contract TokenLock {
    using SafeMath for uint256;
    address public owner;
    address public md_address;
    
    struct LockRecord {
        address userAddress;
        uint256 amount;
        uint256 releaseTime;
    }
    
    LockRecord[] lockRecords;
    mapping(uint256 => bool) lockStatus;
    
    MD md;

    event Deposit(address indexed _userAddress, uint256 _amount, uint256 _releaseTime, uint256 _index);
    event Release(address indexed _userAddress, address indexed _merchantAddress, uint256 _merchantAmount, uint256 _releaseTime, uint256 _index);
    
    modifier ownerOnly {
      require(
            msg.sender == owner,
            "Sender not authorized."
        );
        _;
    }
    
    //constructor
    constructor(address _owner, address _md_address) public{
        owner = _owner;
        md_address = _md_address;
        md = MD(md_address);
    }

    function getContractBalance() public view returns (uint256 _balance) {
        return md.balanceOf(this);
    }
    
    function deposit(address _userAddress, uint256 _amount, uint256 _days) public ownerOnly {
        require(_amount > 0);
        require(md.transferFrom(_userAddress, this, _amount));
        uint256 releaseTime = block.timestamp + _days * 1 days;
        LockRecord memory r = LockRecord(_userAddress, _amount, releaseTime);
        uint256 l = lockRecords.push(r);
        emit Deposit(_userAddress, _amount, releaseTime, l.sub(1));
    }
    
    function release(uint256 _index, address _merchantAddress, uint256 _merchantAmount) public ownerOnly {
        require(
            lockStatus[_index] == false,
            "Already released."
        );
        
        LockRecord storage r = lockRecords[_index];
        
        require(
            r.releaseTime <= block.timestamp,
            "Release time not reached"
        );
        
        require(
            _merchantAmount <= r.amount,
            "Merchant amount larger than locked amount."
        );

        
        if (_merchantAmount > 0) {
            require(md.transfer(_merchantAddress, _merchantAmount));
        }
        
        uint256 remainingAmount = r.amount.sub(_merchantAmount);
        if (remainingAmount > 0){
            require(md.transfer(r.userAddress, remainingAmount));
        }

        lockStatus[_index] = true;
        emit Release(r.userAddress, _merchantAddress, _merchantAmount, r.releaseTime, _index);
    }
    
    /**
     * Change owner address (where ICO ETH is being forwarded).
     */
    function changeOwner(address _newowner) public ownerOnly returns (bool success) {
        owner = _newowner;
        return true;
    }
    
    // forward all eth to owner
    function() payable public {
        if (!owner.call.value(msg.value)()) revert();
    }

    // only owner can kill
    function kill() public ownerOnly {
        md.transfer(owner, getContractBalance());
        selfdestruct(owner);
    }

}
function kill() public ownerOnly {
        md.transfer(owner, getContractBalance());
        selfdestruct(owner);
    }
// only owner can kill