fix(youtube/return-youtube-dislike): don't block the UI thread (#221)

Co-authored-by: LisousEinaiKyrios <user@host>
Co-authored-by: oSumAtrIX <johan.melkonyan1@web.de>

app/src/main/java/app/revanced/integrations/returnyoutubedislike/Registration.java

@@ -1,103 +0,0 @@
-package app.revanced.integrations.returnyoutubedislike;
-
-
-import android.util.Base64;
-
-import java.security.MessageDigest;
-import java.security.SecureRandom;
-
-import app.revanced.integrations.settings.SettingsEnum;
-import app.revanced.integrations.utils.LogHelper;
-import app.revanced.integrations.returnyoutubedislike.requests.ReturnYouTubeDislikeApi;
-
-public class Registration {
-
-    // https://stackoverflow.com/a/157202
-    private final String AB = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
-    private SecureRandom rnd = new SecureRandom();
-    private String userId;
-
-    public String getUserId() {
-        return userId != null ? userId : fetchUserId();
-    }
-
-    public void saveUserId(String userId) {
-        SettingsEnum.RYD_USER_ID.saveValue(userId);
-    }
-
-    public static String solvePuzzle(String challenge, int difficulty) {
-        byte[] decodedChallenge = Base64.decode(challenge, Base64.NO_WRAP);
-
-        byte[] buffer = new byte[20];
-        for (int i = 4; i < 20; i++) {
-            buffer[i] = decodedChallenge[i - 4];
-        }
-
-        try {
-            int maxCount = (int) (Math.pow(2, difficulty + 1) * 5);
-            MessageDigest md = MessageDigest.getInstance("SHA-512");
-            for (int i = 0; i < maxCount; i++) {
-                buffer[0] = (byte) i;
-                buffer[1] = (byte) (i >> 8);
-                buffer[2] = (byte) (i >> 16);
-                buffer[3] = (byte) (i >> 24);
-                byte[] messageDigest = md.digest(buffer);
-
-                if (countLeadingZeroes(messageDigest) >= difficulty) {
-                    String encode = Base64.encodeToString(new byte[]{buffer[0], buffer[1], buffer[2], buffer[3]}, Base64.NO_WRAP);
-                    return encode;
-                }
-            }
-        } catch (Exception ex) {
-            LogHelper.printException(Registration.class, "Failed to solve puzzle", ex);
-        }
-
-        return null;
-    }
-
-    private String register() {
-        String userId = randomString(36);
-        LogHelper.debug(Registration.class, "Trying to register the following userId: " + userId);
-        return ReturnYouTubeDislikeApi.register(userId, this);
-    }
-
-    private String randomString(int len) {
-        StringBuilder sb = new StringBuilder(len);
-        for (int i = 0; i < len; i++)
-            sb.append(AB.charAt(rnd.nextInt(AB.length())));
-        return sb.toString();
-    }
-
-    private String fetchUserId() {
-        this.userId = SettingsEnum.RYD_USER_ID.getString();
-        if (this.userId == null) {
-            this.userId = register();
-        }
-
-        return this.userId;
-    }
-
-    private static int countLeadingZeroes(byte[] uInt8View) {
-        int zeroes = 0;
-        int value = 0;
-        for (int i = 0; i < uInt8View.length; i++) {
-            value = uInt8View[i] & 0xFF;
-            if (value == 0) {
-                zeroes += 8;
-            } else {
-                int count = 1;
-                if (value >>> 4 == 0) {
-                    count += 4;
-                    value <<= 4;
-                }
-                if (value >>> 6 == 0) {
-                    count += 2;
-                    value <<= 2;
-                }
-                zeroes += count - (value >>> 7);
-                break;
-            }
-        }
-        return zeroes;
-    }
-}

app/src/main/java/app/revanced/integrations/returnyoutubedislike/ReturnYouTubeDislike.java

@@ -5,6 +5,9 @@ import android.icu.text.CompactDecimalFormat;
 import android.os.Build;
 import android.text.SpannableString;
 
+import androidx.annotation.GuardedBy;
+import androidx.annotation.Nullable;
+
 import java.util.Locale;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicReference;
@@ -16,8 +19,16 @@ import app.revanced.integrations.utils.ReVancedUtils;
 import app.revanced.integrations.utils.SharedPrefHelper;
 
 public class ReturnYouTubeDislike {
+    /**
+     * maximum amount of time to block the UI from updates, while waiting for dislike network call to complete
+     */
+    private static final long MILLISECONDS_TO_BLOCK_UI_WHILE_WAITING_FOR_DISLIKE_FETCH_TO_COMPLETE = 5000;
+
+    // Different threads read and write these fields. access to them must be synchronized
+    @GuardedBy("this")
     private static String currentVideoId;
-    public static Integer dislikeCount;
+    @GuardedBy("this")
+    private static Integer dislikeCount;
 
     private static boolean isEnabled;
     private static boolean segmentedButton;
@@ -27,7 +38,7 @@ public class ReturnYouTubeDislike {
         DISLIKE(-1),
         LIKE_REMOVE(0);
 
-        public int value;
+        public final int value;
 
         Vote(int value) {
             this.value = value;
@@ -36,21 +47,14 @@ public class ReturnYouTubeDislike {
 
     private static Thread _dislikeFetchThread = null;
     private static Thread _votingThread = null;
-    private static Registration registration;
-    private static Voting voting;
     private static CompactDecimalFormat compactNumberFormatter;
 
     static {
-        Context context = ReVancedUtils.getContext();
         isEnabled = SettingsEnum.RYD_ENABLED.getBoolean();
-        if (isEnabled) {
-            registration = new Registration();
-            voting = new Voting(registration);
-        }
-
-        Locale locale = context.getResources().getConfiguration().locale;
-        LogHelper.debug(ReturnYouTubeDislike.class, "locale - " + locale);
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            Context context = ReVancedUtils.getContext();
+            Locale locale = context.getResources().getConfiguration().locale;
+            LogHelper.debug(ReturnYouTubeDislike.class, "Locale: " + locale);
             compactNumberFormatter = CompactDecimalFormat.getInstance(
                     locale,
                     CompactDecimalFormat.CompactStyle.SHORT
@@ -58,34 +62,90 @@ public class ReturnYouTubeDislike {
         }
     }
 
+    private ReturnYouTubeDislike() {
+    } // only static methods
+
     public static void onEnabledChange(boolean enabled) {
         isEnabled = enabled;
-        if (registration == null) {
+    }
-            registration = new Registration();
+
+    public static synchronized String getCurrentVideoId() {
+        return currentVideoId;
+    }
+
+    public static synchronized void setCurrentVideoId(String videoId) {
+        Objects.requireNonNull(videoId);
+        currentVideoId = videoId;
+        dislikeCount = null;
+    }
+
+    /**
+     * @return the dislikeCount for {@link #getCurrentVideoId()}.
+     * Returns NULL if the dislike is not yet loaded, or if the dislike network fetch failed.
+     */
+    public static synchronized Integer getDislikeCount() {
+        return dislikeCount;
+    }
+
+    /**
+     * @return true if the videoId parameter matches the current dislike request, and the set value was successful.
+     * If videoID parameter does not match currentVideoId, then this call does nothing
+     */
+    private static synchronized boolean setCurrentDislikeCount(String videoId, Integer videoIdDislikeCount) {
+        if (!videoId.equals(currentVideoId)) {
+            return false;
         }
-        if (voting == null) {
+        dislikeCount = videoIdDislikeCount;
-            voting = new Voting(registration);
+        return true;
+    }
+
+    private static void interruptDislikeFetchThreadIfRunning() {
+        if (_dislikeFetchThread == null) return;
+        try {
+            Thread.State dislikeFetchThreadState = _dislikeFetchThread.getState();
+            if (dislikeFetchThreadState != Thread.State.TERMINATED) {
+                LogHelper.debug(ReturnYouTubeDislike.class, "Interrupting the fetch dislike thread of state: " + dislikeFetchThreadState);
+                _dislikeFetchThread.interrupt();
+            }
+        } catch (Exception ex) {
+            LogHelper.printException(ReturnYouTubeDislike.class, "Error in the fetch dislike thread", ex);
+        }
+    }
+
+    private static void interruptVoteThreadIfRunning() {
+        if (_votingThread == null) return;
+        try {
+            Thread.State voteThreadState = _votingThread.getState();
+            if (voteThreadState != Thread.State.TERMINATED) {
+                LogHelper.debug(ReturnYouTubeDislike.class, "Interrupting the voting thread of state: " + voteThreadState);
+                _votingThread.interrupt();
+            }
+        } catch (Exception ex) {
+            LogHelper.printException(ReturnYouTubeDislike.class, "Error in the voting thread", ex);
         }
     }
 
     public static void newVideoLoaded(String videoId) {
-        LogHelper.debug(ReturnYouTubeDislike.class, "newVideoLoaded - " + videoId);
-
-        dislikeCount = null;
         if (!isEnabled) return;
+        LogHelper.debug(ReturnYouTubeDislike.class, "New video loaded: " + videoId);
 
-        currentVideoId = videoId;
+        setCurrentVideoId(videoId);
+        interruptDislikeFetchThreadIfRunning();
 
-        try {
+        // TODO use a private fixed size thread pool
-            if (_dislikeFetchThread != null && _dislikeFetchThread.getState() != Thread.State.TERMINATED) {
+        _dislikeFetchThread = new Thread(() -> {
-                LogHelper.debug(ReturnYouTubeDislike.class, "Interrupting the thread. Current state " + _dislikeFetchThread.getState());
+            try {
-                _dislikeFetchThread.interrupt();
+                Integer fetchedDislikeCount = ReturnYouTubeDislikeApi.fetchDislikes(videoId);
+                if (fetchedDislikeCount == null) {
+                    return; // fetch failed or thread was interrupted
+                }
+                if (!ReturnYouTubeDislike.setCurrentDislikeCount(videoId, fetchedDislikeCount)) {
+                    LogHelper.debug(ReturnYouTubeDislike.class, "Ignoring stale dislike fetched call for video " + videoId);
+                }
+            } catch (Exception ex) {
+                LogHelper.printException(ReturnYouTubeDislike.class, "Failed to fetch dislikes for videoId: " + videoId, ex);
             }
-        } catch (Exception ex) {
+        });
-            LogHelper.printException(ReturnYouTubeDislike.class, "Error in the dislike fetch thread", ex);
-        }
-
-        _dislikeFetchThread = new Thread(() -> ReturnYouTubeDislikeApi.fetchDislikes(videoId));
         _dislikeFetchThread.start();
     }
 
@@ -96,17 +156,26 @@ public class ReturnYouTubeDislike {
             var conversionContextString = conversionContext.toString();
 
             // Check for new component
-            if (conversionContextString.contains("|segmented_like_dislike_button.eml|"))
+            if (conversionContextString.contains("|segmented_like_dislike_button.eml|")) {
                 segmentedButton = true;
-            else if (!conversionContextString.contains("|dislike_button.eml|"))
+            } else if (!conversionContextString.contains("|dislike_button.eml|")) {
+                LogHelper.debug(ReturnYouTubeDislike.class, "could not find a dislike button in " + conversionContextString);
                 return;
-
+            }
 
             // Have to block the current thread until fetching is done
             // There's no known way to edit the text after creation yet
-            if (_dislikeFetchThread != null) _dislikeFetchThread.join();
+            if (_dislikeFetchThread != null) {
+                _dislikeFetchThread.join(MILLISECONDS_TO_BLOCK_UI_WHILE_WAITING_FOR_DISLIKE_FETCH_TO_COMPLETE);
+            }
 
-            if (dislikeCount == null) return;
+            Integer fetchedDislikeCount = getDislikeCount();
+            if (fetchedDislikeCount == null) {
+                LogHelper.debug(ReturnYouTubeDislike.class, "Cannot add dislike count to UI (dislike count not available)");
+                // There's no point letting the request continue, as there is not another chance to use the result
+                interruptDislikeFetchThreadIfRunning();
+                return;
+            }
 
             updateDislike(textRef, dislikeCount);
             LogHelper.debug(ReturnYouTubeDislike.class, "Updated text on component" + conversionContextString);
@@ -118,24 +187,18 @@ public class ReturnYouTubeDislike {
     public static void sendVote(Vote vote) {
         if (!isEnabled) return;
 
-        Context context = ReVancedUtils.getContext();
+        Context context = Objects.requireNonNull(ReVancedUtils.getContext());
-        if (SharedPrefHelper.getBoolean(Objects.requireNonNull(context), SharedPrefHelper.SharedPrefNames.YOUTUBE, "user_signed_out", true))
+        if (SharedPrefHelper.getBoolean(context, SharedPrefHelper.SharedPrefNames.YOUTUBE, "user_signed_out", true))
             return;
 
-        LogHelper.debug(ReturnYouTubeDislike.class, "sending vote - " + vote + " for video " + currentVideoId);
+        // Must make a local copy of videoId, since it may change between now and when the vote thread runs
-        try {
+        String videoIdToVoteFor = getCurrentVideoId();
-            if (_votingThread != null && _votingThread.getState() != Thread.State.TERMINATED) {
+        interruptVoteThreadIfRunning();
-                LogHelper.debug(ReturnYouTubeDislike.class, "Interrupting the thread. Current state " + _votingThread.getState());
-                _votingThread.interrupt();
-            }
-        } catch (Exception ex) {
-            LogHelper.printException(ReturnYouTubeDislike.class, "Error in the voting thread", ex);
-        }
 
+        // TODO: use a private fixed sized thread pool
         _votingThread = new Thread(() -> {
             try {
-                boolean result = voting.sendVote(currentVideoId, vote);
+                ReturnYouTubeDislikeApi.sendVote(videoIdToVoteFor, getUserId(), vote);
-                LogHelper.debug(ReturnYouTubeDislike.class, "sendVote status " + result);
             } catch (Exception ex) {
                 LogHelper.printException(ReturnYouTubeDislike.class, "Failed to send vote", ex);
             }
@@ -143,11 +206,40 @@ public class ReturnYouTubeDislike {
         _votingThread.start();
     }
 
+    /**
+     * Lock used exclusively by {@link #getUserId()}
+     */
+    private static final Object rydUserIdLock = new Object();
+
+    /**
+     * Must call off main thread, as this will make a network call if user has not yet been registered yet
+     *
+     * @return ReturnYouTubeDislike user ID. If user registration has never happened
+     * and the network call fails, this will return NULL
+     */
+    @Nullable
+    private static String getUserId() {
+        ReVancedUtils.verifyOffMainThread();
+
+        synchronized (rydUserIdLock) {
+            String userId = SettingsEnum.RYD_USER_ID.getString();
+            if (userId != null) {
+                return userId;
+            }
+
+            userId = ReturnYouTubeDislikeApi.registerAsNewUser(); // blocks until network call is completed
+            if (userId != null) {
+                SettingsEnum.RYD_USER_ID.saveValue(userId);
+            }
+            return userId;
+        }
+    }
+
     private static void updateDislike(AtomicReference<Object> textRef, Integer dislikeCount) {
         SpannableString oldSpannableString = (SpannableString) textRef.get();
 
-        // parse the buttons string
+        // Parse the buttons string.
-        // if the button is segmented, only get the like count as a string
+        // If the button is segmented, only get the like count as a string
         var oldButtonString = oldSpannableString.toString();
         if (segmentedButton) oldButtonString = oldButtonString.split(" \\| ")[0];
 

app/src/main/java/app/revanced/integrations/returnyoutubedislike/Voting.java

@@ -1,18 +0,0 @@
-package app.revanced.integrations.returnyoutubedislike;
-
-import app.revanced.integrations.utils.LogHelper;
-import app.revanced.integrations.returnyoutubedislike.requests.ReturnYouTubeDislikeApi;
-
-public class Voting {
-    private Registration registration;
-
-    public Voting(Registration registration) {
-        this.registration = registration;
-    }
-
-    public boolean sendVote(String videoId, ReturnYouTubeDislike.Vote vote) {
-        String userId = registration.getUserId();
-        LogHelper.debug(Voting.class, "Trying to vote the following video: " + videoId + " with vote " + vote + " and userId: " + userId);
-        return ReturnYouTubeDislikeApi.sendVote(videoId, userId, vote.value);
-    }
-}

app/src/main/java/app/revanced/integrations/returnyoutubedislike/requests/ReturnYouTubeDislikeApi.java

@@ -2,71 +2,178 @@ package app.revanced.integrations.returnyoutubedislike.requests;
 
 import static app.revanced.integrations.requests.Requester.parseJson;
 
+import android.util.Base64;
+
+import androidx.annotation.Nullable;
 
 import org.json.JSONObject;
 
 import java.io.IOException;
 import java.io.OutputStream;
 import java.net.HttpURLConnection;
+import java.net.ProtocolException;
 import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.SecureRandom;
+import java.util.Objects;
 
-import app.revanced.integrations.returnyoutubedislike.ReturnYouTubeDislike;
-import app.revanced.integrations.utils.LogHelper;
-import app.revanced.integrations.returnyoutubedislike.Registration;
 import app.revanced.integrations.requests.Requester;
 import app.revanced.integrations.requests.Route;
+import app.revanced.integrations.returnyoutubedislike.ReturnYouTubeDislike;
+import app.revanced.integrations.utils.LogHelper;
+import app.revanced.integrations.utils.ReVancedUtils;
 
 public class ReturnYouTubeDislikeApi {
     private static final String RYD_API_URL = "https://returnyoutubedislikeapi.com/";
 
+    private static final int HTTP_CONNECTION_DEFAULT_TIMEOUT = 5000;
+
+    /**
+     * Indicates a client rate limit has been reached
+     */
+    private static final int RATE_LIMIT_HTTP_STATUS_CODE = 429;
+
+    /**
+     * How long wait until API calls are resumed, if a rate limit is hit
+     * No clear guideline of how long to backoff.  Using 60 seconds for now.
+     */
+    private static final int RATE_LIMIT_BACKOFF_SECONDS = 60;
+
+    /**
+     * Last time a {@link #RATE_LIMIT_HTTP_STATUS_CODE} was reached.
+     * zero if has not been reached.
+     */
+    private static volatile long lastTimeLimitWasHit; // must be volatile, since different threads access this
+
     private ReturnYouTubeDislikeApi() {
+    } // utility class
+
+    /**
+     * @return True, if api rate limit is in effect.
+     */
+    private static boolean checkIfRateLimitInEffect(String apiEndPointName) {
+        if (lastTimeLimitWasHit == 0) {
+            return false;
+        }
+        final long numberOfSecondsSinceLastRateLimit = (System.currentTimeMillis() - lastTimeLimitWasHit) / 1000;
+        if (numberOfSecondsSinceLastRateLimit < RATE_LIMIT_BACKOFF_SECONDS) {
+            LogHelper.debug(ReturnYouTubeDislikeApi.class, "Ignoring api call " + apiEndPointName + " as only "
+                    + numberOfSecondsSinceLastRateLimit + " seconds has passed since last rate limit.");
+            return true;
+        }
+        return false;
     }
 
-    public static void fetchDislikes(String videoId) {
+    /**
+     * @return True, if the rate limit was reached.
+     */
+    private static boolean checkIfRateLimitWasHit(int httpResponseCode) {
+        // set to true, to verify rate limit works
+        final boolean DEBUG_RATE_LIMIT = false;
+        if (DEBUG_RATE_LIMIT) {
+            final double RANDOM_RATE_LIMIT_PERCENTAGE = 0.1; // 10% chance of a triggering a rate limit
+            if (Math.random() < RANDOM_RATE_LIMIT_PERCENTAGE) {
+                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Artificially triggering rate limit for debug purposes");
+                httpResponseCode = RATE_LIMIT_HTTP_STATUS_CODE;
+            }
+        }
+
+        if (httpResponseCode == RATE_LIMIT_HTTP_STATUS_CODE) {
+            lastTimeLimitWasHit = System.currentTimeMillis();
+            LogHelper.debug(ReturnYouTubeDislikeApi.class, "API rate limit was hit. Stopping API calls for the next "
+                    + RATE_LIMIT_BACKOFF_SECONDS + " seconds");
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * @return The number of dislikes.
+     * Returns NULL if fetch failed, calling thread is interrupted, or rate limit is in effect.
+     */
+    @Nullable
+    public static Integer fetchDislikes(String videoId) {
+        ReVancedUtils.verifyOffMainThread();
+        Objects.requireNonNull(videoId);
         try {
+            if (checkIfRateLimitInEffect("fetchDislikes")) {
+                return null;
+            }
             LogHelper.debug(ReturnYouTubeDislikeApi.class, "Fetching dislikes for " + videoId);
             HttpURLConnection connection = getConnectionFromRoute(ReturnYouTubeDislikeRoutes.GET_DISLIKES, videoId);
-            connection.setConnectTimeout(1000);
+            connection.setConnectTimeout(HTTP_CONNECTION_DEFAULT_TIMEOUT);
-            if (connection.getResponseCode() == 200) {
+            final int responseCode = connection.getResponseCode();
+            if (checkIfRateLimitWasHit(responseCode)) {
+                connection.disconnect();
+                return null;
+            } else if (responseCode == 200) {
                 JSONObject json = getJSONObject(connection);
-                ReturnYouTubeDislike.dislikeCount = json.getInt("dislikes");
+                Integer fetchedDislikeCount = json.getInt("dislikes");
-                LogHelper.debug(ReturnYouTubeDislikeApi.class, "dislikes fetched - " + ReturnYouTubeDislike.dislikeCount);
+                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Dislikes fetched: " + fetchedDislikeCount);
+                connection.disconnect();
+                return fetchedDislikeCount;
             } else {
-                LogHelper.debug(ReturnYouTubeDislikeApi.class, "dislikes fetch response was " + connection.getResponseCode());
+                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Dislikes fetch response was " + responseCode);
+                connection.disconnect();
             }
-            connection.disconnect();
         } catch (Exception ex) {
             LogHelper.printException(ReturnYouTubeDislikeApi.class, "Failed to fetch dislikes", ex);
         }
+        return null;
     }
 
-    public static String register(String userId, Registration registration) {
+    /**
+     * @return The newly created and registered user id.  Returns NULL if registration failed.
+     */
+    @Nullable
+    public static String registerAsNewUser() {
+        ReVancedUtils.verifyOffMainThread();
         try {
+            if (checkIfRateLimitInEffect("registerAsNewUser")) {
+                return null;
+            }
+            String userId = randomString(36);
+            LogHelper.debug(ReturnYouTubeDislikeApi.class, "Trying to register the following userId: " + userId);
+
             HttpURLConnection connection = getConnectionFromRoute(ReturnYouTubeDislikeRoutes.GET_REGISTRATION, userId);
-            connection.setConnectTimeout(5 * 1000);
+            connection.setConnectTimeout(HTTP_CONNECTION_DEFAULT_TIMEOUT);
-            if (connection.getResponseCode() == 200) {
+            final int responseCode = connection.getResponseCode();
+            if (checkIfRateLimitWasHit(responseCode)) {
+                connection.disconnect();
+                return null;
+            } else if (responseCode == 200) {
                 JSONObject json = getJSONObject(connection);
                 String challenge = json.getString("challenge");
                 int difficulty = json.getInt("difficulty");
                 LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration challenge - " + challenge + " with difficulty of " + difficulty);
+                connection.disconnect();
 
                 // Solve the puzzle
-                String solution = Registration.solvePuzzle(challenge, difficulty);
+                String solution = solvePuzzle(challenge, difficulty);
                 LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration confirmation solution is " + solution);
-
+                if (solution == null) {
-                return confirmRegistration(userId, solution, registration);
+                    return null; // failed to solve puzzle
+                }
+                return confirmRegistration(userId, solution);
             } else {
-                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration response was " + connection.getResponseCode());
+                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration response was " + responseCode);
+                connection.disconnect();
             }
-            connection.disconnect();
         } catch (Exception ex) {
             LogHelper.printException(ReturnYouTubeDislikeApi.class, "Failed to register userId", ex);
         }
         return null;
     }
 
-    private static String confirmRegistration(String userId, String solution, Registration registration) {
+    @Nullable
+    private static String confirmRegistration(String userId, String solution) {
+        ReVancedUtils.verifyOffMainThread();
+        Objects.requireNonNull(userId);
+        Objects.requireNonNull(solution);
         try {
+            if (checkIfRateLimitInEffect("confirmRegistration")) {
+                return null;
+            }
             LogHelper.debug(ReturnYouTubeDislikeApi.class, "Trying to confirm registration for the following userId: " + userId + " with solution: " + solution);
 
             HttpURLConnection connection = getConnectionFromRoute(ReturnYouTubeDislikeRoutes.CONFIRM_REGISTRATION, userId);
@@ -77,20 +184,25 @@ public class ReturnYouTubeDislikeApi {
                 byte[] input = jsonInputString.getBytes(StandardCharsets.UTF_8);
                 os.write(input, 0, input.length);
             }
-            if (connection.getResponseCode() == 200) {
+            final int responseCode = connection.getResponseCode();
+            if (checkIfRateLimitWasHit(responseCode)) {
+                connection.disconnect();
+                return null;
+            }
+
+            if (responseCode == 200) {
                 String result = parseJson(connection);
                 LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration confirmation result was " + result);
+                connection.disconnect();
 
                 if (result.equalsIgnoreCase("true")) {
-                    registration.saveUserId(userId);
                     LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration was successful for user " + userId);
-
                     return userId;
                 }
             } else {
-                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration confirmation response was " + connection.getResponseCode());
+                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Registration confirmation response was " + responseCode);
+                connection.disconnect();
             }
-            connection.disconnect();
         } catch (Exception ex) {
             LogHelper.printException(ReturnYouTubeDislikeApi.class, "Failed to confirm registration", ex);
         }
@@ -98,33 +210,50 @@ public class ReturnYouTubeDislikeApi {
         return null;
     }
 
-    public static boolean sendVote(String videoId, String userId, int vote) {
+    public static boolean sendVote(String videoId, String userId, ReturnYouTubeDislike.Vote vote) {
+        ReVancedUtils.verifyOffMainThread();
+        Objects.requireNonNull(videoId);
+        Objects.requireNonNull(userId);
+        Objects.requireNonNull(vote);
+
+        if (checkIfRateLimitInEffect("sendVote")) {
+            return false;
+        }
+        LogHelper.debug(ReturnYouTubeDislikeApi.class, "Trying to vote the following video: "
+                + videoId + " with vote " + vote + " and userId: " + userId);
         try {
             HttpURLConnection connection = getConnectionFromRoute(ReturnYouTubeDislikeRoutes.SEND_VOTE);
             applyCommonRequestSettings(connection);
 
-            String voteJsonString = "{\"userId\": \"" + userId + "\", \"videoId\": \"" + videoId + "\", \"value\": \"" + vote + "\"}";
+            String voteJsonString = "{\"userId\": \"" + userId + "\", \"videoId\": \"" + videoId + "\", \"value\": \"" + vote.value + "\"}";
             try (OutputStream os = connection.getOutputStream()) {
                 byte[] input = voteJsonString.getBytes(StandardCharsets.UTF_8);
                 os.write(input, 0, input.length);
             }
 
-            if (connection.getResponseCode() == 200) {
+            final int responseCode = connection.getResponseCode();
+            if (checkIfRateLimitWasHit(responseCode)) {
+                connection.disconnect();
+                return false;
+            }
+
+            if (responseCode == 200) {
                 JSONObject json = getJSONObject(connection);
                 String challenge = json.getString("challenge");
                 int difficulty = json.getInt("difficulty");
                 LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote challenge - " + challenge + " with difficulty of " + difficulty);
+                connection.disconnect();
 
                 // Solve the puzzle
-                String solution = Registration.solvePuzzle(challenge, difficulty);
+                String solution = solvePuzzle(challenge, difficulty);
                 LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote confirmation solution is " + solution);
 
                 // Confirm vote
                 return confirmVote(videoId, userId, solution);
             } else {
-                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote response was " + connection.getResponseCode());
+                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote response was " + responseCode);
+                connection.disconnect();
             }
-            connection.disconnect();
         } catch (Exception ex) {
             LogHelper.printException(ReturnYouTubeDislikeApi.class, "Failed to send vote", ex);
         }
@@ -132,6 +261,14 @@ public class ReturnYouTubeDislikeApi {
     }
 
     private static boolean confirmVote(String videoId, String userId, String solution) {
+        ReVancedUtils.verifyOffMainThread();
+        Objects.requireNonNull(videoId);
+        Objects.requireNonNull(userId);
+        Objects.requireNonNull(solution);
+
+        if (checkIfRateLimitInEffect("confirmVote")) {
+            return false;
+        }
         try {
             HttpURLConnection connection = getConnectionFromRoute(ReturnYouTubeDislikeRoutes.CONFIRM_VOTE);
             applyCommonRequestSettings(connection);
@@ -141,20 +278,28 @@ public class ReturnYouTubeDislikeApi {
                 byte[] input = jsonInputString.getBytes(StandardCharsets.UTF_8);
                 os.write(input, 0, input.length);
             }
-            if (connection.getResponseCode() == 200) {
+            final int responseCode = connection.getResponseCode();
+            if (checkIfRateLimitWasHit(responseCode)) {
+                connection.disconnect();
+                return false;
+            }
+
+            if (responseCode == 200) {
                 String result = parseJson(connection);
                 LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote confirmation result was " + result);
-
+                connection.disconnect();
 
                 if (result.equalsIgnoreCase("true")) {
                     LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote was successful for user " + userId);
-
                     return true;
+                } else {
+                    LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote was unsuccessful for user " + userId);
+                    return false;
                 }
             } else {
-                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote confirmation response was " + connection.getResponseCode());
+                LogHelper.debug(ReturnYouTubeDislikeApi.class, "Vote confirmation response was " + responseCode);
+                connection.disconnect();
             }
-            connection.disconnect();
         } catch (Exception ex) {
             LogHelper.printException(ReturnYouTubeDislikeApi.class, "Failed to confirm vote", ex);
         }
@@ -163,12 +308,12 @@ public class ReturnYouTubeDislikeApi {
 
     // utils
 
-    private static void applyCommonRequestSettings(HttpURLConnection connection) throws Exception {
+    private static void applyCommonRequestSettings(HttpURLConnection connection) throws ProtocolException {
         connection.setRequestMethod("POST");
         connection.setRequestProperty("Content-Type", "application/json");
         connection.setRequestProperty("Accept", "application/json");
         connection.setDoOutput(true);
-        connection.setConnectTimeout(5 * 1000);
+        connection.setConnectTimeout(HTTP_CONNECTION_DEFAULT_TIMEOUT);
     }
 
     // helpers
@@ -180,4 +325,68 @@ public class ReturnYouTubeDislikeApi {
     private static JSONObject getJSONObject(HttpURLConnection connection) throws Exception {
         return Requester.getJSONObject(connection);
     }
+
+    private static String solvePuzzle(String challenge, int difficulty) {
+        byte[] decodedChallenge = Base64.decode(challenge, Base64.NO_WRAP);
+
+        byte[] buffer = new byte[20];
+        for (int i = 4; i < 20; i++) {
+            buffer[i] = decodedChallenge[i - 4];
+        }
+
+        try {
+            int maxCount = (int) (Math.pow(2, difficulty + 1) * 5);
+            MessageDigest md = MessageDigest.getInstance("SHA-512");
+            for (int i = 0; i < maxCount; i++) {
+                buffer[0] = (byte) i;
+                buffer[1] = (byte) (i >> 8);
+                buffer[2] = (byte) (i >> 16);
+                buffer[3] = (byte) (i >> 24);
+                byte[] messageDigest = md.digest(buffer);
+
+                if (countLeadingZeroes(messageDigest) >= difficulty) {
+                    return Base64.encodeToString(new byte[]{buffer[0], buffer[1], buffer[2], buffer[3]}, Base64.NO_WRAP);
+                }
+            }
+        } catch (Exception ex) {
+            LogHelper.printException(ReturnYouTubeDislikeApi.class, "Failed to solve puzzle", ex);
+        }
+
+        return null;
+    }
+
+    // https://stackoverflow.com/a/157202
+    private static String randomString(int len) {
+        String AB = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+        SecureRandom rnd = new SecureRandom();
+
+        StringBuilder sb = new StringBuilder(len);
+        for (int i = 0; i < len; i++)
+            sb.append(AB.charAt(rnd.nextInt(AB.length())));
+        return sb.toString();
+    }
+
+    private static int countLeadingZeroes(byte[] uInt8View) {
+        int zeroes = 0;
+        int value = 0;
+        for (int i = 0; i < uInt8View.length; i++) {
+            value = uInt8View[i] & 0xFF;
+            if (value == 0) {
+                zeroes += 8;
+            } else {
+                int count = 1;
+                if (value >>> 4 == 0) {
+                    count += 4;
+                    value <<= 4;
+                }
+                if (value >>> 6 == 0) {
+                    count += 2;
+                    value <<= 2;
+                }
+                zeroes += count - (value >>> 7);
+                break;
+            }
+        }
+        return zeroes;
+    }
 }

app/src/main/java/app/revanced/integrations/settings/SettingsEnum.java

@@ -140,7 +140,9 @@ public enum SettingsEnum {
     private final ReturnType returnType;
     private final boolean rebootApp;
 
-    private Object value = null;
+    // must be volatile, as some settings are changed from non-main threads
+    // of note, the object value is persistently stored using SharedPreferences (which is thread safe)
+    private volatile Object value;
 
     SettingsEnum(String path, Object defaultValue, ReturnType returnType) {
         this.path = path;

app/src/main/java/app/revanced/integrations/utils/LogHelper.java

@@ -25,4 +25,4 @@ public class LogHelper {
     public static void info(Class clazz, String message) {
         Log.i("revanced: " + (clazz != null ? clazz.getSimpleName() : ""), message);
     }
-}
+}

app/src/main/java/app/revanced/integrations/utils/ReVancedUtils.java

@@ -1,5 +1,6 @@
 package app.revanced.integrations.utils;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.res.Resources;
 import android.os.Handler;
@@ -10,10 +11,14 @@ import app.revanced.integrations.sponsorblock.player.PlayerType;
 public class ReVancedUtils {
 
     private static PlayerType env;
-    public static boolean newVideo = false;
+    private static boolean newVideo = false;
 
+    @SuppressLint("StaticFieldLeak")
     public static Context context;
 
+    private ReVancedUtils() {
+    } // utility class
+
     public static boolean containsAny(final String value, final String... targets) {
         for (String string : targets)
             if (!string.isEmpty() && value.contains(string)) return true;
@@ -52,10 +57,6 @@ public class ReVancedUtils {
         return context.getResources().getIdentifier(name, defType, context.getPackageName());
     }
 
-    public static void runOnMainThread(Runnable runnable) {
-        new Handler(Looper.getMainLooper()).post(runnable);
-    }
-
     public static Context getContext() {
         if (context != null) {
             return context;
@@ -68,4 +69,33 @@ public class ReVancedUtils {
     public static boolean isTablet(Context context) {
         return context.getResources().getConfiguration().smallestScreenWidthDp >= 600;
     }
+
+    public static void runOnMainThread(Runnable runnable) {
+        new Handler(Looper.getMainLooper()).post(runnable);
+    }
+
+    /**
+     * @return if the calling thread is on the main thread
+     */
+    public static boolean currentIsOnMainThread() {
+        return Looper.getMainLooper().isCurrentThread();
+    }
+
+    /**
+     * @throws IllegalStateException if the calling thread is _not_ on the main thread
+     */
+    public static void verifyOnMainThread() throws IllegalStateException {
+        if (!currentIsOnMainThread()) {
+            throw new IllegalStateException("Must call _on_ the main thread");
+        }
+    }
+
+    /**
+     * @throws IllegalStateException if the calling thread _is_ on the main thread
+     */
+    public static void verifyOffMainThread() throws IllegalStateException {
+        if (currentIsOnMainThread()) {
+            throw new IllegalStateException("Must call _off_ the main thread");
+        }
+    }
 }