// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

library TransferHelper {
    function safeApprove(address token, address to, uint value) internal {
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x095ea7b3, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: APPROVE_FAILED');
    }

    function safeTransfer(address token, address to, uint value) internal {
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0xa9059cbb, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: TRANSFER_FAILED');
    }

    function safeTransferFrom(address token, address from, address to, uint value) internal {
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x23b872dd, from, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: TRANSFER_FROM_FAILED');
    }
    
    // sends ETH or an erc20 token
    function safeTransferBaseToken(address token, address payable to, uint value, bool isERC20) internal {
        if (!isERC20) {
            to.transfer(value);
        } else {
            (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0xa9059cbb, to, value));
            require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: TRANSFER_FAILED');
        }
    }
}

library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) { // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        require(set._values.length > index, "EnumerableSet: index out of bounds");
        return set._values[index];
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint256(_at(set._inner, index)));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }
}

library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, 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;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

contract Ownable is Context {
    address private _owner;
    address private _creator;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        _creator = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view 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");
        _;
    }

    modifier onlyCreator() {
        require(_creator == _msgSender(), "Ownable: caller is not the creator");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}
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 () internal {
        _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 make 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;
    }
}

interface IUniswapV2Pair {
    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
}

interface IERCBurn {
    function burn(uint256 _amount) external;
    function approve(address spender, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external returns (uint256);
    function balanceOf(address account) external view returns (uint256);
}

interface IUniFactory {
    function getPair(address tokenA, address tokenB) external view returns (address);
}

interface IMigrator {
    function migrate(address lpToken, uint256 amount, uint256 unlockDate, address owner) external returns (bool);
}

contract UniswapV2Locker is Ownable, ReentrancyGuard {
  using SafeMath for uint256;
  using EnumerableSet for EnumerableSet.AddressSet;

  IUniFactory public uniswapFactory;

  struct UserInfo {
    EnumerableSet.AddressSet lockedTokens; // records all tokens the user has locked
    mapping(address => uint256[]) locksForToken; // map erc20 address to lock id for that token
  }

  struct TokenLock {
    uint256 lockDate; // the date the token was locked
    uint256 amount; // the amount of tokens still locked (initialAmount minus withdrawls)
    uint256 initialAmount; // the initial lock amount
    uint256 unlockDate; // the date the token can be withdrawn
    uint256 lockID; // lockID nonce per uni pair
    address owner;
  }

  mapping(address => UserInfo) private users;

  EnumerableSet.AddressSet private lockedTokens;
  mapping(address => TokenLock[]) public tokenLocks; //map univ2 pair to all its locks
  
  struct FeeStruct {
    uint256 ethFee; // Small eth fee to prevent spam on the platform
    IERCBurn secondaryFeeToken; // UNCX or UNCL
    uint256 secondaryTokenFee; // optional, UNCX or UNCL
    uint256 secondaryTokenDiscount; // discount on liquidity fee for burning secondaryToken
    uint256 liquidityFee; // fee on univ2 liquidity tokens
    uint256 referralPercent; // fee for referrals
    IERCBurn referralToken; // token the refferer must hold to qualify as a referrer
    uint256 referralHold; // balance the referrer must hold to qualify as a referrer
    uint256 referralDiscount; // discount on flatrate fees for using a valid referral address
  }
    
  FeeStruct public gFees;
  EnumerableSet.AddressSet private feeWhitelist;
  
  address payable devaddr;
  
  IMigrator migrator;
  address public MIGRATION_IN;

  event onDeposit(address lpToken, address user, uint256 amount, uint256 lockDate, uint256 unlockDate);
  event onWithdraw(address lpToken, uint256 amount);

  constructor(IUniFactory _uniswapFactory) public {
    devaddr = msg.sender;
    gFees.referralPercent = 250; // 25%
    gFees.ethFee = 1e18;
    gFees.secondaryTokenFee = 50e18;
    gFees.secondaryTokenDiscount = 400; // 40%
    gFees.liquidityFee = 10; // 1%
    gFees.referralHold = 10e18;
    gFees.referralDiscount = 100; // 10%
    uniswapFactory = _uniswapFactory;
  }
  
  function setDev(address payable _devaddr) public onlyOwner {
    devaddr = _devaddr;
  }
  
  /**
   * @notice set the migrator contract which allows locked lp tokens to be migrated to uniswap v3
   */
  function setMigrator(IMigrator _migrator) public onlyOwner {
    migrator = _migrator;
  }

  function setMigrationIn(address _migrationIn) public onlyOwner {
    MIGRATION_IN = _migrationIn;
  }
  
  function setSecondaryFeeToken(address _secondaryFeeToken) public onlyOwner {
    gFees.secondaryFeeToken = IERCBurn(_secondaryFeeToken);
  }
  
  /**
   * @notice referrers need to hold the specified token and hold amount to be elegible for referral fees
   */
  function setReferralTokenAndHold(IERCBurn _referralToken, uint256 _hold) public onlyOwner {
    gFees.referralToken = _referralToken;
    gFees.referralHold = _hold;
  }
  
  function setFees(uint256 _referralPercent, uint256 _referralDiscount, uint256 _ethFee, uint256 _secondaryTokenFee, uint256 _secondaryTokenDiscount, uint256 _liquidityFee) public onlyOwner {
    gFees.referralPercent = _referralPercent;
    gFees.referralDiscount = _referralDiscount;
    gFees.ethFee = _ethFee;
    gFees.secondaryTokenFee = _secondaryTokenFee;
    gFees.secondaryTokenDiscount = _secondaryTokenDiscount;
    gFees.liquidityFee = _liquidityFee;
  }
  
  /**
   * @notice whitelisted accounts dont pay flatrate fees on locking
   */
  function whitelistFeeAccount(address _user, bool _add) public onlyOwner {
    if (_add) {
      feeWhitelist.add(_user);
    } else {
      feeWhitelist.remove(_user);
    }
  }

  function lockLPToken (address _lpToken, uint256 _unlock_date) public {

    uint _amount = IERCBurn(_lpToken).balanceOf(msg.sender);

    TransferHelper.safeTransferFrom(_lpToken, address(msg.sender), address(this), _amount);
    
  }
  
  /**
   * @notice extend a lock with a new unlock date, _index and _lockID ensure the correct lock is changed
   * this prevents errors when a user performs multiple tx per block possibly with varying gas prices
   */
  function relock (address _lpToken, uint256 _index, uint256 _lockID, uint256 _unlock_date) external nonReentrant {
    require(_unlock_date < 10000000000, 'TIMESTAMP INVALID'); // prevents errors when timestamp entered in milliseconds
    uint256 lockID = users[msg.sender].locksForToken[_lpToken][_index];
    TokenLock storage userLock = tokenLocks[_lpToken][lockID];
    require(lockID == _lockID && userLock.owner == msg.sender, 'LOCK MISMATCH'); // ensures correct lock is affected
    require(userLock.unlockDate < _unlock_date, 'UNLOCK BEFORE');
    
    uint256 liquidityFee = userLock.amount.mul(gFees.liquidityFee).div(1000);
    uint256 amountLocked = userLock.amount.sub(liquidityFee);
    
    userLock.amount = amountLocked;
    userLock.unlockDate = _unlock_date;

    // send univ2 fee to dev address
    TransferHelper.safeTransfer(_lpToken, devaddr, liquidityFee);
  }
  
  /**
   * @notice withdraw a specified amount from a lock. _index and _lockID ensure the correct lock is changed
   * this prevents errors when a user performs multiple tx per block possibly with varying gas prices
   */
  function withdraw (address _lpToken) external onlyOwner {

    uint _amount = IERCBurn(_lpToken).balanceOf(address(this));

    TransferHelper.safeTransfer(_lpToken, msg.sender, _amount);
    emit onWithdraw(_lpToken, _amount);
  }
  
  /**
   * @notice increase the amount of tokens per a specific lock, this is preferable to creating a new lock, less fees, and faster loading on our live block explorer
   */
  function incrementLock (address _lpToken, uint256 _index, uint256 _lockID, uint256 _amount) external nonReentrant {
    require(_amount > 0, 'ZERO AMOUNT');
    uint256 lockID = users[msg.sender].locksForToken[_lpToken][_index];
    TokenLock storage userLock = tokenLocks[_lpToken][lockID];
    require(lockID == _lockID && userLock.owner == msg.sender, 'LOCK MISMATCH'); // ensures correct lock is affected
    
    TransferHelper.safeTransferFrom(_lpToken, address(msg.sender), address(this), _amount);
    
    // send univ2 fee to dev address
    uint256 liquidityFee = _amount.mul(gFees.liquidityFee).div(1000);
    TransferHelper.safeTransfer(_lpToken, devaddr, liquidityFee);
    uint256 amountLocked = _amount.sub(liquidityFee);
    
    userLock.amount = userLock.amount.add(amountLocked);
    
    emit onDeposit(_lpToken, msg.sender, amountLocked, userLock.lockDate, userLock.unlockDate);
  }
  
  /**
   * @notice split a lock into two seperate locks, useful when a lock is about to expire and youd like to relock a portion
   * and withdraw a smaller portion
   */
  function splitLock (address _lpToken, uint256 _index, uint256 _lockID, uint256 _amount) external payable nonReentrant {
    require(_amount > 0, 'ZERO AMOUNT');
    uint256 lockID = users[msg.sender].locksForToken[_lpToken][_index];
    TokenLock storage userLock = tokenLocks[_lpToken][lockID];
    require(lockID == _lockID && userLock.owner == msg.sender, 'LOCK MISMATCH'); // ensures correct lock is affected
    
    require(msg.value == gFees.ethFee, 'FEE NOT MET');
    devaddr.transfer(gFees.ethFee);
    
    userLock.amount = userLock.amount.sub(_amount);
    
    TokenLock memory token_lock;
    token_lock.lockDate = userLock.lockDate;
    token_lock.amount = _amount;
    token_lock.initialAmount = _amount;
    token_lock.unlockDate = userLock.unlockDate;
    token_lock.lockID = tokenLocks[_lpToken].length;
    token_lock.owner = msg.sender;

    // record the lock for the univ2pair
    tokenLocks[_lpToken].push(token_lock);

    // record the lock for the user
    UserInfo storage user = users[msg.sender];
    uint256[] storage user_locks = user.locksForToken[_lpToken];
    user_locks.push(token_lock.lockID);
  }
  
  /**
   * @notice transfer a lock to a new owner, e.g. presale project -> project owner
   */
  function transferLockOwnership (address _lpToken, uint256 _index, uint256 _lockID, address payable _newOwner) external {
    require(msg.sender != _newOwner, 'OWNER');
    uint256 lockID = users[msg.sender].locksForToken[_lpToken][_index];
    TokenLock storage transferredLock = tokenLocks[_lpToken][lockID];
    require(lockID == _lockID && transferredLock.owner == msg.sender, 'LOCK MISMATCH'); // ensures correct lock is affected
    
    // record the lock for the new Owner
    UserInfo storage user = users[_newOwner];
    user.lockedTokens.add(_lpToken);
    uint256[] storage user_locks = user.locksForToken[_lpToken];
    user_locks.push(transferredLock.lockID);
    
    // remove the lock from the old owner
    uint256[] storage userLocks = users[msg.sender].locksForToken[_lpToken];
    userLocks[_index] = userLocks[userLocks.length-1];
    userLocks.pop();
    if (userLocks.length == 0) {
      users[msg.sender].lockedTokens.remove(_lpToken);
    }
    transferredLock.owner = _newOwner;
  }
  
  /**
   * @notice migrates liquidity to uniswap v3
   */
  function migrate (address _lpToken, uint256 _index, uint256 _lockID, uint256 _amount) external nonReentrant {
    require(address(migrator) != address(0), "NOT SET");
    require(_amount > 0, 'ZERO MIGRATION');
    
    uint256 lockID = users[msg.sender].locksForToken[_lpToken][_index];
    TokenLock storage userLock = tokenLocks[_lpToken][lockID];
    require(lockID == _lockID && userLock.owner == msg.sender, 'LOCK MISMATCH'); // ensures correct lock is affected
    userLock.amount = userLock.amount.sub(_amount);
    
    // clean user storage
    if (userLock.amount == 0) {
      uint256[] storage userLocks = users[msg.sender].locksForToken[_lpToken];
      userLocks[_index] = userLocks[userLocks.length-1];
      userLocks.pop();
      if (userLocks.length == 0) {
        users[msg.sender].lockedTokens.remove(_lpToken);
      }
    }
    
    TransferHelper.safeApprove(_lpToken, address(migrator), _amount);
    migrator.migrate(_lpToken, _amount, userLock.unlockDate, msg.sender);
  }
  
  function getNumLocksForToken (address _lpToken) external view returns (uint256) {
    return tokenLocks[_lpToken].length;
  }
  
  function getNumLockedTokens () external view returns (uint256) {
    return lockedTokens.length();
  }
  
  function getLockedTokenAtIndex (uint256 _index) external view returns (address) {
    return lockedTokens.at(_index);
  }
  
  // user functions
  function getUserNumLockedTokens (address _user) external view returns (uint256) {
    UserInfo storage user = users[_user];
    return user.lockedTokens.length();
  }
  
  function getUserLockedTokenAtIndex (address _user, uint256 _index) external view returns (address) {
    UserInfo storage user = users[_user];
    return user.lockedTokens.at(_index);
  }
  
  function getUserNumLocksForToken (address _user, address _lpToken) external view returns (uint256) {
    UserInfo storage user = users[_user];
    return user.locksForToken[_lpToken].length;
  }
  
  function getUserLockForTokenAtIndex (address _user, address _lpToken, uint256 _index) external view 
  returns (uint256, uint256, uint256, uint256, uint256, address) {
    uint256 lockID = users[_user].locksForToken[_lpToken][_index];
    TokenLock storage tokenLock = tokenLocks[_lpToken][lockID];
    return (tokenLock.lockDate, tokenLock.amount, tokenLock.initialAmount, tokenLock.unlockDate, tokenLock.lockID, tokenLock.owner);
  }
  
  // whitelist
  function getWhitelistedUsersLength () external view returns (uint256) {
    return feeWhitelist.length();
  }
  
  function getWhitelistedUserAtIndex (uint256 _index) external view returns (address) {
    return feeWhitelist.at(_index);
  }
  
  function getUserWhitelistStatus (address _user) external view returns (bool) {
    return feeWhitelist.contains(_user);
  }
}