Fix SoundCloud channel tab pagination looping on empty pages

Author: that1potato

extractor/src/main/java/org/schabi/newpipe/extractor/services/soundcloud/extractors/SoundcloudChannelTabExtractor.java

@@ -14,6 +14,8 @@
 
 import javax.annotation.Nonnull;
 import java.io.IOException;
+import java.util.HashSet;
+import java.util.Set;
 
 import static org.schabi.newpipe.extractor.services.soundcloud.SoundcloudParsingHelper.SOUNDCLOUD_API_V2_URL;
 import static org.schabi.newpipe.extractor.utils.Utils.isNullOrEmpty;
@@ -22,6 +24,8 @@ public class SoundcloudChannelTabExtractor extends ChannelTabExtractor {
 
     private static final String USERS_ENDPOINT = SOUNDCLOUD_API_V2_URL + "users/";
 
+    private static final int MAX_EMPTY_PAGES = 5;
+
     private final String userId;
 
     public SoundcloudChannelTabExtractor(final StreamingService service,
@@ -70,9 +74,40 @@ public InfoItemsPage<InfoItem> getPage(final Page page)
         }
 
         final MultiInfoItemsCollector collector = new MultiInfoItemsCollector(getServiceId());
-        final String nextPageUrl = SoundcloudParsingHelper.getInfoItemsFromApi(
-                collector, page.getUrl());
+        final Set<String> visitedPages = new HashSet<>();
+
+        String currentPageUrl = page.getUrl();
+        String nextPageUrl = "";
+        int emptyPageCount = 0;
+
+        while (!isNullOrEmpty(currentPageUrl)) {
+            if (!visitedPages.add(currentPageUrl)) {
+                // Prevent infinite loops when the API points back to an already visited page.
+                nextPageUrl = "";
+                break;
+            }
+
+            final int itemsBefore = collector.getItems().size();
+            final String candidateNextPage = SoundcloudParsingHelper
+                    .getInfoItemsFromApi(collector, currentPageUrl);
+            final boolean hasNewItems = collector.getItems().size() > itemsBefore;
+
+            if (hasNewItems) {
+                nextPageUrl = candidateNextPage;
+                break;
+            }
+
+            emptyPageCount++;
+            if (emptyPageCount >= MAX_EMPTY_PAGES || isNullOrEmpty(candidateNextPage)) {
+                // Give up after too many empty responses or when SoundCloud stops providing tokens.
+                nextPageUrl = "";
+                break;
+            }
+
+            currentPageUrl = candidateNextPage;
+        }
 
-        return new InfoItemsPage<>(collector, new Page(nextPageUrl));
+        final Page nextPage = isNullOrEmpty(nextPageUrl) ? null : new Page(nextPageUrl);
+        return new InfoItemsPage<>(collector, nextPage);
     }
 }