<?php
namespace TestProject;

/*
 * Question class
 */
class Question extends Item {
	private const tb_str       = 'question';
	private const resultTb_str = 'question_result';

	private $text_str;
	private $answers_arr;

	/**
	 * Load question
	 *
	 * @param int $id_int ID of question to load
	 */
	public function __construct( int $id_int ){
		$db = DB::getDB();

		$rows_arr = $db->select( self::tb_str, array(), array( 'id' => $id_int ) );

		if ( empty( $rows_arr ) ){
			throw new \RuntimeException( 'Invalid question ID' );
		}

		$this->id_int   = $rows_arr[0]['id'];
		$this->text_str = $rows_arr[0]['text'];

		$answerID_arr = Answer::getList( $this->id_int );
		$this->answers_arr = array();

		foreach( $answerID_arr as $answerID_int ){
			$this->answers_arr[] = new Answer( $answerID_int );
		}
	}

	/**
	 * Get a list of question IDs for a quiz
	 *
	 * @param int $quizID_int ID of quiz to load questions for
	 *
	 * @return int[] Array of question IDs
	 */
	public static function getList( int $quizID_int ){
		$db = DB::getDB();

		$rows_arr = $db->select( self::tb_str, array( 'id' ), array( 'quiz' => $quizID_int ) );

		$id_arr = array();
		foreach( $rows_arr as $row_arr ){
			$id_arr[] = $row_arr['id'];
		}

		return $id_arr;
	}

	/**
	 * Get question text
	 *
	 * @return string Question text
	 */
	public function getText(){
		return $this->text_str;
	}

	/**
	 * Get Answers for question
	 *
	 * @return TestProject\Answer[] Array of answer objects
	 */
	public function getAnswers(){
		return $this->answers_arr;
	}

	/**
	 * Calculate user's score and save to DB
	 *
	 * @param int $userID_int ID of user
	 * @param int[] $ans_arr Array of answer IDs
	 */
	public function saveAnswer( int $userID_int, $ans_arr ){
		$maxScore_int = 0;
		$score_int    = 0;

		foreach( $this->answers_arr as $answer ){
			if ( $answer->isCorrect() ){
				$maxScore_int++;

				// User selected correct answer
				if ( in_array( $answer->getID(), $ans_arr ) ){
					$score_int++;
				}
			}
		}

		// Apply penalty if more answers selected than correct options
		$diff_int = count( $ans_arr ) - $maxScore_int;
		if ( $diff_int > 0 ){
			$score_int -= $diff_int;
		}
		// Do not allow a negative score
		if ( $score_int < 0 ){
			$score_int = 0;
		}

		$db = DB::getDB();

		// Check for existing answer
		$row_arr = $db->select( self::resultTb_str, array( 'id' ), array( 'user' => $userID_int, 'question' => $this->id_int ) );
		if ( empty( $row_arr ) ){
			$db->insert(
				self::resultTb_str,
				array(
					'user'     => $userID_int,
					'question' => $this->id_int,
					'score'    => $score_int
				)
			);
		} else {
			$db->update( self::resultTb_str, array( 'score' => $score_int ), array( 'id' => $row_arr[0]['id'] ) );
		}
	}

	/**
	 * Get a user's score for the question
	 *
	 * @param int $userID_int ID of user
	 *
	 * @return int Score
	 */
	public function getScore( int $userID_int ){
		$db = DB::getDB();

		$row_arr = $db->select( self::resultTb_str, array( 'score' ), array( 'user' => $userID_int, 'question' => $this->id_int ) );
		if ( empty( $row_arr ) ){
			// Question not answered
			return 0;
		}

		return $row_arr[0]['score'];
	}
}