[RadioRai] get "final" URLs

Without this, every item has an enclosure with the same basename and
different query parameters.
This is correct, but some podcast readers (gPodder) mess it up, writing
every download to the same file.

bridges/RadioRaiBridge.php

@@ -4,7 +4,7 @@ class RadioRaiBridge extends BridgeAbstract {
 	const MAINTAINER = 'boyska';
 	const NAME = 'Radio Rai';
 	const URI = 'https://www.raiplayradio.it';
-	const CACHE_TIMEOUT = 1; // 10min
+	const CACHE_TIMEOUT = 900; // 15min
 	const DESCRIPTION = 'Segui le trasmissioni radio rai con feed/podcast valido';
 	const PARAMETERS = array( array(
 		'txname' => array(
@@ -13,6 +13,20 @@ class RadioRaiBridge extends BridgeAbstract {
 		)
 	));
 
+    private function getFinalURL($url) {
+        $ch = curl_init($url);
+        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+        curl_setopt($ch, CURLOPT_NOBODY, true);
+        curl_setopt($ch, CURLOPT_HEADER, true);
+        $ret = curl_exec($ch);
+        if($ret === FALSE) {
+            return null;
+        }
+        $redirect = curl_getinfo($ch, CURLINFO_REDIRECT_URL);
+        if($redirect === false) return $url;
+        return $redirect;
+    }
+
 	public function collectData(){
 		$html = getSimpleHTMLDOM($this->getURI())
 			or returnServerError('No results for this query.');
@@ -27,7 +41,7 @@ class RadioRaiBridge extends BridgeAbstract {
             $item['author'] = $this->getInput('txname');
             $item['title'] = $title;
             $item['content'] = $episode->plaintext;
-            $item['enclosures'] = [ $audiourl ];
+            $item['enclosures'] = [ $this::getFinalURL($audiourl) ];
             $item['url'] = $this::URI . $episode->getAttribute('data-href');
 
             $this->items[] = $item;