mahara.php

<?php
/**
 * This program is part of Mahara
 *
 *  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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * @package    mahara
 * @subpackage core
 * @author     Penny Leach <penny@catalyst.net.nz>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL
 * @copyright  (C) 2006,2007 Catalyst IT Ltd http://catalyst.net.nz
 * @copyright  (C) portions from Moodle, (C) Martin Dougiamas http://dougiamas.com
 */

defined('INTERNAL') || die();

/** 
 * work around silly php settings
 * and broken setup stuff about the install
 * and raise a warning/fail depending on severity
 */
function ensure_sanity() {

    // PHP version
    if (version_compare(phpversion(), '5.1.0') < 0) {
        throw new ConfigSanityException(get_string('phpversion', 'error'));
    }

    // Various required extensions
    if (!extension_loaded('json')) {
        throw new ConfigSanityException(get_string('jsonextensionnotloaded', 'error'));
    }
    if (!extension_loaded('pgsql') && !extension_loaded('mysqli')) {
        throw new ConfigSanityException(get_string('dbextensionnotloaded', 'error'));
    }
    if (!extension_loaded('libxml')) {
        throw new ConfigSanityException(get_string('libxmlextensionnotloaded', 'error'));
    }
    if (!extension_loaded('gd')) {
        throw new ConfigSanityException(get_string('gdextensionnotloaded', 'error'));
    }
    if (!extension_loaded('session')) {
        throw new ConfigSanityException(get_string('sessionextensionnotloaded', 'error'));
    }

    // Various optional extensions
    if (!extension_loaded('openssl')) {
        log_environ(get_string('opensslextensionnotloaded', 'error'));
    }
    if (!extension_loaded('curl')) {
        log_environ(get_string('curlextensionnotloaded', 'error'));
    }
    if (!extension_loaded('xmlrpc')) {
        log_environ(get_string('xmlrpcextensionnotloaded', 'error'));
    }

    // register globals workaround
    if (ini_get_bool('register_globals')) {
        log_environ(get_string('registerglobals', 'error'));
        $massivearray = array_keys(array_merge($_POST, $_GET, $_COOKIE, $_SERVER, $_REQUEST, $_FILES));
        foreach ($massivearray as $tounset) {
            unset($GLOBALS[$tounset]);
        }
    }

    // magic_quotes_gpc workaround
    if (ini_get_bool('magic_quotes_gpc')) {
        log_environ(get_string('magicquotesgpc', 'error'));
        function stripslashes_deep($value) {
            $value = is_array($value) ?
                array_map('stripslashes_deep', $value) :
                stripslashes($value);
            return $value;
        }
        $_POST = array_map('stripslashes_deep', $_POST);
        $_GET = array_map('stripslashes_deep', $_GET);
        $_COOKIE = array_map('stripslashes_deep', $_COOKIE);
        $_REQUEST = array_map('stripslashes_deep', $_REQUEST);

        $servervars = array('REQUEST_URI','QUERY_STRING','HTTP_REFERER','PATH_INFO','PHP_SELF','PATH_TRANSLATED');
        foreach ($servervars as $tocheck) {
            if (array_key_exists($tocheck,$_SERVER) && !empty($_SERVER[$tocheck])) {
                $_SERVER[$tocheck] = stripslashes($_SERVER[$tocheck]);
            }
        }
    }

    if (ini_get_bool('magic_quotes_runtime')) {
        // Turn of magic_quotes_runtime. Anyone with this on deserves a slap in the face
        set_magic_quotes_runtime(0);
        log_environ(get_string('magicquotesruntime', 'error'));
    }

    if (ini_get_bool('magic_quotes_sybase')) {
        // See above comment re. magic_quotes_runtime
        @ini_set('magic_quotes_sybase', 0);
        log_environ(get_string('magicquotessybase', 'error'));
    }

    if (ini_get_bool('safe_mode')) {
        // We don't run with safe mode
        throw new ConfigSanityException(get_string('safemodeon', 'error'));
    }

    // Other things that might be worth checking:
    //    memory limit
    //    file_uploads (off|on)
    //    upload_max_filesize
    //    allow_url_fopen (only if we use this)
    //

    // dataroot inside document root.
    if (strpos(get_config('dataroot'), get_config('docroot')) !== false) {
        throw new ConfigSanityException(get_string('datarootinsidedocroot', 'error'));
    }

    // dataroot not writable..
    if (!check_dir_exists(get_config('dataroot')) || !is_writable(get_config('dataroot'))) {
        throw new ConfigSanityException(get_string('datarootnotwritable', 'error', get_config('dataroot')));
    }

    if (
        !check_dir_exists(get_config('dataroot') . 'smarty/compile') ||
        !check_dir_exists(get_config('dataroot') . 'smarty/cache') ||
        !check_dir_exists(get_config('dataroot') . 'templates') ||
        !check_dir_exists(get_config('dataroot') . 'sessions')) {
        throw new ConfigSanityException(get_string('couldnotmakedatadirectories', 'error'));
    }
}

/**
 * Check to see if the internal plugins are installed. Die if they are not.
 */
function ensure_internal_plugins_exist() {
    // Internal things installed
    if (get_config('installed')) {
        foreach (plugin_types() as $type) {
            if (!record_exists($type . '_installed', 'name', 'internal')) {
                throw new ConfigSanityException(get_string($type . 'notinstalled'));
            }
        }
    }
}

function get_string($identifier, $section='mahara') {

    $variables = func_get_args();
    if (count($variables) > 2) { // we have some stuff we need to sprintf
        array_shift($variables);
        array_shift($variables); //shift off the first two.
    }
    else {
        $variables = array();
    }
    
    return get_string_location($identifier, $section, $variables);
}

function get_helpfile($plugintype, $pluginname, $form, $element, $page=null, $section=null) {
    if ($langfile = get_helpfile_location($plugintype, $pluginname, $form, $element, $page, $section)) {
        return file_get_contents($langfile);
    }
    return false;
}

function get_helpfile_location($plugintype, $pluginname, $form, $element, $page=null, $section=null) {

    $location = get_config('docroot') ;
    $file = 'help/';

    if ($plugintype != 'core') {
        $location .= $plugintype . '/' . $pluginname . '/lang/';
    }
    else {
        $location .= 'lang/';
    }
    if ($page) {
        $page = str_replace('-', '/', $page);
        if ($plugintype != 'core') {
            $file .=  'pages/' . $page . '.html';
        }
        else {
            $file .= 'pages/' . $pluginname . '/' . $page . '.html';
        } 
    }
    else if ($section) {
        $file .= 'sections/' . $section . '.html';
    }
    else if (!empty($form) && !empty($element)) {
        $file .= 'forms/' . $form . '.' . $element . '.html';
    }
    else if (!empty($form) && empty($element)) {
        $file .= 'forms/' . $form . '.html';
    }
    else {
        return false;
    }

    // now we have to try and locate the help file
    $lang = current_language();
    if ($lang == 'en.utf8') {
        $trieden = true;
    }
    else {
        $trieden = false;
    }

    // try the current language
    $langfile = $location . $lang . '/' . $file;
    if (is_readable($langfile)) {
        return $langfile;
    }

    // if it's not found, try the parent language if there is one...
    if (empty($data) && empty($trieden)) {
        $langfile = $location . $lang . '/langconfig.php';
        if ($parentlang = get_string_from_file('parentlanguage', $langfile)) {
            if ($parentlang == 'en.utf8') {
                $trieden = true;
            }
            $langfile = $location . $parentlang . '/' . $file;
            if (is_readable($langfile)) {
                return $langfile;
            }
        }
    }

    // if it's STILL not found, and we haven't already tried english ...
    if (empty($data) && empty($trieden)) {
        $langfile = $location .  'en.utf8/' . $file;
        if (is_readable($langfile)) {
            return $langfile;
        }
    }
    return false;
}

// get a string without sprintfing it.
function get_raw_string($identifier, $section='mahara') {
    // For a raw string we don't want to format any arguments using
    // sprintf, so the replace function passed to get_string_location
    // should just return the first argument and ignore the second.
    return get_string_location($identifier, $section, array(), 
                               create_function('$string, $args','return $string;'));
}


/**
 * This function gets a language string identified by $identifier from
 * an appropriate location, and formats the string and any arguments
 * in $variables using the function $replacefunc.
 *
 * @param string   $identifier
 * @param string   $section
 * @param array    $variables
 * @param function $replacefunc
 * @return string
 */
function get_string_location($identifier, $section, $variables, $replacefunc='format_langstring') {

    $langconfigstrs = array('parentlanguage', 'strftimedate', 'strftimedateshort', 'strftimedatetime',
                            'strftimedaydate', 'strftimedaydatetime', 'strftimedayshort', 'strftimedaytime',
                            'strftimemonthyear', 'strftimerecent', 'strftimerecentfull', 'strftimetime',
                            'strfdaymonthyearshort', 'thislanguage');

    if (in_array($identifier, $langconfigstrs)) {
        $section = 'langconfig';
    }

    $lang = current_language();

    // Define the locations of language strings for this section
    $docroot = get_config('docroot');
    $locations = array();
    
    if (false === strpos($section, '.')) {
        $locations[] = $docroot . 'lang/';
    }
    else {
        $extras = plugin_types(); // more later..
        foreach ($extras as $tocheck) {
            if (strpos($section,$tocheck . '.') === 0) {
                $pluginname = substr($section ,strlen($tocheck) + 1);
                $locations[] = $docroot . $tocheck . '/' . $pluginname . '/lang/';
            }
        }
    }

    // First check all the normal locations for the string in the current language
    foreach ($locations as $location) {
        //if local directory not found, or particular string does not exist in local direcotry
        $langfile = $location . $lang . '/' . $section . '.php';
        if (is_readable($langfile)) {
            if ($result = get_string_from_file($identifier, $langfile)) {
                return $replacefunc($result, $variables);
            }
        }
    }

    // If the preferred language was English (utf8) we can abort now
    // saving some checks beacuse it's the only "root" lang
    if ($lang == 'en.utf8') {
        return '[[' . $identifier . '/' . $section . ']]';
    }

    // Is a parent language defined?  If so, try to find this string in a parent language file
    foreach ($locations as $location) {
        $langfile = $location . $lang . '/langconfig.php';
        if (is_readable($langfile)) {
            if ($parentlang = get_string_from_file('parentlanguage', $langfile)) {
                $langfile = $location . $parentlang . '/' . $section . '.php';
                if (is_readable($langfile)) {
                    if ($result = get_string_from_file($identifier, $langfile)) {
                        return $replacefunc($result, $variables);
                    }
                }
            }
        }
    }

    /// Our only remaining option is to try English
    foreach ($locations as $location) {
        //if local_en not found, or string not found in local_en
        $langfile = $location . 'en.utf8/' . $section . '.php';
        if (is_readable($langfile)) {
            if ($result = get_string_from_file($identifier, $langfile)) {
                return $replacefunc($result, $variables);
            }
        }
    }

    return '[[' . $identifier . '/' . $section . ']]';  // Last resort
}


/**
 * Return a list of available languages
 *
 */
function get_languages() {
    $langs = array();
    $langbase = get_config('docroot') . 'lang/';
    if (!$langdir = opendir($langbase)) {
        throw new SystemException('Unable to read language directory '.$langbase);
    }
    while (false !== ($subdir = readdir($langdir))) {
        $langfile = $langbase . $subdir . '/langconfig.php';
        if ($subdir != "." && $subdir != ".." && is_readable($langfile)) {
            if ($langname = get_string_from_file('thislanguage',$langfile)) {
                $langs[$subdir] = $langname;
            }
        }
    }
    closedir($langdir);
    return $langs;
}

/**
 * Return a list of available themes
 * Need to add the theme names sometime; for now use get_string().
 *
 */
function get_themes() {
    $themes = array();
    $themebase = get_config('docroot') . 'theme/';
    if (!$themedir = opendir($themebase)) {
        throw new SystemException('Unable to read theme directory '.$themebase);
    }
    while (false !== ($subdir = readdir($themedir))) {
        if ($subdir != "." && $subdir != ".." && is_dir($themebase . $subdir)) {
            $themes[$subdir] = $subdir;

            $config_path = $themebase . $subdir . '/config.php';
            if (is_readable($config_path)) {
                require_once($config_path);
                if (isset($theme->name)) {
                    $themes[$subdir] = $theme->name;
                }
            }
        }
    }
    closedir($themedir);
    return $themes;
}


/**
 * This function is only used from {@link get_string()}.
 *
 * @internal Only used from get_string, not meant to be public API
 * @param string $identifier ?
 * @param string $langfile ?
 * @param string $destination ?
 * @return string|false ?
 * @staticvar array $strings Localized strings
 * @access private
 * @todo Finish documenting this function.
 */
function get_string_from_file($identifier, $langfile) {

    static $strings;    // Keep the strings cached in memory.

    if (empty($strings[$langfile])) {
        $string = array();
        include ($langfile);
        $strings[$langfile] = $string;
    } else {
        $string = &$strings[$langfile];
    }

    if (!isset ($string[$identifier])) {
        return false;
    }

    return $string[$identifier];
}

/**
 * This function makes the return value of ini_get consistent if you are
 * setting server directives through the .htaccess file in apache.
 * Current behavior for value set from php.ini On = 1, Off = [blank]
 * Current behavior for value set from .htaccess On = On, Off = Off
 * Contributed by jdell @ unr.edu
 *
 * @param string $ini_get_arg setting to look for
 * @return bool
 */
function ini_get_bool($ini_get_arg) {
    $temp = ini_get($ini_get_arg);

    if ($temp == '1' or strtolower($temp) == 'on') {
        return true;
    }
    return false;
}

/**
 * This function loads up the basic $CFG
 * from the database table
 * note that it doesn't load plugin config
 * as not every page needs them
 * @return boolean false if the assignment fails (generally if the databse is not installed)
 */
function load_config() {
    global $CFG;
    
    try {
        $dbconfig = get_records_array('config', '', '', '', 'field, value');
    } 
    catch (SQLException $e) {
        // TODO: better reporting if config could not be obtained? This 
        // normally happens when the system isn't installed
        log_info($e->getMessage());
        return false;
    }
    
    foreach ($dbconfig as $cfg) {
        if (isset($CFG->{$cfg->field}) && $CFG->{$cfg->field} != $cfg->value) {
            // @todo warn that we're overriding db config with $CFG
            continue;
        }
        $CFG->{$cfg->field} = $cfg->value;
    }

    return true;
}

/**
 * This function returns a value from $CFG
 * or null if it is not found
 * 
 * @param string $key config setting to look for 
 * @return mixed
 */
function get_config($key) {
    global $CFG;
    if (array_key_exists($key,$CFG)) {
        return $CFG->$key;
    }
    return null;
}


/**
 * This function sets a config variable
 * both in $CFG and in the database
 *
 * @param string $key config field to set
 * @param string $value config value
 */
function set_config($key, $value) {
    global $CFG;

    if (get_record('config', 'field', $key)) {
        if (set_field('config', 'value', $value, 'field', $key)) {
            $status = true;
        }
    } 
    else {
        $config = new StdClass;
        $config->field = $key;
        $config->value = $value;
        $status = insert_record('config', $config);
    }

    if (!empty($status)) {
        $CFG->{$key} = $value;
        return true;
    }

    return false;
}

/**
 * This function returns a value for $CFG for a plugin
 * or null if it is not found
 * note that it may go and look in the database
 *
 * @param string $plugintype eg artefact
 * @param string $pluginname eg blog
 * @param string $key the config setting to look for
 */
function get_config_plugin($plugintype, $pluginname, $key) {
    global $CFG;

    // Suppress NOTICE with @ in case $key is not yet cached
    @$value = $CFG->plugin->{$plugintype}->{$pluginname}->{$key};
    if (isset($value)) {
        return $value;
    }

    $records = get_records_array($plugintype . '_config', 'plugin', $pluginname, 'field', 'field, value');
    if (!empty($records)) {
        foreach($records as $record) {
            $CFG->plugin->{$plugintype}->{$pluginname}->{$record->field} = $record->value;
            if ($record->field == $key) {
                $value = $record->value;
            }
        }
    }

    return $value;
}

function set_config_plugin($plugintype, $pluginname, $key, $value) {
    global $CFG;
    $table = $plugintype . '_config';

    if (false !== get_field($table, 'value', 'plugin', $pluginname, 'field', $key)) {
        //if (set_field($table, 'value', $key, 'plugin', $pluginname, 'field', $value)) {
        if (set_field($table, 'value', $value, 'plugin', $pluginname, 'field', $key)) {
            $status = true;
        }
    }
    else {
        $pconfig = new StdClass;
        $pconfig->plugin = $pluginname;
        $pconfig->field  = $key;
        $pconfig->value  = $value;
        $status = insert_record($table, $pconfig);
    }
    if ($status) {
        $CFG->plugin->{$plugintype}->{$pluginname}->{$key} = $value;
        return true;
    }
    return false;
}

/**
 * This function returns a value for $CFG for a plugin instance
 * or null if it is not found. Initially this is interesting only 
 * for multiauth. Note that it may go and look in the database
 *
 * @param string $plugintype   E.g. auth
 * @param string $pluginname   E.g. internal
 * @param string $pluginid     Instance id
 * @param string $key          The config setting to look for
 */
function get_config_plugin_instance($plugintype, $pluginid, $key) {
    global $CFG;

    // Must be unlikely to exist as a config option for any plugin
    $instance = '_i_n_s_t'.$pluginid;

    // Suppress NOTICE with @ in case $key is not yet cached
    @$value = $CFG->plugin->{$plugintype}->{$instance}->{$key};
    if (isset($value)) {
        return $value;
    }

    $records = get_records_array($plugintype . '_instance_config', 'instance', $pluginid, 'field', 'field, value');
    if (!empty($records)) {
        foreach($records as $record) {
            $CFG->plugin->{$plugintype}->{$instance}->{$record->field} = $record->value;
            if ($record->field == $key) {
                $value = $record->value;
            }
        }
    }

    return $value;
}

/**
 * This function returns a value for $CFG for a plugin instance
 * or null if it is not found. Initially this is interesting only 
 * for multiauth. Note that it may go and look in the database
 *
 * @param string $plugintype   E.g. auth
 * @param string $pluginname   E.g. internal
 * @param string $pluginid     Instance id
 * @param string $key          The config setting to look for
 */
function set_config_plugin_instance($plugintype, $pluginname, $pluginid, $key, $value) {
    global $CFG;
    $table = $plugintype . '_instance_config';

    if (false !== get_field($table, 'value', 'instance', $pluginid, 'field', $key)) {
        if (set_field($table, 'value', $value, 'instance', $pluginid, 'field', $key)) {
            $status = true;
        }
    }
    else {
        $pconfig = new StdClass;
        $pconfig->instance = $pluginid;
        $pconfig->field  = $key;
        $pconfig->value  = $value;
        $status = insert_record($table, $pconfig);
    }
    if ($status) {
        // Must be unlikely to exist as a config option for any plugin
        $instance = '_i_n_s_t'.$pluginid;
        $CFG->plugin->{$plugintype}->{$pluginname}->{$instance}->{$key} = $value;
        return true;
    }
    return false;
}

/**
 * This function prints an array or object
 * wrapped inside <pre></pre>
 * 
 * @param $mixed value to print
 */
function print_object($mixed) {
    echo '<pre>';
    print_r($mixed);
    echo '</pre>';
}

/**
 * This function returns the current 
 * language to use, either for a given user
 * or sitewide, or the default
 * 
 * @return string
 */
function current_language() {
    global $USER, $CFG;
    if ($USER instanceof User) {
        $lang = $USER->get_account_preference('lang');
        if ($lang !== null && $lang != 'default') {
            return $lang;
        }
    }
    if (!empty($CFG->lang)) {
        return $CFG->lang;
    }
    return 'en.utf8';
}

/**
 * Helper function to sprintf language strings
 * with a variable number of arguments
 * 
 * @param string $string raw string to use
 * @param array $args arguments to sprintf
 */
function format_langstring($string,$args) {
    return call_user_func_array('sprintf',array_merge(array($string),$args));
}

/**
 * Helper function to figure out whether an array is an array or a hash
 * @param array $array array to check
 * @return bool true if the array is a hash
 */
function is_hash($array) {
    if (!is_array($array)) {
        return false;
    }
    $diff = array_diff_assoc($array,array_values($array));
    return !empty($diff);
}

/**
 * Function to check if a directory exists and optionally create it.
 *
 * @param string absolute directory path
 * @param boolean create directory if does not exist
 * @param boolean create directory recursively
 *
 * @return boolean true if directory exists or created
 */
function check_dir_exists($dir, $create=true, $recursive=true) {

    $status = true;

    if(!is_dir($dir)) {
        if (!$create) {
            $status = false;
        } else {
            umask(0000); 
            $status = @mkdir($dir, 0777, true);
            // @todo has the umask been clobbered at this point, and is this a bad thing?
        }
    }
    return $status;
}

/**
 * Function to require a plugin file. This is to avoid doing 
 * require and include directly with variables.
 *
 * This function is the one safe point to require plugin files.
 * so USE it :)
 *
 * @param string $plugintype the type of plugin (eg artefact)
 * @param string $pluginname the name of the plugin (eg blog)
 * @param string $filename the name of the file to include within the plugin structure
 * @param string $function (optional, defaults to require) the require/include function to use
 * @param string $nonfatal (optional, defaults to false) just returns false if the file doesn't exist
 */
function safe_require($plugintype, $pluginname, $filename='lib.php', $function='require_once', $nonfatal=false) {
    $plugintypes = plugin_types();
    if (!in_array($plugintype, $plugintypes)) {
        throw new Exception("\"$plugintype\" is not a valid plugin type");
    }
    require_once(get_config('docroot') . $plugintype . '/lib.php');

    if (!in_array($function,array('require', 'include', 'require_once', 'include_once'))) {
        if (!empty($nonfatal)) {
            return false;
        }
        throw new Exception ('invalid require type');
    }

    if ($plugintype == 'blocktype') { // these are a bit of a special case
        $bits = explode('/', $pluginname);
        if (count($bits) == 2) {
           $fullpath = get_config('docroot') . 'artefact/' . $bits[0] . '/blocktype/' . $bits[1] . '/' . $filename;
        }
    } 
    if (empty($fullpath)) {
        $fullpath = get_config('docroot') . $plugintype . '/' . $pluginname . '/' . $filename;
    }

    if (!$realpath = realpath($fullpath)) {
        if (!empty($nonfatal)) {
            return false;
        }
        throw new Exception ("File $fullpath did not exist");
    }

    if (strpos($realpath, get_config('docroot') !== 0)) {
        if (!empty($nonfatal)) {
            return false;
        }
        throw new Exception ("File $fullpath was outside document root!");
    }

    if ($function == 'require') { return require($realpath); }
    if ($function == 'include') { return include($realpath); }
    if ($function == 'require_once') { return require_once($realpath); }
    if ($function == 'include_once') { return include_once($realpath); }
    
}

/**
 * This function returns the list of plugintypes we currently care about
 * @return array of names
 */
function plugin_types() {
    static $pluginstocheck;
    if (empty($pluginstocheck)) {
        $pluginstocheck = array('artefact', 'auth', 'notification', 'search', 'blocktype');
    }
    return $pluginstocheck;
}

/** 
 * This return returns the names of plugins installed 
 * for the given plugin type.
 * 
 * @param string $plugintype type of plugin
 */
function plugins_installed($plugintype) {
    return get_records_array($plugintype . '_installed');
}

/**
 * Helper to call a static method when you do not know the name of the class
 * you want to call the method on. PHP5 does not support $class::method().
 */
function call_static_method($class, $method) {
    $args = func_get_args();
    array_shift($args);
    array_shift($args);
    return call_user_func_array(array($class, $method), $args);
}

function generate_class_name() {
    $args = func_get_args();
    return 'Plugin' . implode('', array_map('ucfirst', $args));
}

function generate_artefact_class_name($type) {
    return 'ArtefactType' . ucfirst($type);
}

function generate_blocktype_class_name($type) {
    return 'BlockType' . ucfirst($type);
}

/**
 * Fires an event which can be handled by different parts of the system
 */
function handle_event($event, $data) {
    if (!$e = get_record('event_type', 'name', $event)) {
        throw new Exception("Invalid event");
    }

    if ($data instanceof ArtefactType) {
        // leave it alone
    }
    else if (is_object($data)) {
        $data = (array)$data;
    }
    else if (is_numeric($data)) {
        $data = array('id' => $data);
    }

    // this is here because the core can't listen to events
    // @todo, this is VERY ugly, and someone should fix it
    if ($event == 'createuser') {
        activity_set_defaults($data['id']);
    }

    $plugintypes = plugin_types();
    foreach ($plugintypes as $name) {
        if ($subs = get_records_array($name . '_event_subscription', 'event', $event)) {
            foreach ($subs as $sub) {
                safe_require($name, $sub->plugin);
                $classname = 'Plugin' . ucfirst($name) . ucfirst($sub->plugin);
                try {
                    call_static_method($classname, $sub->callfunction, $event, $data);
                }
                catch (Exception $e) {
                    log_warn("Event $event caused an exception from plugin $classname "
                             . "with function $sub->callfunction. Continuing with event handlers");
                }
            }
        }
    }
}

/**
 * function to convert an array of objects to 
 * an array containing one field per place
 * 
 * @param array $array input array
 * @param mixed $field field to look for in each object
 */
function mixed_array_to_field_array($array, $field) {
    $repl_fun = create_function('$n, $field', '$n = (object)$n; return $n->{$field};');
    $fields = array_pad(array(), count($array), $field);
    return array_map($repl_fun, $array, $fields);
}


/** 
 * Adds stuff to the log
 * @todo write this function
 *
 * @param string $plugintype plugin type or core
 * @param string $pluginname plugin name or core component (eg 'view')
 * @param string $action action string (like 'add')
 * @param int $user id of user making the action
 * @param int $id relevant id (ie, profile view would have id of profile owner)
 * 
 */
function add_to_log($plugintype, $pluginname, $action, $user, $id=0) {

}

/**
 * Used by XMLDB
 */
function debugging ($message, $level) {
    log_debug($message);
}
function xmldb_dbg($message) {
    log_warn($message);
}
define('DEBUG_DEVELOPER', 'whocares');

/** 
 * Base class for all plugintypes.
 */
class Plugin {
    
    /**
     * This function returns an array of crons it wants to have run
     * Each item should be a StdClass object containing - 
     * - callfunction (static function on the Plugin Class)
     * - any or all of minute, hour, day, month, dayofweek 
     * (will default to * if not supplied)
     */
    public static function get_cron() {
        return array();
    }

    /** 
     * This function returns an array of events to subscribe to
     * by unique name. 
     * If an event the plugin is trying to subscribe to is unknown by the
     * core, an exception will be thrown.
     * @return array
     */
    public static function get_event_subscriptions() {
        return array();
    }


    /**
     * This function will be run after every upgrade to the plugin.
     * 
     * @param int $fromversion version upgrading from (or 0 if installing)
     */
    public static function postinst($fromversion) {
        return true;
    }

    /**
     * Whether this plugin has admin plugin config options.
     * If you return true here, you must supply a valid pieform
     * in {@link get_config}
     */
    public static function has_config() {
        return false;
    }
}

/**
 * formats a unix timestamp to a nice date format.
 * 
 * @param int $date unix timestamp to format
 * @param string $formatkey language key to fetch the format from
 * @param string $notspecifiedkey (optional) language key to fetch 'not specified string' from
 * @param string $notspecifiedsection (optional) language section to fetch 'not specified string' from
 * (see langconfig.php or the top of {@link get_string_location}
 * for supported keys
 */

function format_date($date, $formatkey='strftimedatetime', $notspecifiedkey='strftimenotspecified', $notspecifiedsection='mahara') {
    if (empty($date)) {
        return get_string($notspecifiedkey, $notspecifiedsection);
    }
    return strftime(get_string($formatkey), $date);
}

/**
 * Returns a random string suitable for registration/change password requests
 *
 * @param int $length The length of the key to return
 * @return string
 */
function get_random_key($length=16) {
    if ($length < 1) {
        throw new IllegalArgumentException('Length must be a positive number');
    }
    $pool = array_merge(
        range('A', 'Z'),
        range('a', 'z'),
        range(0, 9)
    );
    shuffle($pool);
    $result = '';