function deposit(bytes32 _listingHash, uint _amount) external {
        Listing storage listingHash = listings[_listingHash];

        require(listingHash.owner == msg.sender);
        require(token.transferFrom(msg.sender, this, _amount));

        listingHash.unstakedDeposit += _amount;

        _Deposit(_listingHash, _amount, listingHash.unstakedDeposit);
    }