<?php

/**
 * Class LP_Question_CURD
 *
 * @author  ThimPress
 * @package LearnPress/Classes/CURD
 * @since   3.0.0
 */

/**
 * Prevent loading this file directly
 */
defined( 'ABSPATH' ) || exit();

if ( ! class_exists( 'LP_Question_CURD' ) ) {

	/**
	 * Class LP_Question_CURD
	 */
	class LP_Question_CURD extends LP_Object_Data_CURD implements LP_Interface_CURD {

		/**
		 * LP_Question_CURD constructor.
		 */
		public function __construct() {
			$this->_error_messages = array(
				'QUESTION_NOT_EXISTS' => __( 'The question does not exist.', 'learnpress' ),
			);
		}

		/**
		 * Create question and can add to quiz.
		 *
		 * @param $args
		 *
		 * @return bool|int|LP_Question|WP_Error
		 */
		public function create( &$args ) {
			$args = wp_parse_args(
				$args,
				array(
					'quiz_id'        => 0,
					'order'          => - 1,
					'id'             => '',
					'status'         => 'publish',
					'type'           => 'true_or_false',
					'title'          => __( 'New Question', 'learnpress' ),
					'content'        => '',
					'create_answers' => true,
				)
			);

			// set question author for author of quiz
			if ( ! empty( $args['quiz_id'] ) ) {
				$user_id = get_post_field( 'post_author', $args['quiz_id'] );
			} else {
				$user_id = learn_press_get_current_user_id();
			}

			$question_id = wp_insert_post(
				array(
					'ID'           => $args['id'],
					'post_author'  => $user_id,
					'post_type'    => LP_QUESTION_CPT,
					'post_status'  => $args['status'],
					'post_title'   => $args['title'],
					'post_content' => $args['content'],
				)
			);

			if ( $question_id ) {
				// add default meta for new lesson
				$default_meta = LP_Question::get_default_meta();

				if ( is_array( $default_meta ) ) {
					foreach ( $default_meta as $key => $value ) {
						update_post_meta( $question_id, '_lp_' . $key, $value );
					}
				}
				update_post_meta( $question_id, '_lp_type', $args['type'] );
				// update user memory question types
				get_user_meta( $user_id, '_learn_press_memorize_question_types', $args['type'] );

				$question = LP_Question::get_question( $question_id, array( 'type' => $args['type'] ) );
				$question->set_type( $args['type'] );

				// add question to quiz
				if ( ! empty( $args['quiz_id'] ) ) {
					$quiz_curd = new LP_Quiz_CURD();
					$quiz_curd->add_question( $args['quiz_id'], $question_id, $args['order'] );
				}

				if ( $args['create_answers'] ) {
					$question->create_default_answers();
				}

				do_action( 'learn-press/after-create-question', $question );

				return $question;
			}

			return $question_id;
		}


		public function update( &$question ) {
			return $question;
			// TODO: Implement update() method.
		}

		/**
		 * Delete all question's related data before run wp_delete_post(), hook to before delete question hook.
		 *
		 * @since 3.0.0
		 *
		 * @param object $question_id
		 */
		public function delete( &$question_id ) {
			// remove all answer of question from {$wpdb->prefix}learnpress_question_answers table
			$this->clear( $question_id );

			// quiz curd
			$curd = new LP_Quiz_CURD();

			// allow hook
			do_action( 'learn-press/before-delete-question', $question_id );

			// get the quizzes that a question is assigned to, return WP Post
			$quiz = $this->get_quiz( $question_id );

			// remove question from quiz
			if ( $quiz ) {
				$curd->remove_questions( $quiz->ID, $question_id );
			}
		}

		/**
		 * Duplicate question.
		 *
		 * @since 3.0.0
		 *
		 * @param       $question_id
		 * @param array       $args
		 *
		 * @return mixed|WP_Error
		 */
		public function duplicate( &$question_id, $args = array() ) {
			if ( ! $question_id ) {
				return new WP_Error( 'lp/question/curd/duplicate/err', 'Oops! ID not found' );
			}

			if ( learn_press_get_post_type( $question_id ) != LP_QUESTION_CPT ) {
				return new WP_Error( 'lp/question/curd/duplicate/err', 'Op! The question does not exist' );
			}

			// ensure that user can create question
			if ( ! current_user_can( 'edit_posts' ) ) {
				return new WP_Error( 'lp/question/curd/duplicate/err', 'Sorry! You do not have permission to duplicate this question' );
			}

			// origin question
			$question = LP_Question::get_question( $question_id );

			// duplicate question
			$new_question_id = learn_press_duplicate_post( $question_id, array( 'post_status' => 'publish' ) );

			if ( ! $new_question_id || is_wp_error( $new_question_id ) ) {
				return new WP_Error( 'lp/question/curd/duplicate/err', 'Sorry! Failed to duplicate the question!' );
			} else {

				// init new question
				$new_question = LP_Question::get_question( $new_question_id );

				// set data
				$new_question->set_type( $question->get_type() );
				$new_question->set_data( 'answer_options', $question->get_data( 'answer_options' ) );

				// trigger change user memorize question types
				$user_id = get_current_user_id();
				update_user_meta( $user_id, '_learn_press_memorize_question_types', $new_question->get_type() );

				// duplicate answer
				$this->duplicate_answer( $question_id, $new_question_id );

				do_action( 'learn-press/item/after-duplicate', $question_id, $new_question_id, $args );

				return $new_question_id;
			}
		}

		/**
		 * Duplicate answer question.
		 *
		 * @param $question_id     | origin question
		 * @param $question_id_clone | new question
		 * @version 3.0.1
		 * @since 1.0.1
		 */
		public function duplicate_answer( $question_id, $question_id_clone ) {
			$lp_db                  = LP_Database::getInstance();
			$lp_question_answers_db = LP_Question_Answers_DB::getInstance();

			try {
				// Get all answer of question
				$filter_get_answer_options               = new LP_Question_Answers_Filter();
				$filter_get_answer_options->question_ids = [ $question_id ];
				$answer_options                          = $lp_question_answers_db->get_question_answers( $filter_get_answer_options );

				if ( $answer_options ) {
					foreach ( $answer_options as $answer_option ) {
						$question_answer_id = $answer_option->question_answer_id;

						// Insert new question_answer
						$insert_question_answer_rs = $lp_db->wpdb->insert(
							$lp_db->tb_lp_question_answers,
							array(
								'question_id' => $question_id_clone,
								'title'       => ! empty( $answer_option->title ) ? $answer_option->title : '',
								'value'       => ! empty( $answer_option->value ) ? $answer_option->value : '',
								'is_true'     => ! empty( $answer_option->is_true ) ? $answer_option->is_true : '',
								'order'       => $answer_option->order,
							),
							array( '%d', '%s', '%s', '%s', '%s' )
						);

						if ( ! $insert_question_answer_rs ) {
							throw new Exception( __( 'Failed to duplicate answer', 'learnpress' ) );
						}

						// Get question_answer_id have just inserted
						$filter_question_answer_id                      = new LP_Question_Answers_Filter();
						$filter_question_answer_id->only_fields         = [ 'MAX(question_answer_id)' ];
						$filter_question_answer_id->question_ids        = [ $question_id_clone ];
						$filter_question_answer_id->return_string_query = true;
						$question_answer_id_query                       = $lp_question_answers_db->get_question_answers( $filter_question_answer_id );
						$question_answer_id_new                         = (int) $lp_question_answers_db->wpdb->get_var( $question_answer_id_query );

						if ( ! $question_answer_id_new ) {
							throw new Exception( __( 'Failed to duplicate answer', 'learnpress' ) );
						}

						// Duplicate answer meta
						// Get answer meta by question_answer_id
						$filter_get                   = new LP_Question_Answermeta_Filter();
						$filter_get->collection       = $lp_db->tb_lp_question_answermeta;
						$filter_get->collection_alias = 'qam';
						$filter_get->field_count      = 'meta_id';
						$filter_get->limit            = -1;
						$filter_get->where[]          = $lp_db->wpdb->prepare( 'AND qam.learnpress_question_answer_id = %d', $question_answer_id );
						$filter_get->fields           = $lp_db->get_cols_of_table( $lp_db->tb_lp_question_answermeta );
						$question_answermeta_rs       = $lp_db->execute( $filter_get );

						foreach ( $question_answermeta_rs as $question_answermeta ) {
							$lp_db->wpdb->insert(
								$lp_db->tb_lp_question_answermeta,
								array(
									'learnpress_question_answer_id' => $question_answer_id_new,
									'meta_key'   => $question_answermeta->meta_key,
									'meta_value' => $question_answermeta->meta_value,
								),
								array( '%d', '%s', '%s' )
							);
						}
					}
				}
			} catch ( Throwable $e ) {
				error_log( $e->getMessage() );
			}
		}

		/**
		 * @param LP_Question $question
		 *
		 * @return bool
		 * @throws Exception
		 */
		public function load( &$question ) {
			// question id
			$id = $question->get_id();

			if ( ! $id || ! in_array( learn_press_get_post_type( $id ), array( 'revision', LP_QUESTION_CPT ) ) ) {
				throw new Exception( sprintf( __( 'Invalid question with ID "%d".', 'learnpress' ), $id ) );
			}

			$question->set_explanation( get_post_meta( $id, '_lp_explanation', true ) );
			$question->set_hint( get_post_meta( $id, '_lp_hint', true ) );
			// $this->_load_answer_options( $question );
			$this->_load_meta( $question );

			return true;
		}

		/**
		 * @param $question | LP_Question
		 */
		protected function _load_meta( &$question ) {
			$type = get_post_meta( $question->get_id(), '_lp_type', true );
			if ( ! learn_press_is_support_question_type( $type ) ) {
				$type = 'true_or_false';
			}
			// $question->set_type( $type );

			$mark = $this->_get_question_mark( $question->get_id() );
			$question->set_mark( $mark );
		}

		public function _get_question_mark( $question_id ) {

			// Recheck _lp_mark @tungnx
			$mark = get_post_meta( $question_id, '_lp_mark', true ) ? get_post_meta( $question_id, '_lp_mark', true ) : 0;

			$mark = abs( $mark );
			if ( ! $mark ) {
				$mark = apply_filters( 'learn-press/question/default-mark', 1, $question_id );
				update_post_meta( $question_id, '_lp_mark', $mark );
			}

			return $mark;
		}

		/**
		 * Get the quizzes that a question is assigned to.
		 *
		 * @since 3.0.0
		 *
		 * @param $question_id
		 *
		 * @return null|object WP_Post
		 */
		public function get_quiz( $question_id ) {
			global $wpdb;

			$query = $wpdb->prepare(
				"
	  			SELECT post.* FROM {$wpdb->posts} post
				INNER JOIN {$wpdb->prefix}learnpress_quiz_questions quiz ON post.ID = quiz.quiz_id
				WHERE quiz.question_id = %d
			",
				$question_id
			);

			// get single row
			return $wpdb->get_row( $query );
		}

		/**
		 * Change question type.
		 *
		 * @param $question LP_Question
		 * @param $new_type
		 *
		 * @return false|void
		 * @since 3.0.0
		 * @version 1.0.1
		 */
		public function change_question_type( &$question, $new_type ) {
			if ( learn_press_get_post_type( $question->get_id() ) != LP_QUESTION_CPT ) {
				return false;
			}

			$question_id = $question->get_id();

			// If not new Question or not change type return
			$old_type    = get_post_meta( $question_id, '_lp_type', true );
			if ( ! empty( $old_type ) && $old_type === $new_type ) {
				return;
			}

			$answer_options = $question->get_data( 'answer_options' );
			update_post_meta( $question_id, '_lp_type', $new_type );
			$question->set_type( $new_type );

			$new_question = LP_Question::get_question( $question_id, array( 'force' => true ) );

			if ( $new_question ) {
				$user_id = get_current_user_id();
				update_user_meta( $user_id, '_learn_press_memorize_question_types', $new_type );

				if ( $old_type == 'multi_choice' && $new_type == 'single_choice' ) {
					$func = '_convert_answers_multi_choice_to_single_choice';
				} elseif ( ( $old_type == 'multi_choice' || $old_type == 'single_choice' ) && 'true_or_false' == $new_type ) {
					$func = '_convert_answers_to_true_or_false';
				} else {
					// for rest, clear answer data and create default
					$func = '_convert_default_answers';
				}

				if ( is_callable( array( $this, $func ) ) ) {
					$answer_options = call_user_func_array(
						array( $this, $func ),
						array(
							$question,
							$new_question,
							$answer_options,
						)
					);
				}

				LP_Object_Cache::set( 'answer-options-' . $question_id, $answer_options, 'learn-press/questions' );
				$new_question->set_data( 'answer_options', $answer_options );

				$question = $new_question;
			}
		}

		/**
		 * Update answer title
		 *
		 * @param $question_id
		 * @param $answer
		 *
		 * @return bool|false|int
		 */
		public function update_answer_title( $question_id, $answer ) {
			if ( get_post_type( $question_id ) !== LP_QUESTION_CPT ) {
				return false;
			}

			global $wpdb;

			// question data
			$data = array(
				'data'  => apply_filters(
					'learn-press/question/update-answer-data',
					array(
						'title'   => $answer['title'],
						'value'   => $answer['value'] ?? '',
						'is_true' => $answer['is_true'] ?? '',
					)
				),
				'where' => array(
					'question_answer_id' => $answer['question_answer_id'],
					'question_id'        => $question_id,
				),
			);

			$update = $wpdb->update(
				$wpdb->learnpress_question_answers,
				$data['data'],
				$data['where'],
				array( '%s', '%s', '%s' ),
				array( '%d', '%d' )
			);

			// Update for Fill in Blanks.
			if ( ! empty( $answer['blanks'] ) ) {
				$blanks = $answer['blanks'];

				/*if ( is_array( $blanks ) ) {
					$question = LP_Question::get_question( $question_id );

					foreach ( $blanks as $id => $blank ) {
						$question->_blanks[ $blank['id'] ] = $blank;
					}
				}*/

				learn_press_update_question_answer_meta( $answer['question_answer_id'], '_blanks', $blanks );
			}

			return $update;
		}

		/**
		 * Update correct answer.
		 *
		 * @param $question LP_Question
		 * @param $correct
		 *
		 * @return bool | LP_Question
		 */
		public function change_correct_answer( $question, $correct ) {
			if ( learn_press_get_post_type( $question->get_id() ) != LP_QUESTION_CPT ) {
				return false;
			}

			global $wpdb;

			$question_id      = $question->get_id();
			$question_type    = $question->get_type();
			$question_answers = $question->get_data( 'answer_options' );

			$db_args = $answers = array();

			foreach ( $question_answers as $index => $answer ) {

				$answer_data = array(
					'title'   => $answer['title'],
					'value'   => isset( $answer['value'] ) ? stripslashes( $answer['value'] ) : '',
					'is_true' => isset( $answer['is_true'] ) ? $answer['is_true'] : '',
				);

				// update correct for select answer
				if ( $answer['question_answer_id'] == $correct['question_answer_id'] ) {
					$answer_data['is_true'] = $correct['is_true'];
				} else {
					// untrue all rest answer with True or false and Single choice question
					if ( in_array( $question_type, array( 'true_or_false', 'single_choice' ) ) ) {
						$answer_data['is_true'] = '';
					}
				}

				// question answers data to set cache
				$answers[ $index ] = array(
					'question_answer_id' => $answer['question_answer_id'],
					'question_id'        => $question_id,
					'order'              => $answer['order'],
					'title'              => $answer_data['title'],
					'value'              => $answer_data['value'],
					'is_true'            => $answer_data['is_true'],
				);

				// new answers data
				$db_args[ $index ] = array(
					'data'  => array(
						'title'   => $answer_data['title'],
						'value'   => $answer_data['value'],
						'is_true' => $answer_data['is_true'],
					),
					'where' => array(
						'question_answer_id' => $answer['question_answer_id'],
						'question_id'        => $question_id,
						'order'              => $answer['order'],
					),
				);
			}

			// update db
			foreach ( $db_args as $id => $arg ) {
				$wpdb->update(
					$wpdb->learnpress_question_answers,
					$arg['data'],
					$arg['where'],
					array( '%s', '%s', '%s' ),
					array( '%d', '%d', '%d' )
				);
			}

			// set question answer data
			$question->set_data( 'answer_options', $answers );

			return $question;
		}

		/**
		 * Sort answers.
		 *
		 * @since 3.0.0
		 *
		 * @param       $question_id
		 * @param array       $order
		 *
		 * @return bool|LP_Question
		 */
		public function sort_answers( $question_id, $order = array() ) {

			if ( learn_press_get_post_type( $question_id ) !== LP_QUESTION_CPT ) {
				return false;
			}

			if ( $order ) {
				$question = LP_Question::get_question( $question_id );
				$answers  = $question->get_data( 'answer_options' );

				global $wpdb;
				$new_answers = array();
				foreach ( $order as $index => $answer_id ) {
					$wpdb->update(
						$wpdb->learnpress_question_answers,
						array( 'order' => $index + 1 ),
						array( 'question_answer_id' => $answer_id )
					);

					$new_answers[ $answer_id ] = $answers[ $answer_id ];
				}

				$question->set_data( 'answer_options', $new_answers );

				return $question;

			}

			return false;
		}

		/**
		 * Delete question answer.
		 *
		 * @param $question_id
		 * @param $answer_id
		 * @param $force
		 *
		 * @return bool|false|int
		 */
		public function delete_answer( $question_id, $answer_id, $force = false ) {

			if ( learn_press_get_post_type( $question_id ) !== LP_QUESTION_CPT ) {
				return false;
			}

			$question = LP_Question::get_question( $question_id );

			// exist answer options
			$answers = $question->get_data( 'answer_options' );

			global $wpdb;

			// Delete answer meta
			$wpdb->delete(
				$wpdb->learnpress_question_answermeta,
				array( 'learnpress_question_answer_id' => $answer_id )
			);

			$delete = $wpdb->delete(
				$wpdb->learnpress_question_answers,
				array( 'question_answer_id' => $answer_id )
			);
			if ( $delete ) {
				unset( $answers[ $answer_id ] );
				$question->set_data( 'answer_options', $answers );

				$this->sort_answers( $question_id, array_keys( $answers ) );
			}

			return $delete;
		}

		/**
		 * Add new answer.
		 *
		 * @param $question_id
		 * @param $new_answer
		 *
		 * @return bool|false|int
		 */
		public function new_answer( $question_id, $new_answer ) {
			if ( learn_press_get_post_type( $question_id ) !== LP_QUESTION_CPT ) {
				return false;
			}

			$question = LP_Question::get_question( $question_id );

			// exist answer options
			$answers = $question->get_data( 'answer_options' );
			// number answer options
			$number = count( $answers );

			if ( $question->get_type() === 'sorting_choice' ) {
				$new_answer['is_true'] = 'yes';
			}

			global $wpdb;

			$new_answer = wp_parse_args(
				$new_answer,
				array(
					'question_id' => $question_id,
					'title'       => '',
					'value'       => learn_press_random_value(),
					'is_true'     => '',
					'order'       => $number + 1,
				)
			);

			$insert = $wpdb->insert(
				$wpdb->learnpress_question_answers,
				$new_answer,
				learn_press_map_columns_format(
					$new_answer,
					array(
						'question_id' => '%d',
						'title'       => '%s',
						'value'       => '%s',
						'is_true'     => '%s',
						'order'       => '%d',
					)
				)
			);

			if ( $insert ) {
				$new_answer['question_answer_id'] = $wpdb->insert_id;

				if ( is_array( $answers ) ) {
					$answers = array_merge( $answers, array( $new_answer ) );
				} else {
					$answers = array( $new_answer );
				}
				$question->set_data( 'answer_options', $answers );
			}

			return $wpdb->insert_id;
		}


		/**
		 * Convert answers to true or false question.
		 *
		 * @since 3.0.0
		 *
		 * @param $question
		 * @param $new_question
		 * @param $answers
		 *
		 * @return mixed
		 */
		protected function _convert_answers_to_true_or_false( $question, $new_question, $answers ) {
			if ( is_array( $answers ) ) {
				// array answer ids
				$answer_ids = array_keys( $answers );

				if ( sizeof( $answers ) > 2 ) {
					global $wpdb;

					foreach ( $answers as $key => $answer ) {
						if ( array_search( $key, $answer_ids ) > 1 ) {
							$wpdb->delete(
								$wpdb->learnpress_question_answers,
								array( 'question_answer_id' => $answer['question_answer_id'] )
							);
						}
					}
					$answers = array_slice( $answers, 0, 2, true );
				}

				$correct = 0;
				foreach ( $answers as $key => $answer ) {
					if ( $answer['is_true'] == 'yes' ) {
						$correct += 1;
					}
				}

				if ( ! $correct ) {
					// for single choice deletes all correct, set first option is correct
					$answers[ $answer_ids[0] ]['is_true'] = 'yes';
				} elseif ( $correct == 2 ) {
					// for multiple choice keeps all correct, remove all correct and keep first option
					$answers[ $answer_ids[1] ]['is_true'] = 'no';
				}
			}

			return $answers;
		}

		/**
		 *
		 * Convert answers for multi choice to single choice question.
		 *
		 * @since 3.0.0
		 *
		 * @param $question
		 * @param $new_question
		 * @param $answers
		 *
		 * @return array
		 */
		protected function _convert_answers_multi_choice_to_single_choice( $question, $new_question, $answers ) {
			if ( is_array( $answers ) ) {
				// array answer ids
				$answer_ids = array_keys( $answers );

				$correct = 0;
				foreach ( $answers as $key => $answer ) {
					if ( $answer['is_true'] == 'yes' ) {
						$correct += 1;
					}
				}

				if ( ! $correct ) {
					$answers[ $answer_ids[0] ]['is_true'] = 'yes';
				} elseif ( $correct > 1 ) {
					// remove all correct and keep first option
					$answers[ $answer_ids[0] ]['is_true'] = 'no';
				}
			}

			return $answers;
		}

		/**
		 * Convert default answers.
		 *
		 * @param $question     LP_Question
		 * @param $new_question LP_Question
		 * @param $answers
		 *
		 * @return array
		 */
		protected function _convert_default_answers( $question, $new_question, $answers ) {
			$question_id = $question->get_id();
			// clear all exists answer
			$this->clear( $question_id );
			// set default answer
			$answer_options = $new_question->get_default_answers();

			if ( is_array( $answer_options ) ) {
				foreach ( $answer_options as $index => $answer ) {
					$insert        = array(
						'question_id' => $question_id,
						'title'       => $answer['title'],
						'value'       => isset( $answer['value'] ) ? stripslashes( $answer['value'] ) : '',
						'is_true'     => ( $answer['is_true'] == 'yes' ) ? $answer['is_true'] : '',
						'order'       => $index + 1,
					);
					$new_answers[] = $this->add_answer( $new_question->get_type(), $insert );
				};

				return $new_answers;
			}

			return $answers;
		}

		/**
		 * Add question answer.
		 *
		 * @since 3.0.0
		 *
		 * @param string $question_type
		 * @param array  $args
		 *
		 * @return array|bool
		 */
		public function add_answer( $question_type = '', $args = array() ) {
			global $wpdb;

			$question = LP_Question::get_question( $args['question_id'], array( 'type' => $question_type ) );

			$wpdb->insert(
				$wpdb->learnpress_question_answers,
				array(
					'question_id' => $args['question_id'],
					'title'       => $args['title'],
					'value'       => $args['value'],
					'is_true'     => $args['is_true'],
					'order'       => $args['order'],
				),
				array( '%d', '%s', '%s', '%s', '%d' )
			);

			$question_answer_id = $wpdb->insert_id;
			if ( $question_answer_id ) {
				// update question answer option data
				$answer_options = $question->get_data( 'answer_options' ) ? $question->get_data( 'answer_options' ) : array();

				$new_answer_option_data = array(
					'question_answer_id' => $question_answer_id,
					'question_id'        => $args['question_id'],
					'order'              => $args['order'],
					'title'              => $args['title'],
					'value'              => $args['value'],
					'is_true'            => $args['is_true'],
				);

				if ( ! $answer_options ) {
					$question->set_data( 'answer_options', array( $new_answer_option_data ) );
				} else {
					$answer_options[] = $new_answer_option_data;
					$question->set_data( 'answer_options', $answer_options );
				}

				return $new_answer_option_data;
			} else {
				return false;
			}
		}

		/**
		 * Delete question answer.
		 *
		 * @since 3.0.0
		 *
		 * @param $question_id
		 * @param $answer_id
		 *
		 * @return bool|false|int
		 */
		public function delete_question_answer( $question_id, $answer_id ) {
			if ( learn_press_get_post_type( $question_id ) !== LP_QUESTION_CPT || ! $answer_id ) {
				return false;
			}

			global $wpdb;

			$result = $wpdb->delete(
				$wpdb->learnpress_question_answers,
				array( 'question_answer_id' => $answer_id )
			);

			return $result;
		}

		/**
		 * Delete all question answers.
		 *
		 * @param $question_id
		 *
		 * @return bool|WP_Error
		 */
		public function clear( $question_id ) {

			if ( ! learn_press_get_question( $question_id ) ) {
				return $this->get_error( 'QUESTION_NOT_EXISTS' );
			}

			do_action( 'learn-press/before-clear-question', $question_id );

			global $wpdb;
			$wpdb->delete( $wpdb->learnpress_question_answers, array( 'question_id' => $question_id ) );

			return true;
		}

		/**
		 * Load answer options for the question from database.
		 * Load from cache if data is already loaded into cache.
		 * Otherwise, load from database and put to cache.
		 *
		 * @param int $question_id
		 *
		 * @return array
		 */
		protected function _read_answers( $question_id ) {
			global $wpdb;

			$query = $wpdb->prepare(
				"
				SELECT question_answer_id, title, value, is_true
				FROM {$wpdb->prefix}learnpress_question_answers
				WHERE question_id = %d
				ORDER BY `order` ASC
			",
				$question_id
			);

			$answer_options = array();

			$results = $wpdb->get_results( $query );

			if ( $results ) {
				foreach ( $results as $k => $v ) {
					$answer_option = array(
						'question_answer_id' => absint( $v->question_answer_id ),
						'title'              => $v->title,
						'value'              => $v->value,
						'is_true'            => $v->is_true,
						'order'              => $k + 1, // Need???
					);

					$answer_options[ $v->question_answer_id ] = $answer_option;
				}
			}

			return $answer_options;
		}

		/**
		 * Load question answers
		 *
		 * @updated 3.1.0
		 *
		 * @param array|int $question_id
		 *
		 * @return array|bool
		 */
		public function load_answer_options( $question_id ) {
			global $wpdb;

			$return_id = 0;

			if ( is_array( $question_id ) ) {

				foreach ( $question_id as $q_id ) {
					$this->load_answer_options( $q_id );
					if ( ! $return_id ) {
						$return_id = $q_id;
					}
				}
				$question_id = $return_id;
			}

			$answer_options = LP_Object_Cache::get( 'question-' . $question_id, 'question-answers' );

			if ( false === $answer_options ) {
				$answer_options = $this->_read_answers( $question_id );
				LP_Object_Cache::set( 'question-' . $question_id, $answer_options, 'question-answers' );
			}

			return $answer_options;
		}
	}
}
