[YouTube] Fix channel extraction when redirects are in the response

Some redirects were embed directly into the response as instructions
for the page, instead of the usual http redirects.

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

@@ -2,7 +2,6 @@ package org.schabi.newpipe.extractor.services.youtube.extractors;
 
 import com.grack.nanojson.JsonArray;
 import com.grack.nanojson.JsonObject;
-
 import org.schabi.newpipe.extractor.StreamingService;
 import org.schabi.newpipe.extractor.channel.ChannelExtractor;
 import org.schabi.newpipe.extractor.downloader.Downloader;
@@ -16,13 +15,11 @@ import org.schabi.newpipe.extractor.stream.StreamInfoItem;
 import org.schabi.newpipe.extractor.stream.StreamInfoItemsCollector;
 import org.schabi.newpipe.extractor.utils.Utils;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 
-import javax.annotation.Nonnull;
+import static org.schabi.newpipe.extractor.services.youtube.linkHandler.YoutubeParsingHelper.*;
-
+import static org.schabi.newpipe.extractor.utils.JsonUtils.*;
-import static org.schabi.newpipe.extractor.services.youtube.linkHandler.YoutubeParsingHelper.fixThumbnailUrl;
-import static org.schabi.newpipe.extractor.services.youtube.linkHandler.YoutubeParsingHelper.getJsonResponse;
-import static org.schabi.newpipe.extractor.services.youtube.linkHandler.YoutubeParsingHelper.getTextFromObject;
 
 /*
  * Created by Christian Schabesberger on 25.07.16.
@@ -55,9 +52,45 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
 
     @Override
     public void onFetchPage(@Nonnull Downloader downloader) throws IOException, ExtractionException {
-        final String url = super.getUrl() + "/videos?pbj=1&view=0&flow=grid";
+        String url = super.getUrl() + "/videos?pbj=1&view=0&flow=grid";
+        JsonArray ajaxJson = null;
+
+        int level = 0;
+        while (level < 3) {
+            final JsonArray jsonResponse = getJsonResponse(url, getExtractorLocalization());
+
+            final JsonObject endpoint = jsonResponse.getObject(1, EMPTY_OBJECT)
+                    .getObject("response", EMPTY_OBJECT).getArray("onResponseReceivedActions", EMPTY_ARRAY)
+                    .getObject(0, EMPTY_OBJECT).getObject("navigateAction", EMPTY_OBJECT)
+                    .getObject("endpoint", EMPTY_OBJECT);
+
+            final String webPageType = endpoint
+                    .getObject("commandMetadata", EMPTY_OBJECT)
+                    .getObject("webCommandMetadata", EMPTY_OBJECT)
+                    .getString("webPageType", EMPTY_STRING);
+
+            final String browseId = endpoint
+                    .getObject("browseEndpoint", EMPTY_OBJECT)
+                    .getString("browseId", EMPTY_STRING);
+
+            if (webPageType.equalsIgnoreCase("WEB_PAGE_TYPE_BROWSE") && !browseId.isEmpty()) {
+
+                if (!browseId.startsWith("UC")) {
+                    throw new ExtractionException("Redirected id is not pointing to a channel");
+                }
+
+                url = "https://www.youtube.com/channel/" + browseId + "/videos?pbj=1&view=0&flow=grid";
+                level++;
+            } else {
+                ajaxJson = jsonResponse;
+                break;
+            }
+        }
+
+        if (ajaxJson == null) {
+            throw new ExtractionException("Could not fetch initial JSON data");
+        }
 
-        final JsonArray ajaxJson = getJsonResponse(url, getExtractorLocalization());
         initialData = ajaxJson.getObject(1).getObject("response");
         YoutubeParsingHelper.defaultAlertsCheck(initialData);
     }

extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/extractors/YoutubeStreamExtractor.java

@@ -621,7 +621,7 @@ public class YoutubeStreamExtractor extends StreamExtractor {
 
         playerResponse = getPlayerResponse();
 
-        final JsonObject playabilityStatus = playerResponse.getObject("playabilityStatus", JsonUtils.DEFAULT_EMPTY);
+        final JsonObject playabilityStatus = playerResponse.getObject("playabilityStatus", JsonUtils.EMPTY_OBJECT);
         final String status = playabilityStatus.getString("status");
         // If status exist, and is not "OK", throw a ContentNotAvailableException with the reason.
         if (status != null && !status.toLowerCase().equals("ok")) {

extractor/src/main/java/org/schabi/newpipe/extractor/utils/JsonUtils.java

@@ -11,7 +11,9 @@ import java.util.Arrays;
 import java.util.List;
 
 public class JsonUtils {
-    public static final JsonObject DEFAULT_EMPTY = new JsonObject();
+    public static final JsonObject EMPTY_OBJECT = new JsonObject();
+    public static final JsonArray EMPTY_ARRAY = new JsonArray();
+    public static final String EMPTY_STRING = "";
 
     private JsonUtils() {
     }

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

@@ -5,12 +5,16 @@ import org.junit.Test;
 import org.schabi.newpipe.DownloaderTestImpl;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.channel.ChannelExtractor;
+import org.schabi.newpipe.extractor.channel.ChannelInfo;
 import org.schabi.newpipe.extractor.exceptions.ContentNotAvailableException;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
 import org.schabi.newpipe.extractor.services.BaseChannelExtractorTest;
 import org.schabi.newpipe.extractor.services.youtube.extractors.YoutubeChannelExtractor;
 
+import java.util.List;
+
 import static org.junit.Assert.*;
+import static org.schabi.newpipe.extractor.ExtractorAsserts.assertEmpty;
 import static org.schabi.newpipe.extractor.ExtractorAsserts.assertIsSecureUrl;
 import static org.schabi.newpipe.extractor.ServiceList.YouTube;
 import static org.schabi.newpipe.extractor.services.DefaultTests.*;
@@ -505,6 +509,97 @@ public class YoutubeChannelExtractorTest {
         }
     }
 
+    /**
+     * Some VEVO channels will redirect to a new page with a new channel id.
+     * <p>
+     * Though, it isn't a simple redirect, but a redirect instruction embed in the response itself, this
+     * test assure that we account for that.
+     */
+    public static class RedirectedChannel implements BaseChannelExtractorTest {
+        private static YoutubeChannelExtractor extractor;
+
+        @BeforeClass
+        public static void setUp() throws Exception {
+            NewPipe.init(DownloaderTestImpl.getInstance());
+            extractor = (YoutubeChannelExtractor) YouTube
+                    .getChannelExtractor("https://www.youtube.com/channel/UCITk7Ky4iE5_xISw9IaHqpQ");
+            extractor.fetchPage();
+        }
+
+        /*//////////////////////////////////////////////////////////////////////////
+        // Extractor
+        //////////////////////////////////////////////////////////////////////////*/
+
+        @Test
+        public void testServiceId() {
+            assertEquals(YouTube.getServiceId(), extractor.getServiceId());
+        }
+
+        @Test
+        public void testName() throws Exception {
+            assertEquals("LordiVEVO", extractor.getName());
+        }
+
+        @Test
+        public void testId() throws Exception {
+            assertEquals("UCrxkwepj7-4Wz1wHyfzw-sQ", extractor.getId());
+        }
+
+        @Test
+        public void testUrl() throws ParsingException {
+            assertEquals("https://www.youtube.com/channel/UCrxkwepj7-4Wz1wHyfzw-sQ", extractor.getUrl());
+        }
+
+        @Test
+        public void testOriginalUrl() throws ParsingException {
+            assertEquals("https://www.youtube.com/channel/UCITk7Ky4iE5_xISw9IaHqpQ", extractor.getOriginalUrl());
+        }
+
+        /*//////////////////////////////////////////////////////////////////////////
+        // ListExtractor
+        //////////////////////////////////////////////////////////////////////////*/
+
+        @Test
+        public void testRelatedItems() throws Exception {
+            defaultTestRelatedItems(extractor);
+        }
+
+        @Test
+        public void testMoreRelatedItems() throws Exception {
+            assertNoMoreItems(extractor);
+        }
+
+         /*//////////////////////////////////////////////////////////////////////////
+         // ChannelExtractor
+         //////////////////////////////////////////////////////////////////////////*/
+
+        @Test
+        public void testDescription() throws Exception {
+            assertEmpty(extractor.getDescription());
+        }
+
+        @Test
+        public void testAvatarUrl() throws Exception {
+            String avatarUrl = extractor.getAvatarUrl();
+            assertIsSecureUrl(avatarUrl);
+            assertTrue(avatarUrl, avatarUrl.contains("yt3"));
+        }
+
+        @Test
+        public void testBannerUrl() throws Exception {
+            assertEmpty(extractor.getBannerUrl());
+        }
+
+        @Test
+        public void testFeedUrl() throws Exception {
+            assertEquals("https://www.youtube.com/feeds/videos.xml?channel_id=UCrxkwepj7-4Wz1wHyfzw-sQ", extractor.getFeedUrl());
+        }
+
+        @Test
+        public void testSubscriberCount() throws Exception {
+            assertEquals(-1, extractor.getSubscriberCount());
+        }
+    }
 
     public static class RandomChannel implements BaseChannelExtractorTest {
         private static YoutubeChannelExtractor extractor;