[YouTube] Convert signature timestamp to integer

The signature timestamp is used as a number by HTML5 clients, so it should be
used in the same way by the extractor too instead of being a string.

As the timestamp doesn't seem to exceed 5 digits, an integer is used to store
its value.

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

@@ -33,7 +33,7 @@ public final class YoutubeJavaScriptPlayerManager {
     private static String cachedJavaScriptPlayerCode;
 
     @Nullable
-    private static String cachedSignatureTimestamp;
+    private static Integer cachedSignatureTimestamp;
     @Nullable
     private static String cachedSignatureDeobfuscationFunction;
     @Nullable
@@ -76,7 +76,7 @@ public final class YoutubeJavaScriptPlayerManager {
      * signature timestamp failed
      */
     @Nonnull
-    public static String getSignatureTimestamp(@Nonnull final String videoId)
+    public static Integer getSignatureTimestamp(@Nonnull final String videoId)
             throws ParsingException {
         // Return the cached result if it is present
         if (cachedSignatureTimestamp != null) {
@@ -93,12 +93,15 @@ public final class YoutubeJavaScriptPlayerManager {
         extractJavaScriptCodeIfNeeded(videoId);
 
         try {
-            cachedSignatureTimestamp = YoutubeSignatureUtils.getSignatureTimestamp(
+            cachedSignatureTimestamp = Integer.valueOf(
-                    cachedJavaScriptPlayerCode);
+                    YoutubeSignatureUtils.getSignatureTimestamp(cachedJavaScriptPlayerCode));
         } catch (final ParsingException e) {
             // Store the exception for future calls of this method, in order to improve performance
             sigTimestampExtractionEx = e;
             throw e;
+        } catch (final NumberFormatException e) {
+            sigTimestampExtractionEx =
+                    new ParsingException("Could not convert signature timestamp to a number", e);
         }
 
         return cachedSignatureTimestamp;

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

@@ -1419,7 +1419,7 @@ public final class YoutubeParsingHelper {
             @Nonnull final Localization localization,
             @Nonnull final ContentCountry contentCountry,
             @Nonnull final String videoId,
-            @Nonnull final String sts,
+            @Nonnull final Integer sts,
             final boolean isTvHtml5DesktopJsonBuilder,
             @Nonnull final String contentPlaybackNonce) throws IOException, ExtractionException {
         // @formatter:off