// File: contracts/sVotingEscrow.sol



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

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

/**
@title Voting Escrow
@author Curve Finance
@license MIT
@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` (3 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 (3 years?)
*/
struct Point {
    int128 bias;
    int128 slope; // # -dweight / dt
    uint ts;
    uint blk; // block
}

struct LockedBalance {
    int128 amount;
    uint end;
}

contract sVotingEscrow is Ownable, ReentrancyGuard {
    enum DepositType {
        DEPOSIT_FOR_TYPE,
        CREATE_LOCK_TYPE,
        INCREASE_LOCK_AMOUNT,
        INCREASE_UNLOCK_TIME
    }

    event Deposit(address indexed provider, uint value, uint indexed locktime, DepositType deposit_type, uint ts);
    event Withdraw(address indexed provider, uint value, uint ts);

    uint internal constant WEEK = 1 weeks;
    uint public constant MAXTIME = 3 * 365 * 86400;
    int128 internal constant iMAXTIME = 3 * 365 * 86400;
    uint internal constant MULTIPLIER = 1 ether;

    mapping(address => LockedBalance) public locked;

    uint public epoch;
    mapping(uint => Point) public point_history; // epoch -> unsigned point
    mapping(address => Point[1000000000]) public user_point_history; // user -> Point[user_epoch]
    mapping(address => uint) public user_point_epoch;
    mapping(uint => int128) public slope_changes; // time -> signed slope change

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

    /// @notice Contract constructor
    constructor() {
        point_history[0].blk = block.number;
        point_history[0].ts = block.timestamp;
    }

    /// @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) {
        uint 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, uint _idx) external view returns (uint) {
        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 (uint) {
        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;
        uint _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(int(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(int(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];
        }
        uint 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

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

        uint 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
        uint t_i = (last_checkpoint / WEEK) * WEEK;
        for (uint 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(int(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;
            uint 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, uint _value, uint unlock_time, LockedBalance memory locked_balance, DepositType deposit_type) internal {
        LockedBalance memory _locked = locked_balance;

        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(int(_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);

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

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

    /// @notice Deposit `_value` tokens for `_addr` and lock until `_unlock_time`
    /// @param _addr Create lock for address
    /// @param _value Amount to deposit
    /// @param _unlock_time Epoch time when tokens unlock, rounded down to whole weeks
    function create_lock_for(address _addr, uint _value, uint _unlock_time) external nonReentrant onlyOwner {
        require(_value > 0); // dev: need non-zero value

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

        uint unlock_time = (_unlock_time / WEEK) * WEEK; // Locktime is rounded down to weeks
        require(unlock_time > block.timestamp, "Can only lock until time in the future");
        require(unlock_time <= block.timestamp + MAXTIME, "Voting lock can be 3 years max");

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

    /// @notice Deposit `_value` additional tokens for `_addr` without modifying the unlock time
    /// @param _addr Increase amount for address
    /// @param _value Amount of tokens to deposit and add to the lock
    function increase_amount_for(address _addr, uint _value) external nonReentrant onlyOwner {
        LockedBalance memory _locked = locked[_addr];

        require(_value > 0); // 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.INCREASE_LOCK_AMOUNT);
    }

    /// @notice Extend the unlock time for `_addr` to `_unlock_time`
    /// @param _addr Increase unlock time for address
    /// @param _unlock_time New epoch time for unlocking
    function increase_unlock_time_for(address _addr, uint _unlock_time) external nonReentrant onlyOwner {
        LockedBalance memory _locked = locked[_addr];
        uint 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 3 years max");

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

    /// @notice Withdraw all tokens for `_addr`
    /// @dev Only possible if the lock has expired
    /// @param _addr Withdraw for address
    function withdraw_for(address _addr) external nonReentrant onlyOwner {
        LockedBalance memory _locked = locked[_addr];
        uint value = uint(int(_locked.amount));

        locked[_addr] = LockedBalance(0, 0);

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

        emit Withdraw(_addr, value, block.timestamp);
    }

    // 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(uint _block, uint max_epoch) internal view returns (uint) {
        // Binary search
        uint _min = 0;
        uint _max = max_epoch;
        for (uint i = 0; i < 128; ++i) {
            // Will be always enough for 128-bit numbers
            if (_min >= _max) {
                break;
            }
            uint _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 `_addr`
    /// @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, uint _t) internal view returns (uint) {
        uint _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(int(_t) - int(last_point.ts));
            if (last_point.bias < 0) {
                last_point.bias = 0;
            }
            return uint(int(last_point.bias));
        }
    }

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

    function balanceOf(address addr) external view returns (uint) {
        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, uint _block) external view returns (uint) {
        // Copying and pasting totalSupply code because Vyper cannot pass by
        // reference yet
        require(_block <= block.number);

        // Binary search
        uint _min = 0;
        uint _max = user_point_epoch[addr];
        for (uint i = 0; i < 128; ++i) {
            // Will be always enough for 128-bit numbers
            if (_min >= _max) {
                break;
            }
            uint _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];

        uint max_epoch = epoch;
        uint _epoch = _find_block_epoch(_block, max_epoch);
        Point memory point_0 = point_history[_epoch];
        uint d_block = 0;
        uint 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;
        }
        uint block_time = point_0.ts;
        if (d_block != 0) {
            block_time += (d_t * (_block - point_0.blk)) / d_block;
        }

        upoint.bias -= upoint.slope * int128(int(block_time - upoint.ts));
        if (upoint.bias >= 0) {
            return uint(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, uint t) internal view returns (uint) {
        Point memory last_point = point;
        uint t_i = (last_point.ts / WEEK) * WEEK;
        for (uint 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(int(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 uint(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(uint t) internal view returns (uint) {
        uint _epoch = epoch;
        Point memory last_point = point_history[_epoch];
        return _supply_at(last_point, t);
    }

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

    function totalSupply() external view returns (uint) {
        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(uint _block) external view returns (uint) {
        require(_block <= block.number);
        uint _epoch = epoch;
        uint target_epoch = _find_block_epoch(_block, _epoch);

        Point memory point = point_history[target_epoch];
        uint 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);
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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 Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _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: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

        _;

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

// File: @openzeppelin/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;
    }
}