-Fixed subtitles extraction to use method from youtube-dl.

-Expose subtitles during extraction.
-Make subtitle lists return nonnull empty collections instead of null.

src/main/java/org/schabi/newpipe/extractor/Subtitles.java

@@ -2,7 +2,9 @@ package org.schabi.newpipe.extractor;
 
 import org.schabi.newpipe.extractor.stream.SubtitlesFormat;
 
-public class Subtitles {
+import java.io.Serializable;
+
+public class Subtitles implements Serializable {
     private final SubtitlesFormat format;
     private final String languageCode;
     private final String URL;

src/main/java/org/schabi/newpipe/extractor/services/soundcloud/SoundcloudStreamExtractor.java

@@ -167,15 +167,15 @@ public class SoundcloudStreamExtractor extends StreamExtractor {
     }
 
     @Override
-    @Nullable
+    @Nonnull
     public List<Subtitles> getSubtitlesDefault() throws IOException, ExtractionException {
-        return null;
+        return Collections.emptyList();
     }
 
     @Override
-    @Nullable
+    @Nonnull
     public List<Subtitles> getSubtitles(SubtitlesFormat format) throws IOException, ExtractionException {
-        return null;
+        return Collections.emptyList();
     }
 
     @Override

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

@@ -7,6 +7,7 @@ import com.grack.nanojson.JsonParserException;
 import org.jsoup.Jsoup;
 import org.jsoup.nodes.Document;
 import org.jsoup.nodes.Element;
+import org.jsoup.select.Elements;
 import org.mozilla.javascript.Context;
 import org.mozilla.javascript.Function;
 import org.mozilla.javascript.ScriptableObject;
@@ -26,8 +27,6 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.io.IOException;
 import java.util.*;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 /*
  * Created by Christian Schabesberger on 06.08.15.
@@ -74,6 +73,12 @@ public class YoutubeStreamExtractor extends StreamExtractor {
         }
     }
 
+    public class SubtitlesException extends ContentNotAvailableException {
+        SubtitlesException(String message, Throwable cause) {
+            super(message, cause);
+        }
+    }
+
     /*//////////////////////////////////////////////////////////////////////////*/
 
     private Document doc;
@@ -81,6 +86,8 @@ public class YoutubeStreamExtractor extends StreamExtractor {
     private JsonObject playerArgs;
     @Nonnull
     private final Map<String, String> videoInfoPage = new HashMap<>();
+    @Nonnull
+    private List<Subtitles> availableSubtitles = new ArrayList<>();
 
     private boolean isAgeRestricted;
 
@@ -419,54 +426,20 @@ public class YoutubeStreamExtractor extends StreamExtractor {
     }
 
     @Override
-    @Nullable
+    @Nonnull
     public List<Subtitles> getSubtitlesDefault() throws IOException, ExtractionException {
-        return getSubtitles(SubtitlesFormat.TTML);
+        return getSubtitles(SubtitlesFormat.VTT);
     }
 
     @Override
-    @Nullable
+    @Nonnull
     public List<Subtitles> getSubtitles(SubtitlesFormat format) throws IOException, ExtractionException {
         assertPageFetched();
-        if(isAgeRestricted) {
+        List<Subtitles> subtitles = new ArrayList<>();
-            // If the video is age restricted getPlayerConfig will fail
+        for (final Subtitles subtitle : availableSubtitles) {
-            return null;
+            if (subtitle.getFileType() == format) subtitles.add(subtitle);
         }
-        // TODO: This should be done in onFetchPage()
+        return subtitles;
-        JsonObject playerConfig = getPlayerConfig(getPageHtml(NewPipe.getDownloader()));
-        String playerResponse = playerConfig.getObject("args").getString("player_response");
-
-        JsonObject captions;
-        try {
-            // Captions does not exist, return null
-            if (!JsonParser.object().from(playerResponse).has("captions")) return null;
-
-            captions = JsonParser.object().from(playerResponse).getObject("captions");
-        } catch (JsonParserException e) {
-            // Failed to parse subtitles
-            return null;
-        }
-        JsonArray captionsArray = captions.getObject("playerCaptionsTracklistRenderer").getArray("captionTracks");
-
-        int captionsSize = captionsArray.size();
-        // Should not happen, if there is the "captions" object, it should always has some captions in it
-        if(captionsSize == 0) return null;
-
-        List<Subtitles> result = new ArrayList<>();
-        for (int x = 0; x < captionsSize; x++) {
-            String baseUrl = captionsArray.getObject(x).getString("baseUrl");
-
-            String extension = format.getExtension();
-
-            String URL = baseUrl.replaceAll("&fmt=[^&]*", "&fmt=" + extension);
-            String captionsLangCode = captionsArray.getObject(x).getString("vssId");
-            boolean isAutoGenerated = captionsLangCode.startsWith("a.");
-            String languageCode = captionsLangCode.replaceFirst((isAutoGenerated) ? "a." : ".", "");
-
-            result.add(new Subtitles(format, languageCode, URL, isAutoGenerated));
-        }
-
-        return result;
     }
 
     @Override
@@ -580,6 +553,10 @@ public class YoutubeStreamExtractor extends StreamExtractor {
         if (decryptionCode.isEmpty()) {
             decryptionCode = loadDecryptionCode(playerUrl);
         }
+
+        if (availableSubtitles.isEmpty()) {
+            availableSubtitles.addAll(getAvailableSubtitles(getId()));
+        }
     }
 
     private JsonObject getPlayerConfig(String pageContent) throws ParsingException {
@@ -732,6 +709,25 @@ public class YoutubeStreamExtractor extends StreamExtractor {
         return result == null ? "" : result.toString();
     }
 
+    private List<Subtitles> getAvailableSubtitles(final String id) throws SubtitlesException {
+        try {
+            final String listingUrl = getVideoSubtitlesListingUrl(id);
+            final String pageContent = NewPipe.getDownloader().download(listingUrl);
+            final Document listing = Jsoup.parse(pageContent, listingUrl);
+            final Elements tracks = listing.select("track");
+
+            List<Subtitles> subtitles = new ArrayList<>(tracks.size() * 5);
+            for (final Element track : tracks) {
+                final String languageCode = track.attr("lang_code");
+                subtitles.add(getVideoSubtitlesUrl(id, languageCode, SubtitlesFormat.TTML));
+                subtitles.add(getVideoSubtitlesUrl(id, languageCode, SubtitlesFormat.VTT));
+                // todo: add transcripts, they are currently omitted since they are incompatible with ExoPlayer
+            }
+            return subtitles;
+        } catch (IOException | ReCaptchaException e) {
+            throw new SubtitlesException("Unable to download subtitles listing", e);
+        }
+    }
     /*//////////////////////////////////////////////////////////////////////////
     // Data Class
     //////////////////////////////////////////////////////////////////////////*/
@@ -751,12 +747,25 @@ public class YoutubeStreamExtractor extends StreamExtractor {
     //////////////////////////////////////////////////////////////////////////*/
 
     @Nonnull
-    private String getVideoInfoUrl(final String id, final String sts) {
+    private static String getVideoInfoUrl(final String id, final String sts) {
         return "https://www.youtube.com/get_video_info?" + "video_id=" + id +
                 "&eurl=https://youtube.googleapis.com/v/" + id +
                 "&sts=" + sts + "&ps=default&gl=US&hl=en";
     }
 
+    @Nonnull
+    private static String getVideoSubtitlesListingUrl(final String id) {
+        return "https://video.google.com/timedtext?type=list&v=" + id;
+    }
+
+    @Nonnull
+    private static Subtitles getVideoSubtitlesUrl(final String id, final String locale, final SubtitlesFormat format) {
+        final String url = "https://www.youtube.com/api/timedtext?lang=" + locale +
+                "&fmt=" + format.getExtension() + "&name=&v=" + id;
+        // These are all non-generated
+        return new Subtitles(format, locale, url, false);
+    }
+
     private Map<String, ItagItem> getItags(String encodedUrlMapKey, ItagItem.ItagType itagTypeWanted) throws ParsingException {
         Map<String, ItagItem> urlAndItags = new LinkedHashMap<>();
 

src/main/java/org/schabi/newpipe/extractor/stream/StreamExtractor.java

@@ -132,10 +132,9 @@ public abstract class StreamExtractor extends Extractor {
     public abstract List<VideoStream> getVideoStreams() throws IOException, ExtractionException;
     public abstract List<VideoStream> getVideoOnlyStreams() throws IOException, ExtractionException;
 
-    @Nullable
+    @Nonnull
     public abstract List<Subtitles> getSubtitlesDefault() throws IOException, ExtractionException;
-
+    @Nonnull
-    @Nullable
     public abstract List<Subtitles> getSubtitles(SubtitlesFormat format) throws IOException, ExtractionException;
 
     public abstract StreamType getStreamType() throws ParsingException;

src/main/java/org/schabi/newpipe/extractor/stream/StreamInfo.java

@@ -138,6 +138,10 @@ public class StreamInfo extends Info {
         return start_position;
     }
 
+    public List<Subtitles> getSubtitles() {
+        return subtitles;
+    }
+
     public void setStreamType(StreamType stream_type) {
         this.stream_type = stream_type;
     }
@@ -214,6 +218,10 @@ public class StreamInfo extends Info {
         this.start_position = start_position;
     }
 
+    public void setSubtitles(List<Subtitles> subtitles) {
+        this.subtitles = subtitles;
+    }
+
     public static class StreamExtractException extends ExtractionException {
         StreamExtractException(String message) {
             super(message);
@@ -313,6 +321,12 @@ public class StreamInfo extends Info {
             streamInfo.addError(new ExtractionException("Couldn't get video only streams", e));
         }
 
+        try {
+            streamInfo.setSubtitles(extractor.getSubtitlesDefault());
+        } catch (Exception e) {
+            streamInfo.addError(new ExtractionException("Couldn't get subtitles", e));
+        }
+
         // Lists can be null if a exception was thrown during extraction
         if (streamInfo.getVideoStreams() == null) streamInfo.setVideoStreams(Collections.<VideoStream>emptyList());
         if (streamInfo.getVideoOnlyStreams()== null) streamInfo.setVideoOnlyStreams(Collections.<VideoStream>emptyList());
@@ -444,4 +458,6 @@ public class StreamInfo extends Info {
     public List<InfoItem> related_streams;
     //in seconds. some metadata is not passed using a StreamInfo object!
     public long start_position = 0;
+
+    public List<Subtitles> subtitles;
 }

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

@@ -3,7 +3,6 @@ package org.schabi.newpipe.extractor.services.youtube;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import org.schabi.newpipe.Downloader;
-import org.schabi.newpipe.extractor.ExtractorAsserts;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.exceptions.ExtractionException;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
@@ -148,12 +147,12 @@ public class YoutubeStreamExtractorDefaultTest {
     @Test
     public void testGetSubtitlesListDefault() throws IOException, ExtractionException {
         // Video (/view?v=YQHsXMglC9A) set in the setUp() method has no captions => null
-        assertTrue(extractor.getSubtitlesDefault() == null);
+        assertTrue(extractor.getSubtitlesDefault().isEmpty());
     }
 
     @Test
     public void testGetSubtitlesList() throws IOException, ExtractionException {
         // Video (/view?v=YQHsXMglC9A) set in the setUp() method has no captions => null
-        assertTrue(extractor.getSubtitles(SubtitlesFormat.VTT) == null);
+        assertTrue(extractor.getSubtitles(SubtitlesFormat.VTT).isEmpty());
     }
 }

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

@@ -122,12 +122,12 @@ public class YoutubeStreamExtractorRestrictedTest {
     @Test
     public void testGetSubtitlesListDefault() throws IOException, ExtractionException {
         // Video (/view?v=YQHsXMglC9A) set in the setUp() method has no captions => null
-        assertNull(extractor.getSubtitlesDefault());
+        assertTrue(extractor.getSubtitlesDefault().isEmpty());
     }
 
     @Test
     public void testGetSubtitlesList() throws IOException, ExtractionException {
         // Video (/view?v=YQHsXMglC9A) set in the setUp() method has no captions => null
-        assertNull(extractor.getSubtitles(SubtitlesFormat.VTT));
+        assertTrue(extractor.getSubtitles(SubtitlesFormat.VTT).isEmpty());
     }
 }