Expand regex to match n param decrypt function

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

@@ -3,6 +3,7 @@
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
 import org.schabi.newpipe.extractor.utils.JavaScript;
 import org.schabi.newpipe.extractor.utils.Parser;
+import org.schabi.newpipe.extractor.utils.StringUtil;
 
 import javax.annotation.Nonnull;
 import java.util.HashMap;
@@ -33,7 +34,10 @@
  */
 public class YoutubeThrottlingDecrypter {
 
-    private static final String N_PARAM_REGEX = "[&?]n=([^&]+)";
+    private static final Pattern N_PARAM_PATTERN = Pattern.compile("[&?]n=([^&]+)");
+    private static final Pattern FUNCTION_NAME_PATTERN = Pattern.compile(
+            "b=a\\.get\\(\"n\"\\)\\)&&\\(b=(\\w+)\\(b\\),a\\.set\\(\"n\",b\\)");
+
     private static final Map<String, String> nParams = new HashMap<>();
 
     private final String functionName;
@@ -62,15 +66,26 @@ public YoutubeThrottlingDecrypter() throws ParsingException {
 
     private String parseDecodeFunctionName(final String playerJsCode)
             throws Parser.RegexException {
-        Pattern pattern = Pattern.compile(
-                "b=a\\.get\\(\"n\"\\)\\)&&\\(b=(\\w+)\\(b\\),a\\.set\\(\"n\",b\\)");
-        return Parser.matchGroup1(pattern, playerJsCode);
+        return Parser.matchGroup1(FUNCTION_NAME_PATTERN, playerJsCode);
     }
 
     @Nonnull
     private String parseDecodeFunction(final String playerJsCode, final String functionName)
             throws Parser.RegexException {
-        Pattern functionPattern = Pattern.compile(functionName + "=function(.*?;)\n",
+        try {
+            return parseWithParenthesisMatching(playerJsCode, functionName);
+        } catch (Exception e) {
+            return parseWithRegex(playerJsCode, functionName);
+        }
+    }
+
+    private String parseWithParenthesisMatching(final String playerJsCode, final String functionName) {
+        final String functionBase = functionName + "=function";
+        return functionBase + StringUtil.matchToClosingParenthesis(playerJsCode, functionBase) + ";";
+    }
+
+    private String parseWithRegex(final String playerJsCode, final String functionName) throws Parser.RegexException {
+        Pattern functionPattern = Pattern.compile(functionName + "=function(.*?}};)\n",
                 Pattern.DOTALL);
         return "function " + functionName + Parser.matchGroup1(functionPattern, playerJsCode);
     }
@@ -86,12 +101,11 @@ public String apply(final String url) throws Parser.RegexException {
     }
 
     private boolean containsNParam(final String url) {
-        return Parser.isMatch(N_PARAM_REGEX, url);
+        return Parser.isMatch(N_PARAM_PATTERN, url);
     }
 
     private String parseNParam(final String url) throws Parser.RegexException {
-        Pattern nValuePattern = Pattern.compile(N_PARAM_REGEX);
-        return Parser.matchGroup1(nValuePattern, url);
+        return Parser.matchGroup1(N_PARAM_PATTERN, url);
     }
 
     private String decryptNParam(final String nParam) {

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

@@ -84,6 +84,11 @@ public static boolean isMatch(String pattern, String input) {
         return mat.find();
     }
 
+    public static boolean isMatch(Pattern pattern, String input) {
+        Matcher mat = pattern.matcher(input);
+        return mat.find();
+    }
+
     public static Map<String, String> compatParseMap(final String input) throws UnsupportedEncodingException {
         Map<String, String> map = new HashMap<>();
         for (String arg : input.split("&")) {

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

@@ -0,0 +1,47 @@
+package org.schabi.newpipe.extractor.utils;
+
+import edu.umd.cs.findbugs.annotations.NonNull;
+
+public class StringUtil {
+
+    private StringUtil() {
+    }
+
+    /**
+     * @param string The string to search in
+     * @param start A string from which to start searching.
+     * @return A substring where each '{' matches a '}'
+     * @throws IndexOutOfBoundsException If {@ string} does not contain {@code start}
+     */
+    @NonNull
+    public static String matchToClosingParenthesis(@NonNull final String string, @NonNull final String start) {
+        int startIndex = string.indexOf(start);
+        if (startIndex < 0) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        startIndex += start.length();
+        int endIndex = startIndex;
+        while (string.charAt(endIndex) != '{') {
+            ++endIndex;
+        }
+        ++endIndex;
+
+        int openParenthesis = 1;
+        while (openParenthesis > 0) {
+            switch (string.charAt(endIndex)) {
+                case '{':
+                    ++openParenthesis;
+                    break;
+                case '}':
+                    --openParenthesis;
+                    break;
+                default:
+                    break;
+            }
+            ++endIndex;
+        }
+
+        return string.substring(startIndex, endIndex);
+    }
+}

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

@@ -2,6 +2,7 @@
 
 import org.junit.Before;
 import org.junit.Test;
+import org.mozilla.javascript.EvaluatorException;
 import org.schabi.newpipe.downloader.DownloaderTestImpl;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
@@ -11,6 +12,7 @@
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.fail;
 
 public class YoutubeThrottlingDecrypterTest {
 
@@ -19,6 +21,22 @@ public void setup() throws IOException {
         NewPipe.init(DownloaderTestImpl.getInstance());
     }
 
+    @Test
+    public void testExtractFunction__success() throws ParsingException {
+        String[] videoIds = {"jE1USQrs1rw", "CqxjzfudGAc", "goH-9MfQI7w", "KYIdr_7H5Yw", "J1WeqmGbYeI"};
+
+        final String encryptedUrl = "https://r6---sn-4g5ednek.googlevideo.com/videoplayback?expire=1626562120&ei=6AnzYO_YBpql1gLGkb_IBQ&ip=127.0.0.1&id=o-ANhBEf36Z5h-8U9DDddtPDqtS0ZNwf0XJAAigudKI2uI&itag=278&aitags=133%2C134%2C135%2C136%2C137%2C160%2C242%2C243%2C244%2C247%2C248%2C278&source=youtube&requiressl=yes&vprv=1&mime=video%2Fwebm&ns=TvecOReN0vPuXb3j_zq157IG&gir=yes&clen=2915100&dur=270.203&lmt=1608157174907785&keepalive=yes&fexp=24001373,24007246&c=WEB&txp=5535432&n=N9BWSTFT7vvBJrvQ&sparams=expire%2Cei%2Cip%2Cid%2Caitags%2Csource%2Crequiressl%2Cvprv%2Cmime%2Cns%2Cgir%2Cclen%2Cdur%2Clmt&alr=yes&sig=AOq0QJ8wRQIgW6XnUDKPDSxiT0_KE_tDDMpcaCJl2Un5p0Fu9qZNQGkCIQDWxsDHi_s2BEmRqIbd1C5g_gzfihB7RZLsScKWNMwzzA%3D%3D&cpn=9r2yt3BqcYmeb2Yu&cver=2.20210716.00.00&redirect_counter=1&cm2rm=sn-4g5ezy7s&cms_redirect=yes&mh=Y5&mm=34&mn=sn-4g5ednek&ms=ltu&mt=1626540524&mv=m&mvi=6&pl=43&lsparams=mh,mm,mn,ms,mv,mvi,pl&lsig=AG3C_xAwRQIhAIUzxTn9Vw1-vm-_7OQ5-0h1M6AZsY9Bx1FlCCTeMICzAiADtGggbn4Znsrh2EnvyOsGnYdRGcbxn4mW9JMOQiInDQ%3D%3D&range=259165-480735&rn=11&rbuf=20190";
+
+        for (String videoId : videoIds) {
+            try {
+                final String decryptedUrl = new YoutubeThrottlingDecrypter(videoId).apply(encryptedUrl);
+                assertNotEquals(encryptedUrl, decryptedUrl);
+            } catch (EvaluatorException e) {
+                fail("Failed to extract n param decrypt function for video " + videoId + "\n" + e);
+            }
+        }
+    }
+
     @Test
     public void testDecode__success() throws ParsingException {
         // URL extracted from browser with the dev tools