Add comment replies.

Author: FireMasterK

extractor/src/main/java/org/schabi/newpipe/extractor/comments/CommentsInfoItemExtractor.java

@@ -1,6 +1,7 @@
 package org.schabi.newpipe.extractor.comments;
 
 import org.schabi.newpipe.extractor.InfoItemExtractor;
+import org.schabi.newpipe.extractor.Page;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
 import org.schabi.newpipe.extractor.localization.DateWrapper;
 import org.schabi.newpipe.extractor.services.youtube.extractors.YoutubeCommentsInfoItemExtractor;
@@ -107,4 +108,13 @@ default boolean isUploaderVerified() throws ParsingException {
     default int getStreamPosition() throws ParsingException {
         return CommentsInfoItem.NO_STREAM_POSITION;
     }
+
+    /**
+     * The continuation page which is used to get comment replies from.
+     * @return the continuation Page for the replies
+     */
+    @Nullable
+    default Page getReplies() throws ParsingException {
+        return null;
+    }
 }

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

@@ -3,6 +3,7 @@
 import com.grack.nanojson.JsonArray;
 import com.grack.nanojson.JsonObject;
 
+import org.schabi.newpipe.extractor.Page;
 import org.schabi.newpipe.extractor.comments.CommentsInfoItemExtractor;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
 import org.schabi.newpipe.extractor.localization.DateWrapper;
@@ -230,4 +231,14 @@ public String getUploaderUrl() throws ParsingException {
             return EMPTY_STRING;
         }
     }
+
+    @Override
+    public Page getReplies() throws ParsingException {
+        try {
+            final String id = JsonUtils.getString(JsonUtils.getArray(json, "replies.commentRepliesRenderer.contents").getObject(0), "continuationItemRenderer.continuationEndpoint.continuationCommand.token");
+            return new Page(url, id);
+        } catch (final Exception e) {
+            return null;
+        }
+    }
 }