Fix YouTubeChannelExtractor

It was given some inconsistent results (/user and /channel), now it only returns /channel urls don't matter what the original is (at least when calling the getCleanUrl() method).

src/main/java/org/schabi/newpipe/extractor/services/youtube/YoutubeChannelExtractor.java

@@ -59,7 +59,7 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
     public void fetchPage() throws IOException, ExtractionException {
         Downloader downloader = NewPipe.getDownloader();
 
-        String channelUrl = getCleanUrl() + CHANNEL_URL_PARAMETERS;
+        String channelUrl = super.getCleanUrl() + CHANNEL_URL_PARAMETERS;
         String pageContent = downloader.download(channelUrl);
         doc = Jsoup.parse(pageContent, channelUrl);
 
@@ -67,12 +67,24 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
         nextStreamsAjax = null;
     }
 
+    @Override
+    public String getCleanUrl() {
+        try {
+            return "https://www.youtube.com/channel/" + getId();
+        } catch (ParsingException e) {
+            return super.getCleanUrl();
+        }
+    }
+
     @Override
     public String getId() throws ParsingException {
         try {
-            return getUrlIdHandler().getId(getCleanUrl());
+            Element element = doc.getElementsByClass("yt-uix-subscription-button").first();
+            if (element == null) element = doc.getElementsByClass("yt-uix-subscription-preferences-button").first();
+
+            return element.attr("data-channel-external-id");
         } catch (Exception e) {
-            throw new ParsingException("Could not get channel id");
+            throw new ParsingException("Could not get channel id", e);
         }
     }
 
@@ -110,8 +122,7 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
     @Override
     public String getFeedUrl() throws ParsingException {
         try {
-            String channelId = doc.getElementsByClass("yt-uix-subscription-button").first().attr("data-channel-external-id");
+            return CHANNEL_FEED_BASE + getId();
-            return channelId == null ? "" : CHANNEL_FEED_BASE + channelId;
         } catch (Exception e) {
             throw new ParsingException("Could not get feed url", e);
         }

src/test/java/org/schabi/newpipe/extractor/services/youtube/YoutubeChannelExtractorTest.java

@@ -41,7 +41,7 @@ public class YoutubeChannelExtractorTest {
     public void setUp() throws Exception {
         NewPipe.init(Downloader.getInstance());
         extractor = YouTube.getService()
-                .getChannelExtractor("https://www.youtube.com/channel/UCYJ61XIK64sp6ZFFS8sctxw");
+                .getChannelExtractor("https://www.youtube.com/user/Gronkh");
     }
 
     @Test
@@ -54,6 +54,16 @@ public class YoutubeChannelExtractorTest {
         assertEquals(extractor.getName(), "Gronkh");
     }
 
+    @Test
+    public void testGetId() throws Exception {
+        assertEquals(extractor.getId(), "UCYJ61XIK64sp6ZFFS8sctxw");
+    }
+
+    @Test
+    public void testGetUrl() throws Exception {
+        assertEquals(extractor.getCleanUrl(), "https://www.youtube.com/channel/UCYJ61XIK64sp6ZFFS8sctxw");
+    }
+
     @Test
     public void testGetDescription() throws Exception {
         assertEquals(extractor.getDescription(), "★ ★ ★ KLICK MICH HART, DU SAU! :D ★ ★ ★ Zart im Schmelz und süffig im Abgang. Ungebremster Spieltrieb seit 1896. Tägliche Folgen nonstop seit dem 01.04.2010!...");
@@ -71,7 +81,7 @@ public class YoutubeChannelExtractorTest {
 
     @Test
     public void testGetFeedUrl() throws Exception {
-        assertTrue(extractor.getFeedUrl(), extractor.getFeedUrl().contains("feed"));
+        assertEquals(extractor.getFeedUrl(), "https://www.youtube.com/feeds/videos.xml?channel_id=UCYJ61XIK64sp6ZFFS8sctxw");
     }
 
     @Test