Contract Source Code:

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

import "./ERC20Permit.sol";
import "./lib/IOwnable.sol";
import "./OwnableManagement.sol";

contract veSYNC is ERC20Permit, OwnableManagement {
    using SafeMath for uint256;

    modifier onlyStakingContract() {
        require(msg.sender == stakingContract);
        _;
    }

    address public stakingContract;
    address public initializer;

    event LogSupply(
        uint256 indexed epoch,
        uint256 timestamp,
        uint256 totalSupply
    );
    event LogRebase(uint256 indexed epoch, uint256 rebase, uint256 index);
    event LogStakingContractUpdated(address stakingContract);

    struct Rebase {
        uint epoch;
        uint rebase; // 18 decimals
        uint totalStakedBefore;
        uint totalStakedAfter;
        uint amountRebased;
        uint index;
        uint32 timeOccured;
    }
    Rebase[] public rebases;

    uint public INDEX;

    uint256 private constant MAX_UINT256 = ~uint256(0);
    uint256 private constant INITIAL_FRAGMENTS_SUPPLY =
        5_000_000_000_000 * 10 ** 9;

    // TOTAL_GONS is a multiple of INITIAL_FRAGMENTS_SUPPLY so that _gonsPerFragment is an integer.
    // Use the highest value that fits in a uint256 for max granularity.
    uint256 private constant TOTAL_GONS =
        MAX_UINT256 - (MAX_UINT256 % INITIAL_FRAGMENTS_SUPPLY);

    // MAX_SUPPLY = maximum integer < (sqrt(4*TOTAL_GONS + 1) - 1) / 2
    uint256 private constant MAX_SUPPLY = ~uint128(0); // (2^128) - 1

    uint256 private _gonsPerFragment;
    mapping(address => uint256) private _gonBalances;

    mapping(address => mapping(address => uint256)) private _allowedValue;

    constructor() ERC20("Vote-escrowed SYNC", "veSYNC", 9) ERC20Permit() {
        initializer = msg.sender;
        _totalSupply = INITIAL_FRAGMENTS_SUPPLY;
        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);
    }

    function initialize(address stakingContract_) external returns (bool) {
        require(msg.sender == initializer);
        require(stakingContract_ != address(0));
        stakingContract = stakingContract_;
        _gonBalances[stakingContract] = TOTAL_GONS;

        emit Transfer(address(0x0), stakingContract, _totalSupply);
        emit LogStakingContractUpdated(stakingContract_);

        initializer = address(0);
        return true;
    }

    function setIndex(uint _INDEX) external onlyManager returns (bool) {
        require(INDEX == 0);
        INDEX = gonsForBalance(_INDEX);
        return true;
    }

    /**
        @notice increases veSYNC supply to increase staking balances relative to profit_
        @param profit_ uint256
        @return uint256
     */
    function rebase(
        uint256 profit_,
        uint epoch_
    ) public onlyStakingContract returns (uint256) {
        uint256 rebaseAmount;
        uint256 circulatingSupply_ = circulatingSupply();

        if (profit_ == 0) {
            emit LogSupply(epoch_, block.timestamp, _totalSupply);
            emit LogRebase(epoch_, 0, index());
            return _totalSupply;
        } else if (circulatingSupply_ > 0) {
            rebaseAmount = profit_.mul(_totalSupply).div(circulatingSupply_);
        } else {
            rebaseAmount = profit_;
        }

        _totalSupply = _totalSupply.add(rebaseAmount);

        if (_totalSupply > MAX_SUPPLY) {
            _totalSupply = MAX_SUPPLY;
        }

        _gonsPerFragment = TOTAL_GONS.div(_totalSupply);

        _storeRebase(circulatingSupply_, profit_, epoch_);

        return _totalSupply;
    }

    /**
        @notice emits event with data about rebase
        @param previousCirculating_ uint
        @param profit_ uint
        @param epoch_ uint
        @return bool
     */
    function _storeRebase(
        uint previousCirculating_,
        uint profit_,
        uint epoch_
    ) internal returns (bool) {
        uint rebasePercent = profit_.mul(1e18).div(previousCirculating_);

        rebases.push(
            Rebase({
                epoch: epoch_,
                rebase: rebasePercent, // 18 decimals
                totalStakedBefore: previousCirculating_,
                totalStakedAfter: circulatingSupply(),
                amountRebased: profit_,
                index: index(),
                timeOccured: uint32(block.timestamp)
            })
        );

        emit LogSupply(epoch_, block.timestamp, _totalSupply);
        emit LogRebase(epoch_, rebasePercent, index());

        return true;
    }

    function balanceOf(address who) public view override returns (uint256) {
        return _gonBalances[who].div(_gonsPerFragment);
    }

    function gonsForBalance(uint amount) public view returns (uint) {
        return amount.mul(_gonsPerFragment);
    }

    function balanceForGons(uint gons) public view returns (uint) {
        return gons.div(_gonsPerFragment);
    }

    // Staking contract holds excess veSYNC
    function circulatingSupply() public view returns (uint) {
        return _totalSupply.sub(balanceOf(stakingContract));
    }

    function index() public view returns (uint) {
        return balanceForGons(INDEX);
    }

    function transfer(
        address to,
        uint256 value
    ) public override returns (bool) {
        uint256 gonValue = value.mul(_gonsPerFragment);
        _gonBalances[msg.sender] = _gonBalances[msg.sender].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(msg.sender, to, value);
        return true;
    }

    function allowance(
        address owner_,
        address spender
    ) public view override returns (uint256) {
        return _allowedValue[owner_][spender];
    }

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) public override returns (bool) {
        _allowedValue[from][msg.sender] = _allowedValue[from][msg.sender].sub(
            value
        );
        emit Approval(from, msg.sender, _allowedValue[from][msg.sender]);

        uint256 gonValue = gonsForBalance(value);
        _gonBalances[from] = _gonBalances[from].sub(gonValue);
        _gonBalances[to] = _gonBalances[to].add(gonValue);
        emit Transfer(from, to, value);

        return true;
    }

    function approve(
        address spender,
        uint256 value
    ) public override returns (bool) {
        _allowedValue[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    // What gets called in a permit
    function _approve(
        address owner,
        address spender,
        uint256 value
    ) internal virtual override {
        _allowedValue[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    function increaseAllowance(
        address spender,
        uint256 addedValue
    ) public override returns (bool) {
        _allowedValue[msg.sender][spender] = _allowedValue[msg.sender][spender]
            .add(addedValue);
        emit Approval(msg.sender, spender, _allowedValue[msg.sender][spender]);
        return true;
    }

    function decreaseAllowance(
        address spender,
        uint256 subtractedValue
    ) public override returns (bool) {
        uint256 oldValue = _allowedValue[msg.sender][spender];
        if (subtractedValue >= oldValue) {
            _allowedValue[msg.sender][spender] = 0;
        } else {
            _allowedValue[msg.sender][spender] = oldValue.sub(subtractedValue);
        }
        emit Approval(msg.sender, spender, _allowedValue[msg.sender][spender]);
        return true;
    }
}

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

import "./lib/IERC20.sol";
import "./lib/IERC2612Permit.sol";
import "./lib/Counters.sol";
import "./ERC20.sol";

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)
            )
        );
    }

    /**
     * @dev See {IERC2612Permit-permit}.
     *
     */
    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,
            "ZeroSwapPermit: Invalid signature"
        );

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

    /**
     * @dev See {IERC2612Permit-nonces}.
     */
    function nonces(address owner) public view override returns (uint256) {
        return _nonces[owner].current();
    }
}

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

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

    function renounceOwnership() external;

    function transferOwnership(address newOwner_) external;
}

// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;
import "./lib/IOwnableManagement.sol";

contract OwnableManagement is IOwnableManagement {
      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 manager() public view override returns (address) {
        return _owner;
    }

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

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

    function pushManagement( address newOwner_ ) public virtual override onlyManager() {
        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;
    }
}

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

interface IERC20 {
    function decimals() external view returns (uint8);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

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

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

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

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

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

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

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

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);
}

// 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);
    }
}

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

import "./lib/IERC20.sol";
import "./lib/SafeMath.sol";

abstract contract ERC20 is IERC20 {
    using SafeMath for uint256;

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

    // Present in ERC777
    mapping(address => uint256) internal _balances;

    // Present in ERC777
    mapping(address => mapping(address => uint256)) internal _allowances;

    // Present in ERC777
    uint256 internal _totalSupply;

    // Present in ERC777
    string internal _name;

    // Present in ERC777
    string internal _symbol;

    // Present in ERC777
    uint8 internal _decimals;

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

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

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

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

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

    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 {}
}

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

interface IOwnableManagement {
    function manager() external view returns (address);

    function renounceManagement() external;

    function pushManagement(address newOwner_) external;

    function pullManagement() external;
}

// 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 add32(uint32 a, uint32 b) internal pure returns (uint32) {
        uint32 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 sub32(uint32 a, uint32 b) internal pure returns (uint32) {
        return sub32(a, b, "SafeMath: subtraction overflow");
    }

    function sub32(
        uint32 a,
        uint32 b,
        string memory errorMessage
    ) internal pure returns (uint32) {
        require(b <= a, errorMessage);
        uint32 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 mul32(uint32 a, uint32 b) internal pure returns (uint32) {
        if (a == 0) {
            return 0;
        }

        uint32 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 mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }

    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;
        }
    }

    function percentageAmount(
        uint256 total_,
        uint8 percentage_
    ) internal pure returns (uint256 percentAmount_) {
        return div(mul(total_, percentage_), 1000);
    }

    function substractPercentage(
        uint256 total_,
        uint8 percentageToSub_
    ) internal pure returns (uint256 result_) {
        return sub(total_, div(mul(total_, percentageToSub_), 1000));
    }

    function percentageOfTotal(
        uint256 part_,
        uint256 total_
    ) internal pure returns (uint256 percent_) {
        return div(mul(part_, 100), total_);
    }

    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + (((a % 2) + (b % 2)) / 2);
    }

    function quadraticPricing(
        uint256 payment_,
        uint256 multiplier_
    ) internal pure returns (uint256) {
        return sqrrt(mul(multiplier_, payment_));
    }

    function bondingCurve(
        uint256 supply_,
        uint256 multiplier_
    ) internal pure returns (uint256) {
        return mul(multiplier_, supply_);
    }
}