MDL-8002 - Don't show overall feedback for incomplete quiz attempts.

[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 (Encased in phpdoc proper comments)/////////////////////////

/**
 * 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);

/// Date and time constants ///
/**
 * 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 - every call to optional_param(), required_param()  ///
/// or clean_param() should have a specified type of parameter.  //////////////

/**
 * PARAM_RAW specifies a parameter that is not cleaned/processed in any way;
 * originally was 0, but changed because we need to detect unknown
 * parameter types and swiched order in clean_param().
 */
define('PARAM_RAW', 666);

/**
 * PARAM_CLEAN - obsoleted, please try to use more specific type of parameter.
 * It was one of the first types, that is why it is abused so much ;-)
 */
define('PARAM_CLEAN',    0x0001);

/**
 * PARAM_INT - integers only, use when expecting only numbers.
 */
define('PARAM_INT',      0x0002);

/**
 * PARAM_INTEGER - an alias for PARAM_INT
 */
define('PARAM_INTEGER',  0x0002);

/**
 * PARAM_ALPHA - contains only english letters.
 */
define('PARAM_ALPHA',    0x0004);

/**
 * PARAM_ACTION - an alias for PARAM_ALPHA, use for various actions in formas and urls
 * @TODO: should we alias it to PARAM_ALPHANUM ?
 */
define('PARAM_ACTION',   0x0004);

/**
 * PARAM_FORMAT - an alias for PARAM_ALPHA, use for names of plugins, formats, etc.
 * @TODO: should we alias it to PARAM_ALPHANUM ?
 */
define('PARAM_FORMAT',   0x0004);

/**
 * PARAM_NOTAGS - all html tags are stripped from the text. Do not abuse this type.
 */
define('PARAM_NOTAGS',   0x0008);

 /**
 * PARAM_MULTILANG - alias of PARAM_TEXT.
 */
define('PARAM_MULTILANG',  0x0009);

 /**
 * PARAM_TEXT - general plain text compatible with multilang filter, no other html tags.
 */
define('PARAM_TEXT',  0x0009);

/**
 * PARAM_FILE - safe file name, all dangerous chars are stripped, protects against XSS, SQL injections and directory traversals
 */
define('PARAM_FILE',     0x0010);

/**
 * PARAM_PATH - safe relative path name, all dangerous chars are stripped, protects against XSS, SQL injections and directory traversals
 * note: the leading slash is not removed, window drive letter is not allowed
 */
define('PARAM_PATH',     0x0020);

/**
 * PARAM_HOST - expected fully qualified domain name (FQDN) or an IPv4 dotted quad (IP address)
 */
define('PARAM_HOST',     0x0040);

/**
 * PARAM_URL - expected properly formatted URL.
 */
define('PARAM_URL',      0x0080);

/**
 * PARAM_LOCALURL - expected properly formatted URL as well as one that refers to the local server itself. (NOT orthogonal to the others! Implies PARAM_URL!)
 */
define('PARAM_LOCALURL', 0x0180);

/**
 * PARAM_CLEANFILE - safe file name, all dangerous and regional chars are removed,
 * use when you want to store a new file submitted by students
 */
define('PARAM_CLEANFILE',0x0200);

/**
 * PARAM_ALPHANUM - expected numbers and letters only.
 */
define('PARAM_ALPHANUM', 0x0400);

/**
 * PARAM_BOOL - converts input into 0 or 1, use for switches in forms and urls.
 */
define('PARAM_BOOL',     0x0800);

/**
 * PARAM_CLEANHTML - cleans submitted HTML code and removes slashes
 * note: do not forget to addslashes() before storing into database!
 */
define('PARAM_CLEANHTML',0x1000);

/**
 * PARAM_ALPHAEXT the same contents as PARAM_ALPHA plus the chars in quotes: "/-_" allowed,
 * suitable for include() and require()
 * @TODO: should we rename this function to PARAM_SAFEDIRS??
 */
define('PARAM_ALPHAEXT', 0x2000);

/**
 * PARAM_SAFEDIR - safe directory name, suitable for include() and require()
 */
define('PARAM_SAFEDIR',  0x4000);

/**
 * PARAM_SEQUENCE - expects a sequence of numbers like 8 to 1,5,6,4,6,8,9.  Numbers and comma only.
 */
define('PARAM_SEQUENCE',  0x8000);

/// Page types ///
/**
 * PAGE_COURSE_VIEW is a definition of a page type. For more information on the page class see moodle/lib/pagelib.php.
 */
define('PAGE_COURSE_VIEW', 'course-view');

/// Debug levels ///
/** no warnings at all */
define ('DEBUG_NONE', 0);
/** E_ERROR | E_PARSE */
define ('DEBUG_MINIMAL', 5);
/** E_ERROR | E_PARSE | E_WARNING | E_NOTICE */
define ('DEBUG_NORMAL', 15);
/** E_ALL without E_STRICT and E_RECOVERABLE_ERROR for now */
define ('DEBUG_ALL', 2047);
/** DEBUG_ALL with extra Moodle debug messages - (DEBUG_ALL | 32768) */
define ('DEBUG_DEVELOPER', 34815);

/// 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 $parname the name of the page parameter we want
 * @param int $type expected type of parameter
 * @return mixed
 */
function required_param($parname, $type=PARAM_CLEAN) {

    // detect_unchecked_vars addition
    global $CFG;
    if (!empty($CFG->detect_unchecked_vars)) {
        global $UNCHECKED_VARS;
        unset ($UNCHECKED_VARS->vars[$parname]);
    }

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

    return clean_param($param, $type);
}

/**
 * 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 $parname the name of the page parameter we want
 * @param mixed  $default the default value to return if nothing is found
 * @param int $type expected type of parameter
 * @return mixed
 */
function optional_param($parname, $default=NULL, $type=PARAM_CLEAN) {

    // detect_unchecked_vars addition
    global $CFG;
    if (!empty($CFG->detect_unchecked_vars)) {
        global $UNCHECKED_VARS;
        unset ($UNCHECKED_VARS->vars[$parname]);
    }

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

    return clean_param($param, $type);
}

/**
 * Used by {@link optional_param()} and {@link required_param()} to
 * clean the variables and/or cast to specific types, based on
 * an options field.
 * <code>
 * $course->format = clean_param($course->format, PARAM_ALPHA);
 * $selectedgrade_item = clean_param($selectedgrade_item, PARAM_CLEAN);
 * </code>
 *
 * @uses $CFG
 * @uses PARAM_CLEAN
 * @uses PARAM_INT
 * @uses PARAM_INTEGER
 * @uses PARAM_ALPHA
 * @uses PARAM_ALPHANUM
 * @uses PARAM_NOTAGS
 * @uses PARAM_ALPHAEXT
 * @uses PARAM_BOOL
 * @uses PARAM_SAFEDIR
 * @uses PARAM_CLEANFILE
 * @uses PARAM_FILE
 * @uses PARAM_PATH
 * @uses PARAM_HOST
 * @uses PARAM_URL
 * @uses PARAM_LOCALURL
 * @uses PARAM_CLEANHTML
 * @uses PARAM_SEQUENCE
 * @param mixed $param the variable we are cleaning
 * @param int $type expected format of param after cleaning.
 * @return mixed
 */
function clean_param($param, $type) {

    global $CFG;

    if (is_array($param)) {              // Let's loop
        $newparam = array();
        foreach ($param as $key => $value) {
            $newparam[$key] = clean_param($value, $type);
        }
        return $newparam;
    }

    switch ($type) {
        case PARAM_RAW:          // no cleaning at all
            return $param;

        case PARAM_CLEAN:        // General HTML cleaning, try to use more specific type if possible
            if (is_numeric($param)) {
                return $param;
            }
            $param = stripslashes($param);   // Needed for kses to work fine
            $param = clean_text($param);     // Sweep for scripts, etc
            return addslashes($param);       // Restore original request parameter slashes

        case PARAM_CLEANHTML:    // prepare html fragment for display, do not store it into db!!
            $param = stripslashes($param);   // Remove any slashes
            $param = clean_text($param);     // Sweep for scripts, etc
            return trim($param);

        case PARAM_INT:
            return (int)$param;  // Convert to integer

        case PARAM_ALPHA:        // Remove everything not a-z
            return eregi_replace('[^a-zA-Z]', '', $param);

        case PARAM_ALPHANUM:     // Remove everything not a-zA-Z0-9
            return eregi_replace('[^A-Za-z0-9]', '', $param);

        case PARAM_ALPHAEXT:     // Remove everything not a-zA-Z/_-
            return eregi_replace('[^a-zA-Z/_-]', '', $param);

        case PARAM_SEQUENCE:     // Remove everything not 0-9,
            return eregi_replace('[^0-9,]', '', $param);

        case PARAM_BOOL:         // Convert to 1 or 0
            $tempstr = strtolower($param);
            if ($tempstr == 'on' or $tempstr == 'yes' ) {
                $param = 1;
            } else if ($tempstr == 'off' or $tempstr == 'no') {
                $param = 0;
            } else {
                $param = empty($param) ? 0 : 1;
            }
            return $param;

        case PARAM_NOTAGS:       // Strip all tags
            return strip_tags($param);

        case PARAM_TEXT:    // leave only tags needed for multilang
            return clean_param(strip_tags($param, '<lang><span>'), PARAM_CLEAN);

        case PARAM_SAFEDIR:      // Remove everything not a-zA-Z0-9_-
            return eregi_replace('[^a-zA-Z0-9_-]', '', $param);

        case PARAM_CLEANFILE:    // allow only safe characters
            return clean_filename($param);

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

        case 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);
            return ereg_replace('/(\./)+', '/', $param);

        case 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='';
            }
            return $param;

        case PARAM_URL:          // allow safe ftp, http, mailto urls
            include_once($CFG->dirroot . '/lib/validateurlsyntax.php');
            if (!empty($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
            }
            return $param;

        case PARAM_LOCALURL:     // allow http absolute, root relative and relative URLs within wwwroot
            clean_param($param, PARAM_URL);
            if (!empty($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;

        default:                 // throw error, switched parameters in optional_param or another serious problem
            error("Unknown parameter type: $type");
    }
}



/**
 * 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.
 *
 * Can also be used to update keys for plugin-scoped configs in config_plugin table.
 * In that case it doesn't affect $CFG.
 *
 * @param string $name the key to set
 * @param string $value the value to set (without magic quotes)
 * @param string $plugin (optional) the plugin scope
 * @uses $CFG
 * @return bool
 */
function set_config($name, $value, $plugin=NULL) {
/// No need for get_config because they are usually always available in $CFG

    global $CFG;

    if (empty($plugin)) {
        $CFG->$name = $value;  // So it's defined for this invocation at least

        if (get_field('config', 'name', 'name', $name)) {
            return set_field('config', 'value', addslashes($value), 'name', $name);
        } else {
            $config = new object();
            $config->name = $name;
            $config->value = addslashes($value);
            return insert_record('config', $config);
        }
    } else { // plugin scope
        if ($id = get_field('config_plugins', 'id', 'name', $name, 'plugin', $plugin)) {
            return set_field('config_plugins', 'value', addslashes($value), 'id', $id);
        } else {
            $config = new object();
            $config->plugin = addslashes($plugin);
            $config->name   = $name;
            $config->value  = $value;
            return insert_record('config_plugins', $config);
        }
    }
}

/**
 * Get configuration values from the global config table
 * or the config_plugins table.
 *
 * If called with no parameters it will do the right thing
 * generating $CFG safely from the database without overwriting
 * existing values.
 *
 * @param string $plugin
 * @param string $name
 * @uses $CFG
 * @return hash-like object or single value
 *
 */
function get_config($plugin=NULL, $name=NULL) {

    global $CFG;

    if (!empty($name)) { // the user is asking for a specific value
        if (!empty($plugin)) {
            return get_record('config_plugins', 'plugin' , $plugin, 'name', $name);
        } else {
            return get_record('config', 'name', $name);
        }
    }

    // the user is after a recordset
    if (!empty($plugin)) {
        if ($configs=get_records('config_plugins', 'plugin', $plugin, '', 'name,value')) {
            $configs = (array)$configs;
            $localcfg = array();
            foreach ($configs as $config) {
                $localcfg[$config->name] = $config->value;
            }
            return (object)$localcfg;
        } else {
            return false;
        }
    } else {
        // this was originally in setup.php
        if ($configs = get_records('config')) {
            $localcfg = (array)$CFG;
            foreach ($configs as $config) {
                if (!isset($localcfg[$config->name])) {
                    $localcfg[$config->name] = $config->value;
                } else {
                    if ($localcfg[$config->name] != $config->value ) {
                        // complain if the DB has a different
                        // value than config.php does
                        error_log("\$CFG->{$config->name} in config.php ({$localcfg[$config->name]}) overrides database setting ({$config->value})");
                    }
                }
            }

            $localcfg = (object)$localcfg;
            return $localcfg;
        } else {
            // preserve $CFG if DB returns nothing or error
            return $CFG;
        }

    }
}

/**
 * Removes a key from global configuration
 *
 * @param string $name the key to set
 * @param string $plugin (optional) the plugin scope
 * @uses $CFG
 * @return bool
 */
function unset_config($name, $plugin=NULL) {

    global $CFG;

    unset($CFG->$name);

    if (empty($plugin)) {
        return delete_records('config', 'name', $name);
    } else { 
        return delete_records('config_plugins', 'name', $name, 'plugin', $plugin);
    }
}


/**
 * 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. Add inline links to $USER and user functions in above line.

 * @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 $userid A moodle user ID
 * @return bool
 */
function set_user_preference($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 $userid A moodle user ID
 * @return bool
 */
function unset_user_preference($name, $userid=NULL) {

    global $USER;

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

    //Delete the preference from $USER
    if (isset($USER->preference[$name])) {
        unset($USER->preference[$name]);
    }

    //Then from DB
    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 $userid A moodle user ID
 * @return bool
 */
function set_user_preferences($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 float $timezone ?
 * @param bool $applydst ?
 * @return int timestamp
 * @todo Finish documenting this function
 */
function make_timestamp($year, $month=1, $day=1, $hour=0, $minute=0, $second=0, $timezone=99, $applydst=true) {

    $timezone = get_user_timezone_offset($timezone);

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

    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 timestamp in GMT
 * @param string $format strftime format
 * @param float $timezone
 * @param bool $fixday If true (default) then the leading
 * zero from %d is removed. If false then the leading zero is mantained.
 * @return string
 */
function userdate($date, $format='', $timezone=99, $fixday = true) {

    global $CFG;

    static $strftimedaydatetime;

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

    if (!empty($CFG->nofixday)) {  // Config.php can force %d not to be fixed.
        $fixday = false;
    } else if ($fixday) {
        $formatnoday = str_replace('%d', 'DD', $format);
        $fixday = ($formatnoday != $format);
    }

    $date += dst_offset_on($date);

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {   /// Server time
        if ($fixday) {
            $datestring = strftime($formatnoday, $date);
            $daystring  = str_replace(' 0', '', strftime(' %d', $date));
            $datestring = str_replace('DD', $daystring, $datestring);
        } else {
            $datestring = strftime($format, $date);
        }
    } else {
        $date += (int)($timezone * 3600);
        if ($fixday) {
            $datestring = gmstrftime($formatnoday, $date);
            $daystring  = str_replace(' 0', '', gmstrftime(' %d', $date));
            $datestring = str_replace('DD', $daystring, $datestring);
        } else {
            $datestring = gmstrftime($format, $date);
        }
    }

/// If we are running under Windows convert from windows encoding to UTF-8
/// (because it's impossible to specify UTF-8 to fetch locale info in Win32)

   if ($CFG->ostype == 'WINDOWS') {
       if ($localewincharset = get_string('localewincharset')) {
           $textlib = textlib_get_instance();
           $datestring = $textlib->convert($datestring, $localewincharset, 'utf-8');
       }
   }

    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 float $timezone ?
 * @return array An array that represents the date in user time
 * @todo Finish documenting this function
 */
function usergetdate($time, $timezone=99) {

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {    // Server time
        return getdate($time);
    }

    // There is no gmgetdate so we use gmdate instead
    $time += dst_offset_on($time);
    $time += intval((float)$timezone * HOURSECS);

    $datestring = gmstrftime('%S_%M_%H_%d_%m_%Y_%w_%j_%A_%B', $time);

    list(
        $getdate['seconds'],
        $getdate['minutes'],
        $getdate['hours'],
        $getdate['mday'],
        $getdate['mon'],
        $getdate['year'],
        $getdate['wday'],
        $getdate['yday'],
        $getdate['weekday'],
        $getdate['month']
    ) = explode('_', $datestring);

    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 float $timezone
 * @return int
 */
function usertime($date, $timezone=99) {

    $timezone = get_user_timezone_offset($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 float $timezone ?
 * @return ?
 */
function usergetmidnight($date, $timezone=99) {

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

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

}

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

    $tz = get_user_timezone($timezone);

    if (!is_float($tz)) {
        return $tz;
    }

    if(abs($tz) > 13) { // Server time
        return get_string('serverlocaltime');
    }

    if($tz == intval($tz)) {
        // Don't show .0 for whole hours
        $tz = intval($tz);
    }

    if($tz == 0) {
        return 'GMT';
    }
    else if($tz > 0) {
        return 'GMT+'.$tz;
    }
    else {
        return 'GMT'.$tz;
    }

}

/**
 * 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 float $tz If this value is provided and not equal to 99, it will be returned as is and no other settings will be checked
 * @return int
 */
function get_user_timezone_offset($tz = 99) {

    global $USER, $CFG;

    $tz = get_user_timezone($tz);

    if (is_float($tz)) {
        return $tz;
    } else {
        $tzrecord = get_timezone_record($tz);
        if (empty($tzrecord)) {
            return 99.0;
        }
        return (float)$tzrecord->gmtoff / HOURMINS;
    }
}

/**
 * Returns a float or a string which denotes the user's timezone
 * A float value means that a simple offset from GMT is used, while a string (it will be the name of a timezone in the database)
 * means that for this timezone there are also DST rules to be taken into account
 * Checks various settings and picks the most dominant of those which have a value
 *
 * @uses $USER
 * @uses $CFG
 * @param float $tz If this value is provided and not equal to 99, it will be returned as is and no other settings will be checked
 * @return mixed
 */
function get_user_timezone($tz = 99) {
    global $USER, $CFG;

    $timezones = array(
        $tz,
        isset($CFG->forcetimezone) ? $CFG->forcetimezone : 99,
        isset($USER->timezone) ? $USER->timezone : 99,
        isset($CFG->timezone) ? $CFG->timezone : 99,
        );

    $tz = 99;

    while(($tz == '' || $tz == 99) && $next = each($timezones)) {
        $tz = $next['value'];
    }

    return is_numeric($tz) ? (float) $tz : $tz;
}

/**
 * ?
 *
 * @uses $CFG
 * @uses $db
 * @param string $timezonename ?
 * @return object
 */
function get_timezone_record($timezonename) {
    global $CFG, $db;
    static $cache = NULL;

    if ($cache === NULL) {
        $cache = array();
    }

    if (isset($cache[$timezonename])) {
        return $cache[$timezonename];
    }

    return $cache[$timezonename] = get_record_sql('SELECT * FROM '.$CFG->prefix.'timezone
                                      WHERE name = '.$db->qstr($timezonename).' ORDER BY year DESC', true);
}

/**
 * ?
 *
 * @uses $CFG
 * @uses $USER
 * @param ? $fromyear ?
 * @param ? $to_year ?
 * @return bool
 */
function calculate_user_dst_table($from_year = NULL, $to_year = NULL) {
    global $CFG, $SESSION;

    $usertz = get_user_timezone();

    if (is_float($usertz)) {
        // Trivial timezone, no DST
        return false;
    }

    if (!empty($SESSION->dst_offsettz) && $SESSION->dst_offsettz != $usertz) {
        // We have precalculated values, but the user's effective TZ has changed in the meantime, so reset
        unset($SESSION->dst_offsets);
        unset($SESSION->dst_range);
    }

    if (!empty($SESSION->dst_offsets) && empty($from_year) && empty($to_year)) {
        // Repeat calls which do not request specific year ranges stop here, we have already calculated the table
        // This will be the return path most of the time, pretty light computationally
        return true;
    }

    // Reaching here means we either need to extend our table or create it from scratch

    // Remember which TZ we calculated these changes for
    $SESSION->dst_offsettz = $usertz;

    if(empty($SESSION->dst_offsets)) {
        // If we 're creating from scratch, put the two guard elements in there
        $SESSION->dst_offsets = array(1 => NULL, 0 => NULL);
    }
    if(empty($SESSION->dst_range)) {
        // If creating from scratch
        $from = max((empty($from_year) ? intval(date('Y')) - 3 : $from_year), 1971);
        $to   = min((empty($to_year)   ? intval(date('Y')) + 3 : $to_year),   2035);

        // Fill in the array with the extra years we need to process
        $yearstoprocess = array();
        for($i = $from; $i <= $to; ++$i) {
            $yearstoprocess[] = $i;
        }

        // Take note of which years we have processed for future calls
        $SESSION->dst_range = array($from, $to);
    }
    else {
        // If needing to extend the table, do the same
        $yearstoprocess = array();

        $from = max((empty($from_year) ? $SESSION->dst_range[0] : $from_year), 1971);
        $to   = min((empty($to_year)   ? $SESSION->dst_range[1] : $to_year),   2035);

        if($from < $SESSION->dst_range[0]) {
            // Take note of which years we need to process and then note that we have processed them for future calls
            for($i = $from; $i < $SESSION->dst_range[0]; ++$i) {
                $yearstoprocess[] = $i;
            }
            $SESSION->dst_range[0] = $from;
        }
        if($to > $SESSION->dst_range[1]) {
            // Take note of which years we need to process and then note that we have processed them for future calls
            for($i = $SESSION->dst_range[1] + 1; $i <= $to; ++$i) {
                $yearstoprocess[] = $i;
            }
            $SESSION->dst_range[1] = $to;
        }
    }

    if(empty($yearstoprocess)) {
        // This means that there was a call requesting a SMALLER range than we have already calculated
        return true;
    }

    // From now on, we know that the array has at least the two guard elements, and $yearstoprocess has the years we need
    // Also, the array is sorted in descending timestamp order!

    // Get DB data
    $presetrecords = get_records('timezone', 'name', $usertz, 'year DESC', 'year, gmtoff, dstoff, dst_month, dst_startday, dst_weekday, dst_skipweeks, dst_time, std_month, std_startday, std_weekday, std_skipweeks, std_time');
    if(empty($presetrecords)) {
        return false;
    }

    // Remove ending guard (first element of the array)
    reset($SESSION->dst_offsets);
    unset($SESSION->dst_offsets[key($SESSION->dst_offsets)]);

    // Add all required change timestamps
    foreach($yearstoprocess as $y) {
        // Find the record which is in effect for the year $y
        foreach($presetrecords as $year => $preset) {
            if($year <= $y) {
                break;
            }
        }

        $changes = dst_changes_for_year($y, $preset);

        if($changes === NULL) {
            continue;
        }
        if($changes['dst'] != 0) {
            $SESSION->dst_offsets[$changes['dst']] = $preset->dstoff * MINSECS;
        }
        if($changes['std'] != 0) {
            $SESSION->dst_offsets[$changes['std']] = 0;
        }
    }

    // Put in a guard element at the top
    $maxtimestamp = max(array_keys($SESSION->dst_offsets));
    $SESSION->dst_offsets[($maxtimestamp + DAYSECS)] = NULL; // DAYSECS is arbitrary, any "small" number will do

    // Sort again
    krsort($SESSION->dst_offsets);

    return true;
}

function dst_changes_for_year($year, $timezone) {

    if($timezone->dst_startday == 0 && $timezone->dst_weekday == 0 && $timezone->std_startday == 0 && $timezone->std_weekday == 0) {
        return NULL;
    }

    $monthdaydst = find_day_in_month($timezone->dst_startday, $timezone->dst_weekday, $timezone->dst_month, $year);
    $monthdaystd = find_day_in_month($timezone->std_startday, $timezone->std_weekday, $timezone->std_month, $year);

    list($dst_hour, $dst_min) = explode(':', $timezone->dst_time);
    list($std_hour, $std_min) = explode(':', $timezone->std_time);

    $timedst = make_timestamp($year, $timezone->dst_month, $monthdaydst, 0, 0, 0, 99, false);
    $timestd = make_timestamp($year, $timezone->std_month, $monthdaystd, 0, 0, 0, 99, false);

    // Instead of putting hour and minute in make_timestamp(), we add them afterwards.
    // This has the advantage of being able to have negative values for hour, i.e. for timezones
    // where GMT time would be in the PREVIOUS day than the local one on which DST changes.

    $timedst += $dst_hour * HOURSECS + $dst_min * MINSECS;
    $timestd += $std_hour * HOURSECS + $std_min * MINSECS;

    return array('dst' => $timedst, 0 => $timedst, 'std' => $timestd, 1 => $timestd);
}

// $time must NOT be compensated at all, it has to be a pure timestamp
function dst_offset_on($time) {
    global $SESSION;

    if(!calculate_user_dst_table() || empty($SESSION->dst_offsets)) {
        return 0;
    }

    reset($SESSION->dst_offsets);
    while(list($from, $offset) = each($SESSION->dst_offsets)) {
        if($from <= $time) {
            break;
        }
    }

    // This is the normal return path
    if($offset !== NULL) {
        return $offset;
    }

    // Reaching this point means we haven't calculated far enough, do it now:
    // Calculate extra DST changes if needed and recurse. The recursion always
    // moves toward the stopping condition, so will always end.

    if($from == 0) {
        // We need a year smaller than $SESSION->dst_range[0]
        if($SESSION->dst_range[0] == 1971) {
            return 0;
        }
        calculate_user_dst_table($SESSION->dst_range[0] - 5, NULL);
        return dst_offset_on($time);
    }
    else {
        // We need a year larger than $SESSION->dst_range[1]
        if($SESSION->dst_range[1] == 2035) {
            return 0;
        }
        calculate_user_dst_table(NULL, $SESSION->dst_range[1] + 5);
        return dst_offset_on($time);
    }
}

function find_day_in_month($startday, $weekday, $month, $year) {

    $daysinmonth = days_in_month($month, $year);

    if($weekday == -1) {
        // Don't care about weekday, so return:
        //    abs($startday) if $startday != -1
        //    $daysinmonth otherwise
        return ($startday == -1) ? $daysinmonth : abs($startday);
    }

    // From now on we 're looking for a specific weekday

    // Give "end of month" its actual value, since we know it
    if($startday == -1) {
        $startday = -1 * $daysinmonth;
    }

    // Starting from day $startday, the sign is the direction

    if($startday < 1) {

        $startday = abs($startday);
        $lastmonthweekday  = strftime('%w', mktime(12, 0, 0, $month, $daysinmonth, $year, 0));

        // This is the last such weekday of the month
        $lastinmonth = $daysinmonth + $weekday - $lastmonthweekday;
        if($lastinmonth > $daysinmonth) {
            $lastinmonth -= 7;
        }

        // Find the first such weekday <= $startday
        while($lastinmonth > $startday) {
            $lastinmonth -= 7;
        }

        return $lastinmonth;

    }
    else {

        $indexweekday = strftime('%w', mktime(12, 0, 0, $month, $startday, $year, 0));

        $diff = $weekday - $indexweekday;
        if($diff < 0) {
            $diff += 7;
        }

        // This is the first such weekday of the month equal to or after $startday
        $firstfromindex = $startday + $diff;

        return $firstfromindex;

    }
}

/**
 * Calculate the number of days in a given month
 *
 * @param int $month The month whose day count is sought
 * @param int $year The year of the month whose day count is sought
 * @return int
 */
function days_in_month($month, $year) {
   return intval(date('t', mktime(12, 0, 0, $month, 1, $year, 0)));
}

/**
 * Calculate the position in the week of a specific calendar day
 *
 * @param int $day The day of the date whose position in the week is sought
 * @param int $month The month of the date whose position in the week is sought
 * @param int $year The year of the date whose position in the week is sought
 * @return int
 */
function dayofweek($day, $month, $year) {
    // I wonder if this is any different from
    // strftime('%w', mktime(12, 0, 0, $month, $daysinmonth, $year, 0));
    return intval(date('w', mktime(12, 0, 0, $month, $day, $year, 0)));
}

/// 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.
 *
 * @uses $USER
 * @return string
 */
function sesskey() {
    global $USER;

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

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

    return $USER->sesskey;
}


/**
 * 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 $sesskey optionally provided sesskey
 * @return bool
 */
function confirm_sesskey($sesskey=NULL) {
    global $USER;

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

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

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

    return ($USER->sesskey === $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 $COURSE
 * @uses $MoodleSession
 * @param int $courseid id of the course
 * @param bool $autologinguest
 * @param object $cm course module object
 */
function require_login($courseid=0, $autologinguest=true, $cm=null) {

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

/// Redefine global $COURSE if we can
    global $course;  // We use the global hack once here so it doesn't need to be used again
    if (is_object($course) and !empty($course->id) and ($courseid == 0 || $course->id == $courseid)) {
        $COURSE = clone($course);
    } else if ($courseid) {
        $COURSE = get_record('course', 'id', $courseid);
    }

    if (!empty($COURSE->lang)) {
        $CFG->courselang = $COURSE->lang;
        moodle_setlocale();
    }

/// If the user is not even logged in yet then make sure they are
    if (! (isset($USER->loggedin) and $USER->confirmed and ($USER->site == $CFG->wwwroot)) ) {
        $SESSION->wantsurl = $FULLME;
        if (!empty($_SERVER['HTTP_REFERER'])) {
            $SESSION->fromurl  = $_SERVER['HTTP_REFERER'];
        }
        $USER = NULL;
        if ($autologinguest && !empty($CFG->autologinguests) and 
            $courseid and ($courseid == SITEID or 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);
        }
        exit;
    }

/// check whether the user should be changing password
    if (!empty($USER->preference['auth_forcepasswordchange'])){
        if (is_internal_auth() || $CFG->{'auth_'.$USER->auth.'_stdchangepassword'}){
            $SESSION->wantsurl = $FULLME;
            if (empty($CFG->loginhttps)) {
                redirect($CFG->wwwroot .'/login/change_password.php');
            } else {
                $wwwroot = str_replace('http:','https:', $CFG->wwwroot);
                redirect($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)) {
        $SESSION->wantsurl = $FULLME;
        redirect($CFG->wwwroot .'/user/edit.php?id='. $USER->id .'&amp;course='. SITEID);
    }

/// 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');
        }
    }

/// If the site is currently under maintenance, then print a message
    if (!has_capability('moodle/site:config',get_context_instance(CONTEXT_SYSTEM, SITEID))) {
        if (file_exists($CFG->dataroot.'/'.SITEID.'/maintenance.html')) {
            print_maintenance_message();
            exit;
        }
    }

/// Next, check if the user can be in a particular course
    if ($courseid) {

    /// Sanity check on the courseid

        if ($courseid == $COURSE->id) {     /// Pretty much always true but let's be sure
            $course = $COURSE;
        } else if (! $course = get_record('course', 'id', $courseid)) {
            error('That course doesn\'t exist');
        }

    /// We can eliminate hidden site activities straight away

        if ($course->id == SITEID) {
            if (!empty($cm) && !$cm->visible and !has_capability('moodle/course:viewhiddenactivities', 
                                                          get_context_instance(CONTEXT_SYSTEM, SITEID))) {
                redirect($CFG->wwwroot, get_string('activityiscurrentlyhidden'));
            }
            return;
        }

 
    /// If the whole course is hidden from us then we can stop now

        if (!$context = get_context_instance(CONTEXT_COURSE, $course->id)) {
            print_error('nocontext');
        }

        if (empty($USER->switchrole[$context->id]) &&
            !($course->visible && course_parent_visible($course)) &&
               !has_capability('moodle/course:viewhiddencourses', get_context_instance(CONTEXT_COURSE, $course->id)) ){
            print_header_simple();
            notice(get_string('coursehidden'), $CFG->wwwroot .'/');
        }    
        
    /// Non-guests who don't currently have access, check if they can be allowed in as a guest

        if ($USER->username != 'guest' and !has_capability('moodle/course:view', $context)) {
            if ($course->guest == 1) {
                 // Temporarily assign them guest role for this context,
                 // if it fails user is asked to enrol
                 load_guest_role($context);
            }
        }

    /// If the user is a guest then treat them according to the course policy about guests

        if (has_capability('moodle/legacy:guest', $context, NULL, false)) {
            switch ($course->guest) {    /// Check course policy about guest access

                case 1:    /// Guests always allowed 
                    if (!has_capability('moodle/course:view', $context)) {    // Prohibited by capability
                        print_header_simple();
                        notice(get_string('guestsnotallowed', '', $course->fullname), "$CFG->wwwroot/login/index.php");
                    }
                    if (!empty($cm) and !$cm->visible) { // Not allowed to see module, send to course page
                        redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course, 
                                 get_string('activityiscurrentlyhidden'));
                    }

                    return;   // User is allowed to see this course

                    break;

                case 2:    /// Guests allowed with key 
                    if (!empty($USER->enrolkey[$course->id])) {   // Set by enrol/manual/enrol.php
                        return true;
                    }
                    //  otherwise drop through to logic below (--> enrol.php)
                    break;

                default:    /// Guests not allowed
                    print_header_simple('', '', get_string('loggedinasguest'));
                    if (empty($USER->switchrole[$context->id])) {  // Normal guest
                        notice(get_string('guestsnotallowed', '', $course->fullname), "$CFG->wwwroot/login/index.php");
                    } else {
                        notify(get_string('guestsnotallowed', '', $course->fullname));
                        echo '<div class="notifyproblem">'.switchroles_form($course->id).'</div>';
                        print_footer($course);
                        exit;
                    }
                    break;
            }

    /// For non-guests, check if they have course view access

        } else if (has_capability('moodle/course:view', $context)) {
            if (!empty($USER->realuser)) {   // Make sure the REAL person can also access this course
                if (!has_capability('moodle/course:view', $context, $USER->realuser)) {
                    print_header_simple();
                    notice(get_string('studentnotallowed', '', fullname($USER, true)), $CFG->wwwroot .'/');
                }
            }

        /// Make sure they can read this activity too, if specified

            if (!empty($cm) and !$cm->visible and !has_capability('moodle/course:viewhiddenactivities', $context)) { 
                redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course, get_string('activityiscurrentlyhidden'));
            }
            return;   // User is allowed to see this course

        }


    /// 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 function just makes sure a user is logged out.
 *
 * @uses $CFG
 * @uses $USER
 */
function require_logout() {

    global $USER, $CFG;

    if (isset($USER) and isset($USER->id)) {
        add_to_log(SITEID, "user", "logout", "view.php?id=$USER->id&course=".SITEID, $USER->id, 0, $USER->id);

        if ($USER->auth == 'cas' && !empty($CFG->cas_enabled)) {
            require($CFG->dirroot.'/auth/cas/logout.php');
        }
    }

    if (ini_get_bool("register_globals") and check_php_version("4.3.0")) {
        // This method is just to try to avoid silly warnings from PHP 4.3.0
        session_unregister("USER");
        session_unregister("SESSION");
    }

    setcookie('MoodleSessionTest'.$CFG->sessioncookie, '', time() - 3600, $CFG->sessioncookiepath);
    unset($_SESSION['USER']);
    unset($_SESSION['SESSION']);

    unset($SESSION);
    unset($USER);

}

/**
 * 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 object $course The course object in question
 * @param bool $autologinguest Allow autologin guests if that is wanted
 * @param object $cm Course activity module if known
 */
function require_course_login($course, $autologinguest=true, $cm=null) {
    global $CFG;
    if (!empty($CFG->forcelogin)) {
        require_login();
    }
    if ($course->id != SITEID) {
        require_login($course->id, $autologinguest, $cm);
    }
}

/**
 * Modify the user table by setting the currently logged in user's
 * last login to now.
 *
 * @uses $USER
 * @return bool
 */
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 $USER} object to test for the existance of a valid name and email
 * @return bool
 */
function user_not_fully_set_up($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, false);
    }
}

/**
* @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, false);
    }
}

/**
 * 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;
}

function sync_metacourses() {

    global $CFG;

    if (!$courses = get_records('course', 'metacourse', 1)) {
        return;
    }

    foreach ($courses as $course) {
        sync_metacourse($course);
    }
}

/**
 * Goes through all enrolment records for the courses inside the metacourse and sync with them.
 * 
 * @param mixed $course the metacourse to synch. Either the course object itself, or the courseid.
 */
function sync_metacourse($course) {
    global $CFG;

    // Check the course is valid.
    if (!is_object($course)) {
        if (!$course = get_record('course', 'id', $course)) {
            return false; // invalid course id
        }
    }
    
    // Check that we actually have a metacourse.
    if (empty($course->metacourse)) {
        return false;
    }

    // Get the context of the metacourse.
    $context = get_context_instance(CONTEXT_COURSE, $course->id); // SITEID can not be a metacourse

    // We do not ever want to unassign the list of metacourse manager, so get a list of them.
    if ($users = get_users_by_capability($context, 'moodle/course:managemetacourse')) {
        $managers = array_keys($users);
    } else {
        $managers = array();
    }

    // Get assignments of a user to a role that exist in a child course, but
    // not in the meta coure. That is, get a list of the assignments that need to be made.
    if (!$assignments = get_records_sql("
            SELECT
                ra.id, ra.roleid, ra.userid
            FROM
                {$CFG->prefix}role_assignments ra,
                {$CFG->prefix}context con,
                {$CFG->prefix}course_meta cm
            WHERE
                ra.contextid = con.id AND
                con.contextlevel = " . CONTEXT_COURSE . " AND
                con.instanceid = cm.child_course AND
                cm.parent_course = {$course->id} AND
                NOT EXISTS (
                    SELECT 1 FROM
                        {$CFG->prefix}role_assignments ra2
                    WHERE
                        ra2.userid = ra.userid AND
                        ra2.roleid = ra.roleid AND
                        ra2.contextid = {$context->id}
                )
    ")) {
        $assignments = array();
    }

    // Get assignments of a user to a role that exist in the meta course, but
    // not in any child courses. That is, get a list of the unassignments that need to be made.
    if (!$unassignments = get_records_sql("
            SELECT
                ra.id, ra.roleid, ra.userid
            FROM
                {$CFG->prefix}role_assignments ra
            WHERE
                ra.contextid = {$context->id} AND
                NOT EXISTS (
                    SELECT 1 FROM
                        {$CFG->prefix}role_assignments ra2,
                        {$CFG->prefix}context con2,
                        {$CFG->prefix}course_meta cm
                    WHERE
                        ra2.userid = ra.userid AND
                        ra2.roleid = ra.roleid AND
                        ra2.contextid = con2.id AND
                        con2.contextlevel = " . CONTEXT_COURSE . " AND
                        con2.instanceid = cm.child_course AND
                        cm.parent_course = {$course->id}
                )
    ")) {
        $unassignments = array();
    }

    $success = true;

    // Make the unassignments, if they are not managers.
    foreach ($unassignments as $unassignment) {
        if (!in_array($unassignment->userid, $managers)) {
            $success = role_unassign($unassignment->roleid, $unassignment->userid, 0, $context->id) && $success;
        }
    }

    // Make the assignments.
    foreach ($assignments as $assignment) {
        $success = role_assign($assignment->roleid, $assignment->userid, 0, $context->id) && $success;
    }

    return $success;
    
// TODO: finish timeend and timestart
// maybe we could rely on cron job to do the cleaning from time to time
}

/**
 * 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 is currently logged in
 *
 * @uses $USER
 * @return bool
 */
function isloggedin() {
    global $USER;

    return (!empty($USER->id));
}


/**
 * 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 $USER} object. If null then the currently logged in user is used.
 * @return bool
 */
function isediting($courseid, $user=NULL) {
    global $USER;
    if (!$user) {
        $user = $USER;
    }
    if (empty($user->editing)) {
        return false;
    }
    return ($user->editing and has_capability('moodle/course:manageactivities', get_context_instance(CONTEXT_COURSE, $courseid)));
}

/**
 * Determines if the logged in user is currently moving an activity
 *
 * @uses $USER
 * @param int $courseid The id of the course being tested
 * @return bool
 */
function ismoving($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 object $user A {@link $USER} object to get full name of
 * @param bool $override If true then the name will be first name followed by last name rather than adhering to fullnamedisplay setting.
 */
function fullname($user, $override=false) {

    global $CFG, $SESSION;

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

    if (!$override) {
        if (!empty($CFG->forcefirstname)) {
            $user->firstname = $CFG->forcefirstname;
        }
        if (!empty($CFG->forcelastname)) {
            $user->lastname = $CFG->forcelastname;
        }
    }

    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;

    if ($thing == 'guest') {  // Ignore guest account
        return;
    }

    $cookiename = 'MOODLEID_'.$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 {
        $thing = rc4decrypt($_COOKIE[$cookiename]);
        return ($thing == 'guest') ? '': $thing;  // Ignore guest account
    }
}

/**
 * Returns true if an internal authentication method is being used.
 * if method not specified then, global default is assumed
 *
 * @uses $CFG
 * @param string $auth Form of authentication required
 * @return bool
 * @todo Outline auth types and provide code example
 */
function is_internal_auth($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
 */
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 object 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 = $username;
    update_internal_user_password($newuser, $password, false);
    $newuser->lang = $CFG->lang;
    $newuser->confirmed = 1;
    $newuser->lastip = getremoteaddr();
    $newuser->timemodified = time();

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

        $oldinfo = get_record('user', 'username', $username, '','','','', 'username, auth');
        $authconfig = get_config('auth/' . $oldinfo->auth);

        if ($newinfo = auth_get_userinfo($username)) {
            $newinfo = truncate_userinfo($newinfo);
            foreach ($newinfo as $key => $value){
                $confkey = 'field_updatelocal_' . $key;
                if (!empty($authconfig->$confkey) && $authconfig->$confkey === 'onlogin') {
                    $value = addslashes(stripslashes($value));   // Just in case
                    set_field('user', $key, $value, 'username', $username)
                        || error_log("Error updating $key for $username");
                }
            }
        }
    }
    return get_complete_user_data('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'   => 100,
                    'lastname'    => 100,
                    '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;

    // First try to find the user in the database

    if (!$user = get_complete_user_data('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($user->auth)) {      // For some reason it isn't set yet
        if (!empty($user->id) && (isadmin($user->id) || isguest($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->id) {                          // User already exists in database
            if (empty($user->auth)) {             // For some reason auth isn't set yet
                set_field('user', 'auth', $auth, 'username', $username);
            }
            update_internal_user_password($user, $password);
            if (!is_internal_auth()) {            // update user record from external DB
                $user = update_user_record($username);
            }
        } else {
            $user = create_user_record($username, $password, $auth);
        }
        // fix for MDL-6928    
        if (function_exists('auth_iscreator')) {                    
            $sitecontext = get_context_instance(CONTEXT_SYSTEM);
            if ($creatorroles = get_roles_with_capability('moodle/legacy:coursecreator', CAP_ALLOW)) {
                $creatorrole = array_shift($creatorroles); // We can only use one, let's use the first one
                // Check if the user is a creator
                if (auth_iscreator($username)) { // Following calls will not create duplicates
                    role_assign($creatorrole->id, $user->id, 0, $sitecontext->id, 0, 0, 0, $auth);
                } else {
                    role_unassign($creatorrole->id, $user->id, 0, $sitecontext->id);
                }
            }
        }

    /// Log in to a second system if necessary
        if (!empty($CFG->sso)) {
            include_once($CFG->dirroot .'/sso/'. $CFG->sso .'/lib.php');
            if (function_exists('sso_user_login')) {
                if (!sso_user_login($username, $password)) {   // Perform the signon process
                    notify('Second sign-on failed');
                }
            }
        }

        return $user;

    } else {
        add_to_log(0, 'login', 'error', 'index.php', $username);
        error_log('[client '.$_SERVER['REMOTE_ADDR']."]  $CFG->wwwroot  Failed Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
        return false;
    }
}

/**
 * Compare password against hash stored in internal user table.
 * If necessary it also updates the stored hash to new format.
 * 
 * @param object user
 * @param string plain text password
 * @return bool is password valid?
 */
function validate_internal_user_password(&$user, $password) {
    global $CFG;

    if (!isset($CFG->passwordsaltmain)) {
        $CFG->passwordsaltmain = '';
    }

    $validated = false;

	// get password original encoding in case it was not updated to unicode yet
    $textlib = textlib_get_instance();
    $convpassword = $textlib->convert($password, 'utf-8', get_string('oldcharset'));

    if ($user->password == md5($password.$CFG->passwordsaltmain) or $user->password == md5($password)
        or $user->password == md5($convpassword.$CFG->passwordsaltmain) or $user->password == md5($convpassword)) {
        $validated = true;
    } else {
        for ($i=1; $i<=20; $i++) { //20 alternative salts should be enough, right?
            $alt = 'passwordsaltalt'.$i;
            if (!empty($CFG->$alt)) {
                if ($user->password == md5($password.$CFG->$alt) or $user->password == md5($convpassword.$CFG->$alt)) {
                    $validated = true;
                    break;
                }
            }
        }
    }

    if ($validated) {
        // force update of password hash using latest main password salt and encoding if needed
        update_internal_user_password($user, $password);
    }

    return $validated;
}

/**
 * Calculate hashed value from password using current hash mechanism.
 * 
 * @param string password
 * @return string password hash
 */
function hash_internal_user_password($password) {
    global $CFG;

    if (isset($CFG->passwordsaltmain)) {
        return md5($password.$CFG->passwordsaltmain);
    } else {
        return md5($password);
    }
}

/**
 * Update pssword hash in user object.
 * 
 * @param object user
 * @param string plain text password
 * @param bool store changes also in db, default true
 * @return true if hash changed
 */
function update_internal_user_password(&$user, $password, $storeindb=true) {
    global $CFG;

    if (!empty($CFG->{$user->auth.'_preventpassindb'})) {
        $hashedpassword = 'not cached';
    } else {
        $hashedpassword = hash_internal_user_password($password);
    }

    if ($user->password != $hashedpassword) {
        if ($storeindb) {
            if (!set_field('user', 'password',  $hashedpassword, 'username', $user->username)) {
                return false;
            }
        }
        $user->password = $hashedpassword;
    }
    return true;
}

/**
 * Get a complete user record, which includes all the info
 * in the user record
 * Intended for setting as $USER session variable
 *
 * @uses $CFG
 * @uses SITEID
 * @param string $field The user field to be checked for a given value.
 * @param string $value The value to match for $field.
 * @return user A {@link $USER} object.
 */
function get_complete_user_data($field, $value) {

    global $CFG;

    if (!$field || !$value) {
        return false;
    }

/// Get all the basic user data

    if (! $user = get_record_select('user', $field .' = \''. $value .'\' AND deleted <> \'1\'')) {
        return false;
    }

/// Get various settings and preferences

    if ($displays = get_records('course_display', 'userid', $user->id)) {
        foreach ($displays as $display) {
            $user->display[$display->course] = $display->display;
        }
    }

    if ($preferences = get_records('user_preferences', 'userid', $user->id)) {
        foreach ($preferences as $preference) {
            $user->preference[$preference->name] = $preference->value;
        }
    }

    if ($lastaccesses = get_records('user_lastaccess', 'userid', $user->id)) {
        foreach ($lastaccesses as $lastaccess) {
            $user->lastcourseaccess[$lastaccess->courseid] = $lastaccess->timeaccess;
        }
    }

    if ($groups = get_records('groups_members', 'userid', $user->id)) {
        foreach ($groups as $groupmember) {
            $courseid = get_field('groups', 'courseid', 'id', $groupmember->groupid);
            //change this to 2D array so we can put multiple groups in a course
            $user->groupmember[$courseid][] = $groupmember->groupid;
        }
    }

/// Rewrite some variables if necessary
    if (!empty($user->description)) {
        $user->description = true;   // No need to cart all of it around
    }
    if ($user->username == 'guest') {
        $user->lang       = $CFG->lang;               // Guest language always same as site
        $user->firstname  = get_string('guestuser');  // Name always in current language
        $user->lastname   = ' ';
    }

    $user->loggedin = true;
    $user->site     = $CFG->wwwroot; // for added security, store the site in the session
    $user->sesskey  = random_string(10);
    $user->sessionIP = md5(getremoteaddr());   // Store the current IP in the session

    return $user;
}



/*
 * When logging in, this function is run to set certain preferences
 * for the current SESSION
 */
function set_login_session_preferences() {
    global $SESSION, $CFG;

    $SESSION->justloggedin = true;

    unset($SESSION->lang);

    // Restore the calendar filters, if saved
    if (intval(get_user_preferences('calendar_persistflt', 0))) {
        include_once($CFG->dirroot.'/calendar/lib.php');
        calendar_set_filters_status(get_user_preferences('calendav_savedflt', 0xff));
    }
}


/**
 * Delete a course, including all related data from the database,
 * and any associated files from the moodledata folder.
 *
 * @param int $courseid The id of the course to delete.
 * @param bool $showfeedback Whether to display notifications of each action the function performs.
 * @return bool true if all the removals succeeded. false if there were any failures. If this
 *             method returns false, some of the removals will probably have succeeded, and others
 *             failed, but you have no way of knowing which.
 */
function delete_course($courseid, $showfeedback = true) {
    global $CFG;
    $result = true;

    if (!remove_course_contents($courseid, $showfeedback)) {
        if ($showfeedback) {
            notify("An error occurred while deleting some of the course contents.");
        }
        $result = false;
    }

    if (!delete_records("course", "id", $courseid)) {
        if ($showfeedback) {
            notify("An error occurred while deleting the main course record.");
        }
        $result = false;
    }

    if (!delete_records('context', 'contextlevel', CONTEXT_COURSE, 'instanceid', $courseid)) {
        if ($showfeedback) {
            notify("An error occurred while deleting the main context record.");
        }
        $result = false;
    }

    if (!fulldelete($CFG->dataroot.'/'.$courseid)) {
        if ($showfeedback) {
            notify("An error occurred while deleting the course files.");
        }
        $result = false;
    }

    return $result;
}

/**
 * Clear a course out completely, deleting all content
 * but don't delete the course itself
 *
 * @uses $CFG
 * @param int $courseid The id of the course that is being deleted
 * @param bool $showfeedback Whether to display notifications of each action the function performs.
 * @return bool true if all the removals succeeded. false if there were any failures. If this
 *             method returns false, some of the removals will probably have succeeded, and others
 *             failed, but you have no way of knowing which.
 */
function remove_course_contents($courseid, $showfeedback=true) {

    global $CFG;

    $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 $instance) {
                            if ($cm = get_coursemodule_from_instance($modname, $instance->id, $course->id)) {
                                delete_context(CONTEXT_MODULE, $cm->id);
                            }
                            if ($moddelete($instance->id)) {
                                $count++;

                            } else {
                                notify('Could not delete '. $modname .' instance '. $instance->id .' ('. format_string($instance->name) .')');
                                $result = false;
                            }
                        }
                    }
                } else {
                    notify('Function '. $moddelete() .'doesn\'t exist!');
                    $result = false;
                }

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

/// Give local code a chance to delete its references to this course.
    require_once('locallib.php');
    notify_local_delete_course($courseid, $showfeedback);

/// Delete course blocks

    if ($blocks = get_records_sql("SELECT * 
                                   FROM {$CFG->prefix}block_instance
                                   WHERE pagetype = '".PAGE_COURSE_VIEW."'
                                   AND pageid = $course->id")) {
        if (delete_records('block_instance', 'pagetype', PAGE_COURSE_VIEW, 'pageid', $course->id)) {
            if ($showfeedback) {
                notify($strdeleted .' block_instance');
            }
            foreach ($blocks as $block) {  /// Delete any associated contexts for this block
                delete_context(CONTEXT_BLOCK, $block->id);
            }
        } else {
            $result = false;
        }
    }

/// Delete any groups
    if ($groups = get_records('groups', 'courseid', $course->id)) {
        if (delete_records('groups', 'courseid', $course->id)) {
            if ($showfeedback) {
                notify($strdeleted .' groups');
            }
            foreach ($groups as $group) {
                if (delete_records('groups_members', 'groupid', $group->id)) {
                    if ($showfeedback) {
                        notify($strdeleted .' groups_members');
                    }
                } else {
                    $result = false;
                }
                /// Delete any associated context for this group
                delete_context(CONTEXT_GROUP, $group->id);
            }
        } else {
            $result = false;
        }
    }

/// Delete all related records in other tables that may have a courseid
/// This array stores the tables that need to be cleared, as
/// table_name => column_name that contains the course id.

    $tablestoclear = array(
        'event' => 'courseid', // Delete events
        'log' => 'course', // Delete logs
        'course_sections' => 'course', // Delete any course stuff
        'course_modules' => 'course',
        'grade_category' => 'courseid', // Delete gradebook stuff
        'grade_exceptions' => 'courseid',
        'grade_item' => 'courseid',
        'grade_letter' => 'courseid',
        'grade_preferences' => 'courseid'
    );
    foreach ($tablestoclear as $table => $col) {
        if (delete_records($table, $col, $course->id)) {
            if ($showfeedback) {
                notify($strdeleted . ' ' . $table);
            }
        } else {
            $result = false;
        }
    }


/// Clean up metacourse stuff

    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");
            }
        }
    }

/// Delete questions and question categories
    include_once($CFG->libdir.'/questionlib.php');
    question_delete_course($course, $showfeedback);

/// Delete all roles and overiddes in the course context (but keep the course context)
    if ($courseid != SITEID) {
        delete_context(CONTEXT_COURSE, $course->id);
    }
    
    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 object $data an object containing all the boolean settings and courseid
 * @param bool $showfeedback  if false then do it all silently
 * @return bool
 * @todo Finish documenting this function
 */
function reset_course_userdata($data, $showfeedback=true) {

    global $CFG, $USER, $SESSION;

    $result = true;

    $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 = $modname .'_delete_userdata';   // Function to delete user data
            if (file_exists($modfile)) {
                @include_once($modfile);
                if (function_exists($moddeleteuserdata)) {
                    $moddeleteuserdata($data, $showfeedback);
                }
            }
        }
    } else {
        error('No modules are installed!');
    }

    // Delete other stuff
    $coursecontext = get_context_instance(CONTEXT_COURSE, $data->courseid);

    if (!empty($data->reset_students) or !empty($data->reset_teachers)) {
        $teachers     = array_keys(get_users_by_capability($coursecontext, 'moodle/course:update'));
        $participants = array_keys(get_users_by_capability($coursecontext, 'moodle/course:view'));
        $students     = array_diff($participants, $teachers);

        if (!empty($data->reset_students)) {
            foreach ($students as $studentid) {
                role_unassign(0, $studentid, 0, $coursecontext->id);
            }
            if ($showfeedback) {
                notify($strdeleted .' '.get_string('students'), 'notifysuccess');
            }

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

        if (!empty($data->reset_teachers)) {
            foreach ($teachers as $teacherid) {
                role_unassign(0, $teacherid, 0, $coursecontext->id);
            }
            if ($showfeedback) {
                notify($strdeleted .' '.get_string('teachers'), 'notifysuccess');
            }
        }
    }

    if (!empty($data->reset_groups)) {
        if ($groups = get_records('groups', 'courseid', $data->courseid)) {
            foreach ($groups as $group) {
                if (delete_records('groups', 'id', $group->id)) {
                    if ($showfeedback) {
                        notify($strdeleted .' groups', 'notifysuccess');
                    }
                } else {
                    $result = false;
                }
            }
        }
    }

    if (!empty($data->reset_events)) {
        if (delete_records('event', 'courseid', $data->courseid)) {
            if ($showfeedback) {
                notify($strdeleted .' event', 'notifysuccess');
            }
        } else {
            $result = false;
        }
    }

    if (!empty($data->reset_logs)) {
        if (delete_records('log', 'course', $data->courseid)) {
            if ($showfeedback) {
                notify($strdeleted .' log', 'notifysuccess');
            }
        } else {
            $result = false;
        }
    }

    // deletes all role assignments, and local override, these have no courseid in table and needs separate process
    $context = get_context_instance(CONTEXT_COURSE, $data->courseid);
    delete_records('role_capabilities', 'contextid', $context->id);

    return $result;
}


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


/**
 * Determines if the user a member of the given group
 *
 * @uses $USER
 * @param int $groupid The group to check the membership of
 * @param int $userid The user to check against the group
 * @return bool
 */
function ismember($groupid, $userid=0) {
    global $USER;

    if (!$groupid) {   // No point doing further checks
        return false;
    }
    //if groupid is supplied in array format
    if (!$userid) {
        if (empty($USER->groupmember)) {
            return false;
        }
        //changed too for multiple groups
        foreach ($USER->groupmember as $courseid => $mgroupid) {
            //need to loop one more time...
            if (is_array($mgroupid)) {
                foreach ($mgroupid as $index => $mygroupid) {
                    if ($mygroupid == $groupid) {
                        return true;
                    }
                }
            } else if ($mgroupid == $groupid) {
                return true;
            }
        }
        return false;
    }

    if (is_array($groupid)){
        foreach ($groupid as $index => $val){
            if (record_exists('groups_members', 'groupid', $val, 'userid', $userid)){
                return true;
            }
        }
    }
    else {
        return record_exists('groups_members', 'groupid', $groupid, 'userid', $userid);
    }
    return false;

    //else group id is in single format

    //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 int $groupid  The group id to add user to
 * @param int $userid   The user id to add to the group
 * @return bool
 */
function add_user_to_group ($groupid, $userid) {
    if (ismember($groupid, $userid)) return true;
    $record->groupid = $groupid;
    $record->userid = $userid;
    $record->timeadded = time();
    return (insert_record('groups_members', $record) !== false);
}


/**
 * Get the group ID of the current user in the given course
 *
 * @uses $USER
 * @param int $courseid The course being examined - relates to id field in 'course' table.
 * @return int
 */
function mygroupid($courseid) {
    global $USER;
    if (empty($USER->groupmember[$courseid])) {
        return 0;
    } else {
        //this is an array of ids >.<
        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 object $cm A course module object
 * @return int A group mode (NOGROUPS, SEPARATEGROUPS or VISIBLEGROUPS)
 */
function groupmode($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 $groupid The group being examined.
 * @return int Current group id which was set by this function
 */
function set_current_group($courseid, $groupid) {
    global $SESSION;

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


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

    if (!isset($SESSION->currentgroup[$courseid])) {
        if (empty($USER->groupmember[$courseid]) or has_capability('moodle/site:accessallgroups', get_context_instance(CONTEXT_COURSE, $courseid))) {

            return 0;
        } else {
            //trying to add a hack >.<, always first select the first one in list
            $SESSION->currentgroup[$courseid] = $USER->groupmember[$courseid][0];
        }
    }

    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 $groupid Will try to use this optional parameter to
 *            reset the current group for the user
 * @return int|false Returns the current group id or false if error.
 */
function get_and_set_current_group($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 (has_capability('moodle/site:accessallgroups', get_context_instance(CONTEXT_COURSE, $course->id))) {          // Sets current default group
                $currentgroupid = set_current_group($course->id, $group->id);

            } else if ($groupmode == VISIBLEGROUPS) {
                  // All groups are visible
                //if (ismember($group->id)){
                    $currentgroupid = set_current_group($course->id, $group->id);//set this since he might post
                /*)}else {
                    $currentgroupid = $group->id;*/
            } else if ($groupmode == SEPARATEGROUPS) { // student in separate groups switching
                if (ismember($group->id)){//check if is a member
                    $currentgroupid = set_current_group($course->id, $group->id); //might need to set_current_group?
                }
                else {
                    echo ($group->id);
                    notify('you do not belong to this group!',error);
                }
            }
        }
    } else {             // When groupid = 0 it means show ALL groups
        //this is changed, non editting teacher needs access to group 0 as well, for viewing work in visible groups (need to set current group for multiple pages)
        if (has_capability('moodle/site:accessallgroups', get_context_instance(CONTEXT_COURSE, $course->id)) AND ($groupmode == VISIBLEGROUPS)) {          // 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 $urlroot ?
 * @return int|false
 */
function setup_and_print_groups($course, $groupmode, $urlroot) {

    global $USER, $SESSION; //needs his id, need to hack his groups in session

    $changegroup = optional_param('group', -1, PARAM_INT);

    $currentgroup = get_and_set_current_group($course, $groupmode, $changegroup);
    if ($currentgroup === false) {
        return false;
    }

    if ($groupmode == SEPARATEGROUPS and !has_capability('moodle/site:accessallgroups', get_context_instance(CONTEXT_COURSE, $course->id)) and !$currentgroup) {
        //we are in separate groups and the current group is group 0, as last set.
        //this can mean that either, this guy has no group
        //or, this guy just came from a visible all forum, and he left when he set his current group to 0 (show all)

        //for the second situation, we need to perform the trick and get him a group.
        $courseid = $course->id;
        if (!empty($USER->groupmember[$courseid])){
            $currentgroup = get_and_set_current_group($course, $groupmode, $USER->groupmember[$courseid][0]);
        }
        else {//else he has no group in this course
            print_heading(get_string('notingroup'));
            print_footer($course);
            exit;
        }
    }

    if ($groupmode == VISIBLEGROUPS or ($groupmode and has_capability('moodle/site:accessallgroups', get_context_instance(CONTEXT_COURSE, $course->id)))) {
        if ($groups = get_records_menu('groups', 'courseid', $course->id, 'name ASC', 'id,name')) {
            echo '<div align="center">';
            print_group_menu($groups, $groupmode, $currentgroup, $urlroot);
            echo '</div>';
        }
    }//added code here to allow non-editting teacher to swap in-between his own groups
    //added code for students in separategrous to swtich groups
    else if ($groupmode == SEPARATEGROUPS and has_capability('moodle/course:view', get_context_instance(CONTEXT_COURSE, $course->id))) {
        $validgroups = array();
        //get all the groups this guy is in in this course
        if ($p = user_group($course->id,$USER->id)){
            //extract the name and id for the group
            foreach ($p as $index => $object){
                $validgroups[$object->id] = $object->name;
            }
            echo '<div align="center">';
            //print them in the menu
            print_group_menu($validgroups, $groupmode, $currentgroup, $urlroot,0);
            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.$CFG->siteidentifier),0,16).'@'.$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)));