internal ScoreSheet Sign(string signature)
{
var newScoreSheet = new ScoreSheet(this);
newScoreSheet.Signature = signature;
return(newScoreSheet);
}
internal ScoreSheet Finish()
{
var newScoreSheet = new ScoreSheet(this);
newScoreSheet.FinishedTimestamp = DateTimeOffset.Now;
return(newScoreSheet);
}
public ScoreSheet CompletePuzzle(ScoreSheet scoreSheet)
{
if (!IsAuthentic(scoreSheet))
{
throw new InvalidOperationException("Score sheet is not authentic");
}
if (!scoreSheet.CompletedPuzzles.Contains(scoreSheet.CurrentPuzzle))
{
scoreSheet = scoreSheet.Complete(scoreSheet.CurrentPuzzle);
}
var remainingPuzzles = Puzzle.Ids.Except(scoreSheet.CompletedPuzzles).ToArray();
if (remainingPuzzles.Any())
{
scoreSheet = scoreSheet.ChangeToPuzzle(PickOneAtRandom(remainingPuzzles));
}
else
{
scoreSheet = scoreSheet.Finish();
}
return(Sign(scoreSheet));
}
public ScoreSheet RegisterNewContestant(string name)
{
var firstQuestion = PickOneAtRandom(Puzzle.Ids);
var scoreSheet = new ScoreSheet(name, firstQuestion);
return(Sign(scoreSheet));
}
public static string ComputeSignature(this ScoreSheet scoresheet, string key)
{
var document = JsonSerializer.Serialize(new ScoreSheet(scoresheet));
using var hmac = new HMACSHA384(Encoding.UTF8.GetBytes(key));
return(Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(document))));
}
public ScoreSheet(ScoreSheet otherScoreSheet)
{
Name = otherScoreSheet.Name;
StartingTimestamp = otherScoreSheet.StartingTimestamp;
FinishedTimestamp = otherScoreSheet.FinishedTimestamp;
CompletedPuzzles = otherScoreSheet.CompletedPuzzles;
CurrentPuzzle = otherScoreSheet.CurrentPuzzle;
}
internal ScoreSheet ChangeToPuzzle(Guid puzzleId)
{
if (CompletedPuzzles.Contains(puzzleId))
{
throw new InvalidOperationException("Can't change to an already completed puzzle");
}
var newScoreSheet = new ScoreSheet(this);
newScoreSheet.CurrentPuzzle = puzzleId;
return(newScoreSheet);
}
internal ScoreSheet Complete(Guid puzzleId)
{
if (CurrentPuzzle != puzzleId)
{
throw new InvalidOperationException("Can only complete the current puzzle");
}
var newScoreSheet = new ScoreSheet(this);
newScoreSheet.CompletedPuzzles = newScoreSheet.CompletedPuzzles.Concat(new[] { puzzleId }).Distinct().ToArray();
return(newScoreSheet);
}
private ScoreSheet Sign(ScoreSheet scoreSheet)
{
var signature = scoreSheet.ComputeSignature(_signingKey);
return(scoreSheet.Sign(signature));
}
public bool IsAuthentic(ScoreSheet scoreSheet)
{
var expectedSignature = scoreSheet.ComputeSignature(_signingKey);
return(scoreSheet.Signature == expectedSignature);
}