Working for DST support.

[moodle.git] / lib / moodlelib.php

<?php // $Id$

///////////////////////////////////////////////////////////////////////////
//                                                                       //
// NOTICE OF COPYRIGHT                                                   //
//                                                                       //
// Moodle - Modular Object-Oriented Dynamic Learning Environment         //
//          http://moodle.org                                            //
//                                                                       //
// Copyright (C) 1999-2004  Martin Dougiamas  http://dougiamas.com       //
//                                                                       //
// This program 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 2 of the License, or     //
// (at your option) any later version.                                   //
//                                                                       //
// This program 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:                          //
//                                                                       //
//          http://www.gnu.org/copyleft/gpl.html                         //
//                                                                       //
///////////////////////////////////////////////////////////////////////////

/**
 * moodlelib.php - Moodle main library
 *
 * Main library file of miscellaneous general-purpose Moodle functions.
 * Other main libraries:
 *  - weblib.php      - functions that produce web output
 *  - datalib.php     - functions that access the database
 * @author Martin Dougiamas
 * @version $Id$
 * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
 * @package moodlecore
 */
/// CONSTANTS /////////////////////////////////////////////////////////////

/**
 * Used by some scripts to check they are being called by Moodle
 */
define('MOODLE_INTERNAL', true);


/**
 * No groups used?
 */
define('NOGROUPS', 0);

/**
 * Groups used?
 */
define('SEPARATEGROUPS', 1);

/**
 * Groups visible?
 */
define('VISIBLEGROUPS', 2);

/**
 * Time constant - the number of seconds in a week
 */
define('WEEKSECS', 604800);

/**
 * Time constant - the number of seconds in a day
 */
define('DAYSECS', 86400);

/**
 * Time constant - the number of seconds in an hour
 */
define('HOURSECS', 3600);

/**
 * Time constant - the number of seconds in a minute
 */
define('MINSECS', 60);

/**
 * Time constant - the number of minutes in a day
 */
define('DAYMINS', 1440);

/**
 * Time constant - the number of minutes in an hour
 */
define('HOURMINS', 60);

/**
 * Parameter constants - if set then the parameter is cleaned of scripts etc
 */
define('PARAM_RAW',     0x0000);
define('PARAM_CLEAN',   0x0001);
define('PARAM_INT',     0x0002);
define('PARAM_INTEGER', 0x0002);  // Alias for PARAM_INT
define('PARAM_ALPHA',   0x0004);
define('PARAM_ACTION',  0x0004);  // Alias for PARAM_ALPHA
define('PARAM_FORMAT',  0x0004);  // Alias for PARAM_ALPHA
define('PARAM_NOTAGS',  0x0008);
define('PARAM_FILE',    0x0010);
define('PARAM_PATH',    0x0020);
define('PARAM_HOST',    0x0040);  // FQDN or IPv4 dotted quad
define('PARAM_URL',     0x0080);  
define('PARAM_LOCALURL',0x0180);  // NOT orthogonal to the others! Implies PARAM_URL!
define('PARAM_CLEANFILE',0x0200);
define('PARAM_ALPHANUM',0x0400);  //numbers or letters only
define('PARAM_BOOL',    0x0800);  //convert to value 1 or 0 using empty()

/**
 * Definition of page types
 */
define('PAGE_COURSE_VIEW', 'course-view');

/// PARAMETER HANDLING ////////////////////////////////////////////////////

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET.  If the parameter doesn't exist then an error is
 * thrown because we require this variable.
 *
 * This function should be used to initialise all required values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $id = required_param('id');
 *
 * @param string $varname the name of the parameter variable we want
 * @param integer $options a bit field that specifies any cleaning needed
 * @return mixed
 */
function required_param($varname, $options=PARAM_CLEAN) {

    if (isset($_POST[$varname])) {       // POST has precedence
        $param = $_POST[$varname];
    } else if (isset($_GET[$varname])) {
        $param = $_GET[$varname];
    } else {
        error('A required parameter ('.$varname.') was missing');
    }

    return clean_param($param, $options);
}

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET, otherwise returning a given default.
 *
 * This function should be used to initialise all optional values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $name = optional_param('name', 'Fred');
 *
 * @param string $varname the name of the parameter variable we want
 * @param mixed  $default the default value to return if nothing is found
 * @param integer $options a bit field that specifies any cleaning needed
 * @return mixed
 */
function optional_param($varname, $default=NULL, $options=PARAM_CLEAN) {

    if (isset($_POST[$varname])) {       // POST has precedence
        $param = $_POST[$varname];
    } else if (isset($_GET[$varname])) {
        $param = $_GET[$varname];
    } else {
        return $default;
    }

    return clean_param($param, $options);
}

/**
 * Used by {@link optional_param()} and {@link required_param()} to
 * clean the variables and/or cast to specific types, based on
 * an options field.
 *
 * @param mixed $param the variable we are cleaning
 * @param integer $options a bit field that specifies the cleaning needed
 * @return mixed
 */
function clean_param($param, $options) {

    global $CFG;

    if (!$options) {
        return $param;                   // Return raw value
    }

    if ((string)$param == (string)(int)$param) {  // It's just an integer
        return (int)$param;
    }

    if ($options & PARAM_CLEAN) {
        $param = clean_text($param);     // Sweep for scripts, etc
    }

    if ($options & PARAM_INT) {
        $param = (int)$param;            // Convert to integer
    }

    if ($options & PARAM_ALPHA) {        // Remove everything not a-z
        $param = eregi_replace('[^a-zA-Z]', '', $param);
    }

    if ($options & PARAM_ALPHANUM) {     // Remove everything not a-zA-Z0-9
        $param = eregi_replace('[^A-Za-z0-9]', '', $param);
    }

    if ($options & PARAM_BOOL) {         // Convert to 1 or 0
        $param = empty($param) ? 0 : 1;
    }

    if ($options & PARAM_NOTAGS) {       // Strip all tags completely
        $param = strip_tags($param);
    }

    if ($options & PARAM_CLEANFILE) {    // allow only safe characters
        $param = clean_filename($param);
    }

    if ($options & PARAM_FILE) {         // Strip all suspicious characters from filename
        $param = ereg_replace('[[:cntrl:]]|[<>"`\|\':\\/]', '', $param);
        $param = ereg_replace('\.\.+', '', $param);
    }

    if ($options & PARAM_PATH) {         // Strip all suspicious characters from file path
        $param = str_replace('\\\'', '\'', $param);
        $param = str_replace('\\"', '"', $param);
        $param = str_replace('\\', '/', $param);
        $param = ereg_replace('[[:cntrl:]]|[<>"`\|\':]', '', $param);
        $param = ereg_replace('\.\.+', '', $param);
        $param = ereg_replace('//+', '/', $param);
    }

    if ($options & PARAM_HOST) {         // allow FQDN or IPv4 dotted quad
        preg_replace('/[^\.\d\w-]/','', $param ); // only allowed chars 
        // match ipv4 dotted quad
        if (preg_match('/(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/',$param, $match)){
            // confirm values are ok
            if ( $match[0] > 255
                 || $match[1] > 255
                 || $match[3] > 255 
                 || $match[4] > 255 ) {
                // hmmm, what kind of dotted quad is this?
                $param = '';
            }
        } elseif ( preg_match('/^[\w\d\.-]+$/', $param) // dots, hyphens, numbers
                   && !preg_match('/^[\.-]/',  $param) // no leading dots/hyphens
                   && !preg_match('/[\.-]$/',  $param) // no trailing dots/hyphens
                   ) {
            // all is ok - $param is respected
        } else {
            // all is not ok...
            $param='';               
        } 
    }

    if ($options & PARAM_URL) { // allow safe ftp, http, mailto urls

        include_once($CFG->dirroot . '/lib/validateurlsyntax.php');

        //
        // Parameters to validateurlsyntax()
        //
        // s? scheme is optional
        //   H? http optional
        //   S? https optional
        //   F? ftp   optional
        //   E? mailto optional
        // u- user section not allowed
        //   P- password not allowed
        // a? address optional
        //   I? Numeric IP address optional (can use IP or domain)
        //   p-  port not allowed -- restrict to default port
        // f? "file" path section optional
        //   q? query section optional
        //   r? fragment (anchor) optional
        //
        if (!empty($param) && validateUrlSyntax($param, 's?H?S?F?E?u-P-a?I?p-f?q?r?')) {
            // all is ok, param is respected
        } else {
            $param =''; // not really ok
        }
        $options ^= PARAM_URL; // Turn off the URL bit so that simple PARAM_URLs don't test true for PARAM_LOCALURL
    }

    if ($options & PARAM_LOCALURL) { 
        // assume we passed the PARAM_URL test...
        // allow http absolute, root relative and relative URLs within wwwroot
        if (!empty($param)) {
            if (preg_match(':^/:', $param)) { 
                // root-relative, ok!
            } elseif (preg_match('/^'.preg_quote($CFG->wwwroot, '/').'/i',$param)) {
                // absolute, and matches our wwwroot
            } else { 
                // relative - let's make sure there are no tricks
                if (validateUrlSyntax($param, 's-u-P-a-p-f+q?r?')) {
                    // looks ok.
                } else {
                    $param = '';
                }                
            }
        }
    }

    return $param;
}

/**
 * For security purposes, this function will check that the currently
 * given sesskey (passed as a parameter to the script or this function)
 * matches that of the current user.
 *
 * @param string $sesskey optionally provided sesskey
 * @return boolean
 */
function confirm_sesskey($sesskey=NULL) {
    global $USER;

    if (!empty($USER->ignoresesskey)) {
        return true;
    }

    if (empty($sesskey)) {
        $sesskey = required_param('sesskey');  // Check script parameters
    }

    if (!isset($USER->sesskey)) {
        return false;
    }

    return ($USER->sesskey === $sesskey);
}


/**
 * Ensure that a variable is set
 *
 * If $var is undefined throw an error, otherwise return $var.
 * This function will soon be made obsolete by {@link required_param()}
 *
 * @param mixed $var the variable which may be unset
 * @param mixed $default the value to return if $var is unset
 */
function require_variable($var) {
    if (! isset($var)) {
        error('A required parameter was missing');
    }
}


/**
 * Ensure that a variable is set
 *
 * If $var is undefined set it (by reference), otherwise return $var.
 * This function will soon be made obsolete by {@link optional_param()}
 *
 * @param mixed $var the variable which may be unset
 * @param mixed $default the value to return if $var is unset
 */
function optional_variable(&$var, $default=0) {
    if (! isset($var)) {
        $var = $default;
    }
}

/**
 * Set a key in global configuration
 *
 * Set a key/value pair in both this session's {@link $CFG} global variable
 * and in the 'config' database table for future sessions.
 *
 * @param string $name the key to set
 * @param string $value the value to set
 * @uses $CFG
 * @return bool
 */
function set_config($name, $value) {
/// No need for get_config because they are usually always available in $CFG

    global $CFG;


    $CFG->$name = $value;  // So it's defined for this invocation at least

    if (get_field('config', 'name', 'name', $name)) {
        return set_field('config', 'value', $value, 'name', $name);
    } else {
        $config->name = $name;
        $config->value = $value;
        return insert_record('config', $config);
    }
}

/**
 * Refresh current $USER session global variable with all their current preferences.
 * @uses $USER
 */
function reload_user_preferences() {

    global $USER;

    if(empty($USER) || empty($USER->id)) {
        return false;
    }

    unset($USER->preference);

    if ($preferences = get_records('user_preferences', 'userid', $USER->id)) {
        foreach ($preferences as $preference) {
            $USER->preference[$preference->name] = $preference->value;
        }
    } else {
            //return empty preference array to hold new values
            $USER->preference = array();
    }
}

/**
 * Sets a preference for the current user
 * Optionally, can set a preference for a different user object
 * @uses $USER
 * @todo Add a better description and include usage examples.
 * @param string $name The key to set as preference for the specified user
 * @param string $value The value to set forthe $name key in the specified user's record
 * @param int $userid A moodle user ID
 * @todo Add inline links to $USER and user functions in above line.
 * @return boolean
 */
function set_user_preference($name, $value, $otheruser=NULL) {

    global $USER;

    if (empty($otheruser)){
        if (!empty($USER) && !empty($USER->id)) {
            $userid = $USER->id;
        } else {
            return false;
        }
    } else {
        $userid = $otheruser;
    }

    if (empty($name)) {
        return false;
    }

    if ($preference = get_record('user_preferences', 'userid', $userid, 'name', $name)) {
        if (set_field('user_preferences', 'value', $value, 'id', $preference->id)) {
            if (empty($otheruser) and !empty($USER)) {
                $USER->preference[$name] = $value;
            }
            return true;
        } else {
            return false;
        }

    } else {
        $preference->userid = $userid;
        $preference->name   = $name;
        $preference->value  = (string)$value;
        if (insert_record('user_preferences', $preference)) {
            if (empty($otheruser) and !empty($USER)) {
                $USER->preference[$name] = $value;
            }
            return true;
        } else {
            return false;
        }
    }
}

/**
 * Unsets a preference completely by deleting it from the database
 * Optionally, can set a preference for a different user id
 * @uses $USER
 * @param string  $name The key to unset as preference for the specified user
 * @param int $userid A moodle user ID
 * @return boolean
 */
function unset_user_preference($name, $userid=NULL) {

    global $USER;

    if (empty($userid)){
        if(!empty($USER) && !empty($USER->id)) {
            $userid = $USER->id;
        }
        else {
            return false;
        }
    }

    return delete_records('user_preferences', 'userid', $userid, 'name', $name);
}


/**
 * Sets a whole array of preferences for the current user
 * @param array $prefarray An array of key/value pairs to be set
 * @param int $userid A moodle user ID
 * @return boolean
 */
function set_user_preferences($prefarray, $userid=NULL) {

    global $USER;

    if (!is_array($prefarray) or empty($prefarray)) {
        return false;
    }

    if (empty($userid)){
        if (!empty($USER) && !empty($USER->id)) {
            $userid = NULL;  // Continue with the current user below
        } else {
            return false;    // No-one to set!
        }
    }

    $return = true;
    foreach ($prefarray as $name => $value) {
        // The order is important; if the test for return is done first, then
        // if one function call fails all the remaining ones will be "optimized away"
        $return = set_user_preference($name, $value, $userid) and $return;
    }
    return $return;
}

/**
 * If no arguments are supplied this function will return
 * all of the current user preferences as an array.
 * If a name is specified then this function
 * attempts to return that particular preference value.  If
 * none is found, then the optional value $default is returned,
 * otherwise NULL.
 * @param string $name Name of the key to use in finding a preference value
 * @param string $default Value to be returned if the $name key is not set in the user preferences
 * @param int $userid A moodle user ID
 * @uses $USER
 * @return string
 */
function get_user_preferences($name=NULL, $default=NULL, $userid=NULL) {

    global $USER;

    if (empty($userid)) {   // assume current user
        if (empty($USER->preference)) {
            return $default;              // Default value (or NULL)
        }
        if (empty($name)) {
            return $USER->preference;     // Whole array
        }
        if (!isset($USER->preference[$name])) {
            return $default;              // Default value (or NULL)
        }
        return $USER->preference[$name];  // The single value

    } else {
        $preference = get_records_menu('user_preferences', 'userid', $userid, 'name', 'name,value');

        if (empty($name)) {
            return $preference;
        }
        if (!isset($preference[$name])) {
            return $default;              // Default value (or NULL)
        }
        return $preference[$name];        // The single value
    }
}


/// FUNCTIONS FOR HANDLING TIME ////////////////////////////////////////////

/**
 * Given date parts in user time produce a GMT timestamp.
 *
 * @param int $year The year part to create timestamp of.
 * @param int $month The month part to create timestamp of.
 * @param int $day The day part to create timestamp of.
 * @param int $hour The hour part to create timestamp of.
 * @param int $minute The minute part to create timestamp of.
 * @param int $second The second part to create timestamp of.
 * @param int $timezone ?
 * @return ?
 * @todo Finish documenting this function
 */
function make_timestamp($year, $month=1, $day=1, $hour=0, $minute=0, $second=0, $timezone=99, $applydst=true) {

    $timezone = get_user_timezone($timezone);

    if (abs($timezone) > 13) {
        $time = mktime((int)$hour,(int)$minute,(int)$second,(int)$month,(int)$day,(int)$year, 0);
    } else {
        $time = gmmktime((int)$hour,(int)$minute,(int)$second,(int)$month,(int)$day,(int)$year, 0);
        $time = usertime($time, $timezone);
    }

    if(!$applydst) {
        return $time;
    }

    if(($dstid = get_user_preferences('calendar_dstpreset')) !== NULL) {
        $preset = get_record('dst_preset', 'id', $dstid);

        if($time >= $preset->last_change && $time < $preset->next_change) {
            $time -= $preset->current_offset * 60;
            return $time;
        }

        // It's in some other time period, we need to recalculate
        $changes = calendar_dst_changes_for_year($year, $preset);

        if($time >= $changes['activate'] && $time < $changes['deactivate']) {
            // Compensation required
            $time -= $preset->apply_offset * $preset->apply_offset_sign;
        }
    }
    return $time;
}

/**
 * Given an amount of time in seconds, returns string
 * formatted nicely as months, days, hours etc as needed
 *
 * @uses MINSECS
 * @uses HOURSECS
 * @uses DAYSECS
 * @param int $totalsecs ?
 * @param array $str ?
 * @return string
 * @todo Finish documenting this function
 */
 function format_time($totalsecs, $str=NULL) {

    $totalsecs = abs($totalsecs);

    if (!$str) {  // Create the str structure the slow way
        $str->day   = get_string('day');
        $str->days  = get_string('days');
        $str->hour  = get_string('hour');
        $str->hours = get_string('hours');
        $str->min   = get_string('min');
        $str->mins  = get_string('mins');
        $str->sec   = get_string('sec');
        $str->secs  = get_string('secs');
    }

    $days      = floor($totalsecs/DAYSECS);
    $remainder = $totalsecs - ($days*DAYSECS);
    $hours     = floor($remainder/HOURSECS);
    $remainder = $remainder - ($hours*HOURSECS);
    $mins      = floor($remainder/MINSECS);
    $secs      = $remainder - ($mins*MINSECS);

    $ss = ($secs == 1)  ? $str->sec  : $str->secs;
    $sm = ($mins == 1)  ? $str->min  : $str->mins;
    $sh = ($hours == 1) ? $str->hour : $str->hours;
    $sd = ($days == 1)  ? $str->day  : $str->days;

    $odays = '';
    $ohours = '';
    $omins = '';
    $osecs = '';

    if ($days)  $odays  = $days .' '. $sd;
    if ($hours) $ohours = $hours .' '. $sh;
    if ($mins)  $omins  = $mins .' '. $sm;
    if ($secs)  $osecs  = $secs .' '. $ss;

    if ($days)  return $odays .' '. $ohours;
    if ($hours) return $ohours .' '. $omins;
    if ($mins)  return $omins .' '. $osecs;
    if ($secs)  return $osecs;
    return get_string('now');
}

/**
 * Returns a formatted string that represents a date in user time
 * <b>WARNING: note that the format is for strftime(), not date().</b>
 * Because of a bug in most Windows time libraries, we can't use
 * the nicer %e, so we have to use %d which has leading zeroes.
 * A lot of the fuss in the function is just getting rid of these leading
 * zeroes as efficiently as possible.
 *
 * If parameter fixday = true (default), then take off leading
 * zero from %d, else mantain it.
 *
 * @uses HOURSECS
 * @param  int $date ?
 * @param string $format ?
 * @param int $timezone ?
 * @param boolean $fixday If true (default) then the leading
 * zero from %d is removed. If false then the leading zero is mantained.
 * @return string
 * @todo Finish documenting this function
 */
function userdate($date, $format='', $timezone=99, $fixday = true) {

    if ($format == '') {
        $format = get_string('strftimedaydatetime');
    }

    $formatnoday = str_replace('%d', 'DD', $format);
    if ($fixday) {
        $fixday = ($formatnoday != $format);
    }

    $timezone = get_user_timezone($timezone);

    if (abs($timezone) > 13) {
        if ($fixday) {
            $datestring = strftime($formatnoday, $date);
            $daystring  = str_replace(' 0', '', strftime(" %d", $date));
            $datestring = str_replace('DD', $daystring, $datestring);
        } else {
            $datestring = strftime($format, $date);
        }
    } else {
        $date = $date + (int)($timezone * HOURSECS);
        if ($fixday) {
            $datestring = gmstrftime($formatnoday, $date);
            $daystring  = str_replace(' 0', '', gmstrftime(" %d", $date));
            $datestring = str_replace('DD', $daystring, $datestring);
        } else {
            $datestring = gmstrftime($format, $date);
        }
    }

    return $datestring;
}

/**
 * Given a $time timestamp in GMT (seconds since epoch),
 * returns an array that represents the date in user time
 *
 * @uses HOURSECS
 * @param int $time Timestamp in GMT
 * @param int $timezone ?
 * @return array An array that represents the date in user time
 * @todo Finish documenting this function
 */
function usergetdate($time, $timezone=99) {

    $timezone = get_user_timezone($timezone);

    if (abs($timezone) > 13) {
        return getdate($time);
    }
    //There is no gmgetdate so I have to fake it...
    $time += (int)($timezone * HOURSECS);

    // This is independent of the server's TZ settings,
    // unlike gmstrftime. It's also a bit faster this way.
    list(
        $getdate['seconds'],
        $getdate['minutes'],
        $getdate['hours'],
        $getdate['mday'],
        $getdate['mon'],
        $getdate['year'],
        $getdate['wday'],
        $getdate['yday'],
        $getdate['weekday'],
        $getdate['month']
    ) = explode(' ', gmdate('s i H d m Y w z l F', $time));

    return $getdate;
}

/**
 * Given a GMT timestamp (seconds since epoch), offsets it by
 * the timezone.  eg 3pm in India is 3pm GMT - 7 * 3600 seconds
 *
 * @uses HOURSECS
 * @param  int $date Timestamp in GMT
 * @param int $timezone ?
 * @return int
 * @todo Finish documenting this function
 */
function usertime($date, $timezone=99) {

    $timezone = get_user_timezone($timezone);
    if (abs($timezone) > 13) {
        return $date;
    }
    return $date - (int)($timezone * HOURSECS);
}

/**
 * Given a time, return the GMT timestamp of the most recent midnight
 * for the current user.
 *
 * @param  int $date Timestamp in GMT
 * @param int $timezone ?
 * @return ?
 * @todo Finish documenting this function. Is timezone an int or float?
 */
function usergetmidnight($date, $timezone=99) {

    $timezone = get_user_timezone($timezone);
    $userdate = usergetdate($date, $timezone);

    if (abs($timezone) > 13) {
        return mktime(0, 0, 0, $userdate['mon'], $userdate['mday'], $userdate['year']);
    }

    $timemidnight = gmmktime (0, 0, 0, $userdate['mon'], $userdate['mday'], $userdate['year']);
    return usertime($timemidnight, $timezone); // Time of midnight of this user's day, in GMT

}

/**
 * Returns a string that prints the user's timezone
 *
 * @param float $timezone The user's timezone
 * @return string
 * @todo is $timezone an int or a float?
 */
function usertimezone($timezone=99) {

    $timezone = get_user_timezone($timezone);

    if (abs($timezone) > 13) {
        return 'server time';
    }
    if (abs($timezone) < 0.5) {
        return 'GMT';
    }
    if ($timezone > 0) {
        return 'GMT+'. $timezone;
    } else {
        return 'GMT'. $timezone;
    }
}

/**
 * Returns a float which represents the user's timezone difference from GMT in hours
 * Checks various settings and picks the most dominant of those which have a value
 *
 * @uses $CFG
 * @uses $USER
 * @param int $tz The user's timezone
 * @return int
 * @todo is $tz an int or a float?
 */
function get_user_timezone($tz = 99) {

    // Variables declared explicitly global here so that if we add
    // something later we won't forget to global it...
    $timezones = array(
        isset($GLOBALS['USER']->timezone) ? $GLOBALS['USER']->timezone : 99,
        isset($GLOBALS['CFG']->timezone) ? $GLOBALS['CFG']->timezone : 99,
        );
    while($tz == 99 && $next = each($timezones)) {
        $tz = (float)$next['value'];
    }

    return $tz;
}

/// USER AUTHENTICATION AND LOGIN ////////////////////////////////////////

// Makes sure that $USER->sesskey exists, if $USER itself exists. It sets a new sesskey
// if one does not already exist, but does not overwrite existing sesskeys. Returns the
// sesskey string if $USER exists, or boolean false if not.
function sesskey() {
    global $USER;

    if(!isset($USER)) {
        return false;
    }

    if (empty($USER->sesskey)) {
        $USER->sesskey = random_string(10);
    }

    return $USER->sesskey;
}

/**
 * This function checks that the current user is logged in and has the
 * required privileges
 *
 * This function checks that the current user is logged in, and optionally
 * whether they are allowed to be in a particular course and view a particular
 * course module.
 * If they are not logged in, then it redirects them to the site login unless
 * $autologinguest is set and {@link $CFG}->autologinguests is set to 1 in which 
 * case they are automatically logged in as guests.
 * If $courseid is given and the user is not enrolled in that course then the
 * user is redirected to the course enrolment page.
 * If $cm is given and the coursemodule is hidden and the user is not a teacher
 * in the course then the user is redirected to the course home page.
 *
 * @uses $CFG
 * @uses $SESSION
 * @uses $USER
 * @uses $FULLME
 * @uses SITEID
 * @uses $MoodleSession
 * @param int $courseid id of the course
 * @param boolean $autologinguest 
 * @param $cm course module object
 */
function require_login($courseid=0, $autologinguest=true, $cm=null) {

    global $CFG, $SESSION, $USER, $FULLME, $MoodleSession;

    // First check that the user is logged in to the site.
    if (! (isset($USER->loggedin) and $USER->confirmed and ($USER->site == $CFG->wwwroot)) ) { // They're not
        $SESSION->wantsurl = $FULLME;
        if (!empty($_SERVER['HTTP_REFERER'])) {
            $SESSION->fromurl  = $_SERVER['HTTP_REFERER'];
        }
        $USER = NULL;
        if ($autologinguest and $CFG->autologinguests and $courseid and get_field('course','guest','id',$courseid)) {
            $loginguest = '?loginguest=true';
        } else {
            $loginguest = '';
        }
        if (empty($CFG->loginhttps)) {
            redirect($CFG->wwwroot .'/login/index.php'. $loginguest);
        } else {
            $wwwroot = str_replace('http','https', $CFG->wwwroot);
            redirect($wwwroot .'/login/index.php'. $loginguest);
        }
        die;
    }

    // check whether the user should be changing password
    // reload_user_preferences();    // Why is this necessary?  Seems wasteful.  - MD
    if (!empty($USER->preference['auth_forcepasswordchange'])){
        if (is_internal_auth() || $CFG->{'auth_'.$USER->auth.'_stdchangepassword'}){
            redirect($CFG->wwwroot .'/login/change_password.php');
        } elseif($CFG->changepassword) {
            redirect($CFG->changepassword);
        } else {
            error('You cannot proceed without changing your password.
                   However there is no available page for changing it.
                   Please contact your Moodle Administrator.');
        }
    }
    // Check that the user account is properly set up
    if (user_not_fully_set_up($USER)) {
        redirect($CFG->wwwroot .'/user/edit.php?id='. $USER->id .'&amp;course='. SITEID);
        die;
    }

    // Make sure current IP matches the one for this session (if required)
    if (!empty($CFG->tracksessionip)) {
        if ($USER->sessionIP != md5(getremoteaddr())) {
            error(get_string('sessionipnomatch', 'error'));
        }
    }

    // Make sure the USER has a sesskey set up.  Used for checking script parameters.
    sesskey();

    // Check that the user has agreed to a site policy if there is one
    if (!empty($CFG->sitepolicy)) {
        if (!$USER->policyagreed) {
            $SESSION->wantsurl = $FULLME;
            redirect($CFG->wwwroot .'/user/policy.php');
            die;
        }
    }

    // If the site is currently under maintenance, then print a message
    if (!isadmin()) {
        if (file_exists($CFG->dataroot.'/1/maintenance.html')) {
            print_maintenance_message();
            die;
        }
    }

    // Next, check if the user can be in a particular course
    if ($courseid) {
        if ($courseid == SITEID) { // Anyone can be in the site course
            if (isset($cm) and !$cm->visible and !isteacher(SITEID)) { // Not allowed to see module, send to course page
                redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course, get_string('activityiscurrentlyhidden'));
            }
            return;   
        }
        if (!empty($USER->student[$courseid]) or !empty($USER->teacher[$courseid]) or !empty($USER->admin)) {
            if (isset($USER->realuser)) {   // Make sure the REAL person can also access this course
                if (!isteacher($courseid, $USER->realuser)) {
                    print_header();
                    notice(get_string('studentnotallowed', '', fullname($USER, true)), $CFG->wwwroot .'/');
                }
            }
            if (isset($cm) and !$cm->visible and !isteacher($courseid)) { // Not allowed to see module, send to course page
                redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course, get_string('activityiscurrentlyhidden'));
            }
            return;   // user is a member of this course.
        }
        if (! $course = get_record('course', 'id', $courseid)) {
            error('That course doesn\'t exist');
        }
        if (!$course->visible) {
            print_header();
            notice(get_string('coursehidden'), $CFG->wwwroot .'/');
        }
        if ($USER->username == 'guest') {
            switch ($course->guest) {
                case 0: // Guests not allowed
                    print_header();
                    notice(get_string('guestsnotallowed', '', $course->fullname), "$CFG->wwwroot/login/index.php");
                    break;
                case 1: // Guests allowed
                    if (isset($cm) and !$cm->visible) { // Not allowed to see module, send to course page
                        redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course, get_string('activityiscurrentlyhidden'));
                    }
                    return;
                case 2: // Guests allowed with key (drop through)
                    break;
            }
        }

        //User is not enrolled in the course, wants to access course content
        //as a guest, and course setting allow unlimited guest access
        //Code cribbed from course/loginas.php
        if (strstr($FULLME,"username=guest") && ($course->guest==1)) {
            $realuser = $USER->id;
            $realname = fullname($USER, true);
            $USER = guest_user();
            $USER->loggedin = true;
            $USER->site = $CFG->wwwroot;
            $USER->realuser = $realuser;
            if (isset($SESSION->currentgroup[$course->id])) {    // Remember current setting for later
                $SESSION->oldcurrentgroup = $SESSION->currentgroup[$course->id];
                unset($SESSION->currentgroup[$course->id]);
            }
            $guest_name = fullname($USER, true);
            add_to_log($course->id, "course", "loginas", "../user/view.php?id=$course->id&$USER->id$", "$realname -> $guest_name");
            if (isset($cm) and !$cm->visible) { // Not allowed to see module, send to course page
                redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course, get_string('activityiscurrentlyhidden'));
            }
            return;
        }

        // Currently not enrolled in the course, so see if they want to enrol
        $SESSION->wantsurl = $FULLME;
        redirect($CFG->wwwroot .'/course/enrol.php?id='. $courseid);
        die;
    }
}

/**
 * This is a weaker version of {@link require_login()} which only requires login
 * when called from within a course rather than the site page, unless
 * the forcelogin option is turned on.
 *
 * @uses $CFG
 * @param int $courseid The course in question
 * @param boolean $autologinguest Allow autologin guests if that is wanted
 */
function require_course_login($course, $autologinguest=true, $cm=null) {
    global $CFG;
    if ($CFG->forcelogin) {
        require_login();
    }
    if ($course->category) {
        require_login($course->id, $autologinguest, $cm);
    }
}

/**
 * Modify the user table by setting the currently logged in user's
 * last login to now.
 *
 * @uses $USER
 * @return boolean
 */
function update_user_login_times() {
    global $USER;

    $USER->lastlogin = $user->lastlogin = $USER->currentlogin;
    $USER->currentlogin = $user->lastaccess = $user->currentlogin = time();

    $user->id = $USER->id;

    return update_record('user', $user);
}

/**
 * Determines if a user has completed setting up their account.
 *
 * @param user $user A {@link $USER} object to test for the existance of a valid name and email
 * @return boolean
 */
function user_not_fully_set_up($user) {
    return ($user->username != 'guest' and (empty($user->firstname) or empty($user->lastname) or empty($user->email) or over_bounce_threshold($user)));
}

function over_bounce_threshold($user) {
    
    global $CFG;
    
    if (empty($CFG->handlebounces)) {
        return false;
    }
    // set sensible defaults
    if (empty($CFG->minbounces)) {
        $CFG->minbounces = 10;
    }
    if (empty($CFG->bounceratio)) {
        $CFG->bounceratio = .20;
    }
    $bouncecount = 0;
    $sendcount = 0;
    if ($bounce = get_record('user_preferences','userid',$user->id,'name','email_bounce_count')) {
        $bouncecount = $bounce->value;
    }
    if ($send = get_record('user_preferences','userid',$user->id,'name','email_send_count')) {
        $sendcount = $send->value;
    }
    return ($bouncecount >= $CFG->minbounces && $bouncecount/$sendcount >= $CFG->bounceratio);
}

/** 
 * @param $user - object containing an id
 * @param $reset - will reset the count to 0
 */
function set_send_count($user,$reset=false) {
    if ($pref = get_record('user_preferences','userid',$user->id,'name','email_send_count')) {  
        $pref->value = (!empty($reset)) ? 0 : $pref->value+1;
        update_record('user_preferences',$pref);
    }
    else if (!empty($reset)) { // if it's not there and we're resetting, don't bother.
        // make a new one
        $pref->name = 'email_send_count';
        $pref->value = 1;
        $pref->userid = $user->id;
        insert_record('user_preferences',$pref);
    }
}

/** 
* @param $user - object containing an id
 * @param $reset - will reset the count to 0
 */
function set_bounce_count($user,$reset=false) {
    if ($pref = get_record('user_preferences','userid',$user->id,'name','email_bounce_count')) {    
        $pref->value = (!empty($reset)) ? 0 : $pref->value+1;
        update_record('user_preferences',$pref);
    }
    else if (!empty($reset)) { // if it's not there and we're resetting, don't bother.
        // make a new one
        $pref->name = 'email_bounce_count';
        $pref->value = 1;
        $pref->userid = $user->id;
        insert_record('user_preferences',$pref);
    }
}

/**
 * Keeps track of login attempts
 *
 * @uses $SESSION
 */
function update_login_count() {

    global $SESSION;

    $max_logins = 10;

    if (empty($SESSION->logincount)) {
        $SESSION->logincount = 1;
    } else {
        $SESSION->logincount++;
    }

    if ($SESSION->logincount > $max_logins) {
        unset($SESSION->wantsurl);
        error(get_string('errortoomanylogins'));
    }
}

/**
 * Resets login attempts
 *
 * @uses $SESSION
 */
function reset_login_count() {
    global $SESSION;

    $SESSION->logincount = 0;
}

/**
 * check_for_restricted_user
 *
 * @uses $CFG
 * @uses $USER
 * @param string $username ?
 * @param string $redirect ?
 * @todo Finish documenting this function
 */
function check_for_restricted_user($username=NULL, $redirect='') {
    global $CFG, $USER;

    if (!$username) {
        if (!empty($USER->username)) {
            $username = $USER->username;
        } else {
            return false;
        }
    }

    if (!empty($CFG->restrictusers)) {
        $names = explode(',', $CFG->restrictusers);
        if (in_array($username, $names)) {
            error(get_string('restricteduser', 'error', fullname($USER)), $redirect);
        }
    }
}

function sync_metacourses() {

    global $CFG;

    if (!$courses = get_records_sql("SELECT DISTINCT parent_course,1 FROM {$CFG->prefix}course_meta")) {
        return;
    }
    
    foreach ($courses as $course) {
        sync_metacourse($course->parent_course);
    }
}


/**
 * Goes through all enrolment records for the courses inside the metacourse and sync with them.
 */ 

function sync_metacourse($metacourseid) {

    global $CFG;

    if (!$metacourse = get_record("course","id",$metacourseid)) {
        return false;
    }


    if (count_records('course_meta','parent_course',$metacourseid) == 0) { // if there are no child courses for this meta course, nuke the enrolments
        if ($enrolments = get_records('user_students','course',$metacourseid,'','userid,1')) {
            foreach ($enrolments as $enrolment) {
                unenrol_student($enrolment->userid,$metacourseid);
            }
        }
        return true;
    }


    // this will return a list of userids from user_student for enrolments in the metacourse that shouldn't be there.
    $sql = "SELECT DISTINCT parent.userid,1 
            FROM {$CFG->prefix}course_meta meta 
              JOIN {$CFG->prefix}user_students parent 
                ON meta.parent_course = parent.course 
              LEFT OUTER JOIN {$CFG->prefix}user_students child
                ON meta.child_course = child.course 
                AND child.userid = parent.userid
                WHERE child.course IS NULL
                AND meta.parent_course = $metacourseid";

    if ($enrolmentstodelete = get_records_sql($sql)) {
        foreach ($enrolmentstodelete as $enrolment) {
            unenrol_student($enrolment->userid,$metacourseid); // doing it this way for forum subscriptions etc.
        }
    }


    // this will return a list of userids that need to be enrolled in the metacourse
    $sql = "SELECT DISTINCT child.userid,1 
            FROM {$CFG->prefix}course_meta meta 
              JOIN {$CFG->prefix}user_students child 
                 ON meta.child_course = child.course 
              LEFT OUTER JOIN {$CFG->prefix}user_students parent 
                 ON meta.parent_course = parent.course 
                 AND parent.userid = child.userid
                 WHERE parent.course IS NULL 
                 AND meta.parent_course = $metacourseid";

    if ($userstoadd = get_records_sql($sql)) {
        foreach ($userstoadd as $user) {
            enrol_student($user->userid,$metacourseid);
        }
    }
    
    // and next make sure that we have the right start time and end time (ie max and min) for them all.
    if ($enrolments = get_records('user_students','course',$metacourseid,'','id,userid')) {
        foreach ($enrolments as $enrol) {
            if ($maxmin = get_record_sql("SELECT min(timestart) AS timestart, max(timeend) AS timeend
               FROM {$CFG->prefix}user_students u JOIN {$CFG->prefix}course_meta mc ON u.course = mc.child_course WHERE userid = $enrol->userid
               AND mc.parent_course = $metacourseid")) {
                $enrol->timestart = $maxmin->timestart;
                $enrol->timeend = $maxmin->timeend;
                update_record('user_students',$enrol);
            }
        }
    }
    return true;
}

/** 
 * Adds a record to the metacourse table and calls sync_metacoures
 */
function add_to_metacourse ($metacourseid, $courseid) {
 
    if (!$metacourse = get_record("course","id",$metacourseid)) {
        return false;
    }
    
    if (!$course = get_record("course","id",$courseid)) {
        return false;
    }

    if (!$record = get_record("course_meta","parent_course",$metacourseid,"child_course",$courseid)) {
        $rec->parent_course = $metacourseid;
        $rec->child_course = $courseid;
        if (!insert_record('course_meta',$rec)) {
            return false;
        }
        return sync_metacourse($metacourseid);
    }
    return true;
   
}

/** 
 * Removes the record from the metacourse table and calls sync_metacourse
 */
function remove_from_metacourse($metacourseid, $courseid) {

    if (delete_records('course_meta','parent_course',$metacourseid,'child_course',$courseid)) {
        return sync_metacourse($metacourseid);
    }
    return false;
}


/**
 * Determines if a user an admin
 *
 * @uses $USER
 * @param int $userid The id of the user as is found in the 'user' table
 * @staticvar array $admin ?
 * @staticvar array $nonadmins ?
 * @return boolean
 * @todo Complete documentation for this function
 */
function isadmin($userid=0) {
    global $USER;
    static $admins = array();
    static $nonadmins = array();

    if (!$userid){
        if (empty($USER->id)) {
            return false;
        }
        $userid = $USER->id;
    }

    if (in_array($userid, $admins)) {
        return true;
    } else if (in_array($userid, $nonadmins)) {
        return false;
    } else if (record_exists('user_admins', 'userid', $userid)){
        $admins[] = $userid;
        return true;
    } else {
        $nonadmins[] = $userid;
        return false;
    }
}

/**
 * Determines if a user is a teacher or an admin
 *
 * @uses $USER
 * @param int $courseid The id of the course that is being viewed, if any
 * @param int $userid The id of the user that is being tested against. Set this to 0 if you would just like to test against the currently logged in user.
 * @param boolean $includeadmin If true this function will return true when it encounters an admin user.
 * @return boolean
 * @todo Finish documenting this function
 */
function isteacher($courseid=0, $userid=0, $includeadmin=true) {
/// Is the user a teacher or admin?
    global $USER, $CFG;

    if ($includeadmin and isadmin($userid)) {  // admins can do anything the teacher can
        return true;
    }

    if (empty($courseid)) {
        if (isadmin() or $CFG->debug > 7) {
            notify('Coding error: isteacher() should not be used without a valid course id as argument.  Please notify a developer.');
        }
        return isteacherinanycourse($userid, $includeadmin);
    }

    if (!$userid) {
        if ($courseid) {
            return !empty($USER->teacher[$courseid]);
        }
        if (!isset($USER->id)) {
            return false;
        }
        $userid = $USER->id;
    }

    return record_exists('user_teachers', 'userid', $userid, 'course', $courseid);
}

/**
 * Determines if a user is a teacher in any course, or an admin
 *
 * @uses $USER
 * @param int $userid The id of the user that is being tested against. Set this to 0 if you would just like to test against the currently logged in user.
 * @param boolean $includeadmin If true this function will return true when it encounters an admin user.
 * @return boolean
 * @todo Finish documenting this function
 */
function isteacherinanycourse($userid = 0, $includeadmin = true) {
    global $USER;

    if(empty($userid)) {
        if(empty($USER) || empty($USER->id)) {
            return false;
        }
        $userid = $USER->id;
    }

    if (isadmin($userid) && $includeadmin) {  // admins can do anything
        return true;
    }

    return record_exists('user_teachers', 'userid', $userid);
}

/**
 * Determines if a user is allowed to edit a given course
 *
 * @uses $USER
 * @param int $courseid The id of the course that is being edited
 * @param int $userid The id of the user that is being tested against. Set this to 0 if you would just like to test against the currently logged in user.
 * @return boolean
 */
function isteacheredit($courseid, $userid=0) {
    global $USER;

    if (isadmin($userid)) {  // admins can do anything
        return true;
    }

    if (!$userid) {
        return !empty($USER->teacheredit[$courseid]);
    }

    return get_field('user_teachers', 'editall', 'userid', $userid, 'course', $courseid);
}

/**
 * Determines if a user can create new courses
 *
 * @uses $USER
 * @param int $userid The user being tested. You can set this to 0 or leave it blank to test the currently logged in user.
 * @return boolean
 */
function iscreator ($userid=0) {
    global $USER;
    if (empty($USER->id)) {
        return false;
    }
    if (isadmin($userid)) {  // admins can do anything
        return true;
    }
    if (empty($userid)) {
        return record_exists('user_coursecreators', 'userid', $USER->id);
    }

    return record_exists('user_coursecreators', 'userid', $userid);
}

/**
 * Determines if a user is a student in the specified course
 *
 * If the course id specifies the site then the function determines
 * if the user is a confirmed and valid user of this site.
 *
 * @uses $USER
 * @uses $CFG
 * @uses SITEID
 * @param int $courseid The id of the course being tested
 * @param int $userid The user being tested. You can set this to 0 or leave it blank to test the currently logged in user.
 * @return boolean
 */
function isstudent($courseid, $userid=0) {
    global $USER, $CFG;

    if (empty($USER->id) and !$userid) {
        return false;
    }

    if ($courseid == SITEID) {
        if (!$userid) {
            $userid = $USER->id;
        }
        if (isguest($userid)) {
            return false;
        }
        // a site teacher can never be a site student
        if (isteacher($courseid, $userid)) {
            return false;
        }
        if ($CFG->allusersaresitestudents) {
            return record_exists('user', 'id', $userid);
        } else {
            return (record_exists('user_students', 'userid', $userid)
                     or record_exists('user_teachers', 'userid', $userid));
        }
    }

    if (!$userid) {
        return !empty($USER->student[$courseid]);
    }

  //  $timenow = time();   // todo:  add time check below

    return record_exists('user_students', 'userid', $userid, 'course', $courseid);
}

/**
 * Determines if the specified user is logged in as guest.
 *
 * @uses $USER
 * @param int $userid The user being tested. You can set this to 0 or leave it blank to test the currently logged in user.
 * @return boolean
 */
function isguest($userid=0) {
    global $USER;

    if (!$userid) {
        if (empty($USER->username)) {
            return false;
        }
        return ($USER->username == 'guest');
    }

    return record_exists('user', 'id', $userid, 'username', 'guest');
}

/**
 * Determines if the currently logged in user is in editing mode
 *
 * @uses $USER
 * @param int $courseid The id of the course being tested
 * @param user $user A {@link $USER} object. If null then the currently logged in user is used.
 * @return boolean
 */
function isediting($courseid, $user=NULL) {
    global $USER;
    if (!$user){
        $user = $USER;
    }
    if (empty($user->editing)) {
        return false;
    }
    return ($user->editing and isteacher($courseid, $user->id));
}

/**
 * Determines if the logged in user is currently moving an activity
 *
 * @uses $USER
 * @param int $courseid The id of the course being tested
 * @return boolean
 */
function ismoving($courseid) {
    global $USER;

    if (!empty($USER->activitycopy)) {
        return ($USER->activitycopycourse == $courseid);
    }
    return false;
}

/**
 * Given an object containing firstname and lastname
 * values, this function returns a string with the
 * full name of the person.
 * The result may depend on system settings
 * or language.  'override' will force both names
 * to be used even if system settings specify one.
 * @uses $CFG
 * @uses $SESSION
 * @param    type description
 * @todo Finish documenting this function
 */
function fullname($user, $override=false) {

    global $CFG, $SESSION;

    if (!isset($user->firstname) and !isset($user->lastname)) {
        return '';
    }

    if (!empty($SESSION->fullnamedisplay)) {
        $CFG->fullnamedisplay = $SESSION->fullnamedisplay;
    }

    if ($CFG->fullnamedisplay == 'firstname lastname') {
        return $user->firstname .' '. $user->lastname;

    } else if ($CFG->fullnamedisplay == 'lastname firstname') {
        return $user->lastname .' '. $user->firstname;

    } else if ($CFG->fullnamedisplay == 'firstname') {
        if ($override) {
            return get_string('fullnamedisplay', '', $user);
        } else {
            return $user->firstname;
        }
    }

    return get_string('fullnamedisplay', '', $user);
}

/**
 * Sets a moodle cookie with an encrypted string
 *
 * @uses $CFG
 * @uses DAYSECS
 * @uses HOURSECS
 * @param string $thing The string to encrypt and place in a cookie
 */
function set_moodle_cookie($thing) {
    global $CFG;

    $cookiename = 'MOODLEID_'.$CFG->sessioncookie;

    $days = 60;
    $seconds = DAYSECS*$days;

    setCookie($cookiename, '', time() - HOURSECS, '/');
    setCookie($cookiename, rc4encrypt($thing), time()+$seconds, '/');
}

/**
 * Gets a moodle cookie with an encrypted string
 *
 * @uses $CFG
 * @return string
 */
function get_moodle_cookie() {
    global $CFG;

    $cookiename = 'MOODLEID_'.$CFG->sessioncookie;

    if (empty($_COOKIE[$cookiename])) {
        return '';
    } else {
        return rc4decrypt($_COOKIE[$cookiename]);
    }
}

/**
 * Returns true if an internal authentication method is being used.
 * if method not specified then, global default is assumed
 *
 * @uses $CFG
 * @param string $auth Form of authentication required
 * @return boolean
 * @todo Outline auth types and provide code example
 */
function is_internal_auth($auth='') {
/// Returns true if an internal authentication method is being used.
/// If auth not specified then global default is assumed

    global $CFG;

    if (empty($auth)) {
        $auth = $CFG->auth;
    }

    return ($auth == "email" || $auth == "none" || $auth == "manual");
}

/**
 * Returns an array of user fields
 *
 * @uses $CFG
 * @uses $db
 * @return array User field/column names
 * @todo Finish documenting this function
 */
function get_user_fieldnames() {

    global $CFG, $db;

    $fieldarray = $db->MetaColumnNames($CFG->prefix.'user');
    unset($fieldarray['ID']);

    return $fieldarray;
}

/**
 * Creates a bare-bones user record
 *
 * @uses $CFG
 * @param string $username New user's username to add to record
 * @param string $password New user's password to add to record
 * @param string $auth Form of authentication required
 * @return user A {@link $USER} object
 * @todo Outline auth types and provide code example
 */
function create_user_record($username, $password, $auth='') {
    global $CFG;

    //just in case check text case
    $username = trim(moodle_strtolower($username));

    if (function_exists('auth_get_userinfo')) {
        if ($newinfo = auth_get_userinfo($username)) {
            $newinfo = truncate_userinfo($newinfo);
            foreach ($newinfo as $key => $value){
                $newuser->$key = addslashes(stripslashes($value)); // Just in case
            }
        }
    }

    if (!empty($newuser->email)) {
        if (email_is_not_allowed($newuser->email)) {
            unset($newuser->email);
        }
    }

    $newuser->auth = (empty($auth)) ? $CFG->auth : $auth;
    $newuser->username = $username;
    $newuser->password = md5($password);
    $newuser->lang = $CFG->lang;
    $newuser->confirmed = 1;
    $newuser->lastIP = getremoteaddr();
    $newuser->timemodified = time();

    if (insert_record('user', $newuser)) {
         $user = get_user_info_from_db('username', $newuser->username);
         if($CFG->{'auth_'.$newuser->auth.'_forcechangepassword'}){
             set_user_preference('auth_forcepasswordchange', 1, $user);
         }
         return $user;
    }
    return false;
}

/**
 * Will update a local user record from an external source
 *
 * @uses $CFG
 * @param string $username New user's username to add to record
 * @return user A {@link $USER} object
 */
function update_user_record($username) {
    global $CFG;

    if (function_exists('auth_get_userinfo')) {
        $username = trim(moodle_strtolower($username)); /// just in case check text case

        if ($newinfo = auth_get_userinfo($username)) {
            foreach ($newinfo as $key => $value){
                if (!empty($CFG->{'auth_user_' . $key. '_updatelocal'})) {
                    $value = addslashes(stripslashes($value));   // Just in case
                    set_field('user', $key, $value, 'username', $username);
                }
            }
        }
    }
    return get_user_info_from_db('username', $username);
}

function truncate_userinfo($info) {
/// will truncate userinfo as it comes from auth_get_userinfo (from external auth)
/// which may have large fields

    // define the limits
    $limit = array(
                    'username'    => 100,
                    'idnumber'    =>  64,
                    'firstname'   =>  20,
                    'lastname'    =>  20,
                    'email'       => 100,
                    'icq'         =>  15,
                    'phone1'      =>  20,
                    'phone2'      =>  20,
                    'institution' =>  40,
                    'department'  =>  30,
                    'address'     =>  70,
                    'city'        =>  20,
                    'country'     =>   2,
                    'url'         => 255,
                    );

    // apply where needed
    foreach (array_keys($info) as $key) {
        if (!empty($limit[$key])) {
            $info[$key] = trim(substr($info[$key],0, $limit[$key]));
        }
    }

    return $info;
}

/**
 * Retrieve the guest user object
 *
 * @uses $CFG
 * @return user A {@link $USER} object
 */
function guest_user() {
    global $CFG;

    if ($newuser = get_record('user', 'username', 'guest')) {
        $newuser->loggedin = true;
        $newuser->confirmed = 1;
        $newuser->site = $CFG->wwwroot;
        $newuser->lang = $CFG->lang;
        $newuser->lastIP = getremoteaddr();
    }

    return $newuser;
}

/**
 * Given a username and password, this function looks them
 * up using the currently selected authentication mechanism,
 * and if the authentication is successful, it returns a
 * valid $user object from the 'user' table.
 *
 * Uses auth_ functions from the currently active auth module
 *
 * @uses $CFG
 * @param string $username  User's username
 * @param string $password  User's password
 * @return user|flase A {@link $USER} object or false if error
 */
function authenticate_user_login($username, $password) {

    global $CFG;

    $md5password = md5($password);

    // First try to find the user in the database

    if (!$user = get_user_info_from_db('username', $username)) {
        $user->id = 0;     // Not a user
        $user->auth = $CFG->auth;
    }

    // Sort out the authentication method we are using.

    if (empty($CFG->auth)) {
        $CFG->auth = 'manual';     // Default authentication module
    }

    if (empty($user->auth)) {      // For some reason it isn't set yet
        if (isadmin($user->id) or isguest($user->id)) {
            $auth = 'manual';    // Always assume these guys are internal
        } else {
            $auth = $CFG->auth;  // Normal users default to site method
        }
        // update user record from external DB
        if ($user->auth != 'manual' && $user->auth != 'email') {
            $user = update_user_record($username);
        }
    } else {
        $auth = $user->auth;
    }

    if (detect_munged_arguments($auth, 0)) {   // For safety on the next require
        return false;
    }

    if (!file_exists($CFG->dirroot .'/auth/'. $auth .'/lib.php')) {
        $auth = 'manual';    // Can't find auth module, default to internal
    }

    require_once($CFG->dirroot .'/auth/'. $auth .'/lib.php');

    if (auth_user_login($username, $password)) {  // Successful authentication
        if ($user) {                              // User already exists in database
            if (empty($user->auth)) {             // For some reason auth isn't set yet
                set_field('user', 'auth', $auth, 'username', $username);
            }
            if ($md5password <> $user->password) {   // Update local copy of password for reference
                set_field('user', 'password', $md5password, 'username', $username);
            }
            if (!is_internal_auth()) {            // update user record from external DB
                $user = update_user_record($username);
            }
        } else {
            $user = create_user_record($username, $password, $auth);
        }

        if (function_exists('auth_iscreator')) {    // Check if the user is a creator
            $useriscreator = auth_iscreator($username);
            if (!is_null($useriscreator)) {
                if ($useriscreator) {
                    if (! record_exists('user_coursecreators', 'userid', $user->id)) {
                        $cdata->userid = $user->id;
                        if (! insert_record('user_coursecreators', $cdata)) {
                            error('Cannot add user to course creators.');
                        }
                    }
                } else {
                    if (record_exists('user_coursecreators', 'userid', $user->id)) {
                        if (! delete_records('user_coursecreators', 'userid', $user->id)) {
                            error('Cannot remove user from course creators.');
                        }
                    }
                }
            }
        }
        $user->sessionIP = md5(getremoteaddr());   // Store the current IP in the session
        return $user;

    } else {
        add_to_log(0, 'login', 'error', $_SERVER['HTTP_REFERER'], $username);
        error_log('[client '.$_SERVER['REMOTE_ADDR']."]\t$CFG->wwwroot\tFailed Login:\t$username\t".$_SERVER['HTTP_USER_AGENT']);
        return false;
    }
}

/**
 * Enrols (or re-enrols) a student in a given course
 *
 * @param int $courseid The id of the course that is being viewed
 * @param int $userid The id of the user that is being tested against. Set this to 0 if you would just like to test against the currently logged in user.
 * @param int $timestart ?
 * @param int $timeend ?
 * @return boolean
 * @todo Finish documenting this function
 */
function enrol_student($userid, $courseid, $timestart=0, $timeend=0, $enrol='') {

    global $CFG;

    if (!$course = get_record('course', 'id', $courseid)) {  // Check course
        return false;
    }
    if (!$user = get_record('user', 'id', $userid)) {        // Check user
        return false;
    }
    // enrol the student in any parent meta courses...
    if ($parents = get_records('course_meta','child_course',$courseid)) {
        foreach ($parents as $parent) {
            enrol_student($userid, $parent->parent_course,$timestart,$timeend,$enrol);
        }
    }

    if (empty($enrol)) {
        $enrol = $CFG->enrol;   // Default current method
    }
    if ($student = get_record('user_students', 'userid', $userid, 'course', $courseid)) {
        $student->timestart = $timestart;
        $student->timeend = $timeend;
        $student->time = time();
        $student->enrol = $enrol;
        return update_record('user_students', $student);

    } else {
        require_once("$CFG->dirroot/mod/forum/lib.php");
        forum_add_user($userid, $courseid);

        $student->userid = $userid;
        $student->course = $courseid;
        $student->timestart = $timestart;
        $student->timeend = $timeend;
        $student->time = time();
        $student->enrol = $enrol;
        return insert_record('user_students', $student);
    }
}

/**
 * Unenrols a student from a given course
 *
 * @param int $courseid The id of the course that is being viewed, if any
 * @param int $userid The id of the user that is being tested against.
 * @return boolean
 */
function unenrol_student($userid, $courseid=0) {

    if ($courseid) {
        /// First delete any crucial stuff that might still send mail
        if ($forums = get_records('forum', 'course', $courseid)) {
            foreach ($forums as $forum) {
                delete_records('forum_subscriptions', 'forum', $forum->id, 'userid', $userid);
            }
        }
        if ($groups = get_groups($courseid, $userid)) {
            foreach ($groups as $group) {
                delete_records('groups_members', 'groupid', $group->id, 'userid', $userid);
            }
        }
        // enrol the student in any parent meta courses...
        if ($parents = get_records('course_meta','child_course',$courseid)) {
            foreach ($parents as $parent) {
                unenrol_student($userid, $parent->parent_course);
            }
        }
        return delete_records('user_students', 'userid', $userid, 'course', $courseid);

    } else {
        delete_records('forum_subscriptions', 'userid', $userid);
        delete_records('groups_members', 'userid', $userid);
        return delete_records('user_students', 'userid', $userid);
    }
}

/**
 * Add a teacher to a given course
 *
  * @uses $USER
 * @param int $courseid The id of the course that is being viewed, if any
 * @param int $userid The id of the user that is being tested against. Set this to 0 if you would just like to test against the currently logged in user.
 * @param int $editall ?
 * @param string $role ?
 * @param int $timestart ?
 * @param int $timeend ?
 * @return boolean
 * @todo Finish documenting this function
 */
function add_teacher($userid, $courseid, $editall=1, $role='', $timestart=0, $timeend=0, $enrol='manual') {
    global $CFG;

    if ($teacher = get_record('user_teachers', 'userid', $userid, 'course', $courseid)) {
        $newteacher = NULL;
        $newteacher->id = $teacher->id;
        $newteacher->editall = $editall;
        $newteacher->enrol = $enrol;
        if ($role) {
            $newteacher->role = $role;
        }
        if ($timestart) {
            $newteacher->timestart = $timestart;
        }
        if ($timeend) {
            $newteacher->timeend = $timeend;
        }
        return update_record('user_teachers', $newteacher);
    }

    if (!record_exists('user', 'id', $userid)) {
        return false;   // no such user
    }

    if (!record_exists('course', 'id', $courseid)) {
        return false;   // no such course
    }

    $teacher = NULL;
    $teacher->userid  = $userid;
    $teacher->course  = $courseid;
    $teacher->editall = $editall;
    $teacher->role    = $role;
    $teacher->timemodified = time();
    $newteacher->timestart = $timestart;
    $newteacher->timeend = $timeend;
    if ($student = get_record('user_students', 'userid', $userid, 'course', $courseid)) {
        $teacher->timestart = $student->timestart;
        $teacher->timeend = $student->timeend;
        $teacher->timeaccess = $student->timeaccess;
    }

    if (record_exists('user_teachers', 'course', $courseid)) {
        $teacher->authority = 2;
    } else {
        $teacher->authority = 1;
    }
    delete_records('user_students', 'userid', $userid, 'course', $courseid); // Unenrol as student

    /// Add forum subscriptions for new users
    require_once('../mod/forum/lib.php');
    forum_add_user($userid, $courseid);

    return insert_record('user_teachers', $teacher);

}

/**
 * Removes a teacher from a given course (or ALL courses)
 * Does not delete the user account
 *
 * @param int $courseid The id of the course that is being viewed, if any
 * @param int $userid The id of the user that is being tested against.
 * @return boolean
 */
function remove_teacher($userid, $courseid=0) {
    if ($courseid) {
        /// First delete any crucial stuff that might still send mail
        if ($forums = get_records('forum', 'course', $courseid)) {
            foreach ($forums as $forum) {
                delete_records('forum_subscriptions', 'forum', $forum->id, 'userid', $userid);
            }
        }

        /// Next if the teacher is not registered as a student, but is
        /// a member of a group, remove them from the group.
        if (!isstudent($courseid, $userid)) {
            if ($groups = get_groups($courseid, $userid)) {
                foreach ($groups as $group) {
                    delete_records('groups_members', 'groupid', $group->id, 'userid', $userid);
                }
            }
        }

        return delete_records('user_teachers', 'userid', $userid, 'course', $courseid);
    } else {
        delete_records('forum_subscriptions', 'userid', $userid);
        return delete_records('user_teachers', 'userid', $userid);
    }
}

/**
 * Add a creator to the site
 *
 * @param int $userid The id of the user that is being tested against.
 * @return boolean
 */
function add_creator($userid) {

    if (!record_exists('user_admins', 'userid', $userid)) {
        if (record_exists('user', 'id', $userid)) {
            $creator->userid = $userid;
            return insert_record('user_coursecreators', $creator);
        }
        return false;
    }
    return true;
}

/**
 * Remove a creator from a site
 *
  * @uses $db
 * @param int $userid The id of the user that is being tested against.
 * @return boolean
 */
function remove_creator($userid) {
    global $db;

    return delete_records('user_coursecreators', 'userid', $userid);
}

/**
 * Add an admin to a site
 *
 * @uses SITEID
 * @param int $userid The id of the user that is being tested against.
 * @return boolean
 */
function add_admin($userid) {

    if (!record_exists('user_admins', 'userid', $userid)) {
        if (record_exists('user', 'id', $userid)) {
            $admin->userid = $userid;

            // any admin is also a teacher on the site course
            if (!record_exists('user_teachers', 'course', SITEID, 'userid', $userid)) {
                if (!add_teacher($userid, SITEID)) {
                    return false;
                }
            }

            return insert_record('user_admins', $admin);
        }
        return false;
    }
    return true;
}

/**
 * Removes an admin from a site
 *
  * @uses $db
  * @uses SITEID
 * @param int $userid The id of the user that is being tested against.
 * @return boolean
 */
function remove_admin($userid) {
    global $db;

    // remove also from the list of site teachers
    remove_teacher($userid, SITEID);

    return delete_records('user_admins', 'userid', $userid);
}

/**
 * Clear a course out completely, deleting all content
 * but don't delete the course itself
 *
 * @uses $USER
 * @uses $SESSION
 * @uses $CFG
 * @param int $courseid The id of the course that is being viewed
 * @param boolean $showfeedback Set this to false to suppress notifications from being printed as the functions performs its steps.
 * @return boolean
 */
function remove_course_contents($courseid, $showfeedback=true) {

    global $CFG, $USER, $SESSION;

    $result = true;

    if (! $course = get_record('course', 'id', $courseid)) {
        error('Course ID was incorrect (can\'t find it)');
    }

    $strdeleted = get_string('deleted');

    // First delete every instance of every module

    if ($allmods = get_records('modules') ) {
        foreach ($allmods as $mod) {
            $modname = $mod->name;
            $modfile = $CFG->dirroot .'/mod/'. $modname .'/lib.php';
            $moddelete = $modname .'_delete_instance';       // Delete everything connected to an instance
            $moddeletecourse = $modname .'_delete_course';   // Delete other stray stuff (uncommon)
            $count=0;
            if (file_exists($modfile)) {
                include_once($modfile);
                if (function_exists($moddelete)) {
                    if ($instances = get_records($modname, 'course', $course->id)) {
                        foreach ($instances as $instance) {
                            if ($moddelete($instance->id)) {
                                $count++;
                            } else {
                                notify('Could not delete '. $modname .' instance '. $instance->id .' ('. $instance->name .')');
                                $result = false;
                            }
                        }
                    }
                } else {
                    notify('Function '. $moddelete() .'doesn\'t exist!');
                    $result = false;
                }

                if (function_exists($moddeletecourse)) {
                    $moddeletecourse($course);
                }
            }
            if ($showfeedback) {
                notify($strdeleted .' '. $count .' x '. $modname);
            }
        }
    } else {
        error('No modules are installed!');
    }

    // Delete any user stuff

    if (delete_records('user_students', 'course', $course->id)) {
        if ($showfeedback) {
            notify($strdeleted .' user_students');
        }
    } else {
        $result = false;
    }

    if (delete_records('user_teachers', 'course', $course->id)) {
        if ($showfeedback) {
            notify($strdeleted .' user_teachers');
        }
    } else {
        $result = false;
    }

    // Delete any groups

    if ($groups = get_records('groups', 'courseid', $course->id)) {
        foreach ($groups as $group) {
            if (delete_records('groups_members', 'groupid', $group->id)) {
                if ($showfeedback) {
                    notify($strdeleted .' groups_members');
                }
            } else {
                $result = false;
            }
            if (delete_records('groups', 'id', $group->id)) {
                if ($showfeedback) {
                    notify($strdeleted .' groups');
                }
            } else {
                $result = false;
            }
        }
    }

    // Delete events

    if (delete_records('event', 'courseid', $course->id)) {
        if ($showfeedback) {
            notify($strdeleted .' event');
        }
    } else {
        $result = false;
    }

    // Delete logs

    if (delete_records('log', 'course', $course->id)) {
        if ($showfeedback) {
            notify($strdeleted .' log');
        }
    } else {
        $result = false;
    }

    // Delete any course stuff

    if (delete_records('course_sections', 'course', $course->id)) {
        if ($showfeedback) {
            notify($strdeleted .' course_sections');
        }
    } else {
        $result = false;
    }

    if (delete_records('course_modules', 'course', $course->id)) {
        if ($showfeedback) {
            notify($strdeleted .' course_modules');
        }
    } else {
        $result = false;
    }

    if ($course->metacourse) {
        delete_records("course_meta","parent_course",$course->id);
        sync_metacourse($course->id); // have to do it here so the enrolments get nuked. sync_metacourses won't find it without the id.
        if ($showfeedback) {
            notify("$strdeleted course_meta");
        }
    }
    else {
        if ($parents = get_records("course_meta","child_course",$course->id)) {
            foreach ($parents as $parent) {
                remove_from_metacourse($parent->parent_course,$parent->child_course); // this will do the unenrolments as well.
            }
            if ($showfeedback) {
                notify("$strdeleted course_meta");
            }
        }
    }

    return $result;

}

/**
 * This function will empty a course of USER data as much as
/// possible. It will retain the activities and the structure
/// of the course.
 *
 * @uses $USER
 * @uses $SESSION
 * @uses $CFG
 * @param int $courseid The id of the course that is being viewed
 * @param boolean $showfeedback Set this to false to suppress notifications from being printed as the functions performs its steps.
 * @param boolean $removestudents ?
 * @param boolean $removeteachers ?
 * @param boolean $removegroups ?
 * @param boolean $removeevents ?
 * @param boolean $removelogs ?
 * @return boolean
 * @todo Finish documenting this function
 */
function remove_course_userdata($courseid, $showfeedback=true,
                                $removestudents=true, $removeteachers=false, $removegroups=true,
                                $removeevents=true, $removelogs=false) {

    global $CFG, $USER, $SESSION;

    $result = true;

    if (! $course = get_record('course', 'id', $courseid)) {
        error('Course ID was incorrect (can\'t find it)');
    }

    $strdeleted = get_string('deleted');

    // Look in every instance of every module for data to delete

    if ($allmods = get_records('modules') ) {
        foreach ($allmods as $mod) {
            $modname = $mod->name;
            $modfile = $CFG->dirroot .'/mod/'. $modname .'/lib.php';
            $moddeleteuserdata = $modname .'_delete_userdata';   // Function to delete user data
            $count=0;
            if (file_exists($modfile)) {
                @include_once($modfile);
                if (function_exists($moddeleteuserdata)) {
                    $moddeleteuserdata($course, $showfeedback);
                }
            }
        }
    } else {
        error('No modules are installed!');
    }

    // Delete other stuff

    if ($removestudents) {
        /// Delete student enrolments
        if (delete_records('user_students', 'course', $course->id)) {
            if ($showfeedback) {
                notify($strdeleted .' user_students');
            }
        } else {
            $result = false;
        }
        /// Delete group members (but keep the groups)
        if ($groups = get_records('groups', 'courseid', $course->id)) {
            foreach ($groups as $group) {
                if (delete_records('groups_members', 'groupid', $group->id)) {
                    if ($showfeedback) {
                        notify($strdeleted .' groups_members');
                    }
                } else {
                    $result = false;
                }
            }
        }
    }

    if ($removeteachers) {
        if (delete_records('user_teachers', 'course', $course->id)) {
            if ($showfeedback) {
                notify($strdeleted .' user_teachers');
            }
        } else {
            $result = false;
        }
    }

    if ($removegroups) {
        if ($groups = get_records('groups', 'courseid', $course->id)) {
            foreach ($groups as $group) {
                if (delete_records('groups', 'id', $group->id)) {
                    if ($showfeedback) {
                        notify($strdeleted .' groups');
                    }
                } else {
                    $result = false;
                }
            }
        }
    }

    if ($removeevents) {
        if (delete_records('event', 'courseid', $course->id)) {
            if ($showfeedback) {
                notify($strdeleted .' event');
            }
        } else {
            $result = false;
        }
    }

    if ($removelogs) {
        if (delete_records('log', 'course', $course->id)) {
            if ($showfeedback) {
                notify($strdeleted .' log');
            }
        } else {
            $result = false;
        }
    }

    return $result;

}



/// GROUPS /////////////////////////////////////////////////////////


/**
* Returns a boolean: is the user a member of the given group?
*
* @param    type description
 * @todo Finish documenting this function
*/
function ismember($groupid, $userid=0) {
    global $USER;

    if (!$groupid) {   // No point doing further checks
        return false;
    }

    if (!$userid) {
        if (empty($USER->groupmember)) {
            return false;
        }
        foreach ($USER->groupmember as $courseid => $mgroupid) {
            if ($mgroupid == $groupid) {
                return true;
            }
        }
        return false;
    }

    return record_exists('groups_members', 'groupid', $groupid, 'userid', $userid);
}

/**
 * Add a user to a group, return true upon success or if user already a group member
 *
 * @param groupid  The group id
 * @param userid   The user id
 * @todo Finish documenting this function
 */
function add_user_to_group ($groupid, $userid) {
    if (ismember($groupid, $userid)) return true;
    $record->groupid = $groupid;
    $record->userid = $userid;
    $record->timeadded = time(); 
    return (insert_record('groups_members', $record) !== false);
}


/**
 * Returns the group ID of the current user in the given course
 *
 * @uses $USER
 * @param int $courseid The course being examined - relates to id field in 'course' table.
 * @todo Finish documenting this function
 */
function mygroupid($courseid) {
    global $USER;

    if (empty($USER->groupmember[$courseid])) {
        return 0;
    } else {
        return $USER->groupmember[$courseid];
    }
}

/**
 * For a given course, and possibly course module, determine
 * what the current default groupmode is:
 * NOGROUPS, SEPARATEGROUPS or VISIBLEGROUPS
 *
 * @param course $course A {@link $COURSE} object
 * @param array? $cm A course module object
 * @return int A group mode (NOGROUPS, SEPARATEGROUPS or VISIBLEGROUPS)
 */
function groupmode($course, $cm=null) {

    if ($cm and !$course->groupmodeforce) {
        return $cm->groupmode;
    }
    return $course->groupmode;
}


/**
 * Sets the current group in the session variable
 *
 * @uses $SESSION
 * @param int $courseid The course being examined - relates to id field in 'course' table.
 * @param int $groupid The group being examined.
 * @return int Current group id which was set by this function
 * @todo Finish documenting this function
 */
function set_current_group($courseid, $groupid) {
    global $SESSION;

    return $SESSION->currentgroup[$courseid] = $groupid;
}


/**
 * Gets the current group for the current user as an id or an object
 *
 * @uses $CFG
 * @uses $SESSION
 * @param int $courseid The course being examined - relates to id field in 'course' table.
 * @param boolean $full If true, the return value is a full record object. If false, just the id of the record.
 * @todo Finish documenting this function
 */
function get_current_group($courseid, $full=false) {
    global $SESSION, $USER;

    if (!isset($SESSION->currentgroup[$courseid])) {
        if (empty($USER->groupmember[$courseid])) {
            return 0;
        } else {
            $SESSION->currentgroup[$courseid] = $USER->groupmember[$courseid];
        }
    }

    if ($full) {
        return get_record('groups', 'id', $SESSION->currentgroup[$courseid]);
    } else {
        return $SESSION->currentgroup[$courseid];
    }
}

/**
 * A combination function to make it easier for modules
 * to set up groups.
 *
 * It will use a given "groupid" parameter and try to use
 * that to reset the current group for the user.
 *
 * @uses VISIBLEGROUPS
 * @param course $course A {@link $COURSE} object
 * @param int $groupmode Either NOGROUPS, SEPARATEGROUPS or VISIBLEGROUPS
 * @param int $groupid Will try to use this optional parameter to
 *            reset the current group for the user
 * @return int|false Returns the current group id or false if error.
 * @todo Finish documenting this function
 */
function get_and_set_current_group($course, $groupmode, $groupid=-1) {

    if (!$groupmode) {   // Groups don't even apply
        return false;
    }

    $currentgroupid = get_current_group($course->id);

    if ($groupid < 0) {  // No change was specified
        return $currentgroupid;
    }

    if ($groupid) {      // Try to change the current group to this groupid
        if ($group = get_record('groups', 'id', $groupid, 'courseid', $course->id)) { // Exists
            if (isteacheredit($course->id)) {          // Sets current default group
                $currentgroupid = set_current_group($course->id, $group->id);

            } else if ($groupmode == VISIBLEGROUPS) {  // All groups are visible
                $currentgroupid = $group->id;
            }
        }
    } else {             // When groupid = 0 it means show ALL groups
        if (isteacheredit($course->id)) {          // Sets current default group
            $currentgroupid = set_current_group($course->id, 0);

        } else if ($groupmode == VISIBLEGROUPS) {  // All groups are visible
            $currentgroupid = 0;
        }
    }

    return $currentgroupid;
}


/**
 * A big combination function to make it easier for modules
 * to set up groups.
 *
 * Terminates if the current user shouldn't be looking at this group
 * Otherwise returns the current group if there is one
 * Otherwise returns false if groups aren't relevant
 *
 * @uses SEPARATEGROUPS
 * @uses VISIBLEGROUPS
 * @param course $course A {@link $COURSE} object
 * @param int $groupmode Either NOGROUPS, SEPARATEGROUPS or VISIBLEGROUPS
 * @param string $urlroot ?
 * @todo Finish documenting this function
 */
function setup_and_print_groups($course, $groupmode, $urlroot) {

    if (isset($_GET['group'])) {
        $changegroup = $_GET['group'];  /// 0 or higher
    } else {
        $changegroup = -1;              /// This means no group change was specified
    }

    $currentgroup = get_and_set_current_group($course, $groupmode, $changegroup);

    if ($currentgroup === false) {
        return false;
    }

    if ($groupmode == SEPARATEGROUPS and !isteacheredit($course->id) and !$currentgroup) {
        print_heading(get_string('notingroup'));
        print_footer($course);
        exit;
    }

    if ($groupmode == VISIBLEGROUPS or ($groupmode and isteacheredit($course->id))) {
        if ($groups = get_records_menu('groups', 'courseid', $course->id, 'name ASC', 'id,name')) {
            echo '<div align="center">';
            print_group_menu($groups, $groupmode, $currentgroup, $urlroot);
            echo '</div>';
        }
    }

    return $currentgroup;
}

function generate_email_processing_address($modid,$modargs) {
    global $CFG;

    if (empty($CFG->siteidentifier)) {    // Unique site identification code
        set_config('siteidentifier', random_string(32));
    }
    
    $header = $CFG->mailprefix . substr(base64_encode(pack('C',$modid)),0,2).$modargs;
    return $header . substr(md5($header.$CFG->sitesecret),0,16).'@'.$CFG->maildomain;
}


function moodle_process_email($modargs,$body) {
    // the first char should be an unencoded letter. We'll take this as an action
    switch ($modargs{0}) {
        case 'B': { // bounce
            list(,$userid) = unpack('V',base64_decode(substr($modargs,1,8)));
            if ($user = get_record_select("user","id=$userid","id,email")) {
                // check the half md5 of their email
                $md5check = substr(md5($user->email),0,16);
                if ($md5check = substr($modargs, -16)) {
                    set_bounce_count($user);
                }
                // else maybe they've already changed it?
            }
        }
        break;
        // maybe more later?
    }
}

/// CORRESPONDENCE  ////////////////////////////////////////////////

/**
 * Send an email to a specified user
 *
 * @uses $CFG
 * @uses $_SERVER
 * @uses SITEID
 * @param user $user  A {@link $USER} object
 * @param user $from A {@link $USER} object
 * @param string $subject plain text subject line of the email
 * @param string $messagetext plain text version of the message
 * @param string $messagehtml complete html version of the message (optional)
 * @param string $attachment a file on the filesystem, relative to $CFG->dataroot
 * @param string $attachname the name of the file (extension indicates MIME)
 * @param boolean $usetrueaddress determines whether $from email address should
 *          be sent out. Will be overruled by user profile setting for maildisplay
 * @return boolean|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
function email_to_user($user, $from, $subject, $messagetext, $messagehtml='', $attachment='', $attachname='', $usetrueaddress=true, $repyto='', $replytoname='') {

    global $CFG, $FULLME;

    global $course;                // This is a bit of an ugly hack to be gotten rid of later
    if (!empty($course->lang)) {   // Course language is defined
        $CFG->courselang = $course->lang;
    }
    if (!empty($course->theme)) {   // Course language is defined
        $CFG->coursetheme = $course->theme;
    }

    include_once($CFG->libdir .'/phpmailer/class.phpmailer.php');

    if (empty($user)) {
        return false;
    }

    if (!empty($user->emailstop)) {
        return 'emailstop';
    }
    
    if (over_bounce_threshold($user)) {
        error_log("User $user->id (".fullname($user).") is over bounce threshold! Not sending.");
        return false;
    }

    $mail = new phpmailer;

    $mail->Version = 'Moodle '. $CFG->version;           // mailer version
    $mail->PluginDir = $CFG->libdir .'/phpmailer/';      // plugin directory (eg smtp plugin)


    if (current_language() != 'en') {
        $mail->CharSet = get_string('thischarset');
    }

    if ($CFG->smtphosts == 'qmail') {
        $mail->IsQmail();                              // use Qmail system

    } else if (empty($CFG->smtphosts)) {
        $mail->IsMail();                               // use PHP mail() = sendmail

    } else {
        $mail->IsSMTP();                               // use SMTP directly
        if ($CFG->debug > 7) {
            echo '<pre>' . "\n";
            $mail->SMTPDebug = true;
        }
        $mail->Host = $CFG->smtphosts;               // specify main and backup servers

        if ($CFG->smtpuser) {                          // Use SMTP authentication
            $mail->SMTPAuth = true;
            $mail->Username = $CFG->smtpuser;
            $mail->Password = $CFG->smtppass;
        }
    }

    $adminuser = get_admin();

    // make up an email address for handling bounces
    if (!empty($CFG->handlebounces)) {
        $modargs = 'B'.base64_encode(pack('V',$user->id)).substr(md5($user->email),0,16);
        $mail->Sender = generate_email_processing_address(0,$modargs);
    }
    else {
        $mail->Sender   = $adminuser->email;
    } 

    if (is_string($from)) { // So we can pass whatever we want if there is need
        $mail->From     = $CFG->noreplyaddress;
        $mail->FromName = $from;
    } else if ($usetrueaddress and $from->maildisplay) {
        $mail->From     = $from->email;
        $mail->FromName = fullname($from);
    } else {
        $mail->From     = $CFG->noreplyaddress;
        $mail->FromName = fullname($from);
        if (empty($replyto)) {
            $mail->AddReplyTo($CFG->noreplyaddress,get_string('noreplyname'));
        }
    }
        
    if (!empty($replyto)) {
        $mail->AddReplyTo($replyto,$replytoname);
    }

    $mail->Subject  =  stripslashes($subject);

    $mail->AddAddress($user->email, fullname($user) );

    $mail->WordWrap = 79;                               // set word wrap

    if (!empty($from->customheaders)) {                 // Add custom headers
        if (is_array($from->customheaders)) {
            foreach ($from->customheaders as $customheader) {
                $mail->AddCustomHeader($customheader);
            }
        } else {
            $mail->AddCustomHeader($from->customheaders);
        }
    }

    if ($messagehtml && $user->mailformat == 1) { // Don't ever send HTML to users who don't want it
        $mail->IsHTML(true);
        $mail->Encoding = 'quoted-printable';           // Encoding to use
        $mail->Body    =  $messagehtml;
        $mail->AltBody =  "\n$messagetext\n";
    } else {
        $mail->IsHTML(false);
        $mail->Body =  "\n$messagetext\n";
    }

    if ($attachment && $attachname) {
        if (ereg( "\\.\\." ,$attachment )) {    // Security check for ".." in dir path
            $mail->AddAddress($adminuser->email, fullname($adminuser) );
            $mail->AddStringAttachment('Error in attachment.  User attempted to attach a filename with a unsafe name.', 'error.txt', '8bit', 'text/plain');
        } else {
            include_once($CFG->dirroot .'/files/mimetypes.php');
            $mimetype = mimeinfo('type', $attachname);
            $mail->AddAttachment($CFG->dataroot .'/'. $attachment, $attachname, 'base64', $mimetype);
        }
    }

    if ($mail->Send()) {
        set_send_count($user);
        return true;
    } else {
        mtrace('ERROR: '. $mail->ErrorInfo);
        add_to_log(SITEID, 'library', 'mailer', $FULLME, 'ERROR: '. $mail->ErrorInfo);
        return false;
    }
}

/**
 * Resets specified user's password and send the new password to the user via email.
 *
 * @uses $CFG
 * @param user $user A {@link $USER} object
 * @return boolean|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
function reset_password_and_mail($user) {

    global $CFG;

    $site  = get_site();
    $from = get_admin();

    $newpassword = generate_password();

    if (! set_field('user', 'password', md5($newpassword), 'id', $user->id) ) {
        error('Could not set user password!');
    }

    $a->firstname = $user->firstname;
    $a->sitename = $site->fullname;
    $a->username = $user->username;
    $a->newpassword = $newpassword;
    $a->link = $CFG->wwwroot .'/login/change_password.php';
    $a->signoff = fullname($from, true).' ('. $from->email .')';

    $message = get_string('newpasswordtext', '', $a);

    $subject  = $site->fullname .': '. get_string('changedpassword');

    return email_to_user($user, $from, $subject, $message);

}

/**
 * Send email to specified user with confirmation text and activation link.
 *
 * @uses $CFG
 * @param user $user A {@link $USER} object
 * @return boolean|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
 function send_confirmation_email($user) {

    global $CFG;

    $site = get_site();
    $from = get_admin();

    $data->firstname = fullname($user);
    $data->sitename = $site->fullname;
    $data->link = $CFG->wwwroot .'/login/confirm.php?p='. $user->secret .'&amp;s='. $user->username;
    $data->admin = fullname($from) .' ('. $from->email .')';

    $message = get_string('emailconfirmation', '', $data);
    $subject = get_string('emailconfirmationsubject', '', $site->fullname);

    $messagehtml = text_to_html($message, false, false, true);

    return email_to_user($user, $from, $subject, $message, $messagehtml);

}

/**
 * send_password_change_confirmation_email.
 *
 * @uses $CFG
 * @param user $user A {@link $USER} object
 * @return boolean|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 * @todo Finish documenting this function
 */
function send_password_change_confirmation_email($user) {

    global $CFG;

    $site = get_site();
    $from = get_admin();

    $data->firstname = $user->firstname;
    $data->sitename = $site->fullname;
    $data->link = $CFG->wwwroot .'/login/forgot_password.php?p='. $user->secret .'&amp;s='. $user->username;
    $data->admin = fullname($from).' ('. $from->email .')';

    $message = get_string('emailpasswordconfirmation', '', $data);
    $subject = get_string('emailpasswordconfirmationsubject', '', $site->fullname);

    return email_to_user($user, $from, $subject, $message);

}

/**
 * Check that an email is allowed.  It returns an error message if there
 * was a problem.
 *
 * @param    type description
 * @todo Finish documenting this function
 */
function email_is_not_allowed($email) {

    global $CFG;

    if (!empty($CFG->allowemailaddresses)) {
        $allowed = explode(' ', $CFG->allowemailaddresses);
        foreach ($allowed as $allowedpattern) {
            $allowedpattern = trim($allowedpattern);
            if (!$allowedpattern) {
                continue;
            }
            if (strpos($email, $allowedpattern) !== false) {  // Match!
                return false;
            }
        }
        return get_string('emailonlyallowed', '', $CFG->allowemailaddresses);

    } else if (!empty($CFG->denyemailaddresses)) {
        $denied = explode(' ', $CFG->denyemailaddresses);
        foreach ($denied as $deniedpattern) {
            $deniedpattern = trim($deniedpattern);
            if (!$deniedpattern) {
                continue;
            }
            if (strpos($email, $deniedpattern) !== false) {   // Match!
                return get_string('emailnotallowed', '', $CFG->denyemailaddresses);
            }
        }
    }

    return false;
}


/// FILE HANDLING  /////////////////////////////////////////////

/**
 * Create a directory.
 *
 * @uses $CFG
 * @param string $directory  a string of directory names under $CFG->dataroot eg  stuff/assignment/1
 * param boolean $shownotices If true then notification messages will be printed out on error.
 * @return string|false Returns full path to directory if successful, false if not
 */
function make_upload_directory($directory, $shownotices=true) {

    global $CFG;

    $currdir = $CFG->dataroot;

    umask(0000);

    if (!file_exists($currdir)) {
        if (! mkdir($currdir, $CFG->directorypermissions)) {
            if ($shownotices) {
                notify('ERROR: You need to create the directory '. $currdir .' with web server write access');
            }
            return false;
        }
        if ($handle = fopen($currdir.'/.htaccess', 'w')) {   // For safety
            @fwrite($handle, "deny from all\r\n");
            @fclose($handle); 
        }
    }

    $dirarray = explode('/', $directory);

    foreach ($dirarray as $dir) {
        $currdir = $currdir .'/'. $dir;
        if (! file_exists($currdir)) {
            if (! mkdir($currdir, $CFG->directorypermissions)) {
                if ($shownotices) {
                    notify('ERROR: Could not find or create a directory ('. $currdir .')');
                }
                return false;
            }
            //@chmod($currdir, $CFG->directorypermissions);  // Just in case mkdir didn't do it
        }
    }

    return $currdir;
}

/**
 * Makes an upload directory for a particular module.
 *
 * @uses $CFG
 * @param int $courseid The id of the course in question - maps to id field of 'course' table.
 * @return string|false Returns full path to directory if successful, false if not
 * @todo Finish documenting this function
 */
function make_mod_upload_directory($courseid) {
    global $CFG;

    if (! $moddata = make_upload_directory($courseid .'/'. $CFG->moddata)) {
        return false;
    }

    $strreadme = get_string('readme');

    if (file_exists($CFG->dirroot .'/lang/'. $CFG->lang .'/docs/module_files.txt')) {
        copy($CFG->dirroot .'/lang/'. $CFG->lang .'/docs/module_files.txt', $moddata .'/'. $strreadme .'.txt');
    } else {
        copy($CFG->dirroot .'/lang/en/docs/module_files.txt', $moddata .'/'. $strreadme .'.txt');
    }
    return $moddata;
}

/**
 * Returns current name of file on disk if it exists.
 *
 * @param string $newfile File to be verified
 * @return string Current name of file on disk if true
 * @todo Finish documenting this function
 */
function valid_uploaded_file($newfile) {
    if (empty($newfile)) {
        return '';
    }
    if (is_uploaded_file($newfile['tmp_name']) and $newfile['size'] > 0) {
        return $newfile['tmp_name'];
    } else {
        return '';
    }
}

/**
 * Returns the maximum size for uploading files.
 *
 * There are seven possible upload limits:
 * 1. in Apache using LimitRequestBody (no way of checking or changing this)
 * 2. in php.ini for 'upload_max_filesize' (can not be changed inside PHP)
 * 3. in .htaccess for 'upload_max_filesize' (can not be changed inside PHP)
 * 4. in php.ini for 'post_max_size' (can not be changed inside PHP)
 * 5. by the Moodle admin in $CFG->maxbytes
 * 6. by the teacher in the current course $course->maxbytes
 * 7. by the teacher for the current module, eg $assignment->maxbytes
 *
 * These last two are passed to this function as arguments (in bytes).
 * Anything defined as 0 is ignored.
 * The smallest of all the non-zero numbers is returned.
 *
 * @param int $sizebytes ?
 * @param int $coursebytes Current course $course->maxbytes (in bytes)
 * @param int $modulebytes Current module ->maxbytes (in bytes)
 * @return int The maximum size for uploading files.
 * @todo Finish documenting this function
 */
function get_max_upload_file_size($sitebytes=0, $coursebytes=0, $modulebytes=0) {

    if (! $filesize = ini_get('upload_max_filesize')) {
        $filesize = '5M';
    }
    $minimumsize = get_real_size($filesize);

    if ($postsize = ini_get('post_max_size')) {
        $postsize = get_real_size($postsize);
        if ($postsize < $minimumsize) {
            $minimumsize = $postsize;
        }
    }

    if ($sitebytes and $sitebytes < $minimumsize) {
        $minimumsize = $sitebytes;
    }

    if ($coursebytes and $coursebytes < $minimumsize) {
        $minimumsize = $coursebytes;
    }

    if ($modulebytes and $modulebytes < $minimumsize) {
        $minimumsize = $modulebytes;
    }

    return $minimumsize;
}

/**
 * Related to the above function - this function returns an
 * array of possible sizes in an array, translated to the
 * local language.
 *
 * @uses SORT_NUMERIC
 * @param int $sizebytes ?
 * @param int $coursebytes Current course $course->maxbytes (in bytes)
 * @param int $modulebytes Current module ->maxbytes (in bytes)
 * @return int
 * @todo Finish documenting this function
 */
function get_max_upload_sizes($sitebytes=0, $coursebytes=0, $modulebytes=0) {

    if (!$maxsize = get_max_upload_file_size($sitebytes, $coursebytes, $modulebytes)) {
        return array();
    }

    $filesize[$maxsize] = display_size($maxsize);

    $sizelist = array(10240, 51200, 102400, 512000, 1048576, 2097152,
                      5242880, 10485760, 20971520, 52428800, 104857600);

    foreach ($sizelist as $sizebytes) {
       if ($sizebytes < $maxsize) {
           $filesize[$sizebytes] = display_size($sizebytes);
       }
    }

    krsort($filesize, SORT_NUMERIC);

    return $filesize;
}

/**
 * If there has been an error uploading a file, print the appropriate error message
 * Numerical constants used as constant definitions not added until PHP version 4.2.0
 *
 * $filearray is a 1-dimensional sub-array of the $_FILES array
 * eg $filearray = $_FILES['userfile1']
 * If left empty then the first element of the $_FILES array will be used
 *
 * @uses $_FILES
 * @param array $filearray  A 1-dimensional sub-array of the $_FILES array
 * @param boolean $returnerror ?
 * @return boolean
 * @todo Finish documenting this function
 */
function print_file_upload_error($filearray = '', $returnerror = false) {

    if ($filearray == '' or !isset($filearray['error'])) {

        if (empty($_FILES)) return false;

        $files = $_FILES; /// so we don't mess up the _FILES array for subsequent code
        $filearray = array_shift($files); /// use first element of array
    }

    switch ($filearray['error']) {

        case 0: // UPLOAD_ERR_OK
            if ($filearray['size'] > 0) {
                $errmessage = get_string('uploadproblem', $filearray['name']);
            } else {
                $errmessage = get_string('uploadnofilefound'); /// probably a dud file name
            }
            break;

        case 1: // UPLOAD_ERR_INI_SIZE
            $errmessage = get_string('uploadserverlimit');
            break;

        case 2: // UPLOAD_ERR_FORM_SIZE
            $errmessage = get_string('uploadformlimit');
            break;

        case 3: // UPLOAD_ERR_PARTIAL
            $errmessage = get_string('uploadpartialfile');
            break;

        case 4: // UPLOAD_ERR_NO_FILE
            $errmessage = get_string('uploadnofilefound');
            break;

        default:
            $errmessage = get_string('uploadproblem', $filearray['name']);
    }

    if ($returnerror) {
        return $errmessage;
    } else {
        notify($errmessage);
        return true;
    }

}

/**
 * Returns an array with all the filenames in
 * all subdirectories, relative to the given rootdir.
 * If excludefile is defined, then that file/directory is ignored
 * If getdirs is true, then (sub)directories are included in the output
 * If getfiles is true, then files are included in the output
 * (at least one of these must be true!)
 *
 * @param string $rootdir  ?
 * @param string $excludefile  If defined then the specified file/directory is ignored
 * @param boolean $descend  ?
 * @param boolean $getdirs  If true then (sub)directories are included in the output
 * @param boolean $getfiles  If true then files are included in the output
 * @return array An array with all the filenames in
 * all subdirectories, relative to the given rootdir
 * @todo Finish documenting this function. Add examples of $excludefile usage.
 */
function get_directory_list($rootdir, $excludefile='', $descend=true, $getdirs=false, $getfiles=true) {

    $dirs = array();

    if (!$getdirs and !$getfiles) {   // Nothing to show
        return $dirs;
    }

    if (!is_dir($rootdir)) {          // Must be a directory
        return $dirs;
    }