Add a robots.txt URL to the site root

Adds a robots.txt file to the site root. Defaults defined by
'robotstxt' section of config. New events StartRobotsTxt and
EndRobotsTxt to let plugins add information. Probably not
useful if path is not /, but won't hurt anything, either.

EVENTS.txt

@@ -708,3 +708,9 @@ EndUserRegister: When a new user has been registered
 - &$profile: new profile data
 - &$user: new user account
 
+StartRobotsTxt: Before outputting the robots.txt page
+- &$action: RobotstxtAction being shown
+
+EndRobotsTxt: After the default robots.txt page (good place for customization)
+- &$action: RobotstxtAction being shown
+

README

@@ -1496,6 +1496,20 @@ interface. It also makes the user's profile the root URL.
 enabled: Whether to run in "single user mode". Default false.
 nickname: nickname of the single user.
 
+robotstxt
+---------
+
+We put out a default robots.txt file to guide the processing of
+Web crawlers. See http://www.robotstxt.org/ for more information
+on the format of this file.
+
+crawldelay: if non-empty, this value is provided as the Crawl-Delay:
+            for the robots.txt file. see http://ur1.ca/l5a0
+            for more information. Default is zero, no explicit delay.
+disallow: Array of (virtual) directories to disallow. Default is 'main',
+          'search', 'message', 'settings', 'admin'. Ignored when site
+          is private, in which case the entire site ('/') is disallowed.
+
 Plugins
 =======
 

actions/robotstxt.php

@@ -0,0 +1,100 @@
+<?php
+/**
+ * StatusNet - the distributed open-source microblogging tool
+ * Copyright (C) 2010, StatusNet, Inc.
+ *
+ * robots.txt generator
+ *
+ * PHP version 5
+ *
+ * @category Action
+ * @package  StatusNet
+ * @author   Evan Prodromou <evan@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl.html AGPLv3
+ * @link     http://status.net/
+ *
+ * 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/>.
+ */
+
+if (!defined('STATUSNET')) {
+    exit(1);
+}
+
+/**
+ * Prints out a static robots.txt
+ *
+ * @category Action
+ * @package  StatusNet
+ * @author   Evan Prodromou <evan@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl.html AGPLv3
+ * @link     http://status.net/
+ */
+
+class RobotstxtAction extends Action
+{
+    /**
+     * Handles requests
+     *
+     * Since this is a relatively static document, we
+     * don't do a prepare()
+     *
+     * @param array $args GET, POST, and URL params; unused.
+     *
+     * @return void
+     */
+
+    function handle($args)
+    {
+        if (Event::handle('StartRobotsTxt', array($this))) {
+
+            header('Content-Type: text/plain');
+
+            print "User-Agent: *\n";
+
+            if (common_config('site', 'private')) {
+
+                print "Disallow: /\n";
+
+            } else {
+
+                $disallow = common_config('robotstxt', 'disallow');
+
+                foreach ($disallow as $dir) {
+                    print "Disallow: /$dir/\n";
+                }
+
+                $crawldelay = common_config('robotstxt', 'crawldelay');
+
+                if (!empty($crawldelay)) {
+                    print "Crawl-delay: " . $crawldelay . "\n";
+                }
+            }
+
+            Event::handle('EndRobotsTxt', array($this));
+        }
+    }
+
+    /**
+     * Return true; this page doesn't touch the DB.
+     *
+     * @param array $args other arguments
+     *
+     * @return boolean is read only action?
+     */
+
+    function isReadOnly($args)
+    {
+        return true;
+    }
+}

index.php

@@ -285,8 +285,9 @@ function main()
     if (!$user && common_config('site', 'private')
         && !isLoginAction($action)
         && !preg_match('/rss$/', $action)
-        && !preg_match('/^Api/', $action)
-    ) {
+        && $action != 'robotstxt'
+        && !preg_match('/^Api/', $action)) {
+
         // set returnto
         $rargs =& common_copy_args($args);
         unset($rargs['action']);

lib/default.php

@@ -270,4 +270,8 @@ $default =
         'singleuser' =>
         array('enabled' => false,
               'nickname' => null),
+        'robotstxt' =>
+        array('crawldelay' => 0,
+              'disallow' => array('main', 'settings', 'admin', 'search', 'message')
+              ),
         );

lib/router.php

@@ -73,6 +73,8 @@ class Router
 
         if (Event::handle('StartInitializeRouter', array(&$m))) {
 
+            $m->connect('robots.txt', array('action' => 'robotstxt'));
+
             $m->connect('opensearch/people', array('action' => 'opensearch',
                                                    'type' => 'people'));
             $m->connect('opensearch/notice', array('action' => 'opensearch',