/**

Deployed by Ren Project, https://renproject.io

Commit hash: 4021b7f
Repository: https://github.com/renproject/darknode-sol
Issues: https://github.com/renproject/darknode-sol/issues

Licenses
@openzeppelin/contracts: (MIT) https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/LICENSE
darknode-sol: (GNU GPL V3) https://github.com/renproject/darknode-sol/blob/master/LICENSE

*/

pragma solidity 0.5.16;


library SafeMath {
    
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    
    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;
    }

    
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        
        require(b > 0, errorMessage);
        uint256 c = a / b;
        

        return c;
    }

    
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

contract Proxy {
  
  function () payable external {
    _fallback();
  }

  
  function _implementation() internal view returns (address);

  
  function _delegate(address implementation) internal {
    assembly {
      
      
      
      calldatacopy(0, 0, calldatasize)

      
      
      let result := delegatecall(gas, implementation, 0, calldatasize, 0, 0)

      
      returndatacopy(0, 0, returndatasize)

      switch result
      
      case 0 { revert(0, returndatasize) }
      default { return(0, returndatasize) }
    }
  }

  
  function _willFallback() internal {
  }

  
  function _fallback() internal {
    _willFallback();
    _delegate(_implementation());
  }
}

library OpenZeppelinUpgradesAddress {
    
    function isContract(address account) internal view returns (bool) {
        uint256 size;
        
        
        
        
        
        
        
        assembly { size := extcodesize(account) }
        return size > 0;
    }
}

contract BaseUpgradeabilityProxy is Proxy {
  
  event Upgraded(address indexed implementation);

  
  bytes32 internal constant IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;

  
  function _implementation() internal view returns (address impl) {
    bytes32 slot = IMPLEMENTATION_SLOT;
    assembly {
      impl := sload(slot)
    }
  }

  
  function _upgradeTo(address newImplementation) internal {
    _setImplementation(newImplementation);
    emit Upgraded(newImplementation);
  }

  
  function _setImplementation(address newImplementation) internal {
    require(OpenZeppelinUpgradesAddress.isContract(newImplementation), "Cannot set a proxy implementation to a non-contract address");

    bytes32 slot = IMPLEMENTATION_SLOT;

    assembly {
      sstore(slot, newImplementation)
    }
  }
}

contract UpgradeabilityProxy is BaseUpgradeabilityProxy {
  
  constructor(address _logic, bytes memory _data) public payable {
    assert(IMPLEMENTATION_SLOT == bytes32(uint256(keccak256('eip1967.proxy.implementation')) - 1));
    _setImplementation(_logic);
    if(_data.length > 0) {
      (bool success,) = _logic.delegatecall(_data);
      require(success);
    }
  }  
}

contract BaseAdminUpgradeabilityProxy is BaseUpgradeabilityProxy {
  
  event AdminChanged(address previousAdmin, address newAdmin);

  

  bytes32 internal constant ADMIN_SLOT = 0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;

  
  modifier ifAdmin() {
    if (msg.sender == _admin()) {
      _;
    } else {
      _fallback();
    }
  }

  
  function admin() external ifAdmin returns (address) {
    return _admin();
  }

  
  function implementation() external ifAdmin returns (address) {
    return _implementation();
  }

  
  function changeAdmin(address newAdmin) external ifAdmin {
    require(newAdmin != address(0), "Cannot change the admin of a proxy to the zero address");
    emit AdminChanged(_admin(), newAdmin);
    _setAdmin(newAdmin);
  }

  
  function upgradeTo(address newImplementation) external ifAdmin {
    _upgradeTo(newImplementation);
  }

  
  function upgradeToAndCall(address newImplementation, bytes calldata data) payable external ifAdmin {
    _upgradeTo(newImplementation);
    (bool success,) = newImplementation.delegatecall(data);
    require(success);
  }

  
  function _admin() internal view returns (address adm) {
    bytes32 slot = ADMIN_SLOT;
    assembly {
      adm := sload(slot)
    }
  }

  
  function _setAdmin(address newAdmin) internal {
    bytes32 slot = ADMIN_SLOT;

    assembly {
      sstore(slot, newAdmin)
    }
  }

  
  function _willFallback() internal {
    require(msg.sender != _admin(), "Cannot call fallback function from the proxy admin");
    super._willFallback();
  }
}

contract InitializableUpgradeabilityProxy is BaseUpgradeabilityProxy {
  
  function initialize(address _logic, bytes memory _data) public payable {
    require(_implementation() == address(0));
    assert(IMPLEMENTATION_SLOT == bytes32(uint256(keccak256('eip1967.proxy.implementation')) - 1));
    _setImplementation(_logic);
    if(_data.length > 0) {
      (bool success,) = _logic.delegatecall(_data);
      require(success);
    }
  }  
}

contract InitializableAdminUpgradeabilityProxy is BaseAdminUpgradeabilityProxy, InitializableUpgradeabilityProxy {
  
  function initialize(address _logic, address _admin, bytes memory _data) public payable {
    require(_implementation() == address(0));
    InitializableUpgradeabilityProxy.initialize(_logic, _data);
    assert(ADMIN_SLOT == bytes32(uint256(keccak256('eip1967.proxy.admin')) - 1));
    _setAdmin(_admin);
  }
}

contract Initializable {

  
  bool private initialized;

  
  bool private initializing;

  
  modifier initializer() {
    require(initializing || isConstructor() || !initialized, "Contract instance has already been initialized");

    bool isTopLevelCall = !initializing;
    if (isTopLevelCall) {
      initializing = true;
      initialized = true;
    }

    _;

    if (isTopLevelCall) {
      initializing = false;
    }
  }

  
  function isConstructor() private view returns (bool) {
    
    
    
    
    
    address self = address(this);
    uint256 cs;
    assembly { cs := extcodesize(self) }
    return cs == 0;
  }

  
  uint256[50] private ______gap;
}

contract Context is Initializable {
    
    
    constructor () internal { }
    

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

    function _msgData() internal view returns (bytes memory) {
        this; 
        return msg.data;
    }
}

contract Ownable is Initializable, Context {
    address private _owner;

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

    
    function initialize(address sender) public initializer {
        _owner = sender;
        emit OwnershipTransferred(address(0), _owner);
    }

    
    function owner() public view returns (address) {
        return _owner;
    }

    
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }

    
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }

    uint256[50] private ______gap;
}

interface IERC20 {
    
    function totalSupply() external view returns (uint256);

    
    function balanceOf(address account) external view returns (uint256);

    
    function transfer(address recipient, uint256 amount) external returns (bool);

    
    function allowance(address owner, address spender) external view returns (uint256);

    
    function approve(address spender, uint256 amount) external returns (bool);

    
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    
    event Transfer(address indexed from, address indexed to, uint256 value);

    
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

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

    
    function initialize(string memory name, string memory symbol, uint8 decimals) public initializer {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }

    
    function name() public view returns (string memory) {
        return _name;
    }

    
    function symbol() public view returns (string memory) {
        return _symbol;
    }

    
    function decimals() public view returns (uint8) {
        return _decimals;
    }

    uint256[50] private ______gap;
}

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

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

    
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    
    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    
    function approve(address spender, uint256 amount) public returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    
    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;
    }

    
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    
    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);
    }

    
    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);
    }

     
    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);
    }

    
    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);
    }

    
    function _burnFrom(address account, uint256 amount) internal {
        _burn(account, amount);
        _approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
    }

    uint256[50] private ______gap;
}

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

    
    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    
    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    
    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 Initializable, Context {
    using Roles for Roles.Role;

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

    Roles.Role private _pausers;

    function initialize(address sender) public initializer {
        if (!isPauser(sender)) {
            _addPauser(sender);
        }
    }

    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);
    }

    uint256[50] private ______gap;
}

contract Pausable is Initializable, Context, PauserRole {
    
    event Paused(address account);

    
    event Unpaused(address account);

    bool private _paused;

    
    function initialize(address sender) public initializer {
        PauserRole.initialize(sender);

        _paused = false;
    }

    
    function paused() public view returns (bool) {
        return _paused;
    }

    
    modifier whenNotPaused() {
        require(!_paused, "Pausable: paused");
        _;
    }

    
    modifier whenPaused() {
        require(_paused, "Pausable: not paused");
        _;
    }

    
    function pause() public onlyPauser whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    
    function unpause() public onlyPauser whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }

    uint256[50] private ______gap;
}

contract ERC20Pausable is Initializable, ERC20, Pausable {
    function initialize(address sender) public initializer {
        Pausable.initialize(sender);
    }

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

    function transferFrom(address from, address to, uint256 value) public whenNotPaused returns (bool) {
        return super.transferFrom(from, to, value);
    }

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

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

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

    uint256[50] private ______gap;
}

contract ERC20Burnable is Initializable, Context, ERC20 {
    
    function burn(uint256 amount) public {
        _burn(_msgSender(), amount);
    }

    
    function burnFrom(address account, uint256 amount) public {
        _burnFrom(account, amount);
    }

    uint256[50] private ______gap;
}

contract RenToken is Ownable, ERC20Detailed, ERC20Pausable, ERC20Burnable {
    string private constant _name = "REN";
    string private constant _symbol = "REN";
    uint8 private constant _decimals = 18;

    uint256 public constant INITIAL_SUPPLY = 1000000000 *
        10**uint256(_decimals);

    
    constructor() public {
        ERC20Pausable.initialize(msg.sender);
        ERC20Detailed.initialize(_name, _symbol, _decimals);
        Ownable.initialize(msg.sender);
        _mint(msg.sender, INITIAL_SUPPLY);
    }

    function transferTokens(address beneficiary, uint256 amount)
        public
        onlyOwner
        returns (bool)
    {
        
        
        require(amount > 0);

        _transfer(msg.sender, beneficiary, amount);
        emit Transfer(msg.sender, beneficiary, amount);

        return true;
    }
}

contract Claimable is Initializable, Ownable {
    address public pendingOwner;

    function initialize(address _nextOwner) public initializer {
        Ownable.initialize(_nextOwner);
    }

    modifier onlyPendingOwner() {
        require(
            _msgSender() == pendingOwner,
            "Claimable: caller is not the pending owner"
        );
        _;
    }

    function transferOwnership(address newOwner) public onlyOwner {
        require(
            newOwner != owner() && newOwner != pendingOwner,
            "Claimable: invalid new owner"
        );
        pendingOwner = newOwner;
    }

    function claimOwnership() public onlyPendingOwner {
        _transferOwnership(pendingOwner);
        delete pendingOwner;
    }
}

library LinkedList {

    
    address public constant NULL = address(0);

    
    struct Node {
        bool inList;
        address previous;
        address next;
    }

    
    struct List {
        mapping (address => Node) list;
    }

    
    function insertBefore(List storage self, address target, address newNode) internal {
        require(newNode != address(0), "LinkedList: invalid address");
        require(!isInList(self, newNode), "LinkedList: already in list");
        require(isInList(self, target) || target == NULL, "LinkedList: not in list");

        
        address prev = self.list[target].previous;

        self.list[newNode].next = target;
        self.list[newNode].previous = prev;
        self.list[target].previous = newNode;
        self.list[prev].next = newNode;

        self.list[newNode].inList = true;
    }

    
    function insertAfter(List storage self, address target, address newNode) internal {
        require(newNode != address(0), "LinkedList: invalid address");
        require(!isInList(self, newNode), "LinkedList: already in list");
        require(isInList(self, target) || target == NULL, "LinkedList: not in list");

        
        address n = self.list[target].next;

        self.list[newNode].previous = target;
        self.list[newNode].next = n;
        self.list[target].next = newNode;
        self.list[n].previous = newNode;

        self.list[newNode].inList = true;
    }

    
    function remove(List storage self, address node) internal {
        require(isInList(self, node), "LinkedList: not in list");
        
        address p = self.list[node].previous;
        address n = self.list[node].next;

        self.list[p].next = n;
        self.list[n].previous = p;

        
        
        self.list[node].inList = false;
        delete self.list[node];
    }

    
    function prepend(List storage self, address node) internal {
        

        insertBefore(self, begin(self), node);
    }

    
    function append(List storage self, address node) internal {
        

        insertAfter(self, end(self), node);
    }

    function swap(List storage self, address left, address right) internal {
        

        address previousRight = self.list[right].previous;
        remove(self, right);
        insertAfter(self, left, right);
        remove(self, left);
        insertAfter(self, previousRight, left);
    }

    function isInList(List storage self, address node) internal view returns (bool) {
        return self.list[node].inList;
    }

    
    function begin(List storage self) internal view returns (address) {
        return self.list[NULL].next;
    }

    
    function end(List storage self) internal view returns (address) {
        return self.list[NULL].previous;
    }

    function next(List storage self, address node) internal view returns (address) {
        require(isInList(self, node), "LinkedList: not in list");
        return self.list[node].next;
    }

    function previous(List storage self, address node) internal view returns (address) {
        require(isInList(self, node), "LinkedList: not in list");
        return self.list[node].previous;
    }

    function elements(List storage self, address _start, uint256 _count) internal view returns (address[] memory) {
        require(_count > 0, "LinkedList: invalid count");
        require(isInList(self, _start) || _start == address(0), "LinkedList: not in list");
        address[] memory elems = new address[](_count);

        
        uint256 n = 0;
        address nextItem = _start;
        if (nextItem == address(0)) {
            nextItem = begin(self);
        }

        while (n < _count) {
            if (nextItem == address(0)) {
                break;
            }
            elems[n] = nextItem;
            nextItem = next(self, nextItem);
            n += 1;
        }
        return elems;
    }
}

library Address {
    
    function isContract(address account) internal view returns (bool) {
        
        
        

        
        
        
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        
        assembly { codehash := extcodehash(account) }
        return (codehash != 0x0 && codehash != accountHash);
    }

    
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        
        (bool success, ) = recipient.call.value(amount)("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        
        
        
        
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        
        

        
        
        
        
        
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { 
            
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

contract CanReclaimTokens is Claimable {
    using SafeERC20 for ERC20;

    mapping(address => bool) private recoverableTokensBlacklist;

    function initialize(address _nextOwner) public initializer {
        Claimable.initialize(_nextOwner);
    }

    function blacklistRecoverableToken(address _token) public onlyOwner {
        recoverableTokensBlacklist[_token] = true;
    }

    
    
    function recoverTokens(address _token) external onlyOwner {
        require(
            !recoverableTokensBlacklist[_token],
            "CanReclaimTokens: token is not recoverable"
        );

        if (_token == address(0x0)) {
            msg.sender.transfer(address(this).balance);
        } else {
            ERC20(_token).safeTransfer(
                msg.sender,
                ERC20(_token).balanceOf(address(this))
            );
        }
    }
}

contract DarknodeRegistryStore is Claimable, CanReclaimTokens {
    using SafeMath for uint256;

    string public VERSION; 

    
    
    
    
    
    struct Darknode {
        
        
        
        
        address payable owner;
        
        
        
        uint256 bond;
        
        uint256 registeredAt;
        
        uint256 deregisteredAt;
        
        
        
        
        bytes publicKey;
    }

    
    mapping(address => Darknode) private darknodeRegistry;
    LinkedList.List private darknodes;

    
    RenToken public ren;

    
    
    
    
    constructor(string memory _VERSION, RenToken _ren) public {
        Claimable.initialize(msg.sender);
        CanReclaimTokens.initialize(msg.sender);
        VERSION = _VERSION;
        ren = _ren;
        blacklistRecoverableToken(address(ren));
    }

    
    
    
    
    
    
    
    
    
    function appendDarknode(
        address _darknodeID,
        address payable _darknodeOperator,
        uint256 _bond,
        bytes calldata _publicKey,
        uint256 _registeredAt,
        uint256 _deregisteredAt
    ) external onlyOwner {
        Darknode memory darknode = Darknode({
            owner: _darknodeOperator,
            bond: _bond,
            publicKey: _publicKey,
            registeredAt: _registeredAt,
            deregisteredAt: _deregisteredAt
        });
        darknodeRegistry[_darknodeID] = darknode;
        LinkedList.append(darknodes, _darknodeID);
    }

    
    function begin() external view onlyOwner returns (address) {
        return LinkedList.begin(darknodes);
    }

    
    
    function next(address darknodeID)
        external
        view
        onlyOwner
        returns (address)
    {
        return LinkedList.next(darknodes, darknodeID);
    }

    
    
    function removeDarknode(address darknodeID) external onlyOwner {
        uint256 bond = darknodeRegistry[darknodeID].bond;
        delete darknodeRegistry[darknodeID];
        LinkedList.remove(darknodes, darknodeID);
        require(
            ren.transfer(owner(), bond),
            "DarknodeRegistryStore: bond transfer failed"
        );
    }

    
    
    function updateDarknodeBond(address darknodeID, uint256 decreasedBond)
        external
        onlyOwner
    {
        uint256 previousBond = darknodeRegistry[darknodeID].bond;
        require(
            decreasedBond < previousBond,
            "DarknodeRegistryStore: bond not decreased"
        );
        darknodeRegistry[darknodeID].bond = decreasedBond;
        require(
            ren.transfer(owner(), previousBond.sub(decreasedBond)),
            "DarknodeRegistryStore: bond transfer failed"
        );
    }

    
    function updateDarknodeDeregisteredAt(
        address darknodeID,
        uint256 deregisteredAt
    ) external onlyOwner {
        darknodeRegistry[darknodeID].deregisteredAt = deregisteredAt;
    }

    
    function darknodeOperator(address darknodeID)
        external
        view
        onlyOwner
        returns (address payable)
    {
        return darknodeRegistry[darknodeID].owner;
    }

    
    function darknodeBond(address darknodeID)
        external
        view
        onlyOwner
        returns (uint256)
    {
        return darknodeRegistry[darknodeID].bond;
    }

    
    function darknodeRegisteredAt(address darknodeID)
        external
        view
        onlyOwner
        returns (uint256)
    {
        return darknodeRegistry[darknodeID].registeredAt;
    }

    
    function darknodeDeregisteredAt(address darknodeID)
        external
        view
        onlyOwner
        returns (uint256)
    {
        return darknodeRegistry[darknodeID].deregisteredAt;
    }

    
    function darknodePublicKey(address darknodeID)
        external
        view
        onlyOwner
        returns (bytes memory)
    {
        return darknodeRegistry[darknodeID].publicKey;
    }
}

interface IDarknodePaymentStore {}

interface IDarknodePayment {
    function changeCycle() external returns (uint256);
    function store() external view returns (IDarknodePaymentStore);
}

interface IDarknodeSlasher {}

contract DarknodeRegistryStateV1 {
    using SafeMath for uint256;

    string public VERSION; 

    
    
    
    struct Epoch {
        uint256 epochhash;
        uint256 blocktime;
    }

    uint256 public numDarknodes;
    uint256 public numDarknodesNextEpoch;
    uint256 public numDarknodesPreviousEpoch;

    
    uint256 public minimumBond;
    uint256 public minimumPodSize;
    uint256 public minimumEpochInterval;
    uint256 public deregistrationInterval;

    
    
    
    uint256 public nextMinimumBond;
    uint256 public nextMinimumPodSize;
    uint256 public nextMinimumEpochInterval;

    
    Epoch public currentEpoch;
    Epoch public previousEpoch;

    
    RenToken public ren;

    
    DarknodeRegistryStore public store;

    
    IDarknodePayment public darknodePayment;

    
    IDarknodeSlasher public slasher;
    IDarknodeSlasher public nextSlasher;
}

contract DarknodeRegistryLogicV1 is
    Claimable,
    CanReclaimTokens,
    DarknodeRegistryStateV1
{
    
    
    
    
    event LogDarknodeRegistered(
        address indexed _darknodeOperator,
        address indexed _darknodeID,
        uint256 _bond
    );

    
    
    
    event LogDarknodeDeregistered(
        address indexed _darknodeOperator,
        address indexed _darknodeID
    );

    
    
    
    event LogDarknodeRefunded(
        address indexed _darknodeOperator,
        address indexed _darknodeID,
        uint256 _amount
    );

    
    
    
    
    
    event LogDarknodeSlashed(
        address indexed _darknodeOperator,
        address indexed _darknodeID,
        address indexed _challenger,
        uint256 _percentage
    );

    
    event LogNewEpoch(uint256 indexed epochhash);

    
    event LogMinimumBondUpdated(
        uint256 _previousMinimumBond,
        uint256 _nextMinimumBond
    );
    event LogMinimumPodSizeUpdated(
        uint256 _previousMinimumPodSize,
        uint256 _nextMinimumPodSize
    );
    event LogMinimumEpochIntervalUpdated(
        uint256 _previousMinimumEpochInterval,
        uint256 _nextMinimumEpochInterval
    );
    event LogSlasherUpdated(
        address indexed _previousSlasher,
        address indexed _nextSlasher
    );
    event LogDarknodePaymentUpdated(
        IDarknodePayment indexed _previousDarknodePayment,
        IDarknodePayment indexed _nextDarknodePayment
    );

    
    modifier onlyDarknodeOperator(address _darknodeID) {
        require(
            store.darknodeOperator(_darknodeID) == msg.sender,
            "DarknodeRegistry: must be darknode owner"
        );
        _;
    }

    
    modifier onlyRefunded(address _darknodeID) {
        require(
            isRefunded(_darknodeID),
            "DarknodeRegistry: must be refunded or never registered"
        );
        _;
    }

    
    modifier onlyRefundable(address _darknodeID) {
        require(
            isRefundable(_darknodeID),
            "DarknodeRegistry: must be deregistered for at least one epoch"
        );
        _;
    }

    
    
    modifier onlyDeregisterable(address _darknodeID) {
        require(
            isDeregisterable(_darknodeID),
            "DarknodeRegistry: must be deregisterable"
        );
        _;
    }

    
    modifier onlySlasher() {
        require(
            address(slasher) == msg.sender,
            "DarknodeRegistry: must be slasher"
        );
        _;
    }

    
    
    modifier onlyDarknode(address _darknodeID) {
        require(
            isRegistered(_darknodeID),
            "DarknodeRegistry: invalid darknode"
        );
        _;
    }

    
    
    
    
    
    
    
    
    
    function initialize(
        string memory _VERSION,
        RenToken _renAddress,
        DarknodeRegistryStore _storeAddress,
        uint256 _minimumBond,
        uint256 _minimumPodSize,
        uint256 _minimumEpochIntervalSeconds,
        uint256 _deregistrationIntervalSeconds
    ) public initializer {
        Claimable.initialize(msg.sender);
        CanReclaimTokens.initialize(msg.sender);
        VERSION = _VERSION;

        store = _storeAddress;
        ren = _renAddress;

        minimumBond = _minimumBond;
        nextMinimumBond = minimumBond;

        minimumPodSize = _minimumPodSize;
        nextMinimumPodSize = minimumPodSize;

        minimumEpochInterval = _minimumEpochIntervalSeconds;
        nextMinimumEpochInterval = minimumEpochInterval;
        deregistrationInterval = _deregistrationIntervalSeconds;

        uint256 epochhash = uint256(blockhash(block.number - 1));
        currentEpoch = Epoch({
            epochhash: epochhash,
            blocktime: block.timestamp
        });
        emit LogNewEpoch(epochhash);
    }

    
    
    
    
    
    
    
    
    
    
    function register(address _darknodeID, bytes calldata _publicKey)
        external
        onlyRefunded(_darknodeID)
    {
        require(
            _darknodeID != address(0),
            "DarknodeRegistry: darknode address cannot be zero"
        );

        
        require(
            ren.transferFrom(msg.sender, address(store), minimumBond),
            "DarknodeRegistry: bond transfer failed"
        );

        
        store.appendDarknode(
            _darknodeID,
            msg.sender,
            minimumBond,
            _publicKey,
            currentEpoch.blocktime.add(minimumEpochInterval),
            0
        );

        numDarknodesNextEpoch = numDarknodesNextEpoch.add(1);

        
        emit LogDarknodeRegistered(msg.sender, _darknodeID, minimumBond);
    }

    
    
    
    
    
    
    function deregister(address _darknodeID)
        external
        onlyDeregisterable(_darknodeID)
        onlyDarknodeOperator(_darknodeID)
    {
        deregisterDarknode(_darknodeID);
    }

    
    
    
    function epoch() external {
        if (previousEpoch.blocktime == 0) {
            
            require(
                msg.sender == owner(),
                "DarknodeRegistry: not authorized to call first epoch"
            );
        }

        
        require(
            block.timestamp >= currentEpoch.blocktime.add(minimumEpochInterval),
            "DarknodeRegistry: epoch interval has not passed"
        );
        uint256 epochhash = uint256(blockhash(block.number - 1));

        
        previousEpoch = currentEpoch;
        currentEpoch = Epoch({
            epochhash: epochhash,
            blocktime: block.timestamp
        });

        
        numDarknodesPreviousEpoch = numDarknodes;
        numDarknodes = numDarknodesNextEpoch;

        
        if (nextMinimumBond != minimumBond) {
            minimumBond = nextMinimumBond;
            emit LogMinimumBondUpdated(minimumBond, nextMinimumBond);
        }
        if (nextMinimumPodSize != minimumPodSize) {
            minimumPodSize = nextMinimumPodSize;
            emit LogMinimumPodSizeUpdated(minimumPodSize, nextMinimumPodSize);
        }
        if (nextMinimumEpochInterval != minimumEpochInterval) {
            minimumEpochInterval = nextMinimumEpochInterval;
            emit LogMinimumEpochIntervalUpdated(
                minimumEpochInterval,
                nextMinimumEpochInterval
            );
        }
        if (nextSlasher != slasher) {
            slasher = nextSlasher;
            emit LogSlasherUpdated(address(slasher), address(nextSlasher));
        }
        if (address(darknodePayment) != address(0x0)) {
            darknodePayment.changeCycle();
        }

        
        emit LogNewEpoch(epochhash);
    }

    
    
    
    function transferStoreOwnership(DarknodeRegistryLogicV1 _newOwner)
        external
        onlyOwner
    {
        store.transferOwnership(address(_newOwner));
        _newOwner.claimStoreOwnership();
    }

    
    
    
    function claimStoreOwnership() external {
        store.claimOwnership();

        
        
        (
            numDarknodesPreviousEpoch,
            numDarknodes,
            numDarknodesNextEpoch
        ) = getDarknodeCountFromEpochs();
    }

    
    
    
    
    function updateDarknodePayment(IDarknodePayment _darknodePayment)
        external
        onlyOwner
    {
        require(
            address(_darknodePayment) != address(0x0),
            "DarknodeRegistry: invalid Darknode Payment address"
        );
        IDarknodePayment previousDarknodePayment = darknodePayment;
        darknodePayment = _darknodePayment;
        emit LogDarknodePaymentUpdated(
            previousDarknodePayment,
            darknodePayment
        );
    }

    
    
    
    function updateMinimumBond(uint256 _nextMinimumBond) external onlyOwner {
        
        nextMinimumBond = _nextMinimumBond;
    }

    
    
    function updateMinimumPodSize(uint256 _nextMinimumPodSize)
        external
        onlyOwner
    {
        
        nextMinimumPodSize = _nextMinimumPodSize;
    }

    
    
    function updateMinimumEpochInterval(uint256 _nextMinimumEpochInterval)
        external
        onlyOwner
    {
        
        nextMinimumEpochInterval = _nextMinimumEpochInterval;
    }

    
    
    
    function updateSlasher(IDarknodeSlasher _slasher) external onlyOwner {
        require(
            address(_slasher) != address(0),
            "DarknodeRegistry: invalid slasher address"
        );
        nextSlasher = _slasher;
    }

    
    
    
    
    
    function slash(address _guilty, address _challenger, uint256 _percentage)
        external
        onlySlasher
        onlyDarknode(_guilty)
    {
        require(_percentage <= 100, "DarknodeRegistry: invalid percent");

        
        if (isDeregisterable(_guilty)) {
            deregisterDarknode(_guilty);
        }

        uint256 totalBond = store.darknodeBond(_guilty);
        uint256 penalty = totalBond.div(100).mul(_percentage);
        uint256 challengerReward = penalty.div(2);
        uint256 darknodePaymentReward = penalty.sub(challengerReward);
        if (challengerReward > 0) {
            
            store.updateDarknodeBond(_guilty, totalBond.sub(penalty));

            
            require(
                address(darknodePayment) != address(0x0),
                "DarknodeRegistry: invalid payment address"
            );
            require(
                ren.transfer(
                    address(darknodePayment.store()),
                    darknodePaymentReward
                ),
                "DarknodeRegistry: reward transfer failed"
            );
            require(
                ren.transfer(_challenger, challengerReward),
                "DarknodeRegistry: reward transfer failed"
            );
        }

        emit LogDarknodeSlashed(
            store.darknodeOperator(_guilty),
            _guilty,
            _challenger,
            _percentage
        );
    }

    
    
    
    
    
    function refund(address _darknodeID) external onlyRefundable(_darknodeID) {
        address darknodeOperator = store.darknodeOperator(_darknodeID);

        
        uint256 amount = store.darknodeBond(_darknodeID);

        
        store.removeDarknode(_darknodeID);

        
        require(
            ren.transfer(darknodeOperator, amount),
            "DarknodeRegistry: bond transfer failed"
        );

        
        emit LogDarknodeRefunded(darknodeOperator, _darknodeID, amount);
    }

    
    
    function getDarknodeOperator(address _darknodeID)
        external
        view
        returns (address payable)
    {
        return store.darknodeOperator(_darknodeID);
    }

    
    
    function getDarknodeBond(address _darknodeID)
        external
        view
        returns (uint256)
    {
        return store.darknodeBond(_darknodeID);
    }

    
    
    function getDarknodePublicKey(address _darknodeID)
        external
        view
        returns (bytes memory)
    {
        return store.darknodePublicKey(_darknodeID);
    }

    
    
    
    
    
    
    
    
    
    
    function getDarknodes(address _start, uint256 _count)
        external
        view
        returns (address[] memory)
    {
        uint256 count = _count;
        if (count == 0) {
            count = numDarknodes;
        }
        return getDarknodesFromEpochs(_start, count, false);
    }

    
    
    function getPreviousDarknodes(address _start, uint256 _count)
        external
        view
        returns (address[] memory)
    {
        uint256 count = _count;
        if (count == 0) {
            count = numDarknodesPreviousEpoch;
        }
        return getDarknodesFromEpochs(_start, count, true);
    }

    
    
    
    function isPendingRegistration(address _darknodeID)
        public
        view
        returns (bool)
    {
        uint256 registeredAt = store.darknodeRegisteredAt(_darknodeID);
        return registeredAt != 0 && registeredAt > currentEpoch.blocktime;
    }

    
    
    function isPendingDeregistration(address _darknodeID)
        public
        view
        returns (bool)
    {
        uint256 deregisteredAt = store.darknodeDeregisteredAt(_darknodeID);
        return deregisteredAt != 0 && deregisteredAt > currentEpoch.blocktime;
    }

    
    function isDeregistered(address _darknodeID) public view returns (bool) {
        uint256 deregisteredAt = store.darknodeDeregisteredAt(_darknodeID);
        return deregisteredAt != 0 && deregisteredAt <= currentEpoch.blocktime;
    }

    
    
    
    function isDeregisterable(address _darknodeID) public view returns (bool) {
        uint256 deregisteredAt = store.darknodeDeregisteredAt(_darknodeID);
        
        
        return isRegistered(_darknodeID) && deregisteredAt == 0;
    }

    
    
    
    function isRefunded(address _darknodeID) public view returns (bool) {
        uint256 registeredAt = store.darknodeRegisteredAt(_darknodeID);
        uint256 deregisteredAt = store.darknodeDeregisteredAt(_darknodeID);
        return registeredAt == 0 && deregisteredAt == 0;
    }

    
    
    function isRefundable(address _darknodeID) public view returns (bool) {
        return
            isDeregistered(_darknodeID) &&
            store.darknodeDeregisteredAt(_darknodeID) <=
            (previousEpoch.blocktime - deregistrationInterval);
    }

    
    function isRegistered(address _darknodeID) public view returns (bool) {
        return isRegisteredInEpoch(_darknodeID, currentEpoch);
    }

    
    function isRegisteredInPreviousEpoch(address _darknodeID)
        public
        view
        returns (bool)
    {
        return isRegisteredInEpoch(_darknodeID, previousEpoch);
    }

    
    
    
    
    function isRegisteredInEpoch(address _darknodeID, Epoch memory _epoch)
        private
        view
        returns (bool)
    {
        uint256 registeredAt = store.darknodeRegisteredAt(_darknodeID);
        uint256 deregisteredAt = store.darknodeDeregisteredAt(_darknodeID);
        bool registered = registeredAt != 0 && registeredAt <= _epoch.blocktime;
        bool notDeregistered = deregisteredAt == 0 ||
            deregisteredAt > _epoch.blocktime;
        
        
        return registered && notDeregistered;
    }

    
    
    
    
    
    function getDarknodesFromEpochs(
        address _start,
        uint256 _count,
        bool _usePreviousEpoch
    ) private view returns (address[] memory) {
        uint256 count = _count;
        if (count == 0) {
            count = numDarknodes;
        }

        address[] memory nodes = new address[](count);

        
        uint256 n = 0;
        address next = _start;
        if (next == address(0)) {
            next = store.begin();
        }

        
        while (n < count) {
            if (next == address(0)) {
                break;
            }
            
            bool includeNext;
            if (_usePreviousEpoch) {
                includeNext = isRegisteredInPreviousEpoch(next);
            } else {
                includeNext = isRegistered(next);
            }
            if (!includeNext) {
                next = store.next(next);
                continue;
            }
            nodes[n] = next;
            next = store.next(next);
            n += 1;
        }
        return nodes;
    }

    
    function deregisterDarknode(address _darknodeID) private {
        address darknodeOperator = store.darknodeOperator(_darknodeID);

        
        store.updateDarknodeDeregisteredAt(
            _darknodeID,
            currentEpoch.blocktime.add(minimumEpochInterval)
        );
        numDarknodesNextEpoch = numDarknodesNextEpoch.sub(1);

        
        emit LogDarknodeDeregistered(darknodeOperator, _darknodeID);
    }

    function getDarknodeCountFromEpochs()
        private
        view
        returns (uint256, uint256, uint256)
    {
        
        uint256 nPreviousEpoch = 0;
        uint256 nCurrentEpoch = 0;
        uint256 nNextEpoch = 0;
        address next = store.begin();

        
        while (true) {
            
            if (next == address(0)) {
                break;
            }

            if (isRegisteredInPreviousEpoch(next)) {
                nPreviousEpoch += 1;
            }

            if (isRegistered(next)) {
                nCurrentEpoch += 1;
            }

            
            
            if (
                ((isRegistered(next) && !isPendingDeregistration(next)) ||
                    isPendingRegistration(next))
            ) {
                nNextEpoch += 1;
            }
            next = store.next(next);
        }
        return (nPreviousEpoch, nCurrentEpoch, nNextEpoch);
    }
}

contract DarknodeRegistryProxy is InitializableAdminUpgradeabilityProxy {}