// File: contracts/VotingEscrow.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

/**
 * @title Voting Escrow
 * @notice Votes have a weight depending on time, so that users are
 *         committed to the future of (whatever they are voting for)
 * @dev Vote weight decays linearly over time. Lock time cannot be
 *      more than `MAXTIME` (2 years).
 *
 * # Voting escrow to have time-weighted votes
 * # Votes have a weight depending on time, so that users are committed
 * # to the future of (whatever they are voting for).
 * # The weight in this implementation is linear, and lock cannot be more than maxtime:
 * # w ^
 * # 1 +        /
 * #   |      /
 * #   |    /
 * #   |  /
 * #   |/
 * # 0 +--------+------> time
 * #       maxtime (2 years?)
 */

import { Ownable2Step } from "@openzeppelin/contracts/access/Ownable2Step.sol";
import { ReentrancyGuard } from "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import { IERC20 } from "@openzeppelin/contracts/interfaces/IERC20.sol";
import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import { IVotingEscrow } from "./interfaces/IVotingEscrow.sol";

/* We cannot really do block numbers per se b/c slope is per time, not per block
 * and per block could be fairly bad b/c Ethereum changes blocktimes.
 * What we can do is to extrapolate ***At functions */

contract VotingEscrow is IVotingEscrow, Ownable2Step, ReentrancyGuard {
    using SafeERC20 for IERC20;

    enum DepositType {
        DEPOSIT_FOR_TYPE,
        CREATE_LOCK_TYPE,
        INCREASE_LOCK_AMOUNT,
        INCREASE_UNLOCK_TIME
    }

    event Deposit(
        address indexed provider, uint256 value, uint256 indexed locktime, DepositType deposit_type, uint256 ts
    );
    event Withdraw(address indexed provider, uint256 value, uint256 ts);
    event Supply(uint256 prevSupply, uint256 supply);

    uint256 public constant override MAXTIME = 2 * 365 * 86_400;
    uint256 internal constant WEEK = 1 weeks;
    int128 internal constant iMAXTIME = 2 * 365 * 86_400;
    uint256 internal constant MULTIPLIER = 1 ether;

    uint256 public immutable override MINTIME;
    address public immutable override token;
    uint256 public override supply;
    bool public override unlocked;

    mapping(address => LockedBalance) public override locked;

    uint256 public override epoch;
    mapping(uint256 => Point) public override point_history; // epoch -> unsigned point
    mapping(address => Point[1_000_000_000]) public override user_point_history; // user -> Point[user_epoch]
    mapping(address => uint256) public override user_point_epoch;
    mapping(uint256 => int128) public override slope_changes; // time -> signed slope change

    // Aragon's view methods for compatibility
    address public controller;
    bool public transfersEnabled;

    string public constant name = "veRAFT";
    string public constant symbol = "veRAFT";
    string public constant version = "1.0.0";
    uint8 public constant decimals = 18;

    // Whitelisted (smart contract) wallets which are allowed to deposit
    // The goal is to prevent tokenizing the escrow
    mapping(address => bool) public contracts_whitelist;

    /// @notice Contract constructor
    /// @param token_addr `ERC20CRV` token address
    constructor(address token_addr, uint256 min_time) {
        token = token_addr;
        point_history[0].blk = block.number;
        point_history[0].ts = block.timestamp;
        controller = msg.sender;
        transfersEnabled = true;
        MINTIME = min_time;
    }

    modifier onlyUserOrWhitelist() {
        if (msg.sender != tx.origin) {
            require(contracts_whitelist[msg.sender], "Smart contract not allowed");
        }
        _;
    }

    modifier onlyWhitelist() {
        require(contracts_whitelist[msg.sender], "Only whitelisted addresses");
        _;
    }

    modifier notUnlocked() {
        require(!unlocked, "unlocked globally");
        _;
    }

    /// @notice Add address to whitelist smart contract depositors `addr`
    /// @param addr Address to be whitelisted
    function add_to_whitelist(address addr) external onlyOwner {
        contracts_whitelist[addr] = true;
    }

    /// @notice Remove a smart contract address from whitelist
    /// @param addr Address to be removed from whitelist
    function remove_from_whitelist(address addr) external onlyOwner {
        contracts_whitelist[addr] = false;
    }

    /// @notice Unlock all locked balances
    function unlock() external onlyOwner {
        unlocked = true;
    }

    /// @notice Get the most recently recorded rate of voting power decrease for `_addr`
    /// @param addr Address of the user wallet
    /// @return Value of the slope
    function get_last_user_slope(address addr) external view returns (int128) {
        uint256 uepoch = user_point_epoch[addr];
        return user_point_history[addr][uepoch].slope;
    }

    /// @notice Get the timestamp for checkpoint `_idx` for `_addr`
    /// @param _addr User wallet address
    /// @param _idx User epoch number
    /// @return Epoch time of the checkpoint
    function user_point_history__ts(address _addr, uint256 _idx) external view returns (uint256) {
        return user_point_history[_addr][_idx].ts;
    }

    /// @notice Get timestamp when `_addr`'s lock finishes
    /// @param _addr User wallet address
    /// @return Epoch time of the lock end
    function locked__end(address _addr) external view returns (uint256) {
        return locked[_addr].end;
    }

    /// @notice Record global and per-user data to checkpoint
    /// @param _addr User's wallet address. No user checkpoint if 0x0
    /// @param old_locked Pevious locked amount / end lock time for the user
    /// @param new_locked New locked amount / end lock time for the user
    function _checkpoint(address _addr, LockedBalance memory old_locked, LockedBalance memory new_locked) internal {
        Point memory u_old;
        Point memory u_new;
        int128 old_dslope = 0;
        int128 new_dslope = 0;
        uint256 _epoch = epoch;

        if (_addr != address(0x0)) {
            // Calculate slopes and biases
            // Kept at zero when they have to
            if (old_locked.end > block.timestamp && old_locked.amount > 0) {
                u_old.slope = old_locked.amount / iMAXTIME;
                u_old.bias = u_old.slope * int128(int256(old_locked.end - block.timestamp));
            }
            if (new_locked.end > block.timestamp && new_locked.amount > 0) {
                u_new.slope = new_locked.amount / iMAXTIME;
                u_new.bias = u_new.slope * int128(int256(new_locked.end - block.timestamp));
            }

            // Read values of scheduled changes in the slope
            // old_locked.end can be in the past and in the future
            // new_locked.end can ONLY by in the FUTURE unless everything expired: than zeros
            old_dslope = slope_changes[old_locked.end];
            if (new_locked.end != 0) {
                if (new_locked.end == old_locked.end) {
                    new_dslope = old_dslope;
                } else {
                    new_dslope = slope_changes[new_locked.end];
                }
            }
        }

        Point memory last_point = Point({ bias: 0, slope: 0, ts: block.timestamp, blk: block.number });
        if (_epoch > 0) {
            last_point = point_history[_epoch];
        }
        uint256 last_checkpoint = last_point.ts;
        // initial_last_point is used for extrapolation to calculate block number
        // (approximately, for *At methods) and save them
        // as we cannot figure that out exactly from inside the contract

        uint256 initial_last_point_ts = last_point.ts;
        uint256 initial_last_point_blk = last_point.blk;

        uint256 block_slope = 0; // dblock/dt
        if (block.timestamp > last_point.ts) {
            block_slope = (MULTIPLIER * (block.number - last_point.blk)) / (block.timestamp - last_point.ts);
        }
        // If last point is already recorded in this block, slope=0
        // But that's ok b/c we know the block in such case

        // Go over weeks to fill history and calculate what the current point is
        uint256 t_i = (last_checkpoint / WEEK) * WEEK;
        for (uint256 i = 0; i < 255; ++i) {
            // Hopefully it won't happen that this won't get used in 5 years!
            // If it does, users will be able to withdraw but vote weight will be broken
            t_i += WEEK;
            int128 d_slope = 0;
            if (t_i > block.timestamp) {
                t_i = block.timestamp;
            } else {
                d_slope = slope_changes[t_i];
            }
            last_point.bias -= last_point.slope * int128(int256(t_i - last_checkpoint));
            last_point.slope += d_slope;
            if (last_point.bias < 0) {
                // This can happen
                last_point.bias = 0;
            }
            if (last_point.slope < 0) {
                // This cannot happen - just in case
                last_point.slope = 0;
            }
            last_checkpoint = t_i;
            last_point.ts = t_i;
            last_point.blk = initial_last_point_blk + (block_slope * (t_i - initial_last_point_ts)) / MULTIPLIER;

            _epoch += 1;
            if (t_i == block.timestamp) {
                last_point.blk = block.number;
                break;
            } else {
                point_history[_epoch] = last_point;
            }
        }

        epoch = _epoch;
        // Now point_history is filled until t=now

        if (_addr != address(0x0)) {
            // If last point was in this block, the slope change has been applied already
            // But in such case we have 0 slope(s)
            last_point.slope += (u_new.slope - u_old.slope);
            last_point.bias += (u_new.bias - u_old.bias);
            if (last_point.slope < 0) {
                last_point.slope = 0;
            }
            if (last_point.bias < 0) {
                last_point.bias = 0;
            }
        }

        // Record the changed point into history
        point_history[_epoch] = last_point;

        if (_addr != address(0x0)) {
            // Schedule the slope changes (slope is going down)
            // We subtract new_user_slope from [new_locked.end]
            // and add old_user_slope to [old_locked.end]
            if (old_locked.end > block.timestamp) {
                // old_dslope was <something> - u_old.slope, so we cancel that
                old_dslope += u_old.slope;
                if (new_locked.end == old_locked.end) {
                    old_dslope -= u_new.slope; // It was a new deposit, not extension
                }
                slope_changes[old_locked.end] = old_dslope;
            }

            if (new_locked.end > block.timestamp) {
                if (new_locked.end > old_locked.end) {
                    new_dslope -= u_new.slope; // old slope disappeared at this point
                    slope_changes[new_locked.end] = new_dslope;
                }
                // else: we recorded it already in old_dslope
            }
            // Now handle user history
            address addr = _addr;
            uint256 user_epoch = user_point_epoch[addr] + 1;

            user_point_epoch[addr] = user_epoch;
            u_new.ts = block.timestamp;
            u_new.blk = block.number;
            user_point_history[addr][user_epoch] = u_new;
        }
    }

    /// @notice Deposit and lock tokens for a user
    /// @param _addr User's wallet address
    /// @param _value Amount to deposit
    /// @param unlock_time New time when to unlock the tokens, or 0 if unchanged
    /// @param locked_balance Previous locked amount / timestamp
    /// @param deposit_type The type of deposit
    function _deposit_for(
        address _addr,
        uint256 _value,
        uint256 unlock_time,
        LockedBalance memory locked_balance,
        DepositType deposit_type
    )
        internal
    {
        LockedBalance memory _locked = locked_balance;
        uint256 supply_before = supply;

        supply = supply_before + _value;
        LockedBalance memory old_locked;
        (old_locked.amount, old_locked.end) = (_locked.amount, _locked.end);
        // Adding to existing lock, or if a lock is expired - creating a new one
        _locked.amount += int128(int256(_value));
        if (unlock_time != 0) {
            _locked.end = unlock_time;
        }
        locked[_addr] = _locked;

        // Possibilities:
        // Both old_locked.end could be current or expired (>/< block.timestamp)
        // value == 0 (extend lock) or value > 0 (add to lock or extend lock)
        // _locked.end > block.timestamp (always)
        _checkpoint(_addr, old_locked, _locked);

        if (_value != 0) {
            IERC20(token).safeTransferFrom(_addr, address(this), _value);
        }

        emit Deposit(_addr, _value, _locked.end, deposit_type, block.timestamp);
        emit Supply(supply_before, supply_before + _value);
    }

    /// @notice Record global data to checkpoint
    function checkpoint() external notUnlocked {
        _checkpoint(address(0x0), LockedBalance(0, 0), LockedBalance(0, 0));
    }

    /// @notice Deposit `_value` tokens for `_addr` and add to the lock
    /// @dev Anyone (even a smart contract) can deposit for someone else, but
    ///      cannot extend their locktime and deposit for a brand new user
    /// @param _addr User's wallet address
    /// @param _value Amount to add to user's lock
    function deposit_for(address _addr, uint256 _value) external nonReentrant notUnlocked {
        LockedBalance memory _locked = locked[_addr];

        require(_value > 0, "Need non-zero value"); // dev: need non-zero value
        require(_locked.amount > 0, "No existing lock found");
        require(_locked.end > block.timestamp, "Cannot add to expired lock. Withdraw");
        _deposit_for(_addr, _value, 0, _locked, DepositType.DEPOSIT_FOR_TYPE);
    }

    /// @notice Deposit `_value` tokens for `msg.sender` and lock until `_unlock_time`
    /// @param _value Amount to deposit
    /// @param _unlock_time Epoch time when tokens unlock, rounded down to whole weeks
    function _create_lock(address _acc, uint256 _value, uint256 _unlock_time) internal {
        require(_value > 0, "Need non-zero value"); // dev: need non-zero value

        LockedBalance memory _locked = locked[_acc];
        require(_locked.amount == 0, "Withdraw old tokens first");

        uint256 unlock_time = (_unlock_time / WEEK) * WEEK; // Locktime is rounded down to weeks
        require(unlock_time >= block.timestamp + MINTIME, "Voting lock must be at least MINTIME");
        require(unlock_time <= block.timestamp + MAXTIME, "Voting lock can be 2 years max");

        _deposit_for(_acc, _value, unlock_time, _locked, DepositType.CREATE_LOCK_TYPE);
    }

    /// @notice External function for _create_lock
    /// @param _value Amount to deposit
    /// @param _unlock_time Epoch time when tokens unlock, rounded down to whole weeks
    function create_lock(uint256 _value, uint256 _unlock_time) external nonReentrant onlyUserOrWhitelist notUnlocked {
        _create_lock(msg.sender, _value, _unlock_time);
    }

    function create_lock_for(
        address _acc,
        uint256 _value,
        uint256 _unlock_time
    )
        external
        nonReentrant
        onlyWhitelist
        notUnlocked
    {
        _create_lock(_acc, _value, _unlock_time);
    }

    /// @notice Deposit `_value` additional tokens for `msg.sender` without modifying the unlock time
    /// @param _value Amount of tokens to deposit and add to the lock
    function increase_amount(uint256 _value) external nonReentrant onlyUserOrWhitelist notUnlocked {
        _increase_amount(_value);
    }

    function _increase_amount(uint256 _value) internal {
        LockedBalance memory _locked = locked[msg.sender];

        require(_value > 0, "Need non-zero value"); // dev: need non-zero value
        require(_locked.amount > 0, "No existing lock found");
        require(_locked.end > block.timestamp, "Cannot add to expired lock. Withdraw");

        _deposit_for(msg.sender, _value, 0, _locked, DepositType.INCREASE_LOCK_AMOUNT);
    }

    /// @notice Extend the unlock time for `msg.sender` to `_unlock_time`
    /// @param _unlock_time New epoch time for unlocking
    function increase_unlock_time(uint256 _unlock_time) external nonReentrant onlyUserOrWhitelist notUnlocked {
        _increase_unlock_time(_unlock_time);
    }

    function _increase_unlock_time(uint256 _unlock_time) internal {
        LockedBalance memory _locked = locked[msg.sender];
        uint256 unlock_time = (_unlock_time / WEEK) * WEEK; // Locktime is rounded down to weeks

        require(_locked.end > block.timestamp, "Lock expired");
        require(_locked.amount > 0, "Nothing is locked");
        require(unlock_time > _locked.end, "Can only increase lock duration");
        require(unlock_time <= block.timestamp + MAXTIME, "Voting lock can be 2 years max");

        _deposit_for(msg.sender, 0, unlock_time, _locked, DepositType.INCREASE_UNLOCK_TIME);
    }

    /// @notice Extend the unlock time and/or for `msg.sender` to `_unlock_time`
    /// @param _unlock_time New epoch time for unlocking
    function increase_amount_and_time(
        uint256 _value,
        uint256 _unlock_time
    )
        external
        nonReentrant
        onlyUserOrWhitelist
        notUnlocked
    {
        require(_value > 0 || _unlock_time > 0, "Value and Unlock cannot both be 0");
        if (_value > 0 && _unlock_time > 0) {
            _increase_amount(_value);
            _increase_unlock_time(_unlock_time);
        } else if (_value > 0 && _unlock_time == 0) {
            _increase_amount(_value);
        } else {
            _increase_unlock_time(_unlock_time);
        }
    }

    /// @notice Withdraw all tokens for `msg.sender`
    /// @dev Only possible if the lock has expired
    function _withdraw() internal {
        LockedBalance memory _locked = locked[msg.sender];
        uint256 value = uint256(int256(_locked.amount));

        if (!unlocked) {
            require(block.timestamp >= _locked.end, "The lock didn't expire");
        }

        locked[msg.sender] = LockedBalance(0, 0);
        uint256 supply_before = supply;
        supply = supply_before - value;

        // old_locked can have either expired <= timestamp or zero end
        // _locked has only 0 end
        // Both can have >= 0 amount
        _checkpoint(msg.sender, _locked, LockedBalance(0, 0));

        IERC20(token).safeTransfer(msg.sender, value);

        emit Withdraw(msg.sender, value, block.timestamp);
        emit Supply(supply_before, supply_before - value);
    }

    function withdraw() external nonReentrant {
        _withdraw();
    }

    /// @notice Deposit `_value` tokens for `msg.sender` and lock until `_unlock_time`
    /// @param _value Amount to deposit
    /// @param _unlock_time Epoch time when tokens unlock, rounded down to whole weeks
    function withdraw_and_create_lock(
        uint256 _value,
        uint256 _unlock_time
    )
        external
        nonReentrant
        onlyUserOrWhitelist
        notUnlocked
    {
        _withdraw();
        _create_lock(msg.sender, _value, _unlock_time);
    }

    // The following ERC20/minime-compatible methods are not real balanceOf and supply!
    // They measure the weights for the purpose of voting, so they don't represent
    // real coins.

    /// @notice Binary search to estimate timestamp for block number
    /// @param _block Block to find
    /// @param max_epoch Don't go beyond this epoch
    /// @return Approximate timestamp for block
    function _find_block_epoch(uint256 _block, uint256 max_epoch) internal view returns (uint256) {
        // Binary search
        uint256 _min = 0;
        uint256 _max = max_epoch;
        for (uint256 i = 0; i < 128; ++i) {
            // Will be always enough for 128-bit numbers
            if (_min >= _max) {
                break;
            }
            uint256 _mid = (_min + _max + 1) / 2;
            if (point_history[_mid].blk <= _block) {
                _min = _mid;
            } else {
                _max = _mid - 1;
            }
        }
        return _min;
    }

    /// @notice Get the current voting power for `msg.sender`
    /// @dev Adheres to the ERC20 `balanceOf` interface for Aragon compatibility
    /// @param addr User wallet address
    /// @param _t Epoch time to return voting power at
    /// @return User voting power
    function _balanceOf(address addr, uint256 _t) internal view returns (uint256) {
        uint256 _epoch = user_point_epoch[addr];
        if (_epoch == 0) {
            return 0;
        } else {
            Point memory last_point = user_point_history[addr][_epoch];
            last_point.bias -= last_point.slope * int128(int256(_t) - int256(last_point.ts));
            if (last_point.bias < 0) {
                last_point.bias = 0;
            }
            return uint256(int256(last_point.bias));
        }
    }

    function balanceOfAtT(address addr, uint256 _t) external view returns (uint256) {
        return _balanceOf(addr, _t);
    }

    function balanceOf(address addr) external view returns (uint256) {
        return _balanceOf(addr, block.timestamp);
    }

    /// @notice Measure voting power of `addr` at block height `_block`
    /// @dev Adheres to MiniMe `balanceOfAt` interface: https://github.com/Giveth/minime
    /// @param addr User's wallet address
    /// @param _block Block to calculate the voting power at
    /// @return Voting power
    function balanceOfAt(address addr, uint256 _block) external view returns (uint256) {
        // Copying and pasting totalSupply code because Vyper cannot pass by
        // reference yet
        require(_block <= block.number);

        // Binary search
        uint256 _min = 0;
        uint256 _max = user_point_epoch[addr];
        for (uint256 i = 0; i < 128; ++i) {
            // Will be always enough for 128-bit numbers
            if (_min >= _max) {
                break;
            }
            uint256 _mid = (_min + _max + 1) / 2;
            if (user_point_history[addr][_mid].blk <= _block) {
                _min = _mid;
            } else {
                _max = _mid - 1;
            }
        }

        Point memory upoint = user_point_history[addr][_min];

        uint256 max_epoch = epoch;
        uint256 _epoch = _find_block_epoch(_block, max_epoch);
        Point memory point_0 = point_history[_epoch];
        uint256 d_block = 0;
        uint256 d_t = 0;
        if (_epoch < max_epoch) {
            Point memory point_1 = point_history[_epoch + 1];
            d_block = point_1.blk - point_0.blk;
            d_t = point_1.ts - point_0.ts;
        } else {
            d_block = block.number - point_0.blk;
            d_t = block.timestamp - point_0.ts;
        }
        uint256 block_time = point_0.ts;
        if (d_block != 0) {
            block_time += (d_t * (_block - point_0.blk)) / d_block;
        }

        upoint.bias -= upoint.slope * int128(int256(block_time - upoint.ts));
        if (upoint.bias >= 0) {
            return uint256(uint128(upoint.bias));
        } else {
            return 0;
        }
    }

    /// @notice Calculate total voting power at some point in the past
    /// @param point The point (bias/slope) to start search from
    /// @param t Time to calculate the total voting power at
    /// @return Total voting power at that time
    function _supply_at(Point memory point, uint256 t) internal view returns (uint256) {
        Point memory last_point = point;
        uint256 t_i = (last_point.ts / WEEK) * WEEK;
        for (uint256 i = 0; i < 255; ++i) {
            t_i += WEEK;
            int128 d_slope = 0;
            if (t_i > t) {
                t_i = t;
            } else {
                d_slope = slope_changes[t_i];
            }
            last_point.bias -= last_point.slope * int128(int256(t_i - last_point.ts));
            if (t_i == t) {
                break;
            }
            last_point.slope += d_slope;
            last_point.ts = t_i;
        }

        if (last_point.bias < 0) {
            last_point.bias = 0;
        }
        return uint256(uint128(last_point.bias));
    }

    /// @notice Calculate total voting power
    /// @dev Adheres to the ERC20 `totalSupply` interface for Aragon compatibility
    /// @return Total voting power
    function _totalSupply(uint256 t) internal view returns (uint256) {
        uint256 _epoch = epoch;
        Point memory last_point = point_history[_epoch];
        return _supply_at(last_point, t);
    }

    function totalSupplyAtT(uint256 t) external view returns (uint256) {
        return _totalSupply(t);
    }

    function totalSupply() external view returns (uint256) {
        return _totalSupply(block.timestamp);
    }

    /// @notice Calculate total voting power at some point in the past
    /// @param _block Block to calculate the total voting power at
    /// @return Total voting power at `_block`
    function totalSupplyAt(uint256 _block) external view returns (uint256) {
        require(_block <= block.number);
        uint256 _epoch = epoch;
        uint256 target_epoch = _find_block_epoch(_block, _epoch);

        Point memory point = point_history[target_epoch];
        uint256 dt = 0;
        if (target_epoch < _epoch) {
            Point memory point_next = point_history[target_epoch + 1];
            if (point.blk != point_next.blk) {
                dt = ((_block - point.blk) * (point_next.ts - point.ts)) / (point_next.blk - point.blk);
            }
        } else {
            if (point.blk != block.number) {
                dt = ((_block - point.blk) * (block.timestamp - point.ts)) / (block.number - point.blk);
            }
        }
        // Now dt contains info on how far are we beyond point
        return _supply_at(point, point.ts + dt);
    }

    // Dummy methods for compatibility with Aragon
    function changeController(address _newController) external {
        require(msg.sender == controller);
        controller = _newController;
    }
}

// File: contracts/interfaces/IVotingEscrow.sol



// SPDX-License-Identifier: GPL-3.0-or-later

pragma solidity >=0.7.0 <0.9.0;
pragma experimental ABIEncoderV2;

// For compatibility, we're keeping the same function names as in the original Curve code, including the mixed-case
// naming convention.
// solhint-disable func-name-mixedcase

interface IVotingEscrow {
    struct Point {
        int128 bias;
        int128 slope; // - dweight / dt
        uint256 ts;
        uint256 blk; // block
    }

    struct LockedBalance {
        int128 amount;
        uint256 end;
    }

    function MAXTIME() external view returns (uint256);

    function MINTIME() external view returns (uint256);

    function token() external view returns (address);

    function supply() external view returns (uint256);

    function unlocked() external view returns (bool);

    function locked(address) external view returns (int128, uint256);

    function epoch() external view returns (uint256);

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

    function balanceOfAt(address user, uint256 _block) external view returns (uint256);

    function balanceOfAtT(address user, uint256 timestamp) external view returns (uint256);

    function totalSupply() external view returns (uint256);

    function totalSupplyAt(uint256 _block) external view returns (uint256);

    function totalSupplyAtT(uint256 timestamp) external view returns (uint256);

    function user_point_epoch(address user) external view returns (uint256);

    function slope_changes(uint256 i) external view returns (int128);

    function point_history(uint256 timestamp) external view returns (int128, int128, uint256, uint256);

    function user_point_history(
        address user,
        uint256 timestamp
    )
        external
        view
        returns (int128, int128, uint256, uint256);

    function unlock() external;

    function checkpoint() external;

    function locked__end(address user) external view returns (uint256);

    function deposit_for(address _addr, uint256 _value) external;

    function create_lock(uint256 _value, uint256 _unlock_time) external;

    function create_lock_for(address _addr, uint256 _value, uint256 _unlock_time) external;

    function increase_amount(uint256 _value) external;

    function withdraw() external;

    function add_to_whitelist(address _addr) external;

    function remove_from_whitelist(address _addr) external;
}

// File: lib/openzeppelin-contracts/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/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() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(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");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: lib/openzeppelin-contracts/contracts/access/Ownable2Step.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (access/Ownable2Step.sol)

pragma solidity ^0.8.0;

import "./Ownable.sol";

/**
 * @dev Contract module which provides 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} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

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

    /**
     * @dev Returns the address of the pending owner.
     */
    function pendingOwner() public view virtual returns (address) {
        return _pendingOwner;
    }

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual override onlyOwner {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() public virtual {
        address sender = _msgSender();
        require(pendingOwner() == sender, "Ownable2Step: caller is not the new owner");
        _transferOwnership(sender);
    }
}

// File: lib/openzeppelin-contracts/contracts/interfaces/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC20.sol)

pragma solidity ^0.8.0;

import "../token/ERC20/IERC20.sol";

// File: lib/openzeppelin-contracts/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == _ENTERED;
    }
}

// File: lib/openzeppelin-contracts/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

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

// File: lib/openzeppelin-contracts/contracts/token/ERC20/extensions/IERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/extensions/IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

// File: lib/openzeppelin-contracts/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.3) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/IERC20Permit.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    /**
     * @dev Transfer `value` amount of `token` from the calling contract to `to`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    /**
     * @dev Transfer `value` amount of `token` from `from` to `to`, spending the approval given by `from` to the
     * calling contract. If `token` returns no value, non-reverting calls are assumed to be successful.
     */
    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'
        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));
    }

    /**
     * @dev Increase the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 oldAllowance = token.allowance(address(this), spender);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, oldAllowance + value));
    }

    /**
     * @dev Decrease the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, oldAllowance - value));
        }
    }

    /**
     * @dev Set the calling contract's allowance toward `spender` to `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful. Meant to be used with tokens that require the approval
     * to be set to zero before setting it to a non-zero value, such as USDT.
     */
    function forceApprove(IERC20 token, address spender, uint256 value) internal {
        bytes memory approvalCall = abi.encodeWithSelector(token.approve.selector, spender, value);

        if (!_callOptionalReturnBool(token, approvalCall)) {
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, 0));
            _callOptionalReturn(token, approvalCall);
        }
    }

    /**
     * @dev Use a ERC-2612 signature to set the `owner` approval toward `spender` on `token`.
     * Revert on invalid signature.
     */
    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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");
        require(returndata.length == 0 || abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
    }

    /**
     * @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).
     *
     * This is a variant of {_callOptionalReturn} that silents catches all reverts and returns a bool instead.
     */
    function _callOptionalReturnBool(IERC20 token, bytes memory data) private returns (bool) {
        // 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 cannot use {Address-functionCall} here since this should return false
        // and not revert is the subcall reverts.

        (bool success, bytes memory returndata) = address(token).call(data);
        return
            success && (returndata.length == 0 || abi.decode(returndata, (bool))) && Address.isContract(address(token));
    }
}

// File: lib/openzeppelin-contracts/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     *
     * Furthermore, `isContract` will also return true if the target contract within
     * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
     * which only has an effect at the end of a transaction.
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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://consensys.net/diligence/blog/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/v0.8.0/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");

        (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 functionCallWithValue(target, data, 0, "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");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // 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
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

// File: lib/openzeppelin-contracts/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^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 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) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}