// 'GetHashCode() for String' does not guarantee unique code for different strings, but, nevertheless, the chance of collisions is not so high.
// So, I use it and try to write a value to the DB, given the presence of an index in the database,
// which will throw an error if will getting collision and code will try again with a new id.
private async Task <string> GenerateShortAlias(string fullLink, string userId)
{
var tryCount = 0;
while (tryCount < 3)
{
try
{
var id = ObjectId.GenerateNewId().ToString();
var shortAlias = _shortenerService.GenerateShortString(id.GetHashCode());
var newLink = new Link(id, userId, shortAlias, fullLink);
await _linkRepository.CreateNewLink(newLink);
return(newLink.ShortAlias);
}
catch (MongoDB.Driver.MongoDuplicateKeyException)
{
tryCount++;
}
}
throw new InvalidOperationException("Three tries not enough for resolve collisions!");
}