From c97142ad3edea1652f39e7fb58c8c3443f8a0f67 Mon Sep 17 00:00:00 2001
From: Evan Prodromou <evan@controlyourself.ca>
Date: Sun, 8 Mar 2009 11:50:55 -0700
Subject: [PATCH] first version of plugin for pingback and trackback (no
 trackback yet)

---
 plugins/LinkbackPlugin.php | 140 +++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 plugins/LinkbackPlugin.php

diff --git a/plugins/LinkbackPlugin.php b/plugins/LinkbackPlugin.php
new file mode 100644
index 0000000000..77adfa87d1
--- /dev/null
+++ b/plugins/LinkbackPlugin.php
@@ -0,0 +1,140 @@
+<?php
+/**
+ * Laconica, the distributed open-source microblogging tool
+ *
+ * Plugin to do linkbacks for notices containing links
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Plugin
+ * @package   Laconica
+ * @author    Evan Prodromou <evan@controlyourself.ca>
+ * @copyright 2009 Control Yourself, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link      http://laconi.ca/
+ */
+
+if (!defined('LACONICA')) {
+    exit(1);
+}
+
+require_once('Auth/Yadis/Yadis.php');
+
+define('LINKBACKPLUGIN_VERSION', '0.1');
+
+/**
+ * Plugin to do linkbacks for notices containing URLs
+ *
+ * After new notices are saved, we check their text for URLs. If there
+ * are URLs, we test each URL to see if it supports any
+ *
+ * @category Plugin
+ * @package  Laconica
+ * @author   Evan Prodromou <evan@controlyourself.ca>
+ * @license  http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link     http://laconi.ca/
+ *
+ * @see      Event
+ */
+
+class LinkbackPlugin extends Plugin
+{
+    var $notice = null;
+
+    function __construct()
+    {
+        parent::__construct();
+    }
+
+    function onEndNoticeSave($notice)
+    {
+        if ($notice->is_local == 1) {
+            // Try to avoid actually mucking with the
+            // notice content
+            $c = $notice->content;
+            $this->notice = $notice;
+            // Ignoring results
+            common_replace_urls_callback($c,
+                                         array($this, 'linkbackUrl'));
+        }
+        return true;
+    }
+
+    function linkbackUrl($url)
+    {
+        $orig = $url;
+        $url = htmlspecialchars_decode($orig);
+        $scheme = parse_url($url, PHP_URL_SCHEME);
+        if (!in_array($scheme, array('http', 'https'))) {
+            return $orig;
+        }
+
+        // XXX: Do a HEAD first to save some time/bandwidth
+
+        $fetcher = Auth_Yadis_Yadis::getHTTPFetcher();
+
+        $result = $fetcher->get($url,
+                                array('User-Agent: ' . $this->userAgent(),
+                                      'Accept: application/html+xml,text/html'));
+
+        if (!in_array($result->status, array('200', '206'))) {
+            return $orig;
+        }
+
+        if (array_key_exists('X-Pingback', $result->headers)) {
+            $endpoint = $result->headers['X-Pingback'];
+        } else if (preg_match('/<link rel="pingback" href="([^"]+)" ?/?>/',
+                              $result->body,
+                              $match)) {
+            $endpoint = $match[1];
+        } else {
+            // XXX: do Trackback lookup
+            return $orig;
+        }
+
+        $this->pingback($url, $endpoint);
+        return $orig;
+    }
+
+    function pingback($url, $endpoint)
+    {
+        $args = array($this->notice->uri, $url);
+
+        $request = xmlrpc_encode_request('pingback.ping', $args);
+        $context = stream_context_create(array('http' => array('method' => "POST",
+                                                               'header' =>
+                                                               "Content-Type: text/xml\r\n".
+                                                               "User-Agent: " . $this->userAgent(),
+                                                               'content' => $request)));
+        $file = file_get_contents($endpoint, false, $context);
+        $response = xmlrpc_decode($file);
+        if (xmlrpc_is_fault($response)) {
+            common_log(LOG_WARNING,
+                       "Pingback error for '$url' ($endpoint): ".
+                       "$response[faultString] ($response[faultCode])");
+        } else {
+            common_log(LOG_INFO,
+                       "Pingback success for '$url' ($endpoint): ".
+                       "'$response'");
+        }
+    }
+
+    function userAgent()
+    {
+        return 'LinkbackPlugin/'.LINKBACKPLUGIN_VERSION .
+          ' Laconica/' . LACONICA_VERSION;
+    }
+}