<?php
/**
* Base class for course query backends
*/
abstract class CourseBackend
{
/*
* Static part for handling interfaces
*/
/**
* @var array list of known backends
*/
private static $backendTypes = false;
/**
* @var boolean|string false = no error, error message otherwise
*/
protected $error;
/**
* @var int as internal serverId
*/
protected $serverId;
/**
* @var string url of the service
*/
protected $location;
/**
* @const int max number of additional locations to fetch (for backends that benefit from request coalesc.)
*/
const MAX_ADDIDIONAL_LOCATIONS = 5;
/**
* CourseBackend constructor.
*/
public final function __construct()
{
$this->location = "";
$this->error = false;
}
/**
* Load all known backend types. This is done
* by including *.inc.php from inc/coursebackend/.
*/
public static function loadDb()
{
if (self::$backendTypes !== false)
return;
self::$backendTypes = array();
foreach (glob(dirname(__FILE__) . '/coursebackend/coursebackend_*.inc.php', GLOB_NOSORT) as $file) {
require_once $file;
preg_match('#coursebackend_([^/\.]+)\.inc\.php$#i', $file, $out);
if (!class_exists('coursebackend_' . $out[1])) {
trigger_error("Backend type source unit $file doesn't seem to define class CourseBackend_{$out[1]}", E_USER_ERROR);
}
self::$backendTypes[$out[1]] = true;
}
}
/**
* Get all known config module types.
*
* @return array list of modules
*/
public static function getList()
{
self::loadDb();
return array_keys(self::$backendTypes);
}
/**
* Get fresh instance of ConfigModule subclass for given module type.
*
* @param string $moduleType name of module type
* @return \CourseBackend module instance
*/
public static function getInstance($moduleType)
{
self::loadDb();
if (!isset(self::$backendTypes[$moduleType])) {
error_log('Unknown module type: ' . $moduleType);
return false;
}
if (!is_object(self::$backendTypes[$moduleType])) {
$class = "coursebackend_$moduleType";
self::$backendTypes[$moduleType] = new $class;
}
return self::$backendTypes[$moduleType];
}
/**
* @return string return display name of backend
*/
public abstract function getDisplayName();
/**
* @returns array with parameter name as key and and an array with type, help text and mask as value
*/
public abstract function getCredentials();
/**
* @return boolean true if the connection works, false otherwise
*/
public abstract function checkConnection();
/**
* uses json to setCredentials, the json must follow the form given in
* getCredentials
*
* @param array $data with the credentials
* @param string $url address of the server
* @param int $serverId ID of the server
* @returns bool if the credentials were in the correct format
*/
public abstract function setCredentials($data, $url, $serverId);
/**
* @return int desired caching time of results, in seconds. 0 = no caching
*/
public abstract function getCacheTime();
/**
* @return int age after which timetables are no longer refreshed should be
* greater then CacheTime
*/
public abstract function getRefreshTime();
/**
* Internal version of fetch, to be overridden by subclasses.
*
* @param $roomIds array with local ID as key and serverId as value
* @return array a recursive array that uses the roomID as key
* and has the schedule array as value. A shedule array contains an array in this format:
* ["start"=>'JJJJ-MM-DD HH:MM:SS',"end"=>'JJJJ-MM-DD HH:MM:SS',"title"=>string]
*/
protected abstract function fetchSchedulesInternal($roomId);
/**
* Method for fetching the schedule of the given rooms on a server.
*
* @param array $roomId array of room ID to fetch
* @return array|bool array containing the timetables as value and roomid as key as result, or false on error
*/
public final function fetchSchedule($requestedLocationIds)
{
if (!is_array($requestedLocationIds)) {
$this->error = 'No array of roomids was given to fetchSchedule';
return false;
}
if (empty($requestedLocationIds))
return array();
$NOW = time();
$dbquery1 = Database::simpleQuery("SELECT locationid, calendar, serverroomid, lastcalendarupdate
FROM location_info WHERE locationid IN (:locations)",
array('locations' => array_values($requestedLocationIds)));
$returnValue = [];
$remoteIds = [];
while ($row = $dbquery1->fetch(PDO::FETCH_ASSOC)) {
//Check if in cache if lastUpdate is null then it is interpreted as 1970
if ($row['lastcalendarupdate'] + $this->getCacheTime() > $NOW) {
$returnValue[$row['locationid']] = json_decode($row['calendar']);
} else {
$remoteIds[$row['locationid']] = $row['serverroomid'];
}
}
// No need for additional round trips to backend
if (empty($remoteIds)) {
return $returnValue;
}
// Check if we should refresh other rooms recently requested by front ends
if ($this->getRefreshTime() > $this->getCacheTime()) {
$dbquery4 = Database::simpleQuery("SELECT locationid, serverroomid FROM location_info
WHERE serverid = :serverid AND serverroomid NOT IN (:skiplist)
AND lastcalendarupdate BETWEEN :lowerage AND :upperage
LIMIT " . self::MAX_ADDIDIONAL_LOCATIONS, array(
'serverid' => $this->serverId,
'skiplist' => array_values($remoteIds),
'lowerage' => $NOW - $this->getRefreshTime(),
'upperage' => $NOW - $this->getCacheTime(),
));
while ($row = $dbquery4->fetch(PDO::FETCH_ASSOC)) {
$remoteIds[$row['locationid']] = $row['serverroomid'];
}
}
$backendResponse = $this->fetchSchedulesInternal($remoteIds);
if ($backendResponse === false) {
return false;
}
if ($this->getCacheTime() > 0) {
// Caching requested by backend, write to DB
foreach ($backendResponse as $serverRoomId => $calendar) {
$value = json_encode($calendar);
Database::simpleQuery("UPDATE location_info SET calendar = :ttable, lastcalendarupdate = :now
WHERE serverid = :serverid AND serverroomid = :serverroomid", array(
'serverid' => $this->serverId,
'serverroomid' => $serverRoomId,
'ttable' => $value,
'now' => $NOW
));
}
}
// Add rooms that were requested to the final return value
foreach ($remoteIds as $location => $serverRoomId) {
if (isset($backendResponse[$serverRoomId]) && in_array($location, $requestedLocationIds)) {
// Only add if we can map it back to our location id AND it was not an unsolicited coalesced refresh
$returnValue[$location] = $backendResponse[$serverRoomId];
}
}
return $returnValue;
}
/**
* @return false if there was no error string with error message if there was one
*/
public final function getError()
{
return $this->error;
}
/**
* Query path in array-representation of XML document.
* e.g. 'path/syntax/foo/wanteditem'
* This works for intermediate nodes (that have more children)
* and leaf nodes. The result is always an array on success, or
* false if not found.
*/
protected function getAttributes($array, $path)
{
if (!is_array($path)) {
// Convert 'path/syntax/foo/wanteditem' to array for further processing and recursive calls
$path = explode('/', $path);
}
do {
// Get next element from array, loop to ignore empty elements (so double slashes in the path are allowed)
$element = array_shift($path);
} while (empty($element) && !empty($path));
if (!isset($array[$element])) {
// Current path element does not exist - error
return false;
}
if (empty($path)) {
// Path is now empty which means we're at 'wanteditem' from out example above
if (!is_array($array[$element]) || !isset($array[$element][0])) {
// If it's a leaf node of the array, wrap it in plain array, so the function will
// always return an array on success
return array($array[$element]);
}
// 'wanteditem' is not a unique leaf node, return as is
// This means it's either a plain array, in case there are multiple 'wanteditem' elements on the same level
// or it's an associative array if 'wanteditem' has any sub-nodes
return $array[$element];
}
// Recurse
if (!is_array($array[$element])) {
// We're in the middle of the requested path, but the current element is already a leaf node with no
// children - error
return false;
}
if (isset($array[$element][0])) {
// The currently handled element of the path exists multiple times on the current level, so it is
// wrapped in a plain array - recurse into each one of them and merge the results
$return = [];
foreach ($array[$element] as $item) {
$test = $this->getAttributes($item, $path);
If (gettype($test) == "array") {
$return = array_merge($return, $test);
}
}
return $return;
}
// Unique non-leaf node - simple recursion
return $this->getAttributes($array[$element], $path);
}
/**
* @param string $response xml document to convert
* @return bool|array array representation of the xml if possible, false otherwise
*/
protected function toArray($response)
{
$cleanresponse = preg_replace('/(<\/?)(\w+):([^>]*>)/', '$1$2$3', $response);
try {
$xml = new SimpleXMLElement($cleanresponse);
} catch (Exception $e) {
$this->error = 'Could not parse reply as XML, got ' . get_class($e) . ': ' . $e->getMessage();
return false;
}
$array = json_decode(json_encode((array)$xml), true);
return $array;
}
}
