Make Facebook spout work again

In 2015, Facebook removed its feed support. Unfortunately,
it is no longer possible to access the site content
programmatically without registering an app.

This patch switches to the new API and adds fields for entering
the app credentials.

Closes: #687

spouts/facebook/page.php

@@ -2,15 +2,20 @@
 
 namespace spouts\facebook;
 
+use GuzzleHttp\Url;
+use helpers\WebClient;
+
 /**
  * Spout for fetching a facebook page feed
  *
- * @copyright  Copyright (c) Tobias Zeising (http://www.aditu.de)
- * @license    GPLv3 (https://www.gnu.org/licenses/gpl-3.0.html)
- * @author     Tobias Zeising <tobias.zeising@aditu.de>
- * @author     Thomas Muguet <t.muguet@thomasmuguet.info>
+ * https://developers.facebook.com/docs/graph-api/reference/v2.9/page/feed
+ *
+ * @copyright Copyright (c) Tobias Zeising (http://www.aditu.de)
+ * @license GPLv3 (https://www.gnu.org/licenses/gpl-3.0.html)
+ * @author Tobias Zeising <tobias.zeising@aditu.de>
+ * @author Jan Tojnar <jtojnar@gmail.com>
  */
-class page extends \spouts\rss\feed {
+class page extends \spouts\spout {
     /** @var string name of source */
     public $name = 'Facebook page feed';
 
@@ -45,41 +50,193 @@ class page extends \spouts\rss\feed {
             'default' => '',
             'required' => true,
             'validation' => ['notempty']
-        ]
+        ],
+        'app_id' => [
+            'title' => 'App ID',
+            'type' => 'text',
+            'default' => '',
+            'required' => true,
+            'validation' => ['notempty']
+        ],
+        'app_secret' => [
+            'title' => 'App Secret',
+            'type' => 'text',
+            'default' => '',
+            'required' => true,
+            'validation' => ['notempty']
+        ],
     ];
 
-    //
-    // Source Methods
-    //
+    /** @var ?string page picture */
+    private $pageLink;
+
+    /** @var ?string page picture */
+    private $pagePicture;
 
     /**
      * loads content for given source
-     * I supress all Warnings of SimplePie for ensuring
-     * working plugin in PHP Strict mode
      *
      * @param mixed $params the params of this source
      *
      * @return void
      */
     public function load($params) {
-        parent::load(['url' => $this->getXmlUrl($params)]);
+        $http = WebClient::getHttpClient();
+        $url = Url::fromString('https://graph.facebook.com/' . urlencode($params['user']));
+        $qs = $url->getQuery();
+        $qs['access_token'] = $params['app_id'] . '|' . $params['app_secret'];
+        $qs['fields'] = 'name,picture{url},link,feed{id,message,created_time,attachments,permalink_url}';
+        $data = $http->get($url)->json();
+
+        $this->spoutTitle = $data['name'];
+        $this->pagePicture = $data['picture']['data']['url'];
+        $this->pageLink = $data['picture']['link'];
+        $this->items = $data['feed']['data'];
+    }
+
+    public function getHtmlUrl() {
+        return $this->pageLink;
+    }
+
+    public function getId() {
+        if ($this->items !== false) {
+            $item = current($this->items);
+
+            return $item['id'];
+        }
+
+        return false;
+    }
+
+    public function getTitle() {
+        if ($this->items !== false) {
+            $item = current($this->items);
+
+            if (mb_strlen($item['message']) > 80) {
+                return mb_substr($item['message'], 0, 100) . '…';
+            } else {
+                return $item['message'];
+            }
+        }
+
+        return false;
+    }
+
+    public function getContent() {
+        if ($this->items !== false) {
+            $item = current($this->items);
+            $message = $item['message'];
+
+            if (isset($item['attachments']) && count($item['attachments']['data']) > 0) {
+                foreach ($item['attachments']['data'] as $media) {
+                    if ($media['type'] === 'photo') {
+                        $message .= '<figure>' . PHP_EOL;
+                        $message .= '<a href="' . $media['target']['url'] . '"><img src="' . $media['media']['image']['src'] . '" alt=""></a>' . PHP_EOL;
+
+                        // Some photos will have the same description, no need to display it twice
+                        if ($media['description'] !== $item['message']) {
+                            $message .= '<figcaption>' . $media['description'] . '</figcaption>' . PHP_EOL;
+                        }
+
+                        $message .= '</figure>' . PHP_EOL;
+                    }
+                }
+            }
+
+            return $message;
+        }
+
+        return false;
+    }
+
+    public function getIcon() {
+        return $this->pagePicture;
+    }
+
+    public function getLink() {
+        if ($this->items !== false) {
+            $item = current($this->items);
+
+            return $item['permalink_url'];
+        }
+
+        return false;
+    }
+
+    public function getDate() {
+        if ($this->items !== false) {
+            $item = current($this->items);
+
+            return $item['created_time'];
+        }
+
+        return false;
+    }
+
+    //
+    // Iterator Interface
+    //
+
+    /**
+     * reset iterator
+     *
+     * @return void
+     */
+    public function rewind() {
+        if ($this->items !== false) {
+            reset($this->items);
+        }
+    }
+
+    /**
+     * receive current item
+     *
+     * @return page current item
+     */
+    public function current() {
+        if ($this->items !== false) {
+            return $this;
+        }
+
+        return false;
     }
 
     /**
-     * returns the xml feed url for the source
+     * receive key of current item
      *
-     * @param mixed $params params for the source
+     * @return mixed key of current item
+     */
+    public function key() {
+        if ($this->items !== false) {
+            return key($this->items);
+        }
+
+        return false;
+    }
+
+    /**
+     * select next item
+     *
+     * @return page next item
+     */
+    public function next() {
+        if ($this->items !== false) {
+            next($this->items);
+        }
+
+        return $this;
+    }
+
+    /**
+     * end reached
      *
-     * @return string url as xml
+     * @return bool false if end reached
      */
-    public function getXmlUrl($params) {
-        $protocol = 'http://';
-        if (version_compare(PHP_VERSION, '5.3.0') >= 0 && defined('OPENSSL_VERSION_NUMBER')) {
-            $protocol = 'https://';
+    public function valid() {
+        if ($this->items !== false) {
+            return current($this->items) !== false;
         }
-        $content = @file_get_contents($protocol . 'graph.facebook.com/' . urlencode($params['user']));
-        $data = json_decode($content, true);
 
-        return $protocol . 'www.facebook.com/feeds/page.php?format=atom10&id=' . $data['id'];
+        return false;
     }
 }