// File: contracts/base/PotPool.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.5.16;

import "./inheritance/Controllable.sol";
import "./interface/IController.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/GSN/Context.sol";
import "@openzeppelin/contracts/ownership/Ownable.sol";

contract IRewardDistributionRecipient is Ownable {

    mapping (address => bool) public rewardDistribution;

    constructor(address[] memory _rewardDistributions) public {
        // NotifyHelper
        rewardDistribution[0xE20c31e3d08027F5AfACe84A3A46B7b3B165053c] = true;

        // FeeRewardForwarderV6
        rewardDistribution[0x153C544f72329c1ba521DDf5086cf2fA98C86676] = true;

        // Community Multisig
        rewardDistribution[0xF49440C1F012d041802b25A73e5B0B9166a75c02] = true;

        for(uint256 i = 0; i < _rewardDistributions.length; i++) {
          rewardDistribution[_rewardDistributions[i]] = true;
        }
    }

    function notifyTargetRewardAmount(address rewardToken, uint256 reward) external;
    function notifyRewardAmount(uint256 reward) external;

    modifier onlyRewardDistribution() {
        require(rewardDistribution[_msgSender()], "Caller is not reward distribution");
        _;
    }

    function setRewardDistribution(address[] calldata _newRewardDistribution, bool _flag)
        external
        onlyOwner
    {
        for(uint256 i = 0; i < _newRewardDistribution.length; i++){
          rewardDistribution[_newRewardDistribution[i]] = _flag;
        }
    }
}

contract PotPool is IRewardDistributionRecipient, Controllable, ERC20, ERC20Detailed {

    using Address for address;
    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    address public lpToken;
    uint256 public duration; // making it not a constant is less gas efficient, but portable

    mapping(address => uint256) public stakedBalanceOf;

    mapping (address => bool) smartContractStakers;
    address[] public rewardTokens;
    mapping(address => uint256) public periodFinishForToken;
    mapping(address => uint256) public rewardRateForToken;
    mapping(address => uint256) public lastUpdateTimeForToken;
    mapping(address => uint256) public rewardPerTokenStoredForToken;
    mapping(address => mapping(address => uint256)) public userRewardPerTokenPaidForToken;
    mapping(address => mapping(address => uint256)) public rewardsForToken;

    event RewardAdded(address rewardToken, uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, address rewardToken, uint256 reward);
    event RewardDenied(address indexed user, address rewardToken, uint256 reward);
    event SmartContractRecorded(address indexed smartContractAddress, address indexed smartContractInitiator);

    modifier onlyGovernanceOrRewardDistribution() {
      require(msg.sender == governance() || rewardDistribution[msg.sender], "Not governance nor reward distribution");
      _;
    }

    modifier updateRewards(address account) {
      for(uint256 i = 0; i < rewardTokens.length; i++ ){
        address rt = rewardTokens[i];
        rewardPerTokenStoredForToken[rt] = rewardPerToken(rt);
        lastUpdateTimeForToken[rt] = lastTimeRewardApplicable(rt);
        if (account != address(0)) {
            rewardsForToken[rt][account] = earned(rt, account);
            userRewardPerTokenPaidForToken[rt][account] = rewardPerTokenStoredForToken[rt];
        }
      }
      _;
    }

    modifier updateReward(address account, address rt){
      rewardPerTokenStoredForToken[rt] = rewardPerToken(rt);
      lastUpdateTimeForToken[rt] = lastTimeRewardApplicable(rt);
      if (account != address(0)) {
          rewardsForToken[rt][account] = earned(rt, account);
          userRewardPerTokenPaidForToken[rt][account] = rewardPerTokenStoredForToken[rt];
      }
      _;
    }

    /** View functions to respect old interface */
    function rewardToken() public view returns(address) {
      return rewardTokens[0];
    }

    function rewardPerToken() public view returns(uint256) {
      return rewardPerToken(rewardTokens[0]);
    }

    function periodFinish() public view returns(uint256) {
      return periodFinishForToken[rewardTokens[0]];
    }

    function rewardRate() public view returns(uint256) {
      return rewardRateForToken[rewardTokens[0]];
    }

    function lastUpdateTime() public view returns(uint256) {
      return lastUpdateTimeForToken[rewardTokens[0]];
    }

    function rewardPerTokenStored() public view returns(uint256) {
      return rewardPerTokenStoredForToken[rewardTokens[0]];
    }

    function userRewardPerTokenPaid(address user) public view returns(uint256) {
      return userRewardPerTokenPaidForToken[rewardTokens[0]][user];
    }

    function rewards(address user) public view returns(uint256) {
      return rewardsForToken[rewardTokens[0]][user];
    }

    // [Hardwork] setting the reward, lpToken, duration, and rewardDistribution for each pool
    constructor(
        address[] memory _rewardTokens,
        address _lpToken,
        uint256 _duration,
        address[] memory _rewardDistribution,
        address _storage,
        string memory _name,
        string memory _symbol,
        uint8 _decimals
      ) public
      ERC20Detailed(_name, _symbol, _decimals)
      IRewardDistributionRecipient(_rewardDistribution)
      Controllable(_storage) // only used for referencing the grey list
    {
        require(_decimals == ERC20Detailed(_lpToken).decimals(), "decimals has to be aligned with the lpToken");
        require(_rewardTokens.length != 0, "should initialize with at least 1 rewardToken");
        rewardTokens = _rewardTokens;
        lpToken = _lpToken;
        duration = _duration;
    }

    function lastTimeRewardApplicable(uint256 i) public view returns (uint256) {
        return lastTimeRewardApplicable(rewardTokens[i]);
    }

    function lastTimeRewardApplicable(address rt) public view returns (uint256) {
        return Math.min(block.timestamp, periodFinishForToken[rt]);
    }

    function lastTimeRewardApplicable() public view returns (uint256) {
        return lastTimeRewardApplicable(rewardTokens[0]);
    }

    function rewardPerToken(uint256 i) public view returns (uint256) {
        return rewardPerToken(rewardTokens[i]);
    }

    function rewardPerToken(address rt) public view returns (uint256) {
        if (totalSupply() == 0) {
            return rewardPerTokenStoredForToken[rt];
        }
        return
            rewardPerTokenStoredForToken[rt].add(
                lastTimeRewardApplicable(rt)
                    .sub(lastUpdateTimeForToken[rt])
                    .mul(rewardRateForToken[rt])
                    .mul(1e18)
                    .div(totalSupply())
            );
    }

    function earned(uint256 i, address account) public view returns (uint256) {
        return earned(rewardTokens[i], account);
    }

    function earned(address account) public view returns (uint256) {
        return earned(rewardTokens[0], account);
    }

    function earned(address rt, address account) public view returns (uint256) {
        return
            stakedBalanceOf[account]
                .mul(rewardPerToken(rt).sub(userRewardPerTokenPaidForToken[rt][account]))
                .div(1e18)
                .add(rewardsForToken[rt][account]);
    }

    function stake(uint256 amount) public updateRewards(msg.sender) {
        require(amount > 0, "Cannot stake 0");
        recordSmartContract();
        super._mint(msg.sender, amount); // ERC20 is used as a staking receipt
        stakedBalanceOf[msg.sender] = stakedBalanceOf[msg.sender].add(amount);
        IERC20(lpToken).safeTransferFrom(msg.sender, address(this), amount);
        emit Staked(msg.sender, amount);
    }

    function withdraw(uint256 amount) public updateRewards(msg.sender) {
        require(amount > 0, "Cannot withdraw 0");
        super._burn(msg.sender, amount);
        stakedBalanceOf[msg.sender] = stakedBalanceOf[msg.sender].sub(amount);
        IERC20(lpToken).safeTransfer(msg.sender, amount);
        emit Withdrawn(msg.sender, amount);
    }

    function exit() external {
        withdraw(Math.min(stakedBalanceOf[msg.sender], balanceOf(msg.sender)));
        getAllRewards();
    }

    /// A push mechanism for accounts that have not claimed their rewards for a long time.
    /// The implementation is semantically analogous to getReward(), but uses a push pattern
    /// instead of pull pattern.
    function pushAllRewards(address recipient) public updateRewards(recipient) onlyGovernance {
      bool rewardPayout = (!smartContractStakers[recipient] || !IController(controller()).greyList(recipient));
      for(uint256 i = 0 ; i < rewardTokens.length; i++ ){
        uint256 reward = earned(rewardTokens[i], recipient);
        if (reward > 0) {
            rewardsForToken[rewardTokens[i]][recipient] = 0;
            // If it is a normal user and not smart contract,
            // then the requirement will pass
            // If it is a smart contract, then
            // make sure that it is not on our greyList.
            if (rewardPayout) {
                IERC20(rewardTokens[i]).safeTransfer(recipient, reward);
                emit RewardPaid(recipient, rewardTokens[i], reward);
            } else {
                emit RewardDenied(recipient, rewardTokens[i], reward);
            }
        }
      }
    }

    function getAllRewards() public updateRewards(msg.sender) {
      recordSmartContract();
      bool rewardPayout = (!smartContractStakers[msg.sender] || !IController(controller()).greyList(msg.sender));
      for(uint256 i = 0 ; i < rewardTokens.length; i++ ){
        _getRewardAction(rewardTokens[i], rewardPayout);
      }
    }

    function getReward(address rt) public updateReward(msg.sender, rt) {
      recordSmartContract();
      _getRewardAction(
        rt,
        // don't payout if it is a grey listed smart contract
        (!smartContractStakers[msg.sender] || !IController(controller()).greyList(msg.sender))
      );
    }

    function getReward() public {
      getReward(rewardTokens[0]);
    }

    function _getRewardAction(address rt, bool rewardPayout) internal {
      uint256 reward = earned(rt, msg.sender);
      if (reward > 0 && IERC20(rt).balanceOf(address(this)) >= reward ) {
          rewardsForToken[rt][msg.sender] = 0;
          // If it is a normal user and not smart contract,
          // then the requirement will pass
          // If it is a smart contract, then
          // make sure that it is not on our greyList.
          if (rewardPayout) {
              IERC20(rt).safeTransfer(msg.sender, reward);
              emit RewardPaid(msg.sender, rt, reward);
          } else {
              emit RewardDenied(msg.sender, rt, reward);
          }
      }
    }

    function addRewardToken(address rt) public onlyGovernanceOrRewardDistribution {
      require(getRewardTokenIndex(rt) == uint256(-1), "Reward token already exists");
      rewardTokens.push(rt);
    }

    function removeRewardToken(address rt) public onlyGovernance {
      uint256 i = getRewardTokenIndex(rt);
      require(i != uint256(-1), "Reward token does not exists");
      require(periodFinishForToken[rewardTokens[i]] < block.timestamp, "Can only remove when the reward period has passed");
      require(rewardTokens.length > 1, "Cannot remove the last reward token");
      uint256 lastIndex = rewardTokens.length - 1;

      // swap
      rewardTokens[i] = rewardTokens[lastIndex];

      // delete last element
      rewardTokens.length--;
    }

    // If the return value is MAX_UINT256, it means that
    // the specified reward token is not in the list
    function getRewardTokenIndex(address rt) public view returns(uint256) {
      for(uint i = 0 ; i < rewardTokens.length ; i++){
        if(rewardTokens[i] == rt)
          return i;
      }
      return uint256(-1);
    }

    function notifyTargetRewardAmount(address _rewardToken, uint256 reward)
        public
        onlyRewardDistribution
        updateRewards(address(0))
    {
        // overflow fix according to https://sips.synthetix.io/sips/sip-77
        require(reward < uint(-1) / 1e18, "the notified reward cannot invoke multiplication overflow");

        uint256 i = getRewardTokenIndex(_rewardToken);
        require(i != uint256(-1), "rewardTokenIndex not found");

        if (block.timestamp >= periodFinishForToken[_rewardToken]) {
            rewardRateForToken[_rewardToken] = reward.div(duration);
        } else {
            uint256 remaining = periodFinishForToken[_rewardToken].sub(block.timestamp);
            uint256 leftover = remaining.mul(rewardRateForToken[_rewardToken]);
            rewardRateForToken[_rewardToken] = reward.add(leftover).div(duration);
        }
        lastUpdateTimeForToken[_rewardToken] = block.timestamp;
        periodFinishForToken[_rewardToken] = block.timestamp.add(duration);
        emit RewardAdded(_rewardToken, reward);
    }

    function notifyRewardAmount(uint256 reward)
        external
        onlyRewardDistribution
        updateRewards(address(0))
    {
      notifyTargetRewardAmount(rewardTokens[0], reward);
    }

    function rewardTokensLength() public view returns(uint256){
      return rewardTokens.length;
    }

    // Harvest Smart Contract recording
    function recordSmartContract() internal {
      if( tx.origin != msg.sender ) {
        smartContractStakers[msg.sender] = true;
        emit SmartContractRecorded(msg.sender, tx.origin);
      }
    }

}

// File: contracts/base/inheritance/Controllable.sol



pragma solidity 0.5.16;

import "./Governable.sol";

contract Controllable is Governable {

  constructor(address _storage) Governable(_storage) public {
  }

  modifier onlyController() {
    require(store.isController(msg.sender), "Not a controller");
    _;
  }

  modifier onlyControllerOrGovernance(){
    require((store.isController(msg.sender) || store.isGovernance(msg.sender)),
      "The caller must be controller or governance");
    _;
  }

  function controller() public view returns (address) {
    return store.controller();
  }
}

// File: contracts/base/interface/IController.sol



pragma solidity 0.5.16;

interface IController {

    event SharePriceChangeLog(
      address indexed vault,
      address indexed strategy,
      uint256 oldSharePrice,
      uint256 newSharePrice,
      uint256 timestamp
    );

    // [Grey list]
    // An EOA can safely interact with the system no matter what.
    // If you're using Metamask, you're using an EOA.
    // Only smart contracts may be affected by this grey list.
    //
    // This contract will not be able to ban any EOA from the system
    // even if an EOA is being added to the greyList, he/she will still be able
    // to interact with the whole system as if nothing happened.
    // Only smart contracts will be affected by being added to the greyList.
    // This grey list is only used in Vault.sol, see the code there for reference
    function greyList(address _target) external view returns(bool);

    function addVaultAndStrategy(address _vault, address _strategy) external;
    function doHardWork(address _vault) external;

    function salvage(address _token, uint256 amount) external;
    function salvageStrategy(address _strategy, address _token, uint256 amount) external;

    function notifyFee(address _underlying, uint256 fee) external;
    function profitSharingNumerator() external view returns (uint256);
    function profitSharingDenominator() external view returns (uint256);

    function feeRewardForwarder() external view returns(address);
    function setFeeRewardForwarder(address _value) external;

    function addHardWorker(address _worker) external;
    function addToWhitelist(address _target) external;
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



pragma solidity ^0.5.0;

import "../../GSN/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 {ERC20Mintable}.
 *
 * 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;

    /**
     * @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"));
    }
}

// File: @openzeppelin/contracts/token/ERC20/ERC20Detailed.sol



pragma solidity ^0.5.0;

import "./IERC20.sol";

/**
 * @dev Optional functions from the ERC20 standard.
 */
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;
    }
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



pragma solidity ^0.5.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
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 {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).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));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



pragma solidity ^0.5.0;

/**
 * @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, 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;
    }
}

// File: @openzeppelin/contracts/math/Math.sol



pragma solidity ^0.5.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

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



pragma solidity ^0.5.5;

/**
 * @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) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    /**
     * @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].
     *
     * _Available since v2.4.0._
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-call-value
        (bool success, ) = recipient.call.value(amount)("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

// File: @openzeppelin/contracts/GSN/Context.sol



pragma solidity ^0.5.0;

/*
 * @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.
 */
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;
    }
}

// File: @openzeppelin/contracts/ownership/Ownable.sol



pragma solidity ^0.5.0;

import "../GSN/Context.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
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;
    }
}

// File: contracts/base/inheritance/Governable.sol



pragma solidity 0.5.16;

import "./Storage.sol";

contract Governable {

  Storage public store;

  constructor(address _store) public {
    require(_store != address(0), "new storage shouldn't be empty");
    store = Storage(_store);
  }

  modifier onlyGovernance() {
    require(store.isGovernance(msg.sender), "Not governance");
    _;
  }

  function setStorage(address _store) public onlyGovernance {
    require(_store != address(0), "new storage shouldn't be empty");
    store = Storage(_store);
  }

  function governance() public view returns (address) {
    return store.governance();
  }
}

// File: contracts/base/inheritance/Storage.sol



pragma solidity 0.5.16;

contract Storage {

  address public governance;
  address public controller;

  constructor() public {
    governance = msg.sender;
  }

  modifier onlyGovernance() {
    require(isGovernance(msg.sender), "Not governance");
    _;
  }

  function setGovernance(address _governance) public onlyGovernance {
    require(_governance != address(0), "new governance shouldn't be empty");
    governance = _governance;
  }

  function setController(address _controller) public onlyGovernance {
    require(_controller != address(0), "new controller shouldn't be empty");
    controller = _controller;
  }

  function isGovernance(address account) public view returns (bool) {
    return account == governance;
  }

  function isController(address account) public view returns (bool) {
    return account == controller;
  }
}