/*
 * Copyright (C) 2008 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 android.net.wifi;

import static android.Manifest.permission.NEARBY_WIFI_DEVICES;

import android.Manifest;
import android.annotation.CallbackExecutor;
import android.annotation.IntDef;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.RequiresPermission;
import android.annotation.SuppressLint;
import android.annotation.SystemApi;
import android.annotation.SystemService;
import android.content.Context;
import android.os.Binder;
import android.os.Build;
import android.os.Bundle;
import android.os.Looper;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.Process;
import android.os.RemoteException;
import android.os.WorkSource;
import android.text.TextUtils;
import android.util.Log;

import androidx.annotation.RequiresApi;

import com.android.internal.util.Protocol;
import com.android.modules.utils.build.SdkLevel;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.Executor;

/**
 * This class provides a way to scan the Wifi universe around the device
 * @hide
 */
@SystemApi
@SystemService(Context.WIFI_SCANNING_SERVICE)
public class WifiScanner {

    /** @hide */
    public static final int WIFI_BAND_INDEX_24_GHZ = 0;
    /** @hide */
    public static final int WIFI_BAND_INDEX_5_GHZ = 1;
    /** @hide */
    public static final int WIFI_BAND_INDEX_5_GHZ_DFS_ONLY = 2;
    /** @hide */
    public static final int WIFI_BAND_INDEX_6_GHZ = 3;
    /** @hide */
    public static final int WIFI_BAND_INDEX_60_GHZ = 4;
    /** @hide */
    public static final int WIFI_BAND_COUNT = 5;

    /** @hide */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef(prefix = {"WIFI_BAND_INDEX_"}, value = {
            WIFI_BAND_INDEX_24_GHZ,
            WIFI_BAND_INDEX_5_GHZ,
            WIFI_BAND_INDEX_5_GHZ_DFS_ONLY,
            WIFI_BAND_INDEX_6_GHZ,
            WIFI_BAND_INDEX_60_GHZ})
    public @interface WifiBandIndex {}

    /** no band specified; use channel list instead */
    public static final int WIFI_BAND_UNSPECIFIED = 0;
    /** 2.4 GHz band */
    public static final int WIFI_BAND_24_GHZ = 1 << WIFI_BAND_INDEX_24_GHZ;
    /** 5 GHz band excluding DFS channels */
    public static final int WIFI_BAND_5_GHZ = 1 << WIFI_BAND_INDEX_5_GHZ;
    /** DFS channels from 5 GHz band only */
    public static final int WIFI_BAND_5_GHZ_DFS_ONLY  = 1 << WIFI_BAND_INDEX_5_GHZ_DFS_ONLY;
    /** 6 GHz band */
    public static final int WIFI_BAND_6_GHZ = 1 << WIFI_BAND_INDEX_6_GHZ;
    /** 60 GHz band */
    public static final int WIFI_BAND_60_GHZ = 1 << WIFI_BAND_INDEX_60_GHZ;

    /**
     * Combination of bands
     * Note that those are only the common band combinations,
     * other combinations can be created by combining any of the basic bands above
     */
    /** Both 2.4 GHz band and 5 GHz band; no DFS channels */
    public static final int WIFI_BAND_BOTH = WIFI_BAND_24_GHZ | WIFI_BAND_5_GHZ;
    /**
     * 2.4Ghz band + DFS channels from 5 GHz band only
     * @hide
     */
    public static final int WIFI_BAND_24_GHZ_WITH_5GHZ_DFS  =
            WIFI_BAND_24_GHZ | WIFI_BAND_5_GHZ_DFS_ONLY;
    /** 5 GHz band including DFS channels */
    public static final int WIFI_BAND_5_GHZ_WITH_DFS  = WIFI_BAND_5_GHZ | WIFI_BAND_5_GHZ_DFS_ONLY;
    /** Both 2.4 GHz band and 5 GHz band; with DFS channels */
    public static final int WIFI_BAND_BOTH_WITH_DFS =
            WIFI_BAND_24_GHZ | WIFI_BAND_5_GHZ | WIFI_BAND_5_GHZ_DFS_ONLY;
    /** 2.4 GHz band and 5 GHz band (no DFS channels) and 6 GHz */
    public static final int WIFI_BAND_24_5_6_GHZ = WIFI_BAND_BOTH | WIFI_BAND_6_GHZ;
    /** 2.4 GHz band and 5 GHz band; with DFS channels and 6 GHz */
    public static final int WIFI_BAND_24_5_WITH_DFS_6_GHZ =
            WIFI_BAND_BOTH_WITH_DFS | WIFI_BAND_6_GHZ;
    /** @hide */
    public static final int WIFI_BAND_24_5_6_60_GHZ =
            WIFI_BAND_24_5_6_GHZ | WIFI_BAND_60_GHZ;
    /** @hide */
    public static final int WIFI_BAND_24_5_WITH_DFS_6_60_GHZ =
            WIFI_BAND_24_5_6_60_GHZ | WIFI_BAND_5_GHZ_DFS_ONLY;

    /** @hide */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef(prefix = {"WIFI_BAND_"}, value = {
            WIFI_BAND_UNSPECIFIED,
            WIFI_BAND_24_GHZ,
            WIFI_BAND_5_GHZ,
            WIFI_BAND_BOTH,
            WIFI_BAND_5_GHZ_DFS_ONLY,
            WIFI_BAND_24_GHZ_WITH_5GHZ_DFS,
            WIFI_BAND_5_GHZ_WITH_DFS,
            WIFI_BAND_BOTH_WITH_DFS,
            WIFI_BAND_6_GHZ,
            WIFI_BAND_24_5_6_GHZ,
            WIFI_BAND_24_5_WITH_DFS_6_GHZ,
            WIFI_BAND_60_GHZ,
            WIFI_BAND_24_5_6_60_GHZ,
            WIFI_BAND_24_5_WITH_DFS_6_60_GHZ})
    public @interface WifiBand {}

    /**
     * All bands
     * @hide
     */
    public static final int WIFI_BAND_ALL = (1 << WIFI_BAND_COUNT) - 1;

    /** Minimum supported scanning period */
    public static final int MIN_SCAN_PERIOD_MS = 1000;
    /** Maximum supported scanning period */
    public static final int MAX_SCAN_PERIOD_MS = 1024000;

    /** No Error */
    public static final int REASON_SUCCEEDED = 0;
    /** Unknown error */
    public static final int REASON_UNSPECIFIED = -1;
    /** Invalid listener */
    public static final int REASON_INVALID_LISTENER = -2;
    /** Invalid request */
    public static final int REASON_INVALID_REQUEST = -3;
    /** Invalid request */
    public static final int REASON_NOT_AUTHORIZED = -4;
    /** An outstanding request with the same listener hasn't finished yet. */
    public static final int REASON_DUPLICATE_REQEUST = -5;
    /** Busy - Due to Connection in progress, processing another scan request etc. */
    public static final int REASON_BUSY = -6;
    /** Abort - Due to another high priority operation like roaming, offload scan etc. */
    public static final int REASON_ABORT = -7;
    /** No such device - Wrong interface or interface doesn't exist. */
    public static final int REASON_NO_DEVICE = -8;
    /** Invalid argument - Wrong/unsupported argument passed in scan params. */
    public static final int REASON_INVALID_ARGS = -9;
    /** Timeout - Device didn't respond back with scan results */
    public static final int REASON_TIMEOUT = -10;

    /** @hide */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef(prefix = { "REASON_" }, value = {
            REASON_SUCCEEDED,
            REASON_UNSPECIFIED,
            REASON_INVALID_LISTENER,
            REASON_INVALID_REQUEST,
            REASON_NOT_AUTHORIZED,
            REASON_DUPLICATE_REQEUST,
            REASON_BUSY,
            REASON_ABORT,
            REASON_NO_DEVICE,
            REASON_INVALID_ARGS,
            REASON_TIMEOUT,
    })
    public @interface ScanStatusCode {}

    /** @hide */
    public static final String GET_AVAILABLE_CHANNELS_EXTRA = "Channels";

    /**
     * This constant is used for {@link ScanSettings#setRnrSetting(int)}.
     * <p>
     * Scan 6Ghz APs co-located with 2.4/5Ghz APs using Reduced Neighbor Report (RNR) if the 6Ghz
     * band is explicitly requested to be scanned and the current country code supports scanning
     * of at least one 6Ghz channel. The 6Ghz band is explicitly requested if the
     * ScanSetting.band parameter is set to one of:
     * <li> {@link #WIFI_BAND_6_GHZ} </li>
     * <li> {@link #WIFI_BAND_24_5_6_GHZ} </li>
     * <li> {@link #WIFI_BAND_24_5_WITH_DFS_6_GHZ} </li>
     * <li> {@link #WIFI_BAND_24_5_6_60_GHZ} </li>
     * <li> {@link #WIFI_BAND_24_5_WITH_DFS_6_60_GHZ} </li>
     * <li> {@link #WIFI_BAND_ALL} </li>
     **/
    public static final int WIFI_RNR_ENABLED_IF_WIFI_BAND_6_GHZ_SCANNED = 0;
    /**
     * This constant is used for {@link ScanSettings#setRnrSetting(int)}.
     * <p>
     * Request to scan 6Ghz APs co-located with 2.4/5Ghz APs using Reduced Neighbor Report (RNR)
     * when the current country code supports scanning of at least one 6Ghz channel.
     **/
    public static final int WIFI_RNR_ENABLED = 1;
    /**
     * This constant is used for {@link ScanSettings#setRnrSetting(int)}.
     * <p>
     * Do not request to scan 6Ghz APs co-located with 2.4/5Ghz APs using
     * Reduced Neighbor Report (RNR)
     **/
    public static final int WIFI_RNR_NOT_NEEDED = 2;

    /** @hide */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef(prefix = {"RNR_"}, value = {
            WIFI_RNR_ENABLED_IF_WIFI_BAND_6_GHZ_SCANNED,
            WIFI_RNR_ENABLED,
            WIFI_RNR_NOT_NEEDED})
    public @interface RnrSetting {}

    /**
     * Maximum length in bytes of all vendor specific information elements (IEs) allowed to set.
     * @hide
     */
    public static final int WIFI_SCANNER_SETTINGS_VENDOR_ELEMENTS_MAX_LEN = 512;

    /**
     * Information Element head: id (1 byte) + length (1 byte)
     * @hide
     */
    public static final int WIFI_IE_HEAD_LEN = 2;

    /**
     * Generic action callback invocation interface
     *  @hide
     */
    @SystemApi
    public static interface ActionListener {
        public void onSuccess();
        public void onFailure(int reason, String description);
    }

    /**
     * Test if scan is a full scan. i.e. scanning all available bands.
     * For backward compatibility, since some apps don't include 6GHz or 60Ghz in their requests
     * yet, lacking 6GHz or 60Ghz band does not cause the result to be false.
     *
     * @param bandsScanned bands that are fully scanned
     * @param excludeDfs when true, DFS band is excluded from the check
     * @return true if all bands are scanned, false otherwise
     *
     * @hide
     */
    public static boolean isFullBandScan(@WifiBand int bandsScanned, boolean excludeDfs) {
        return (bandsScanned | WIFI_BAND_6_GHZ | WIFI_BAND_60_GHZ
                | (excludeDfs ? WIFI_BAND_5_GHZ_DFS_ONLY : 0))
                == WIFI_BAND_ALL;
    }

    /**
     * Returns a list of all the possible channels for the given band(s).
     *
     * @param band one of the WifiScanner#WIFI_BAND_* constants, e.g. {@link #WIFI_BAND_24_GHZ}
     * @return a list of all the frequencies, in MHz, for the given band(s) e.g. channel 1 is
     * 2412, or null if an error occurred.
     */
    @NonNull
    @RequiresPermission(NEARBY_WIFI_DEVICES)
    public List<Integer> getAvailableChannels(int band) {
        try {
            Bundle extras = new Bundle();
            if (SdkLevel.isAtLeastS()) {
                extras.putParcelable(WifiManager.EXTRA_PARAM_KEY_ATTRIBUTION_SOURCE,
                        mContext.getAttributionSource());
            }
            Bundle bundle = mService.getAvailableChannels(band, mContext.getOpPackageName(),
                    mContext.getAttributionTag(), extras);
            List<Integer> channels = bundle.getIntegerArrayList(GET_AVAILABLE_CHANNELS_EXTRA);
            return channels == null ? new ArrayList<>() : channels;
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    private class ServiceListener extends IWifiScannerListener.Stub {
        private ActionListener mActionListener;
        private Executor mExecutor;

        ServiceListener(ActionListener listener, Executor executor) {
            mActionListener = listener;
            mExecutor = executor;
        }

        @Override
        public void onSuccess() {
            if (mActionListener == null) return;
            Binder.clearCallingIdentity();
            mExecutor.execute(mActionListener::onSuccess);
        }

        @Override
        public void onFailure(int reason, String description) {
            if (mActionListener == null) return;
            Binder.clearCallingIdentity();
            mExecutor.execute(() ->
                    mActionListener.onFailure(reason, description));
            removeListener(mActionListener);
        }

        /**
         * reports results retrieved from background scan and single shot scans
         */
        @Override
        public void onResults(WifiScanner.ScanData[] results) {
            if (mActionListener == null) return;
            if (!(mActionListener instanceof ScanListener)) return;
            ScanListener scanListener = (ScanListener) mActionListener;
            Binder.clearCallingIdentity();
            mExecutor.execute(
                    () -> scanListener.onResults(results));
        }

        /**
         * reports full scan result for each access point found in scan
         */
        @Override
        public void onFullResult(ScanResult fullScanResult) {
            if (mActionListener == null) return;
            if (!(mActionListener instanceof ScanListener)) return;
            ScanListener scanListener = (ScanListener) mActionListener;
            Binder.clearCallingIdentity();
            mExecutor.execute(
                    () -> scanListener.onFullResult(fullScanResult));
        }

        @Override
        public void onSingleScanCompleted() {
            if (DBG) Log.d(TAG, "single scan completed");
            removeListener(mActionListener);
        }

        /**
         * Invoked when one of the PNO networks are found in scan results.
         */
        @Override
        public void onPnoNetworkFound(ScanResult[] results) {
            if (mActionListener == null) return;
            if (!(mActionListener instanceof PnoScanListener)) return;
            PnoScanListener pnoScanListener = (PnoScanListener) mActionListener;
            Binder.clearCallingIdentity();
            mExecutor.execute(
                    () -> pnoScanListener.onPnoNetworkFound(results));
        }
    }

    /**
     * provides channel specification for scanning
     */
    public static class ChannelSpec {
        /**
         * channel frequency in MHz; for example channel 1 is specified as 2412
         */
        public int frequency;
        /**
         * if true, scan this channel in passive fashion.
         * This flag is ignored on DFS channel specification.
         * @hide
         */
        public boolean passive;                                    /* ignored on DFS channels */
        /**
         * how long to dwell on this channel
         * @hide
         */
        public int dwellTimeMS;                                    /* not supported for now */

        /**
         * default constructor for channel spec
         */
        public ChannelSpec(int frequency) {
            this.frequency = frequency;
            passive = false;
            dwellTimeMS = 0;
        }
    }

    /**
     * reports {@link ScanListener#onResults} when underlying buffers are full
     * this is simply the lack of the {@link #REPORT_EVENT_AFTER_EACH_SCAN} flag
     * @deprecated It is not supported anymore.
     */
    @Deprecated
    public static final int REPORT_EVENT_AFTER_BUFFER_FULL = 0;
    /**
     * reports {@link ScanListener#onResults} after each scan
     */
    public static final int REPORT_EVENT_AFTER_EACH_SCAN = (1 << 0);
    /**
     * reports {@link ScanListener#onFullResult} whenever each beacon is discovered
     */
    public static final int REPORT_EVENT_FULL_SCAN_RESULT = (1 << 1);
    /**
     * Do not place scans in the chip's scan history buffer
     */
    public static final int REPORT_EVENT_NO_BATCH = (1 << 2);

    /**
     * Optimize the scan for lower latency.
     * @see ScanSettings#type
     */
    public static final int SCAN_TYPE_LOW_LATENCY = 0;
    /**
     * Optimize the scan for lower power usage.
     * @see ScanSettings#type
     */
    public static final int SCAN_TYPE_LOW_POWER = 1;
    /**
     * Optimize the scan for higher accuracy.
     * @see ScanSettings#type
     */
    public static final int SCAN_TYPE_HIGH_ACCURACY = 2;
    /**
     * Max valid value of SCAN_TYPE_
     * @hide
     */
    public static final int SCAN_TYPE_MAX = 2;

    /** {@hide} */
    public static final String SCAN_PARAMS_SCAN_SETTINGS_KEY = "ScanSettings";
    /** {@hide} */
    public static final String SCAN_PARAMS_WORK_SOURCE_KEY = "WorkSource";
    /** {@hide} */
    public static final String REQUEST_PACKAGE_NAME_KEY = "PackageName";
    /** {@hide} */
    public static final String REQUEST_FEATURE_ID_KEY = "FeatureId";

    /**
     * scan configuration parameters to be sent to {@link #startBackgroundScan}
     */
    public static class ScanSettings implements Parcelable {
        /** Hidden network to be scanned for. */
        public static class HiddenNetwork {
            /** SSID of the network */
            @NonNull
            public final String ssid;

            /** Default constructor for HiddenNetwork. */
            public HiddenNetwork(@NonNull String ssid) {
                this.ssid = ssid;
            }
        }

        /** one of the WIFI_BAND values */
        public int band;
        /**
         * one of the {@code WIFI_RNR_*} values.
         */
        private int mRnrSetting = WIFI_RNR_ENABLED_IF_WIFI_BAND_6_GHZ_SCANNED;

        /**
         * See {@link #set6GhzPscOnlyEnabled}
         */
        private boolean mEnable6GhzPsc = false;

        /** list of channels; used when band is set to WIFI_BAND_UNSPECIFIED */
        public ChannelSpec[] channels;
        /**
         * List of hidden networks to scan for. Explicit probe requests are sent out for such
         * networks during scan. Only valid for single scan requests.
         */
        @NonNull
        @RequiresPermission(android.Manifest.permission.NETWORK_STACK)
        public final List<HiddenNetwork> hiddenNetworks = new ArrayList<>();

        /**
         * vendor IEs -- list of ScanResult.InformationElement, configured by App
         * see {@link #setVendorIes(List)}
         */
        @NonNull
        private List<ScanResult.InformationElement> mVendorIes = new ArrayList<>();

        /**
         * period of background scan; in millisecond, 0 => single shot scan
         * @deprecated Background scan support has always been hardware vendor dependent. This
         * support may not be present on newer devices. Use {@link #startScan(ScanSettings,
         * ScanListener)} instead for single scans.
         */
        @Deprecated
        public int periodInMs;
        /**
         * must have a valid REPORT_EVENT value
         * @deprecated Background scan support has always been hardware vendor dependent. This
         * support may not be present on newer devices. Use {@link #startScan(ScanSettings,
         * ScanListener)} instead for single scans.
         */
        @Deprecated
        public int reportEvents;
        /**
         * defines number of bssids to cache from each scan
         * @deprecated Background scan support has always been hardware vendor dependent. This
         * support may not be present on newer devices. Use {@link #startScan(ScanSettings,
         * ScanListener)} instead for single scans.
         */
        @Deprecated
        public int numBssidsPerScan;
        /**
         * defines number of scans to cache; use it with REPORT_EVENT_AFTER_BUFFER_FULL
         * to wake up at fixed interval
         * @deprecated Background scan support has always been hardware vendor dependent. This
         * support may not be present on newer devices. Use {@link #startScan(ScanSettings,
         * ScanListener)} instead for single scans.
         */
        @Deprecated
        public int maxScansToCache;
        /**
         * if maxPeriodInMs is non zero or different than period, then this bucket is
         * a truncated binary exponential backoff bucket and the scan period will grow
         * exponentially as per formula: actual_period(N) = period * (2 ^ (N/stepCount))
         * to maxPeriodInMs
         * @deprecated Background scan support has always been hardware vendor dependent. This
         * support may not be present on newer devices. Use {@link #startScan(ScanSettings,
         * ScanListener)} instead for single scans.
         */
        @Deprecated
        public int maxPeriodInMs;
        /**
         * for truncated binary exponential back off bucket, number of scans to perform
         * for a given period
         * @deprecated Background scan support has always been hardware vendor dependent. This
         * support may not be present on newer devices. Use {@link #startScan(ScanSettings,
         * ScanListener)} instead for single scans.
         */
        @Deprecated
        public int stepCount;
        /**
         * Flag to indicate if the scan settings are targeted for PNO scan.
         * {@hide}
         */
        public boolean isPnoScan;
        /**
         * Indicate the type of scan to be performed by the wifi chip.
         *
         * On devices with multiple hardware radio chains (and hence different modes of scan),
         * this type serves as an indication to the hardware on what mode of scan to perform.
         * Only apps holding {@link android.Manifest.permission.NETWORK_STACK} permission can set
         * this value.
         *
         * Note: This serves as an intent and not as a stipulation, the wifi chip
         * might honor or ignore the indication based on the current radio conditions. Always
         * use the {@link ScanResult#radioChainInfos} to figure out the radio chain configuration
         * used to receive the corresponding scan result.
         *
         * One of {@link #SCAN_TYPE_LOW_LATENCY}, {@link #SCAN_TYPE_LOW_POWER},
         * {@link #SCAN_TYPE_HIGH_ACCURACY}.
         * Default value: {@link #SCAN_TYPE_LOW_LATENCY}.
         */
        @WifiAnnotations.ScanType
        @RequiresPermission(android.Manifest.permission.NETWORK_STACK)
        public int type = SCAN_TYPE_LOW_LATENCY;
        /**
         * This scan request may ignore location settings while receiving scans. This should only
         * be used in emergency situations.
         * {@hide}
         */
        @SystemApi
        public boolean ignoreLocationSettings;
        /**
         * This scan request will be hidden from app-ops noting for location information. This
         * should only be used by FLP/NLP module on the device which is using the scan results to
         * compute results for behalf on their clients. FLP/NLP module using this flag should ensure
         * that they note in app-ops the eventual delivery of location information computed using
         * these results to their client .
         * {@hide}
         */
        @SystemApi
        public boolean hideFromAppOps;

        /**
         * Configure whether it is needed to scan 6Ghz non Preferred Scanning Channels when scanning
         * {@link #WIFI_BAND_6_GHZ}. If set to true and a band that contains
         * {@link #WIFI_BAND_6_GHZ} is configured for scanning, then only scan 6Ghz PSC channels in
         * addition to any other bands configured for scanning. Note, 6Ghz non-PSC channels that
         * are co-located with 2.4/5Ghz APs could still be scanned via the
         * {@link #setRnrSetting(int)} API.
         *
         * <p>
         * For example, given a ScanSettings with band set to {@link #WIFI_BAND_24_5_WITH_DFS_6_GHZ}
         * If this API is set to "true" then the ScanSettings is configured to scan all of 2.4Ghz
         * + all of 5Ghz(DFS and non-DFS) + 6Ghz PSC channels. If this API is set to "false", then
         * the ScanSetting is configured to scan all of 2.4Ghz + all of 5Ghz(DFS and non_DFS)
         * + all of 6Ghz channels.
         * @param enable true to only scan 6Ghz PSC channels, false to scan all 6Ghz channels.
         */
        @RequiresApi(Build.VERSION_CODES.S)
        public void set6GhzPscOnlyEnabled(boolean enable) {
            if (!SdkLevel.isAtLeastS()) {
                throw new UnsupportedOperationException();
            }
            mEnable6GhzPsc = enable;
        }

        /**
         * See {@link #set6GhzPscOnlyEnabled}
         */
        @RequiresApi(Build.VERSION_CODES.S)
        public boolean is6GhzPscOnlyEnabled() {
            if (!SdkLevel.isAtLeastS()) {
                throw new UnsupportedOperationException();
            }
            return mEnable6GhzPsc;
        }

        /**
         * Configure when to scan 6Ghz APs co-located with 2.4/5Ghz APs using Reduced
         * Neighbor Report (RNR).
         * @param rnrSetting one of the {@code WIFI_RNR_*} values
         */
        @RequiresApi(Build.VERSION_CODES.S)
        public void setRnrSetting(@RnrSetting int rnrSetting) {
            if (!SdkLevel.isAtLeastS()) {
                throw new UnsupportedOperationException();
            }
            if (rnrSetting < WIFI_RNR_ENABLED_IF_WIFI_BAND_6_GHZ_SCANNED
                    || rnrSetting > WIFI_RNR_NOT_NEEDED) {
                throw new IllegalArgumentException("Invalid rnrSetting");
            }
            mRnrSetting = rnrSetting;
        }

        /**
         * See {@link #setRnrSetting}
         */
        @RequiresApi(Build.VERSION_CODES.S)
        public @RnrSetting int getRnrSetting() {
            if (!SdkLevel.isAtLeastS()) {
                throw new UnsupportedOperationException();
            }
            return mRnrSetting;
        }

        /**
         * Set vendor IEs in scan probe req.
         *
         * @param vendorIes List of ScanResult.InformationElement configured by App.
         */
        @RequiresApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
        public void setVendorIes(@NonNull List<ScanResult.InformationElement> vendorIes) {
            if (!SdkLevel.isAtLeastU()) {
                throw new UnsupportedOperationException();
            }

            mVendorIes.clear();
            int totalBytes = 0;
            for (ScanResult.InformationElement e : vendorIes) {
                if (e.id != ScanResult.InformationElement.EID_VSA) {
                    throw new IllegalArgumentException("received InformationElement which is not "
                            + "a Vendor Specific IE (VSIE). VSIEs have an ID = ScanResult"
                            + ".InformationElement.EID_VSA.");
                }
                if (e.bytes == null || e.bytes.length > 0xff) {
                    throw new IllegalArgumentException("received InformationElement whose payload "
                            + "is null or size is greater than 255.");
                }
                // The total bytes of an IE is EID (1 byte) + length (1 byte) + payload length.
                totalBytes += WIFI_IE_HEAD_LEN + e.bytes.length;
                if (totalBytes > WIFI_SCANNER_SETTINGS_VENDOR_ELEMENTS_MAX_LEN) {
                    throw new IllegalArgumentException(
                            "received InformationElement whose total size is greater than "
                                    + WIFI_SCANNER_SETTINGS_VENDOR_ELEMENTS_MAX_LEN + ".");
                }
            }
            mVendorIes.addAll(vendorIes);
        }

        /**
         * See {@link #setVendorIes(List)}
         */
        @RequiresApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
        public @NonNull List<ScanResult.InformationElement> getVendorIes() {
            if (!SdkLevel.isAtLeastU()) {
                throw new UnsupportedOperationException();
            }
            return mVendorIes;
        }

        /** Implement the Parcelable interface {@hide} */
        public int describeContents() {
            return 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeInt(band);
            dest.writeInt(periodInMs);
            dest.writeInt(reportEvents);
            dest.writeInt(numBssidsPerScan);
            dest.writeInt(maxScansToCache);
            dest.writeInt(maxPeriodInMs);
            dest.writeInt(stepCount);
            dest.writeInt(isPnoScan ? 1 : 0);
            dest.writeInt(type);
            dest.writeInt(ignoreLocationSettings ? 1 : 0);
            dest.writeInt(hideFromAppOps ? 1 : 0);
            dest.writeInt(mRnrSetting);
            dest.writeBoolean(mEnable6GhzPsc);
            if (channels != null) {
                dest.writeInt(channels.length);
                for (int i = 0; i < channels.length; i++) {
                    dest.writeInt(channels[i].frequency);
                    dest.writeInt(channels[i].dwellTimeMS);
                    dest.writeInt(channels[i].passive ? 1 : 0);
                }
            } else {
                dest.writeInt(0);
            }
            dest.writeInt(hiddenNetworks.size());
            for (HiddenNetwork hiddenNetwork : hiddenNetworks) {
                dest.writeString(hiddenNetwork.ssid);
            }
            dest.writeTypedList(mVendorIes);
        }

        /** Implement the Parcelable interface */
        public static final @NonNull Creator<ScanSettings> CREATOR =
                new Creator<ScanSettings>() {
                    public ScanSettings createFromParcel(Parcel in) {
                        ScanSettings settings = new ScanSettings();
                        settings.band = in.readInt();
                        settings.periodInMs = in.readInt();
                        settings.reportEvents = in.readInt();
                        settings.numBssidsPerScan = in.readInt();
                        settings.maxScansToCache = in.readInt();
                        settings.maxPeriodInMs = in.readInt();
                        settings.stepCount = in.readInt();
                        settings.isPnoScan = in.readInt() == 1;
                        settings.type = in.readInt();
                        settings.ignoreLocationSettings = in.readInt() == 1;
                        settings.hideFromAppOps = in.readInt() == 1;
                        settings.mRnrSetting = in.readInt();
                        settings.mEnable6GhzPsc = in.readBoolean();
                        int num_channels = in.readInt();
                        settings.channels = new ChannelSpec[num_channels];
                        for (int i = 0; i < num_channels; i++) {
                            int frequency = in.readInt();
                            ChannelSpec spec = new ChannelSpec(frequency);
                            spec.dwellTimeMS = in.readInt();
                            spec.passive = in.readInt() == 1;
                            settings.channels[i] = spec;
                        }
                        int numNetworks = in.readInt();
                        settings.hiddenNetworks.clear();
                        for (int i = 0; i < numNetworks; i++) {
                            String ssid = in.readString();
                            settings.hiddenNetworks.add(new HiddenNetwork(ssid));
                        }
                        in.readTypedList(settings.mVendorIes,
                                ScanResult.InformationElement.CREATOR);
                        return settings;
                    }

                    public ScanSettings[] newArray(int size) {
                        return new ScanSettings[size];
                    }
                };
    }

    /**
     * All the information garnered from a single scan
     */
    public static class ScanData implements Parcelable {
        /** scan identifier */
        private int mId;
        /** additional information about scan
         * 0 => no special issues encountered in the scan
         * non-zero => scan was truncated, so results may not be complete
         */
        private int mFlags;
        /**
         * Indicates the buckets that were scanned to generate these results.
         * This is not relevant to WifiScanner API users and is used internally.
         * {@hide}
         */
        private int mBucketsScanned;
        /**
         * Bands scanned. One of the WIFI_BAND values.
         * Will be {@link #WIFI_BAND_UNSPECIFIED} if the list of channels do not fully cover
         * any of the bands.
         * {@hide}
         */
        private int mScannedBands;
        /** all scan results discovered in this scan, sorted by timestamp in ascending order */
        private final List<ScanResult> mResults;

        ScanData() {
            mResults = new ArrayList<>();
        }

        public ScanData(int id, int flags, ScanResult[] results) {
            mId = id;
            mFlags = flags;
            mResults = new ArrayList<>(Arrays.asList(results));
        }

        /** {@hide} */
        public ScanData(int id, int flags, int bucketsScanned, int bandsScanned,
                        ScanResult[] results) {
            this(id, flags, bucketsScanned, bandsScanned, new ArrayList<>(Arrays.asList(results)));
        }

        /** {@hide} */
        public ScanData(int id, int flags, int bucketsScanned, int bandsScanned,
                        List<ScanResult> results) {
            mId = id;
            mFlags = flags;
            mBucketsScanned = bucketsScanned;
            mScannedBands = bandsScanned;
            mResults = results;
        }

        public ScanData(ScanData s) {
            mId = s.mId;
            mFlags = s.mFlags;
            mBucketsScanned = s.mBucketsScanned;
            mScannedBands = s.mScannedBands;
            mResults = new ArrayList<>();
            for (ScanResult scanResult : s.mResults) {
                mResults.add(new ScanResult(scanResult));
            }
        }

        public int getId() {
            return mId;
        }

        public int getFlags() {
            return mFlags;
        }

        /** {@hide} */
        public int getBucketsScanned() {
            return mBucketsScanned;
        }

        /**
         * Retrieve the bands that were fully scanned for this ScanData instance. "fully" here
         * refers to all the channels available in the band based on the current regulatory
         * domain.
         *
         * @return Bitmask of {@link #WIFI_BAND_24_GHZ}, {@link #WIFI_BAND_5_GHZ},
         * {@link #WIFI_BAND_5_GHZ_DFS_ONLY}, {@link #WIFI_BAND_6_GHZ} & {@link #WIFI_BAND_60_GHZ}
         * values. Each bit is set only if all the channels in the corresponding band is scanned.
         * Will be {@link #WIFI_BAND_UNSPECIFIED} if the list of channels do not fully cover
         * any of the bands.
         * <p>
         * For ex:
         * <li> Scenario 1:  Fully scanned 2.4Ghz band, partially scanned 5Ghz band
         *      - Returns {@link #WIFI_BAND_24_GHZ}
         * </li>
         * <li> Scenario 2:  Partially scanned 2.4Ghz band and 5Ghz band
         *      - Returns {@link #WIFI_BAND_UNSPECIFIED}
         * </li>
         * </p>
         */
        public @WifiBand int getScannedBands() {
            return getScannedBandsInternal();
        }

        /**
         * Same as {@link #getScannedBands()}. For use in the wifi stack without version check.
         *
         * {@hide}
         */
        public @WifiBand int getScannedBandsInternal() {
            return mScannedBands;
        }

        public ScanResult[] getResults() {
            return mResults.toArray(new ScanResult[0]);
        }

        /** {@hide} */
        public void addResults(@NonNull ScanResult[] newResults) {
            for (ScanResult result : newResults) {
                mResults.add(new ScanResult(result));
            }
        }

        /** {@hide} */
        public void addResults(@NonNull ScanData s) {
            mScannedBands |= s.mScannedBands;
            mFlags |= s.mFlags;
            addResults(s.getResults());
        }

        /** {@hide} */
        public boolean isFullBandScanResults() {
            return (mScannedBands & WifiScanner.WIFI_BAND_24_GHZ) != 0
                && (mScannedBands & WifiScanner.WIFI_BAND_5_GHZ) != 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public int describeContents() {
            return 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeInt(mId);
            dest.writeInt(mFlags);
            dest.writeInt(mBucketsScanned);
            dest.writeInt(mScannedBands);
            dest.writeParcelableList(mResults, 0);
        }

        /** Implement the Parcelable interface {@hide} */
        public static final @NonNull Creator<ScanData> CREATOR =
                new Creator<ScanData>() {
                    public ScanData createFromParcel(Parcel in) {
                        int id = in.readInt();
                        int flags = in.readInt();
                        int bucketsScanned = in.readInt();
                        int bandsScanned = in.readInt();
                        List<ScanResult> results = new ArrayList<>();
                        in.readParcelableList(results, ScanResult.class.getClassLoader());
                        return new ScanData(id, flags, bucketsScanned, bandsScanned, results);
                    }

                    public ScanData[] newArray(int size) {
                        return new ScanData[size];
                    }
                };
    }

    public static class ParcelableScanData implements Parcelable {

        public ScanData mResults[];

        public ParcelableScanData(ScanData[] results) {
            mResults = results;
        }

        public ScanData[] getResults() {
            return mResults;
        }

        /** Implement the Parcelable interface {@hide} */
        public int describeContents() {
            return 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public void writeToParcel(Parcel dest, int flags) {
            if (mResults != null) {
                dest.writeInt(mResults.length);
                for (int i = 0; i < mResults.length; i++) {
                    ScanData result = mResults[i];
                    result.writeToParcel(dest, flags);
                }
            } else {
                dest.writeInt(0);
            }
        }

        /** Implement the Parcelable interface {@hide} */
        public static final @NonNull Creator<ParcelableScanData> CREATOR =
                new Creator<ParcelableScanData>() {
                    public ParcelableScanData createFromParcel(Parcel in) {
                        int n = in.readInt();
                        ScanData results[] = new ScanData[n];
                        for (int i = 0; i < n; i++) {
                            results[i] = ScanData.CREATOR.createFromParcel(in);
                        }
                        return new ParcelableScanData(results);
                    }

                    public ParcelableScanData[] newArray(int size) {
                        return new ParcelableScanData[size];
                    }
                };
    }

    public static class ParcelableScanResults implements Parcelable {

        public ScanResult mResults[];

        public ParcelableScanResults(ScanResult[] results) {
            mResults = results;
        }

        public ScanResult[] getResults() {
            return mResults;
        }

        /** Implement the Parcelable interface {@hide} */
        public int describeContents() {
            return 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public void writeToParcel(Parcel dest, int flags) {
            if (mResults != null) {
                dest.writeInt(mResults.length);
                for (int i = 0; i < mResults.length; i++) {
                    ScanResult result = mResults[i];
                    result.writeToParcel(dest, flags);
                }
            } else {
                dest.writeInt(0);
            }
        }

        /** Implement the Parcelable interface {@hide} */
        public static final @NonNull Creator<ParcelableScanResults> CREATOR =
                new Creator<ParcelableScanResults>() {
                    public ParcelableScanResults createFromParcel(Parcel in) {
                        int n = in.readInt();
                        ScanResult results[] = new ScanResult[n];
                        for (int i = 0; i < n; i++) {
                            results[i] = ScanResult.CREATOR.createFromParcel(in);
                        }
                        return new ParcelableScanResults(results);
                    }

                    public ParcelableScanResults[] newArray(int size) {
                        return new ParcelableScanResults[size];
                    }
                };
    }

    /** {@hide} */
    public static final String PNO_PARAMS_PNO_SETTINGS_KEY = "PnoSettings";
    /** {@hide} */
    public static final String PNO_PARAMS_SCAN_SETTINGS_KEY = "ScanSettings";
    /**
     * PNO scan configuration parameters to be sent to {@link #startPnoScan}.
     * Note: This structure needs to be in sync with |wifi_epno_params| struct in gscan HAL API.
     * {@hide}
     */
    public static class PnoSettings implements Parcelable {
        /**
         * Pno network to be added to the PNO scan filtering.
         * {@hide}
         */
        public static class PnoNetwork {
            /*
             * Pno flags bitmask to be set in {@link #PnoNetwork.flags}
             */
            /** Whether directed scan needs to be performed (for hidden SSIDs) */
            public static final byte FLAG_DIRECTED_SCAN = (1 << 0);
            /** Whether PNO event shall be triggered if the network is found on A band */
            public static final byte FLAG_A_BAND = (1 << 1);
            /** Whether PNO event shall be triggered if the network is found on G band */
            public static final byte FLAG_G_BAND = (1 << 2);
            /**
             * Whether strict matching is required
             * If required then the firmware must store the network's SSID and not just a hash
             */
            public static final byte FLAG_STRICT_MATCH = (1 << 3);
            /**
             * If this SSID should be considered the same network as the currently connected
             * one for scoring.
             */
            public static final byte FLAG_SAME_NETWORK = (1 << 4);

            /*
             * Code for matching the beacon AUTH IE - additional codes. Bitmask to be set in
             * {@link #PnoNetwork.authBitField}
             */
            /** Open Network */
            public static final byte AUTH_CODE_OPEN = (1 << 0);
            /** WPA_PSK or WPA2PSK */
            public static final byte AUTH_CODE_PSK = (1 << 1);
            /** any EAPOL */
            public static final byte AUTH_CODE_EAPOL = (1 << 2);

            /** SSID of the network */
            public String ssid;
            /** Bitmask of the FLAG_XXX */
            public byte flags = 0;
            /** Bitmask of the ATUH_XXX */
            public byte authBitField = 0;
            /** frequencies on which the particular network needs to be scanned for */
            public int[] frequencies = {};

            /**
             * default constructor for PnoNetwork
             */
            public PnoNetwork(String ssid) {
                this.ssid = ssid;
            }

            @Override
            public int hashCode() {
                return Objects.hash(ssid, flags, authBitField);
            }

            @Override
            public boolean equals(Object obj) {
                if (this == obj) {
                    return true;
                }
                if (!(obj instanceof PnoNetwork)) {
                    return false;
                }
                PnoNetwork lhs = (PnoNetwork) obj;
                return TextUtils.equals(this.ssid, lhs.ssid)
                        && this.flags == lhs.flags
                        && this.authBitField == lhs.authBitField;
            }
        }

        /** Connected vs Disconnected PNO flag {@hide} */
        public boolean isConnected;
        /** Minimum 5GHz RSSI for a BSSID to be considered */
        public int min5GHzRssi;
        /** Minimum 2.4GHz RSSI for a BSSID to be considered */
        public int min24GHzRssi;
        /** Minimum 6GHz RSSI for a BSSID to be considered */
        public int min6GHzRssi;
        /** Iterations of Pno scan */
        public int scanIterations;
        /** Multiplier of Pno scan interval */
        public int scanIntervalMultiplier;
        /** Pno Network filter list */
        public PnoNetwork[] networkList;

        /** Implement the Parcelable interface {@hide} */
        public int describeContents() {
            return 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeInt(isConnected ? 1 : 0);
            dest.writeInt(min5GHzRssi);
            dest.writeInt(min24GHzRssi);
            dest.writeInt(min6GHzRssi);
            dest.writeInt(scanIterations);
            dest.writeInt(scanIntervalMultiplier);
            if (networkList != null) {
                dest.writeInt(networkList.length);
                for (int i = 0; i < networkList.length; i++) {
                    dest.writeString(networkList[i].ssid);
                    dest.writeByte(networkList[i].flags);
                    dest.writeByte(networkList[i].authBitField);
                    dest.writeIntArray(networkList[i].frequencies);
                }
            } else {
                dest.writeInt(0);
            }
        }

        /** Implement the Parcelable interface {@hide} */
        public static final @NonNull Creator<PnoSettings> CREATOR =
                new Creator<PnoSettings>() {
                    public PnoSettings createFromParcel(Parcel in) {
                        PnoSettings settings = new PnoSettings();
                        settings.isConnected = in.readInt() == 1;
                        settings.min5GHzRssi = in.readInt();
                        settings.min24GHzRssi = in.readInt();
                        settings.min6GHzRssi = in.readInt();
                        settings.scanIterations = in.readInt();
                        settings.scanIntervalMultiplier = in.readInt();
                        int numNetworks = in.readInt();
                        settings.networkList = new PnoNetwork[numNetworks];
                        for (int i = 0; i < numNetworks; i++) {
                            String ssid = in.readString();
                            PnoNetwork network = new PnoNetwork(ssid);
                            network.flags = in.readByte();
                            network.authBitField = in.readByte();
                            network.frequencies = in.createIntArray();
                            settings.networkList[i] = network;
                        }
                        return settings;
                    }

                    public PnoSettings[] newArray(int size) {
                        return new PnoSettings[size];
                    }
                };

    }

    /**
     * interface to get scan events on; specify this on {@link #startBackgroundScan} or
     * {@link #startScan}
     */
    public interface ScanListener extends ActionListener {
        /**
         * Framework co-ordinates scans across multiple apps; so it may not give exactly the
         * same period requested. If period of a scan is changed; it is reported by this event.
         * @deprecated Background scan support has always been hardware vendor dependent. This
         * support may not be present on newer devices. Use {@link #startScan(ScanSettings,
         * ScanListener)} instead for single scans.
         */
        @Deprecated
        public void onPeriodChanged(int periodInMs);
        /**
         * reports results retrieved from background scan and single shot scans
         */
        public void onResults(ScanData[] results);
        /**
         * reports full scan result for each access point found in scan
         */
        public void onFullResult(ScanResult fullScanResult);
    }

    /**
     * interface to get PNO scan events on; specify this on {@link #startDisconnectedPnoScan} and
     * {@link #startConnectedPnoScan}.
     * {@hide}
     */
    public interface PnoScanListener extends ScanListener {
        /**
         * Invoked when one of the PNO networks are found in scan results.
         */
        void onPnoNetworkFound(ScanResult[] results);
    }

    /**
     * Enable/Disable wifi scanning.
     *
     * @param enable set to true to enable scanning, set to false to disable all types of scanning.
     *
     * @see WifiManager#ACTION_WIFI_SCAN_AVAILABILITY_CHANGED
     * {@hide}
     */
    @SystemApi
    @RequiresPermission(Manifest.permission.NETWORK_STACK)
    public void setScanningEnabled(boolean enable) {
        try {
            mService.setScanningEnabled(enable, Process.myTid(), mContext.getOpPackageName());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Register a listener that will receive results from all single scans.
     * Either the {@link ScanListener#onSuccess()} or  {@link ScanListener#onFailure(int, String)}
     * method will be called once when the listener is registered.
     * Afterwards (assuming onSuccess was called), all subsequent single scan results will be
     * delivered to the listener. It is possible that onFullResult will not be called for all
     * results of the first scan if the listener was registered during the scan.
     * <p>
     * On {@link android.os.Build.VERSION_CODES#TIRAMISU} or above this API can be called by
     * an app with either {@link android.Manifest.permission#LOCATION_HARDWARE} or
     * {@link android.Manifest.permission#NETWORK_STACK}. On platform versions prior to
     * {@link android.os.Build.VERSION_CODES#TIRAMISU}, the caller must have
     * {@link android.Manifest.permission#NETWORK_STACK}.
     *
     * @param executor the Executor on which to run the callback.
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this request, and must also be specified to cancel the request.
     *                 Multiple requests should also not share this object.
     * @throws SecurityException if the caller does not have permission.
     */
    @RequiresPermission(anyOf = {
            Manifest.permission.LOCATION_HARDWARE,
            Manifest.permission.NETWORK_STACK})
    public void registerScanListener(@NonNull @CallbackExecutor Executor executor,
            @NonNull ScanListener listener) {
        Objects.requireNonNull(executor, "executor cannot be null");
        Objects.requireNonNull(listener, "listener cannot be null");
        ServiceListener serviceListener = new ServiceListener(listener, executor);
        if (!addListener(listener, serviceListener)) {
            Binder.clearCallingIdentity();
            executor.execute(() ->
                    // TODO: fix the typo in WifiScanner system API.
                    listener.onFailure(REASON_DUPLICATE_REQEUST, // NOTYPO
                            "Outstanding request with same key not stopped yet"));
            return;
        }
        try {
            mService.registerScanListener(serviceListener,
                    mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to register listener " + listener);
            removeListener(listener);
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Overload of {@link #registerScanListener(Executor, ScanListener)} that executes the callback
     * synchronously.
     * @hide
     */
    @RequiresPermission(Manifest.permission.NETWORK_STACK)
    public void registerScanListener(@NonNull ScanListener listener) {
        registerScanListener(new SynchronousExecutor(), listener);
    }

    /**
     * Deregister a listener for ongoing single scans
     * @param listener specifies which scan to cancel; must be same object as passed in {@link
     *  #registerScanListener}
     */
    public void unregisterScanListener(@NonNull ScanListener listener) {
        Objects.requireNonNull(listener, "listener cannot be null");
        ServiceListener serviceListener = getServiceListener(listener);
        if (serviceListener == null) {
            Log.e(TAG, "listener does not exist");
            return;
        }
        try {
            mService.unregisterScanListener(serviceListener, mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            Log.e(TAG, "failed to unregister listener");
            throw e.rethrowFromSystemServer();
        } finally {
            removeListener(listener);
        }
    }

    /**
     * Check whether the Wi-Fi subsystem has started a scan and is waiting for scan results.
     * @return true if a scan initiated via
     *         {@link WifiScanner#startScan(ScanSettings, ScanListener)} or
     *         {@link WifiManager#startScan()} is in progress.
     *         false if there is currently no scanning initiated by {@link WifiScanner} or
     *         {@link WifiManager}, but it's still possible the wifi radio is scanning for
     *         another reason.
     * @hide
     */
    @SystemApi
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public boolean isScanning() {
        try {
            return mService.isScanning();
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /** start wifi scan in background
     * @param settings specifies various parameters for the scan; for more information look at
     * {@link ScanSettings}
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this scan, and must also be specified to cancel the scan. Multiple
     *                 scans should also not share this object.
     */
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public void startBackgroundScan(ScanSettings settings, ScanListener listener) {
        startBackgroundScan(settings, listener, null);
    }

    /** start wifi scan in background
     * @param settings specifies various parameters for the scan; for more information look at
     * {@link ScanSettings}
     * @param workSource WorkSource to blame for power usage
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this scan, and must also be specified to cancel the scan. Multiple
     *                 scans should also not share this object.
     * @deprecated Background scan support has always been hardware vendor dependent. This support
     * may not be present on newer devices. Use {@link #startScan(ScanSettings, ScanListener)}
     * instead for single scans.
     */
    @Deprecated
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public void startBackgroundScan(ScanSettings settings, ScanListener listener,
            WorkSource workSource) {
        Objects.requireNonNull(listener, "listener cannot be null");
        if (getServiceListener(listener) != null) return;
        ServiceListener serviceListener = new ServiceListener(listener, new SynchronousExecutor());
        if (!addListener(listener, serviceListener)) {
            Log.e(TAG, "listener already exist!");
            return;
        }
        try {
            mService.startBackgroundScan(serviceListener, settings, workSource,
                    mContext.getOpPackageName(), mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * stop an ongoing wifi scan
     * @param listener specifies which scan to cancel; must be same object as passed in {@link
     *  #startBackgroundScan}
     * @deprecated Background scan support has always been hardware vendor dependent. This support
     * may not be present on newer devices. Use {@link #startScan(ScanSettings, ScanListener)}
     * instead for single scans.
     */
    @Deprecated
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public void stopBackgroundScan(ScanListener listener) {
        Objects.requireNonNull(listener, "listener cannot be null");
        ServiceListener serviceListener = getServiceListener(listener);
        if (serviceListener == null) {
            Log.e(TAG, "listener does not exist");
            return;
        }
        try {
            mService.stopBackgroundScan(serviceListener, mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        } finally {
            removeListener(listener);
        }
    }

    /**
     * reports currently available scan results on appropriate listeners
     * @return true if all scan results were reported correctly
     * @deprecated Background scan support has always been hardware vendor dependent. This support
     * may not be present on newer devices. Use {@link #startScan(ScanSettings, ScanListener)}
     * instead for single scans.
     */
    @Deprecated
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public boolean getScanResults() {
        try {
            return mService.getScanResults(mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * starts a single scan and reports results asynchronously
     * @param settings specifies various parameters for the scan; for more information look at
     * {@link ScanSettings}
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this scan, and must also be specified to cancel the scan. Multiple
     *                 scans should also not share this object.
     */
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public void startScan(ScanSettings settings, ScanListener listener) {
        startScan(settings, listener, null);
    }

    /**
     * starts a single scan and reports results asynchronously
     * @param settings specifies various parameters for the scan; for more information look at
     * {@link ScanSettings}
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this scan, and must also be specified to cancel the scan. Multiple
     *                 scans should also not share this object.
     * @param workSource WorkSource to blame for power usage
     */
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public void startScan(ScanSettings settings, ScanListener listener, WorkSource workSource) {
        startScan(settings, new SynchronousExecutor(), listener, workSource);
    }

    /**
     * starts a single scan and reports results asynchronously
     * @param settings specifies various parameters for the scan; for more information look at
     * {@link ScanSettings}
     * @param executor the Executor on which to run the callback.
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this scan, and must also be specified to cancel the scan. Multiple
     *                 scans should also not share this object.
     * @param workSource WorkSource to blame for power usage
     * @hide
     */
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public void startScan(ScanSettings settings, @Nullable @CallbackExecutor Executor executor,
            ScanListener listener, WorkSource workSource) {
        Objects.requireNonNull(listener, "listener cannot be null");
        if (getServiceListener(listener) != null) return;
        ServiceListener serviceListener = new ServiceListener(listener, executor);
        if (!addListener(listener, serviceListener)) {
            Log.e(TAG, "listener already exist!");
            return;
        }
        try {
            mService.startScan(serviceListener, settings, workSource,
                    mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * stops an ongoing single shot scan; only useful after {@link #startScan} if onResults()
     * hasn't been called on the listener, ignored otherwise
     * @param listener
     */
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public void stopScan(ScanListener listener) {
        Objects.requireNonNull(listener, "listener cannot be null");
        ServiceListener serviceListener = getServiceListener(listener);
        if (serviceListener == null) {
            Log.e(TAG, "listener does not exist");
            return;
        }
        try {
            mService.stopScan(serviceListener, mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        } finally {
            removeListener(listener);
        }
    }

    /**
     * Retrieve the most recent scan results from a single scan request.
     */
    @NonNull
    @RequiresPermission(android.Manifest.permission.LOCATION_HARDWARE)
    public List<ScanResult> getSingleScanResults() {
        try {
            return mService.getSingleScanResults(mContext.getPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    private void startPnoScan(PnoScanListener listener, Executor executor,
            ScanSettings scanSettings, PnoSettings pnoSettings) {
        // Set the PNO scan flag.
        scanSettings.isPnoScan = true;
        if (getServiceListener(listener) != null) return;
        ServiceListener serviceListener = new ServiceListener(listener, executor);
        if (!addListener(listener, serviceListener)) {
            Log.w(TAG, "listener already exist!");
        }
        try {
            mService.startPnoScan(serviceListener, scanSettings, pnoSettings,
                    mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Start wifi connected PNO scan
     * @param scanSettings specifies various parameters for the scan; for more information look at
     * {@link ScanSettings}
     * @param pnoSettings specifies various parameters for PNO; for more information look at
     * {@link PnoSettings}
     * @param executor the Executor on which to run the callback.
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this scan, and must also be specified to cancel the scan. Multiple
     *                 scans should also not share this object.
     * {@hide}
     */
    public void startConnectedPnoScan(ScanSettings scanSettings, PnoSettings pnoSettings,
            @NonNull @CallbackExecutor Executor executor, PnoScanListener listener) {
        Objects.requireNonNull(listener, "listener cannot be null");
        Objects.requireNonNull(pnoSettings, "pnoSettings cannot be null");
        pnoSettings.isConnected = true;
        startPnoScan(listener, executor, scanSettings, pnoSettings);
    }
    /**
     * Start wifi disconnected PNO scan
     * @param scanSettings specifies various parameters for the scan; for more information look at
     * {@link ScanSettings}
     * @param pnoSettings specifies various parameters for PNO; for more information look at
     * {@link PnoSettings}
     * @param listener specifies the object to report events to. This object is also treated as a
     *                 key for this scan, and must also be specified to cancel the scan. Multiple
     *                 scans should also not share this object.
     * {@hide}
     */
    @RequiresPermission(android.Manifest.permission.NETWORK_STACK)
    public void startDisconnectedPnoScan(ScanSettings scanSettings, PnoSettings pnoSettings,
            @NonNull @CallbackExecutor Executor executor, PnoScanListener listener) {
        Objects.requireNonNull(listener, "listener cannot be null");
        Objects.requireNonNull(pnoSettings, "pnoSettings cannot be null");
        pnoSettings.isConnected = false;
        startPnoScan(listener, executor, scanSettings, pnoSettings);
    }
    /**
     * Stop an ongoing wifi PNO scan
     * @param listener specifies which scan to cancel; must be same object as passed in {@link
     *  #startPnoScan}
     * {@hide}
     */
    @RequiresPermission(android.Manifest.permission.NETWORK_STACK)
    public void stopPnoScan(ScanListener listener) {
        Objects.requireNonNull(listener, "listener cannot be null");
        ServiceListener serviceListener = getServiceListener(listener);
        if (serviceListener == null) {
            Log.e(TAG, "listener does not exist");
            return;
        }
        try {
            mService.stopPnoScan(serviceListener, mContext.getOpPackageName(),
                    mContext.getAttributionTag());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        } finally {
            removeListener(listener);
        }
    }

    /**
     * Enable verbose logging. For internal use by wifi framework only.
     * @param enabled whether verbose logging is enabled
     * @hide
     */
    @RequiresPermission(android.Manifest.permission.NETWORK_SETTINGS)
    public void enableVerboseLogging(boolean enabled) {
        try {
            mService.enableVerboseLogging(enabled);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /** specifies information about an access point of interest */
    @Deprecated
    public static class BssidInfo {
        /** bssid of the access point; in XX:XX:XX:XX:XX:XX format */
        public String bssid;
        /** low signal strength threshold; more information at {@link ScanResult#level} */
        public int low;                                            /* minimum RSSI */
        /** high signal threshold; more information at {@link ScanResult#level} */
        public int high;                                           /* maximum RSSI */
        /** channel frequency (in KHz) where you may find this BSSID */
        public int frequencyHint;
    }

    /** @hide */
    @SystemApi
    @Deprecated
    public static class WifiChangeSettings implements Parcelable {
        public int rssiSampleSize;                          /* sample size for RSSI averaging */
        public int lostApSampleSize;                        /* samples to confirm AP's loss */
        public int unchangedSampleSize;                     /* samples to confirm no change */
        public int minApsBreachingThreshold;                /* change threshold to trigger event */
        public int periodInMs;                              /* scan period in millisecond */
        public BssidInfo[] bssidInfos;

        /** Implement the Parcelable interface {@hide} */
        public int describeContents() {
            return 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public void writeToParcel(Parcel dest, int flags) {
        }

        /** Implement the Parcelable interface {@hide} */
        public static final @NonNull Creator<WifiChangeSettings> CREATOR =
                new Creator<WifiChangeSettings>() {
                    public WifiChangeSettings createFromParcel(Parcel in) {
                        return new WifiChangeSettings();
                    }

                    public WifiChangeSettings[] newArray(int size) {
                        return new WifiChangeSettings[size];
                    }
                };

    }

    /** configure WifiChange detection
     * @param rssiSampleSize number of samples used for RSSI averaging
     * @param lostApSampleSize number of samples to confirm an access point's loss
     * @param unchangedSampleSize number of samples to confirm there are no changes
     * @param minApsBreachingThreshold minimum number of access points that need to be
     *                                 out of range to detect WifiChange
     * @param periodInMs indicates period of scan to find changes
     * @param bssidInfos access points to watch
     */
    @Deprecated
    @SuppressLint("RequiresPermission")
    public void configureWifiChange(
            int rssiSampleSize,                             /* sample size for RSSI averaging */
            int lostApSampleSize,                           /* samples to confirm AP's loss */
            int unchangedSampleSize,                        /* samples to confirm no change */
            int minApsBreachingThreshold,                   /* change threshold to trigger event */
            int periodInMs,                                 /* period of scan */
            BssidInfo[] bssidInfos                          /* signal thresholds to cross */
            )
    {
        throw new UnsupportedOperationException();
    }

    /**
     * interface to get wifi change events on; use this on {@link #startTrackingWifiChange}
     */
    @Deprecated
    public interface WifiChangeListener extends ActionListener {
        /** indicates that changes were detected in wifi environment
         * @param results indicate the access points that exhibited change
         */
        public void onChanging(ScanResult[] results);           /* changes are found */
        /** indicates that no wifi changes are being detected for a while
         * @param results indicate the access points that are bing monitored for change
         */
        public void onQuiescence(ScanResult[] results);         /* changes settled down */
    }

    /**
     * track changes in wifi environment
     * @param listener object to report events on; this object must be unique and must also be
     *                 provided on {@link #stopTrackingWifiChange}
     */
    @Deprecated
    @SuppressLint("RequiresPermission")
    public void startTrackingWifiChange(WifiChangeListener listener) {
        throw new UnsupportedOperationException();
    }

    /**
     * stop tracking changes in wifi environment
     * @param listener object that was provided to report events on {@link
     * #stopTrackingWifiChange}
     */
    @Deprecated
    @SuppressLint("RequiresPermission")
    public void stopTrackingWifiChange(WifiChangeListener listener) {
        throw new UnsupportedOperationException();
    }

    /** @hide */
    @SystemApi
    @Deprecated
    @SuppressLint("RequiresPermission")
    public void configureWifiChange(WifiChangeSettings settings) {
        throw new UnsupportedOperationException();
    }

    /** interface to receive hotlist events on; use this on {@link #setHotlist} */
    @Deprecated
    public static interface BssidListener extends ActionListener {
        /** indicates that access points were found by on going scans
         * @param results list of scan results, one for each access point visible currently
         */
        public void onFound(ScanResult[] results);
        /** indicates that access points were missed by on going scans
         * @param results list of scan results, for each access point that is not visible anymore
         */
        public void onLost(ScanResult[] results);
    }

    /** @hide */
    @SystemApi
    @Deprecated
    public static class HotlistSettings implements Parcelable {
        public BssidInfo[] bssidInfos;
        public int apLostThreshold;

        /** Implement the Parcelable interface {@hide} */
        public int describeContents() {
            return 0;
        }

        /** Implement the Parcelable interface {@hide} */
        public void writeToParcel(Parcel dest, int flags) {
        }

        /** Implement the Parcelable interface {@hide} */
        public static final @NonNull Creator<HotlistSettings> CREATOR =
                new Creator<HotlistSettings>() {
                    public HotlistSettings createFromParcel(Parcel in) {
                        HotlistSettings settings = new HotlistSettings();
                        return settings;
                    }

                    public HotlistSettings[] newArray(int size) {
                        return new HotlistSettings[size];
                    }
                };
    }

    /**
     * set interesting access points to find
     * @param bssidInfos access points of interest
     * @param apLostThreshold number of scans needed to indicate that AP is lost
     * @param listener object provided to report events on; this object must be unique and must
     *                 also be provided on {@link #stopTrackingBssids}
     */
    @Deprecated
    @SuppressLint("RequiresPermission")
    public void startTrackingBssids(BssidInfo[] bssidInfos,
                                    int apLostThreshold, BssidListener listener) {
        throw new UnsupportedOperationException();
    }

    /**
     * remove tracking of interesting access points
     * @param listener same object provided in {@link #startTrackingBssids}
     */
    @Deprecated
    @SuppressLint("RequiresPermission")
    public void stopTrackingBssids(BssidListener listener) {
        throw new UnsupportedOperationException();
    }


    /* private members and methods */

    private static final String TAG = "WifiScanner";
    private static final boolean DBG = false;

    /* commands for Wifi Service */
    private static final int BASE = Protocol.BASE_WIFI_SCANNER;

    /** @hide */
    public static final int CMD_START_BACKGROUND_SCAN       = BASE + 2;
    /** @hide */
    public static final int CMD_STOP_BACKGROUND_SCAN        = BASE + 3;
    /** @hide */
    public static final int CMD_GET_SCAN_RESULTS            = BASE + 4;
    /** @hide */
    public static final int CMD_SCAN_RESULT                 = BASE + 5;
    /** @hide */
    public static final int CMD_OP_SUCCEEDED                = BASE + 17;
    /** @hide */
    public static final int CMD_OP_FAILED                   = BASE + 18;
    /** @hide */
    public static final int CMD_FULL_SCAN_RESULT            = BASE + 20;
    /** @hide */
    public static final int CMD_START_SINGLE_SCAN           = BASE + 21;
    /** @hide */
    public static final int CMD_STOP_SINGLE_SCAN            = BASE + 22;
    /** @hide */
    public static final int CMD_SINGLE_SCAN_COMPLETED       = BASE + 23;
    /** @hide */
    public static final int CMD_START_PNO_SCAN              = BASE + 24;
    /** @hide */
    public static final int CMD_STOP_PNO_SCAN               = BASE + 25;
    /** @hide */
    public static final int CMD_PNO_NETWORK_FOUND           = BASE + 26;
    /** @hide */
    public static final int CMD_REGISTER_SCAN_LISTENER      = BASE + 27;
    /** @hide */
    public static final int CMD_DEREGISTER_SCAN_LISTENER    = BASE + 28;
    /** @hide */
    public static final int CMD_GET_SINGLE_SCAN_RESULTS     = BASE + 29;
    /** @hide */
    public static final int CMD_ENABLE                      = BASE + 30;
    /** @hide */
    public static final int CMD_DISABLE                     = BASE + 31;

    private Context mContext;
    private IWifiScanner mService;

    private final Object mListenerMapLock = new Object();
    private final Map<ActionListener, ServiceListener> mListenerMap = new HashMap<>();

    /**
     * Create a new WifiScanner instance.
     * Applications will almost always want to use
     * {@link android.content.Context#getSystemService Context.getSystemService()} to retrieve
     * the standard {@link android.content.Context#WIFI_SERVICE Context.WIFI_SERVICE}.
     *
     * @param context the application context
     * @param service the Binder interface for {@link Context#WIFI_SCANNING_SERVICE}
     * @param looper the Looper used to deliver callbacks
     *
     * @hide
     */
    public WifiScanner(@NonNull Context context, @NonNull IWifiScanner service,
            @NonNull Looper looper) {
        mContext = context;
        mService = service;
    }

    // Add a listener into listener map. If the listener already exists, return INVALID_KEY and
    // send an error message to internal handler; Otherwise add the listener to the listener map and
    // return the key of the listener.
    private boolean addListener(ActionListener listener, ServiceListener serviceListener) {
        synchronized (mListenerMapLock) {
            boolean keyExists = mListenerMap.containsKey(listener);
            // Note we need to put the listener into listener map even if it's a duplicate as the
            // internal handler will need the key to find the listener. In case of duplicates,
            // removing duplicate key logic will be handled in internal handler.
            if (keyExists) {
                if (DBG) Log.d(TAG, "listener key already exists");
                return false;
            }
            mListenerMap.put(listener, serviceListener);
            return true;
        }
    }

    private ServiceListener getServiceListener(ActionListener listener) {
        if (listener == null) return null;
        synchronized (mListenerMapLock) {
            return mListenerMap.get(listener);
        }
    }

    private void removeListener(ActionListener listener) {
        if (listener == null) return;
        synchronized (mListenerMapLock) {
            mListenerMap.remove(listener);
        }
    }

}