/**
* Selects the next question base appropriate for the quiz attempt passed
* @param Model_Quiz_QuizAttempt $vQuizAttempt
* @param boolean $debug Being Phased out TODO
* @throws Exception
* @return Model_Quiz_QuestionBase|NULL NULL Should only be returned in exceptional circumstances
*/
public static function select_next_question($vQuizAttempt, $debug = false)
{
//Get all the concepts this quiz tests
$vQuiz = $vQuizAttempt->getQuiz();
$vTestedConcepts = $vQuiz->getTestedConcepts();
if (sizeof($vTestedConcepts) < 1) {
throw new Exception("This quiz is not ready yet - reason: No testedConcepts specified.");
}
//Foreach concept tested, see how many questions we've attempted
foreach ($vTestedConcepts as $vTestedConcept) {
Model_Shell_Debug::getInstance()->log("Looking at TestedConcept: " . $vTestedConcept->getConcept()->getConcept_name());
$vQuestionAttempts = Model_Quiz_QuestionAttempt::getAllFromQuizAttemptAndConcept($vQuizAttempt, $vTestedConcept->getConcept());
Model_Shell_Debug::getInstance()->log("Done " . sizeof($vQuestionAttempts) . "/" . $vTestedConcept->getNumber_tested());
//If we haven't attempted enough in this concept, we need to choose a question difficulty
if (sizeof($vQuestionAttempts) < $vTestedConcept->getNumber_tested()) {
//What difficulties are there being tested within this concept?
$vLowest = $vTestedConcept->getLower_difficulty();
$vHighest = $vTestedConcept->getHigher_difficulty();
//Find out how many questions I should allocate for each difficulty
$mQuestionsPerDifficultyLevel = floor(0.8 / ($vHighest + 1 - $vLowest) * $vTestedConcept->getNumber_tested());
$mBuffer = $vTestedConcept->getNumber_tested() - ($vHighest + 1 - $vLowest) * $mQuestionsPerDifficultyLevel;
//If there's only one difficulty, that settles that
if ($vLowest == $vHighest) {
return Model_Shell_QuestionChooser::select_next_question_2($vQuizAttempt, $vTestedConcept->getConcept(), $vLowest);
}
//Were there any previous attempts at this concept? If not, we need to start a Q at the lowest specified difficulty
$vQuestionAttempts = $vQuizAttempt->getQuestionAttempts($vTestedConcept->getConcept());
//echo "Size of vQuestionAttempts:".sizeof($vQuestionAttempts)."<br/>";
if (sizeof($vQuestionAttempts) == 0) {
return Model_Shell_QuestionChooser::select_next_question_2($vQuizAttempt, $vTestedConcept->getConcept(), $vLowest);
}
//Find the highest attempted difficulty done so far
$vHighestSoFar = $vQuizAttempt->getHighestDifficultyTestedSoFar();
//echo "The highest difficulty so far: $vHighestSoFar<br/>";
if ($vHighestSoFar >= $vHighest) {
//Already at the highest difficulty, the next question will be at this difficulty too
return Model_Shell_QuestionChooser::select_next_question_2($vQuizAttempt, $vTestedConcept->getConcept(), $vHighest);
}
//Look at the last attempts in this difficulty. Were they below-par (use a percentage?)?
$vTotal = 0;
$vTotalRight = 0;
Model_Shell_Debug::getInstance()->log("Checking your previous attempts...Size of vQuestionAttempts:" . sizeof($vQuestionAttempts));
foreach ($vQuestionAttempts as $vQA) {
$vQB = $vQA->getQuestion_base();
//echo "Looking at " . $vQB->getDifficulty() . " vs $vHighestSoFar<br/>";
if ($vQB->getDifficulty() == $vHighestSoFar) {
$vTotal++;
if ($vQB->getEstimated_time() > $vQA->getTime_finished() - $vQA->getTime_started()) {
//You did this question in a reasonable time... did you get it right first time?
if ($vQA->getInitial_result() == "1") {
$vTotalRight++;
}
}
}
}
//Note, a divide by 0 happened here before...
if ($vTotal == 0 || $vTotalRight / $vTotal > 0.8) {
//OK. If they WERE good attempts, I should move on if I've hit my quota for this difficulty
if ($vTotal >= $mQuestionsPerDifficultyLevel) {
//Reached our minumum quota for this difficulty level. NEXT!
return Model_Shell_QuestionChooser::select_next_question_2($vQuizAttempt, $vTestedConcept->getConcept(), $vHighestSoFar + 1);
} else {
//We've done well so far, but we need to do more in this difficulty
return Model_Shell_QuestionChooser::select_next_question_2($vQuizAttempt, $vTestedConcept->getConcept(), $vHighestSoFar);
}
} else {
//Your previous attempts weren't all that good.
//Figure out how much buffer we have left. Can we afford to give you a question at $vHighestSoFar? Or do we have to move onto something harder?
$mBuffer = $vTestedConcept->getNumber_tested() - ($vHighest - $vHighestSoFar) * $mQuestionsPerDifficultyLevel - sizeof($vQuestionAttempts);
if ($mBuffer > 1) {
//We can afford to give you another easier question
return Model_Shell_QuestionChooser::select_next_question_2($vQuizAttempt, $vTestedConcept->getConcept(), $vHighestSoFar);
} else {
//Sorry.. buffer is dry. You weren't going too well, but you gotta do the harder stuff
return Model_Shell_QuestionChooser::select_next_question_2($vQuizAttempt, $vTestedConcept->getConcept(), $vHighestSoFar + 1);
}
}
}
//End If
}
//End Foreach testedConcept
//We shouldn't really ever get here, but in case we do -> null
return null;
}
