// File: contracts/protocol/staking/PhiatMultisigTreasury.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.7.6;
pragma experimental ABIEncoderV2;

import "../../dependencies/governance/Multisig.sol";
import "../../interfaces/IPhiatMultisigTreasury.sol";
import "./PhiatFeeDistribution.sol";
import "./PhiatToken.sol";

contract PhiatMultisigTreasury is Multisig, IPhiatMultisigTreasury {
    address public phiatFeeDistribution;

    constructor(
        address[] memory _owners,
        uint256 _required,
        address _phiatFeeDistribution
    ) Multisig(_owners, _required) {
        require(
            _phiatFeeDistribution != address(0),
            "Phiat fee distribution can not be zero address"
        );
        phiatFeeDistribution = _phiatFeeDistribution;
    }

    function mintPhiat() external override ownerExists(msg.sender) {
        PhiatToken phiat = PhiatToken(
            address(PhiatFeeDistribution(phiatFeeDistribution).stakingToken())
        );
        phiat.mint();
    }

    function mintPhiatByTreasury(address account)
        external
        override
        ownerExists(msg.sender)
    {
        PhiatToken phiat = PhiatToken(
            address(PhiatFeeDistribution(phiatFeeDistribution).stakingToken())
        );
        phiat.mintByTreasury(account);
    }

    function getReward() external override ownerExists(msg.sender) {
        PhiatFeeDistribution(phiatFeeDistribution).getReward();
    }

    function setPhiatFeeDistribution(address _phiatFeeDistribution)
        external
        onlyWallet
    {
        require(
            _phiatFeeDistribution != address(0),
            "Phiat fee distribution can not be zero address"
        );
        phiatFeeDistribution = _phiatFeeDistribution;
    }
}

// File: contracts/dependencies/governance/Multisig.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;
pragma experimental ABIEncoderV2;

contract Multisig {
    // ============ Events ============

    event Confirmation(address indexed sender, uint256 indexed transactionId);
    event Revocation(address indexed sender, uint256 indexed transactionId);
    event Submission(uint256 indexed transactionId);
    event Execution(uint256 indexed transactionId);
    event ExecutionFailure(uint256 indexed transactionId);
    event OwnerAddition(address indexed owner);
    event OwnerRemoval(address indexed owner);
    event RequirementChange(uint256 required);

    // ============ Constants ============

    uint256 public constant MAX_OWNER_COUNT = 50;
    address constant ADDRESS_ZERO = address(0);

    // ============ Storage ============

    mapping(uint256 => Transaction) public transactions;
    mapping(uint256 => mapping(address => bool)) public confirmations;
    mapping(address => bool) public isOwner;
    address[] public owners;
    uint256 public required;
    uint256 public transactionCount;

    // ============ Structs ============

    struct Transaction {
        address destination;
        uint256 value;
        bytes data;
        bool executed;
    }

    // ============ Modifiers ============

    modifier onlyWallet() {
        require(
            msg.sender == address(this),
            "Multisig: sender is not this contract"
        );
        _;
    }

    modifier ownerDoesNotExist(address owner) {
        require(!isOwner[owner], "Multisig: should not be one of the owners");
        _;
    }

    modifier ownerExists(address owner) {
        require(isOwner[owner], "Multisig: should be one of the owners");
        _;
    }

    modifier transactionExists(uint256 transactionId) {
        require(
            transactions[transactionId].destination != ADDRESS_ZERO,
            "Multisig: transaction does not exist"
        );
        _;
    }

    modifier confirmed(uint256 transactionId, address owner) {
        require(
            confirmations[transactionId][owner],
            "Multisig: transaction is not confirmed"
        );
        _;
    }

    modifier notConfirmed(uint256 transactionId, address owner) {
        require(
            !confirmations[transactionId][owner],
            "Multisig: transaction is confirmed"
        );
        _;
    }

    modifier notExecuted(uint256 transactionId) {
        require(
            !transactions[transactionId].executed,
            "Multisig: transaction is executed"
        );
        _;
    }

    modifier notNull(address _address) {
        require(
            _address != ADDRESS_ZERO,
            "Multisig: should not be zero address"
        );
        _;
    }

    modifier validRequirement(uint256 ownerCount, uint256 _required) {
        require(
            ownerCount <= MAX_OWNER_COUNT &&
                _required <= ownerCount &&
                _required != 0 &&
                ownerCount != 0,
            "Multisig: invalid owner setting"
        );
        _;
    }

    // ============ Constructor ============

    /**
     * Contract constructor sets initial owners and required number of confirmations.
     *
     * @param  _owners    List of initial owners.
     * @param  _required  Number of required confirmations.
     */
    constructor(address[] memory _owners, uint256 _required)
        validRequirement(_owners.length, _required)
    {
        for (uint256 i = 0; i < _owners.length; i++) {
            require(
                _owners[i] != ADDRESS_ZERO,
                "Multisig: owner should not be zero address"
            );
            require(
                !isOwner[_owners[i]],
                "Multisig: should not have duplicate owners"
            );
            isOwner[_owners[i]] = true;
        }
        owners = _owners;
        required = _required;
    }

    // ============ Wallet-Only Functions ============

    /**
     * Allows to add a new owner. Transaction has to be sent by wallet.
     *
     * @param  owner  Address of new owner.
     */
    function addOwner(address owner)
        public
        onlyWallet
        ownerDoesNotExist(owner)
        notNull(owner)
        validRequirement(owners.length + 1, required)
    {
        isOwner[owner] = true;
        owners.push(owner);
        emit OwnerAddition(owner);
    }

    /**
     * Allows to remove an owner. Transaction has to be sent by wallet.
     *
     * @param  owner  Address of owner.
     */
    function removeOwner(address owner) public onlyWallet ownerExists(owner) {
        isOwner[owner] = false;
        for (uint256 i = 0; i < owners.length - 1; i++) {
            if (owners[i] == owner) {
                owners[i] = owners[owners.length - 1];
                break;
            }
        }
        owners.pop();
        if (required > owners.length) {
            changeRequirement(owners.length);
        }
        emit OwnerRemoval(owner);
    }

    /**
     * Allows to replace an owner with a new owner. Transaction has to be sent by wallet.
     *
     * @param  owner     Address of owner to be replaced.
     * @param  newOwner  Address of new owner.
     */
    function replaceOwner(address owner, address newOwner)
        public
        onlyWallet
        ownerExists(owner)
        ownerDoesNotExist(newOwner)
        notNull(newOwner)
    {
        for (uint256 i = 0; i < owners.length; i++) {
            if (owners[i] == owner) {
                owners[i] = newOwner;
                break;
            }
        }
        isOwner[owner] = false;
        isOwner[newOwner] = true;
        emit OwnerRemoval(owner);
        emit OwnerAddition(newOwner);
    }

    /**
     * Allows to change the number of required confirmations. Transaction has to be sent by wallet.
     *
     * @param  _required  Number of required confirmations.
     */
    function changeRequirement(uint256 _required)
        public
        onlyWallet
        validRequirement(owners.length, _required)
    {
        required = _required;
        emit RequirementChange(_required);
    }

    // ============ Owner Functions ============

    /**
     * Allows an owner to submit and confirm a transaction.
     *
     * @param  destination  Transaction target address.
     * @param  value        Transaction ether value.
     * @param  data         Transaction data payload.
     * @return              Transaction ID.
     */
    function submitTransaction(
        address destination,
        uint256 value,
        bytes memory data
    ) public returns (uint256) {
        uint256 transactionId = addTransaction(destination, value, data);
        confirmTransaction(transactionId);
        return transactionId;
    }

    /**
     * Allows an owner to confirm a transaction.
     *
     * @param  transactionId  Transaction ID.
     */
    function confirmTransaction(uint256 transactionId)
        public
        ownerExists(msg.sender)
        transactionExists(transactionId)
        notConfirmed(transactionId, msg.sender)
    {
        confirmations[transactionId][msg.sender] = true;
        emit Confirmation(msg.sender, transactionId);
        executeTransaction(transactionId);
    }

    /**
     * Allows an owner to revoke a confirmation for a transaction.
     *
     * @param  transactionId  Transaction ID.
     */
    function revokeConfirmation(uint256 transactionId)
        public
        ownerExists(msg.sender)
        confirmed(transactionId, msg.sender)
        notExecuted(transactionId)
    {
        confirmations[transactionId][msg.sender] = false;
        emit Revocation(msg.sender, transactionId);
    }

    /**
     * Allows an owner to execute a confirmed transaction.
     *
     * @param  transactionId  Transaction ID.
     */
    function executeTransaction(uint256 transactionId)
        public
        ownerExists(msg.sender)
        confirmed(transactionId, msg.sender)
        notExecuted(transactionId)
    {
        if (isConfirmed(transactionId)) {
            Transaction storage txn = transactions[transactionId];
            txn.executed = true;
            if (externalCall(txn.destination, txn.value, txn.data)) {
                emit Execution(transactionId);
            } else {
                emit ExecutionFailure(transactionId);
                txn.executed = false;
            }
        }
    }

    // ============ Getter Functions ============

    /**
     * Returns the confirmation status of a transaction.
     *
     * @param  transactionId  Transaction ID.
     * @return                Confirmation status.
     */
    function isConfirmed(uint256 transactionId) public view returns (bool) {
        uint256 count = 0;
        for (uint256 i = 0; i < owners.length; i++) {
            if (confirmations[transactionId][owners[i]]) {
                count += 1;
            }
            if (count == required) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns number of confirmations of a transaction.
     *
     * @param  transactionId  Transaction ID.
     * @return                Number of confirmations.
     */
    function getConfirmationCount(uint256 transactionId)
        public
        view
        returns (uint256)
    {
        uint256 count = 0;
        for (uint256 i = 0; i < owners.length; i++) {
            if (confirmations[transactionId][owners[i]]) {
                count += 1;
            }
        }
        return count;
    }

    /**
     * Returns total number of transactions after filers are applied.
     *
     * @param  pending   Include pending transactions.
     * @param  executed  Include executed transactions.
     * @return           Total number of transactions after filters are applied.
     */
    function getTransactionCount(bool pending, bool executed)
        public
        view
        returns (uint256)
    {
        uint256 count = 0;
        for (uint256 i = 0; i < transactionCount; i++) {
            if (
                (pending && !transactions[i].executed) ||
                (executed && transactions[i].executed)
            ) {
                count += 1;
            }
        }
        return count;
    }

    /**
     * Returns array of owners.
     *
     * @return  Array of owner addresses.
     */
    function getOwners() public view returns (address[] memory) {
        return owners;
    }

    /**
     * Returns array with owner addresses, which confirmed transaction.
     *
     * @param  transactionId  Transaction ID.
     * @return                Array of owner addresses.
     */
    function getConfirmations(uint256 transactionId)
        public
        view
        returns (address[] memory)
    {
        address[] memory confirmationsTemp = new address[](owners.length);
        uint256 count = 0;
        uint256 i;
        for (i = 0; i < owners.length; i++) {
            if (confirmations[transactionId][owners[i]]) {
                confirmationsTemp[count] = owners[i];
                count += 1;
            }
        }
        address[] memory _confirmations = new address[](count);
        for (i = 0; i < count; i++) {
            _confirmations[i] = confirmationsTemp[i];
        }
        return _confirmations;
    }

    /**
     * Returns list of transaction IDs in defined range.
     *
     * @param  from      Index start position of transaction array.
     * @param  to        Index end position of transaction array.
     * @param  pending   Include pending transactions.
     * @param  executed  Include executed transactions.
     * @return           Array of transaction IDs.
     */
    function getTransactionIds(
        uint256 from,
        uint256 to,
        bool pending,
        bool executed
    ) public view returns (uint256[] memory) {
        uint256[] memory transactionIdsTemp = new uint256[](transactionCount);
        uint256 count = 0;
        uint256 i;
        for (i = 0; i < transactionCount; i++) {
            if (
                (pending && !transactions[i].executed) ||
                (executed && transactions[i].executed)
            ) {
                transactionIdsTemp[count] = i;
                count += 1;
            }
        }
        uint256[] memory _transactionIds = new uint256[](to - from);
        for (i = from; i < to; i++) {
            _transactionIds[i - from] = transactionIdsTemp[i];
        }
        return _transactionIds;
    }

    // ============ Helper Functions ============

    // call has been separated into its own function in order to take advantage
    // of the Solidity's code generator to produce a loop that copies tx.data into memory.
    function externalCall(
        address destination,
        uint256 value,
        bytes memory data
    ) internal returns (bool) {
        (bool success, ) = destination.call{value: value}(data);
        return success;
    }

    /**
     * Adds a new transaction to the transaction mapping, if transaction does not exist yet.
     *
     * @param  destination  Transaction target address.
     * @param  value        Transaction ether value.
     * @param  data         Transaction data payload.
     * @return              Transaction ID.
     */
    function addTransaction(
        address destination,
        uint256 value,
        bytes memory data
    ) internal notNull(destination) returns (uint256) {
        uint256 transactionId = transactionCount;
        transactions[transactionId] = Transaction({
            destination: destination,
            value: value,
            data: data,
            executed: false
        });
        transactionCount += 1;
        emit Submission(transactionId);
        return transactionId;
    }
}

// File: contracts/interfaces/IPhiatMultisigTreasury.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.7.6;
pragma experimental ABIEncoderV2;

interface IPhiatMultisigTreasury {
    function mintPhiat() external;

    function mintPhiatByTreasury(address account) external;

    function getReward() external;
}

// File: contracts/protocol/staking/PhiatFeeDistribution.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.7.6;
pragma abicoder v2;

import "../../dependencies/openzeppelin/contracts/IERC20Capped.sol";
import "../../dependencies/openzeppelin/contracts/SafeERC20.sol";
import "../../dependencies/openzeppelin/contracts/SafeMath.sol";
import "../../dependencies/openzeppelin/contracts/Ownable.sol";
import "../../dependencies/governance/TreasuryOwnable.sol";
import "../../interfaces/IPhiatFeeDistribution.sol";
import "./ERC20Recoverable.sol";

contract PhiatFeeDistribution is
    IPhiatFeeDistribution,
    Ownable,
    TreasuryOwnable,
    ERC20Recoverable
{
    using SafeMath for uint256;
    using SafeERC20 for IERC20Capped;
    using SafeERC20 for IERC20;

    uint256 public constant override REWARD_RATE_PRECISION_ASSIST = 1e18;
    // Duration that rewards are streamed over
    uint256 public constant override REWARD_DURATION = 86400 * 7; // 1 week
    // Duration to unstake so that tokens are withdrawable
    uint256 public constant override UNSTAKE_DURATION = 86400 * 7 * 2; // 2 weeks
    // Duration to withdraw unstaked tokens
    uint256 public constant override WITHDRAW_DURATION = 86400 * 7; // 1 week

    IERC20Capped public immutable override stakingToken;
    uint256 public immutable override stakingTokenPrecision;
    uint256 public immutable override totalSupply; // staking token's total supply (cap)
    uint256 public override totalStakedSupply; // staking token's total staked supply
    address[] public tokens;
    // reward token -> TokenReward
    mapping(address => TokenReward) public tokenRewards;

    // user -> reward token -> amount
    // should divide by REWARD_RATE_PRECISION_ASSIST to get true reward (for total supply)
    // token's decimals are kept
    mapping(address => mapping(address => uint256)) private _userRewardPaid;
    // treasury reward is recorded in this contract's address - address(this)
    // should divide by REWARD_RATE_PRECISION_ASSIST to get true rewards (for individual user)
    // token's decimals are kept
    mapping(address => mapping(address => uint256)) private _userRewards;

    // user -> total staked balance (including unstaked and not withdrawn)
    mapping(address => uint256) private staked;
    // user -> TimedBalance(unstaked amount, withdraw time)
    mapping(address => TimedBalance) private unstaked;

    /* ========== CONSTRUCTOR ========== */

    constructor(address stakingToken_, address treasury_)
        Ownable()
        TreasuryOwnable(treasury_)
    {
        stakingToken = IERC20Capped(stakingToken_);
        stakingTokenPrecision = 10**IERC20Capped(stakingToken_).decimals();
        totalSupply = IERC20Capped(stakingToken_).cap();
    }

    /* ========== ADMIN CONFIGURATION ========== */

    // Add a new reward token to be distributed to stakers
    function addReward(address tokenAddress) external onlyOwner {
        require(
            tokenAddress != address(stakingToken),
            "PHIAT: Can not add staking token as reward token"
        );
        require(
            tokenRewards[tokenAddress].lastUpdateTime == 0,
            "PHIAT: Can not add existing reward token"
        );
        tokens.push(tokenAddress);
        tokenRewards[tokenAddress].lastUpdateTime = block.timestamp;
        tokenRewards[tokenAddress].periodFinish = block.timestamp;
    }

    function transferTreasury(address newTreasury)
        external
        override
        onlyTreasury
    {
        require(
            newTreasury != address(0),
            "TreasuryOwnable: new treasury is the zero address"
        );
        require(
            staked[newTreasury] == 0,
            "PHIAT: new treasury can not have staked tokens"
        );
        _transferTreasury(newTreasury);
    }

    /* ========== REWARD VIEWS ========== */

    function lastTimeRewardApplicable(address tokenAddress)
        public
        view
        override
        returns (uint256)
    {
        // should only return periodFinish
        // when this is a new reward token
        // or when no new rewards have been collected for over REWARD_DURATION
        uint256 periodFinish = tokenRewards[tokenAddress].periodFinish;
        return block.timestamp < periodFinish ? block.timestamp : periodFinish;
    }

    // should divide by REWARD_RATE_PRECISION_ASSIST to get true reward per token
    // token's decimals are kept
    // staking token's decimals are removed
    function rewardPerToken(address tokenAddress)
        external
        view
        override
        returns (uint256)
    {
        return _reward(tokenAddress).div(totalSupply);
    }

    function getRewardForDuration(address tokenAddress)
        external
        view
        override
        returns (uint256)
    {
        return
            tokenRewards[tokenAddress].rewardRate.mul(REWARD_DURATION).div(
                REWARD_RATE_PRECISION_ASSIST
            );
    }

    // Address and claimable amount of all reward tokens for the given account
    function claimableRewards(address account)
        external
        view
        override
        returns (RewardAmount[] memory rewards)
    {
        uint256 stakedBalance_;
        if (account == treasury()) {
            account = address(this);
            stakedBalance_ = totalSupply.sub(totalStakedSupply);
        } else {
            stakedBalance_ = staked[account];
        }

        uint256 length = tokens.length;
        rewards = new RewardAmount[](length);
        for (uint256 i = 0; i < length; i++) {
            rewards[i].token = tokens[i];
            rewards[i].amount = _earned(
                account,
                tokens[i],
                stakedBalance_,
                _reward(tokens[i])
            ).div(REWARD_RATE_PRECISION_ASSIST);
        }
        return rewards;
    }

    /* ========== STAKING VIEWS ========== */

    // Total staked balance of an account, including unstaked tokens that haven't been withdrawn
    function stakedBalance(address user)
        external
        view
        override
        returns (uint256 amount)
    {
        return staked[user];
    }

    // Total unstaked balance for an account (in the process of unstaking)
    function unstakedBalance(address user)
        external
        view
        override
        returns (TimedBalance memory balance)
    {
        balance = unstaked[user];
        if (balance.amount == 0) {
            // no record
        } else if (block.timestamp < balance.time) {
            // still unstaking
        } else {
            balance.amount = 0;
            balance.time = 0;
        }
        return balance;
    }

    // Total withdrawable balance for an account
    function withdrawableBalance(address user)
        external
        view
        override
        returns (TimedBalance memory balance)
    {
        balance = unstaked[user];
        if (balance.amount == 0) {
            // no record
        } else if (block.timestamp >= balance.time) {
            // can withdraw if not reaching expiration time
            balance.time = balance.time.add(WITHDRAW_DURATION); // calculate expiration time
            if (block.timestamp >= balance.time) {
                // reached expiration time
                balance.amount = 0;
                balance.time = 0;
            }
        } else {
            balance.amount = 0;
            balance.time = 0;
        }
        return balance;
    }

    /* ========== STAKING MANAGEMENT ========== */

    // Stake tokens to receive rewards
    function stake(uint256 amount) external {
        require(amount > 0, "PHIAT: Cannot stake 0");
        require(_msgSender() != treasury(), "PHIAT: treasury can not stake");
        _updateReward(_msgSender(), true);
        staked[_msgSender()] = staked[_msgSender()].add(amount);
        totalStakedSupply = totalStakedSupply.add(amount);
        stakingToken.safeTransferFrom(_msgSender(), address(this), amount);
        emit Staked(_msgSender(), amount);
    }

    function unstake(uint256 amount) external {
        require(amount > 0, "PHIAT: Cannot unstake 0");
        TimedBalance memory balance = unstaked[_msgSender()];
        require(
            balance.amount == 0 ||
                block.timestamp >= balance.time.add(WITHDRAW_DURATION), // expired
            "PHIAT: Cannot perform multiple unstaking at the same time"
        );
        require(
            amount <= staked[_msgSender()],
            "PHIAT: Cannot unstake more than staked amount"
        );
        balance.amount = amount;
        balance.time = block.timestamp.add(UNSTAKE_DURATION);
        unstaked[_msgSender()] = balance; // will override previously expired unstaking
        emit Unstaked(_msgSender(), amount);
    }

    function cancelUnstake() external {
        TimedBalance memory balance = unstaked[_msgSender()];
        require(
            balance.amount > 0 && block.timestamp < balance.time, // unstaking not finished
            "PHIAT: No unstaking to cancel"
        );
        delete unstaked[_msgSender()];
        emit UnstakeCancelled(_msgSender());
    }

    // Withdraw all withdrawable tokens
    function withdraw() external {
        TimedBalance memory balance = unstaked[_msgSender()];
        require(
            balance.amount > 0 &&
                block.timestamp >= balance.time && // unstaking finished
                block.timestamp < balance.time.add(WITHDRAW_DURATION), // not expired
            "PHIAT: No withdrawable token"
        );
        _updateReward(_msgSender(), true);
        delete unstaked[_msgSender()];
        if (staked[_msgSender()] == balance.amount) {
            delete staked[_msgSender()];
        } else {
            staked[_msgSender()] = staked[_msgSender()].sub(balance.amount);
        }
        totalStakedSupply = totalStakedSupply.sub(balance.amount);
        stakingToken.safeTransfer(_msgSender(), balance.amount);
        emit Withdrawn(_msgSender(), balance.amount);
    }

    // Claim all pending staking rewards
    function getReward() public override {
        _updateReward(_msgSender(), false);
        _getReward();
    }

    /* ========== INTERNAL REWARD MANAGEMENT ========== */

    // should divide by REWARD_RATE_PRECISION_ASSIST to get true reward
    // token's decimals are kept
    function _reward(address tokenAddress) internal view returns (uint256) {
        uint256 lastTimeRewardApplicable_ = lastTimeRewardApplicable(
            tokenAddress
        );
        if (
            lastTimeRewardApplicable_ ==
            tokenRewards[tokenAddress].lastUpdateTime
        ) {
            return tokenRewards[tokenAddress].rewardStored;
        } else {
            uint256 additionalReward = lastTimeRewardApplicable_
                .sub(tokenRewards[tokenAddress].lastUpdateTime)
                .mul(tokenRewards[tokenAddress].rewardRate);
            return
                tokenRewards[tokenAddress].rewardStored.add(additionalReward);
        }
    }

    // should divide by REWARD_RATE_PRECISION_ASSIST to get true earned rewards
    // token's decimals are kept
    function _earned(
        address account,
        address tokenAddress,
        uint256 stakedBalance_,
        uint256 reward
    ) internal view returns (uint256) {
        return
            stakedBalance_
                .mul(reward.sub(_userRewardPaid[account][tokenAddress]))
                .div(totalSupply)
                .add(_userRewards[account][tokenAddress]);
    }

    function _updateReward(address account, bool updateTreasury) internal {
        address thisAddress = address(this);
        uint256 treasuryBalance = totalSupply.sub(totalStakedSupply);
        if (account == treasury()) {
            // treasury info is saved in address(this) to make transferTreasury simpler
            account = thisAddress;
            updateTreasury = false; // no need to update treasury as a separate step
        }
        uint256 stakedBalance_ = account == thisAddress
            ? treasuryBalance
            : staked[account];
        uint256 length = tokens.length;
        for (uint256 i = 0; i < length; i++) {
            address token = tokens[i];
            TokenReward storage tokenReward = tokenRewards[token];

            uint256 reward = _reward(token);
            tokenReward.rewardStored = reward;
            tokenReward.lastUpdateTime = lastTimeRewardApplicable(token);

            // update account reward
            _userRewards[account][token] = _earned(
                account,
                token,
                stakedBalance_,
                reward
            );
            _userRewardPaid[account][token] = reward;
            if (updateTreasury) {
                // update treasury reward
                _userRewards[thisAddress][token] = _earned(
                    thisAddress,
                    token,
                    treasuryBalance,
                    reward
                );
                _userRewardPaid[thisAddress][token] = reward;
            }
        }
    }

    // every 24 hours treasury will check
    // if new rewards were sent to the contract or accrued via aToken interest
    // and collect treasury rewards
    function _getReward() internal {
        address account = _msgSender() == treasury()
            ? address(this)
            : _msgSender();
        uint256 length = tokens.length;
        for (uint256 i = 0; i < length; i++) {
            address token = tokens[i];
            uint256 reward = _userRewards[account][token].div(
                REWARD_RATE_PRECISION_ASSIST
            );
            TokenReward storage tokenReward = tokenRewards[token];
            uint256 tokenBalance = tokenReward.balance;
            uint256 currentBalance = IERC20(token).balanceOf(address(this));
            if (tokenBalance > currentBalance) {
                // current balance has a slight chance to be lower than stored balance
                // when no new rewards for a prolonged period,
                // and some existing rewards are collected
                // this is due to phToken's balanceOf using a scaling function
                // and therefore has a rounding issue
                tokenBalance = currentBalance;
            }
            if (
                tokenReward.periodFinish <=
                block.timestamp.add(REWARD_DURATION - 86400)
            ) {
                // update if progressed more than 1 day since last periodFinish update
                // or when token is newly added as reward token
                uint256 newlyCollectedRewards = currentBalance.sub(
                    tokenBalance
                );
                if (newlyCollectedRewards > 0) {
                    if (block.timestamp >= tokenReward.periodFinish) {
                        // token is newly added as reward token
                        tokenReward.rewardRate = newlyCollectedRewards
                            .mul(REWARD_RATE_PRECISION_ASSIST)
                            .div(REWARD_DURATION);
                    } else {
                        uint256 remainingTime = tokenReward.periodFinish.sub(
                            block.timestamp
                        ); // around 6 days
                        uint256 projectRewards = remainingTime.mul(
                            tokenReward.rewardRate
                        );
                        // use 1-day real and 6-day projection (current reward rate)
                        // to smooth our reward rate calculation
                        tokenReward.rewardRate = newlyCollectedRewards
                            .mul(REWARD_RATE_PRECISION_ASSIST)
                            .add(projectRewards)
                            .div(REWARD_DURATION);
                    }

                    tokenReward.lastUpdateTime = block.timestamp;
                    tokenReward.periodFinish = block.timestamp.add(
                        REWARD_DURATION
                    );
                    tokenBalance = currentBalance;
                }
            }
            if (tokenBalance < reward) {
                // again this may happen due to phToken balanceOf's rounding issue
                // under extreme circumstances mentioned above
                reward = tokenBalance;
                if (reward == 0) {
                    _userRewards[account][token] = 0;
                }
            }
            tokenReward.balance = tokenBalance.sub(reward);

            if (reward == 0) continue;
            _userRewards[account][token] = 0;
            IERC20(token).safeTransfer(_msgSender(), reward);
            emit RewardPaid(_msgSender(), token, reward);
        }
    }

    /* ========== RESTRICTED FUNCTIONS ========== */

    // support recovering ERC20 tokens except for staking tokens and reward tokens
    function recoverERC20(address tokenAddress) external onlyTreasury {
        require(
            tokenAddress != address(stakingToken),
            "PHIAT: Cannot recover staking token"
        );
        require(
            tokenRewards[tokenAddress].lastUpdateTime == 0,
            "PHIAT: Cannot recover reward token"
        );
        _recoverERC20(tokenAddress);
    }
}

// File: contracts/protocol/staking/PhiatToken.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.7.6;

import "../../dependencies/openzeppelin/contracts/SafeMath.sol";
import "../../dependencies/openzeppelin/contracts/Ownable.sol";
import "../../dependencies/openzeppelin/contracts/ERC20Capped.sol";
import "../../dependencies/governance/TreasuryOwnable.sol";

contract PhiatToken is Ownable, ERC20Capped, TreasuryOwnable {
    using SafeMath for uint256;

    uint256 public immutable mintLockTime; // no more mint amount change
    // can mint between start time and expiration time
    uint256 public immutable mintStartTime;
    uint256 public immutable mintExpirationTime;

    mapping(address => uint256) private _mints;

    event Mint(
        address indexed minter,
        address indexed onBehalfOf,
        uint256 amount
    );

    constructor(
        string memory symbol,
        string memory name,
        uint256 mintLockTime_,
        uint256 mintStartTime_,
        uint256 mintExpirationTime_,
        address treasury_
    )
        Ownable()
        TreasuryOwnable(treasury_)
        ERC20(name, symbol)
        ERC20Capped(55555000000000000000000000)
    {
        require(
            mintLockTime_ < mintStartTime_,
            "PHIAT: Mint should not start before mint amounts are locked"
        );
        require(
            mintStartTime_ < mintExpirationTime_,
            "PHIAT: Mint Should not expire before it starts"
        );
        mintLockTime = mintLockTime_;
        mintStartTime = mintStartTime_;
        mintExpirationTime = mintExpirationTime_;

        uint256 maxSupply = 55555000000000000000000000;
        _mints[treasury_] = maxSupply;
    }

    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal override {
        require(
            block.timestamp >= mintStartTime,
            "PHIAT: Cannot transfer before mint starts"
        );
        super._transfer(sender, recipient, amount);
    }

    function transferTreasury(
        address newTreasury
    ) external override onlyTreasury {
        require(
            newTreasury != address(0),
            "TreasuryOwnable: new treasury is the zero address"
        );
        // transfer mintable amount
        uint256 mintAmount = _mints[treasury()];
        if (mintAmount > 0) {
            delete _mints[treasury()];
            _mints[newTreasury] = _mints[newTreasury].add(mintAmount);
        }
        _transferTreasury(newTreasury);
    }

    function mintOf(address account) external view returns (uint256) {
        return _mints[account];
    }

    function mint() external {
        require(
            block.timestamp >= mintStartTime,
            "PHIAT: Cannot mint before mint started"
        );
        require(
            block.timestamp < mintExpirationTime,
            "PHIAT: Cannot mint after mint expired"
        );

        address sender = _msgSender();
        uint256 mintAmount = _mints[sender];
        require(mintAmount > 0, "PHIAT: nothing to mint");

        delete _mints[sender];
        _mint(sender, mintAmount);
        emit Mint(sender, sender, mintAmount);
    }

    function mintByTreasury(address account) external onlyTreasury {
        require(
            block.timestamp >= mintExpirationTime,
            "PHIAT: No expired token for treasury to mint before mint expired"
        );

        uint256 mintAmount = _mints[account];
        require(mintAmount > 0, "PHIAT: nothing to mint");

        delete _mints[account];
        _mint(treasury(), mintAmount);
        emit Mint(treasury(), account, mintAmount);
    }

    function setMint(address account, uint256 amount) external onlyOwner {
        require(
            block.timestamp < mintLockTime,
            "PHIAT: Cannot set mint amount after mint locked"
        );
        require(
            account != treasury(),
            "PHIAT: Should not adjust mint amount for treasury"
        );
        uint256 currentAmount = _mints[account];
        // adjust treasury's mintable amount
        _mints[treasury()] = _mints[treasury()].add(currentAmount).sub(
            amount,
            "PHIAT: amount exceeds maximum allowance"
        );
        // record new amount
        if (amount == 0) {
            delete _mints[account];
        } else {
            _mints[account] = amount;
        }
    }

    function setMints(
        address[] memory accounts,
        uint256[] memory amounts
    ) external onlyOwner {
        require(
            block.timestamp < mintLockTime,
            "PHIAT: Cannot set mint amount after mint locked"
        );
        require(accounts.length == amounts.length, "PHIAT: input mismatch");
        uint256 treasuryAmount = _mints[treasury()];
        for (uint256 i = 0; i < accounts.length; i++) {
            address account = accounts[i];
            uint256 amount = amounts[i];
            require(
                account != treasury(),
                "PHIAT: Should not adjust mint amount for treasury"
            );
            uint256 currentAmount = _mints[account];
            // adjust treasury's mintable amount
            treasuryAmount = treasuryAmount.add(currentAmount).sub(
                amount,
                "PHIAT: amount exceeds maximum allowance"
            );
            // record new amount
            if (amount == 0) {
                delete _mints[account];
            } else {
                _mints[account] = amount;
            }
        }
        // record new treasury amount
        _mints[treasury()] = treasuryAmount;
    }

    function addMint(address account, uint256 amount) external onlyOwner {
        require(
            block.timestamp < mintLockTime,
            "PHIAT: Cannot add mint amount after mint locked"
        );
        require(amount > 0, "PHIAT: Meaningless to add zero amount");
        require(
            account != treasury(),
            "PHIAT: Should not adjust mint amount for treasury"
        );

        // adjust treasury's mintable amount
        _mints[treasury()] = _mints[treasury()].sub(
            amount,
            "PHIAT: amount exceeds maximum allowance"
        );
        // record new amount
        _mints[account] = _mints[account].add(amount);
    }
}

// File: contracts/dependencies/openzeppelin/contracts/IERC20Capped.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC20Metadata.sol";

/**
 * @dev Extension of {ERC20} that adds a cap to the supply of tokens.
 */
interface IERC20Capped is IERC20Metadata {
    /**
     * @dev Returns the cap on the token's total supply.
     */
    function cap() external view returns (uint256);
}

// File: contracts/dependencies/openzeppelin/contracts/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC20.sol";
import "./SafeMath.sol";
import "./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 IERC20;` 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)
        );
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    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. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(
            data,
            "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: contracts/dependencies/openzeppelin/contracts/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b)
        internal
        pure
        returns (bool, uint256)
    {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: contracts/dependencies/openzeppelin/contracts/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./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.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * 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.
 */
abstract 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 virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the 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 virtual 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 virtual onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: contracts/dependencies/governance/TreasuryOwnable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../openzeppelin/contracts/Context.sol";

abstract contract TreasuryOwnable is Context {
    address private _treasury;

    event TreasuryTransferred(
        address indexed previousTreasury,
        address indexed newTreasury
    );

    /**
     * @dev Initializes the contract setting the given account (`treasury_`) as the initial treasury.
     */
    constructor(address treasury_) {
        _treasury = treasury_;
        emit TreasuryTransferred(address(0), treasury_);
    }

    /**
     * @dev Returns the address of the current treasury.
     */
    function treasury() public view virtual returns (address) {
        return _treasury;
    }

    /**
     * @dev Throws if called by any account other than the treasury.
     */
    modifier onlyTreasury() {
        require(
            treasury() == _msgSender(),
            "TreasuryOwnable: caller is not the treasury"
        );
        _;
    }

    /**
     * @dev Transfers treasury of the contract to a new account (`newTreasury`).
     * Can only be called by the current treasury.
     */
    function transferTreasury(address newTreasury)
        external
        virtual
        onlyTreasury
    {
        require(
            newTreasury != address(0),
            "TreasuryOwnable: new treasury is the zero address"
        );
        _transferTreasury(newTreasury);
    }

    function _transferTreasury(address newTreasury) internal virtual {
        emit TreasuryTransferred(_treasury, newTreasury);
        _treasury = newTreasury;
    }
}

// File: contracts/interfaces/IPhiatFeeDistribution.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.7.6;
pragma abicoder v2;

import "../dependencies/openzeppelin/contracts/IERC20Capped.sol";

interface IPhiatFeeDistribution {
    /* ========== STATE VARIABLES ========== */

    struct TokenReward {
        // updated via _getReward <- getReward
        uint256 periodFinish;
        // updated via _getReward <- getReward
        // every second how many rewards are accumulated for 1 wei
        // should divide by REWARD_RATE_PRECISION_ASSIST to get true reward rate
        uint256 rewardRate;
        // updated via _updateReward / _getReward <- stake / withdraw / getReward
        uint256 lastUpdateTime;
        // how much rewards have been accumulated so far
        // should divide by REWARD_RATE_PRECISION_ASSIST to get true reward
        // updated via _updateReward <- stake / withdraw / getReward
        uint256 rewardStored;
        // tracks already-added balances to handle accrued interest in phToken rewards
        // updated via _getReward <- getReward
        uint256 balance;
    }
    struct TimedBalance {
        uint256 amount;
        uint256 time; // when user can withdraw or unstaking expires
    }
    struct RewardAmount {
        address token;
        uint256 amount;
    }

    /* ========== EVENTS ========== */

    event Staked(address indexed user, uint256 amount);
    event Unstaked(address indexed user, uint256 amount);
    event UnstakeCancelled(address indexed user);
    event Withdrawn(address indexed user, uint256 receivedAmount);
    event RewardPaid(
        address indexed user,
        address indexed rewardToken,
        uint256 reward
    );

    function stakingToken() external view returns (IERC20Capped);

    function stakingTokenPrecision() external view returns (uint256);

    function totalSupply() external view returns (uint256);

    function totalStakedSupply() external view returns (uint256);

    function REWARD_DURATION() external view returns (uint256);

    function UNSTAKE_DURATION() external view returns (uint256);

    function WITHDRAW_DURATION() external view returns (uint256);

    function REWARD_RATE_PRECISION_ASSIST() external view returns (uint256);

    /* ========== REWARD VIEWS ========== */

    function lastTimeRewardApplicable(address tokenAddress)
        external
        view
        returns (uint256);

    // should divide by REWARD_RATE_PRECISION_ASSIST to get true reward per token
    // token's decimals are kept
    // staking token's decimals are removed
    function rewardPerToken(address tokenAddress)
        external
        view
        returns (uint256);

    function getRewardForDuration(address tokenAddress)
        external
        view
        returns (uint256);

    // Address and claimable amount of all reward tokens for the given account
    function claimableRewards(address account)
        external
        view
        returns (RewardAmount[] memory rewards);

    /* ========== STAKING VIEWS ========== */

    // Total staked balance of an account, including unstaked tokens that haven't been withdrawn
    function stakedBalance(address user) external view returns (uint256 amount);

    // Total unstaked balance for an account (in the process of unstaking)
    function unstakedBalance(address user)
        external
        view
        returns (TimedBalance memory balance);

    // Total withdrawable balance for an account
    function withdrawableBalance(address user)
        external
        view
        returns (TimedBalance memory balance);

    function getReward() external;
}

// File: contracts/protocol/staking/ERC20Recoverable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../../dependencies/openzeppelin/contracts/Context.sol";
import "../../dependencies/openzeppelin/contracts/IERC20.sol";
import "../../dependencies/openzeppelin/contracts/SafeERC20.sol";

abstract contract ERC20Recoverable is Context {
    using SafeERC20 for IERC20;

    event Recovered(address token, address account, uint256 amount);

    function _recoverERC20(address tokenAddress) internal {
        IERC20 token = IERC20(tokenAddress);
        uint256 tokenAmount = token.balanceOf(address(this));
        require(tokenAmount > 0, "ERC20Recoverable: no token to recover");
        token.safeTransfer(_msgSender(), tokenAmount);
        emit Recovered(tokenAddress, _msgSender(), tokenAmount);
    }
}

// File: contracts/dependencies/openzeppelin/contracts/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity 0.7.6;

import "./IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// File: contracts/dependencies/openzeppelin/contracts/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

// File: contracts/dependencies/openzeppelin/contracts/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(
            address(this).balance >= amount,
            "Address: insufficient balance"
        );

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{value: amount}("");
        require(
            success,
            "Address: unable to send value, recipient may have reverted"
        );
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return
            functionCallWithValue(
                target,
                data,
                value,
                "Address: low-level call with value failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(
            address(this).balance >= value,
            "Address: insufficient balance for call"
        );
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{value: value}(
            data
        );
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data)
        internal
        view
        returns (bytes memory)
    {
        return
            functionStaticCall(
                target,
                data,
                "Address: low-level static call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data)
        internal
        returns (bytes memory)
    {
        return
            functionDelegateCall(
                target,
                data,
                "Address: low-level delegate call failed"
            );
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: contracts/dependencies/openzeppelin/contracts/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: contracts/dependencies/openzeppelin/contracts/ERC20Capped.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC20Capped.sol";
import "./ERC20.sol";

/**
 * @dev Extension of {ERC20} that adds a cap to the supply of tokens.
 */
abstract contract ERC20Capped is IERC20Capped, ERC20 {
    using SafeMath for uint256;

    uint256 private _cap;

    /**
     * @dev Sets the value of the `cap`. This value is immutable, it can only be
     * set once during construction.
     */
    constructor(uint256 cap_) internal {
        require(cap_ > 0, "ERC20Capped: cap is 0");
        _cap = cap_;
    }

    /**
     * @dev Returns the cap on the token's total supply.
     */
    function cap() public view virtual override returns (uint256) {
        return _cap;
    }

    /**
     * @dev See {ERC20-_beforeTokenTransfer}.
     *
     * Requirements:
     *
     * - minted tokens must not cause the total supply to go over the cap.
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual override {
        super._beforeTokenTransfer(from, to, amount);

        if (from == address(0)) {
            // When minting tokens
            require(
                totalSupply().add(amount) <= cap(),
                "ERC20Capped: cap exceeded"
            );
        }
    }
}

// File: contracts/dependencies/openzeppelin/contracts/ERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./Context.sol";
import "./IERC20Metadata.sol";
import "./SafeMath.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20Metadata {
    using SafeMath for uint256;

    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account)
        public
        view
        virtual
        override
        returns (uint256)
    {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender)
        public
        view
        virtual
        override
        returns (uint256)
    {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        uint256 currentAllowance = allowance(sender, _msgSender());
        if (currentAllowance != type(uint256).max) {
            uint256 decreasedAllowance = currentAllowance.sub(
                amount,
                "ERC20: transfer amount exceeds allowance"
            );

            _approve(sender, _msgSender(), decreasedAllowance);
        }
        _transfer(sender, recipient, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue)
        public
        virtual
        returns (bool)
    {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].add(addedValue)
        );
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue)
        public
        virtual
        returns (bool)
    {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].sub(
                subtractedValue,
                "ERC20: decreased allowance below zero"
            )
        );
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(
            amount,
            "ERC20: transfer amount exceeds balance"
        );
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(
            amount,
            "ERC20: burn amount exceeds balance"
        );
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}