERC20Detailed is IERC20 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for `name`, `symbol`, and `decimals`. All three of
     * these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }

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

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view 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.
     *
     * 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 returns (uint8) {
        return _decimals;
    }
}

contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

library Roles {
    struct Role {
        mapping (address => bool) bearer;
    }

    /**
     * @dev Give an account access to this role.
     */
    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    /**
     * @dev Remove an account's access to this role.
     */
    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    /**
     * @dev Check if an account has this role.
     * @return bool
     */
    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0), "Roles: account is the zero address");
        return role.bearer[account];
    }
}

contract PauserRole is Context {
    using Roles for Roles.Role;

    event PauserAdded(address indexed account);
    event PauserRemoved(address indexed account);

    Roles.Role private _pausers;

    constructor () internal {
        _addPauser(_msgSender());
    }

    modifier onlyPauser() {
        require(isPauser(_msgSender()), "PauserRole: caller does not have the Pauser role");
        _;
    }

    function isPauser(address account) public view returns (bool) {
        return _pausers.has(account);
    }

    function addPauser(address account) public onlyPauser {
        _addPauser(account);
    }

    function renouncePauser() public {
        _removePauser(_msgSender());
    }

    function _addPauser(address account) internal {
        _pausers.add(account);
        emit PauserAdded(account);
    }

    function _removePauser(address account) internal {
        _pausers.remove(account);
        emit PauserRemoved(account);
    }
}

contract Pausable is Context, PauserRole {
    /**
     * @dev Emitted when the pause is triggered by a pauser (`account`).
     */
    event Paused(address account);

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

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state. Assigns the Pauser role
     * to the deployer.
     */
    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.
     */
    modifier whenNotPaused() {
        require(!_paused, "Pausable: paused");
        _;
    }

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

    /**
     * @dev Called by a pauser to pause, triggers stopped state.
     */
    function pause() public onlyPauser whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Called by a pauser to unpause, returns to normal state.
     */
    function unpause() public onlyPauser whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

contract OwnedPausalbe is Pausable, Ownable {
    modifier onlyOwnerOrNotPaused() {
        if (!isOwner()) {
            require(!paused(), "Pausable: paused");
        }
        _;
    }
}

contract PHAToken is ERC20, ERC20Detailed, OwnedPausalbe {
    constructor(uint256 initialSupply) ERC20Detailed("Phala", "PHA", 18) public {
        _mint(msg.sender, initialSupply);
        pause();
    }

    function transfer(address to, uint256 value) public onlyOwnerOrNotPaused returns (bool) {
        return super.transfer(to, value);
    }

    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        if (from != owner()) {
            require(!paused(), "Pausable: paused");
        }
        return super.transferFrom(from, to, value);
    }

    function approve(address spender, uint256 value) public onlyOwnerOrNotPaused returns (bool) {
        return super.approve(spender, value);
    }

    function increaseAllowance(address spender, uint256 addedValue) public onlyOwnerOrNotPaused returns (bool) {
        return super.increaseAllowance(spender, addedValue);
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public onlyOwnerOrNotPaused returns (bool) {
        return super.decreaseAllowance(spender, subtractedValue);
    }
}