parseAlbumInfo(): handle relative track urls

lib/parser.js

@@ -181,10 +181,14 @@ function parseAlbumInfo(html, opts) {
                 return file;
             }
             basic.track.itemListElement.forEach( track => {
+                let trackUrl = track.item.url;
+                if (!utils.isAbsoluteUrl(trackUrl)) {
+                    trackUrl = utils.getUrl(trackUrl, album.url);
+                }
                 album.tracks.push({
                     position: track.position,
                     name: track.item.name,
-                    url: track.item.url,
+                    url: trackUrl,
                     duration: track.item.duration_secs,
                     streamUrl: _getStreamUrl(track.item.url)
                 });

lib/utils.js

@@ -108,6 +108,11 @@ function stripMultipleWhitespaces(str) {
     return str.replace(/\s+/g, ' ');
 }
 
+function isAbsoluteUrl(url) {
+    const isAbsolute = new RegExp('^([a-z]+://|//)', 'i');
+    return isAbsolute.test(url);
+}
+
 module.exports = { 
     getUrl,
     getSiteUrl,
@@ -120,5 +125,6 @@ module.exports = {
     substrBefore,
     splitUrl,
     getSearchUrl,
-    stripMultipleWhitespaces
+    stripMultipleWhitespaces,
+    isAbsoluteUrl
 };