Merge pull request #939 from TurtleArmyMc/fix/SoundcloudPlaylistExtractor_track_order

Fix SoundcloudPlaylistExtractor: tracks are in correct order

Author: TobiGr

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

@@ -1,13 +1,9 @@
 package org.schabi.newpipe.extractor.services.soundcloud.extractors;
 
-import static org.schabi.newpipe.extractor.services.soundcloud.SoundcloudParsingHelper.SOUNDCLOUD_API_V2_URL;
-import static org.schabi.newpipe.extractor.utils.Utils.isNullOrEmpty;
-
 import com.grack.nanojson.JsonArray;
 import com.grack.nanojson.JsonObject;
 import com.grack.nanojson.JsonParser;
 import com.grack.nanojson.JsonParserException;
-
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.Page;
 import org.schabi.newpipe.extractor.StreamingService;
@@ -20,11 +16,15 @@
 import org.schabi.newpipe.extractor.stream.StreamInfoItem;
 import org.schabi.newpipe.extractor.stream.StreamInfoItemsCollector;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Objects;
 
-import javax.annotation.Nonnull;
+import static org.schabi.newpipe.extractor.services.soundcloud.SoundcloudParsingHelper.SOUNDCLOUD_API_V2_URL;
+import static org.schabi.newpipe.extractor.utils.Utils.isNullOrEmpty;
 
 public class SoundcloudPlaylistExtractor extends PlaylistExtractor {
     private static final int STREAMS_PER_REQUESTED_PAGE = 15;
@@ -171,9 +171,26 @@ public InfoItemsPage<StreamInfoItem> getPage(final Page page) throws IOException
 
         try {
             final JsonArray tracks = JsonParser.array().from(response);
+            // Response may not contain tracks in the same order as currentIds.
+            // The streams are displayed in the order which is used in currentIds on SoundCloud.
+            final HashMap<Integer, JsonObject> idToTrack = new HashMap<>();
             for (final Object track : tracks) {
                 if (track instanceof JsonObject) {
-                    collector.commit(new SoundcloudStreamInfoItemExtractor((JsonObject) track));
+                    final JsonObject o = (JsonObject) track;
+                    idToTrack.put(o.getInt("id"), o);
+                }
+            }
+            for (final String strId : currentIds) {
+                final int id = Integer.parseInt(strId);
+                try {
+                    collector.commit(new SoundcloudStreamInfoItemExtractor(
+                        Objects.requireNonNull(
+                                idToTrack.get(id),
+                        "no track with id " + id + " in response"
+                        )
+                    ));
+                } catch (final NullPointerException e) {
+                    throw new ParsingException("Could not parse json response", e);
                 }
             }
         } catch (final JsonParserException e) {