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OwnershipProof.sol

pragma solidity ^0.4.23;

contract OwnershipProof{
    
    //FileDetails structure
    struct FileDetails {
        uint256 timestamp;
        string owner;
    }
    
    //mapping of owners to FileDetails
    mapping (string => FileDetails) files;
    
    //event to log while file is added
    event logFileAddedStatus(bool status,uint256 timestamp, string owner, string fileHash);
    
    //add a file to the files map if it does not exist
    function addFile(string owner, string fileHash) public {
        if(files[fileHash].timestamp == 0){
            files[fileHash] = FileDetails(block.timestamp, owner);
            emit logFileAddedStatus(true, block.timestamp, owner, fileHash);
        }else{
            emit logFileAddedStatus(false, block.timestamp, owner, fileHash);
        }
    }
    
    //get an exisiting file
    function getFile(string fileHash) public view returns(uint256 timestamp, string owner){
        return (files[fileHash].timestamp, files[fileHash].owner);
    }
}