/*
 * Copyright (C) 2018 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.server.pm;

import android.annotation.NonNull;
import android.annotation.Nullable;
import android.apex.ApexInfo;
import android.apex.ApexInfoList;
import android.apex.ApexSessionInfo;
import android.content.Context;
import android.content.IIntentReceiver;
import android.content.IIntentSender;
import android.content.Intent;
import android.content.IntentSender;
import android.content.pm.PackageInfo;
import android.content.pm.PackageInstaller;
import android.content.pm.PackageInstaller.SessionInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageParser;
import android.content.pm.PackageParser.PackageParserException;
import android.content.pm.PackageParser.SigningDetails;
import android.content.pm.PackageParser.SigningDetails.SignatureSchemeVersion;
import android.content.pm.ParceledListSlice;
import android.content.pm.Signature;
import android.content.rollback.IRollbackManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.ParcelFileDescriptor;
import android.os.ParcelableException;
import android.os.PowerManager;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.util.IntArray;
import android.util.Slog;
import android.util.SparseArray;
import android.util.apk.ApkSignatureVerifier;

import com.android.internal.annotations.GuardedBy;
import com.android.internal.os.BackgroundThread;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.function.Predicate;
import java.util.stream.Collectors;

/**
 * This class handles staged install sessions, i.e. install sessions that require packages to
 * be installed only after a reboot.
 */
public class StagingManager {

    private static final String TAG = "StagingManager";

    private final PackageInstallerService mPi;
    private final ApexManager mApexManager;
    private final PowerManager mPowerManager;
    private final Handler mBgHandler;

    @GuardedBy("mStagedSessions")
    private final SparseArray<PackageInstallerSession> mStagedSessions = new SparseArray<>();

    StagingManager(PackageInstallerService pi, ApexManager am, Context context) {
        mPi = pi;
        mApexManager = am;
        mPowerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        mBgHandler = BackgroundThread.getHandler();
    }

    private void updateStoredSession(@NonNull PackageInstallerSession sessionInfo) {
        synchronized (mStagedSessions) {
            PackageInstallerSession storedSession = mStagedSessions.get(sessionInfo.sessionId);
            // storedSession might be null if a call to abortSession was made before the session
            // is updated.
            if (storedSession != null) {
                mStagedSessions.put(sessionInfo.sessionId, sessionInfo);
            }
        }
    }

    ParceledListSlice<PackageInstaller.SessionInfo> getSessions() {
        final List<PackageInstaller.SessionInfo> result = new ArrayList<>();
        synchronized (mStagedSessions) {
            for (int i = 0; i < mStagedSessions.size(); i++) {
                result.add(mStagedSessions.valueAt(i).generateInfo(false));
            }
        }
        return new ParceledListSlice<>(result);
    }

    private void validateApexSignature(String apexPath, String packageName)
            throws PackageManagerException {
        final SigningDetails signingDetails;
        try {
            signingDetails = ApkSignatureVerifier.verify(apexPath, SignatureSchemeVersion.JAR);
        } catch (PackageParserException e) {
            throw new PackageManagerException(SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                    "Failed to parse APEX package " + apexPath, e);
        }

        final PackageInfo packageInfo = mApexManager.getPackageInfo(packageName,
                ApexManager.MATCH_ACTIVE_PACKAGE);
        if (packageInfo == null) {
            // This should never happen, because submitSessionToApexService ensures that no new
            // apexes were installed.
            throw new IllegalStateException("Unknown apex package " + packageName);
        }

        final SigningDetails existingSigningDetails;
        try {
            existingSigningDetails = ApkSignatureVerifier.verify(
                packageInfo.applicationInfo.sourceDir, SignatureSchemeVersion.JAR);
        } catch (PackageParserException e) {
            throw new PackageManagerException(SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                    "Failed to parse APEX package " + packageInfo.applicationInfo.sourceDir, e);
        }

        // Now that we have both sets of signatures, demand that they're an exact match.
        if (Signature.areExactMatch(existingSigningDetails.signatures, signingDetails.signatures)) {
            return;
        }

        throw new PackageManagerException(SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                "APK-container signature verification failed for package "
                        + packageName + ". Signature of file "
                        + apexPath + " does not match the signature of "
                        + " the package already installed.");
    }

    private List<PackageInfo> submitSessionToApexService(
            @NonNull PackageInstallerSession session) throws PackageManagerException {
        final IntArray childSessionsIds = new IntArray();
        if (session.isMultiPackage()) {
            for (int id : session.getChildSessionIds()) {
                if (isApexSession(mStagedSessions.get(id))) {
                    childSessionsIds.add(id);
                }
            }
        }
        // submitStagedSession will throw a PackageManagerException if apexd verification fails,
        // which will be propagated to populate stagedSessionErrorMessage of this session.
        final ApexInfoList apexInfoList = mApexManager.submitStagedSession(session.sessionId,
                childSessionsIds.toArray());
        final List<PackageInfo> result = new ArrayList<>();
        for (ApexInfo apexInfo : apexInfoList.apexInfos) {
            final PackageInfo packageInfo;
            int flags = PackageManager.GET_META_DATA;
            PackageParser.Package pkg;
            try {
                File apexFile = new File(apexInfo.modulePath);
                PackageParser pp = new PackageParser();
                pkg = pp.parsePackage(apexFile, flags, false);
            } catch (PackageParserException e) {
                throw new PackageManagerException(SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                        "Failed to parse APEX package " + apexInfo.modulePath, e);
            }
            packageInfo = PackageParser.generatePackageInfo(pkg, apexInfo, flags);
            final PackageInfo activePackage = mApexManager.getPackageInfo(packageInfo.packageName,
                    ApexManager.MATCH_ACTIVE_PACKAGE);
            if (activePackage == null) {
                Slog.w(TAG, "Attempting to install new APEX package " + packageInfo.packageName);
                throw new PackageManagerException(SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                        "It is forbidden to install new APEX packages.");
            }
            checkRequiredVersionCode(session, activePackage);
            checkDowngrade(session, activePackage, packageInfo);
            result.add(packageInfo);
        }
        return result;
    }

    private void checkRequiredVersionCode(final PackageInstallerSession session,
            final PackageInfo activePackage) throws PackageManagerException {
        if (session.params.requiredInstalledVersionCode == PackageManager.VERSION_CODE_HIGHEST) {
            return;
        }
        final long activeVersion = activePackage.applicationInfo.longVersionCode;
        if (activeVersion != session.params.requiredInstalledVersionCode) {
            if (!mApexManager.abortActiveSession()) {
                Slog.e(TAG, "Failed to abort apex session " + session.sessionId);
            }
            throw new PackageManagerException(
                    SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                    "Installed version of APEX package " + activePackage.packageName
                            + " does not match required. Active version: " + activeVersion
                            + " required: " + session.params.requiredInstalledVersionCode);
        }
    }

    private void checkDowngrade(final PackageInstallerSession session,
            final PackageInfo activePackage, final PackageInfo newPackage)
            throws PackageManagerException {
        final long activeVersion = activePackage.applicationInfo.longVersionCode;
        final long newVersionCode = newPackage.applicationInfo.longVersionCode;
        boolean allowsDowngrade = PackageManagerServiceUtils.isDowngradePermitted(
                session.params.installFlags, activePackage.applicationInfo.flags);
        if (activeVersion > newVersionCode && !allowsDowngrade) {
            if (!mApexManager.abortActiveSession()) {
                Slog.e(TAG, "Failed to abort apex session " + session.sessionId);
            }
            throw new PackageManagerException(
                    SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                    "Downgrade of APEX package " + newPackage.packageName
                            + " is not allowed. Active version: " + activeVersion
                            + " attempted: " + newVersionCode);
        }
    }

    private static boolean isApexSession(@NonNull PackageInstallerSession session) {
        return (session.params.installFlags & PackageManager.INSTALL_APEX) != 0;
    }

    private void preRebootVerification(@NonNull PackageInstallerSession session) {
        final boolean hasApex = sessionContainsApex(session);
        // APEX checks. For single-package sessions, check if they contain an APEX. For
        // multi-package sessions, find all the child sessions that contain an APEX.
        if (hasApex) {
            try {
                final List<PackageInfo> apexPackages = submitSessionToApexService(session);
                for (PackageInfo apexPackage : apexPackages) {
                    validateApexSignature(apexPackage.applicationInfo.sourceDir,
                            apexPackage.packageName);
                }
            } catch (PackageManagerException e) {
                session.setStagedSessionFailed(e.error, e.getMessage());
                return;
            }
        }

        if (sessionContainsApk(session)) {
            if (!installApksInSession(session, /* preReboot */ true)) {
                session.setStagedSessionFailed(SessionInfo.STAGED_SESSION_VERIFICATION_FAILED,
                        "APK verification failed. Check logcat messages for "
                                + "more information.");
                // TODO(b/118865310): abort the session on apexd.
                return;
            }
        }

        if ((session.params.installFlags & PackageManager.INSTALL_ENABLE_ROLLBACK) != 0) {
            // If rollback is enabled for this session, we call through to the RollbackManager
            // with the list of sessions it must enable rollback for. Note that notifyStagedSession
            // is a synchronous operation.
            final IRollbackManager rm = IRollbackManager.Stub.asInterface(
                    ServiceManager.getService(Context.ROLLBACK_SERVICE));
            try {
                // NOTE: To stay consistent with the non-staged install flow, we don't fail the
                // entire install if rollbacks can't be enabled.
                if (!rm.notifyStagedSession(session.sessionId)) {
                    Slog.e(TAG, "Unable to enable rollback for session: " + session.sessionId);
                }
            } catch (RemoteException re) {
                // Cannot happen, the rollback manager is in the same process.
            }
        }

        // Proactively mark session as ready before calling apexd. Although this call order looks
        // counter-intuitive, this is the easiest way to ensure that session won't end up in the
        // inconsistent state:
        //  - If device gets rebooted right before call to apexd, then apexd will never activate
        //      apex files of this staged session. This will result in StagingManager failing the
        //      session.
        // On the other hand, if the order of the calls was inverted (first call apexd, then mark
        // session as ready), then if a device gets rebooted right after the call to apexd, only
        // apex part of the train will be applied, leaving device in an inconsistent state.
        session.setStagedSessionReady();
        if (!hasApex) {
            // Session doesn't contain apex, nothing to do.
            return;
        }
        try {
            mApexManager.markStagedSessionReady(session.sessionId);
        } catch (PackageManagerException e) {
            session.setStagedSessionFailed(e.error, e.getMessage());
        }
    }


    private boolean sessionContains(@NonNull PackageInstallerSession session,
                                    Predicate<PackageInstallerSession> filter) {
        if (!session.isMultiPackage()) {
            return filter.test(session);
        }
        synchronized (mStagedSessions) {
            return !(Arrays.stream(session.getChildSessionIds())
                    // Retrieve cached sessions matching ids.
                    .mapToObj(i -> mStagedSessions.get(i))
                    // Filter only the ones containing APEX.
                    .filter(childSession -> filter.test(childSession))
                    .collect(Collectors.toList())
                    .isEmpty());
        }
    }

    private boolean sessionContainsApex(@NonNull PackageInstallerSession session) {
        return sessionContains(session, (s) -> isApexSession(s));
    }

    private boolean sessionContainsApk(@NonNull PackageInstallerSession session) {
        return sessionContains(session, (s) -> !isApexSession(s));
    }

    private void resumeSession(@NonNull PackageInstallerSession session) {
        boolean hasApex = sessionContainsApex(session);
        if (hasApex) {
            // Check with apexservice whether the apex packages have been activated.
            ApexSessionInfo apexSessionInfo = mApexManager.getStagedSessionInfo(session.sessionId);
            if (apexSessionInfo == null) {
                session.setStagedSessionFailed(SessionInfo.STAGED_SESSION_ACTIVATION_FAILED,
                        "apexd did not know anything about a staged session supposed to be"
                        + "activated");
                return;
            }
            if (isApexSessionFailed(apexSessionInfo)) {
                session.setStagedSessionFailed(SessionInfo.STAGED_SESSION_ACTIVATION_FAILED,
                        "APEX activation failed. Check logcat messages from apexd for "
                                + "more information.");
                return;
            }
            if (apexSessionInfo.isVerified) {
                // Session has been previously submitted to apexd, but didn't complete all the
                // pre-reboot verification, perhaps because the device rebooted in the meantime.
                // Greedily re-trigger the pre-reboot verification.
                Slog.d(TAG, "Found pending staged session " + session.sessionId + " still to be "
                        + "verified, resuming pre-reboot verification");
                mBgHandler.post(() -> preRebootVerification(session));
                return;
            }
            if (!apexSessionInfo.isActivated && !apexSessionInfo.isSuccess) {
                // In all the remaining cases apexd will try to apply the session again at next
                // boot. Nothing to do here for now.
                Slog.w(TAG, "Staged session " + session.sessionId + " scheduled to be applied "
                        + "at boot didn't activate nor fail. This usually means that apexd will "
                        + "retry at next reboot.");
                return;
            }
        }
        // The APEX part of the session is activated, proceed with the installation of APKs.
        if (!installApksInSession(session, /* preReboot */ false)) {
            session.setStagedSessionFailed(SessionInfo.STAGED_SESSION_ACTIVATION_FAILED,
                    "Staged installation of APKs failed. Check logcat messages for"
                        + "more information.");

            if (!hasApex) {
                return;
            }

            if (!mApexManager.abortActiveSession()) {
                Slog.e(TAG, "Failed to abort APEXd session");
            } else {
                Slog.e(TAG,
                        "Successfully aborted apexd session. Rebooting device in order to revert "
                                + "to the previous state of APEXd.");
                mPowerManager.reboot(null);
            }
            return;
        }

        session.setStagedSessionApplied();
        if (hasApex) {
            mApexManager.markStagedSessionSuccessful(session.sessionId);
        }
    }

    private List<String> findAPKsInDir(File stageDir) {
        List<String> ret = new ArrayList<>();
        if (stageDir != null && stageDir.exists()) {
            for (File file : stageDir.listFiles()) {
                if (file.getAbsolutePath().toLowerCase().endsWith(".apk")) {
                    ret.add(file.getAbsolutePath());
                }
            }
        }
        return ret;
    }

    private PackageInstallerSession createAndWriteApkSession(
            @NonNull PackageInstallerSession originalSession, boolean preReboot) {
        if (originalSession.stageDir == null) {
            Slog.wtf(TAG, "Attempting to install a staged APK session with no staging dir");
            return null;
        }
        List<String> apkFilePaths = findAPKsInDir(originalSession.stageDir);
        if (apkFilePaths.isEmpty()) {
            Slog.w(TAG, "Can't find staged APK in " + originalSession.stageDir.getAbsolutePath());
            return null;
        }

        PackageInstaller.SessionParams params = originalSession.params.copy();
        params.isStaged = false;
        params.installFlags |= PackageManager.INSTALL_STAGED;
        // TODO(b/129744602): use the userid from the original session.
        if (preReboot) {
            params.installFlags &= ~PackageManager.INSTALL_ENABLE_ROLLBACK;
            params.installFlags |= PackageManager.INSTALL_DRY_RUN;
        } else {
            params.installFlags |= PackageManager.INSTALL_DISABLE_VERIFICATION;
        }
        try {
            int apkSessionId = mPi.createSession(
                    params, originalSession.getInstallerPackageName(),
                    0 /* UserHandle.SYSTEM */);
            PackageInstallerSession apkSession = mPi.getSession(apkSessionId);
            apkSession.open();
            for (String apkFilePath : apkFilePaths) {
                File apkFile = new File(apkFilePath);
                ParcelFileDescriptor pfd = ParcelFileDescriptor.open(apkFile,
                        ParcelFileDescriptor.MODE_READ_ONLY);
                long sizeBytes = (pfd == null) ? -1 : pfd.getStatSize();
                if (sizeBytes < 0) {
                    Slog.e(TAG, "Unable to get size of: " + apkFilePath);
                    return null;
                }
                apkSession.write(apkFile.getName(), 0, sizeBytes, pfd);
            }
            return apkSession;
        } catch (IOException | ParcelableException e) {
            Slog.e(TAG, "Failure to install APK staged session " + originalSession.sessionId, e);
            return null;
        }
    }

    private boolean commitApkSession(@NonNull PackageInstallerSession apkSession,
                                     int originalSessionId, boolean preReboot) {

        if (!preReboot) {
            if ((apkSession.params.installFlags & PackageManager.INSTALL_ENABLE_ROLLBACK) != 0) {
                // If rollback is available for this session, notify the rollback
                // manager of the apk session so it can properly enable rollback.
                final IRollbackManager rm = IRollbackManager.Stub.asInterface(
                        ServiceManager.getService(Context.ROLLBACK_SERVICE));
                try {
                    rm.notifyStagedApkSession(originalSessionId, apkSession.sessionId);
                } catch (RemoteException re) {
                    // Cannot happen, the rollback manager is in the same process.
                }
            }
        }

        final LocalIntentReceiver receiver = new LocalIntentReceiver();
        apkSession.commit(receiver.getIntentSender(), false);
        final Intent result = receiver.getResult();
        final int status = result.getIntExtra(PackageInstaller.EXTRA_STATUS,
                PackageInstaller.STATUS_FAILURE);
        if (status == PackageInstaller.STATUS_SUCCESS) {
            return true;
        }
        Slog.e(TAG, "Failure to install APK staged session " + originalSessionId + " ["
                + result.getStringExtra(PackageInstaller.EXTRA_STATUS_MESSAGE) + "]");
        return false;
    }

    private boolean installApksInSession(@NonNull PackageInstallerSession session,
                                         boolean preReboot) {
        if (!session.isMultiPackage() && !isApexSession(session)) {
            // APK single-packaged staged session. Do a regular install.
            PackageInstallerSession apkSession = createAndWriteApkSession(session, preReboot);
            if (apkSession == null) {
                return false;
            }
            return commitApkSession(apkSession, session.sessionId, preReboot);
        } else if (session.isMultiPackage()) {
            // For multi-package staged sessions containing APKs, we identify which child sessions
            // contain an APK, and with those then create a new multi-package group of sessions,
            // carrying over all the session parameters and unmarking them as staged. On commit the
            // sessions will be installed atomically.
            List<PackageInstallerSession> childSessions;
            synchronized (mStagedSessions) {
                childSessions =
                        Arrays.stream(session.getChildSessionIds())
                                // Retrieve cached sessions matching ids.
                                .mapToObj(i -> mStagedSessions.get(i))
                                // Filter only the ones containing APKs.s
                                .filter(childSession -> !isApexSession(childSession))
                                .collect(Collectors.toList());
            }
            if (childSessions.isEmpty()) {
                // APEX-only multi-package staged session, nothing to do.
                return true;
            }
            PackageInstaller.SessionParams params = session.params.copy();
            params.isStaged = false;
            if (preReboot) {
                params.installFlags &= ~PackageManager.INSTALL_ENABLE_ROLLBACK;
            }
            // TODO(b/129744602): use the userid from the original session.
            int apkParentSessionId = mPi.createSession(
                    params, session.getInstallerPackageName(),
                    0 /* UserHandle.SYSTEM */);
            PackageInstallerSession apkParentSession = mPi.getSession(apkParentSessionId);
            try {
                apkParentSession.open();
            } catch (IOException e) {
                Slog.e(TAG, "Unable to prepare multi-package session for staged session "
                        + session.sessionId);
                return false;
            }

            for (PackageInstallerSession sessionToClone : childSessions) {
                PackageInstallerSession apkChildSession =
                        createAndWriteApkSession(sessionToClone, preReboot);
                if (apkChildSession == null) {
                    return false;
                }
                try {
                    apkParentSession.addChildSessionId(apkChildSession.sessionId);
                } catch (IllegalStateException e) {
                    Slog.e(TAG, "Failed to add a child session for installing the APK files", e);
                    return false;
                }
            }
            return commitApkSession(apkParentSession, session.sessionId, preReboot);
        }
        // APEX single-package staged session, nothing to do.
        return true;
    }

    void commitSession(@NonNull PackageInstallerSession session) {
        updateStoredSession(session);
        mBgHandler.post(() -> preRebootVerification(session));
    }

    @Nullable
    PackageInstallerSession getActiveSession() {
        synchronized (mStagedSessions) {
            for (int i = 0; i < mStagedSessions.size(); i++) {
                final PackageInstallerSession session = mStagedSessions.valueAt(i);
                if (!session.isCommitted()) {
                    continue;
                }
                if (session.hasParentSessionId()) {
                    // Staging manager will finalize only parent session. Ignore child sessions
                    // picking the active.
                    continue;
                }
                if (!session.isStagedSessionApplied() && !session.isStagedSessionFailed()) {
                    return session;
                }
            }
        }
        return null;
    }

    void createSession(@NonNull PackageInstallerSession sessionInfo) {
        synchronized (mStagedSessions) {
            mStagedSessions.append(sessionInfo.sessionId, sessionInfo);
        }
    }

    void abortSession(@NonNull PackageInstallerSession session) {
        synchronized (mStagedSessions) {
            mStagedSessions.remove(session.sessionId);
        }
    }

    void abortCommittedSession(@NonNull PackageInstallerSession session) {
        if (session.isStagedSessionApplied()) {
            Slog.w(TAG, "Cannot abort applied session : " + session.sessionId);
            return;
        }
        abortSession(session);

        boolean hasApex = sessionContainsApex(session);
        if (hasApex) {
            ApexSessionInfo apexSession = mApexManager.getStagedSessionInfo(session.sessionId);
            if (apexSession == null || isApexSessionFinalized(apexSession)) {
                Slog.w(TAG,
                        "Cannot abort session because it is not active or APEXD is not reachable");
                return;
            }
            mApexManager.abortActiveSession();
        }
    }

    private boolean isApexSessionFinalized(ApexSessionInfo session) {
        /* checking if the session is in a final state, i.e., not active anymore */
        return session.isUnknown || session.isActivationFailed || session.isSuccess
                || session.isRolledBack;
    }

    private static boolean isApexSessionFailed(ApexSessionInfo apexSessionInfo) {
        // isRollbackInProgress is included to cover the scenario, when a device is rebooted in
        // during the rollback, and apexd fails to resume the rollback after reboot.
        return apexSessionInfo.isActivationFailed || apexSessionInfo.isUnknown
                || apexSessionInfo.isRolledBack || apexSessionInfo.isRollbackInProgress
                || apexSessionInfo.isRollbackFailed;
    }

    @GuardedBy("mStagedSessions")
    private boolean isMultiPackageSessionComplete(@NonNull PackageInstallerSession session) {
        // This method assumes that the argument is either a parent session of a multi-package
        // i.e. isMultiPackage() returns true, or that it is a child session, i.e.
        // hasParentSessionId() returns true.
        if (session.isMultiPackage()) {
            // Parent session of a multi-package group. Check that we restored all the children.
            for (int childSession : session.getChildSessionIds()) {
                if (mStagedSessions.get(childSession) == null) {
                    return false;
                }
            }
            return true;
        }
        if (session.hasParentSessionId()) {
            PackageInstallerSession parent = mStagedSessions.get(session.getParentSessionId());
            if (parent == null) {
                return false;
            }
            return isMultiPackageSessionComplete(parent);
        }
        Slog.wtf(TAG, "Attempting to restore an invalid multi-package session.");
        return false;
    }

    void restoreSession(@NonNull PackageInstallerSession session) {
        PackageInstallerSession sessionToResume = session;
        synchronized (mStagedSessions) {
            mStagedSessions.append(session.sessionId, session);
            // For multi-package sessions, we don't know in which order they will be restored. We
            // need to wait until we have restored all the session in a group before restoring them.
            if (session.isMultiPackage() || session.hasParentSessionId()) {
                if (!isMultiPackageSessionComplete(session)) {
                    // Still haven't recovered all sessions of the group, return.
                    return;
                }
                // Group recovered, find the parent if necessary and resume the installation.
                if (session.hasParentSessionId()) {
                    sessionToResume = mStagedSessions.get(session.getParentSessionId());
                }
            }
        }
        checkStateAndResume(sessionToResume);
    }

    private void checkStateAndResume(@NonNull PackageInstallerSession session) {
        if (!session.isCommitted()) {
            // Session hasn't been committed yet, ignore.
            return;
        }
        // Check the state of the session and decide what to do next.
        if (session.isStagedSessionFailed() || session.isStagedSessionApplied()) {
            // Final states, nothing to do.
            return;
        }
        if (!session.isStagedSessionReady()) {
            // The framework got restarted before the pre-reboot verification could complete,
            // restart the verification.
            mBgHandler.post(() -> preRebootVerification(session));
        } else {
            // Session had already being marked ready. Start the checks to verify if there is any
            // follow-up work.
            resumeSession(session);
        }
    }

    private static class LocalIntentReceiver {
        private final LinkedBlockingQueue<Intent> mResult = new LinkedBlockingQueue<>();

        private IIntentSender.Stub mLocalSender = new IIntentSender.Stub() {
            @Override
            public void send(int code, Intent intent, String resolvedType, IBinder whitelistToken,
                             IIntentReceiver finishedReceiver, String requiredPermission,
                             Bundle options) {
                try {
                    mResult.offer(intent, 5, TimeUnit.SECONDS);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            }
        };

        public IntentSender getIntentSender() {
            return new IntentSender((IIntentSender) mLocalSender);
        }

        public Intent getResult() {
            try {
                return mResult.take();
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
    }
}