//Make sure that all answers pertain to the intended quiz and are all for the same question.
public IEnumerable <Answer> ValidateAnswers(Data.Entities.Quizzes.Quiz quiz, IEnumerable <Answer> allAnswers, IEnumerable <long> answerIds)
{
var setAnswerIds = new HashSet <long>(answerIds);
var answers = allAnswers.Where(a => setAnswerIds.Contains(a.Id)).ToList();
long questionId = -1;
foreach (var answer in answers)
{
if (questionId == -1)
{
questionId = answer.QuestionId;
if (answer.Question.QuizId != quiz.Id)
{
throw new QuizAnswersNotForQuizException(answer.Id, quiz.Id, answer.Question.QuizId);
}
}
else if (questionId != answer.QuestionId)
{
throw new QuizAnswersNotSameQuestionException(answer.Id, questionId, answer.QuestionId);
}
}
return(answers);
}
//Determines the next question to provide for the person based on the questions which they have not yet answered.
public Question NextQuestion(Data.Entities.Quizzes.Quiz quiz, Person person, IEnumerable <Question> allQuestions, IEnumerable <PersonAnswer> allPersonAnswers)
{
var questions = allQuestions.Where(q => q.QuizId == quiz.Id);
var questionIdsOfPersonAnswers = new HashSet <long>(allPersonAnswers.Select(a => a.Answer.QuestionId));
//We only are concerned with unanswered questions.
var availableQuestions = questions.Where(q => !questionIdsOfPersonAnswers.Contains(q.Id));
if (quiz.RandomizeQuestions)
{
availableQuestions = availableQuestions.Shuffle(_randomizer);
}
var question = availableQuestions.FirstOrDefault();
if (question != null && question.RandomizeAnswers)
{
question.Answers = question.Answers.Shuffle(_randomizer).ToList();
}
return(question);
}
