[dozmod] api: Add error checks, implement lecture list resource type

1 files changed, 115 insertions, 55 deletions

diff --git a/modules-available/dozmod/api.inc.php b/modules-available/dozmod/api.inc.php
index b37c668c..e5214a55 100644
--- a/modules-available/dozmod/api.inc.php
+++ b/modules-available/dozmod/api.inc.php
@@ -1,3 +1,4 @@
+
 <?php
 /* small API server that acts as a proxy to the dozmod server.
 * To reduce the number of requests and connections to dozmod-server, results
@@ -5,7 +6,7 @@
 *
 * Required Configuration:
 * CONFIG_DOZMOD_EXPIRE: Expiration time in seconds for the cache
-* CONFIG_DOZMOD: URL to the dozmod server
+* CONFIG_DOZMOD_URL: URL to the dozmod server
 *
 **/
 
@@ -15,9 +16,9 @@ if (!Module::isAvailable('locations')) {
 }
 
 
-define('LIST_URL', CONFIG_DOZMOD . '/vmchooser/list');
-define('VMX_URL', CONFIG_DOZMOD . '/vmchooser/lecture');
-$availableRessources = ['vmx', 'test', 'netrules'];
+define('LIST_URL', CONFIG_DOZMOD_URL . '/vmchooser/list');
+define('VMX_URL', CONFIG_DOZMOD_URL . '/vmchooser/lecture');
+$availableRessources = ['list', 'vmx', 'test', 'netrules'];
 
 /* BEGIN: A simple caching mechanism ---------------------------- */
 
@@ -40,9 +41,9 @@ function cache_put($key, $value)
 function cache_has($key)
 {
     $filename = cache_key_to_filename($key);
-    $mtime = filemtime($filename);
+    $mtime = @filemtime($filename);
 
-    if (!$mtime) {
+    if ($mtime === false) {
         return false; // cache miss
     }
     if (time() - $mtime > CONFIG_DOZMOD_EXPIRE) {
@@ -66,9 +67,9 @@ function cache_get_passthru($key)
     $fp = fopen($filename, "r");
     if ($fp) {
         fpassthru($fp);
-    } else {
-        Util::traceError("cannot open file");
+        exit;
     }
+    error_log('Cannot passthrough cache file ' . $filename);
 }
 
 /* END: Cache ---------------------------------------------------- */
@@ -81,25 +82,29 @@ function cache_get_passthru($key)
 **/
 
 
-function println($str) { echo "$str\n"; }
-
-/* return an array of lecutre uuids.
-* Parameter: an array with location Ids
-* */
-function _getLecturesForLocations($locationIds)
+/**
+ * Get list of active lectures for given locations.
+ *
+ * @return string the raw xml data.
+ */
+function _getLecturesForLocations($locationIds, $examMode)
 {
-
-    /* if in any of the locations there is an exam active, consider the client
-    to be in "exam-mode" and only offer him exams (no lectures) */
-    $examMode = false;
-
-    if (Module::isAvailable('exams')) {
-        $examMode = Exams::isInExamMode($locationIds);
-    }
     $ids = implode('%20', $locationIds);
     $url = LIST_URL . "?locations=$ids" . ($examMode ? '&exams' : '');
-    $responseXML = Download::asString($url, 60, $code);
+    return Download::asString($url, 60, $code);
+}
+
+/**
+ * Takes raw lecture list xml, returns array of uuids.
+ *
+ * @param string $responseXML XML from dozmod server
+ * @return array list of UUIDs, false on error
+ */
+function xmlToLectureIds($responseXML)
+{
     $xml = new SimpleXMLElement($responseXML);
+    if (!isset($xml->eintrag))
+        return [];
 
     $uuids = [];
     foreach ($xml->eintrag as $e) {
@@ -109,16 +114,48 @@ function _getLecturesForLocations($locationIds)
 }
 
 /** Caching wrapper around _getLecturesForLocations() */
-function getLecturesForLocations($locationIds)
+function getListForLocations($locationIds, $raw)
 {
+    /* if in any of the locations there is an exam active, consider the client
+        to be in "exam-mode" and only offer him exams (no lectures) */
     $key = 'lectures_' . cache_hash($locationIds);
-    if (cache_has($key)) {
+    $examMode = false;
+    if (Module::isAvailable('exams')) {
+        $examMode = Exams::isInExamMode($locationIds);
+        if ($examMode) {
+            $key .= '_exams';
+        }
+    }
+    $rawKey = $key . '_raw';
+    if ($raw) {
+        Header('Content-Type: text/xml; charset=utf-8');
+        if (cache_has($rawKey)) {
+            cache_get_passthru($rawKey);
+        }
+    } elseif (cache_has($key)) {
         return unserialize(cache_get($key));
-    } else {
-        $value = _getLecturesForLocations($locationIds);
-        cache_put($key, serialize($value));
-        return $value;
     }
+    // Not in cache
+    $value = _getLecturesForLocations($locationIds, $examMode);
+    if ($value === false)
+        return false;
+    cache_put($rawKey, $value);
+    $list = xmlToLectureIds($value);
+    cache_put($key, serialize($list));
+    if ($raw) {
+        die($value);
+    }
+    return $list;
+}
+
+function getLectureUuidsForLocations($locationIds)
+{
+    return getListForLocations($locationIds, false);
+}
+
+function outputLectureXmlForLocation($locationIds)
+{
+    return getListForLocations($locationIds, true);
 }
 
 function _getVMX($lecture_uuid)
@@ -129,58 +166,81 @@ function _getVMX($lecture_uuid)
 }
 
 /** Caching wrapper around _getVMX() **/
-function getVMX($lecture_uuid)
+function outputVMX($lecture_uuid)
 {
     $key = 'vmx_' . $lecture_uuid;
     if (cache_has($key)) {
         cache_get_passthru($key);
     } else {
         $value = _getVMX($lecture_uuid);
+        if ($value === false)
+            return false;
         cache_put($key, $value);
-        return $value;
+        die($value);
     }
 }
 
+function fatalDozmodUnreachable()
+{
+    Header('HTTP/1.1 504 Gateway Timeout');
+    die('Resource not available');
+}
 
-// -----------------------------------------------------------------------------//
-$ip = $_SERVER['REMOTE_ADDR'];
-if (substr($ip, 0, 7) === '::ffff:') {
-    $ip = substr($ip, 7);
+function readLectureParam()
+{
+    global  $location_ids;
+    $lecture  = Request::get('lecture', false, 'string');
+    if ($lecture === false) {
+        Header('HTTP/1.1 400 Bad Request');
+        die('Missing lecture UUID');
+    }
+    $lectures = getLectureUuidsForLocations($location_ids);
+    if ($lectures === false) {
+        fatalDozmodUnreachable();
+    }
+    /* check that the user requests a lecture that he is allowed to have */
+    if (!in_array($lecture, $lectures)) {
+        Header('HTTP/1.1 403 Forbidden');
+        die("You don't have permission to access this lecture");
+    }
+    return $lecture;
 }
 
+
+// -----------------------------------------------------------------------------//
 /* request data, don't trust */
 $resource   = Request::get('resource', false, 'string');
-$lecture    = Request::get('lecture', false, 'string');
 
 if ($resource === false) {
     Util::traceError("you have to specify the 'resource' parameter");
 }
-if ($lecture === false) {
-    Util::traceError("you have to specify the 'lecture' parameter");
+
+if (!in_array($resource, $availableRessources)) {
+    Util::traceError("unknown resource: $resource");
 }
 
+$ip = $_SERVER['REMOTE_ADDR'];
+if (substr($ip, 0, 7) === '::ffff:') {
+    $ip = substr($ip, 7);
+}
+
+
 /* lookup location id(s) */
 $location_ids = Location::getFromIp($ip);
 $location_ids = Location::getLocationRootChain($location_ids);
 
-/* lookup lecture uuids */
-$lectures = getLecturesForLocations($location_ids);
-
-/* validate request -------------------------------------------- */
-/* check resources */
-if (!in_array($resource, $availableRessources)) {
-    Util::traceError("unknown resource: $resource");
+if ($resource === 'vmx') {
+    $lecture = readLectureParam();
+    outputVMX($lecture);
+    // outputVMX does not return on success
+    fatalDozmodUnreachable();
 }
 
-/* check that the user requests a lecture that he is allowed to have */
-if (!in_array($lecture, $lectures)) {
-    Util::traceError("client is not allowed to access this lecture: $lecture");
+if ($resource === 'list') {
+    outputLectureXmlForLocation($location_ids);
+    // Won't return on success...
+    fatalDozmodUnreachable();
 }
 
-if ($resource === 'vmx') {
-    echo getVMX($lecture);
-} else if ($resource === 'test') {
-    echo "Here's your special test data!";
-} else {
-    echo "I don't know how to give you that resource";
-}
+Header('HTTP/1.1 400 Bad Request');
+die("I don't know how to give you that resource");