ranking

ranking.sol

pragma solidity >=0.7.0 <0.8.0;

contract rankingApp
{
    uint256 nThings;
    address private owner;
    mapping (string => uint256) public things;
    mapping (uint256 => uint256) public ratings;
    
    constructor() {
        owner = msg.sender;
    }
    
    modifier isOwner() {
        require(msg.sender == owner, "Caller is not owner");
        _;
    }
    
    function addItemToRate(string memory item) public isOwner {
        nThings++;
        things[item]=nThings;
        ratings[nThings]=1;
    }
    
    function downVote(string memory toDownVote) public{
        uint256 ind = things[toDownVote];
        if(ind == 0){
            revert();
        }
        ratings[ind]--;
    }
    
    function upVote(string memory toUpVote) public{
        uint256 ind = things[toUpVote];
        if(ind == 0){
            revert();
        }
        ratings[ind]++;
    }
}