// File: contracts/MonasteryTreasury.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

import "./libraries/Ownable.sol";
import "./libraries/SafeMath.sol";
import "./libraries/ERC20.sol";

interface IMONKERC20 {
    function burnFrom(address account_, uint256 amount_) external;
}

interface IBondCalculator {
  function valuation( address pair_, uint amount_ ) external view returns ( uint _value );
}

contract MonasteryTreasury is Ownable {

    using SafeMath for uint;
    using SafeERC20 for IERC20;

    event Deposit( address indexed token, uint amount, uint value );
    event Withdrawal( address indexed token, uint amount, uint value );
    event CreateDebt( address indexed debtor, address indexed token, uint amount, uint value );
    event RepayDebt( address indexed debtor, address indexed token, uint amount, uint value );
    event ReservesManaged( address indexed token, uint amount );
    event ReservesUpdated( uint indexed totalReserves );
    event ReservesAudited( uint indexed totalReserves );
    event RewardsMinted( address indexed caller, address indexed recipient, uint amount );
    event ChangeQueued( MANAGING indexed managing, address queued );
    event ChangeActivated( MANAGING indexed managing, address activated, bool result );

    enum MANAGING { RESERVEDEPOSITOR, RESERVESPENDER, RESERVETOKEN, RESERVEMANAGER, LIQUIDITYDEPOSITOR, LIQUIDITYTOKEN, LIQUIDITYMANAGER, DEBTOR, REWARDMANAGER, ZEN }

    address public immutable MONK;
    uint public immutable blocksNeededForQueue;

    address[] public reserveTokens; // Push only, beware false-positives.
    mapping( address => bool ) public isReserveToken;
    mapping( address => uint ) public reserveTokenQueue; // Delays changes to mapping.

    address[] public reserveDepositors; // Push only, beware false-positives. Only for viewing.
    mapping( address => bool ) public isReserveDepositor;
    mapping( address => uint ) public reserveDepositorQueue; // Delays changes to mapping.

    address[] public reserveSpenders; // Push only, beware false-positives. Only for viewing.
    mapping( address => bool ) public isReserveSpender;
    mapping( address => uint ) public reserveSpenderQueue; // Delays changes to mapping.

    address[] public liquidityTokens; // Push only, beware false-positives.
    mapping( address => bool ) public isLiquidityToken;
    mapping( address => uint ) public LiquidityTokenQueue; // Delays changes to mapping.

    address[] public liquidityDepositors; // Push only, beware false-positives. Only for viewing.
    mapping( address => bool ) public isLiquidityDepositor;
    mapping( address => uint ) public LiquidityDepositorQueue; // Delays changes to mapping.

    mapping( address => address ) public bondCalculator; // bond calculator for liquidity token

    address[] public reserveManagers; // Push only, beware false-positives. Only for viewing.
    mapping( address => bool ) public isReserveManager;
    mapping( address => uint ) public ReserveManagerQueue; // Delays changes to mapping.

    address[] public liquidityManagers; // Push only, beware false-positives. Only for viewing.
    mapping( address => bool ) public isLiquidityManager;
    mapping( address => uint ) public LiquidityManagerQueue; // Delays changes to mapping.

    address[] public debtors; // Push only, beware false-positives. Only for viewing.
    mapping( address => bool ) public isDebtor;
    mapping( address => uint ) public debtorQueue; // Delays changes to mapping.
    mapping( address => uint ) public debtorBalance;

    address[] public rewardManagers; // Push only, beware false-positives. Only for viewing.
    mapping( address => bool ) public isRewardManager;
    mapping( address => uint ) public rewardManagerQueue; // Delays changes to mapping.

    address public ZEN;
    uint public ZENQueue; // Delays change to ZEN address

    uint public totalReserves; // Risk-free value of all assets
    uint public totalDebt;

    constructor (
        address _MONK,
        address _DAI,
        address _MONKDAI,
        address _bondCalculator,
        uint _blocksNeededForQueue
    ) {
        require( _MONK != address(0) );
        MONK = _MONK;

        isReserveToken[ _DAI ] = true;
        reserveTokens.push( _DAI );

        isLiquidityToken[ _MONKDAI ] = true;
        liquidityTokens.push( _MONKDAI );
        bondCalculator[_MONKDAI] = _bondCalculator;

        blocksNeededForQueue = _blocksNeededForQueue;
    }

    /**
        @notice allow approved address to deposit an asset for MONK
        @param _amount uint
        @param _token address
        @param _profit uint
        @return send_ uint
     */
    function deposit( uint _amount, address _token, uint _profit ) external returns ( uint send_ ) {
        require( isReserveToken[ _token ] || isLiquidityToken[ _token ], "Not accepted" );
        IERC20( _token ).safeTransferFrom( msg.sender, address(this), _amount );

        if ( isReserveToken[ _token ] ) {
            require( isReserveDepositor[ msg.sender ], "Not approved" );
        } else {
            require( isLiquidityDepositor[ msg.sender ], "Not approved" );
        }

        uint value = valueOfToken(_token, _amount);
        // mint MONK needed and store amount of rewards for distribution
        send_ = value.sub( _profit );
        IERC20Mintable( MONK ).mint( msg.sender, send_ );

        totalReserves = totalReserves.add( value );
        emit ReservesUpdated( totalReserves );

        emit Deposit( _token, _amount, value );
    }

    function depositICO( uint _amount, address _token) external {
        require( isReserveToken[ _token ]);
        require( isReserveDepositor[ msg.sender ], "Not approved" );
        IERC20( _token ).safeTransferFrom( msg.sender, address(this), _amount );

        uint value = valueOfToken(_token, _amount);
        totalReserves = totalReserves.add( value );
        
        emit ReservesUpdated( totalReserves );
        emit Deposit( _token, _amount, value );
    }

    /**
        @notice allow approved address to burn MONK for reserves
        @param _amount uint
        @param _token address
     */
    function withdraw( uint _amount, address _token ) external {
        require( isReserveToken[ _token ], "Not accepted" ); // Only reserves can be used for redemptions
        require( isReserveSpender[ msg.sender ] == true, "Not approved" );

        uint value = valueOfToken( _token, _amount );
        IMONKERC20( MONK ).burnFrom( msg.sender, value );

        totalReserves = totalReserves.sub( value );
        emit ReservesUpdated( totalReserves );

        IERC20( _token ).safeTransfer( msg.sender, _amount );

        emit Withdrawal( _token, _amount, value );
    }

    /**
        @notice allow approved address to borrow reserves
        @param _amount uint
        @param _token address
     */
    function incurDebt( uint _amount, address _token ) external {
        require( isDebtor[ msg.sender ], "Not approved" );
        require( isReserveToken[ _token ], "Not accepted" );

        uint value = valueOfToken( _token, _amount );

        uint maximumDebt = IERC20( ZEN ).balanceOf( msg.sender ); // Can only borrow against ZEN held
        uint availableDebt = maximumDebt.sub( debtorBalance[ msg.sender ] );
        require( value <= availableDebt, "Exceeds debt limit" );

        debtorBalance[ msg.sender ] = debtorBalance[ msg.sender ].add( value );
        totalDebt = totalDebt.add( value );

        totalReserves = totalReserves.sub( value );
        emit ReservesUpdated( totalReserves );

        IERC20( _token ).transfer( msg.sender, _amount );

        emit CreateDebt( msg.sender, _token, _amount, value );
    }

    /**
        @notice allow approved address to repay borrowed reserves with reserves
        @param _amount uint
        @param _token address
     */
    function repayDebtWithReserve( uint _amount, address _token ) external {
        require( isDebtor[ msg.sender ], "Not approved" );
        require( isReserveToken[ _token ], "Not accepted" );

        IERC20( _token ).safeTransferFrom( msg.sender, address(this), _amount );

        uint value = valueOfToken( _token, _amount );
        debtorBalance[ msg.sender ] = debtorBalance[ msg.sender ].sub( value );
        totalDebt = totalDebt.sub( value );

        totalReserves = totalReserves.add( value );
        emit ReservesUpdated( totalReserves );

        emit RepayDebt( msg.sender, _token, _amount, value );
    }

    /**
        @notice allow approved address to repay borrowed reserves with MONK
        @param _amount uint
     */
    function repayDebtWithMONK( uint _amount ) external {
        require( isDebtor[ msg.sender ], "Not approved" );

        IMONKERC20( MONK ).burnFrom( msg.sender, _amount );

        debtorBalance[ msg.sender ] = debtorBalance[ msg.sender ].sub( _amount );
        totalDebt = totalDebt.sub( _amount );

        emit RepayDebt( msg.sender, MONK, _amount, _amount );
    }

    /**
        @notice allow approved address to withdraw assets
        @param _token address
        @param _amount uint
     */
    function manage( address _token, uint _amount ) external {
        if( isLiquidityToken[ _token ] ) {
            require( isLiquidityManager[ msg.sender ], "Not approved" );
        } else {
            require( isReserveManager[ msg.sender ], "Not approved" );
        }

        uint value = valueOfToken(_token, _amount);
        require( value <= excessReserves(), "Insufficient reserves" );

        totalReserves = totalReserves.sub( value );
        emit ReservesUpdated( totalReserves );

        IERC20( _token ).safeTransfer( msg.sender, _amount );

        emit ReservesManaged( _token, _amount );
    }

    /**
        @notice send epoch reward to staking contract
     */
    function mintRewards( address _recipient, uint _amount ) external {
        require( isRewardManager[ msg.sender ], "Not approved" );
        require( _amount <= excessReserves(), "Insufficient reserves" );

        IERC20Mintable( MONK ).mint( _recipient, _amount );

        emit RewardsMinted( msg.sender, _recipient, _amount );
    }

    /**
        @notice returns excess reserves not backing tokens
        @return uint
     */
    function excessReserves() public view returns ( uint ) {
        return totalReserves.sub( IERC20( MONK ).totalSupply().sub( totalDebt ) );
    }

    /**
        @notice takes inventory of all tracked assets
        @notice always consolidate to recognized reserves before audit
     */
    function auditReserves() external onlyOwner() {
        uint reserves;
        for( uint i = 0; i < reserveTokens.length; i++ ) {
            reserves = reserves.add (
                valueOfToken( reserveTokens[ i ], IERC20( reserveTokens[ i ] ).balanceOf( address(this) ) )
            );
        }
        for( uint i = 0; i < liquidityTokens.length; i++ ) {
            reserves = reserves.add (
                valueOfToken( liquidityTokens[ i ], IERC20( liquidityTokens[ i ] ).balanceOf( address(this) ) )
            );
        }
        totalReserves = reserves;
        emit ReservesUpdated( reserves );
        emit ReservesAudited( reserves );
    }

    /**
        @notice returns MONK valuation of asset
        @param _token address
        @param _amount uint
        @return value_ uint
     */
    function valueOfToken( address _token, uint _amount ) public view returns ( uint value_ ) {
        if ( isReserveToken[ _token ] ) {
            // convert amount to match MONK decimals
            value_ = _amount.mul( 10 ** IERC20( MONK ).decimals() ).div( 10 ** IERC20( _token ).decimals() );
        } else if ( isLiquidityToken[ _token ] ) {
            value_ = IBondCalculator( bondCalculator[ _token ] ).valuation( _token, _amount );
        }
    }

    /**
        @notice queue address to change boolean in mapping
        @param _managing MANAGING
        @param _address address
        @return bool
     */
    function queue( MANAGING _managing, address _address ) external onlyOwner() returns ( bool ) {
        require( _address != address(0) );
        if ( _managing == MANAGING.RESERVEDEPOSITOR ) { // 0
            reserveDepositorQueue[ _address ] = block.number.add( blocksNeededForQueue );
        } else if ( _managing == MANAGING.RESERVESPENDER ) { // 1
            reserveSpenderQueue[ _address ] = block.number.add( blocksNeededForQueue );
        } else if ( _managing == MANAGING.RESERVETOKEN ) { // 2
            reserveTokenQueue[ _address ] = block.number.add( blocksNeededForQueue );
        } else if ( _managing == MANAGING.RESERVEMANAGER ) { // 3
            ReserveManagerQueue[ _address ] = block.number.add( blocksNeededForQueue.mul( 2 ) );
        } else if ( _managing == MANAGING.LIQUIDITYDEPOSITOR ) { // 4
            LiquidityDepositorQueue[ _address ] = block.number.add( blocksNeededForQueue );
        } else if ( _managing == MANAGING.LIQUIDITYTOKEN ) { // 5
            LiquidityTokenQueue[ _address ] = block.number.add( blocksNeededForQueue );
        } else if ( _managing == MANAGING.LIQUIDITYMANAGER ) { // 6
            LiquidityManagerQueue[ _address ] = block.number.add( blocksNeededForQueue.mul( 2 ) );
        } else if ( _managing == MANAGING.DEBTOR ) { // 7
            debtorQueue[ _address ] = block.number.add( blocksNeededForQueue );
        } else if ( _managing == MANAGING.REWARDMANAGER ) { // 8
            rewardManagerQueue[ _address ] = block.number.add( blocksNeededForQueue );
        } else if ( _managing == MANAGING.ZEN ) { // 9
            ZENQueue = block.number.add( blocksNeededForQueue );
        } else return false;

        emit ChangeQueued( _managing, _address );
        return true;
    }

    /**
        @notice verify queue then set boolean in mapping
        @param _managing MANAGING
        @param _address address
        @param _calculator address
        @return bool
     */
    function toggle( MANAGING _managing, address _address, address _calculator ) external onlyOwner() returns ( bool ) {
        require( _address != address(0) );
        bool result;
        if ( _managing == MANAGING.RESERVEDEPOSITOR ) { // 0
            if ( requirements( reserveDepositorQueue, isReserveDepositor, _address ) ) {
                reserveDepositorQueue[ _address ] = 0;
                if( !listContains( reserveDepositors, _address ) ) {
                    reserveDepositors.push( _address );
                }
            }
            result = !isReserveDepositor[ _address ];
            isReserveDepositor[ _address ] = result;

        } else if ( _managing == MANAGING.RESERVESPENDER ) { // 1
            if ( requirements( reserveSpenderQueue, isReserveSpender, _address ) ) {
                reserveSpenderQueue[ _address ] = 0;
                if( !listContains( reserveSpenders, _address ) ) {
                    reserveSpenders.push( _address );
                }
            }
            result = !isReserveSpender[ _address ];
            isReserveSpender[ _address ] = result;

        } else if ( _managing == MANAGING.RESERVETOKEN ) { // 2
            if ( requirements( reserveTokenQueue, isReserveToken, _address ) ) {
                reserveTokenQueue[ _address ] = 0;
                if( !listContains( reserveTokens, _address ) ) {
                    reserveTokens.push( _address );
                }
            }
            result = !isReserveToken[ _address ];
            isReserveToken[ _address ] = result;

        } else if ( _managing == MANAGING.RESERVEMANAGER ) { // 3
            if ( requirements( ReserveManagerQueue, isReserveManager, _address ) ) {
                reserveManagers.push( _address );
                ReserveManagerQueue[ _address ] = 0;
                if( !listContains( reserveManagers, _address ) ) {
                    reserveManagers.push( _address );
                }
            }
            result = !isReserveManager[ _address ];
            isReserveManager[ _address ] = result;

        } else if ( _managing == MANAGING.LIQUIDITYDEPOSITOR ) { // 4
            if ( requirements( LiquidityDepositorQueue, isLiquidityDepositor, _address ) ) {
                liquidityDepositors.push( _address );
                LiquidityDepositorQueue[ _address ] = 0;
                if( !listContains( liquidityDepositors, _address ) ) {
                    liquidityDepositors.push( _address );
                }
            }
            result = !isLiquidityDepositor[ _address ];
            isLiquidityDepositor[ _address ] = result;

        } else if ( _managing == MANAGING.LIQUIDITYTOKEN ) { // 5
            if ( requirements( LiquidityTokenQueue, isLiquidityToken, _address ) ) {
                LiquidityTokenQueue[ _address ] = 0;
                if( !listContains( liquidityTokens, _address ) ) {
                    liquidityTokens.push( _address );
                }
            }
            result = !isLiquidityToken[ _address ];
            isLiquidityToken[ _address ] = result;
            bondCalculator[ _address ] = _calculator;

        } else if ( _managing == MANAGING.LIQUIDITYMANAGER ) { // 6
            if ( requirements( LiquidityManagerQueue, isLiquidityManager, _address ) ) {
                LiquidityManagerQueue[ _address ] = 0;
                if( !listContains( liquidityManagers, _address ) ) {
                    liquidityManagers.push( _address );
                }
            }
            result = !isLiquidityManager[ _address ];
            isLiquidityManager[ _address ] = result;

        } else if ( _managing == MANAGING.DEBTOR ) { // 7
            if ( requirements( debtorQueue, isDebtor, _address ) ) {
                debtorQueue[ _address ] = 0;
                if( !listContains( debtors, _address ) ) {
                    debtors.push( _address );
                }
            }
            result = !isDebtor[ _address ];
            isDebtor[ _address ] = result;

        } else if ( _managing == MANAGING.REWARDMANAGER ) { // 8
            if ( requirements( rewardManagerQueue, isRewardManager, _address ) ) {
                rewardManagerQueue[ _address ] = 0;
                if( !listContains( rewardManagers, _address ) ) {
                    rewardManagers.push( _address );
                }
            }
            result = !isRewardManager[ _address ];
            isRewardManager[ _address ] = result;

        } else if ( _managing == MANAGING.ZEN ) { // 9
            ZENQueue = 0;
            ZEN = _address;
            result = true;

        } else return false;

        emit ChangeActivated( _managing, _address, result );
        return true;
    }

    /**
        @notice checks requirements and returns altered structs
        @param queue_ mapping( address => uint )
        @param status_ mapping( address => bool )
        @param _address address
        @return bool
     */
    function requirements(
        mapping( address => uint ) storage queue_,
        mapping( address => bool ) storage status_,
        address _address
    ) internal view returns ( bool ) {
        if ( !status_[ _address ] ) {
            require( queue_[ _address ] != 0, "Must queue" );
            require( queue_[ _address ] <= block.number, "Queue not expired" );
            return true;
        } return false;
    }

    /**
        @notice checks array to ensure against duplicate
        @param _list address[]
        @param _token address
        @return bool
     */
    function listContains( address[] storage _list, address _token ) internal view returns ( bool ) {
        for( uint i = 0; i < _list.length; i++ ) {
            if( _list[ i ] == _token ) {
                return true;
            }
        }
        return false;
    }
}

// File: contracts/libraries/Ownable.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

interface IOwnable {
  function owner() external view returns (address);

  function renounceManagement() external;

  function pushManagement( address newOwner_ ) external;

  function pullManagement() external;
}

contract Ownable is IOwnable {

    address internal _owner;
    address internal _newOwner;

    event OwnershipPushed(address indexed previousOwner, address indexed newOwner);
    event OwnershipPulled(address indexed previousOwner, address indexed newOwner);

    constructor () {
        _owner = msg.sender;
        emit OwnershipPushed( address(0), _owner );
    }

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

    modifier onlyOwner() {
        require( _owner == msg.sender, "Ownable: caller is not the owner" );
        _;
    }

    function renounceManagement() public virtual override onlyOwner() {
        emit OwnershipPushed( _owner, address(0) );
        _owner = address(0);
    }

    function pushManagement( address newOwner_ ) public virtual override onlyOwner() {
        require( newOwner_ != address(0), "Ownable: new owner is the zero address");
        emit OwnershipPushed( _owner, newOwner_ );
        _newOwner = newOwner_;
    }

    function pullManagement() public virtual override {
        require( msg.sender == _newOwner, "Ownable: must be new owner to pull");
        emit OwnershipPulled( _owner, _newOwner );
        _owner = _newOwner;
    }
}

// File: contracts/libraries/SafeMath.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

library SafeMath {

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

        return c;
    }

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

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

        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {

        if (a == 0) {
            return 0;
        }

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

        return c;
    }

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

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    function sqrrt(uint256 a) internal pure returns (uint c) {
        if (a > 3) {
            c = a;
            uint b = add( div( a, 2), 1 );
            while (b < c) {
                c = b;
                b = div( add( div( a, b ), b), 2 );
            }
        } else if (a != 0) {
            c = 1;
        }
    }
}

// File: contracts/libraries/ERC20.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

import "../interfaces/IERC20.sol";
import "./SafeMath.sol";
import "./Counters.sol";
import "./Address.sol";

abstract contract ERC20 is IERC20 {

    using SafeMath for uint256;

    // TODO comment actual hash value.
    bytes32 constant private ERC20TOKEN_ERC1820_INTERFACE_ID = keccak256( "ERC20Token" );

    mapping (address => uint256) internal _balances;

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

    uint256 internal _totalSupply;

    string internal _name;

    string internal _symbol;

    uint8 internal _decimals;

    constructor (string memory name_, string memory symbol_, uint8 decimals_) {
        _name = name_;
        _symbol = symbol_;
        _decimals = decimals_;
    }

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

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

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

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

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

    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

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

    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

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

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

    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);
    }

    function _mint(address account_, uint256 ammount_) internal virtual {
        require(account_ != address(0), "ERC20: mint to the zero address");
        _beforeTokenTransfer(address( this ), account_, ammount_);
        _totalSupply = _totalSupply.add(ammount_);
        _balances[account_] = _balances[account_].add(ammount_);
        emit Transfer(address( this ), account_, ammount_);
    }

    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);
    }

    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);
    }

  function _beforeTokenTransfer( address from_, address to_, uint256 amount_ ) internal virtual { }
}

interface IERC2612Permit {

    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    function nonces(address owner) external view returns (uint256);
}


abstract contract ERC20Permit is ERC20, IERC2612Permit {
    using Counters for Counters.Counter;

    mapping(address => Counters.Counter) private _nonces;

    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;

    bytes32 public DOMAIN_SEPARATOR;

    constructor() {
        uint256 chainID;
        assembly {
            chainID := chainid()
        }

        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
                keccak256(bytes(name())),
                keccak256(bytes("1")), // Version
                chainID,
                address(this)
            )
        );
    }

    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public virtual override {
        require(block.timestamp <= deadline, "Permit: expired deadline");

        bytes32 hashStruct =
            keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, amount, _nonces[owner].current(), deadline));

        bytes32 _hash = keccak256(abi.encodePacked(uint16(0x1901), DOMAIN_SEPARATOR, hashStruct));

        address signer = ecrecover(_hash, v, r, s);
        require(signer != address(0) && signer == owner, "Permit: Invalid signature");

        _nonces[owner].increment();
        _approve(owner, spender, amount);
    }

    function nonces(address owner) public view override returns (uint256) {
        return _nonces[owner].current();
    }
}

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

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

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

    function safeApprove(IERC20 token, address spender, uint256 value) internal {

        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

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

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

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

        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/interfaces/IERC20.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity >=0.5.0;

interface IERC20 {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);
}

interface IERC20Mintable {
  function mint( uint256 amount_ ) external;

  function mint( address account_, uint256 ammount_ ) external;
}

// File: contracts/libraries/Counters.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

import "./SafeMath.sol";

library Counters {
    using SafeMath for uint256;

    struct Counter {

        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        counter._value += 1;
    }

    function decrement(Counter storage counter) internal {
        counter._value = counter._value.sub(1);
    }
}

// File: contracts/libraries/Address.sol



// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

library Address {

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

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    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");
    }

    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    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");
    }

    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);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        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);
            }
        }
    }

    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    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);
    }

    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    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 {
            if (returndata.length > 0) {

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }

    function addressToString(address _address) internal pure returns(string memory) {
        bytes32 _bytes = bytes32(uint256(_address));
        bytes memory HEX = "0123456789abcdef";
        bytes memory _addr = new bytes(42);

        _addr[0] = '0';
        _addr[1] = 'x';

        for(uint256 i = 0; i < 20; i++) {
            _addr[2+i*2] = HEX[uint8(_bytes[i + 12] >> 4)];
            _addr[3+i*2] = HEX[uint8(_bytes[i + 12] & 0x0f)];
        }

        return string(_addr);

    }
}