/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.car.pm;

import static android.car.user.CarUserManager.USER_LIFECYCLE_EVENT_TYPE_INVISIBLE;
import static android.car.user.CarUserManager.USER_LIFECYCLE_EVENT_TYPE_POST_UNLOCKED;
import static android.car.user.CarUserManager.USER_LIFECYCLE_EVENT_TYPE_SWITCHING;
import static android.car.user.CarUserManager.USER_LIFECYCLE_EVENT_TYPE_UNLOCKED;
import static android.car.user.CarUserManager.USER_LIFECYCLE_EVENT_TYPE_VISIBLE;
import static android.content.Context.BIND_AUTO_CREATE;
import static android.os.Process.INVALID_UID;

import static com.android.car.CarLog.TAG_AM;
import static com.android.car.internal.ExcludeFromCodeCoverageGeneratedReport.DUMP_INFO;

import android.annotation.Nullable;
import android.annotation.SuppressLint;
import android.annotation.UserIdInt;
import android.car.builtin.util.Slogf;
import android.car.hardware.power.CarPowerManager;
import android.car.hardware.power.ICarPowerStateListener;
import android.car.user.CarUserManager.UserLifecycleEvent;
import android.car.user.CarUserManager.UserLifecycleListener;
import android.car.user.UserLifecycleEventFilter;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.content.res.Resources;
import android.net.Uri;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;
import android.os.UserHandle;
import android.os.UserManager;
import android.text.TextUtils;
import android.util.Log;

import com.android.car.CarLocalServices;
import com.android.car.CarLog;
import com.android.car.R;
import com.android.car.internal.ExcludeFromCodeCoverageGeneratedReport;
import com.android.car.internal.util.IndentingPrintWriter;
import com.android.car.power.CarPowerManagementService;
import com.android.car.user.ActivityManagerCurrentUserFetcher;
import com.android.car.user.CarUserService;
import com.android.car.user.CurrentUserFetcher;
import com.android.internal.annotations.VisibleForTesting;

import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Executor;

/**
 * Class that responsible for controlling vendor services that was opted in to be bound/started
 * by the Car Service.
 *
 * <p>Thread-safety note: all code runs in the {@code Handler} provided in the constructor, whenever
 * possible pass {@link #mHandler} when subscribe for callbacks otherwise redirect code to the
 * handler.
 */
final class VendorServiceController implements UserLifecycleListener {

    @VisibleForTesting
    static final String TAG = CarLog.tagFor(VendorServiceController.class);

    private static final boolean DBG = Slogf.isLoggable(TAG, Log.DEBUG);
    private static final String PACKAGE_DATA_SCHEME = "package";

    private final List<VendorServiceInfo> mVendorServiceInfos = new ArrayList<>();
    private final Map<ConnectionKey, VendorServiceConnection> mConnections =
            new ConcurrentHashMap<>();
    private final Context mContext;
    private final UserManager mUserManager;
    private final Handler mHandler;
    private CarUserService mCarUserService;
    private CarPowerManagementService mPowerManagementService;
    private CurrentUserFetcher mCurrentUserFetcher;

    private final BroadcastReceiver mPackageChangeReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (DBG) {
                Slogf.d(TAG_AM, "Package change received with action = %s", action);
            }

            Uri packageData = intent.getData();
            if (packageData == null) {
                Slogf.wtf(TAG_AM, "null packageData");
                return;
            }
            String packageName = packageData.getSchemeSpecificPart();
            if (packageName == null) {
                Slogf.w(TAG_AM, "null packageName");
                return;
            }
            int uid = intent.getIntExtra(Intent.EXTRA_UID, INVALID_UID);
            int userId = UserHandle.getUserHandleForUid(uid).getIdentifier();

            switch (action) {
                case Intent.ACTION_PACKAGE_CHANGED:
                    // Fall through
                case Intent.ACTION_PACKAGE_REPLACED:
                    // Fall through
                case Intent.ACTION_PACKAGE_ADDED:
                    startOrBindServiceForPackage(packageName, userId);
                    break;
                case Intent.ACTION_PACKAGE_REMOVED:
                    stopOrUnbindService(packageName, userId);
                    break;
                default:
                    Slogf.w(TAG_AM, "This package change event (%s) can't be handled.",
                            action);
            }
        }
    };

    private final ICarPowerStateListener mCarPowerStateListener =
            new ICarPowerStateListener.Stub() {
                @Override
                public void onStateChanged(int state, long expirationTimeMs) {
                    if (DBG) {
                        Slogf.d(TAG, "Power state change received. State = %d", state);
                    }
                    if (state == CarPowerManager.STATE_HIBERNATION_EXIT
                            || state == CarPowerManager.STATE_SUSPEND_EXIT) {
                        onPowerResumed();
                    }
                }
            };

    VendorServiceController(Context context, Looper looper) {
        this(context, looper, new ActivityManagerCurrentUserFetcher());
    }

    @VisibleForTesting
    VendorServiceController(Context context, Looper looper,
            CurrentUserFetcher currentUserFetcher) {
        mContext = context;
        mUserManager = context.getSystemService(UserManager.class);
        mHandler = new Handler(looper);
        mCurrentUserFetcher = currentUserFetcher;
    }

    void init() {
        if (!loadXmlConfiguration()) {
            return;  // Nothing to do
        }

        mPowerManagementService = CarLocalServices.getService(CarPowerManagementService.class);
        mCarUserService = CarLocalServices.getService(CarUserService.class);
        UserLifecycleEventFilter userLifecycleEventFilter =
                new UserLifecycleEventFilter.Builder()
                        .addEventType(USER_LIFECYCLE_EVENT_TYPE_SWITCHING)
                        .addEventType(USER_LIFECYCLE_EVENT_TYPE_UNLOCKED)
                        .addEventType(USER_LIFECYCLE_EVENT_TYPE_VISIBLE)
                        .addEventType(USER_LIFECYCLE_EVENT_TYPE_INVISIBLE)
                        .addEventType(USER_LIFECYCLE_EVENT_TYPE_POST_UNLOCKED).build();
        mCarUserService.addUserLifecycleListener(userLifecycleEventFilter, this);

        startOrBindServicesIfNeeded();
        mPowerManagementService.registerListener(mCarPowerStateListener);
        registerPackageChangeReceiver();
    }

    void release() {
        if (mVendorServiceInfos.isEmpty()) {
            Slogf.d(TAG_AM, "Releasing VendorServiceController without deep cleaning as no vendor "
                    + "service info present. ");
            return;
        }
        if (mCarUserService != null) {
            mCarUserService.removeUserLifecycleListener(this);
        }
        unregisterPackageChangeReceiver();
        mPowerManagementService.unregisterListener(mCarPowerStateListener);
        for (ConnectionKey key : mConnections.keySet()) {
            stopOrUnbindService(key.mVendorServiceInfo, key.mUserHandle);
        }
        mVendorServiceInfos.clear();
        mConnections.clear();
    }

    @ExcludeFromCodeCoverageGeneratedReport(reason = DUMP_INFO)
    public void dump(IndentingPrintWriter writer) {
        writer.println("VendorServiceController:");

        writer.increaseIndent();
        writer.printf("DBG=%b\n", DBG);

        writer.println("VendorServiceInfo:");
        writer.increaseIndent();
        for (VendorServiceInfo info : mVendorServiceInfos) {
            writer.println(info.toString());
        }
        writer.decreaseIndent(); // end of VendorServiceInfo:

        writer.println("Connections:");
        writer.increaseIndent();
        for (VendorServiceConnection connection : mConnections.values()) {
            connection.dump(writer);
        }
        writer.decreaseIndent(); // end of Connections:

        writer.decreaseIndent(); // end of VendorServiceController:
    }

    @Override
    public void onEvent(UserLifecycleEvent event) {
        if (DBG) {
            Slogf.d(TAG, "onEvent(" + event + ")");
        }
        int userId = event.getUserId();
        switch (event.getEventType()) {
            case USER_LIFECYCLE_EVENT_TYPE_VISIBLE:
                mHandler.post(() -> handleOnUserVisible(userId));
                break;
            case USER_LIFECYCLE_EVENT_TYPE_INVISIBLE:
                mHandler.post(() -> handleOnUserInvisible(userId));
                break;
            case USER_LIFECYCLE_EVENT_TYPE_SWITCHING:
                mHandler.post(() -> handleOnUserSwitching(userId));
                break;
            case USER_LIFECYCLE_EVENT_TYPE_UNLOCKED:
                mHandler.post(() -> handleOnUserUnlocked(userId, /* forPostUnlock= */ false));
                break;
            case USER_LIFECYCLE_EVENT_TYPE_POST_UNLOCKED:
                mHandler.post(() -> handleOnUserUnlocked(userId, /* forPostUnlock= */ true));
                break;
            default:
                // Shouldn't happen as listener was registered with filter
                Slogf.wtf(TAG, "Invalid event: %s", event);
        }
    }

    /** Handles power resume events, starting services with `trigger=resume`. */
    private void onPowerResumed() {
        if (DBG) {
            Slogf.d(TAG, "onPowerResumed()");
        }

        int size = mVendorServiceInfos.size();
        for (int i = 0; i < size; i++) {
            VendorServiceInfo serviceInfo = mVendorServiceInfos.get(i);
            // RESUME events handle the system user only. Current or visible users are handled by
            // user lifecycle events (unlock, visible, etc).
            boolean isForSystemOrAllUsers = serviceInfo.isSystemUserService();
            boolean isResumeTrigger = serviceInfo.shouldStartOnResume();
            if (isForSystemOrAllUsers && isResumeTrigger) {
                startOrBindService(serviceInfo, UserHandle.SYSTEM);
            }
        }
    }

    private void registerPackageChangeReceiver() {
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_PACKAGE_CHANGED);
        filter.addAction(Intent.ACTION_PACKAGE_REPLACED);
        filter.addAction(Intent.ACTION_PACKAGE_ADDED);
        filter.addAction(Intent.ACTION_PACKAGE_REMOVED);
        filter.addDataScheme(PACKAGE_DATA_SCHEME);
        mContext.registerReceiverForAllUsers(mPackageChangeReceiver, filter,
                /* broadcastPermission= */ null, /* scheduler= */ null,
                Context.RECEIVER_NOT_EXPORTED);
    }

    private void unregisterPackageChangeReceiver() {
        mContext.unregisterReceiver(mPackageChangeReceiver);
    }

    private void startOrBindServiceForPackage(String packageName, @UserIdInt int userId) {
        if (DBG) {
            Slogf.d(TAG, "startOrBindServiceForPackage() for package=%s, userId=%d",
                    packageName, userId);
        }

        int currentUserId = mCurrentUserFetcher.getCurrentUser();
        int size = mVendorServiceInfos.size();
        for (int i = 0; i < size; i++) {
            VendorServiceInfo serviceInfo = mVendorServiceInfos.get(i);
            // Start or bind the service when the package name matches and the user is in scope.
            if (packageName.equals(serviceInfo.getIntent().getComponent().getPackageName())
                    && isUserInScope(userId, serviceInfo, mCarUserService, currentUserId)) {
                startOrBindService(serviceInfo, UserHandle.of(userId));
            }
        }
    }

    /** Checks if the given {@code serviceInfo} satisfies the user scope. */
    private static boolean isUserInScope(@UserIdInt int userId, VendorServiceInfo serviceInfo,
            CarUserService carUserService, @UserIdInt int currentUserId) {
        boolean isSystemUser = userId == UserHandle.SYSTEM.getIdentifier();
        boolean isCurrentUser = userId == currentUserId;

        return (isSystemUser && serviceInfo.isSystemUserService())
            || (!isSystemUser && isCurrentUser && serviceInfo.isForegroundUserService())
            || ((serviceInfo.isVisibleUserService()
                    || (!isCurrentUser && serviceInfo.isBackgroundVisibleUserService()))
                && carUserService.isUserVisible(userId));
    }

    private void handleOnUserSwitching(@UserIdInt int userId) {
        // The user switch notification is obsolete if userId is different from the current
        // foreground user. Ignore it.
        int currentUserId = mCurrentUserFetcher.getCurrentUser();
        if (currentUserId != userId) {
            Slogf.w(TAG, "Received userSwitch event for user " + userId
                    + " while current foreground user is " + currentUserId + "."
                    + " Ignore the switch user event.");
            return;
        }

        // Clean up the services which do not satisfy their configured user scope.
        for (VendorServiceConnection connection : mConnections.values()) {
            int connectedUserId = connection.mUser.getIdentifier();
            if (!isUserInScope(connectedUserId, connection.mVendorServiceInfo, mCarUserService,
                    currentUserId)) {
                connection.stopOrUnbindService();
            }
        }

        if (userId != UserHandle.SYSTEM.getIdentifier()) {
            startOrBindServicesForUser(UserHandle.of(userId), /* forPostUnlock= */ null);
        } else {
            Slogf.wtf(TAG, "Unexpected to receive switch user event for system user");
        }
    }

    private void handleOnUserInvisible(@UserIdInt int userId) {
        if (DBG) {
            Slogf.d(TAG, "handleOnUserInvisible(): user=%d", userId);
        }

        for (VendorServiceConnection connection : mConnections.values()) {
            VendorServiceInfo serviceInfo = connection.mVendorServiceInfo;
            if (connection.isUser(userId)
                    && (serviceInfo.isVisibleUserService()
                            || serviceInfo.isBackgroundVisibleUserService())
                    && !serviceInfo.isAllUserService()) {
                connection.stopOrUnbindService();
            }
        }
    }

    private void handleOnUserVisible(@UserIdInt int userId) {
        if (DBG) {
            Slogf.d(TAG, "handleOnUserVisible(): user=%d", userId);
        }

        startOrBindServicesForUser(UserHandle.of(userId), /* forPostUnlock= */ null);
    }

    private void handleOnUserUnlocked(@UserIdInt int userId, boolean forPostUnlock) {
        if (DBG) {
            Slogf.d(TAG, "handleOnUserUnlocked(): user=%d", userId);
        }

        startOrBindServicesForUser(UserHandle.of(userId), forPostUnlock);
    }

    private void startOrBindServicesForUser(UserHandle user, @Nullable Boolean forPostUnlock) {
        int userId = user.getIdentifier();
        if (!mUserManager.isUserRunning(user)) {
            Slogf.w(TAG, "User %d is not running, skip startOrBindServicesForUser", userId);
            return;
        }

        boolean unlocked = mUserManager.isUserUnlockingOrUnlocked(user);
        int currentUserId = mCurrentUserFetcher.getCurrentUser();
        for (VendorServiceInfo service: mVendorServiceInfos) {
            if (forPostUnlock != null
                    && service.shouldStartOnPostUnlock() != forPostUnlock.booleanValue()) {
                continue;
            }

            boolean userScopeChecked = isUserInScope(userId, service, mCarUserService,
                    currentUserId);
            boolean triggerChecked = service.shouldStartAsap() || unlocked;

            if (userScopeChecked && triggerChecked) {
                startOrBindService(service, user);
            }
        }
    }

    @SuppressLint("NewApi")
    private void startOrBindServicesIfNeeded() {
        // Start/bind service for system user.
        startOrBindServicesForUser(UserHandle.SYSTEM, /* forPostUnlock= */ null);

        // Start/bind service for all visible users.
        Set<UserHandle> visibleUsers = mUserManager.getVisibleUsers();
        for (Iterator<UserHandle> iterator = visibleUsers.iterator(); iterator.hasNext();) {
            UserHandle userHandle = iterator.next();
            startOrBindServicesForUser(userHandle, /* forPostUnlock= */ null);
        }
    }

    private void startOrBindService(VendorServiceInfo service, UserHandle user) {
        ConnectionKey key = ConnectionKey.of(service, user);
        VendorServiceConnection connection = getOrCreateConnection(key);
        if (!connection.startOrBindService()) {
            Slogf.e(TAG, "Failed to start or bind service " + service);
            mConnections.remove(key);
        }
    }

    private void stopOrUnbindService(VendorServiceInfo service, UserHandle user) {
        ConnectionKey key = ConnectionKey.of(service, user);
        VendorServiceConnection connection = mConnections.get(key);
        if (connection != null) {
            connection.stopOrUnbindService();
        }
    }

    /**
     * Unbinds the VendorServiceController from all the services with the given {@code packageName}
     * and running as {@code userId}.
     */
    private void stopOrUnbindService(String packageName, @UserIdInt int userId) {
        for (VendorServiceConnection connection : mConnections.values()) {
            if (connection.isUser(userId)
                    && packageName.equals(connection.mVendorServiceInfo.getIntent().getComponent()
                    .getPackageName())) {
                Slogf.d(TAG, "Stopping the connection to service %s",
                         connection.mVendorServiceInfo);
                connection.stopOrUnbindService();
            }
        }
    }

    private VendorServiceConnection getOrCreateConnection(ConnectionKey key) {
        VendorServiceConnection connection = mConnections.get(key);
        if (connection == null) {
            connection = new VendorServiceConnection(mContext, mHandler, key.mVendorServiceInfo,
                    key.mUserHandle, mCurrentUserFetcher);
            mConnections.put(key, connection);
        }

        return connection;
    }

    /** Loads data from XML resources and returns true if any services needs to be started/bound. */
    private boolean loadXmlConfiguration() {
        final Resources res = mContext.getResources();
        for (String rawServiceInfo: res.getStringArray(R.array.config_earlyStartupServices)) {
            if (TextUtils.isEmpty(rawServiceInfo)) {
                continue;
            }
            VendorServiceInfo service = VendorServiceInfo.parse(rawServiceInfo);
            mVendorServiceInfos.add(service);
            if (DBG) {
                Slogf.i(TAG, "Registered vendor service: " + service);
            }
        }
        Slogf.i(TAG, "Found " + mVendorServiceInfos.size()
                + " services to be started/bound");

        return !mVendorServiceInfos.isEmpty();
    }

    /**
     * Represents connection to the vendor service.
     */
    @VisibleForTesting
    public static final class VendorServiceConnection implements ServiceConnection, Executor {
        private static final int INITIAL_REBIND_DELAY_MS = 4000; // 4 sec.
        private static final int DEFAULT_FAILURE_COUNTER_RESET_TIMEOUT = 5 * 60 * 1000; // 5 min.
        private static final int MSG_REBIND = 0;
        private static final int MSG_FAILURE_COUNTER_RESET = 1;

        private int mRecentFailures = 0;
        private boolean mBound = false;
        private boolean mStarted = false;
        private boolean mStopRequested = false;
        private final VendorServiceInfo mVendorServiceInfo;
        private final UserHandle mUser;
        private final CarUserService mCarUserService;
        private final Context mUserContext;
        private final Handler mHandler;
        private final Handler mFailureHandler;
        private final CurrentUserFetcher mCurrentUserFetcher;

        VendorServiceConnection(Context context, Handler handler,
                VendorServiceInfo vendorServiceInfo, UserHandle user,
                CurrentUserFetcher currentUserFetcher) {
            mHandler = handler;
            mVendorServiceInfo = vendorServiceInfo;
            mUser = user;
            mUserContext = context.createContextAsUser(mUser, /* flags= */ 0);
            mCarUserService = CarLocalServices.getService(CarUserService.class);
            mCurrentUserFetcher = currentUserFetcher;

            mFailureHandler = new Handler(handler.getLooper()) {
                @Override
                public void handleMessage(Message msg) {
                    handleFailureMessage(msg);
                }
            };
        }

        @Override
        public String toString() {
            return "VendorServiceConnection[user=" + mUser
                    + ", service=" + mVendorServiceInfo + "]";
        }

        @ExcludeFromCodeCoverageGeneratedReport(reason = DUMP_INFO)
        public void dump(PrintWriter writer) {
            writer.printf("%s, mRecentFailures=%d, mBound=%b, mStarted=%b, mStopRequested=%b\n",
                    toString(), mRecentFailures, mBound, mStarted, mStopRequested);
        }

        private boolean isUser(@UserIdInt int userId) {
            return mUser.getIdentifier() == userId;
        }

        boolean startOrBindService() {
            if (mStarted || mBound) {
                return true;  // Already started or bound
            }

            if (DBG) {
                Slogf.d(TAG, "startOrBindService "
                        + mVendorServiceInfo.toShortString() + ", as user: " + mUser + ", bind: "
                        + mVendorServiceInfo.shouldBeBound());
            }
            mStopRequested = false;

            Intent intent = mVendorServiceInfo.getIntent();
            if (mVendorServiceInfo.shouldBeBound()) {
                boolean canBind = mUserContext.bindService(intent, BIND_AUTO_CREATE,
                        /* executor= */ this, /* conn= */ this);
                if (!canBind) {
                    // Still need to unbind when an attempt to bind fails.
                    try {
                        unbindService();
                    } catch (Exception e) {
                        // When binding already failed, log and ignore an exception from unbind.
                        Slogf.w(TAG, "After bindService() failed, unbindService() threw "
                                + "an exception:", e);
                    }
                }
                return canBind;
            } else if (mVendorServiceInfo.shouldBeStartedInForeground()) {
                try {
                    mStarted = mUserContext.startForegroundService(intent) != null;
                } catch (SecurityException e) {
                    Slogf.e(TAG, "ERROR: Failed to start fg service : " + e);
                    mStarted = false;
                }
                return mStarted;
            } else {
                try {
                    mStarted = mUserContext.startService(intent) != null;
                } catch (SecurityException e) {
                    Slogf.e(TAG, "ERROR: Failed to start service : " + e);
                    mStarted = false;
                }
                return mStarted;
            }
        }

        void stopOrUnbindService() {
            mStopRequested = true;
            if (mStarted) {
                if (DBG) Slogf.d(TAG, "Stopping %s", this);
                mUserContext.stopService(mVendorServiceInfo.getIntent());
                mStarted = false;
            } else if (mBound) {
                unbindService();
                mBound = false;
            }
        }

        private void unbindService() {
            if (DBG) Slogf.d(TAG, "Unbinding %s", this);
            mUserContext.unbindService(this);
        }

        @Override // From Executor
        public void execute(Runnable command) {
            mHandler.post(command);
        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mBound = true;
            if (DBG) {
                Slogf.d(TAG, "onServiceConnected, name: %s", name);
            }
            if (mStopRequested) {
                stopOrUnbindService();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            if (DBG) {
                Slogf.d(TAG, "onServiceDisconnected, name: " + name);
            }
            // A binding is persistent, and the service will be reconnected by the binder.
            // Therefore, there is no need to attempt to rebind or reconnect here.
        }

        @Override
        public void onBindingDied(ComponentName name) {
            mBound = false;
            if (DBG) {
                Slogf.d(TAG, "onBindingDied, name: " + name);
            }
            // When a binding died, first unbind the connection and then rebind.
            unbindService();
            tryToRebind();
        }

        @Override
        public void onNullBinding(ComponentName name) {
            // Null binding means that the attempted service will never become usable.
            if (DBG) {
                Slogf.d(TAG, "onNullBinding, name: " + name);
            }
            // Still need to unbind to release resource associated with the connection.
            unbindService();
        }

        private void tryToRebind() {
            if (mStopRequested) {
                return;
            }

            if (mFailureHandler.hasMessages(MSG_REBIND)) {
                if (DBG) {
                    Slogf.d(TAG, "Rebind already scheduled for "
                            + mVendorServiceInfo.toShortString());
                }
                return;
            }

            int currentUserId = mCurrentUserFetcher.getCurrentUser();
            if (isUserInScope(mUser.getIdentifier(), mVendorServiceInfo, mCarUserService,
                    currentUserId)) {
                // Double the delay after each failure.
                int rebindDelay = INITIAL_REBIND_DELAY_MS * (1 << mRecentFailures);
                Slogf.i(TAG, "tryToRebind(): after " + mRecentFailures + " recent failures,"
                        + " trying to rebind service " + mVendorServiceInfo.toShortString()
                        + " for user " + mUser.getIdentifier() + " in " + rebindDelay + "ms");
                mFailureHandler.sendMessageDelayed(
                        mFailureHandler.obtainMessage(MSG_REBIND), rebindDelay);
                scheduleResetFailureCounter();
            } else {
                Slogf.w(TAG, "No need to rebind anymore as the service no longer satisfies "
                        + " the user scope.");
            }
        }

        private void scheduleResetFailureCounter() {
            mFailureHandler.removeMessages(MSG_FAILURE_COUNTER_RESET);
            // Reset the failure counter after the timeout. We take the max, to ensure
            // that we are not resetting the counter before exhausting all retries.
            int failureCounterResetTimeout =
                    INITIAL_REBIND_DELAY_MS * (1 << (mVendorServiceInfo.getMaxRetries() + 1));
            failureCounterResetTimeout =
                    failureCounterResetTimeout > DEFAULT_FAILURE_COUNTER_RESET_TIMEOUT
                            ? failureCounterResetTimeout : DEFAULT_FAILURE_COUNTER_RESET_TIMEOUT;
            mFailureHandler.sendMessageDelayed(
                    mFailureHandler.obtainMessage(MSG_FAILURE_COUNTER_RESET),
                    failureCounterResetTimeout);
        }

        private void handleFailureMessage(Message msg) {
            switch (msg.what) {
                case MSG_REBIND: {
                    if (mBound) {
                        Slogf.d(TAG, "Service " + mVendorServiceInfo.toShortString()
                                + " is already bound. Ignoring MSG_REBIND");
                    } else if (mRecentFailures < mVendorServiceInfo.getMaxRetries()) {
                        Slogf.i(TAG, "Attempting to rebind to the service "
                                + mVendorServiceInfo.toShortString() + " (" + (mRecentFailures + 1)
                                + " out of " + mVendorServiceInfo.getMaxRetries() + " max tries)");
                        ++mRecentFailures;
                        startOrBindService();
                    } else {
                        Slogf.w(TAG, "Exceeded maximum number of attempts ("
                                + mVendorServiceInfo.getMaxRetries() + ") to rebind to the service "
                                + mVendorServiceInfo.toShortString());
                    }
                    break;
                }
                case MSG_FAILURE_COUNTER_RESET:
                    mRecentFailures = 0;
                    break;
                default:
                    Slogf.e(TAG, "Unexpected message received in failure handler: " + msg.what);
            }
        }
    }

    /** Defines a key in the HashMap to store connection on per user and vendor service basis */
    private static class ConnectionKey {
        private final UserHandle mUserHandle;
        private final VendorServiceInfo mVendorServiceInfo;

        private ConnectionKey(VendorServiceInfo service, UserHandle user) {
            mVendorServiceInfo = service;
            mUserHandle = user;
        }

        static ConnectionKey of(VendorServiceInfo service, UserHandle user) {
            return new ConnectionKey(service, user);
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (!(o instanceof ConnectionKey)) {
                return false;
            }
            ConnectionKey that = (ConnectionKey) o;
            return Objects.equals(mUserHandle, that.mUserHandle)
                    && Objects.equals(mVendorServiceInfo, that.mVendorServiceInfo);
        }

        @Override
        public int hashCode() {
            return Objects.hash(mUserHandle, mVendorServiceInfo);
        }
    }
}