CryptoAlarm Smart Contract

pragma solidity ^0.5.7;

contract AlarmClock {

    mapping (address => uint) userComittedMoney;
    mapping (address => address) alarmAddress;
    /*
        Charity hard codded address
    */
    address payable charityAddress = HARD_CODDED_CHARITY_ADDRESS;
    /*
        Money locking function, user will lock money into this contract
        @param _alarmAddress user's alarm address
    */
    function lockMyMoney(address _alarmAddress) public payable{
        userComittedMoney[msg.sender] = msg.value;
        alarmAddress[msg.sender] = _alarmAddress;
    }
    /*
        Spending function, alarm will spend money from contract if
        user failed to wake up on time.
        @param _alarmAddress user's alarm address
        @param _amount  amount to be charged from user
    */
    function spend(address _alarmAddress, uint _amount) public{
        require(userComittedMoney[msg.sender] >= _amount && alarmAddress[msg.sender]== _alarmAddress);
            charityAddress.transfer(_amount);
            userComittedMoney[msg.sender]-=_amount;
    }
    /*
        Withdraw money function, if user decided to stop trial, he/she will withdraw the rest
        of the money if exists.
        @param _alarmAddress user's alarm address
    */
    function withdrawMoney(address _alarmAddress) public {
        require(alarmAddress[msg.sender] == _alarmAddress  && userComittedMoney[msg.sender]>0);
        msg.sender.transfer(userComittedMoney[msg.sender]);
    }
}