mahara.php

<?php
/**
 * Mahara: Electronic portfolio, weblog, resume builder and social networking
 * Copyright (C) 2006-2009 Catalyst IT Ltd and others; see:
 *                         http://wiki.mahara.org/Contributors
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 * @package    mahara
 * @subpackage core
 * @author     Catalyst IT Ltd
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL
 * @copyright  (C) 2006-2009 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(), '5.1.3') < 0) {
        throw new ConfigSanityException(get_string('phpversion', 'error'));
    }

    // Various required extensions
    if (!extension_loaded('json')) {
        throw new ConfigSanityException(get_string('jsonextensionnotloaded', 'error'));
    }
    switch (get_config('dbtype')) {
    case 'postgres8':
        if (!extension_loaded('pgsql')) {
            throw new ConfigSanityException(get_string('pgsqldbextensionnotloaded', 'error'));
        }
        break;
    case 'mysql5':
        if (!extension_loaded('mysql')) {
            throw new ConfigSanityException(get_string('mysqldbextensionnotloaded', 'error'));
        }
        break;
    default:
        throw new ConfigSanityException(get_string('unknowndbtype', 'error'));
    }
    if (!extension_loaded('xml')) {
        throw new ConfigSanityException(get_string('xmlextensionnotloaded', 'error', 'xml'));
    }
    if (!extension_loaded('libxml')) {
        throw new ConfigSanityException(get_string('xmlextensionnotloaded', 'error', 'libxml'));
    }
    if (!extension_loaded('gd')) {
        throw new ConfigSanityException(get_string('gdextensionnotloaded', 'error'));
    }
    if (!extension_loaded('session')) {
        throw new ConfigSanityException(get_string('sessionextensionnotloaded', 'error'));
    }

    if(!extension_loaded('curl')) {
        throw new ConfigSanityException(get_string('curllibrarynotinstalled', 'error'));
    }
    if (!extension_loaded('dom')) {
        throw new ConfigSanityException(get_string('domextensionnotloaded', 'error'));
    }

    //Check for freetype in the gd extension
    $gd_info = gd_info();
    if (!$gd_info['FreeType Support']) {
        throw new ConfigSanityException(get_string('gdfreetypenotloaded', '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 (!defined('CRON') && 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') . 'sessions') ||
        !check_dir_exists(get_config('dataroot') . 'temp') ||
        !check_dir_exists(get_config('dataroot') . 'langpacks') ||
        !check_dir_exists(get_config('dataroot') . 'htmlpurifier')) {
        throw new ConfigSanityException(get_string('couldnotmakedatadirectories', 'error'));
    }

    raise_memory_limit('128M');
}

/**
 * Check sanity of things that we only check at installation time - not on 
 * every request, like ensure_sanity() does
 */
function ensure_install_sanity() {
    // Must must must be a UTF8 database!
    if (!db_is_utf8()) {
        throw new ConfigSanityException(get_string('dbnotutf8', 'error'));
    }
}

function ensure_upgrade_sanity() {
    // Check column collation is equal to the default
    if (is_mysql()) {
        require_once('ddl.php');
        if (table_exists(new XMLDBTable('event_type'))) {
            if (!column_collation_is_default('event_type', 'name')) {
                throw new ConfigSanityException(get_string('dbcollationmismatch', 'admin'));
            }
        }
    }
}

/**
 * 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_string_from_language($lang, $identifier, $section='mahara') {

    $variables = func_get_args();
    if (count($variables) > 3) { // we have some stuff we need to sprintf
        array_shift($variables);
        array_shift($variables);
        array_shift($variables); //shift off the first three.
    }
    else {
        $variables = array();
    }
    
    return get_string_location($identifier, $section, $variables, 'format_langstring', $lang);
}

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) {

    $subdir = 'help/';

    if ($page) {
        $pagebits = split('-', $page);
        $file = array_pop($pagebits) . '.html';
        if ($plugintype != 'core') {
            $subdir .= 'pages/' . join('/', $pagebits) . '/';
        }
        else {
            $subdir .= 'pages/' . $pluginname . '/' . join('/', $pagebits) . '/';
        } 
    }
    else if ($section) {
        $subdir .= 'sections/';
        $file = $section . '.html';
    }
    else if (!empty($form) && !empty($element)) {
        $subdir .= 'forms/';
        $file = $form . '.' . $element . '.html';
    }
    else if (!empty($form) && empty($element)) {
        $subdir .= 'forms/';
        $file = $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 local settings
    $langfile = get_config('docroot') . 'local/lang/' . $lang . '/' . $subdir;
    if ($plugintype != 'core') {
        $langfile .= $plugintype . '.' . $pluginname . '.' . $file;
    }
    else {
        $langfile .= $file;
    }
    if (is_readable($langfile)) {
        return $langfile;
    }

    if ($plugintype != 'core') {
        $location = $plugintype . '/' . $pluginname . '/lang/';
    }
    else {
        $location = 'lang/';
    }

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

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

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

    $langconfigstrs = array('parentlanguage', 'thislanguage');

    if ($section == 'mahara' &&
        (in_array($identifier, $langconfigstrs)
         || strpos($identifier, 'strftime') === 0
         || strpos($identifier, 'strfday')  === 0)) {
        $section = 'langconfig';
    }

    if (empty($lang)) {
        $lang = current_language();
    }

    // Define the locations of language strings for this section
    $langstringroot = get_language_root($lang);
    $langdirectory  = ''; // The directory in which the language file for this string should ideally reside, if the language has implemented it
    
    if (false === strpos($section, '.')) {
        $langdirectory = 'lang/';
    }
    else {
        $extras = plugin_types(); // more later..
        foreach ($extras as $tocheck) {
            if (strpos($section, $tocheck . '.') === 0) {
                $pluginname = substr($section ,strlen($tocheck) + 1);
                if ($tocheck == 'blocktype' && 
                    strpos($pluginname, '/') !== false) { // it belongs to an artefact plugin
                    $bits = explode('/', $pluginname);
                    $langdirectory = 'artefact/' . $bits[0] . '/blocktype/' . $bits[1] . '/lang/';
                    $section = 'blocktype.' . $bits[1];
                }
                else {
                    $langdirectory = $tocheck . '/' . $pluginname . '/lang/';
                }
            }
        }
    }

    // First check all the normal locations for the string in the current language
    if ($result = get_string_local($langstringroot . $langdirectory, $lang . '/' . $section . '.php', $identifier)) {
        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
    $langfile = $langstringroot . 'lang/' . $lang . '/langconfig.php';
    if (is_readable($langfile)) {
        if ($parentlang = get_string_from_file('parentlanguage', $langfile)) {
            if ($result = get_string_local(get_language_root($parentlang) . 'lang/', $parentlang . '/' . $section . '.php', $identifier)) {
                return $replacefunc($result, $variables);
            }
        }
    }

    /// Our only remaining option is to try English
    if ($result = get_string_local(get_config('docroot') . $langdirectory, 'en.utf8/' . $section . '.php', $identifier)) {
        return $replacefunc($result, $variables);
    }

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


/**
 * Get string from a file, checking the appropriate local customisation directory first
 *
 */
function get_string_local($langpath, $langfile, $identifier) {
    foreach (array(get_config('docroot') . 'local/lang/', $langpath) as $dir) {
        $file = $dir . $langfile;
        if (is_readable($file)) {
            if ($result = get_string_from_file($identifier, $file)) {
                return $result;
            }
        }
    }
    return false;
}


/**
 * Return a list of available languages
 *
 */
function get_languages() {
    static $langs = array();

    if (!$langs) {
        foreach (language_get_searchpaths() as $searchpath) {
            $langbase = $searchpath . 'lang/';
            if ($langdir = @opendir($langbase)) {
                while (false !== ($subdir = readdir($langdir))) {
                    if (preg_match('/\.utf8$/', $subdir) && is_dir($langbase . $subdir)) {
                        $langfile = $langbase . $subdir . '/langconfig.php';
                        if (is_readable($langfile)) {
                            if ($langname = get_string_from_file('thislanguage', $langfile)) {
                                $langs[$subdir] = $langname;
                            }
                        }
                    }
                }
                closedir($langdir);
            }
            else {
                log_warn('Unable to read language directory ' . $langbase);
            }
        }
    }

    return $langs;
}

/**
 * Returns whether the given language is installed/available for use
 */
function language_installed($lang) {
    foreach (language_get_searchpaths() as $searchpath) {
        if (is_readable($searchpath . 'lang/' . $lang . '/langconfig.php')) {
            return true;
        }
    }
    return false;
}

/**
 * Returns a list of directories in which to search for language packs.
 *
 * This is influenced by the configuration variable 'langpacksearchpaths'
 */
function language_get_searchpaths() {
    static $searchpaths = array();

    if (!$searchpaths) {
        // Construct the search path
        $docrootpath = array(get_config('docroot'));

        // Paths to language files in dataroot
        $datarootpaths = (array)glob(get_config('dataroot') . 'langpacks/*.utf8', GLOB_MARK | GLOB_ONLYDIR);

        // langpacksearchpaths configuration variable - for experts :)
        $lpsearchpaths = (array)get_config('langpacksearchpaths');
        $langpacksearchpaths = array();
        foreach ($lpsearchpaths as $path) {
            if (is_dir($path)) {
                $langpacksearchpaths[] = (substr($path, -1) == '/') ? $path : "$path/";
            }
            else {
                log_warn("Path in langpacksearchpaths is not a directory: $path");
            }
        }

        $searchpaths = array_merge($docrootpath, $datarootpaths, $langpacksearchpaths);
    }

    return $searchpaths;
}

/**
 * Get the directory in which the specified language pack resides.
 *
 * Defaults to getting the directory for the current_language() - i.e. the 
 * language the user is using
 *
 * Returns null if the language can't be found
 *
 * @param string $language The language to look for
 */
function get_language_root($language=null) {
    static $language_root_cache = array();

    if (!isset($language_root_cache[$language])) {
        if ($language == null) {
            $language = current_language();
        }

        foreach (language_get_searchpaths() as $path) {
            if (is_dir("$path/lang/$language")) {
                return $language_root_cache[$language] = $path;
            }
        }

        // Oh noes, can't be found
        $language_root_cache[$language] = null;

    }

    return $language_root_cache[$language];
}

/**
 * Return a list of all available themes.
 * @return array subdir => name
 */
function get_all_themes() {
    static $themes = null;

    if (is_null($themes)) {
        $themes = array();
        $themelist = get_all_theme_objects();
        foreach ($themelist AS $subdir => $theme) {
            $themes[$subdir] = isset($theme->displayname) ? $theme->displayname : $subdir;
        }
    }

    return $themes;
}

/**
 * Return a list of themes available to this user
 * If the user is a member of any institutions, only themes available to
 * those institutions are returned; or
 * If a user is not a member of any institution, all themes not marked as
 * institution specific are returned.
 * @return array subdir => name
 */
function get_user_accessible_themes() {
    global $USER;

    $themes = array();
    if ($institutions = $USER->get('institutions')) {
        // Get themes for all of this users institutions
        foreach ($institutions AS $i) {
            $themes = array_merge($themes, get_institution_themes($i->institution));
        }
    }
    else {
        $themelist = get_all_theme_objects();
        foreach ($themelist AS $subdir => $theme) {
            if (!isset($theme->institutions) || !is_array($theme->institutions)) {
                $themes[$subdir] = isset($theme->displayname) ? $theme->displayname : $subdir;
            }
        }

    }
    return $themes;
}

/**
 * Return a list of themes available to the specified institution
 * @param string institution the name of the institution to load themes for
 * @return array subdir => name
 * @throws SystemException if unable to read the theme directory
 */
function get_institution_themes($institution) {
    static $institutionthemes = array();
    if (!isset($institutionthemes[$institution])) {
        $themes = get_all_theme_objects();
        $r = array();
        foreach ($themes AS $subdir => $theme) {
            if (empty($theme->institutions) || !is_array($theme->institutions) || in_array($institution, $theme->institutions)) {
                $r[$subdir] = isset($theme->displayname) ? $theme->displayname : $subdir;
            }
        }
        $institutionthemes[$institution] = $r;
    }

    return $institutionthemes[$institution];
}

/**
 * Return a list of all themes available on the system
 * @return array An array of theme objects
 * @throws SystemException if unable to read the theme directory
 */
function get_all_theme_objects() {
    static $themes = null;

    if (is_null($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)) {
                $config_path = $themebase . $subdir . '/themeconfig.php';
                if (is_readable($config_path)) {
                    require($config_path);
                    if (empty($theme->disabled) || !$theme->disabled) {
                        $themes[$subdir] = $theme;
                    }
                }
            }
        }
        closedir($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;
    
    $dbconfig = get_records_array('config', '', '', '', 'field, value');
    
    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 $CFG;
    if (isset($CFG->$key)) {
        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;

    db_ignore_sql_exceptions(true);
    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);
    }
    db_ignore_sql_exceptions(false);

    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, $SESSION;
    if ($USER instanceof User) {
        $lang = $USER->get_account_preference('lang');
        if ($lang !== null && $lang != 'default') {
            if (language_installed($lang)) {
                return $lang;
            }
            $USER->set_account_preference('lang', 'default');
        }
    }

    if (is_a($SESSION, 'Session')) {
        $sesslang = $SESSION->get('lang');
        if (!empty($sesslang) && $sesslang != 'default') {
            return $sesslang;
        }
    }

    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 {
            $mask = umask(0000);
            $status = @mkdir($dir, get_config('directorypermissions'), true);
            umask($mask);
        }
    }
    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 :)
 *
 * blocktypes are special cases.  eg:
 *   system blocks: safe_require('blocktype', 'wall');
 *   artefact blocks: safe_require('blocktype', 'file/html');
 *
 * import/export plugins are special cases.  eg:
 *   main library: safe_require('export', 'leap');
 *   artefact plugin implementation: safe_require('export', 'leap/file');
 *
 * @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] . '/' . $filename;
        }
        else {
            try {
                if ($artefactplugin = get_field('blocktype_installed', 'artefactplugin', 'name', $pluginname)) {
                    $fullpath = get_config('docroot') . 'artefact/' . $artefactplugin . '/blocktype/' . $pluginname . '/'. $filename;
                }
            }
            catch (SQLException $e) {
                if (get_config('installed')) {
                    throw $e;
                }
            }
        }
    }
    // these can have parts living inside artefact directories as well.
    else if ($plugintype == 'export' || $plugintype == 'import') {
        $bits = explode('/', $pluginname);
        if (count($bits) == 2) {
            $fullpath = get_config('docroot') . 'artefact/' . $bits[1] . '/' . $plugintype . '/' . $bits[0] . '/' . $filename;
        }
    }
    if (empty($fullpath)) {
        $fullpath = get_config('docroot') . $plugintype . '/' . $pluginname . '/' . $filename;
    }

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

    if (strpos($realpath, get_config('docroot') !== 0)) {
        if (!empty($nonfatal)) {
            return false;
        }
        throw new SystemException ("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.
 *
 * NOTE: use plugin_types_installed if you just want the installed ones.
 *
 * @return array of names
 */
function plugin_types() {
    static $pluginstocheck;
    if (empty($pluginstocheck)) {
        // ORDER MATTERS! artefact has to be first!
        $pluginstocheck = array('artefact', 'auth', 'notification', 'search', 'blocktype', 'interaction', 'grouptype', 'import', 'export');
    }
    return $pluginstocheck;
}

/**
 * Returns plugin types that are actually installed
 */
function plugin_types_installed() {
    static $plugins = array();
    if (empty($plugins)) {
        require_once('ddl.php');
        foreach (plugin_types() as $plugin) {
            if (table_exists(new XMLDBTable("{$plugin}_installed"))) {
                $plugins[] = $plugin;
            }
        }
    }
    return $plugins;
}

/** 
 * This return returns the names of plugins installed 
 * for the given plugin type.
 * 
 * @param string $plugintype type of plugin
 */
function plugins_installed($plugintype, $all=false) {
    $sort = 'name';
    if ($plugintype == 'blocktype') {
        $sort = 'artefactplugin,name';
    }
    if ($all) {
        return get_records_array($plugintype . '_installed', '', '', $sort);
    }
    return get_records_array($plugintype . '_installed', 'active', 1, $sort);
}

/**
 * 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() {
    $args = func_get_args();
    if (count($args) == 2 && $args[0] == 'blocktype') {
        return 'PluginBlocktype' . ucfirst(blocktype_namespaced_to_single($args[1]));
    }
    return 'Plugin' . implode('', array_map('ucfirst', $args));
}

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

function generate_interaction_instance_class_name($type) {
    return 'Interaction' . ucfirst($type) . 'Instance';
}

function blocktype_namespaced_to_single($blocktype) {
    if (strpos($blocktype, '/') === false) { // system blocktype
        return $blocktype;
    }
    return substr($blocktype, strpos($blocktype, '/') + 1 );
}

function blocktype_single_to_namespaced($blocktype, $artefact='') {
    if (empty($artefact)) {
        return $blocktype;
    }
    return $artefact . '/' . $blocktype;
}

/**
 * Given a blocktype name, convert it to the namespaced version.
 *
 * This will be $artefacttype/$blocktype, or just plain $blocktype for system 
 * blocktypes.
 *
 * This is useful for language strings
 */
function blocktype_name_to_namespaced($blocktype) {
    static $resultcache = array();

    if (!isset($resultcache[$blocktype])) {
        $artefactplugin = get_field('blocktype_installed', 'artefactplugin', 'name', $blocktype);
        if ($artefactplugin) {
            $resultcache[$blocktype] = "$artefactplugin/$blocktype";
        }
        else {
            $resultcache[$blocktype] = $blocktype;
        }
    }

    return $resultcache[$blocktype];
}


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

    if ($coreevents = get_records_array('event_subscription', 'event', $event)) {
        require_once('activity.php'); // core events can generate activity.
        foreach ($coreevents as $ce) {
            if (function_exists($ce->callfunction)) {
                call_user_func($ce->callfunction, $data);
            }
            else {
                log_warn("Event $event caused a problem with a core subscription "
                . " $ce->callfunction, which wasn't callable.  Continuing with event handlers");
            }
        }
    }

    $plugintypes = plugin_types_installed();
    foreach ($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) {