locallib.php

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
/**
 * @package   mod_pdfannotator
 * @copyright 2018 RWTH Aachen (see README)
 * @author    Rabea de Groot, Anna Heynkes, Friederike Schwager
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

use mod_pdfannotator\output\answermenu;
use mod_pdfannotator\output\questionmenu;
use mod_pdfannotator\output\reportmenu;
use mod_pdfannotator\output\index;

defined('MOODLE_INTERNAL') || die;

require_once("$CFG->libdir/filelib.php");
require_once("$CFG->libdir/resourcelib.php");
require_once("$CFG->dirroot/mod/pdfannotator/lib.php");

/**
 * Display embedded pdfannotator file.
 * @param object $pdfannotator
 * @param object $cm
 * @param object $course
 * @param stored_file $file main file
 * @return does not return
 */
function pdfannotator_display_embed($pdfannotator, $cm, $course, $file, $page = 1, $annoid = null, $commid = null) {
    global $CFG, $PAGE, $OUTPUT, $USER;

    // The revision attribute's existance is demanded by moodle for versioning and could be saved in the pdfannotator table in the future.
    // Note, however, that we forbid file replacement in order to prevent a change of meaning in other people's comments.
    $pdfannotator->revision = 1;

    $context = context_module::instance($cm->id);
    $path = '/' . $context->id . '/mod_pdfannotator/content/' . $pdfannotator->revision . $file->get_filepath() . $file->get_filename();
    $fullurl = file_encode_url($CFG->wwwroot . '/pluginfile.php', $path, false);

    $documentobject = new stdClass();
    $documentobject->annotatorid = $pdfannotator->id;
    $documentobject->fullurl = $fullurl;

    $stringman = get_string_manager();
    // With this method you get the strings of the language-Files.
    $strings = $stringman->load_component_strings('pdfannotator', 'en');
    // Method to use the language-strings in javascript.
    $PAGE->requires->strings_for_js(array_keys($strings), 'pdfannotator');
    // Load and execute the javascript files.
    $PAGE->requires->js(new moodle_url("/mod/pdfannotator/shared/pdf.js"));
    $PAGE->requires->js(new moodle_url("/mod/pdfannotator/shared/pdf_viewer.js"));
    $PAGE->requires->js(new moodle_url("/mod/pdfannotator/shared/textclipper.js"));
    $PAGE->requires->js(new moodle_url("/mod/pdfannotator/shared/index.js?ver=00014"));
    $PAGE->requires->js(new moodle_url("/mod/pdfannotator/shared/locallib.js?ver=00003"));

    // Pass parameters from PHP to JavaScript.

    // 1. Toolbar settings.
    $toolbarsettings = new stdClass();
    $toolbarsettings->use_studenttextbox = $pdfannotator->use_studenttextbox;
    $toolbarsettings->use_studentdrawing = $pdfannotator->use_studentdrawing;
    $toolbarsettings->useprint = $pdfannotator->useprint;
    $toolbarsettings->useprintcomments = $pdfannotator->useprintcomments;
    // 2. Capabilities.
    $capabilities = new stdClass();
    $capabilities->viewquestions = has_capability('mod/pdfannotator:viewquestions', $context);
    $capabilities->viewanswers = has_capability('mod/pdfannotator:viewanswers', $context);
    $capabilities->viewposts = has_capability('mod/pdfannotator:viewposts', $context);
    $capabilities->viewreports = has_capability('mod/pdfannotator:viewreports', $context);
    $capabilities->deleteany = has_capability('mod/pdfannotator:deleteany', $context);
    $capabilities->hidecomment = has_capability('mod/pdfannotator:hidecomments', $context);
    $capabilities->seehiddencomments = has_capability('mod/pdfannotator:seehiddencomments', $context);
    $capabilities->usetextbox = has_capability('mod/pdfannotator:usetextbox', $context);
    $capabilities->usedrawing = has_capability('mod/pdfannotator:usedrawing', $context);
    $capabilities->useprint = has_capability('mod/pdfannotator:printdocument', $context);
    $capabilities->useprintcomments = has_capability('mod/pdfannotator:printcomments', $context);

    $params = [$cm, $documentobject, $USER->id, $capabilities, $toolbarsettings, $page, $annoid, $commid];
    $PAGE->requires->js_init_call('adjustPdfannotatorNavbar', null, true);
    $PAGE->requires->js_init_call('startIndex', $params, true);
    // The renderer renders the original index.php / takes the template and renders it.
    $myrenderer = $PAGE->get_renderer('mod_pdfannotator');
    echo $myrenderer->render_index(new index($pdfannotator, $capabilities, $file));
    $PAGE->requires->js_init_call('checkOnlyOneCheckbox', null, true);

    pdfannotator_print_intro($pdfannotator, $cm, $course);

    echo $OUTPUT->footer();
    die;
}

function pdfannotator_get_instance_name($id) {

    global $DB;
    return $DB->get_field('pdfannotator', 'name', array('id' => $id), $strictness = MUST_EXIST);
}

function pdfannotator_get_course_name_by_id($courseid) {
    global $DB;
    return $DB->get_field('course', 'fullname', array('id' => $courseid), $strictness = MUST_EXIST);
}

function pdfannotator_get_username($userid) {
    global $DB;
    $user = $DB->get_record('user', array('id' => $userid));
    return fullname($user);
}

function pdfannotator_get_annotationtype_id($typename) {
    global $DB;
    if ($typename == 'point') {
        $typename = 'pin';
    }
    $result = $DB->get_records('pdfannotator_annotationtypes', array('name' => $typename));
    foreach ($result as $r) {
        return $r->id;
    }
}

function pdfannotator_get_annotationtype_name($typeid) {
    global $DB;
    $result = $DB->get_records('pdfannotator_annotationtypes', array('id' => $typeid));
    foreach ($result as $r) {
        return $r->name;
    }
}

function pdfannotator_handle_latex($context, string $subject) {
    global $CFG;
    require_once($CFG->dirroot . '/mod/pdfannotator/constants.php');
    $latexapi = get_config('mod_pdfannotator', 'latexapi');

    // Look for these formulae: $$ ... $$, \( ... \) and \[ ... \]
    // !!! keep indentation!
    $pattern = <<<'SIGN'
~(?:\$\$.*?\$\$)|(?:\\\(.*?\\\))|(?:\\\[.*?\\\])~
SIGN;

    $matches = array();
    $hits = preg_match_all($pattern, $subject, $matches, PREG_OFFSET_CAPTURE);

    if ($hits == 0) {
        return $subject;
    }

    $textstart = 0;
    $formulalength = 0;
    $formulaoffset = 0;
    $result = [];
    $matches = $matches[0];
    foreach ($matches as $match) {
        $formulalength = strlen($match[0]);
        $formulaoffset = $match[1];
        $string = $match[0];
        $string = str_replace('\xrightarrow', '\rightarrow', $string);
        $string = str_replace('\xlefttarrow', '\leftarrow', $string);

        $pos = strpos($string, '\\[');
        if ($pos !== false) {
            $string = substr_replace($string, '', $pos, strlen('\\['));
        }

        $pos = strpos($string, '\\(');
        if ($pos !== false) {
            $string = substr_replace($string, '', $pos, strlen('\\('));
        }

        $string = str_replace('\\]', '', $string);

        $string = str_replace('\\)', '', $string);

        $string = str_replace('\begin{aligned}', '', $string);
        $string = str_replace('\end{aligned}', '', $string);

        $string = str_replace('\begin{align*}', '', $string);
        $string = str_replace('\end{align*}', '', $string);

        // Find any backslash preceding a ( or [ and replace it with \backslash
        $pattern = '~\\\\(?=[\\\(\\\[])~';
        $string = preg_replace($pattern, '\\backslash', $string);
        $match[0] = $string;

        $result[] = trim(substr($subject, $textstart, $formulaoffset - $textstart));
        if ($latexapi == LATEX_TO_PNG_GOOGLE_API) {
            $result[] = pdfannotator_process_latex_google($match[0]);
        } else {
            $result[] = pdfannotator_process_latex_moodle($context, $match[0]);
        }
        $textstart = $formulaoffset + $formulalength;
    }
    if ($textstart != strlen($subject) - 1) {
        $result[] = trim(substr($subject, $textstart, strlen($subject) - $textstart));
    }
    return $result;
}

function pdfannotator_process_latex_moodle($context, $string) {
    global $CFG;
    require_once($CFG->libdir . '/moodlelib.php');
    require_once($CFG->dirroot . '/filter/tex/latex.php');
    require_once($CFG->dirroot . '/filter/tex/lib.php');
    $result = array();
    $tex = new latex();
    $md5 = md5($string);
    $image = $tex->render($string, $md5 . 'png');
    if ($image == false) {
        return false;
    }
    $imagedata = file_get_contents($image);
    $result['image'] = IMAGE_PREFIX . base64_encode($imagedata);
    // Imageinfo returns an array with the info of the size of the image. In Parameter 1 there is the height, which is the only
    // thing needed here.
    $imageinfo = getimagesize($image);
    $result['imageheight'] = $imageinfo[1];
    return $result;
}
/**
 * Function takes a latex code string, modifies and url encodes it for the Google Api to process,
 * and returns the resulting image along with its height
 *
 * @param type $string
 * @return type
 */
function pdfannotator_process_latex_google(string $string) {

    $length = strlen($string);
    $im = null;
    if ($length <= 200) { // Google API constraint XXX find better alternative if possible.
        $latexdata = urlencode($string);
        $requesturl = LATEX_TO_PNG_REQUEST . $latexdata;
        $im = @file_get_contents($requesturl); // '@' suppresses warnings so that one failed google request doesn't prevent the pdf from being printed,
        // but just the one formula from being presented as a picture.
    }
    if ($im != null) {
        $array = [];
        try {
            list($width, $height) = getimagesize($requesturl); // XXX alternative: acess height by decoding the string (saving the extra server request)?
            if ($height != null) {
                $imagedata = IMAGE_PREFIX . base64_encode($im); // Image.
                $array['image'] = $imagedata;
                $array['imageheight'] = $height;
                return $array;
            }
        } catch (Exception $ex) {
            return $string;
        }
    } else {
        return $string;
    }
}

function pdfannotator_send_forward_message($recipients, $messageparams, $course, $cm, $context) {
    $name = 'forwardedquestion';
    $text = new stdClass();
    $module = get_string('modulename', 'pdfannotator');
    $modulename = format_string($cm->name, true);
    $text->text = pdfannotator_format_notification_message_text($course, $cm, $context, $module, $modulename, $messageparams, $name);
    $text->url = $messageparams->urltoquestion;

    foreach ($recipients as $recipient) {
        $text->html = pdfannotator_format_notification_message_html($course, $cm, $context, $module, $modulename, $messageparams, $name, $recipient);
        pdfannotator_notify_manager($recipient, $course, $cm, $name, $text);
    }
}

function pdfannotator_notify_manager($recipient, $course, $cm, $name, $messagetext, $anonymous = false) {

    global $USER;
    $userfrom = $USER;
    $modulename = format_string($cm->name, true);
    if ($anonymous) {
        $userfrom = clone($USER);
        $userfrom->firstname = get_string('pdfannotatorname', 'pdfannotator') . ':';
        $userfrom->lastname = $modulename;
    }
    $message = new \core\message\message();
    $message->component = 'mod_pdfannotator';
    $message->name = $name;
    $message->courseid = $course->id;
    $message->userfrom = $userfrom;
    $message->userto = $recipient;
    $message->subject = get_string('notificationsubject:' . $name, 'pdfannotator', $modulename);
    $message->fullmessage = $messagetext->text;
    $message->fullmessageformat = FORMAT_PLAIN;
    $message->fullmessagehtml = $messagetext->html;
    $message->smallmessage = get_string('notificationsubject:' . $name, 'pdfannotator', $modulename);
    $message->notification = 1; // For personal messages '0'. Important: the 1 without '' and 0 with ''.
    $message->contexturl = $messagetext->url;
    $message->contexturlname = 'Context name';
    $content = array('*' => array('header' => ' test ', 'footer' => ' test ')); // Extra content for specific processor.

    $messageid = message_send($message);

    return $messageid;
}

function pdfannotator_format_notification_message_text($course, $cm, $context, $modulename, $pdfannotatorname, $paramsforlanguagestring, $messagetype) {
    global $CFG;
    $formatparams = array('context' => $context->get_course_context());
    $posttext = format_string($course->shortname, true, $formatparams) .
        ' -> ' .
        $modulename .
        ' -> ' .
        format_string($pdfannotatorname, true, $formatparams) . "\n";
    $posttext .= '---------------------------------------------------------------------' . "\n";
    $posttext .= "\n";
    $posttext .= get_string($messagetype . 'text', 'pdfannotator', $paramsforlanguagestring) . "\n---------------------------------------------------------------------\n";
    return $posttext;
}

/**
 * Format a notification for HTML.
 *
 * @param string $messagetype
 * @param stdClass $info
 * @param stdClass $course
 * @param stdClass $context
 * @param string $modulename
 * @param stdClass $coursemodule
 * @param string $assignmentname
 */
function pdfannotator_format_notification_message_html($course, $cm, $context, $modulename, $pdfannotatorname, $report, $messagetype, $recipientid) {
    global $CFG, $USER;
    $formatparams = array('context' => $context->get_course_context());
    $posthtml = '<p><font face="sans-serif">' .
        '<a href="' . $CFG->wwwroot . '/course/view.php?id=' . $course->id . '">' .
        format_string($course->shortname, true, $formatparams) .
        '</a> ->' .
        '<a href="' . $CFG->wwwroot . '/mod/pdfannotator/index.php?id=' . $course->id . '">' .
        $modulename .
        '</a> ->' .
        '<a href="' . $CFG->wwwroot . '/mod/pdfannotator/view.php?id=' . $cm->id . '">' .
        format_string($pdfannotatorname, true, $formatparams) .
        '</a></font></p>';
    $posthtml .= '<hr /><font face="sans-serif">';
    $report->urltoreport = $CFG->wwwroot . '/mod/pdfannotator/view.php?id=' . $cm->id . '&action=overviewreports';
    $posthtml .= '<p>' . get_string($messagetype . 'html', 'pdfannotator', $report) . '</p>';
    $linktonotificationsettingspage = new moodle_url('/message/notificationpreferences.php', array('userid' => $recipientid));
    $linktonotificationsettingspage = $linktonotificationsettingspage->__toString();
    $posthtml .= '</font><hr />';
    $posthtml .= '<font face="sans-serif"><p>' . get_string('unsubscribe_notification', 'pdfannotator', $linktonotificationsettingspage) . '</p></font>';
    return $posthtml;
}

/**
 * Internal function - create click to open text with link.
 */
function pdfannotator_get_clicktoopen($file, $revision, $extra = '') {
    global $CFG;

    $filename = $file->get_filename();
    $path = '/' . $file->get_contextid() . '/mod_pdfannotator/content/' . $revision . $file->get_filepath() . $file->get_filename();
    $fullurl = file_encode_url($CFG->wwwroot . '/pluginfile.php', $path, false);

    $string = get_string('clicktoopen2', 'pdfannotator', "<a href=\"$fullurl\" $extra>$filename</a>");

    return $string;
}

/**
 * Internal function - create click to open text with link.
 */
function pdfannotator_get_clicktodownload($file, $revision) {
    global $CFG;

    $filename = $file->get_filename();
    $path = '/' . $file->get_contextid() . '/mod_pdfannotator/content/' . $revision . $file->get_filepath() . $file->get_filename();
    $fullurl = file_encode_url($CFG->wwwroot . '/pluginfile.php', $path, true);

    $string = get_string('clicktodownload', 'pdfannotator', "<a href=\"$fullurl\">$filename</a>");

    return $string;
}

/**
 * Print pdfannotator header.
 * @param object $pdfannotator
 * @param object $cm
 * @param object $course
 * @return void
 */
function pdfannotator_print_header($pdfannotator, $cm, $course) {
    global $PAGE, $OUTPUT;
    $PAGE->set_title($course->shortname . ': ' . $pdfannotator->name);
    $PAGE->set_heading($course->fullname);
    $PAGE->set_activity_record($pdfannotator);
    echo $OUTPUT->header();
}

/**
 * Gets details of the file to cache in course cache to be displayed using {@see pdfannotator_get_optional_details()}
 *
 * @param object $pdfannotator pdfannotator table row (only property 'displayoptions' is used here)
 * @param object $cm Course-module table row
 * @return string Size and type or empty string if show options are not enabled
 */
function pdfannotator_get_file_details($pdfannotator, $cm) {
    $filedetails = array();

    $context = context_module::instance($cm->id);
    $fs = get_file_storage();
    $files = $fs->get_area_files($context->id, 'mod_pdfannotator', 'content', 0, 'sortorder DESC, id ASC', false);
    // For a typical file pdfannotator, the sortorder is 1 for the main file
    // and 0 for all other files. This sort approach is used just in case
    // there are situations where the file has a different sort order.
    $mainfile = $files ? reset($files) : null;

    foreach ($files as $file) {
        // This will also synchronize the file size for external files if needed.
        $filedetails['size'] += $file->get_filesize();
        if ($file->get_repository_id()) {
            // If file is a reference the 'size' attribute can not be cached.
            $filedetails['isref'] = true;
        }
    }

    return $filedetails;
}

/**
 * Print pdfannotator introduction.
 * @param object $pdfannotator
 * @param object $cm
 * @param object $course
 * @param bool $ignoresettings print even if not specified in modedit
 * @return void
 */
function pdfannotator_print_intro($pdfannotator, $cm, $course, $ignoresettings = false) {
    global $OUTPUT;
    if ($ignoresettings) {
        $gotintro = trim(strip_tags($pdfannotator->intro));
        if ($gotintro || $extraintro) {
            echo $OUTPUT->box_start('mod_introbox', 'pdfannotatorintro');
            if ($gotintro) {
                echo format_module_intro('pdfannotator', $pdfannotator, $cm->id);
            }
            echo $extraintro;
            echo $OUTPUT->box_end();
        }
    }
}

/**
 * Print warning that file can not be found.
 * @param object $pdfannotator
 * @param object $cm
 * @param object $course
 * @return void, does not return
 */
function pdfannotator_print_filenotfound($pdfannotator, $cm, $course) {
    global $DB, $OUTPUT;

    pdfannotator_print_header($pdfannotator, $cm, $course);
    // pdfannotator_print_heading($pdfannotator, $cm, $course);//TODO Method is not defined.
    pdfannotator_print_intro($pdfannotator, $cm, $course);
    echo $OUTPUT->notification(get_string('filenotfound', 'pdfannotator'));

    echo $OUTPUT->footer();
    die;
}

/**
 * Function returns the number of new comments, drawings and textboxes*
 * in this annotator. 'New' is defined here as 'no older than 24h' but
 * can easily be changed to another time span.
 * *Drawings and textboxes cannot be commented. In their case (only),
 * therefore, annotations are counted.
 *
 */
function pdfannotator_get_number_of_new_activities($annotatorid) {

    global $DB;

    $parameters = array();
    $parameters[] = $annotatorid;
    $parameters[] = strtotime("-1 day");

    $sql = "SELECT c.id FROM {pdfannotator_annotations} a JOIN {pdfannotator_comments} c ON c.annotationid = a.id "
        . "WHERE a.pdfannotatorid = ? AND c.timemodified >= ?";
    $sql2 = "SELECT a.id FROM {pdfannotator_annotations} a JOIN {pdfannotator_annotationtypes} t ON a.annotationtypeid = t.id "
        . "WHERE a.pdfannotatorid = ? AND a.timecreated >= ? AND t.name IN('drawing','textbox')";

    return ( count($DB->get_records_sql($sql, $parameters)) + count($DB->get_records_sql($sql2, $parameters)) );
}

/**
 * Function returns the datetime of the last modification on or in the specified annotator.
 * The modification can be the creation of the annotator, a change of title or description,
 * a new annotation or a new comment. Reports are not considered.
 *
 * @param int $annotatorid
 * @return datetime $timemodified
 * The timestamp can be transformed into a readable string with this moodle method:
 * userdate($timestamp, $format = '', $timezone = 99, $fixday = true, $fixhour = true);
 */
function pdfannotator_get_datetime_of_last_modification($annotatorid) {

    global $DB;

    // 1. When was the last time the annotator itself (i.e. its title, description or pdf) was modified?
    $timemodified = $DB->get_record('pdfannotator', array('id' => $annotatorid), 'timemodified', MUST_EXIST);
    $timemodified = $timemodified->timemodified;

    // 2. When was the last time an annotation or a comment was added in the specified annotator?
    $sql = "SELECT max(a.timecreated) AS last_annotation, max(c.timemodified) AS last_comment "
        . "FROM {pdfannotator_annotations} a LEFT OUTER JOIN {pdfannotator_comments} c ON a.id = c.annotationid "
        . "WHERE a.pdfannotatorid = ?";
    $newposts = $DB->get_records_sql($sql, array($annotatorid));

    if (!empty($newposts)) {

        foreach ($newposts as $entry) {

            // 2.a) If there is an annotation younger than the creation/modification of the annotator, set timemodified to the annotation time.
            if (!empty($entry->last_annotation) && ($entry->last_annotation > $timemodified)) {
                $timemodified = $entry->last_annotation;
            }
            // 2.b) If there is a comment younger than the creation/modification of the annotator or its newest annotation, set timemodified to the comment time.
            if (!empty($entry->last_comment) && ($entry->last_comment > $timemodified)) {
                $timemodified = $entry->last_comment;
            }
            return $timemodified;
        }
    }
}

/**
 * File browsing support class
 */
class pdfannotator_content_file_info extends file_info_stored {

    public function get_parent() {
        if ($this->lf->get_filepath() === '/' and $this->lf->get_filename() === '.') {
            return $this->browser->get_file_info($this->context);
        }
        return parent::get_parent();
    }

    public function get_visible_name() {
        if ($this->lf->get_filepath() === '/' and $this->lf->get_filename() === '.') {
            return $this->topvisiblename;
        }
        return parent::get_visible_name();
    }

}

function pdfannotator_set_mainfile($data) {
    global $DB;
    $fs = get_file_storage();
    $cmid = $data->coursemodule;
    $draftitemid = $data->files; // Name from the filemanger.

    $context = context_module::instance($cmid);
    if ($draftitemid) {
        file_save_draft_area_files($draftitemid, $context->id, 'mod_pdfannotator', 'content', 0, array('subdirs' => true));
    }
    $files = $fs->get_area_files($context->id, 'mod_pdfannotator', 'content', 0, 'sortorder', false);
    if (count($files) == 1) {
        // Only one file attached, set it as main file automatically.
        $file = reset($files);
        file_set_sortorder($context->id, 'mod_pdfannotator', 'content', 0, $file->get_filepath(), $file->get_filename(), 1);
    }
}

function pdfannotator_render_listitem_actions(array $actions = null) {
    $menu = new action_menu();
    $menu->attributes['class'] .= ' course-item-actions item-actions';
    $hasitems = false;
    foreach ($actions as $key => $action) {
        $hasitems = true;
        $menu->add(new action_menu_link(
            $action['url'], $action['icon'], $action['string'], in_array($key, []), ['data-action' => $key, 'class' => 'action-' . $key]
        ));
    }
    if (!$hasitems) {
        return '';
    }
    return pdfannotator_render_action_menu($menu);
}

function pdfannotator_render_action_menu($menu) {
    global $OUTPUT;
    return $OUTPUT->render($menu);
}

function pdfannotator_subscribe_all($annotatorid, $context) {
    global $DB;
    $sql = "SELECT id FROM {pdfannotator_annotations} "
        . "WHERE pdfannotatorid = ? AND annotationtypeid NOT IN "
        . "(SELECT id FROM {pdfannotator_annotationtypes} WHERE name = ? OR name = ?)";
    $params = [$annotatorid, 'drawing', 'textbox'];
    $ids = $DB->get_fieldset_sql($sql, $params);
    foreach ($ids as $annotationid) {
        pdfannotator_comment::insert_subscription($annotationid, $context);
    }
}

function pdfannotator_unsubscribe_all($annotatorid) {
    global $DB, $USER;
    $sql = "SELECT a.id FROM {pdfannotator_annotations} a JOIN {pdfannotator_subscriptions} s "
        . "ON s.annotationid = a.id AND s.userid = ? WHERE pdfannotatorid = ?";
    $ids = $DB->get_fieldset_sql($sql, [$USER->id, $annotatorid]);
    foreach ($ids as $annotationid) {
        pdfannotator_comment::delete_subscription($annotationid);
    }
}

/**
 * Checks wether a user has subscribed to all questions in an annotator.
 * Returns 1 if all questions are subscribed, 0 if no questions are subscribed and -1 if at least one but not all questions are subscribed.
 * @param type $annotatorid
 */
function pdfannotator_subscribed($annotatorid) {
    global $DB, $USER;
    $sql = "SELECT COUNT(*) FROM {pdfannotator_annotations} a JOIN {pdfannotator_subscriptions} s "
        . "ON s.annotationid = a.id AND s.userid = ? WHERE a.pdfannotatorid = ?";
    $subscriptions = $DB->count_records_sql($sql, [$USER->id, $annotatorid]);
    $sql = "SELECT COUNT(*) FROM {pdfannotator_annotations} "
        . "WHERE pdfannotatorid = ? AND annotationtypeid NOT IN "
        . "(SELECT id FROM {pdfannotator_annotationtypes} WHERE name = ? OR name = ?)";
    $params = [$annotatorid, 'drawing', 'textbox'];
    $annotations = $DB->count_records_sql($sql, $params);

    if ($subscriptions === 0) {
        return 0;
    } else if ($subscriptions === $annotations) {
        return 1;
    } else {
        return -1;
    }
}

/**
 *
 * @param type $timestamp
 * @return string Day, D Month Y, Time
 */
function pdfannotator_get_user_datetime($timestamp) {
    $userdatetime = userdate($timestamp, $format = '', $timezone = 99, $fixday = true, $fixhour = true); // Method in lib/moodlelib.php
    return $userdatetime;
}

/**
 *
 * @param type $timestamp
 * @return string
 */
function pdfannotator_get_user_datetime_shortformat($timestamp) {
    $shortformat = get_string('strftimedatetime', 'pdfannotator'); // Format strings in moodle\lang\en\langconfig.php.
    $userdatetime = userdate($timestamp, $shortformat, $timezone = 99, $fixday = true, $fixhour = true); // Method in lib/moodlelib.php
    return $userdatetime;
}

/**
 * Function is executed each time one of the overview categories is accessed.
 * It creates the tab navigation and makes javascript accessible.
 *
 * @param type $CFG
 * @param type $PAGE
 * @param type $myrenderer
 * @param type $taburl
 * @param type $action
 * @param type $pdfannotator
 * @param type $context
 */
function pdfannotator_prepare_overviewpage($cmid, $myrenderer, $taburl, $action, $pdfannotator, $context) {

    global $CFG, $PAGE;

    $PAGE->set_title("overview");

    // 1.1 Display tab navigation.
    echo $myrenderer->pdfannotator_render_tabs($taburl, $pdfannotator->name, $context, $action['tab']);

    // 1.2 Give javascript (see below) access to the language string repository.
    $stringman = get_string_manager();
    $strings = $stringman->load_component_strings('pdfannotator', 'en'); // Method gets the strings of the language files.
    $PAGE->requires->strings_for_js(array_keys($strings), 'pdfannotator'); // Method to use the language-strings in javascript.
    // 1.3 Add the javascript file that determines the dynamic behaviour of the page.
    $PAGE->requires->js(new moodle_url("/mod/pdfannotator/shared/locallib.js?ver=00002"));
    $PAGE->requires->js(new moodle_url("/mod/pdfannotator/shared/overview.js?ver=00002"));

    // 1.4 Check user capabilities to view the different categories.
    // The argument 'false' disregards administrator's magical 'doanything' power.
    $capabilities = new stdClass();
    $capabilities->viewquestions = has_capability('mod/pdfannotator:viewquestions', $context);
    $capabilities->viewanswers = has_capability('mod/pdfannotator:viewanswers', $context);
    $capabilities->viewposts = has_capability('mod/pdfannotator:viewposts', $context);
    $capabilities->viewreports = has_capability('mod/pdfannotator:viewreports', $context);

    $params = array($pdfannotator->id, $cmid, $capabilities, $action['action']);
    $PAGE->requires->js_init_call('startOverview', $params, true); // 1. name of JS function, 2. parameters.
}

/**
 * Function serves as subcontroller that tells the annotator model to collect
 * all or all unsolved/solved questions asked in this course.
 *
 * @param int $openannotator
 * @param int $courseid
 * @param type $questionfilter
 * @return type
 */
function pdfannotator_get_questions($courseid, $context, $questionfilter) {

    global $DB;

    $cminfo = pdfannotator_instance::get_cm_info($courseid);
    list($insql, $inparams) = $DB->get_in_or_equal(array_keys($cminfo));

    $sql = "SELECT a.id as annoid, a.page, a.pdfannotatorid, p.name AS pdfannotatorname, p.usevotes, cm.id AS cmid, c.isquestion, "
        . "c.id as commentid, c.content, c.userid, c.visibility, c.timecreated, c.isdeleted, c.ishidden, "
        . "SUM(vote) AS votes, MAX(answ.timecreated) AS lastanswered "
        . "FROM {pdfannotator_annotations} a "
        . "JOIN {pdfannotator_comments} c ON c.annotationid = a.id "
        . "JOIN {pdfannotator} p ON a.pdfannotatorid = p.id "
        . "JOIN {course_modules} cm ON p.id = cm.instance "
        . "LEFT JOIN {pdfannotator_votes} v ON c.id=v.commentid "
        . "LEFT JOIN {pdfannotator_comments} answ ON answ.annotationid = a.id "
        . "WHERE c.isquestion = 1 AND p.course = ? AND cm.id $insql";
    if ($questionfilter == 0) {
        $sql = $sql . ' AND c.solved = 0 ';
    }
    if ($questionfilter == 1) {
        $sql = $sql . ' AND NOT c.solved = 0 ';
    }
    $sql = $sql . "GROUP BY a.id, p.name, p.usevotes, cm.id, c.id, a.page, a.pdfannotatorid, c.content, c.userid, c.visibility,"
        . "c.timecreated, c.isdeleted, c.ishidden, c.isquestion";
    $params = array_merge([$courseid], $inparams);
    $questions = $DB->get_records_sql($sql, $params);

    $seehidden = has_capability('mod/pdfannotator:seehiddencomments', $context);
    $labelhidden = "<br><span class='tag tag-info'>" . get_string('hiddenfromstudents') . "</span>"; // XXX use moodle method if exists.
    $labelunavailable = "<br><span class='tag tag-info'>" . get_string('restricted') . "</span>";

    $res = [];
    foreach ($questions as $key => $question) {

        if (!pdfannotator_can_see_comment($question, $context)) {
            continue;
        }

        if (empty($question->votes)) {
            $question->votes = 0;
        }
        if ($question->usevotes == 0) {
            $question->votes = '-';
        }
        $question->answercount = pdfannotator_count_answers($question->annoid, $context);

        $lastanswer = pdfannotator_get_last_answer($question->annoid, $context);
        if ($lastanswer) {
            $question->lastuser = $lastanswer->userid;
            $question->lastuservisibility = $lastanswer->visibility;
        } else {
            $question->lastanswered = false;
        }

        if ($question->isdeleted == 1) {
            $question->content = "<em>" . get_string('deletedQuestion', 'pdfannotator') . "</em>";
        } else if ($question->ishidden) {
            switch ($seehidden) {
                case 0:
                    $question->content = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
                    break;
                case 1:
                    $question->content = $question->content . $labelhidden;
                    $question->displayhidden = true;
                    break;
                default:
                    $question->content = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
            }
        }

        if (!$cminfo[$question->cmid]['visible']) { // Annotator is not visible for students.
            $question->content = $question->content . $labelhidden;
            $question->displayhidden = true;
        }
        if ($cminfo[$question->cmid]['availableinfo']) { // Annotator is restricted.
            $question->content = $question->content . $labelunavailable . " " . $cminfo[$question->cmid]['availableinfo'];
            $question->displayhidden = true;
        }

        $question->content = format_text($question->content);
        $question->link = (new moodle_url('/mod/pdfannotator/view.php', array('id' => $question->cmid,
            'page' => $question->page, 'annoid' => $question->annoid, 'commid' => $question->commentid)))->out();

        $res[] = $question;

    }
    return $res;
}

/**
 * Function serves as subcontroller that tells the annotator model to collect all
 * questions and answers this user posted in the course.
 *
 * @param int $courseid
 * @return type
 */
function pdfannotator_get_posts_by_this_user($courseid, $context) {

    global $DB, $USER;

    $cminfo = pdfannotator_instance::get_cm_info($courseid);
    list($insql, $inparams) = $DB->get_in_or_equal(array_keys($cminfo));

    $seehidden = has_capability('mod/pdfannotator:seehiddencomments', $context);
    $labelhidden = "<br><span class='tag tag-info'>" . get_string('hiddenforparticipants', 'pdfannotator') . "</span>";
    $labelunavailable = "<br><span class='tag tag-info'>" . get_string('restricted') . "</span>";

    $sql = "SELECT c.id as commid, c.annotationid, c.content, c.timemodified, c.ishidden, a.id AS annoid, "
        . "a.page, a.pdfannotatorid, p.name AS pdfannotatorname, p.usevotes, cm.id AS cmid, "
        . "SUM(v.vote) AS votes "
        . "FROM {pdfannotator_comments} c "
        . "JOIN {pdfannotator_annotations} a ON c.annotationid = a.id "
        . "JOIN {pdfannotator} p ON a.pdfannotatorid = p.id "
        . "JOIN {course_modules} cm ON p.id = cm.instance "
        . "LEFT JOIN {pdfannotator_votes} v ON c.id = v.commentid "
        . "WHERE c.userid = ? AND p.course = ? AND cm.id $insql "
        . "GROUP BY a.id, p.name, p.usevotes, cm.id, c.id, c.annotationid, c.content, c.timemodified, c.ishidden, a.page, a.pdfannotatorid";

    $params = array_merge([$USER->id, $courseid], $inparams);

    $posts = $DB->get_records_sql($sql, $params);

    foreach ($posts as $key => $post) {
        if (empty($post->votes)) {
            $post->votes = 0;
        }
        if ($post->usevotes == 0) {
            $post->votes = '-';
        }

        if ($post->ishidden) { // Post in annotator is hidden.
            switch ($seehidden) {
                case 0:
                    $post->content = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
                    break;
                case 1:
                    $post->content = $post->content . $labelhidden;
                    $post->displayhidden = true;
                    break;
                default:
                    $post->content = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
            }
        }

        if (!$cminfo[$post->cmid]['visible']) {  // Annotator is hidden.
            $post->content = $post->content . $labelhidden;
            $post->displayhidden = true;
        }
        if ($cminfo[$post->cmid]['availableinfo']) {  // Annotator is restricted.
            $post->content = $post->content . $labelunavailable . " " . $cminfo[$post->cmid]['availableinfo'];
            $post->displayhidden = true;
        }

        $params = array('id' => $post->cmid, 'page' => $post->page, 'annoid' => $post->annotationid, 'commid' => $post->commid);
        $post->link = (new moodle_url('/mod/pdfannotator/view.php', $params))->out();
        $post->content = format_text($post->content);
    }
    return $posts;
}

/**
 * Function serves as subcontroller that tells the annotator model to collect
 * all answers given to questions that the current user asked or subscribed to
 * in this course.
 *
 * @param int $courseid
 * @param Moodle object? $context
 * @param int $answerfilter
 * @return array of stdClass objects
 */
function pdfannotator_get_answers_for_this_user($courseid, $context, $answerfilter = 1) {

    global $DB, $USER;

    $cminfo = pdfannotator_instance::get_cm_info($courseid);
    list($insql, $inparams) = $DB->get_in_or_equal(array_keys($cminfo));

    $seehidden = has_capability('mod/pdfannotator:seehiddencomments', $context);
    $labelhidden = "<br><span class='tag tag-info'>" . get_string('hiddenforparticipants', 'pdfannotator') . "</span>";
    $labelunavailable = "<br><span class='tag tag-info'>" . get_string('restricted') . "</span>";

    if ($answerfilter == 0) { // Either: get all answers in this annotator.
        $sql = "SELECT c.id AS answerid, c.content AS answer, c.userid AS userid, c.visibility, "
            . "c.timemodified, c.solved AS correct, c.ishidden AS answerhidden, a.id AS annoid, a.page, q.id AS questionid,"
            . "q.userid AS questionuserid, c.isquestion, c.annotationid, "
            . "q.visibility AS questionvisibility, "
            . "q.content AS answeredquestion, q.isdeleted AS questiondeleted, q.ishidden AS questionhidden, p.id AS annotatorid, "
            . "p.name AS pdfannotatorname, cm.id AS cmid, s.id AS issubscribed "
            . "FROM {pdfannotator_annotations} a "
            . "LEFT JOIN {pdfannotator_subscriptions} s ON a.id = s.annotationid AND s.userid = ? "
            . "JOIN {pdfannotator_comments} q ON q.annotationid = a.id " // Question comment.
            . "JOIN {pdfannotator_comments} c ON c.annotationid = a.id " // Answer comment.
            . "JOIN {pdfannotator} p ON a.pdfannotatorid = p.id "
            . "JOIN {course_modules} cm ON p.id = cm.instance "
            . "WHERE p.course = ? AND q.isquestion = 1 AND NOT c.isquestion = 1 AND NOT c.isdeleted = 1 AND cm.id $insql "
            . "ORDER BY annoid ASC";
    } else { // Or: get answers to those questions the user subscribed to.
        $sql = "SELECT c.id AS answerid, c.content AS answer, c.userid AS userid, c.visibility, "
            . "c.timemodified, c.solved AS correct, c.ishidden AS answerhidden, a.id AS annoid, a.page, q.id AS questionid, "
            . "q.userid AS questionuserid, c.isquestion, c.annotationid, "
            . "q.visibility AS questionvisibility, "
            . "q.content AS answeredquestion, q.isdeleted AS questiondeleted, q.ishidden AS questionhidden, p.id AS annotatorid, "
            . "p.name AS pdfannotatorname, cm.id AS cmid "
            . "FROM {pdfannotator_subscriptions} s "
            . "JOIN {pdfannotator_annotations} a ON a.id = s.annotationid "
            . "JOIN {pdfannotator_comments} q ON q.annotationid = a.id " // Question comment.
            . "JOIN {pdfannotator_comments} c ON c.annotationid = a.id " // Answer comment.
            . "JOIN {pdfannotator} p ON a.pdfannotatorid = p.id "
            . "JOIN {course_modules} cm ON p.id = cm.instance "
            . "WHERE s.userid = ? AND p.course = ? AND q.isquestion = 1 AND NOT c.isquestion = 1 AND NOT c.isdeleted = 1 AND cm.id $insql "
            . "ORDER BY annoid ASC";
    }

    $params = array_merge([$USER->id, $courseid], $inparams);

    $entries = $DB->get_records_sql($sql, $params);

    $res = [];
    foreach ($entries as $key => $entry) {
        if (!pdfannotator_can_see_comment($entry, $context)) {
            continue;
        }
        $entry->link = (new moodle_url('/mod/pdfannotator/view.php',
            array('id' => $entry->cmid, 'page' => $entry->page, 'annoid' => $entry->annoid, 'commid' => $entry->answerid)))->out();
        $entry->questionlink = (new moodle_url('/mod/pdfannotator/view.php',
            array('id' => $entry->cmid, 'page' => $entry->page, 'annoid' => $entry->annoid, 'commid' => $entry->questionid)))->out();

        if ($entry->questiondeleted == 1) {
            $entry->answeredquestion = get_string('deletedComment', 'pdfannotator');
        } else if ($entry->questionhidden) {
            switch ($seehidden) {
                case 0:
                    $entry->answeredquestion = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
                    break;
                case 1:
                    $entry->displayquestionhidden = true;
                    $entry->answeredquestion = $entry->answeredquestion . $labelhidden;
                    break;
                default:
                    $entry->answeredquestion = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
            }
        }

        if ($entry->answerhidden) {
            switch ($seehidden) {
                case 0:
                    $entry->answer = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
                    break;
                case 1:
                    $entry->answer = $entry->answer . $labelhidden;
                    $entry->displayhidden = true;
                    break;
                default:
                    $entry->answer = "<em>" . get_string('hiddenComment', 'pdfannotator') . "</em>";
            }
        }

        if (!$cminfo[$entry->cmid]['visible']) {  // Annotator is hidden.
            $entry->answeredquestion = $entry->answeredquestion . $labelhidden;
            $entry->answer = $entry->answer . $labelhidden;
            $entry->displayhidden = true;
        }
        if ($cminfo[$entry->cmid]['availableinfo']) {  // Annotator is restricted.
            $entry->answeredquestion = $entry->answeredquestion . $labelunavailable . " ". $cminfo[$entry->cmid]['availableinfo'];;
            $entry->answer = $entry->answer . $labelunavailable . " ". $cminfo[$entry->cmid]['availableinfo'];
            $entry->displayhidden = true;
        }

        $entry->answeredquestion = format_text($entry->answeredquestion);
        $entry->answer = format_text($entry->answer);

        $res[] = $entry;
    }

    return $res;
}

/**
 * Function retrieves reports and their respective reported comments from db.
 * Depending on the reportfilter, only read/unread reports or all reports are retrieved.
 *
 * @param int $courseid