pragma solidity ^0.4.24;
import "github.com/Arachnid/solidity-stringutils/strings.sol";

contract registry {
    using strings for *;
    struct Certificate {
        //mapping(address => bool) attested;
        mapping(address => string) ipfsRootHash;
    }

    mapping(string => Certificate) certificates;

    function attest(string _hash, string _ipfsRootHash) public {
        Certificate storage currentCertificate = certificates[_hash];
        if (_ipfsRootHash.toSlice().len() > 0) {
            currentCertificate.ipfsRootHash[msg.sender] = _ipfsRootHash;
        } else {
            currentCertificate.ipfsRootHash[msg.sender] = "default";
        }

    }

    function verify(string _hash) public view returns (string) {
        return certificates[_hash].ipfsRootHash[msg.sender];
    }
}