[YouTube] Optimize extracting auto-translated captions

Faster and ordered: captions provided by the user are at the beginning of the list, auto-translated captions are at the end

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

@@ -670,18 +670,35 @@ public class YoutubeStreamExtractor extends StreamExtractor {
         assertPageFetched();
 
         // We cannot store the subtitles list because the media format may change
-        final List<SubtitlesStream> subtitlesToReturn = new ArrayList<>();
+        final List<SubtitlesStream> subtitles = new ArrayList<>();
+        final List<SubtitlesStream> autoTranslatedSubtitles = new ArrayList<>();
         final JsonObject renderer = playerResponse.getObject("captions")
                 .getObject("playerCaptionsTracklistRenderer");
         final JsonArray captionsArray = renderer.getArray("captionTracks");
 
+        // Generate list of languages available for auto-translations
+        final List<String> translationLanguages;
+        if (renderer.has("translationLanguages")) {
+            translationLanguages = renderer.getArray("translationLanguages")
+                    .stream()
+                    .map(JsonObject.class::cast)
+                    .map(lang -> lang.getString("languageCode"))
+                    .collect(Collectors.toList());
+        } else {
+            translationLanguages = Collections.emptyList();
+        }
+
+        // Add subtitles
         for (int i = 0; i < captionsArray.size(); i++) {
             final JsonObject caption = captionsArray.getObject(i);
             final String languageCode = caption.getString("languageCode");
             final String baseUrl = caption.getString("baseUrl");
             final String vssId = caption.getString("vssId");
 
-            if (languageCode != null && baseUrl != null && vssId != null) {
+            if (languageCode == null || baseUrl == null || vssId == null) {
+                continue;
+            }
+
             final boolean isAutoGenerated = vssId.startsWith("a.");
             final String cleanUrl = baseUrl
                     // Remove preexisting format if exists
@@ -689,33 +706,36 @@ public class YoutubeStreamExtractor extends StreamExtractor {
                     // Remove translation language
                     .replaceAll("&tlang=[^&]*", "");
 
-                subtitlesToReturn.add(new SubtitlesStream.Builder()
+            // add base subtitles
+            subtitles.add(new SubtitlesStream.Builder()
                     .setContent(cleanUrl + "&fmt=" + format.getSuffix(), true)
                     .setMediaFormat(format)
                     .setLanguageCode(languageCode)
                     .setAutoGenerated(isAutoGenerated)
                     .setAutoTranslated(false)
                     .build());
-                if (i == 0 && caption.getBoolean("isTranslatable")
-                        && renderer.has("translationLanguages")) {
-                    final JsonArray languages = renderer.getArray("translationLanguages");
-                    for (int j = 0; j < languages.size(); j++) {
-                        final JsonObject lang = languages.getObject(j);
-                        final String tLanguageCode = lang.getString("languageCode");
-                        subtitlesToReturn.add(new SubtitlesStream.Builder()
+
+            // add auto-translations of this subtitle if available
+            if (caption.getBoolean("isTranslatable")) {
+                for (final String tLanguageCode : translationLanguages) {
+                    autoTranslatedSubtitles.add(new SubtitlesStream.Builder()
                             .setContent(cleanUrl + "&fmt=" + format.getSuffix()
                                     + "&tlang=" + tLanguageCode, true)
                             .setMediaFormat(format)
                             .setLanguageCode(tLanguageCode)
-                                .setAutoGenerated(isAutoGenerated)
+                            .setAutoGenerated(true)
                             .setAutoTranslated(true)
+                            .setBaseLanguageCode(languageCode)
                             .build());
                 }
             }
-            }
+
         }
 
-        return subtitlesToReturn;
+        // add auto-translations at the end for better sorting
+        subtitles.addAll(autoTranslatedSubtitles);
+
+        return subtitles;
     }
 
     @Override

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

@@ -12,6 +12,8 @@ import javax.annotation.Nullable;
 
 public final class SubtitlesStream extends Stream {
     private final MediaFormat format;
+    @Nullable
+    private final Locale baseLocale;
     private final Locale locale;
     private final boolean autoGenerated;
     private final boolean autoTranslated;
@@ -31,6 +33,8 @@ public final class SubtitlesStream extends Stream {
         @Nullable
         private String manifestUrl;
         private String languageCode;
+        @Nullable
+        private String baseLanguageCode;
         // Use of the Boolean class instead of the primitive type needed for setter call check
         private Boolean autoGenerated;
         private Boolean autoTranslated;
@@ -142,6 +146,18 @@ public final class SubtitlesStream extends Stream {
             return this;
         }
 
+        /**
+         * Set the language code of the base language used to auto-translate
+         * the {@link SubtitlesStream} to the current language code.
+         *
+         * @param baseLanguageCode the language code of the {@link SubtitlesStream}
+         * @return this {@link Builder} instance
+         */
+        public Builder setBaseLanguageCode(@Nullable final String baseLanguageCode) {
+            this.baseLanguageCode = baseLanguageCode;
+            return this;
+        }
+
         /**
          * Set whether the subtitles have been auto-generated by the streaming service.
          *
@@ -222,7 +238,7 @@ public final class SubtitlesStream extends Stream {
             }
 
             return new SubtitlesStream(id, content, isUrl, mediaFormat, deliveryMethod,
-                    languageCode, autoGenerated, autoTranslated, manifestUrl);
+                    languageCode, autoGenerated, autoTranslated, baseLanguageCode, manifestUrl);
         }
     }
 
@@ -240,6 +256,9 @@ public final class SubtitlesStream extends Stream {
      * @param languageCode     the language code of the stream
      * @param autoGenerated    whether the subtitles are auto-generated by the streaming service
      * @param autoTranslated   whether the subtitles are auto-translated by the streaming service
+     * @param baseLanguageCode the language code of the base language used to translate
+     *                         the subtitles to the current language
+     *                         or null if the subtitles are not auto-translated
      * @param manifestUrl      the URL of the manifest this stream comes from (if applicable,
      *                         otherwise null)
      */
@@ -252,6 +271,7 @@ public final class SubtitlesStream extends Stream {
                             @Nonnull final String languageCode,
                             final boolean autoGenerated,
                             final boolean autoTranslated,
+                            @Nullable final String baseLanguageCode,
                             @Nullable final String manifestUrl) throws ParsingException {
         super(id, content, isUrl, mediaFormat, deliveryMethod, manifestUrl);
         this.locale = LocaleCompat.forLanguageTag(languageCode).orElseThrow(
@@ -261,6 +281,13 @@ public final class SubtitlesStream extends Stream {
         this.format = mediaFormat;
         this.autoGenerated = autoGenerated;
         this.autoTranslated = autoTranslated;
+        if (baseLanguageCode == null) {
+            this.baseLocale = null;
+        } else {
+            this.baseLocale = LocaleCompat.forLanguageTag(baseLanguageCode).orElseThrow(
+                    () -> new ParsingException(
+                            "not a valid locale language code: " + baseLanguageCode));
+        }
     }
 
     /**
@@ -337,6 +364,37 @@ public final class SubtitlesStream extends Stream {
         return locale;
     }
 
+    /**
+     * Get the {@link Locale baseLocale} which was used to automatically translated the subtitles
+     * into the current {@link #locale}.
+     *
+     * @return the {@link Locale baseLocale} for the subtitle translation
+     * or {@code null} if the subtitle is not auto-translated
+     */
+    @Nullable
+    public Locale getBaseLocale() {
+        return baseLocale;
+    }
+
+    /**
+     * Get the display base language name of the subtitles.
+     *
+     * @return the display language name of the subtitles
+     */
+    public String getDisplayBaseLanguageName() {
+        return locale.getDisplayName(locale);
+    }
+
+    /**
+     * Get the language tag of the subtitles.
+     *
+     * @return the language tag of the subtitles
+     */
+    public String getBaseLanguageTag() {
+        return code;
+    }
+
+
     /**
      * No subtitles which are currently extracted use an {@link ItagItem}, so {@code null} is
      * returned by this method.
@@ -348,4 +406,16 @@ public final class SubtitlesStream extends Stream {
     public ItagItem getItagItem() {
         return null;
     }
+
+    @Override
+    public String toString() {
+        return "SubtitlesStream{"
+                + "format=" + format
+                + ", baseLocale=" + baseLocale
+                + ", locale=" + locale
+                + ", autoGenerated=" + autoGenerated
+                + ", autoTranslated=" + autoTranslated
+                + ", code='" + code + '\''
+                + '}';
+    }
 }

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

@@ -1,5 +1,6 @@
 package org.schabi.newpipe.extractor.utils;
 
+import javax.annotation.Nonnull;
 import java.util.Locale;
 import java.util.Optional;
 
@@ -16,7 +17,7 @@ public final class LocaleCompat {
 
     // Source: The AndroidX LocaleListCompat class's private forLanguageTagCompat() method.
     // Use Locale.forLanguageTag() on Android API level >= 21 / Java instead.
-    public static Optional<Locale> forLanguageTag(final String str) {
+    public static Optional<Locale> forLanguageTag(@Nonnull final String str) {
         if (str.contains("-")) {
             final String[] args = str.split("-", -1);
             if (args.length > 2) {