From 2e03cc50d8745762c8f50700098b920a8ec9a242 Mon Sep 17 00:00:00 2001
From: Terranom674 <thomas_dannenberg@web.de>
Date: Thu, 20 Aug 2026 15:48:29 +0200
Subject: [PATCH] Add WebDAV derivative gate diagnostics

---
 webdav-derivative.php | 260 ++++++++++++++----------------------------
 1 file changed, 83 insertions(+), 177 deletions(-)

diff --git a/webdav-derivative.php b/webdav-derivative.php
index 67f6875..86103b1 100644
--- a/webdav-derivative.php
+++ b/webdav-derivative.php
@@ -10,6 +10,19 @@ if (!defined('BRATONIEN_TOOLS_PATH'))
 }
 require_once(BRATONIEN_TOOLS_PATH.'include/webdav_materialize_runtime.inc.php');
 
+function bratonien_tools_webdav_derivative_debug($request_id, $event, array $fields=array())
+{
+  $parts = array('[BRAT-WD '.$request_id.']', $event);
+  foreach ($fields as $key => $value)
+  {
+    if (is_bool($value)) $value = $value ? '1' : '0';
+    elseif ($value === null) $value = 'NULL';
+    elseif (is_array($value) || is_object($value)) $value = json_encode($value);
+    $parts[] = $key.'='.str_replace(array("\r", "\n"), array('\\r', '\\n'), (string)$value);
+  }
+  error_log(implode(' ', $parts));
+}
+
 function bratonien_tools_webdav_derivative_abort($status, $message)
 {
   http_response_code((int)$status);
@@ -23,19 +36,15 @@ function bratonien_tools_webdav_derivative_decrypt_secret($blob, $hex_key)
 {
   $hex_key = trim((string)$hex_key);
   if (!preg_match('/^[a-f0-9]{64}$/', $hex_key)) return null;
-
   $outer = base64_decode(trim((string)$blob), true);
   $payload = is_string($outer) ? json_decode($outer, true) : null;
   if (!is_array($payload) || (int)($payload['v'] ?? 0) !== 1) return null;
-
   $iv = base64_decode((string)($payload['iv'] ?? ''), true);
   $tag = base64_decode((string)($payload['tag'] ?? ''), true);
   $cipher = base64_decode((string)($payload['data'] ?? ''), true);
   if (!is_string($iv) || !is_string($tag) || !is_string($cipher)) return null;
-
   $plain = openssl_decrypt($cipher, 'aes-256-gcm', hex2bin($hex_key), OPENSSL_RAW_DATA, $iv, $tag);
   if ($plain === false) return null;
-
   $decoded = json_decode((string)$plain, true);
   return is_array($decoded) ? $decoded : null;
 }
@@ -51,51 +60,24 @@ function bratonien_tools_webdav_derivative_download(array $source, $destination,
   $detail = '';
   $table = $GLOBALS['prefixeTable'].'bratonien_tools_nc_connections';
   $result = pwg_query('SELECT config_json, secret_blob FROM `'.$table.'` WHERE id='.(int)$source['connection_id'].' LIMIT 1');
-  if (!pwg_db_num_rows($result))
-  {
-    $detail = 'WebDAV-Verbindung nicht gefunden.';
-    return false;
-  }
-
+  if (!pwg_db_num_rows($result)) { $detail = 'WebDAV-Verbindung nicht gefunden.'; return false; }
   $row = pwg_db_fetch_assoc($result);
   $config = json_decode((string)$row['config_json'], true);
-  if (!is_array($config))
-  {
-    $detail = 'WebDAV-Konfiguration ist ungueltig.';
-    return false;
-  }
-
+  if (!is_array($config)) { $detail = 'WebDAV-Konfiguration ist ungueltig.'; return false; }
   $key_result = pwg_query("SELECT value FROM ".$GLOBALS['prefixeTable']."config WHERE param='bratonien_nc_connector_secret' LIMIT 1");
-  if (!pwg_db_num_rows($key_result))
-  {
-    $detail = 'Connector-Schluessel fehlt.';
-    return false;
-  }
-
+  if (!pwg_db_num_rows($key_result)) { $detail = 'Connector-Schluessel fehlt.'; return false; }
   $key_row = pwg_db_fetch_assoc($key_result);
   $credentials = bratonien_tools_webdav_derivative_decrypt_secret((string)$row['secret_blob'], (string)$key_row['value']);
-  if (!is_array($credentials))
-  {
-    $detail = 'WebDAV-Zugangsdaten konnten nicht gelesen werden.';
-    return false;
-  }
+  if (!is_array($credentials)) { $detail = 'WebDAV-Zugangsdaten konnten nicht gelesen werden.'; return false; }
 
   $base_url = rtrim((string)($config['nextcloud_url'] ?? ''), '/');
   $user = trim((string)($credentials['nextcloud_user'] ?? ''));
   $password = (string)($credentials['nextcloud_password'] ?? '');
   $webdav_path = trim((string)($source['webdav_path'] ?? ''), '/');
-  if ($base_url === '' || $user === '' || $password === '' || $webdav_path === '')
-  {
-    $detail = 'WebDAV-Bildquelle ist unvollstaendig.';
-    return false;
-  }
+  if ($base_url === '' || $user === '' || $password === '' || $webdav_path === '') { $detail = 'WebDAV-Bildquelle ist unvollstaendig.'; return false; }
 
   $fp = @fopen($destination, 'xb');
-  if (!$fp)
-  {
-    $detail = 'Temporaere Quelldatei konnte nicht angelegt werden.';
-    return false;
-  }
+  if (!$fp) { $detail = 'Temporaere Quelldatei konnte nicht angelegt werden.'; return false; }
 
   $url = $base_url.'/remote.php/dav/files/'.rawurlencode($user).'/'.bratonien_tools_webdav_derivative_quote_path($webdav_path);
   $ch = curl_init($url);
@@ -110,28 +92,24 @@ function bratonien_tools_webdav_derivative_download(array $source, $destination,
     CURLOPT_FILE => $fp,
     CURLOPT_USERAGENT => 'Bratonien-Tools-WebDAV-Materialize',
   ));
-
   $ok = curl_exec($ch);
   $errno = curl_errno($ch);
   $error = curl_error($ch);
   $http = (int)curl_getinfo($ch, CURLINFO_HTTP_CODE);
   curl_close($ch);
   fclose($fp);
-
   if ($ok === false || $errno !== 0 || $http < 200 || $http >= 300)
   {
     @unlink($destination);
     $detail = 'Nextcloud-Download fehlgeschlagen (HTTP '.$http.', cURL '.$errno.($error !== '' ? ': '.$error : '').').';
     return false;
   }
-
   if (!is_file($destination) || filesize($destination) < 1 || @getimagesize($destination) === false)
   {
     @unlink($destination);
     $detail = 'Nextcloud-Datei ist kein lesbares Bild.';
     return false;
   }
-
   return true;
 }
 
@@ -139,10 +117,8 @@ function bratonien_tools_webdav_derivative_inner_url($derivative_path)
 {
   $derivative_root = PHPWG_ROOT_PATH.PWG_DERIVATIVE_DIR;
   if (strpos($derivative_path, $derivative_root) !== 0) return null;
-
   $location = ltrim(substr($derivative_path, strlen($derivative_root)), '/');
   if ($location === '') return null;
-
   $segments = array_map('rawurlencode', explode('/', $location));
   return rtrim(get_absolute_root_url(), '/').'/i.php?/'.implode('/', $segments);
 }
@@ -151,7 +127,6 @@ function bratonien_tools_webdav_derivative_call_i($url, &$status, &$detail=null)
 {
   $detail = '';
   $status = 500;
-
   $ch = curl_init($url);
   curl_setopt_array($ch, array(
     CURLOPT_FOLLOWLOCATION => false,
@@ -160,29 +135,15 @@ function bratonien_tools_webdav_derivative_call_i($url, &$status, &$detail=null)
     CURLOPT_RETURNTRANSFER => false,
     CURLOPT_FAILONERROR => false,
     CURLOPT_USERAGENT => 'Bratonien-Tools-WebDAV-Materialize-Gate',
-    CURLOPT_WRITEFUNCTION => function($ch, $data)
-    {
-      return strlen($data);
-    },
+    CURLOPT_WRITEFUNCTION => function($ch, $data) { return strlen($data); },
   ));
-
   $ok = curl_exec($ch);
   $errno = curl_errno($ch);
   $error = curl_error($ch);
   $status = (int)curl_getinfo($ch, CURLINFO_HTTP_CODE);
   curl_close($ch);
-
-  if ($ok === false || $errno !== 0)
-  {
-    $detail = 'Interner i.php-Aufruf fehlgeschlagen (cURL '.$errno.($error !== '' ? ': '.$error : '').').';
-    return false;
-  }
-  if ($status < 200 || $status >= 400)
-  {
-    $detail = 'i.php antwortete mit HTTP '.$status.'.';
-    return false;
-  }
-
+  if ($ok === false || $errno !== 0) { $detail = 'Interner i.php-Aufruf fehlgeschlagen (cURL '.$errno.($error !== '' ? ': '.$error : '').').'; return false; }
+  if ($status < 200 || $status >= 400) { $detail = 'i.php antwortete mit HTTP '.$status.'.'; return false; }
   return true;
 }
 
@@ -190,18 +151,15 @@ function bratonien_tools_webdav_derivative_after_url($encoded)
 {
   $encoded = trim((string)$encoded);
   if ($encoded === '') return null;
-
   $raw = strtr($encoded, '-_', '+/');
   $padding = strlen($raw) % 4;
   if ($padding) $raw .= str_repeat('=', 4 - $padding);
   $url = base64_decode($raw, true);
   if (!is_string($url) || $url === '' || preg_match('/[\r\n]/', $url)) return null;
   if (strpos($url, '//') === 0) return null;
-
   if (preg_match('#^https?://#i', $url))
   {
-    $root = get_absolute_root_url();
-    $root_parts = parse_url($root);
+    $root_parts = parse_url(get_absolute_root_url());
     $url_parts = parse_url($url);
     if (!is_array($root_parts) || !is_array($url_parts)) return null;
     if (strcasecmp((string)($root_parts['scheme'] ?? ''), (string)($url_parts['scheme'] ?? '')) !== 0) return null;
@@ -209,7 +167,6 @@ function bratonien_tools_webdav_derivative_after_url($encoded)
     if ((int)($root_parts['port'] ?? 0) !== (int)($url_parts['port'] ?? 0)) return null;
     return $url;
   }
-
   if (strpos($url, ':') !== false && !preg_match('#^[A-Za-z0-9_./?&=%+-]+$#', $url)) return null;
   return $url;
 }
@@ -224,17 +181,11 @@ function bratonien_tools_webdav_derivative_needs_after_redirect($url)
 function bratonien_tools_webdav_derivative_serve($path)
 {
   clearstatcache(true, $path);
-  if (!is_file($path) || !is_readable($path))
-  {
-    bratonien_tools_webdav_derivative_abort(500, 'Piwigo-Derivat ist nicht lesbar.');
-  }
-
+  if (!is_file($path) || !is_readable($path)) bratonien_tools_webdav_derivative_abort(500, 'Piwigo-Derivat ist nicht lesbar.');
   $size = @getimagesize($path);
   $content_type = is_array($size) && !empty($size['mime']) ? (string)$size['mime'] : 'application/octet-stream';
-  $length = (int)filesize($path);
-
   header('Content-Type: '.$content_type);
-  header('Content-Length: '.$length);
+  header('Content-Length: '.(int)filesize($path));
   header('Cache-Control: public, max-age=31536000');
   header('X-Content-Type-Options: nosniff');
   if (($_SERVER['REQUEST_METHOD'] ?? 'GET') !== 'HEAD') readfile($path);
@@ -243,6 +194,9 @@ function bratonien_tools_webdav_derivative_serve($path)
 
 $image_id = (int)($_GET['id'] ?? 0);
 $variant = trim((string)($_GET['variant'] ?? ''));
+$request_id = bin2hex(random_bytes(4));
+bratonien_tools_webdav_derivative_debug($request_id, 'start', array('image_id'=>$image_id, 'variant'=>$variant));
+
 $after_url = bratonien_tools_webdav_derivative_after_url($_GET['after'] ?? '');
 $after_sig = trim((string)($_GET['sig'] ?? ''));
 if ($image_id < 1) bratonien_tools_webdav_derivative_abort(400, 'Bild-ID fehlt.');
@@ -257,17 +211,32 @@ $redirect_after = bratonien_tools_webdav_derivative_needs_after_redirect($after_
 $permission_condition = get_sql_condition_FandF(array('forbidden_categories'=>'category_id'), null, true);
 $access_result = pwg_query('SELECT 1 FROM '.IMAGE_CATEGORY_TABLE.' WHERE image_id='.$image_id.' AND '.$permission_condition.' LIMIT 1');
 if (!pwg_db_num_rows($access_result)) bratonien_tools_webdav_derivative_abort(403, 'Kein Zugriff auf dieses Bild.');
-
 $result = pwg_query('SELECT * FROM '.IMAGES_TABLE.' WHERE id='.$image_id.' LIMIT 1');
 if (!pwg_db_num_rows($result)) bratonien_tools_webdav_derivative_abort(404, 'Bild nicht gefunden.');
 $image_row = pwg_db_fetch_assoc($result);
 
+$raw_source_path = (string)($image_row['path'] ?? '');
+$absolute_source_path = $raw_source_path;
+if ($absolute_source_path !== '' && strpos($absolute_source_path, '/') !== 0)
+{
+  $absolute_source_path = PHPWG_ROOT_PATH.ltrim(preg_replace('#^\./#', '', $absolute_source_path), '/');
+}
+bratonien_tools_webdav_derivative_debug($request_id, 'source_before_resolve', array(
+  'path'=>$raw_source_path,
+  'is_link'=>$absolute_source_path !== '' && is_link($absolute_source_path),
+  'realpath'=>$absolute_source_path !== '' ? (realpath($absolute_source_path) ?: 'FALSE') : 'EMPTY',
+));
+
 $source = bratonien_tools_webdav_materialize_source_info($image_id);
-if (!$source) bratonien_tools_webdav_derivative_abort(404, 'Keine WebDAV-Quelle fuer dieses Bild gefunden.');
+if (!$source)
+{
+  bratonien_tools_webdav_derivative_debug($request_id, 'source_resolve_failed');
+  bratonien_tools_webdav_derivative_abort(404, 'Keine WebDAV-Quelle fuer dieses Bild gefunden.');
+}
+bratonien_tools_webdav_derivative_debug($request_id, 'source_resolved', array('connection_id'=>$source['connection_id'] ?? 0, 'root_fileid'=>$source['root_fileid'] ?? 0, 'webdav_path'=>$source['webdav_path'] ?? ''));
 
 $params = bratonien_tools_webdav_materialize_params_from_variant($variant);
 if (!$params) bratonien_tools_webdav_derivative_abort(400, 'Unbekannte Derivat-Variante.');
-
 $real_src = new SrcImage($image_row);
 $real_derivative = new DerivativeImage($params, $real_src);
 if ($real_derivative->same_as_source())
@@ -280,85 +249,49 @@ if ($real_derivative->same_as_source())
 
 $target_path = $real_derivative->get_path();
 $derivative_root = PHPWG_ROOT_PATH.PWG_DERIVATIVE_DIR;
-if ($target_path === '' || strpos($target_path, $derivative_root) !== 0)
-{
-  bratonien_tools_webdav_derivative_abort(500, 'Ungueltiger Piwigo-Derivatpfad.');
-}
+if ($target_path === '' || strpos($target_path, $derivative_root) !== 0) bratonien_tools_webdav_derivative_abort(500, 'Ungueltiger Piwigo-Derivatpfad.');
 if (is_file($target_path) && is_readable($target_path))
 {
-  if ($redirect_after !== null)
-  {
-    header('Location: '.$redirect_after, true, 302);
-    exit;
-  }
+  bratonien_tools_webdav_derivative_debug($request_id, 'target_exists', array('target'=>$target_path));
+  if ($redirect_after !== null) { header('Location: '.$redirect_after, true, 302); exit; }
   bratonien_tools_webdav_derivative_serve($target_path);
 }
 
-$shadow_path = (string)($image_row['path'] ?? '');
+$shadow_path = $raw_source_path;
 if ($shadow_path === '') bratonien_tools_webdav_derivative_abort(500, 'Piwigo-Quellpfad fehlt.');
-if (strpos($shadow_path, '/') !== 0)
-{
-  $shadow_path = PHPWG_ROOT_PATH.ltrim(preg_replace('#^\./#', '', $shadow_path), '/');
-}
+if (strpos($shadow_path, '/') !== 0) $shadow_path = PHPWG_ROOT_PATH.ltrim(preg_replace('#^\./#', '', $shadow_path), '/');
 $shadow_normalized = str_replace('\\', '/', $shadow_path);
-if (!preg_match('#/_data/bratonien-tools/nc-webdav-gallery/connection-'.(int)$source['connection_id'].'/#', $shadow_normalized))
-{
-  bratonien_tools_webdav_derivative_abort(500, 'Piwigo-Quellpfad liegt nicht im WebDAV-Shadow-Baum.');
-}
-if (!is_link($shadow_path))
-{
-  bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Shadow-Quelle ist kein Placeholder-Symlink.');
-}
+if (!preg_match('#/_data/bratonien-tools/nc-webdav-gallery/connection-'.(int)$source['connection_id'].'/#', $shadow_normalized)) bratonien_tools_webdav_derivative_abort(500, 'Piwigo-Quellpfad liegt nicht im WebDAV-Shadow-Baum.');
+if (!is_link($shadow_path)) bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Shadow-Quelle ist kein Placeholder-Symlink.');
 
 $placeholder_target = realpath($shadow_path);
 $placeholder_normalized = $placeholder_target === false ? '' : str_replace('\\', '/', $placeholder_target);
-if (
-  $placeholder_target === false
-  || !preg_match(
-    '#/nc-webdav-source/connection-'.(int)$source['connection_id'].'/root-'.(int)$source['root_fileid'].'/#',
-    $placeholder_normalized
-  )
-)
-{
-  bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Placeholder-Ziel ist ungueltig.');
-}
+if ($placeholder_target === false || !preg_match('#/nc-webdav-source/connection-'.(int)$source['connection_id'].'/root-'.(int)$source['root_fileid'].'/#', $placeholder_normalized)) bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Placeholder-Ziel ist ungueltig.');
 
 $shadow_dir = dirname($shadow_path);
-if (!is_dir($shadow_dir) || !is_writable($shadow_dir))
-{
-  bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Shadow-Verzeichnis ist fuer PHP nicht beschreibbar.');
-}
-
+if (!is_dir($shadow_dir) || !is_writable($shadow_dir)) bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Shadow-Verzeichnis ist fuer PHP nicht beschreibbar.');
 $upload_dir = rtrim((string)($GLOBALS['conf']['upload_dir'] ?? './upload'), '/');
 $work_rel_dir = $upload_dir.'/bratonien-webdav-materialize';
 $work_root = PHPWG_ROOT_PATH.$work_rel_dir;
-if (!is_dir($work_root) && !@mkdir($work_root, 0755, true))
-{
-  bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Materialisierungsbereich konnte nicht angelegt werden.');
-}
-if (!is_writable($work_root))
-{
-  bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Materialisierungsbereich ist fuer PHP nicht beschreibbar.');
-}
+if (!is_dir($work_root) && !@mkdir($work_root, 0755, true)) bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Materialisierungsbereich konnte nicht angelegt werden.');
+if (!is_writable($work_root)) bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Materialisierungsbereich ist fuer PHP nicht beschreibbar.');
 
 $lock_path = $work_root.'/image-'.$image_id.'.lock';
+bratonien_tools_webdav_derivative_debug($request_id, 'waiting_lock', array('lock'=>$lock_path, 'is_link'=>is_link($shadow_path), 'realpath'=>realpath($shadow_path) ?: 'FALSE'));
 $lock = @fopen($lock_path, 'c');
 if (!$lock || !flock($lock, LOCK_EX))
 {
   if ($lock) fclose($lock);
   bratonien_tools_webdav_derivative_abort(503, 'WebDAV-Materialisierungslock konnte nicht gesetzt werden.');
 }
+bratonien_tools_webdav_derivative_debug($request_id, 'lock_acquired', array('is_link'=>is_link($shadow_path), 'realpath'=>realpath($shadow_path) ?: 'FALSE'));
 
 clearstatcache(true, $target_path);
 if (is_file($target_path) && is_readable($target_path))
 {
-  @flock($lock, LOCK_UN);
-  @fclose($lock);
-  if ($redirect_after !== null)
-  {
-    header('Location: '.$redirect_after, true, 302);
-    exit;
-  }
+  bratonien_tools_webdav_derivative_debug($request_id, 'target_created_while_waiting', array('target'=>$target_path));
+  @flock($lock, LOCK_UN); @fclose($lock);
+  if ($redirect_after !== null) { header('Location: '.$redirect_after, true, 302); exit; }
   bratonien_tools_webdav_derivative_serve($target_path);
 }
 
@@ -369,21 +302,19 @@ $placeholder_backup = $shadow_path.'.bratonien-placeholder';
 $swapped = false;
 $cleaned = false;
 
-$cleanup = function() use (&$cleaned, &$swapped, $shadow_path, $staging_path, $placeholder_backup, $download_path, $lock)
+$cleanup = function() use (&$cleaned, &$swapped, $shadow_path, $staging_path, $placeholder_backup, $download_path, $lock, $request_id)
 {
   if ($cleaned) return;
   $cleaned = true;
-
   if ($swapped)
   {
     if (is_file($shadow_path) && !is_link($shadow_path)) @unlink($shadow_path);
     if (is_link($placeholder_backup)) @rename($placeholder_backup, $shadow_path);
     $swapped = false;
   }
-
   if (is_file($staging_path) || is_link($staging_path)) @unlink($staging_path);
   if (is_file($download_path)) @unlink($download_path);
-
+  bratonien_tools_webdav_derivative_debug($request_id, 'restored', array('is_link'=>is_link($shadow_path), 'realpath'=>realpath($shadow_path) ?: 'FALSE'));
   @flock($lock, LOCK_UN);
   @fclose($lock);
 };
@@ -391,69 +322,44 @@ register_shutdown_function($cleanup);
 
 try
 {
-  if (is_link($placeholder_backup))
-  {
-    bratonien_tools_webdav_derivative_abort(503, 'WebDAV-Placeholder-Backup existiert bereits; vorheriger Materialisierungslauf ist nicht sauber abgeschlossen.');
-  }
-
+  if (is_link($placeholder_backup)) bratonien_tools_webdav_derivative_abort(503, 'WebDAV-Placeholder-Backup existiert bereits; vorheriger Materialisierungslauf ist nicht sauber abgeschlossen.');
   $detail = '';
-  if (!bratonien_tools_webdav_derivative_download($source, $download_path, $detail))
-  {
-    bratonien_tools_webdav_derivative_abort(502, $detail);
-  }
+  $download_start = microtime(true);
+  if (!bratonien_tools_webdav_derivative_download($source, $download_path, $detail)) bratonien_tools_webdav_derivative_abort(502, $detail);
+  bratonien_tools_webdav_derivative_debug($request_id, 'download_done', array('ms'=>round((microtime(true)-$download_start)*1000, 1), 'bytes'=>@filesize($download_path) ?: 0));
 
-  if (!@copy($download_path, $staging_path))
-  {
-    bratonien_tools_webdav_derivative_abort(500, 'Original konnte nicht in den WebDAV-Shadow-Baum kopiert werden.');
-  }
+  if (!@copy($download_path, $staging_path)) bratonien_tools_webdav_derivative_abort(500, 'Original konnte nicht in den WebDAV-Shadow-Baum kopiert werden.');
   @chmod($staging_path, 0644);
-  if (@getimagesize($staging_path) === false)
-  {
-    bratonien_tools_webdav_derivative_abort(500, 'Materialisierte Shadow-Quelle ist kein gueltiges Bild.');
-  }
+  if (@getimagesize($staging_path) === false) bratonien_tools_webdav_derivative_abort(500, 'Materialisierte Shadow-Quelle ist kein gueltiges Bild.');
 
-  if (!@rename($shadow_path, $placeholder_backup))
-  {
-    bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Placeholder konnte nicht temporaer gesichert werden.');
-  }
+  bratonien_tools_webdav_derivative_debug($request_id, 'swap_begin', array('placeholder'=>$placeholder_target));
+  if (!@rename($shadow_path, $placeholder_backup)) bratonien_tools_webdav_derivative_abort(500, 'WebDAV-Placeholder konnte nicht temporaer gesichert werden.');
   if (!@rename($staging_path, $shadow_path))
   {
     @rename($placeholder_backup, $shadow_path);
     bratonien_tools_webdav_derivative_abort(500, 'Materialisiertes Original konnte nicht am Piwigo-Quellpfad aktiviert werden.');
   }
   $swapped = true;
-
   clearstatcache(true, $shadow_path);
-  if (!is_file($shadow_path) || is_link($shadow_path) || @getimagesize($shadow_path) === false)
-  {
-    bratonien_tools_webdav_derivative_abort(500, 'Piwigo-Quellpfad enthaelt nach Materialisierung kein gueltiges Original.');
-  }
+  bratonien_tools_webdav_derivative_debug($request_id, 'swapped', array('is_link'=>is_link($shadow_path), 'realpath'=>realpath($shadow_path) ?: 'FALSE'));
+  if (!is_file($shadow_path) || is_link($shadow_path) || @getimagesize($shadow_path) === false) bratonien_tools_webdav_derivative_abort(500, 'Piwigo-Quellpfad enthaelt nach Materialisierung kein gueltiges Original.');
 
   $inner_url = bratonien_tools_webdav_derivative_inner_url($target_path);
-  if ($inner_url === null)
-  {
-    bratonien_tools_webdav_derivative_abort(500, 'Piwigo-i.php-URL konnte nicht bestimmt werden.');
-  }
-
+  if ($inner_url === null) bratonien_tools_webdav_derivative_abort(500, 'Piwigo-i.php-URL konnte nicht bestimmt werden.');
   $inner_status = 500;
-  if (!bratonien_tools_webdav_derivative_call_i($inner_url, $inner_status, $detail))
-  {
-    bratonien_tools_webdav_derivative_abort(502, $detail);
-  }
+  $i_start = microtime(true);
+  bratonien_tools_webdav_derivative_debug($request_id, 'i_start', array('url'=>$inner_url));
+  $i_ok = bratonien_tools_webdav_derivative_call_i($inner_url, $inner_status, $detail);
+  bratonien_tools_webdav_derivative_debug($request_id, 'i_done', array('status'=>$inner_status, 'ok'=>$i_ok, 'ms'=>round((microtime(true)-$i_start)*1000, 1), 'detail'=>$detail));
+  if (!$i_ok) bratonien_tools_webdav_derivative_abort(502, $detail);
 
   clearstatcache(true, $target_path);
   $final_size = @getimagesize($target_path);
-  if (!is_file($target_path) || !is_readable($target_path) || !is_array($final_size))
-  {
-    bratonien_tools_webdav_derivative_abort(500, 'Piwigo hat kein gueltiges finales Derivat erzeugt.');
-  }
+  if (!is_file($target_path) || !is_readable($target_path) || !is_array($final_size)) bratonien_tools_webdav_derivative_abort(500, 'Piwigo hat kein gueltiges finales Derivat erzeugt.');
 
   $cleanup();
-  if ($redirect_after !== null)
-  {
-    header('Location: '.$redirect_after, true, 302);
-    exit;
-  }
+  bratonien_tools_webdav_derivative_debug($request_id, 'serve', array('target'=>$target_path, 'width'=>$final_size[0] ?? 0, 'height'=>$final_size[1] ?? 0));
+  if ($redirect_after !== null) { header('Location: '.$redirect_after, true, 302); exit; }
   bratonien_tools_webdav_derivative_serve($target_path);
 }
 finally