woothemes / sensei

includes/class-sensei-teacher.php

<?php
if ( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly

/**
 * Sensei Teacher class
 *
 * All functionality pertaining to the teacher role.
 *
 * @package Users
 * @author Automattic
 * @since 1.0.0
 */
class Sensei_Teacher {

    /**
     * $teacher_role
     *
     * Keeps a reference to the teacher role object
     *
     * @access protected
     * @since 1.8.0
     */
    protected $teacher_role;

    /**
     * $token
     *
     * Keeps a reference to the global sensei token
     *
     * @access protected
     * @since 1.8.0
     */
    public  $token;

    /**
     * Sensei_Teacher::__constructor
     *
     * Constructor Function
     *
     * @since 1.8.0
     * @access public
     */
    public function __construct ( ) {

        add_action( 'add_meta_boxes', array( $this , 'add_teacher_meta_boxes' ) , 10, 2 );
        add_action( 'save_post',  array( $this, 'save_teacher_meta_box' ) );
        add_filter( 'parse_query', array( $this, 'limit_teacher_edit_screen_post_types' ));
        add_filter( 'pre_get_posts', array( $this, 'course_analysis_teacher_access_limit' ) );
        add_filter( 'wp_count_posts', array( $this, 'list_table_counts' ), 10, 3 );

        add_action( 'pre_get_posts', array( $this, 'filter_queries' ) );

        //filter the quiz submissions
        add_filter( 'sensei_check_for_activity' , array( $this, 'filter_grading_activity_queries') );

        //grading totals count only those belonging to the teacher
        add_filter('sensei_count_statuses_args', array( $this, 'limit_grading_totals' ) );

        // show the courses owned by a user on his author archive page
        add_filter( 'pre_get_posts', array( $this, 'add_courses_to_author_archive' ) );

        // notify admin when a teacher creates a course
        add_action( 'transition_post_status',array( $this, 'notify_admin_teacher_course_creation' ), 10, 3 );

        // limit the analysis view to only the users taking courses belong to this teacher
        add_filter( 'sensei_analysis_overview_filter_users',array( $this, 'limit_analysis_learners' ) , 5, 1 );

        // give teacher access to question post type
        add_filter( 'sensei_lesson_quiz_questions', array( $this, 'allow_teacher_access_to_questions' ), 20, 2 );

        // Teacher column on the courses list on the admin edit screen
        add_filter('manage_edit-course_columns' , array( $this, 'course_column_heading'), 10,1 );
        add_filter('manage_course_posts_custom_column' , array( $this, 'course_column_data'), 10,2 );

        //admin edit messages query limit teacher
        add_filter( 'pre_get_posts', array( $this, 'limit_edit_messages_query' ) );

        //add filter by teacher on courses list
        add_action( 'restrict_manage_posts', array( $this, 'course_teacher_filter_options' ) );
        add_filter( 'request', array( $this, 'teacher_filter_query_modify' ) );

        // Handle media library restrictions
        add_filter( 'request', array( $this, 'restrict_media_library' ), 10, 1 );
        add_filter( 'ajax_query_attachments_args', array( $this, 'restrict_media_library_modal' ), 10, 1 );

        // update lesson owner to course teacher when saved
        add_action( 'save_post',  array( $this, 'update_lesson_teacher' ) );

        // If a Teacher logs in, redirect to /wp-admin/
        add_filter( 'wp_login', array( $this, 'teacher_login_redirect') , 10, 2 );


        add_action( 'admin_menu', array( $this, 'restrict_posts_menu_page'), 10);
        add_filter('pre_get_comments',  array ($this, 'restrict_comment_moderation'), 10, 1);


    } // end __constructor()

    /**
     * Sensei_Teacher::create_teacher_role
     *
     * This function checks if the role exist, if not it creates it.
     * for the teacher role
     *
     * @since 1.8.0
     * @access public
     * @return void
     */
    public function create_role ( ) {

        // check if the role exists
        $this->teacher_role = get_role( 'teacher' );

        // if the the teacher is not a valid WordPress role create it
       if ( ! is_a( $this->teacher_role, 'WP_Role' ) ) {
           // create the role
           $this->teacher_role = add_role( 'teacher', __( 'Teacher', 'woothemes-sensei' ) );
       }

       // add the capabilities before returning
        $this->add_capabilities();

    }// end create_teacher_role

    /**
     * Sensei_Teacher::add_capabilities
     *
     * @since 1.8.0
     * @access protected
     */
    protected function add_capabilities ( ) {

        // if this is not a valid WP_Role object exit without adding anything
        if(  ! is_a( $this->teacher_role, 'WP_Role' ) || empty( $this->teacher_role ) ) {
            return;
        }

        /**
         * Sensei teachers capabilities array filter
         *
         * These capabilities will be applied to the teacher role
         * @param array $capabilities
         * keys: (string) $cap_name => (bool) $grant
         */
        $caps = apply_filters( 'sensei_teacher_role_capabilities', array(
            // General access rules
            'read' => true,
            'manage_sensei_grades' => true,
            'moderate_comments'=> true,
            'upload_files'	=> true,
            'edit_files'	=> true,

            //Lessons
            'publish_lessons'	 => true,
            'manage_lesson_categories'	 => true,
            'edit_lessons'	 => true,
            'edit_published_lessons'  => true,
            'edit_private_lessons' => true,
            'read_private_lessons' => true,
            'delete_published_lessons' => true,

            // Courses
            'create_courses' => true,
            'publish_courses'	 => false,
            'manage_course_categories'	 => true,
            'edit_courses'	 => true,
            'edit_published_courses'  => true,
            'edit_private_courses' => true,
            'read_private_courses' => true,
            'delete_published_courses' => true,

            // Quiz
            'publish_quizzes'	 => true,
            'edit_quizzes'	 => true,
            'edit_published_quizzes'  => true,
            'edit_private_quizzes' => true,
            'read_private_quizzes' => true,

            // Questions
            'publish_questions'	 => true,
            'edit_questions'	 => true,
            'edit_published_questions'  => true,
            'edit_private_questions' => true,
            'read_private_questions' => true,

            //messages
            'publish_sensei_messages'	 => true,
            'edit_sensei_messages'	 => true,
            'edit_published_sensei_messages'  => true,
            'edit_private_sensei_messages' => true,
            'read_private_sensei_messages' => true,

            // Comments -
            // Necessary cap so Teachers can moderate comments
            // on their own lessons. We restrict access to other
            // post types in $this->restrict_posts_menu_page()

            'edit_posts' => true,

        ));

        foreach ( $caps as $cap => $grant ) {

            // load the capability on to the teacher role
            $this->teacher_role->add_cap($cap, $grant);

        } // end for each

    }// end add_cap

    /**
     * Sensei_Teacher::teacher_meta_box
     *
     * Add the teacher metabox to the course post type edit screen
     *
     * @since 1.8.0
     * @access public
     * @parameter string $post_type
     * @parameter WP_Post $post
     * @return void
     */
    public function add_teacher_meta_boxes ( $post ) {

        if( !current_user_can('manage_options') ){
            return;
        }
        add_meta_box( 'sensei-teacher',  __( 'Teacher' , 'woothemes-sensei'),  array( $this , 'teacher_meta_box_content' ),
            'course',
            'side',
            'core'
        );

    } // end teacher_meta_box()

    /**
     * Sensei_Teacher::teacher_meta_box_content
     *
     * Render the teacher meta box markup
     *
     * @since 1.8.0
     * @access public
     * @parameters
     */
    public function teacher_meta_box_content ( $post ) {

        // get the current author
        $current_author = $post->post_author;

        //get the users authorised to author courses
        $users = $this->get_teachers_and_authors();

    ?>
        <select name="sensei-course-teacher-author" class="sensei course teacher">

            <?php foreach ( $users as $user_id ) { ?>

                    <?php
                        $user = get_user_by('id', $user_id);
                    ?>
                    <option <?php selected(  $current_author , $user_id , true ); ?> value="<?php echo $user_id; ?>" >
                        <?php echo  $user->display_name; ?>
                    </option>

            <?php }// end for each ?>

        </select>

        <?php

    } // end render_teacher_meta_box()

    /**
     * Sensei_Teacher::get_teachers_and_authors
     *
     * Get a list of users who can author courses, lessons and quizes.
     *
     * @since 1.8.0
     * @access public
     * @parameters
     * @return array $users user id array
     */
    public function get_teachers_and_authors ( ){

        $author_query_args = array(
            'blog_id'      => $GLOBALS['blog_id'],
            'fields'       => 'any',
            'who'          => 'authors'
        );

        $authors = get_users( $author_query_args );

        $teacher_query_args = array(
            'blog_id'      => $GLOBALS['blog_id'],
            'fields'       => 'any',
            'role'         => 'teacher',
        );

        $teachers = get_users( $teacher_query_args );

        return  array_unique( array_merge( $teachers, $authors ) );

    }// end get_teachers_and_authors

    /**
     * Sensei_Teacher::save_teacher_meta_box
     *
     * Save the new teacher / author to course and all lessons
     *
     * Hooked into admin_init
     *
     * @since 1.8.0
     * @access public
     * @parameters
     * @return array $users user id array
     */
    public function save_teacher_meta_box ( $course_id ){

        // check if this is a post from saving the teacher, if not exit early
        if(! isset( $_POST[ 'sensei-course-teacher-author' ] ) || ! isset( $_POST['post_ID'] )  ){
            return;
        }

        //don't fire this hook again
        remove_action('save_post', array( $this, 'save_teacher_meta_box' ) );

        // get the current post object
        $post = get_post( $course_id );

        // get the current teacher/author
        $current_author = absint( $post->post_author );
        $new_author = absint( $_POST[ 'sensei-course-teacher-author' ] );

        // loop through all post lessons to update their authors as well
        $this->update_course_lessons_author( $course_id , $new_author );

        // do not do any processing if the selected author is the same as the current author
        if( $current_author == $new_author ){
            return;
        }

        // save the course  author
        $post_updates = array(
            'ID' => $post->ID ,
            'post_author' => $new_author
        );
        wp_update_post( $post_updates );

        // ensure the the modules are update so that then new teacher has access to them
        Sensei_Teacher::update_course_modules_author( $course_id, $new_author );

        // notify the new teacher
        $this->teacher_course_assigned_notification( $new_author, $course_id );

    } // end save_teacher_meta_box

    /**
     * Update all the course terms set(selected) on the given course. Moving course term ownership to
     * the new author. Making sure the course terms are maintained.
     *
     * This function also checks if terms are shared, with other courses
     *
     * @param $course_id
     * @param $new_teacher_id
     * @return void
     */
    public static function update_course_modules_author( $course_id ,$new_teacher_id ){

        if( empty( $course_id ) || empty( $new_teacher_id ) ){
            return;
        }

        $terms_selected_on_course = wp_get_object_terms( $course_id, 'module' );

        if( empty( $terms_selected_on_course ) ){
            return;
        }

        foreach( $terms_selected_on_course as $term ){

            $term_author = Sensei_Core_Modules::get_term_author( $term->slug );
            if( $new_teacher_id != $term_author->ID  ){

                $new_term = '';

                //if the new teacher is admin first check to see if the term with this name already exists
                if( user_can( $new_teacher_id, 'manage_options' ) ){

                    $slug_without_teacher_id = str_ireplace(' ', '-', trim( $term->name ) );
                    $term_args = array( 'slug'=> $slug_without_teacher_id, 'hide_empty' => false, );
                    $existing_admin_terms = get_terms( 'module', $term_args );
                    if( !empty( $existing_admin_terms ) ){
                        // insert it even if it exists
                        $new_term = get_term( $existing_admin_terms[0]->term_id, 'module', ARRAY_A );
                    }
                }

                if( empty ( $new_term ) ){

                   //setup the new slug
                   $new_author_term_slug =  $new_teacher_id . '-' . str_ireplace(' ', '-', trim( $term->name ) );

                   // create new term and set it
                   $new_term = wp_insert_term( $term->name,'module', array('slug'=> $new_author_term_slug )  );

                }



                // if term exists
                if( is_wp_error( $new_term ) && isset( $new_term->errors['term_exists'] ) ){

                    $existing_term = get_term_by( 'slug', $new_author_term_slug, 'module');
                    $term_id = $existing_term->term_id;

                }else{

                    // for a new term simply get the term from the returned value
                    $term_id = $new_term['term_id'];

                } // end if term exist

                // set the terms selected on the course
                wp_set_object_terms( $course_id, $term_id , 'module', true );

                // remove old term
                wp_remove_object_terms( $course_id, $term->term_id, 'module' );

                // update the lessons within the current module term
                $lessons = Sensei()->course->course_lessons( $course_id );
                foreach( $lessons as $lesson  ){

                    if( has_term( $term->slug, 'module', $lesson ) ){

                        // add the new term, the false at the end says to replace all terms on this module
                        // with the new term.
                        wp_set_object_terms( $lesson->ID, $term_id , 'module', false );
                        update_post_meta( $lesson->ID, '_order_module_' . intval( $term_id ), 0 );
                    }

                }// end for each

            }
        }

    }// end update_course_module_terms_author

    /**
     * Sensei_Teacher::update_course_lessons_author
     *
     * Update all course lessons and their quiz with a new author
     *
     * @since 1.8.0
     * @access public
     * @parameters
     * @return array $users user id array
     */
    public function update_course_lessons_author ( $course_id, $new_author  ){


        if( empty( $course_id ) || empty( $new_author ) ){
            return false;
        }

        //get a list of course lessons
        $lessons = Sensei()->course->course_lessons( $course_id );

        if( empty( $lessons )  ||  ! is_array( $lessons )  ){
            return false;
        }

        // update each lesson and quiz author
        foreach( $lessons as $lesson ){

            // don't update if the author is tha same as the new author
            if( $new_author == $lesson->post_author ){
                continue;
            }

            // update lesson author
            wp_update_post( array(
                'ID'=> $lesson->ID,
                'post_author' => $new_author
                ) );

            // update quiz author
            //get the lessons quiz
            $lesson_quizzes = Sensei()->lesson->lesson_quizzes( $lesson->ID );
            if( is_array( $lesson_quizzes ) ){
                foreach ( $lesson_quizzes as $quiz_id ) {
                    // update quiz with new author
                    wp_update_post( array(
                        'ID'           => $quiz_id,
                        'post_author' =>  $new_author
                    ) );
                }
            }else{
                wp_update_post( array(
                    'ID'           => $lesson_quizzes,
                    'post_author' =>  $new_author
                ) );
            }

        } // end for each lessons

        return true;

    }// end update_course_lessons_author



    /**
     * Sensei_Teacher::course_analysis_teacher_access_limit
     *
     * Alter the query so that users can only see their courses on the analysis page
     *
     * @since 1.8.0
     * @access public
     * @parameters $query
     * @return array $users user id array
     */
    public function course_analysis_teacher_access_limit ( $query ) {

        if( ! is_admin() || ( defined( 'DOING_AJAX' ) && DOING_AJAX ) ) {
            return $query;
        }

        if ( ! function_exists( 'get_current_screen' ) ) {
            return $query;
        }

        $screen = get_current_screen();
        $sensei_post_types = array('course', 'lesson', 'question' );

        // exit early for the following conditions
        $limit_screen_ids = array( 'sensei_page_sensei_analysis', 'course_page_module-order' );

        if( ! $this->is_admin_teacher() || empty( $screen ) || ! in_array( $screen->id ,$limit_screen_ids )
            || ! in_array( $query->query['post_type'], $sensei_post_types ) ){
            return $query;
        }

        global $current_user;
        // set the query author to the current user to only show those those posts
        $query->set( 'author', $current_user->ID );
        return $query;

    }// end course_analysis_teacher_access_limit


    /**
     * Sensei_Teacher::limit_teacher_edit_screen_post_types
     *
     * Determine if we're in admin and the current logged in use is a teacher
     *
     * @since 1.8.0
     * @access public
     * @parameters array $wp_query
     * @return bool $is_admin_teacher
     */
    public function is_admin_teacher ( ){

        if( ! is_user_logged_in()){
            return false;
        }
        $is_admin_teacher = false;

        if( is_admin() && Sensei_Teacher::is_a_teacher( get_current_user_id() )  ){

            $is_admin_teacher = true;

        }

        return $is_admin_teacher;

    } // end is_admin_teacher

    /**
     * Show correct post counts on list table for Sensei post types
     *
     * @since 1.8.0
     *
     * @param  object $counts Default status counts
     * @param  string $type   Current post type
     * @param  string $perm   User permission level
     * @return object         Modified status counts
     */
    public function list_table_counts( $counts, $type, $perm ) {
        global $current_user;

        if( ! in_array( $type, array( 'course', 'lesson', 'question' ) ) ) {
            return $counts;
        }

        if( ! $this->is_admin_teacher() ) {
            return $counts;
        }

        $args = array(
            'post_type' => $type,
            'author' => $current_user->ID,
            'posts_per_page' => -1
        );

         // Get all available statuses
        $stati = get_post_stati();

        // Update count object
        foreach( $stati as $status ) {
            $args['post_status'] = $status;
            $posts = get_posts( $args );
            $counts->$status = count( $posts );
        }

        return $counts;
    }

    /**
     * Filter the post queries to show
     * only lesson /course and users that belong
     * to the current logged teacher.
     *
     * @since 1.8.0
     *
     */
    public function filter_queries ( $query ) {
        global $current_user;

        if( ! $this->is_admin_teacher() ) {
            return;
        }

        if ( ! function_exists( 'get_current_screen' ) ) {
            return;
        }

        $screen = get_current_screen();
        if( empty( $screen ) ) {
            return $query;
        }
        switch( $screen->id ) {
            case 'sensei_page_sensei_grading':
            case 'sensei_page_sensei_analysis':
            case 'sensei_page_sensei_learners':
            case 'lesson':
            case 'course':
            case 'question':
            case 'lesson_page_module-order':

            /**
             * sensei_filter_queries_set_author
             * Filter the author Sensei set for queries
             *
             * @since 1.8.0
             *
             * @param int $user_id
             * @param string $screen_id
             *
             */
            $query->set( 'author', apply_filters( 'sensei_filter_queries_set_author', $current_user->ID, $screen->id ) );
            break;
        }
    }

    /**
     * Limit grading quizzes to only those within courses belonging to the current teacher
     * . This excludes the admin user.
     *
     * @since 1.8.0
     * @hooked into the_comments
     * @param array  $comments
     *
     * @return array $comments
     */
    public function filter_grading_activity_queries( $comments ){

        if( !is_admin() || ! $this->is_admin_teacher() || is_numeric( $comments ) || ! is_array( $comments ) ){
            return $comments ;
        }

        //check if we're on the grading screen
        $screen = get_current_screen();

        if( empty( $screen ) || 'sensei_page_sensei_grading' != $screen->id ){
            return $comments;
        }

        // get the course and determine if the current teacher is the owner
        // if not remove it from the list of comments to be returned
        foreach( $comments as $key => $comment){
            $lesson = get_post( $comment->comment_post_ID );
            $course_id = Sensei()->lesson->get_course_id( $lesson->ID );
            $course = get_post( $course_id );
            if( ! isset( $course->post_author ) || intval( $course->post_author) != intval( get_current_user_id() ) ){
                //remove this as the teacher should see this.
                unset( $comments[ $key ] );
            }
        }
        return $comments ;

    }// end function filter grading

    /**
     * Limit the grading screen totals to only show lessons in the course
     * belonging to the currently logged in teacher. This only applies to
     * the teacher role.
     *
     * @since 1.8.0
     *
     * @hooked into sensei_count_statuses_args
     * @param array $args
     *
     * @return array  $args
     */
    public function limit_grading_totals( $args ){

        if( !is_admin() || ! $this->is_admin_teacher() || ! is_array( $args ) ){
            return $args ;
        }

        //get the teachers courses
        // the query is already filtered to only the teacher
        $courses =  Sensei()->course->get_all_courses();

        if( empty(  $courses ) || ! is_array( $courses ) ){
            return $args;
        }

        //setup the lessons quizzes  to limit the grading totals to
        $quiz_scope = array();
        foreach( $courses as $course ){

            $course_lessons = Sensei()->course->course_lessons( $course->ID );

            if( ! empty( $course_lessons ) && is_array( $course_lessons  ) ){

                foreach(  $course_lessons as $lesson ){

                    $quiz_id = Sensei()->lesson->lesson_quizzes( $lesson->ID );
                    if( !empty( $quiz_id ) ) {

                        array_push( $quiz_scope, $quiz_id );

                    }

                }

            }

        }

        $args['post__in'] = $quiz_scope;

        return $args;
    }

    /**
     * It ensures that the author archive shows course by the current user.
     *
     * This function is hooked into the pre_get_posts filter
     *
     * @param WP_Query $query
     * @return WP_Query $query
     */
    public function add_courses_to_author_archive( $query ) {

        if ( is_admin() || ! $query->is_author() ){
            return $query;
        }

        // this should only apply to users with the teacher role
        $current_page_user = get_user_by('login', $query->get('author_name') );
        if( ! $current_page_user || ! in_array('teacher', $current_page_user->roles ) )     {

            return $query;

        }

        // Change post types depending on what is set already
        $current_post_types = $query->get( 'post_type' );
        if( empty( $current_post_types  ) ){

            // if empty it means post by default, so add post so that it also includes that for now
            $new_post_types = array( 'post', 'course' );

        } elseif( is_array( $current_post_types  ) ) {

            // merge the post types instead of overwriting it
            $new_post_types = array_merge( $current_post_types, array( 'course' ) );

        }else{

            // in this instance it is probably just one post type in string format
            $new_post_types =  array( $current_post_types , 'course');

        }

        // change the query before returning it
        $query->set('post_type', $new_post_types );

        /**
         * Change the query on the teacher author archive template
         *
         * @since 1.8.4
         * @param WP_Query $query
         */
        return apply_filters( 'sensei_teacher_archive_query', $query );

    }

    /**
     * Notify teacher when someone assigns a course to their account.
     *
     * @since 1.8.0
     *
     * @param $teacher_id
     * @param $course_id
     * @return bool
     */
    public function teacher_course_assigned_notification( $teacher_id, $course_id ){

        if( 'course' != get_post_type( $course_id ) || ! get_userdata( $teacher_id ) ){
            return false;
        }

        // if new user is the same as the current logged user, they don't need an email
        if( $teacher_id == get_current_user_id() ){
            return true;
        }

        // load the email class
        include('emails/class-sensei-email-teacher-new-course-assignment.php');
        $email = new Sensei_Email_Teacher_New_Course_Assignment();
        $email->trigger( $teacher_id, $course_id );

        return true;
    } // end  teacher_course_assigned_notification

    /**
     * Email the admin when a teacher creates a new course
     *
     * This function hooks into wp_insert_post
     *
     * @since 1.8.0
     * @param int $course_id
     * @return bool
     */
    public function notify_admin_teacher_course_creation( $new_status, $old_status, $post ){

        $course_id = $post->ID;

        if( 'publish'== $old_status || 'course' != get_post_type( $course_id ) || 'auto-draft' == get_post_status( $course_id )
            || 'trash' == get_post_status( $course_id ) || 'draft' == get_post_status( $course_id ) ) {

            return false;

        }

        /**
         * Filter the option to send admin notification emails when teachers creation
         * course.
         *
         * @since 1.8.0
         *
         * @param bool $on default true
         */
        if( ! apply_filters('sensei_notify_admin_new_course_creation', true ) ){
            return false;
        }

        // setting up the data needed by the email template
        global $sensei_email_data;
        $template = 'admin-teacher-new-course-created';
        $course = get_post( $course_id );
        $teacher = new WP_User( $course->post_author );
        $recipient = get_option('admin_email', true);

        // don't send if the course is created by admin
        if( $recipient == $teacher->user_email || current_user_can( 'manage_options' )){
            return false;
        }

        /**
         * Filter the email Header for the admin-teacher-new-course-created template
         *
         * @since 1.8.0
         * @param string $template
         */
        $heading = apply_filters( 'sensei_email_heading', __( 'New course created.', 'woothemes-sensei' ), $template );

        /**
         * Filter the email subject for the the
         * admin-teacher-new-course-created template
         *
         * @since 1.8.0
         * @param string $subject default New course assigned to you
         * @param string $template
         */
        $subject = apply_filters('sensei_email_subject',
                                '['. get_bloginfo( 'name', 'display' ) .'] '. __( 'New course created by', 'woothemes-sensei' ) . ' ' . $teacher->display_name ,
                                $template );

        //course edit link
        $course_edit_link = admin_url('post.php?post=' . $course_id . '&action=edit' );

        // Construct data array
        $email_data = array(
            'template'			=> $template,
            'heading' =>  $heading,
            'teacher'		=> $teacher,
            'course_id'			=> $course_id,
            'course_name'			=> $course->post_title,
            'course_edit_link' => $course_edit_link,
        );

        /**
         * Filter the sensei email data for the admin-teacher-new-course-created template
         *
         * @since 1.8.0
         * @param array $email_data
         * @param string $template
         */
        $sensei_email_data = apply_filters( 'sensei_email_data', $email_data , $template );

        // Send mail
        Sensei()->emails->send( $recipient, $subject , Sensei()->emails->get_content( $template ) );

    }// end notify admin of course creation

    /**
     * Limit the analysis view to only the users taking courses belong to this teacher
     *
     * Hooked into sensei_analysis_get_learners
     * @param array $args WP_User_Query arguments
     * @return array $learners_query_results
     */
    public function limit_analysis_learners( $args ){

        // show default for none teachers
        if( ! Sensei()->teacher->is_admin_teacher() ) {
                return $args;
        }

        // for teachers all courses only return those which belong to the teacher
        // as they don't have access to course belonging to other users
        $teacher_courses = Sensei()->course->get_all_courses();

        // if the user has no courses they should see no users
        if( empty( $teacher_courses ) ||  ! is_array( $teacher_courses ) ){
            // tell the query to return 0 students
            $args[ 'include'] = array( 0 );
            return $args;

        }

        $learner_ids_for_teacher_courses = array();
        foreach( $teacher_courses as $course ){

            $course_learner_ids = array();
            $activity_comments =  Sensei_Utils::sensei_check_for_activity( array( 'post_id' => $course->ID, 'type' => 'sensei_course_status', 'field' => 'user_id' ), true );

            if( empty( $activity_comments ) ||  ( is_array( $activity_comments  ) && ! ( count( $activity_comments ) > 0 ) ) ){
                continue; // skip to the next course as there are no users on this course
            }

            // it could be an array of comments or a single comment
            if( is_array( $activity_comments ) ){

                foreach( $activity_comments as $comment ){

                    $user = get_userdata( $comment->user_id );

                    if( empty( $user ) ){
                        // next comment in this array
                        continue;
                    }

                    $course_learner_ids[] = $user->ID;
                }

            }else{

                $user = get_userdata( $activity_comments->user_id );
                $course_learner_ids[] = $user->ID;

            }

            // add learners on this course to the all courses learner list
            $learner_ids_for_teacher_courses = array_merge( $learner_ids_for_teacher_courses, $course_learner_ids );

        }

        // if there are no students taking the courses by this teacher don't show them any of the other users
        if( empty( $learner_ids_for_teacher_courses ) ){

            $args[ 'include'] = array( 0 );

        }else{

            $args[ 'include'] = $learner_ids_for_teacher_courses;

        }

        // return the WP_Use_Query arguments
        return $args;

    }// end limit_analysis_learners

    /**
     * Give teacher full admin access to the question post type
     * in certain cases.
     *
     * @since 1.8.0
     * @param $questions
     * @return mixed
     */
    public function allow_teacher_access_to_questions( $questions, $quiz_id ){

        if( ! $this->is_admin_teacher() ){
            return $questions;
        }

        $screen = get_current_screen();

        // don't run this filter within this functions call to Sensei()->lesson->lesson_quiz_questions
        remove_filter( 'sensei_lesson_quiz_questions', array( $this, 'allow_teacher_access_to_questions' ), 20 );

        if( ! empty( $screen ) && 'lesson'== $screen->post_type ){

            $admin_user = get_user_by('email', get_bloginfo('admin_email'));
            if( ! empty($admin_user) ){

                $current_teacher_id = get_current_user_id();

                // set current user to admin so teacher can view all questions
                wp_set_current_user( $admin_user->ID  );
                $questions = Sensei()->lesson->lesson_quiz_questions( $quiz_id  );

                // set the teacher as the current use again
                wp_set_current_user( $current_teacher_id );
            }

        }
        // attach the filter again for other funtion calls to Sensei()->lesson->lesson_quiz_questions
        add_filter( 'sensei_lesson_quiz_questions', array( $this, 'allow_teacher_access_to_questions' ), 20,2 );

        return $questions;
    }

    /**
     * Give the teacher role access to questions from the question bank
     *
     * @since 1.8.0
     * @param $wp_query
     * @return mixed
     */
    public function give_access_to_all_questions( $wp_query ){

        if( ! $this->is_admin_teacher() || !function_exists( 'get_current_screen') || 'question' != $wp_query->get('post_type') ){

            return $wp_query;
        }

        $screen = get_current_screen();
        if( ( isset($screen->id) && 'lesson' == $screen->id )
            || ( defined( 'DOING_AJAX' ) && DOING_AJAX ) ){

            $admin_user = get_user_by('email', get_bloginfo('admin_email'));
            if( ! empty($admin_user) ){

                $current_teacher_id = get_current_user_id();

                // set current user to admin so teacher can view all questions
                wp_set_current_user( $admin_user->ID  );

                //run new query as admin
                $wp_query = new WP_Query( $wp_query->query );

                //set the teache as current use again
                wp_set_current_user( $current_teacher_id );

            }
        }

        return $wp_query;
    }// end give_access_to_all_questions

    /**
     * Add new column heading to the course admin edit list
     *
     * @since 1.8.0
     * @param $columns
     * @return array
     */
    public function course_column_heading($columns) {

        if( $this->is_admin_teacher() ){
            return $columns;
        }
        $new_columns = array(
            'teacher' => __('Teacher', 'woothemes-sensei'),
        );
        return array_merge($columns, $new_columns);

    }// end teacher column add

    /**
     * Print out  teacher column data
     *
     * @since 1.8.0
     * @param $column
     * @param $course_id
     */
    public function course_column_data( $column, $course_id  ){

        if( $this->is_admin_teacher() || 'teacher' != $column  ){
            return;
        }

        $course = get_post( $course_id );
        $teacher = get_userdata( $course->post_author );

        if( !$teacher ){
            return;
        }

        echo '<a href="'. get_edit_user_link( $teacher->ID ) .'" >'. $teacher->display_name.'</a>';

    }// end course_column_ data

    /**
     * Return only courses belonging to the given teacher.
     *
     *
     * @since 1.8.0
     *
     * @param int $teacher_id
     * @param bool $return_ids_only
     *
     * @return array $teachers_courses
     */
    public function get_teacher_courses( $teacher_id, $return_ids_only= false){

        $teachers_courses = array();

        if( empty( $teacher_id  ) ){
            $teacher_id = get_current_user_id();
        }

        $all_courses = Sensei()->course->get_all_courses();

        if( empty( $all_courses ) ){
            return $all_courses;
        }

        foreach( $all_courses as $course ){

            if( $course->post_author != $teacher_id  ){
                continue;
            }

            if( $return_ids_only ){

                $teachers_courses[] = $course->ID;

            }else{

                $teachers_courses[] = $course;

            }

        }

        return $teachers_courses;

    }

    /**
     * Limit the message display to only those sent to the current teacher
     *
     * @since 1.8.0
     *
     * @param $query
     * @return mixed
     */
    public function limit_edit_messages_query( $query ){
        if( ! $this->is_admin_teacher() || 'sensei_message' != $query->get('post_type') ){
            return $query;
        }

        $teacher = wp_get_current_user();

        $query->set( 'meta_key', '_receiver' );
        $meta_query_args = array(
            'key'     => '_receiver',
            'value'   => $teacher->get('user_login') ,
            'compare' => '='
        );

        $query->set('meta_query', $meta_query_args  );

        return $query;
    }


    /**
     * Add options to filter courses by teacher
     *
     * @since 1.8.0
     *
     * @return void
     */
    public function course_teacher_filter_options() {
        global $typenow;

        if( ! is_admin() || 'course' != $typenow || ! current_user_can('manage_sensei') ) {
            return;
        }

        // get all roles
        $roles = get_editable_roles();

        // get roles with the course edit capability
        // and then get the users with those roles
        $users_who_can_edit_courses = array();
        foreach( $roles as $role_item ){

            $role = get_role( strtolower( $role_item['name'] ) );

            if( is_a( $role, 'WP_Role' ) && $role->has_cap('edit_courses') ){

                $user_query_args = array( 'role' => $role->name, 'fields' => array( 'ID', 'display_name' ) );
                $role_users_who_can_edit_courses = get_users( $user_query_args );

                // add user from the current $user_role to all users
                $users_who_can_edit_courses = array_merge( $users_who_can_edit_courses, $role_users_who_can_edit_courses );

            }

        }

        // Create the select element with the given users who can edit course
        $selected = isset( $_GET['course_teacher'] ) ? $_GET['course_teacher'] : '';
        $course_options = '';
        foreach( $users_who_can_edit_courses as $user ) {
            $course_options .= '<option value="' . esc_attr( $user->ID ) . '" ' . selected( $selected, $user->ID, false ) . '>' .  $user->display_name . '</option>';
        }

        $output = '<select name="course_teacher" id="dropdown_course_teachers">';
        $output .= '<option value="">'.__( 'Show all teachers', 'woothemes-sensei' ).'</option>';
        $output .= $course_options;
        $output .= '</select>';

        echo $output;
    }

    /**
     * Modify the main query on the admin course list screen
     *
     * @since 1.8.0
     *
     * @param $query
     * @return $query

The doc-type $query could not be parsed: Unknown type name "$query" at position 0. (view supported doc-types)

     */
    public function teacher_filter_query_modify( $query ){
        global $typenow;

        if( ! is_admin() && 'course' != $typenow  || ! current_user_can('manage_sensei')  ) {
            return $query;
        }
        $course_teacher = isset( $_GET['course_teacher'] ) ? $_GET['course_teacher'] : '';

        if( empty( $course_teacher ) ) {
            return $query;
        }

        $query['author'] = $course_teacher;
        return $query;
    }

    /**
     * Only show current teacher's media in the media library
     * @param  array $request Default request arguments
     * @return array          Modified request arguments
     */
    public function restrict_media_library( $request = array() ) {

        if( ! is_admin() ) {
            return $request;
        }

        if( ! $this->is_admin_teacher() ) {
            return $request;
        }

        $screen = get_current_screen();

        if( in_array( $screen->id, array( 'upload', 'course', 'lesson', 'question' ) ) ) {
            $teacher = intval( get_current_user_id() );

            if( $teacher ) {
                $request['author__in'] = array( $teacher );
            }
        }

        return $request;
    } // End restrict_media_library()

    /**
     * Only show current teacher's media in the media library modal on the course/lesson/quesion edit screen
     * @param  array $query Default query arguments
     * @return array        Modified query arguments
     */
    public function restrict_media_library_modal( $query = array() ) {

        if( ! is_admin() ) {
            return $query;
        }

        if( ! $this->is_admin_teacher() ) {
            return $query;
        }

        $teacher = intval( get_current_user_id() );

        if( $teacher ) {
            $query['author__in'] = array( $teacher );
        }

        return $query;
    } // End restrict_media_library_modal()

    /**
     * When saving the lesson, update the teacher if the lesson belongs to a course
     *
     * @since 1.8.0
     *
     * @param int $lesson_id
     */
    public function update_lesson_teacher( $lesson_id ){

        if( 'lesson'!= get_post_type() ){
            return;
        }

        // this should only run once per request cycle
        remove_action( 'save_post',  array( $this, 'update_lesson_teacher' ) );

        $course_id = Sensei()->lesson->get_course_id( $lesson_id );

        if(  empty( $course_id ) || ! $course_id ){
            return;
        }

        $course = get_post( $course_id );

        $lesson_update_args= array(
            'ID' => $lesson_id ,
            'post_author' => $course->post_author
        );
        wp_update_post( $lesson_update_args );

    } // end update_lesson_teacher

    /**
     * Sensei_Teacher::limit_teacher_edit_screen_post_types
     *
     * Limit teachers to only see their courses, lessons and questions
     *
     * @since 1.8.0
     * @access public
     * @parameters array $wp_query
     * @return WP_Query $wp_query
     */
    public function limit_teacher_edit_screen_post_types( $wp_query ) {
        global $current_user;

        //exit early
        if( ! $this->is_admin_teacher() ){
            return $wp_query;
        }

        if ( ! function_exists( 'get_current_screen' ) ) {
            return $wp_query;
        }

        $screen = get_current_screen();

        if( empty( $screen ) ){
            return $wp_query;
        }

        // for any of these conditions limit what the teacher will see
        $limit_screens = array(
            'edit-lesson',
            'edit-course',
            'edit-question',
            'course_page_course-order',
            'lesson_page_lesson-order',
        );

        if(  in_array($screen->id  , $limit_screens ) ) {

            // set the query author to the current user to only show those those posts
            $wp_query->set( 'author', $current_user->ID );
        }

        return $wp_query;

    } // end limit_teacher_edit_screen_post_types()


    /**
     * Sensei_Teacher::teacher_login_redirect
     *
     * Redirect teachers to /wp-admin/ after login
     *
     * @since 1.8.7
     * @access public
     * @param string $user_login
     * @param object $user
     * @return void
     */

    public function teacher_login_redirect( $user_login, $user  ) {

        if (user_can($user, 'edit_courses')) {

            if (isset($_POST['redirect_to'])) {

                wp_redirect($_POST['redirect_to'], 303);

                exit;

            } else {

                wp_redirect(admin_url(), 303);

                exit;

            }
        }

    } // end teacher_login_redirect()



    /**
     * Sensei_Teacher::restrict_posts_menu_page()
     *
     * Remove the Posts menu page for teachers and restrict access to it.
     * We have to do this because we give teachers the 'edit_posts' cap
     * so they can 'moderate_comments' as well.
     *
     * @since 1.8.7
     * @access public
     * @parameters void
     * @return void
     */

    public function restrict_posts_menu_page() {

        global $pagenow, $typenow;

        $user = wp_get_current_user();

        /**
         * Filter the option to hide the Posts menu page.
         *
         * @since 1.8.7
         *
         * @param bool $restrict default true
         */

        $restrict = apply_filters('sensei_restrict_posts_menu_page', true );

        if ( in_array( 'teacher', (array) $user->roles ) && !current_user_can('delete_posts') && $restrict) {

            remove_menu_page('edit.php');

            if ($pagenow == "edit.php" || $pagenow == "post-new.php") {

                if ($typenow == '' || $typenow == 'post' || $typenow == 'page') {

                    wp_die('You do not have sufficient permissions to access this page.');

                }

            }

        }

    } // end restrict_posts_menu_page()

    /**
     * Sensei_Teacher::restrict_comment_moderation()
     *
     * Restrict commendation moderation for teachers
     * so they can only moderate comments made to posts they own.
     *
     * @since 1.8.7
     * @access public
     * @parameters obj $clauses
     * @return WP_Comment_Query  $clauses
     */

    public function restrict_comment_moderation ( $clauses ) {

        global $pagenow;

        if( self::is_a_teacher( get_current_user_id() ) && $pagenow == "edit-comments.php") {

            $clauses->query_vars['post_author'] = get_current_user_id();

        }

        return $clauses;

    }   // end restrict_comment_moderation()

    /**
     * Determine if a user is a teacher by ID
     *
     * @param int $user_id
     *
     * @return bool
     */
    public static function is_a_teacher( $user_id ){

        $user = get_user_by('id', $user_id);

        if( isset( $user->roles ) && in_array(  'teacher',  $user->roles )   ){

            return true;

        }else{

            return false;

        }

    }// end is_a_teacher

    /**
     * The archive title on the teacher archive filter
     *
     * @since 1.9.0
     */
    public static function archive_title(){

        $author = get_user_by( 'id', get_query_var( 'author' ) );
        $author_name = $author->display_name;
        ?>
            <h2 class="teacher-archive-title">

                <?php echo sprintf( __( 'All courses by %s', 'woothemes-sensei') , $author_name ); ?>

            </h2>
        <?php

    }// archive title

    /**
     * Removing course meta on the teacher archive page
     *
     * @since 1.9.0
     */
    public static function remove_course_meta_on_teacher_archive(){

        remove_action('sensei_course_content_inside_before', array( Sensei()->course, 'the_course_meta' ) );

    }

} // End Class