Add Really Simple Discovery (RSD) support

Anil Dash suggested that all implementers of the Twitter API include
support for the remedial RSD format. This commit adds an RSD action
that returns the API root and additional API data to help client
developers discover and use our Twitter-compatible API.

http://dashes.com/anil/2009/12/the-twitter-api-is-finished.html
http://tales.phrasewise.com/rfc/rsd

actions/public.php

@@ -137,6 +137,14 @@ class PublicAction extends Action
         parent::extraHead();
         $this->element('meta', array('http-equiv' => 'X-XRDS-Location',
                                            'content' => common_local_url('publicxrds')));
+
+        $rsd = common_local_url('rsd');
+
+        // RSD, http://tales.phrasewise.com/rfc/rsd
+
+        $this->element('link', array('rel' => 'EditURI',
+                                     'type' => 'application/rsd+xml',
+                                     'href' => $rsd));
     }
 
     /**

actions/rsd.php

@@ -0,0 +1,226 @@
+<?php
+/**
+ * StatusNet - the distributed open-source microblogging tool
+ * Copyright (C) 2008-2010, StatusNet, Inc.
+ *
+ * Really Simple Discovery (RSD) for API access
+ *
+ * PHP version 5
+ *
+ * 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 API
+ * @package  StatusNet
+ * @author   Evan Prodromou <evan@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl.html AGPLv3
+ * @link     http://status.net/
+ *
+ */
+
+if (!defined('STATUSNET')) {
+    exit(1);
+}
+
+/**
+ * RSD action class
+ *
+ * Really Simple Discovery (RSD) is a simple (to a fault, maybe)
+ * discovery tool for blog APIs.
+ *
+ * http://tales.phrasewise.com/rfc/rsd
+ *
+ * Anil Dash suggested that RSD be used for services that implement
+ * the Twitter API:
+ *
+ * http://dashes.com/anil/2009/12/the-twitter-api-is-finished.html
+ *
+ * It's in use now for WordPress.com blogs:
+ *
+ * http://matt.wordpress.com/xmlrpc.php?rsd
+ *
+ * I (evan@status.net) have tried to stay faithful to the premise of
+ * RSD, while adding information useful to StatusNet client developers.
+ * In particular:
+ *
+ * - There is a link from each user's profile page to their personal
+ *   RSD feed. A personal rsd.xml includes a 'blogID' element that is
+ *   their username.
+ * - There is a link from the public root to '/rsd.xml', a public RSD
+ *   feed. It's identical to the personal rsd except it doesn't include
+ *   a blogId.
+ * - I've added a setting to the API to indicate that OAuth support is
+ *   available.
+ *
+ * @category API
+ * @package  StatusNet
+ * @author   Evan Prodromou <evan@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl.html AGPLv3
+ * @link     http://status.net/
+ */
+
+class RsdAction extends Action
+{
+    /**
+     * Optional attribute for the personal rsd.xml file.
+     */
+
+    var $user = null;
+
+    /**
+     * Prepare the action for use.
+     *
+     * Check for a nickname; redirect if non-canonical; if
+     * not provided, assume public rsd.xml.
+     *
+     * @param array $args GET, POST, and URI arguments.
+     *
+     * @return boolean success flag
+     */
+
+    function prepare($args)
+    {
+        parent::prepare($args);
+
+        // optional argument
+
+        $nickname_arg = $this->arg('nickname');
+
+        if (empty($nickname_arg)) {
+            $this->user = null;
+        } else {
+            $nickname = common_canonical_nickname($nickname_arg);
+
+            // Permanent redirect on non-canonical nickname
+
+            if ($nickname_arg != $nickname) {
+                common_redirect(common_local_url('rsd',
+                                                 array('nickname' => $nickname)),
+                                301);
+                return false;
+            }
+
+            $this->user = User::staticGet('nickname', $nickname);
+
+            if (empty($this->user)) {
+                $this->clientError(_('No such user.'), 404);
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * Action handler.
+     *
+     * Outputs the XML format for an RSD file. May include
+     * personal information if this is a personal file
+     * (based on whether $user attribute is set).
+     *
+     * @param array $args array of arguments
+     *
+     * @return nothing
+     */
+
+    function handle($args)
+    {
+        header('Content-Type: application/rsd+xml');
+
+        $this->startXML();
+
+        $rsdNS = 'http://archipelago.phrasewise.com/rsd';
+        $this->elementStart('rsd', array('version' => '1.0',
+                                         'xmlns' => $rsdNS));
+        $this->elementStart('service');
+        $this->element('engineName', null, _('StatusNet'));
+        $this->element('engineLink', null, 'http://status.net/');
+        $this->elementStart('apis');
+        if (Event::handle('StartRsdListApis', array($this, $this->user))) {
+
+            $blogID   = (empty($this->user)) ? '' : $this->user->nickname;
+            $apiAttrs = array('name' => 'Twitter',
+                              'preferred' => 'true',
+                              'apiLink' => $this->_apiRoot(),
+                              'blogID' => $blogID);
+
+            $this->elementStart('api', $apiAttrs);
+            $this->elementStart('settings');
+            $this->element('docs', null,
+                           'http://status.net/wiki/TwitterCompatibleAPI');
+            $this->element('setting', array('name' => 'OAuth'),
+                           'true');
+            $this->elementEnd('settings');
+            $this->elementEnd('api');
+            Event::handle('EndRsdListApis', array($this, $this->user));
+        }
+        $this->elementEnd('apis');
+        $this->elementEnd('service');
+        $this->elementEnd('rsd');
+
+        $this->endXML();
+
+        return true;
+    }
+
+    /**
+     * Returns last-modified date for use in caching
+     *
+     * Per-user rsd.xml is dated to last change of user
+     * (in case of nickname change); public has no date.
+     *
+     * @return string date of last change of this page
+     */
+
+    function lastModified()
+    {
+        if (!empty($this->user)) {
+            return $this->user->modified;
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Flag to indicate if this action is read-only
+     *
+     * It is; it doesn't change the DB.
+     *
+     * @param array $args ignored
+     *
+     * @return boolean true
+     */
+
+    function isReadOnly($args)
+    {
+        return true;
+    }
+
+    /**
+     * Return current site's API root
+     *
+     * Varies based on URL parameters, like if fancy URLs are
+     * turned on.
+     *
+     * @return string API root URI for this site
+     */
+
+    private function _apiRoot()
+    {
+        if (common_config('site', 'fancy')) {
+            return common_path('api/', true);
+        } else {
+            return common_path('index.php/api/', true);
+        }
+    }
+}

actions/showstream.php

@@ -178,6 +178,15 @@ class ShowstreamAction extends ProfileAction
         $this->element('link', array('rel' => 'microsummary',
                                      'href' => common_local_url('microsummary',
                                                                 array('nickname' => $this->profile->nickname))));
+
+        $rsd = common_local_url('rsd',
+                                array('nickname' => $this->profile->nickname));
+
+        // RSD, http://tales.phrasewise.com/rfc/rsd
+        $this->element('link', array('rel' => 'EditURI',
+                                     'type' => 'application/rsd+xml',
+                                     'href' => $rsd));
+
     }
 
     function showProfile()

lib/router.php

@@ -708,6 +708,10 @@ class Router
                                   'nickname' => $nickname),
                             array('tag' => '[a-zA-Z0-9]+'));
 
+                $m->connect('rsd.xml',
+                            array('action' => 'rsd',
+                                  'nickname' => $nickname));
+
                 $m->connect('',
                             array('action' => 'showstream',
                                   'nickname' => $nickname));
@@ -722,6 +726,7 @@ class Router
                 $m->connect('featured', array('action' => 'featured'));
                 $m->connect('favorited/', array('action' => 'favorited'));
                 $m->connect('favorited', array('action' => 'favorited'));
+                $m->connect('rsd.xml', array('action' => 'rsd'));
 
                 foreach (array('subscriptions', 'subscribers',
                                'nudge', 'all', 'foaf', 'xrds',
@@ -769,6 +774,10 @@ class Router
                             array('nickname' => '[a-zA-Z0-9]{1,64}'),
                             array('tag' => '[a-zA-Z0-9]+'));
 
+                $m->connect(':nickname/rsd.xml',
+                            array('action' => 'rsd'),
+                            array('nickname' => '[a-zA-Z0-9]{1,64}'));
+
                 $m->connect(':nickname',
                             array('action' => 'showstream'),
                             array('nickname' => '[a-zA-Z0-9]{1,64}'));