add log messages to debug which case a URL is hitting

lib/Formats/Mf2.php

@@ -5,6 +5,12 @@ use HTMLPurifier, HTMLPurifier_Config;
 
 class Mf2 {
 
+  private static function _debug($msg) {
+    syslog(LOG_INFO, $msg);
+    if(array_key_exists('REMOTE_ADDR', $_SERVER))
+      header("X-Parse-Debug: " . $msg);
+  }
+
   public static function parse($mf2, $url, $http) {
     if(count($mf2['items']) == 0)
       return false;
@@ -19,6 +25,7 @@ class Mf2 {
           $urls = $item['properties']['url'];
           $urls = array_map('\normalize_url', $urls);
           if(in_array($url, $urls)) {
+            self::_debug("1: Recognized $url as an h-entry because an h-entry on the page matched the URL of the request");
             return self::parseAsHEntry($mf2, $item, $http, $url);
           }
           $lastSeenEntry = $item;
@@ -29,12 +36,14 @@ class Mf2 {
 
     // If there was more than one h-entry on the page, treat the whole page as a feed
     if($hentrys > 1) {
+      self::_debug("2: Recognized $url as an h-feed because there are more than one h-entry on the page");
       return self::parseAsHFeed($mf2, $http);
     }
 
     // If the first item is an h-feed, parse as a feed
     $first = $mf2['items'][0];
     if(in_array('h-feed', $first['type'])) {
+      self::_debug("3: Recognized $url as an h-feed because the first item is an h-feed");
       return self::parseAsHFeed($mf2, $http);
     }
 
@@ -48,6 +57,7 @@ class Mf2 {
         if(in_array($url, $urls)) {
           // TODO: check for children h-entrys (like tantek.com), or sibling h-entries (like aaronparecki.com)
           // and return the result as a feed instead
+          self::_debug("4: Recognized $url as an h-card because an h-card on the page matched the URL of the request");
           return self::parseAsHCard($item, $http, $url);
         }
       }
@@ -59,6 +69,7 @@ class Mf2 {
         $urls = $lastSeenEntry['properties']['url'];
         $urls = array_map('\normalize_url', $urls);
         if(count($urls) && !in_array($url, $urls)) {
+          self::_debug("5: Recognized $url as an h-feed no h-entrys on the page matched the URL of the request");
           return self::parseAsHFeed($mf2, $http);
         }
       }
@@ -68,10 +79,13 @@ class Mf2 {
     foreach($mf2['items'] as $item) {
       // Otherwise check for an h-entry
       if(in_array('h-entry', $item['type']) || in_array('h-cite', $item['type'])) {
+        self::_debug("6: $url is falling back to the first h-entry on the page");
         return self::parseAsHEntry($mf2, $item, $http);
       }
     }
 
+    self::_debug("E: No object at $url was recognized");
+
     return false;
   }