/message/lib.php

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<?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/>.

/**
 * Library functions for messaging
 *
 * @package   core_message
 * @copyright 2008 Luis Rodrigues
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

require_once($CFG->libdir.'/eventslib.php');

define ('MESSAGE_SHORTLENGTH', 300);

define ('MESSAGE_DISCUSSION_WIDTH',600);
define ('MESSAGE_DISCUSSION_HEIGHT',500);

define ('MESSAGE_SHORTVIEW_LIMIT', 8);//the maximum number of messages to show on the short message history

define('MESSAGE_HISTORY_SHORT',0);
define('MESSAGE_HISTORY_ALL',1);

define('MESSAGE_VIEW_UNREAD_MESSAGES','unread');
define('MESSAGE_VIEW_RECENT_CONVERSATIONS','recentconversations');
define('MESSAGE_VIEW_RECENT_NOTIFICATIONS','recentnotifications');
define('MESSAGE_VIEW_CONTACTS','contacts');
define('MESSAGE_VIEW_BLOCKED','blockedusers');
define('MESSAGE_VIEW_COURSE','course_');
define('MESSAGE_VIEW_SEARCH','search');

define('MESSAGE_SEARCH_MAX_RESULTS', 200);

define('MESSAGE_CONTACTS_PER_PAGE',10);
define('MESSAGE_MAX_COURSE_NAME_LENGTH', 30);

/**
 * Define contants for messaging default settings population. For unambiguity of
 * plugin developer intentions we use 4-bit value (LSB numbering):
 * bit 0 - whether to send message when user is loggedin (MESSAGE_DEFAULT_LOGGEDIN)
 * bit 1 - whether to send message when user is loggedoff (MESSAGE_DEFAULT_LOGGEDOFF)
 * bit 2..3 - messaging permission (MESSAGE_DISALLOWED|MESSAGE_PERMITTED|MESSAGE_FORCED)
 *
 * MESSAGE_PERMITTED_MASK contains the mask we use to distinguish permission setting
 */

define('MESSAGE_DEFAULT_LOGGEDIN', 0x01); // 0001
define('MESSAGE_DEFAULT_LOGGEDOFF', 0x02); // 0010

define('MESSAGE_DISALLOWED', 0x04); // 0100
define('MESSAGE_PERMITTED', 0x08); // 1000
define('MESSAGE_FORCED', 0x0c); // 1100

define('MESSAGE_PERMITTED_MASK', 0x0c); // 1100

/**
 * Set default value for default outputs permitted setting
 */
define('MESSAGE_DEFAULT_PERMITTED', 'permitted');

/**
 * Print the selector that allows the user to view their contacts, course participants, their recent
 * conversations etc
 *
 * @param int $countunreadtotal how many unread messages does the user have?
 * @param int $viewing What is the user viewing? ie MESSAGE_VIEW_UNREAD_MESSAGES, MESSAGE_VIEW_SEARCH etc
 * @param object $user1 the user whose messages are being viewed
 * @param object $user2 the user $user1 is talking to
 * @param array $blockedusers an array of users blocked by $user1
 * @param array $onlinecontacts an array of $user1's online contacts
 * @param array $offlinecontacts an array of $user1's offline contacts
 * @param array $strangers an array of users who have messaged $user1 who aren't contacts
 * @param bool $showactionlinks show action links (add/remove contact etc)
 * @param int $page if there are so many users listed that they have to be split into pages what page are we viewing
 * @return void
 */
function message_print_contact_selector($countunreadtotal, $viewing, $user1, $user2, $blockedusers, $onlinecontacts, $offlinecontacts, $strangers, $showactionlinks, $page=0) {
    global $PAGE;

    echo html_writer::start_tag('div', array('class' => 'contactselector mdl-align'));

    //if 0 unread messages and they've requested unread messages then show contacts
    if ($countunreadtotal == 0 && $viewing == MESSAGE_VIEW_UNREAD_MESSAGES) {
        $viewing = MESSAGE_VIEW_CONTACTS;
    }

    //if they have no blocked users and they've requested blocked users switch them over to contacts
    if (count($blockedusers) == 0 && $viewing == MESSAGE_VIEW_BLOCKED) {
        $viewing = MESSAGE_VIEW_CONTACTS;
    }

    $onlyactivecourses = true;
    $courses = enrol_get_users_courses($user1->id, $onlyactivecourses);
    $coursecontexts = message_get_course_contexts($courses);//we need one of these again so holding on to them

    $strunreadmessages = null;
    if ($countunreadtotal>0) { //if there are unread messages
        $strunreadmessages = get_string('unreadmessages','message', $countunreadtotal);
    }

    message_print_usergroup_selector($viewing, $courses, $coursecontexts, $countunreadtotal, count($blockedusers), $strunreadmessages, $user1);

    if ($viewing == MESSAGE_VIEW_UNREAD_MESSAGES) {
        message_print_contacts($onlinecontacts, $offlinecontacts, $strangers, $PAGE->url, 1, $showactionlinks,$strunreadmessages, $user2);
    } else if ($viewing == MESSAGE_VIEW_CONTACTS || $viewing == MESSAGE_VIEW_SEARCH || $viewing == MESSAGE_VIEW_RECENT_CONVERSATIONS || $viewing == MESSAGE_VIEW_RECENT_NOTIFICATIONS) {
        message_print_contacts($onlinecontacts, $offlinecontacts, $strangers, $PAGE->url, 0, $showactionlinks, $strunreadmessages, $user2);
    } else if ($viewing == MESSAGE_VIEW_BLOCKED) {
        message_print_blocked_users($blockedusers, $PAGE->url, $showactionlinks, null, $user2);
    } else if (substr($viewing, 0, 7) == MESSAGE_VIEW_COURSE) {
        $courseidtoshow = intval(substr($viewing, 7));

        if (!empty($courseidtoshow)
            && array_key_exists($courseidtoshow, $coursecontexts)
            && has_capability('moodle/course:viewparticipants', $coursecontexts[$courseidtoshow])) {

            message_print_participants($coursecontexts[$courseidtoshow], $courseidtoshow, $PAGE->url, $showactionlinks, null, $page, $user2);
        } else {
            //shouldn't get here. User trying to access a course they're not in perhaps.
            add_to_log(SITEID, 'message', 'view', 'index.php', $viewing);
        }
    }

    // Only show the search button if we're viewing our own messages.
    // Search isn't currently able to deal with user A wanting to search user B's messages.
    if ($showactionlinks) {
        echo html_writer::start_tag('form', array('action' => 'index.php','method' => 'GET'));
        echo html_writer::start_tag('fieldset');
        $managebuttonclass = 'visible';
        if ($viewing == MESSAGE_VIEW_SEARCH) {
            $managebuttonclass = 'hiddenelement';
        }
        $strmanagecontacts = get_string('search','message');
        echo html_writer::empty_tag('input', array('type' => 'hidden','name' => 'viewing','value' => MESSAGE_VIEW_SEARCH));
        echo html_writer::empty_tag('input', array('type' => 'submit','value' => $strmanagecontacts,'class' => $managebuttonclass));
        echo html_writer::end_tag('fieldset');
        echo html_writer::end_tag('form');
    }

    echo html_writer::end_tag('div');
}

/**
 * Print course participants. Called by message_print_contact_selector()
 *
 * @param object $context the course context
 * @param int $courseid the course ID
 * @param string $contactselecturl the url to send the user to when a contact's name is clicked
 * @param bool $showactionlinks show action links (add/remove contact etc) next to the users
 * @param string $titletodisplay Optionally specify a title to display above the participants
 * @param int $page if there are so many users listed that they have to be split into pages what page are we viewing
 * @param object $user2 the user $user1 is talking to. They will be highlighted if they appear in the list of participants
 * @return void
 */
function message_print_participants($context, $courseid, $contactselecturl=null, $showactionlinks=true, $titletodisplay=null, $page=0, $user2=null) {
    global $DB, $USER, $PAGE, $OUTPUT;

    if (empty($titletodisplay)) {
        $titletodisplay = get_string('participants');
    }

    $countparticipants = count_enrolled_users($context);

    list($esql, $params) = get_enrolled_sql($context);
    $params['mcuserid'] = $USER->id;
    $ufields = user_picture::fields('u');

    $sql = "SELECT $ufields, mc.id as contactlistid, mc.blocked
              FROM {user} u
              JOIN ($esql) je ON je.id = u.id
              LEFT JOIN {message_contacts} mc ON mc.contactid = u.id AND mc.userid = :mcuserid
             WHERE u.deleted = 0";

    $participants = $DB->get_records_sql($sql, $params, $page * MESSAGE_CONTACTS_PER_PAGE, MESSAGE_CONTACTS_PER_PAGE);

    $pagingbar = new paging_bar($countparticipants, $page, MESSAGE_CONTACTS_PER_PAGE, $PAGE->url, 'page');
    echo $OUTPUT->render($pagingbar);

    echo html_writer::start_tag('table', array('id' => 'message_participants', 'class' => 'boxaligncenter', 'cellspacing' => '2', 'cellpadding' => '0', 'border' => '0'));

    echo html_writer::start_tag('tr');
    echo html_writer::tag('td', $titletodisplay, array('colspan' => 3, 'class' => 'heading'));
    echo html_writer::end_tag('tr');

    foreach ($participants as $participant) {
        if ($participant->id != $USER->id) {

            $iscontact = false;
            $isblocked = false;
            if ( $participant->contactlistid )  {
                if ($participant->blocked == 0) {
                    // Is contact. Is not blocked.
                    $iscontact = true;
                    $isblocked = false;
                } else {
                    // Is blocked.
                    $iscontact = false;
                    $isblocked = true;
                }
            }

            $participant->messagecount = 0;//todo it would be nice if the course participant could report new messages
            message_print_contactlist_user($participant, $iscontact, $isblocked, $contactselecturl, $showactionlinks, $user2);
        }
    }

    echo html_writer::end_tag('table');
}

/**
 * Retrieve users blocked by $user1
 *
 * @param object $user1 the user whose messages are being viewed
 * @param object $user2 the user $user1 is talking to. If they are being blocked
 *                      they will have a variable called 'isblocked' added to their user object
 * @return array the users blocked by $user1
 */
function message_get_blocked_users($user1=null, $user2=null) {
    global $DB, $USER;

    if (empty($user1)) {
        $user1 = $USER;
    }

    if (!empty($user2)) {
        $user2->isblocked = false;
    }

    $blockedusers = array();

    $userfields = user_picture::fields('u', array('lastaccess'));
    $blockeduserssql = "SELECT $userfields, COUNT(m.id) AS messagecount
                          FROM {message_contacts} mc
                          JOIN {user} u ON u.id = mc.contactid
                          LEFT OUTER JOIN {message} m ON m.useridfrom = mc.contactid AND m.useridto = :user1id1
                         WHERE mc.userid = :user1id2 AND mc.blocked = 1
                      GROUP BY $userfields
                      ORDER BY u.firstname ASC";
    $rs =  $DB->get_recordset_sql($blockeduserssql, array('user1id1' => $user1->id, 'user1id2' => $user1->id));

    foreach($rs as $rd) {
        $blockedusers[] = $rd;

        if (!empty($user2) && $user2->id == $rd->id) {
            $user2->isblocked = true;
        }
    }
    $rs->close();

    return $blockedusers;
}

/**
 * Print users blocked by $user1. Called by message_print_contact_selector()
 *
 * @param array $blockedusers the users blocked by $user1
 * @param string $contactselecturl the url to send the user to when a contact's name is clicked
 * @param bool $showactionlinks show action links (add/remove contact etc) next to the users
 * @param string $titletodisplay Optionally specify a title to display above the participants
 * @param object $user2 the user $user1 is talking to. They will be highlighted if they appear in the list of blocked users
 * @return void
 */
function message_print_blocked_users($blockedusers, $contactselecturl=null, $showactionlinks=true, $titletodisplay=null, $user2=null) {
    global $DB, $USER;

    $countblocked = count($blockedusers);

    echo html_writer::start_tag('table', array('id' => 'message_contacts', 'class' => 'boxaligncenter'));

    if (!empty($titletodisplay)) {
        echo html_writer::start_tag('tr');
        echo html_writer::tag('td', $titletodisplay, array('colspan' => 3, 'class' => 'heading'));
        echo html_writer::end_tag('tr');
    }

    if ($countblocked) {
        echo html_writer::start_tag('tr');
        echo html_writer::tag('td', get_string('blockedusers', 'message', $countblocked), array('colspan' => 3, 'class' => 'heading'));
        echo html_writer::end_tag('tr');

        $isuserblocked = true;
        $isusercontact = false;
        foreach ($blockedusers as $blockeduser) {
            message_print_contactlist_user($blockeduser, $isusercontact, $isuserblocked, $contactselecturl, $showactionlinks, $user2);
        }
    }

    echo html_writer::end_tag('table');
}

/**
 * Retrieve $user1's contacts (online, offline and strangers)
 *
 * @param object $user1 the user whose messages are being viewed
 * @param object $user2 the user $user1 is talking to. If they are a contact
 *                      they will have a variable called 'iscontact' added to their user object
 * @return array containing 3 arrays. array($onlinecontacts, $offlinecontacts, $strangers)
 */
function message_get_contacts($user1=null, $user2=null) {
    global $DB, $CFG, $USER;

    if (empty($user1)) {
        $user1 = $USER;
    }

    if (!empty($user2)) {
        $user2->iscontact = false;
    }

    $timetoshowusers = 300; //Seconds default
    if (isset($CFG->block_online_users_timetosee)) {
        $timetoshowusers = $CFG->block_online_users_timetosee * 60;
    }

    // time which a user is counting as being active since
    $timefrom = time()-$timetoshowusers;

    // people in our contactlist who are online
    $onlinecontacts  = array();
    // people in our contactlist who are offline
    $offlinecontacts = array();
    // people who are not in our contactlist but have sent us a message
    $strangers       = array();

    $userfields = user_picture::fields('u', array('lastaccess'));

    // get all in our contactlist who are not blocked in our contact list
    // and count messages we have waiting from each of them
    $contactsql = "SELECT $userfields, COUNT(m.id) AS messagecount
                     FROM {message_contacts} mc
                     JOIN {user} u ON u.id = mc.contactid
                     LEFT OUTER JOIN {message} m ON m.useridfrom = mc.contactid AND m.useridto = ?
                    WHERE mc.userid = ? AND mc.blocked = 0
                 GROUP BY $userfields
                 ORDER BY u.firstname ASC";

    $rs = $DB->get_recordset_sql($contactsql, array($user1->id, $user1->id));
    foreach ($rs as $rd) {
        if ($rd->lastaccess >= $timefrom) {
            // they have been active recently, so are counted online
            $onlinecontacts[] = $rd;

        } else {
            $offlinecontacts[] = $rd;
        }

        if (!empty($user2) && $user2->id == $rd->id) {
            $user2->iscontact = true;
        }
    }
    $rs->close();

    // get messages from anyone who isn't in our contact list and count the number
    // of messages we have from each of them
    $strangersql = "SELECT $userfields, count(m.id) as messagecount
                      FROM {message} m
                      JOIN {user} u  ON u.id = m.useridfrom
                      LEFT OUTER JOIN {message_contacts} mc ON mc.contactid = m.useridfrom AND mc.userid = m.useridto
                     WHERE mc.id IS NULL AND m.useridto = ?
                  GROUP BY $userfields
                  ORDER BY u.firstname ASC";

    $rs = $DB->get_recordset_sql($strangersql, array($USER->id));
    // Add user id as array index, so supportuser and noreply user don't get duplicated (if they are real users).
    foreach ($rs as $rd) {
        $strangers[$rd->id] = $rd;
    }
    $rs->close();

    // Add noreply user and support user to the list, if they don't exist.
    $supportuser = core_user::get_support_user();
    if (!isset($strangers[$supportuser->id])) {
        $supportuser->messagecount = message_count_unread_messages($USER, $supportuser);
        if ($supportuser->messagecount > 0) {
            $strangers[$supportuser->id] = $supportuser;
        }
    }

    $noreplyuser = core_user::get_noreply_user();
    if (!isset($strangers[$noreplyuser->id])) {
        $noreplyuser->messagecount = message_count_unread_messages($USER, $noreplyuser);
        if ($noreplyuser->messagecount > 0) {
            $strangers[$noreplyuser->id] = $noreplyuser;
        }
    }
    return array($onlinecontacts, $offlinecontacts, $strangers);
}

/**
 * Print $user1's contacts. Called by message_print_contact_selector()
 *
 * @param array $onlinecontacts $user1's contacts which are online
 * @param array $offlinecontacts $user1's contacts which are offline
 * @param array $strangers users which are not contacts but who have messaged $user1
 * @param string $contactselecturl the url to send the user to when a contact's name is clicked
 * @param int $minmessages The minimum number of unread messages required from a user for them to be displayed
 *                         Typically 0 (show all contacts) or 1 (only show contacts from whom we have a new message)
 * @param bool $showactionlinks show action links (add/remove contact etc) next to the users
 * @param string $titletodisplay Optionally specify a title to display above the participants
 * @param object $user2 the user $user1 is talking to. They will be highlighted if they appear in the list of contacts
 * @return void
 */
function message_print_contacts($onlinecontacts, $offlinecontacts, $strangers, $contactselecturl=null, $minmessages=0, $showactionlinks=true, $titletodisplay=null, $user2=null) {
    global $CFG, $PAGE, $OUTPUT;

    $countonlinecontacts  = count($onlinecontacts);
    $countofflinecontacts = count($offlinecontacts);
    $countstrangers       = count($strangers);
    $isuserblocked = null;

    if ($countonlinecontacts + $countofflinecontacts == 0) {
        echo html_writer::tag('div', get_string('contactlistempty', 'message'), array('class' => 'heading'));
    }

    echo html_writer::start_tag('table', array('id' => 'message_contacts', 'class' => 'boxaligncenter'));

    if (!empty($titletodisplay)) {
        message_print_heading($titletodisplay);
    }

    if($countonlinecontacts) {
        // Print out list of online contacts.

        if (empty($titletodisplay)) {
            message_print_heading(get_string('onlinecontacts', 'message', $countonlinecontacts));
        }

        $isuserblocked = false;
        $isusercontact = true;
        foreach ($onlinecontacts as $contact) {
            if ($minmessages == 0 || $contact->messagecount >= $minmessages) {
                message_print_contactlist_user($contact, $isusercontact, $isuserblocked, $contactselecturl, $showactionlinks, $user2);
            }
        }
    }

    if ($countofflinecontacts) {
        // Print out list of offline contacts.

        if (empty($titletodisplay)) {
            message_print_heading(get_string('offlinecontacts', 'message', $countofflinecontacts));
        }

        $isuserblocked = false;
        $isusercontact = true;
        foreach ($offlinecontacts as $contact) {
            if ($minmessages == 0 || $contact->messagecount >= $minmessages) {
                message_print_contactlist_user($contact, $isusercontact, $isuserblocked, $contactselecturl, $showactionlinks, $user2);
            }
        }

    }

    // Print out list of incoming contacts.
    if ($countstrangers) {
        message_print_heading(get_string('incomingcontacts', 'message', $countstrangers));

        $isuserblocked = false;
        $isusercontact = false;
        foreach ($strangers as $stranger) {
            if ($minmessages == 0 || $stranger->messagecount >= $minmessages) {
                message_print_contactlist_user($stranger, $isusercontact, $isuserblocked, $contactselecturl, $showactionlinks, $user2);
            }
        }
    }

    echo html_writer::end_tag('table');

    if ($countstrangers && ($countonlinecontacts + $countofflinecontacts == 0)) {  // Extra help
        echo html_writer::tag('div','('.get_string('addsomecontactsincoming', 'message').')',array('class' => 'note'));
    }
}

/**
 * Print a select box allowing the user to choose to view new messages, course participants etc.
 *
 * Called by message_print_contact_selector()
 * @param int $viewing What page is the user viewing ie MESSAGE_VIEW_UNREAD_MESSAGES, MESSAGE_VIEW_RECENT_CONVERSATIONS etc
 * @param array $courses array of course objects. The courses the user is enrolled in.
 * @param array $coursecontexts array of course contexts. Keyed on course id.
 * @param int $countunreadtotal how many unread messages does the user have?
 * @param int $countblocked how many users has the current user blocked?
 * @param stdClass $user1 The user whose messages we are viewing.
 * @param string $strunreadmessages a preconstructed message about the number of unread messages the user has
 * @return void
 */
function message_print_usergroup_selector($viewing, $courses, $coursecontexts, $countunreadtotal, $countblocked, $strunreadmessages, $user1 = null) {
    $options = array();

    if ($countunreadtotal>0) { //if there are unread messages
        $options[MESSAGE_VIEW_UNREAD_MESSAGES] = $strunreadmessages;
    }

    $str = get_string('contacts', 'message');
    $options[MESSAGE_VIEW_CONTACTS] = $str;

    $options[MESSAGE_VIEW_RECENT_CONVERSATIONS] = get_string('mostrecentconversations', 'message');
    $options[MESSAGE_VIEW_RECENT_NOTIFICATIONS] = get_string('mostrecentnotifications', 'message');

    if (!empty($courses)) {
        $courses_options = array();

        foreach($courses as $course) {
            if (has_capability('moodle/course:viewparticipants', $coursecontexts[$course->id])) {
                //Not using short_text() as we want the end of the course name. Not the beginning.
                $shortname = format_string($course->shortname, true, array('context' => $coursecontexts[$course->id]));
                if (core_text::strlen($shortname) > MESSAGE_MAX_COURSE_NAME_LENGTH) {
                    $courses_options[MESSAGE_VIEW_COURSE.$course->id] = '...'.core_text::substr($shortname, -MESSAGE_MAX_COURSE_NAME_LENGTH);
                } else {
                    $courses_options[MESSAGE_VIEW_COURSE.$course->id] = $shortname;
                }
            }
        }

        if (!empty($courses_options)) {
            $options[] = array(get_string('courses') => $courses_options);
        }
    }

    if ($countblocked>0) {
        $str = get_string('blockedusers','message', $countblocked);
        $options[MESSAGE_VIEW_BLOCKED] = $str;
    }

    echo html_writer::start_tag('form', array('id' => 'usergroupform','method' => 'get','action' => ''));
    echo html_writer::start_tag('fieldset');
    if ( !empty($user1) && !empty($user1->id) ) {
        echo html_writer::empty_tag('input', array('type' => 'hidden','name' => 'user1','value' => $user1->id));
    }
    echo html_writer::label(get_string('messagenavigation', 'message'), 'viewing');
    echo html_writer::select($options, 'viewing', $viewing, false, array('id' => 'viewing','onchange' => 'this.form.submit()'));
    echo html_writer::end_tag('fieldset');
    echo html_writer::end_tag('form');
}

/**
 * Load the course contexts for all of the users courses
 *
 * @param array $courses array of course objects. The courses the user is enrolled in.
 * @return array of course contexts
 */
function message_get_course_contexts($courses) {
    $coursecontexts = array();

    foreach($courses as $course) {
        $coursecontexts[$course->id] = context_course::instance($course->id);
    }

    return $coursecontexts;
}

/**
 * strip off action parameters like 'removecontact'
 *
 * @param moodle_url/string $moodleurl a URL. Typically the current page URL.
 * @return string the URL minus parameters that perform actions (like adding/removing/blocking a contact).
 */
function message_remove_url_params($moodleurl) {
    $newurl = new moodle_url($moodleurl);
    $newurl->remove_params('addcontact','removecontact','blockcontact','unblockcontact');
    return $newurl->out();
}

/**
 * Count the number of messages with a field having a specified value.
 * if $field is empty then return count of the whole array
 * if $field is non-existent then return 0
 *
 * @param array $messagearray array of message objects
 * @param string $field the field to inspect on the message objects
 * @param string $value the value to test the field against
 */
function message_count_messages($messagearray, $field='', $value='') {
    if (!is_array($messagearray)) return 0;
    if ($field == '' or empty($messagearray)) return count($messagearray);

    $count = 0;
    foreach ($messagearray as $message) {
        $count += ($message->$field == $value) ? 1 : 0;
    }
    return $count;
}

/**
 * Returns the count of unread messages for user. Either from a specific user or from all users.
 *
 * @param object $user1 the first user. Defaults to $USER
 * @param object $user2 the second user. If null this function will count all of user 1's unread messages.
 * @return int the count of $user1's unread messages
 */
function message_count_unread_messages($user1=null, $user2=null) {
    global $USER, $DB;

    if (empty($user1)) {
        $user1 = $USER;
    }

    if (!empty($user2)) {
        return $DB->count_records_select('message', "useridto = ? AND useridfrom = ?",
            array($user1->id, $user2->id), "COUNT('id')");
    } else {
        return $DB->count_records_select('message', "useridto = ?",
            array($user1->id), "COUNT('id')");
    }
}

/**
 * Count the number of users blocked by $user1
 *
 * @param object $user1 user object
 * @return int the number of blocked users
 */
function message_count_blocked_users($user1=null) {
    global $USER, $DB;

    if (empty($user1)) {
        $user1 = $USER;
    }

    $sql = "SELECT count(mc.id)
            FROM {message_contacts} mc
            WHERE mc.userid = :userid AND mc.blocked = 1";
    $params = array('userid' => $user1->id);

    return $DB->count_records_sql($sql, $params);
}

/**
 * Print the search form and search results if a search has been performed
 *
 * @param  boolean $advancedsearch show basic or advanced search form
 * @param  object $user1 the current user
 * @return boolean true if a search was performed
 */
function message_print_search($advancedsearch = false, $user1=null) {
    $frm = data_submitted();

    $doingsearch = false;
    if ($frm) {
        if (confirm_sesskey()) {
            $doingsearch = !empty($frm->combinedsubmit) || !empty($frm->keywords) || (!empty($frm->personsubmit) and !empty($frm->name));
        } else {
            $frm = false;
        }
    }

    if (!empty($frm->combinedsearch)) {
        $combinedsearchstring = $frm->combinedsearch;
    } else {
        //$combinedsearchstring = get_string('searchcombined','message').'...';
        $combinedsearchstring = '';
    }

    if ($doingsearch) {
        if ($advancedsearch) {

            $messagesearch = '';
            if (!empty($frm->keywords)) {
                $messagesearch = $frm->keywords;
            }
            $personsearch = '';
            if (!empty($frm->name)) {
                $personsearch = $frm->name;
            }
            include('search_advanced.html');
        } else {
            include('search.html');
        }

        $showicontext = false;
        message_print_search_results($frm, $showicontext, $user1);

        return true;
    } else {

        if ($advancedsearch) {
            $personsearch = $messagesearch = '';
            include('search_advanced.html');
        } else {
            include('search.html');
        }
        return false;
    }
}

/**
 * Get the users recent conversations meaning all the people they've recently
 * sent or received a message from plus the most recent message sent to or received from each other user
 *
 * @param object $user the current user
 * @param int $limitfrom can be used for paging
 * @param int $limitto can be used for paging
 * @return array
 */
function message_get_recent_conversations($user, $limitfrom=0, $limitto=100) {
    global $DB;

    $userfields = user_picture::fields('otheruser', array('lastaccess'));

    // This query retrieves the most recent message received from or sent to
    // seach other user.
    //
    // If two messages have the same timecreated, we take the one with the
    // larger id.
    //
    // There is a separate query for read and unread messages as they are stored
    // in different tables. They were originally retrieved in one query but it
    // was so large that it was difficult to be confident in its correctness.
    $sql = "SELECT $userfields,
                   message.id as mid, message.notification, message.smallmessage, message.fullmessage,
                   message.fullmessagehtml, message.fullmessageformat, message.timecreated,
                   contact.id as contactlistid, contact.blocked

              FROM {message_read} message
              JOIN {user} otheruser ON otheruser.id = CASE
                                WHEN message.useridto = :userid1 THEN message.useridfrom
                                                                 ELSE message.useridto END
         LEFT JOIN {message_contacts} contact ON contact.userid = :userid2 AND contact.contactid = otheruser.id

             WHERE otheruser.deleted = 0
               AND (message.useridto = :userid3 OR message.useridfrom = :userid4)
               AND message.notification = 0
               AND NOT EXISTS (
                        SELECT 1
                          FROM {message_read} othermessage
                         WHERE ((othermessage.useridto = :userid5 AND othermessage.useridfrom = otheruser.id) OR
                                (othermessage.useridfrom = :userid6 AND othermessage.useridto = otheruser.id))
                           AND (othermessage.timecreated > message.timecreated OR (
                                othermessage.timecreated = message.timecreated AND othermessage.id > message.id))
                   )

          ORDER BY message.timecreated DESC";
    $params = array('userid1' => $user->id, 'userid2' => $user->id, 'userid3' => $user->id,
            'userid4' => $user->id, 'userid5' => $user->id, 'userid6' => $user->id);
    $read = $DB->get_records_sql($sql, $params, $limitfrom, $limitto);

    // We want to get the messages that have not been read. These are stored in the 'message' table. It is the
    // exact same query as the one above, except for the table we are querying. So, simply replace references to
    // the 'message_read' table with the 'message' table.
    $sql = str_replace('{message_read}', '{message}', $sql);
    $unread = $DB->get_records_sql($sql, $params, $limitfrom, $limitto);

    $conversations = array();

    // Union the 2 result sets together looking for the message with the most
    // recent timecreated for each other user.
    // $conversation->id (the array key) is the other user's ID.
    $conversation_arrays = array($unread, $read);
    foreach ($conversation_arrays as $conversation_array) {
        foreach ($conversation_array as $conversation) {
            if (empty($conversations[$conversation->id]) || $conversations[$conversation->id]->timecreated < $conversation->timecreated ) {
                $conversations[$conversation->id] = $conversation;
            }
        }
    }

    // Sort the conversations by $conversation->timecreated, newest to oldest
    // There may be multiple conversations with the same timecreated
    // The conversations array contains both read and unread messages (different tables) so sorting by ID won't work
    $result = core_collator::asort_objects_by_property($conversations, 'timecreated', core_collator::SORT_NUMERIC);
    $conversations = array_reverse($conversations);

    return $conversations;
}

/**
 * Get the users recent event notifications
 *
 * @param object $user the current user
 * @param int $limitfrom can be used for paging
 * @param int $limitto can be used for paging
 * @return array
 */
function message_get_recent_notifications($user, $limitfrom=0, $limitto=100) {
    global $DB;

    $userfields = user_picture::fields('u', array('lastaccess'));
    $sql = "SELECT mr.id AS message_read_id, $userfields, mr.notification, mr.smallmessage, mr.fullmessage, mr.fullmessagehtml, mr.fullmessageformat, mr.timecreated as timecreated, mr.contexturl, mr.contexturlname
              FROM {message_read} mr
                   JOIN {user} u ON u.id=mr.useridfrom
             WHERE mr.useridto = :userid1 AND u.deleted = '0' AND mr.notification = :notification
             ORDER BY mr.timecreated DESC";
    $params = array('userid1' => $user->id, 'notification' => 1);

    $notifications =  $DB->get_records_sql($sql, $params, $limitfrom, $limitto);
    return $notifications;
}

/**
 * Print the user's recent conversations
 *
 * @param stdClass $user the current user
 * @param bool $showicontext flag indicating whether or not to show text next to the action icons
 */
function message_print_recent_conversations($user1 = null, $showicontext = false, $showactionlinks = true) {
    global $USER;

    echo html_writer::start_tag('p', array('class' => 'heading'));
    echo get_string('mostrecentconversations', 'message');
    echo html_writer::end_tag('p');

    if (empty($user1)) {
        $user1 = $USER;
    }

    $conversations = message_get_recent_conversations($user1);

    // Attach context url information to create the "View this conversation" type links
    foreach($conversations as $conversation) {
        $conversation->contexturl = new moodle_url("/message/index.php?user1={$user1->id}&user2={$conversation->id}");
        $conversation->contexturlname = get_string('thisconversation', 'message');
    }

    $showotheruser = true;
    message_print_recent_messages_table($conversations, $user1, $showotheruser, $showicontext, false, $showactionlinks);
}

/**
 * Print the user's recent notifications
 *
 * @param stdClass $user the current user
 */
function message_print_recent_notifications($user=null) {
    global $USER;

    echo html_writer::start_tag('p', array('class' => 'heading'));
    echo get_string('mostrecentnotifications', 'message');
    echo html_writer::end_tag('p');

    if (empty($user)) {
        $user = $USER;
    }

    $notifications = message_get_recent_notifications($user);

    $showicontext = false;
    $showotheruser = false;
    message_print_recent_messages_table($notifications, $user, $showotheruser, $showicontext, true);
}

/**
 * Print a list of recent messages
 *
 * @access private
 *
 * @param array $messages the messages to display
 * @param stdClass $user the current user
 * @param bool $showotheruser display information on the other user?
 * @param bool $showicontext show text next to the action icons?
 * @param bool $forcetexttohtml Force text to go through @see text_to_html() via @see format_text()
 * @param bool $showactionlinks
 * @return void
 */
function message_print_recent_messages_table($messages, $user = null, $showotheruser = true, $showicontext = false, $forcetexttohtml = false, $showactionlinks = true) {
    global $OUTPUT;
    static $dateformat;

    if (empty($dateformat)) {
        $dateformat = get_string('strftimedatetimeshort');
    }

    echo html_writer::start_tag('div', array('class' => 'messagerecent'));
    foreach ($messages as $message) {
        echo html_writer::start_tag('div', array('class' => 'singlemessage'));

        if ($showotheruser) {
            $strcontact = $strblock = $strhistory = null;

            if ($showactionlinks) {
                if ( $message->contactlistid )  {
                    if ($message->blocked == 0) { // The other user isn't blocked.
                        $strcontact = message_contact_link($message->id, 'remove', true, null, $showicontext);
                        $strblock   = message_contact_link($message->id, 'block', true, null, $showicontext);
                    } else { // The other user is blocked.
                        $strcontact = message_contact_link($message->id, 'add', true, null, $showicontext);
                        $strblock   = message_contact_link($message->id, 'unblock', true, null, $showicontext);
                    }
                } else {
                    $strcontact = message_contact_link($message->id, 'add', true, null, $showicontext);
                    $strblock   = message_contact_link($message->id, 'block', true, null, $showicontext);
                }

                //should we show just the icon or icon and text?
                $histicontext = 'icon';
                if ($showicontext) {
                    $histicontext = 'both';
                }
                $strhistory = message_history_link($user->id, $message->id, true, '', '', $histicontext);
            }
            echo html_writer::start_tag('span', array('class' => 'otheruser'));

            echo html_writer::start_tag('span', array('class' => 'pix'));
            echo $OUTPUT->user_picture($message, array('size' => 20, 'courseid' => SITEID));
            echo html_writer::end_tag('span');

            echo html_writer::start_tag('span', array('class' => 'contact'));

            $link = new moodle_url("/message/index.php?user1={$user->id}&user2=$message->id");
            $action = null;
            echo $OUTPUT->action_link($link, fullname($message), $action, array('title' => get_string('sendmessageto', 'message', fullname($message))));

            echo html_writer::end_tag('span');//end contact

            if ($showactionlinks) {
                echo $strcontact.$strblock.$strhistory;
            }
            echo html_writer::end_tag('span');//end otheruser
        }

        $messagetext = message_format_message_text($message, $forcetexttohtml);

        echo html_writer::tag('span', userdate($message->timecreated, $dateformat), array('class' => 'messagedate'));
        echo html_writer::tag('span', $messagetext, array('class' => 'themessage'));
        echo message_format_contexturl($message);
        echo html_writer::end_tag('div');//end singlemessage
    }
    echo html_writer::end_tag('div');//end messagerecent
}

/**
 * Try to guess how to convert the message to html.
 *
 * @access private
 *
 * @param stdClass $message
 * @param bool $forcetexttohtml
 * @return string html fragment
 */
function message_format_message_text($message, $forcetexttohtml = false) {
    // Note: this is a very nasty hack that tries to work around the weird messaging rules and design.

    $options = new stdClass();
    $options->para = false;

    $format = $message->fullmessageformat;

    if ($message->smallmessage !== '') {
        if ($message->notification == 1) {
            if ($message->fullmessagehtml !== '' or $message->fullmessage !== '') {
                $format = FORMAT_PLAIN;
            }
        }
        $messagetext = $message->smallmessage;

    } else if ($message->fullmessageformat == FORMAT_HTML) {
        if ($message->fullmessagehtml !== '') {
            $messagetext = $message->fullmessagehtml;
        } else {
            $messagetext = $message->fullmessage;
            $format = FORMAT_MOODLE;
        }

    } else {
        if ($message->fullmessage !== '') {
            $messagetext = $message->fullmessage;
        } else {
            $messagetext = $message->fullmessagehtml;
            $format = FORMAT_HTML;
        }
    }

    if ($forcetexttohtml) {
        // This is a crazy hack, why not set proper format when creating the notifications?
        if ($format === FORMAT_PLAIN) {
            $format = FORMAT_MOODLE;
        }
    }
    return format_text($messagetext, $format, $options);
}

/**
 * Add the selected user as a contact for the current user
 *
 * @param int $contactid the ID of the user to add as a contact
 * @param int $blocked 1 if you wish to block the contact
 * @return bool/int false if the $contactid isnt a valid user id. True if no changes made.
 *                  Otherwise returns the result of update_record() or insert_record()
 */
function message_add_contact($contactid, $blocked=0) {
    global $USER, $DB;

    if (!$DB->record_exists('user', array('id' => $contactid))) { // invalid userid
        return false;
    }

    if (($contact = $DB->get_record('message_contacts', array('userid' => $USER->id, 'contactid' => $contactid))) !== false) {
    // A record already exists. We may be changing blocking status.

        if ($contact->blocked !== $blocked) {
            // Blocking status has been changed.
            $contact->blocked = $blocked;
            return $DB->update_record('message_contacts', $contact);
        } else {
            // No change to blocking status.
            return true;
        }

    } else {
        // New contact record.
        $contact = new stdClass();
        $contact->userid = $USER->id;
        $contact->contactid = $contactid;
        $contact->blocked = $blocked;
        return $DB->insert_record('message_contacts', $contact, false);
    }
}

/**
 * remove a contact
 *
 * @param int $contactid the user ID of the contact to remove
 * @return bool returns the result of delete_records()
 */
function message_remove_contact($contactid) {
    global $USER, $DB;
    return $DB->delete_records('message_contacts', array('userid' => $USER->id, 'contactid' => $contactid));
}

/**
 * Unblock a contact. Note that this reverts the previously blocked user back to a non-contact.
 *
 * @param int $contactid the user ID of the contact to unblock
 * @return bool returns the result of delete_records()
 */
function message_unblock_contact($contactid) {
    global $USER, $DB;
    return $DB->delete_records('message_contacts', array('userid' => $USER->id, 'contactid' => $contactid));
}

/**
 * block a user
 *
 * @param int $contactid the user ID of the user to block
 */
function message_block_contact($contactid) {
    return message_add_contact($contactid, 1);
}

/**
 * Load a user's contact record
 *
 * @param int $contactid the user ID of the user whose contact record you want
 * @return array message contacts
 */
function message_get_contact($contactid) {
    global $USER, $DB;
    return $DB->get_record('message_contacts', array('userid' => $USER->id, 'contactid' => $contactid));
}

/**
 * Print the results of a message search
 *
 * @param mixed $frm submitted form data
 * @param bool $showicontext show text next to action icons?
 * @param object $currentuser the current user
 * @return void
 */
function message_print_search_results($frm, $showicontext=false, $currentuser=null) {
    global $USER, $DB, $OUTPUT;

    if (empty($currentuser)) {
        $currentuser = $USER;
    }

    echo html_writer::start_tag('div', array('class' => 'mdl-left'));

    $personsearch = false;
    $personsearchstring = null;
    if (!empty($frm->personsubmit) and !empty($frm->name)) {
        $personsearch = true;
        $personsearchstring = $frm->name;
    } else if (!empty($frm->combinedsubmit) and !empty($frm->combinedsearch)) {
        $personsearch = true;
        $personsearchstring = $frm->combinedsearch;
    }

    // Search for person.
    if ($personsearch) {
        if (optional_param('mycourses', 0, PARAM_BOOL)) {
            $users = array();
            $mycourses = enrol_get_my_courses('id');
            $mycoursesids = array();
            foreach ($mycourses as $mycourse) {
                $mycoursesids[] = $mycourse->id;
            }
            $susers = message_search_users($mycoursesids, $personsearchstring);
            foreach ($susers as $suser) {
                $users[$suser->id] = $suser;
            }
        } else {
            $users = message_search_users(SITEID, $personsearchstring);
        }

        if (!empty($users)) {
            echo html_writer::start_tag('p', array('class' => 'heading searchresultcount'));
            echo get_string('userssearchresults', 'message', count($users));
            echo html_writer::end_tag('p');

            echo html_writer::start_tag('table', array('class' => 'messagesearchresults'));
            foreach ($users as $user) {

                if ( $user->contactlistid )  {
                    if ($user->blocked == 0) { // User is not blocked.
                        $strcontact = message_contact_link($user->id, 'remove', true, null, $showicontext);
                        $strblock   = message_contact_link($user->id, 'block', true, null, $showicontext);
                    } else { // blocked
                        $strcontact = message_contact_link($user->id, 'add', true, null, $showicontext);
                        $strblock   = message_contact_link($user->id, 'unblock', true, null, $showicontext);
                    }
                } else {
                    $strcontact = message_contact_link($user->id, 'add', true, null, $showicontext);
                    $strblock   = message_contact_link($user->id, 'block', true, null, $showicontext);
                }

                // Should we show just the icon or icon and text?
                $histicontext = 'icon';
                if ($showicontext) {
                    $histicontext = 'both';
                }
                $strhistory = message_history_link($USER->id, $user->id, true, '', '', $histicontext);

                echo html_writer::start_tag('tr');

                echo html_writer::start_tag('td', array('class' => 'pix'));
                echo $OUTPUT->user_picture($user, array('size' => 20, 'courseid' => SITEID));
                echo html_writer::end_tag('td');

                echo html_writer::start_tag('td',array('class' => 'contact'));
                $action = null;
                $link = new moodle_url("/message/index.php?id=$user->id");
                echo $OUTPUT->action_link($link, fullname($user), $action, array('title' => get_string('sendmessageto', 'message', fullname($user))));
                echo html_writer::end_tag('td');

                echo html_writer::tag('td', $strcontact, array('class' => 'link'));
                echo html_writer::tag('td', $strblock, array('class' => 'link'));
                echo html_writer::tag('td', $strhistory, array('class' => 'link'));

                echo html_writer::end_tag('tr');
            }
            echo html_writer::end_tag('table');

        } else {
            echo html_writer::start_tag('p', array('class' => 'heading searchresultcount'));
            echo get_string('userssearchresults', 'message', 0).'<br /><br />';
            echo html_writer::end_tag('p');
        }
    }

    // search messages for keywords
    $messagesearch = false;
    $messagesearchstring = null;
    if (!empty($frm->keywords)) {
        $messagesearch = true;
        $messagesearchstring = clean_text(trim($frm->keywords));
    } else if (!empty($frm->combinedsubmit) and !empty($frm->combinedsearch)) {
        $messagesearch = true;
        $messagesearchstring = clean_text(trim($frm->combinedsearch));
    }

    if ($messagesearch) {
        if ($messagesearchstring) {
            $keywords = explode(' ', $messagesearchstring);
        } else {
            $keywords = array();
        }
        $tome     = false;
        $fromme   = false;
        $courseid = 'none';

        if (empty($frm->keywordsoption)) {
            $frm->keywordsoption = 'allmine';
        }

        switch ($frm->keywordsoption) {
            case 'tome':
                $tome   = true;
                break;
            case 'fromme':
                $fromme = true;
                break;
            case 'allmine':
                $tome   = true;
                $fromme = true;
                break;
            case 'allusers':
                $courseid = SITEID;
                break;
            case 'courseusers':
                $courseid = $frm->courseid;
                break;
            default:
                $tome   = true;
                $fromme = true;
        }

        if (($messages = message_search($keywords, $fromme, $tome, $courseid)) !== false) {

            // Get a list of contacts.
            if (($contacts = $DB->get_records('message_contacts', array('userid' => $USER->id), '', 'contactid, blocked') ) === false) {
                $contacts = array();
            }

            // Print heading with number of results.
            echo html_writer::start_tag('p', array('class' => 'heading searchresultcount'));
            $countresults = count($messages);
            if ($countresults == MESSAGE_SEARCH_MAX_RESULTS) {
                echo get_string('keywordssearchresultstoomany', 'message', $countresults).' ("'.s($messagesearchstring).'")';
            } else {
                echo get_string('keywordssearchresults', 'message', $countresults);
            }
            echo html_writer::end_tag('p');

            // Print table headings.
            echo html_writer::start_tag('table', array('class' => 'messagesearchresults', 'cellspacing' => '0'));

            $headertdstart = html_writer::start_tag('td', array('class' => 'messagesearchresultscol'));
            $headertdend   = html_writer::end_tag('td');
            echo html_writer::start_tag('tr');
            echo $headertdstart.get_string('from').$headertdend;
            echo $headertdstart.get_string('to').$headertdend;
            echo $headertdstart.get_string('message', 'message').$headertdend;
            echo $headertdstart.get_string('timesent', 'message').$headertdend;
            echo html_writer::end_t…