/*
 * Copyright (C) 2015 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.settingslib.wifi;

import android.annotation.MainThread;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.database.ContentObserver;
import android.net.ConnectivityManager;
import android.net.Network;
import android.net.NetworkCapabilities;
import android.net.NetworkInfo;
import android.net.NetworkInfo.DetailedState;
import android.net.NetworkKey;
import android.net.NetworkRequest;
import android.net.NetworkScoreManager;
import android.net.ScoredNetwork;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiConfiguration;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.net.wifi.WifiNetworkScoreCache;
import android.net.wifi.WifiNetworkScoreCache.CacheListener;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.provider.Settings;
import android.support.annotation.GuardedBy;
import android.util.ArraySet;
import android.util.Log;
import android.util.SparseArray;
import android.util.SparseIntArray;
import android.widget.Toast;

import com.android.internal.annotations.VisibleForTesting;
import com.android.settingslib.R;

import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Tracks saved or available wifi networks and their state.
 */
public class WifiTracker {
    // TODO(b/36733768): Remove flag includeSaved and includePasspoints.

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

    /** verbose logging flag. this flag is set thru developer debugging options
     * and used so as to assist with in-the-field WiFi connectivity debugging  */
    public static int sVerboseLogging = 0;

    // TODO: Allow control of this?
    // Combo scans can take 5-6s to complete - set to 10s.
    private static final int WIFI_RESCAN_INTERVAL_MS = 10 * 1000;
    private static final int NUM_SCANS_TO_CONFIRM_AP_LOSS = 3;

    private final Context mContext;
    private final WifiManager mWifiManager;
    private final IntentFilter mFilter;
    private final ConnectivityManager mConnectivityManager;
    private final NetworkRequest mNetworkRequest;
    private final AtomicBoolean mConnected = new AtomicBoolean(false);
    private final WifiListener mListener;
    private final boolean mIncludeSaved;
    private final boolean mIncludeScans;
    private final boolean mIncludePasspoints;
    @VisibleForTesting final MainHandler mMainHandler;
    @VisibleForTesting final WorkHandler mWorkHandler;

    private WifiTrackerNetworkCallback mNetworkCallback;

    @GuardedBy("mLock")
    private boolean mRegistered;

    /**
     * The externally visible access point list.
     *
     * Updated using main handler. Clone of this collection is returned from
     * {@link #getAccessPoints()}
     */
    private final List<AccessPoint> mAccessPoints = new ArrayList<>();

    /**
     * The internal list of access points, synchronized on itself.
     *
     * Never exposed outside this class.
     */
    @GuardedBy("mLock")
    private final List<AccessPoint> mInternalAccessPoints = new ArrayList<>();

    /**
    * Synchronization lock for managing concurrency between main and worker threads.
    *
    * <p>This lock should be held for all background work.
    * TODO(b/37674366): Remove the worker thread so synchronization is no longer necessary.
    */
    private final Object mLock = new Object();

    //visible to both worker and main thread.
    @GuardedBy("mLock")
    private final AccessPointListenerAdapter mAccessPointListenerAdapter
            = new AccessPointListenerAdapter();

    private final HashMap<String, Integer> mSeenBssids = new HashMap<>();
    private final HashMap<String, ScanResult> mScanResultCache = new HashMap<>();
    private Integer mScanId = 0;

    private NetworkInfo mLastNetworkInfo;
    private WifiInfo mLastInfo;

    private final NetworkScoreManager mNetworkScoreManager;
    private final WifiNetworkScoreCache mScoreCache;
    private boolean mNetworkScoringUiEnabled;
    private final ContentObserver mObserver;

    @GuardedBy("mLock")
    private final Set<NetworkKey> mRequestedScores = new ArraySet<>();

    @VisibleForTesting
    Scanner mScanner;
    private boolean mStaleScanResults = true;

    public WifiTracker(Context context, WifiListener wifiListener,
            boolean includeSaved, boolean includeScans) {
        this(context, wifiListener, null, includeSaved, includeScans);
    }

    public WifiTracker(Context context, WifiListener wifiListener, Looper workerLooper,
            boolean includeSaved, boolean includeScans) {
        this(context, wifiListener, workerLooper, includeSaved, includeScans, false);
    }

    public WifiTracker(Context context, WifiListener wifiListener,
            boolean includeSaved, boolean includeScans, boolean includePasspoints) {
        this(context, wifiListener, null, includeSaved, includeScans, includePasspoints);
    }

    public WifiTracker(Context context, WifiListener wifiListener, Looper workerLooper,
            boolean includeSaved, boolean includeScans, boolean includePasspoints) {
        this(context, wifiListener, workerLooper, includeSaved, includeScans, includePasspoints,
                context.getSystemService(WifiManager.class),
                context.getSystemService(ConnectivityManager.class),
                context.getSystemService(NetworkScoreManager.class), Looper.myLooper()
        );
    }

    @VisibleForTesting
    WifiTracker(Context context, WifiListener wifiListener, Looper workerLooper,
            boolean includeSaved, boolean includeScans, boolean includePasspoints,
            WifiManager wifiManager, ConnectivityManager connectivityManager,
            NetworkScoreManager networkScoreManager, Looper currentLooper) {
        if (!includeSaved && !includeScans) {
            throw new IllegalArgumentException("Must include either saved or scans");
        }
        mContext = context;
        if (currentLooper == null) {
            // When we aren't on a looper thread, default to the main.
            currentLooper = Looper.getMainLooper();
        }
        mMainHandler = new MainHandler(currentLooper);
        mWorkHandler = new WorkHandler(
                workerLooper != null ? workerLooper : currentLooper);
        mWifiManager = wifiManager;
        mIncludeSaved = includeSaved;
        mIncludeScans = includeScans;
        mIncludePasspoints = includePasspoints;
        mListener = wifiListener;
        mConnectivityManager = connectivityManager;

        // check if verbose logging has been turned on or off
        sVerboseLogging = mWifiManager.getVerboseLoggingLevel();

        mFilter = new IntentFilter();
        mFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
        mFilter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
        mFilter.addAction(WifiManager.NETWORK_IDS_CHANGED_ACTION);
        mFilter.addAction(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION);
        mFilter.addAction(WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION);
        mFilter.addAction(WifiManager.LINK_CONFIGURATION_CHANGED_ACTION);
        mFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
        mFilter.addAction(WifiManager.RSSI_CHANGED_ACTION);

        mNetworkRequest = new NetworkRequest.Builder()
                .clearCapabilities()
                .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
                .build();

        mNetworkScoreManager = networkScoreManager;

        mScoreCache = new WifiNetworkScoreCache(context, new CacheListener(mWorkHandler) {
            @Override
            public void networkCacheUpdated(List<ScoredNetwork> networks) {
                synchronized (mLock) {
                    if (!mRegistered) return;
                }

                if (Log.isLoggable(TAG, Log.VERBOSE)) {
                    Log.v(TAG, "Score cache was updated with networks: " + networks);
                }
                updateNetworkScores();
            }
        });

        mObserver = new ContentObserver(mWorkHandler) {
            @Override
            public void onChange(boolean selfChange) {
                mNetworkScoringUiEnabled =
                        Settings.Global.getInt(
                                mContext.getContentResolver(),
                                Settings.Global.NETWORK_SCORING_UI_ENABLED, 0) == 1;
            }
        };
    }

    /**
     * Synchronously update the list of access points with the latest information.
     */
    @MainThread
    public void forceUpdate() {
        synchronized (mLock) {
            mWorkHandler.removeMessages(WorkHandler.MSG_UPDATE_ACCESS_POINTS);
            mLastInfo = mWifiManager.getConnectionInfo();
            mLastNetworkInfo = mConnectivityManager.getNetworkInfo(mWifiManager.getCurrentNetwork());

            final List<ScanResult> newScanResults = mWifiManager.getScanResults();
            List<WifiConfiguration> configs = mWifiManager.getConfiguredNetworks();
            updateAccessPointsLocked(newScanResults, configs);

            if (DBG) {
                Log.d(TAG, "force update - internal access point list:\n" + mInternalAccessPoints);
            }

            // Synchronously copy access points
            mMainHandler.removeMessages(MainHandler.MSG_ACCESS_POINT_CHANGED);
            mMainHandler.handleMessage(
                    Message.obtain(mMainHandler, MainHandler.MSG_ACCESS_POINT_CHANGED));
            if (DBG) {
                Log.d(TAG, "force update - external access point list:\n" + mAccessPoints);
            }
        }
    }

    /**
     * Force a scan for wifi networks to happen now.
     */
    public void forceScan() {
        if (mWifiManager.isWifiEnabled() && mScanner != null) {
            mScanner.forceScan();
        }
    }

    /**
     * Temporarily stop scanning for wifi networks.
     */
    public void pauseScanning() {
        if (mScanner != null) {
            mScanner.pause();
            mScanner = null;
        }
    }

    /**
     * Resume scanning for wifi networks after it has been paused.
     *
     * <p>The score cache should be registered before this method is invoked.
     */
    public void resumeScanning() {
        if (mScanner == null) {
            mScanner = new Scanner();
        }

        mWorkHandler.sendEmptyMessage(WorkHandler.MSG_RESUME);
        if (mWifiManager.isWifiEnabled()) {
            mScanner.resume();
        }
    }

    /**
     * Start tracking wifi networks and scores.
     *
     * <p>Registers listeners and starts scanning for wifi networks. If this is not called
     * then forceUpdate() must be called to populate getAccessPoints().
     */
    @MainThread
    public void startTracking() {
        synchronized (mLock) {
            registerScoreCache();

            mContext.getContentResolver().registerContentObserver(
                    Settings.Global.getUriFor(Settings.Global.NETWORK_SCORING_UI_ENABLED),
                    false /* notifyForDescendants */,
                    mObserver);
            mObserver.onChange(false /* selfChange */); // Set mScoringUiEnabled

            resumeScanning();
            if (!mRegistered) {
                mContext.registerReceiver(mReceiver, mFilter);
                // NetworkCallback objects cannot be reused. http://b/20701525 .
                mNetworkCallback = new WifiTrackerNetworkCallback();
                mConnectivityManager.registerNetworkCallback(mNetworkRequest, mNetworkCallback);
                mRegistered = true;
            }
        }
    }

    private void registerScoreCache() {
        mNetworkScoreManager.registerNetworkScoreCache(
                NetworkKey.TYPE_WIFI,
                mScoreCache,
                NetworkScoreManager.CACHE_FILTER_SCAN_RESULTS);
    }

    private void requestScoresForNetworkKeys(Collection<NetworkKey> keys) {
        if (keys.isEmpty()) return;

        if (DBG) {
            Log.d(TAG, "Requesting scores for Network Keys: " + keys);
        }
        mNetworkScoreManager.requestScores(keys.toArray(new NetworkKey[keys.size()]));
        synchronized (mLock) {
            mRequestedScores.addAll(keys);
        }
    }

    /**
     * Stop tracking wifi networks and scores.
     *
     * <p>This should always be called when done with a WifiTracker (if startTracking was called) to
     * ensure proper cleanup and prevent any further callbacks from occurring.
     *
     * <p>Calling this method will set the {@link #mStaleScanResults} bit, which prevents
     * {@link WifiListener#onAccessPointsChanged()} callbacks from being invoked (until the bit
     * is unset on the next SCAN_RESULTS_AVAILABLE_ACTION).
     */
    @MainThread
    public void stopTracking() {
        synchronized (mLock) {
            if (mRegistered) {
                mContext.unregisterReceiver(mReceiver);
                mConnectivityManager.unregisterNetworkCallback(mNetworkCallback);
                mRegistered = false;
            }
            unregisterAndClearScoreCache();
            pauseScanning();
            mContext.getContentResolver().unregisterContentObserver(mObserver);

            mWorkHandler.removePendingMessages();
            mMainHandler.removePendingMessages();
        }
        mStaleScanResults = true;
    }

    private void unregisterAndClearScoreCache() {
        mNetworkScoreManager.unregisterNetworkScoreCache(NetworkKey.TYPE_WIFI, mScoreCache);
        mScoreCache.clearScores();

        // Synchronize on mLock to avoid concurrent modification during updateAccessPoints
        synchronized (mLock) {
            mRequestedScores.clear();
        }
    }

    /**
     * Gets the current list of access points. Should be called from main thread, otherwise
     * expect inconsistencies
     */
    @MainThread
    public List<AccessPoint> getAccessPoints() {
        return new ArrayList<>(mAccessPoints);
    }

    public WifiManager getManager() {
        return mWifiManager;
    }

    public boolean isWifiEnabled() {
        return mWifiManager.isWifiEnabled();
    }

    /**
     * Returns the number of saved networks on the device, regardless of whether the WifiTracker
     * is tracking saved networks.
     * TODO(b/62292448): remove this function and update callsites to use WifiSavedConfigUtils
     * directly.
     */
    public int getNumSavedNetworks() {
        return WifiSavedConfigUtils.getAllConfigs(mContext, mWifiManager).size();
    }

    public boolean isConnected() {
        return mConnected.get();
    }

    public void dump(PrintWriter pw) {
        pw.println("  - wifi tracker ------");
        for (AccessPoint accessPoint : getAccessPoints()) {
            pw.println("  " + accessPoint);
        }
    }

    private void handleResume() {
        mScanResultCache.clear();
        mSeenBssids.clear();
        mScanId = 0;
    }

    private Collection<ScanResult> updateScanResultCache(final List<ScanResult> newResults) {
        mScanId++;
        for (ScanResult newResult : newResults) {
            if (newResult.SSID == null || newResult.SSID.isEmpty()) {
                continue;
            }
            mScanResultCache.put(newResult.BSSID, newResult);
            mSeenBssids.put(newResult.BSSID, mScanId);
        }

        if (mScanId > NUM_SCANS_TO_CONFIRM_AP_LOSS) {
            if (DBG) Log.d(TAG, "------ Dumping SSIDs that were expired on this scan ------");
            Integer threshold = mScanId - NUM_SCANS_TO_CONFIRM_AP_LOSS;
            for (Iterator<Map.Entry<String, Integer>> it = mSeenBssids.entrySet().iterator();
                    it.hasNext(); /* nothing */) {
                Map.Entry<String, Integer> e = it.next();
                if (e.getValue() < threshold) {
                    ScanResult result = mScanResultCache.get(e.getKey());
                    if (DBG) Log.d(TAG, "Removing " + e.getKey() + ":(" + result.SSID + ")");
                    mScanResultCache.remove(e.getKey());
                    it.remove();
                }
            }
            if (DBG) Log.d(TAG, "---- Done Dumping SSIDs that were expired on this scan ----");
        }

        return mScanResultCache.values();
    }

    private WifiConfiguration getWifiConfigurationForNetworkId(
            int networkId, final List<WifiConfiguration> configs) {
        if (configs != null) {
            for (WifiConfiguration config : configs) {
                if (mLastInfo != null && networkId == config.networkId &&
                        !(config.selfAdded && config.numAssociation == 0)) {
                    return config;
                }
            }
        }
        return null;
    }

    /**
     * Safely modify {@link #mInternalAccessPoints} by acquiring {@link #mLock} first.
     *
     * <p>Will not perform the update if {@link #mStaleScanResults} is true
     */
    private void updateAccessPoints() {
        List<WifiConfiguration> configs = mWifiManager.getConfiguredNetworks();
        final List<ScanResult> newScanResults = mWifiManager.getScanResults();

        synchronized (mLock) {
            if(!mStaleScanResults) {
                updateAccessPointsLocked(newScanResults, configs);
            }
        }
    }

    /**
     * Update the internal list of access points.
     *
     * <p>Do not called directly (except for forceUpdate), use {@link #updateAccessPoints()} which
     * respects {@link #mStaleScanResults}.
     */
    @GuardedBy("mLock")
    private void updateAccessPointsLocked(final List<ScanResult> newScanResults,
            List<WifiConfiguration> configs) {
        WifiConfiguration connectionConfig = null;
        if (mLastInfo != null) {
            connectionConfig = getWifiConfigurationForNetworkId(
                    mLastInfo.getNetworkId(), mWifiManager.getConfiguredNetworks());
        }

        // Swap the current access points into a cached list.
        List<AccessPoint> cachedAccessPoints = new ArrayList<>(mInternalAccessPoints);
        ArrayList<AccessPoint> accessPoints = new ArrayList<>();

        // Clear out the configs so we don't think something is saved when it isn't.
        for (AccessPoint accessPoint : cachedAccessPoints) {
            accessPoint.clearConfig();
        }

    /* Lookup table to more quickly update AccessPoints by only considering objects with the
     * correct SSID.  Maps SSID -> List of AccessPoints with the given SSID.  */
        Multimap<String, AccessPoint> apMap = new Multimap<String, AccessPoint>();

        final Collection<ScanResult> results = updateScanResultCache(newScanResults);

        if (configs != null) {
            for (WifiConfiguration config : configs) {
                if (config.selfAdded && config.numAssociation == 0) {
                    continue;
                }
                AccessPoint accessPoint = getCachedOrCreate(config, cachedAccessPoints);
                if (mLastInfo != null && mLastNetworkInfo != null) {
                    accessPoint.update(connectionConfig, mLastInfo, mLastNetworkInfo);
                }
                if (mIncludeSaved) {
                    // If saved network not present in scan result then set its Rssi to
                    // UNREACHABLE_RSSI
                    boolean apFound = false;
                    for (ScanResult result : results) {
                        if (result.SSID.equals(accessPoint.getSsidStr())) {
                            apFound = true;
                            break;
                        }
                    }
                    if (!apFound) {
                        accessPoint.setUnreachable();
                    }
                    accessPoints.add(accessPoint);
                    apMap.put(accessPoint.getSsidStr(), accessPoint);
                } else {
                    // If we aren't using saved networks, drop them into the cache so that
                    // we have access to their saved info.
                    cachedAccessPoints.add(accessPoint);
                }
            }
        }

        final List<NetworkKey> scoresToRequest = new ArrayList<>();
        if (results != null) {
            for (ScanResult result : results) {
                // Ignore hidden and ad-hoc networks.
                if (result.SSID == null || result.SSID.length() == 0 ||
                        result.capabilities.contains("[IBSS]")) {
                    continue;
                }

                NetworkKey key = NetworkKey.createFromScanResult(result);
                if (key != null && !mRequestedScores.contains(key)) {
                    scoresToRequest.add(key);
                }

                boolean found = false;
                for (AccessPoint accessPoint : apMap.getAll(result.SSID)) {
                    if (accessPoint.update(result)) {
                        found = true;
                        break;
                    }
                }
                if (!found && mIncludeScans) {
                    AccessPoint accessPoint = getCachedOrCreate(result, cachedAccessPoints);
                    if (mLastInfo != null && mLastNetworkInfo != null) {
                        accessPoint.update(connectionConfig, mLastInfo, mLastNetworkInfo);
                    }

                    if (result.isPasspointNetwork()) {
                        // Retrieve a WifiConfiguration for a Passpoint provider that matches
                        // the given ScanResult.  This is used for showing that a given AP
                        // (ScanResult) is available via a Passpoint provider (provider friendly
                        // name).
                        try {
                            WifiConfiguration config = mWifiManager.getMatchingWifiConfig(result);
                            if (config != null) {
                                accessPoint.update(config);
                            }
                        } catch (UnsupportedOperationException e) {
                            // Passpoint not supported on the device.
                        }
                    }

                    accessPoints.add(accessPoint);
                    apMap.put(accessPoint.getSsidStr(), accessPoint);
                }
            }
        }

        requestScoresForNetworkKeys(scoresToRequest);
        for (AccessPoint ap : accessPoints) {
            ap.update(mScoreCache, mNetworkScoringUiEnabled);
        }

        // Pre-sort accessPoints to speed preference insertion
        Collections.sort(accessPoints);

        // Log accesspoints that were deleted
        if (DBG) {
            Log.d(TAG, "------ Dumping SSIDs that were not seen on this scan ------");
            for (AccessPoint prevAccessPoint : mInternalAccessPoints) {
                if (prevAccessPoint.getSsid() == null)
                    continue;
                String prevSsid = prevAccessPoint.getSsidStr();
                boolean found = false;
                for (AccessPoint newAccessPoint : accessPoints) {
                    if (newAccessPoint.getSsid() != null && newAccessPoint.getSsid()
                            .equals(prevSsid)) {
                        found = true;
                        break;
                    }
                }
                if (!found)
                    Log.d(TAG, "Did not find " + prevSsid + " in this scan");
            }
            Log.d(TAG, "---- Done dumping SSIDs that were not seen on this scan ----");
        }

        mInternalAccessPoints.clear();
        mInternalAccessPoints.addAll(accessPoints);

        mMainHandler.sendEmptyMessage(MainHandler.MSG_ACCESS_POINT_CHANGED);
    }

    @VisibleForTesting
    AccessPoint getCachedOrCreate(ScanResult result, List<AccessPoint> cache) {
        final int N = cache.size();
        for (int i = 0; i < N; i++) {
            if (cache.get(i).matches(result)) {
                AccessPoint ret = cache.remove(i);
                ret.update(result);
                return ret;
            }
        }
        final AccessPoint accessPoint = new AccessPoint(mContext, result);
        accessPoint.setListener(mAccessPointListenerAdapter);
        return accessPoint;
    }

    @VisibleForTesting
    AccessPoint getCachedOrCreate(WifiConfiguration config, List<AccessPoint> cache) {
        final int N = cache.size();
        for (int i = 0; i < N; i++) {
            if (cache.get(i).matches(config)) {
                AccessPoint ret = cache.remove(i);
                ret.loadConfig(config);
                return ret;
            }
        }
        final AccessPoint accessPoint = new AccessPoint(mContext, config);
        accessPoint.setListener(mAccessPointListenerAdapter);
        return accessPoint;
    }

    private void updateNetworkInfo(NetworkInfo networkInfo) {
        /* sticky broadcasts can call this when wifi is disabled */
        if (!mWifiManager.isWifiEnabled()) {
            mMainHandler.sendEmptyMessage(MainHandler.MSG_PAUSE_SCANNING);
            clearAccessPointsAndConditionallyUpdate();
            return;
        }

        if (networkInfo != null &&
                networkInfo.getDetailedState() == DetailedState.OBTAINING_IPADDR) {
            mMainHandler.sendEmptyMessage(MainHandler.MSG_PAUSE_SCANNING);
        } else {
            mMainHandler.sendEmptyMessage(MainHandler.MSG_RESUME_SCANNING);
        }

        if (networkInfo != null) {
            mLastNetworkInfo = networkInfo;
        }

        WifiConfiguration connectionConfig = null;
        mLastInfo = mWifiManager.getConnectionInfo();
        if (mLastInfo != null) {
            connectionConfig = getWifiConfigurationForNetworkId(mLastInfo.getNetworkId(),
                    mWifiManager.getConfiguredNetworks());
        }

        boolean updated = false;
        boolean reorder = false; // Only reorder if connected AP was changed

        synchronized (mLock) {
            for (int i = mInternalAccessPoints.size() - 1; i >= 0; --i) {
                AccessPoint ap = mInternalAccessPoints.get(i);
                boolean previouslyConnected = ap.isActive();
                if (ap.update(connectionConfig, mLastInfo, mLastNetworkInfo)) {
                    updated = true;
                    if (previouslyConnected != ap.isActive()) reorder = true;
                }
                if (ap.update(mScoreCache, mNetworkScoringUiEnabled)) {
                    reorder = true;
                    updated = true;
                }
            }

            if (reorder) Collections.sort(mInternalAccessPoints);

            if (updated) mMainHandler.sendEmptyMessage(MainHandler.MSG_ACCESS_POINT_CHANGED);
        }
    }

    private void clearAccessPointsAndConditionallyUpdate() {
        synchronized (mLock) {
            if (!mInternalAccessPoints.isEmpty()) {
                mInternalAccessPoints.clear();
                if (!mMainHandler.hasMessages(MainHandler.MSG_ACCESS_POINT_CHANGED)) {
                    mMainHandler.sendEmptyMessage(MainHandler.MSG_ACCESS_POINT_CHANGED);
                }
            }
        }
    }

    /**
     * Update all the internal access points rankingScores, badge and metering.
     *
     * <p>Will trigger a resort and notify listeners of changes if applicable.
     *
     * <p>Synchronized on {@link #mLock}.
     */
    private void updateNetworkScores() {
        synchronized (mLock) {
            boolean updated = false;
            for (int i = 0; i < mInternalAccessPoints.size(); i++) {
                if (mInternalAccessPoints.get(i).update(mScoreCache, mNetworkScoringUiEnabled)) {
                    updated = true;
                }
            }
            if (updated) {
                Collections.sort(mInternalAccessPoints);
                mMainHandler.sendEmptyMessage(MainHandler.MSG_ACCESS_POINT_CHANGED);
            }
        }
    }

    private void updateWifiState(int state) {
        mWorkHandler.obtainMessage(WorkHandler.MSG_UPDATE_WIFI_STATE, state, 0).sendToTarget();
        if (!mWifiManager.isWifiEnabled()) {
            clearAccessPointsAndConditionallyUpdate();
        }
    }

    public static List<AccessPoint> getCurrentAccessPoints(Context context, boolean includeSaved,
            boolean includeScans, boolean includePasspoints) {
        WifiTracker tracker = new WifiTracker(context,
                null, null, includeSaved, includeScans, includePasspoints);
        tracker.forceUpdate();
        tracker.copyAndNotifyListeners(false /*notifyListeners*/);
        return tracker.getAccessPoints();
    }

    @VisibleForTesting
    final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if (WifiManager.WIFI_STATE_CHANGED_ACTION.equals(action)) {
                updateWifiState(intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
                        WifiManager.WIFI_STATE_UNKNOWN));
            } else if (WifiManager.SCAN_RESULTS_AVAILABLE_ACTION.equals(action)) {
                mWorkHandler
                        .obtainMessage(
                            WorkHandler.MSG_UPDATE_ACCESS_POINTS,
                            WorkHandler.CLEAR_STALE_SCAN_RESULTS,
                            0)
                        .sendToTarget();
            } else if (WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION.equals(action)
                    || WifiManager.LINK_CONFIGURATION_CHANGED_ACTION.equals(action)) {
                mWorkHandler.sendEmptyMessage(WorkHandler.MSG_UPDATE_ACCESS_POINTS);
            } else if (WifiManager.NETWORK_STATE_CHANGED_ACTION.equals(action)) {
                NetworkInfo info = intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO);
                mConnected.set(info.isConnected());

                mMainHandler.sendEmptyMessage(MainHandler.MSG_CONNECTED_CHANGED);

                mWorkHandler.obtainMessage(WorkHandler.MSG_UPDATE_NETWORK_INFO, info)
                        .sendToTarget();
                mWorkHandler.sendEmptyMessage(WorkHandler.MSG_UPDATE_ACCESS_POINTS);
            } else if (WifiManager.RSSI_CHANGED_ACTION.equals(action)) {
                NetworkInfo info =
                        mConnectivityManager.getNetworkInfo(mWifiManager.getCurrentNetwork());
                mWorkHandler.obtainMessage(WorkHandler.MSG_UPDATE_NETWORK_INFO, info)
                        .sendToTarget();
            }
        }
    };

    private final class WifiTrackerNetworkCallback extends ConnectivityManager.NetworkCallback {
        public void onCapabilitiesChanged(Network network, NetworkCapabilities nc) {
            if (network.equals(mWifiManager.getCurrentNetwork())) {
                // We don't send a NetworkInfo object along with this message, because even if we
                // fetch one from ConnectivityManager, it might be older than the most recent
                // NetworkInfo message we got via a WIFI_STATE_CHANGED broadcast.
                mWorkHandler.sendEmptyMessage(WorkHandler.MSG_UPDATE_NETWORK_INFO);
            }
        }
    }

    @VisibleForTesting
    final class MainHandler extends Handler {
        @VisibleForTesting static final int MSG_CONNECTED_CHANGED = 0;
        @VisibleForTesting static final int MSG_WIFI_STATE_CHANGED = 1;
        @VisibleForTesting static final int MSG_ACCESS_POINT_CHANGED = 2;
        private static final int MSG_RESUME_SCANNING = 3;
        private static final int MSG_PAUSE_SCANNING = 4;

        public MainHandler(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            if (mListener == null) {
                return;
            }
            switch (msg.what) {
                case MSG_CONNECTED_CHANGED:
                    mListener.onConnectedChanged();
                    break;
                case MSG_WIFI_STATE_CHANGED:
                    mListener.onWifiStateChanged(msg.arg1);
                    break;
                case MSG_ACCESS_POINT_CHANGED:
                    // Only notify listeners of changes if we have fresh scan results, otherwise the
                    // UI will be updated with stale results. We want to copy the APs regardless,
                    // for instances where forceUpdate was invoked by the caller.
                    if (mStaleScanResults) {
                        copyAndNotifyListeners(false /*notifyListeners*/);
                    } else {
                        copyAndNotifyListeners(true /*notifyListeners*/);
                        mListener.onAccessPointsChanged();
                    }
                    break;
                case MSG_RESUME_SCANNING:
                    if (mScanner != null) {
                        mScanner.resume();
                    }
                    break;
                case MSG_PAUSE_SCANNING:
                    if (mScanner != null) {
                        mScanner.pause();
                    }
                    break;
            }
        }

        void removePendingMessages() {
            removeMessages(MSG_ACCESS_POINT_CHANGED);
            removeMessages(MSG_CONNECTED_CHANGED);
            removeMessages(MSG_WIFI_STATE_CHANGED);
            removeMessages(MSG_PAUSE_SCANNING);
            removeMessages(MSG_RESUME_SCANNING);
        }
    }

    @VisibleForTesting
    final class WorkHandler extends Handler {
        private static final int MSG_UPDATE_ACCESS_POINTS = 0;
        private static final int MSG_UPDATE_NETWORK_INFO = 1;
        private static final int MSG_RESUME = 2;
        private static final int MSG_UPDATE_WIFI_STATE = 3;

        private static final int CLEAR_STALE_SCAN_RESULTS = 1;

        public WorkHandler(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            synchronized (mLock) {
                processMessage(msg);
            }
        }

        private void processMessage(Message msg) {
            if (!mRegistered) return;

            switch (msg.what) {
                case MSG_UPDATE_ACCESS_POINTS:
                    if (msg.arg1 == CLEAR_STALE_SCAN_RESULTS) {
                        mStaleScanResults = false;
                    }
                    updateAccessPoints();
                    break;
                case MSG_UPDATE_NETWORK_INFO:
                    updateNetworkInfo((NetworkInfo) msg.obj);
                    break;
                case MSG_RESUME:
                    handleResume();
                    break;
                case MSG_UPDATE_WIFI_STATE:
                    if (msg.arg1 == WifiManager.WIFI_STATE_ENABLED) {
                        if (mScanner != null) {
                            // We only need to resume if mScanner isn't null because
                            // that means we want to be scanning.
                            mScanner.resume();
                        }
                    } else {
                        mLastInfo = null;
                        mLastNetworkInfo = null;
                        if (mScanner != null) {
                            mScanner.pause();
                        }
                    }
                    mMainHandler.obtainMessage(MainHandler.MSG_WIFI_STATE_CHANGED, msg.arg1, 0)
                            .sendToTarget();
                    break;
            }
        }

        private void removePendingMessages() {
            removeMessages(MSG_UPDATE_ACCESS_POINTS);
            removeMessages(MSG_UPDATE_NETWORK_INFO);
            removeMessages(MSG_RESUME);
            removeMessages(MSG_UPDATE_WIFI_STATE);
        }
    }

    @VisibleForTesting
    class Scanner extends Handler {
        static final int MSG_SCAN = 0;

        private int mRetry = 0;

        void resume() {
            if (!hasMessages(MSG_SCAN)) {
                sendEmptyMessage(MSG_SCAN);
            }
        }

        void forceScan() {
            removeMessages(MSG_SCAN);
            sendEmptyMessage(MSG_SCAN);
        }

        void pause() {
            mRetry = 0;
            removeMessages(MSG_SCAN);
        }

        @VisibleForTesting
        boolean isScanning() {
            return hasMessages(MSG_SCAN);
        }

        @Override
        public void handleMessage(Message message) {
            if (message.what != MSG_SCAN) return;
            if (mWifiManager.startScan()) {
                mRetry = 0;
            } else if (++mRetry >= 3) {
                mRetry = 0;
                if (mContext != null) {
                    Toast.makeText(mContext, R.string.wifi_fail_to_scan, Toast.LENGTH_LONG).show();
                }
                return;
            }
            sendEmptyMessageDelayed(0, WIFI_RESCAN_INTERVAL_MS);
        }
    }

    /** A restricted multimap for use in constructAccessPoints */
    private static class Multimap<K,V> {
        private final HashMap<K,List<V>> store = new HashMap<K,List<V>>();
        /** retrieve a non-null list of values with key K */
        List<V> getAll(K key) {
            List<V> values = store.get(key);
            return values != null ? values : Collections.<V>emptyList();
        }

        void put(K key, V val) {
            List<V> curVals = store.get(key);
            if (curVals == null) {
                curVals = new ArrayList<V>(3);
                store.put(key, curVals);
            }
            curVals.add(val);
        }
    }

    public interface WifiListener {
        /**
         * Called when the state of Wifi has changed, the state will be one of
         * the following.
         *
         * <li>{@link WifiManager#WIFI_STATE_DISABLED}</li>
         * <li>{@link WifiManager#WIFI_STATE_ENABLED}</li>
         * <li>{@link WifiManager#WIFI_STATE_DISABLING}</li>
         * <li>{@link WifiManager#WIFI_STATE_ENABLING}</li>
         * <li>{@link WifiManager#WIFI_STATE_UNKNOWN}</li>
         * <p>
         *
         * @param state The new state of wifi.
         */
        void onWifiStateChanged(int state);

        /**
         * Called when the connection state of wifi has changed and isConnected
         * should be called to get the updated state.
         */
        void onConnectedChanged();

        /**
         * Called to indicate the list of AccessPoints has been updated and
         * getAccessPoints should be called to get the latest information.
         */
        void onAccessPointsChanged();
    }

    /**
     * Helps capture notifications that were generated during AccessPoint modification. Used later
     * on by {@link #copyAndNotifyListeners(boolean)} to send notifications.
     */
    private static class AccessPointListenerAdapter implements AccessPoint.AccessPointListener {
        static final int AP_CHANGED = 1;
        static final int LEVEL_CHANGED = 2;

        final SparseIntArray mPendingNotifications = new SparseIntArray();

        @Override
        public void onAccessPointChanged(AccessPoint accessPoint) {
            int type = mPendingNotifications.get(accessPoint.mId);
            mPendingNotifications.put(accessPoint.mId, type | AP_CHANGED);
        }

        @Override
        public void onLevelChanged(AccessPoint accessPoint) {
            int type = mPendingNotifications.get(accessPoint.mId);
            mPendingNotifications.put(accessPoint.mId, type | LEVEL_CHANGED);
        }
    }

    /**
     * Responsible for copying access points from {@link #mInternalAccessPoints} and notifying
     * accesspoint listeners.
     *
     * @param notifyListeners if true, accesspoint listeners are notified, otherwise notifications
     *                        dropped.
     */
    @MainThread
    private void copyAndNotifyListeners(boolean notifyListeners) {
        // Need to watch out for memory allocations on main thread.
        SparseArray<AccessPoint> oldAccessPoints = new SparseArray<>();
        SparseIntArray notificationMap = null;
        List<AccessPoint> updatedAccessPoints = new ArrayList<>();

        for (AccessPoint accessPoint : mAccessPoints) {
            oldAccessPoints.put(accessPoint.mId, accessPoint);
        }

        if (DBG) {
            Log.d(TAG, "Starting to copy AP items on the MainHandler");
        }
        synchronized (mLock) {
            if (notifyListeners) {
                notificationMap = mAccessPointListenerAdapter.mPendingNotifications.clone();
            }

            mAccessPointListenerAdapter.mPendingNotifications.clear();

            for (AccessPoint internalAccessPoint : mInternalAccessPoints) {
                AccessPoint accessPoint = oldAccessPoints.get(internalAccessPoint.mId);
                if (accessPoint == null) {
                    accessPoint = new AccessPoint(mContext, internalAccessPoint);
                } else {
                    accessPoint.copyFrom(internalAccessPoint);
                }
                updatedAccessPoints.add(accessPoint);
            }
        }

        mAccessPoints.clear();
        mAccessPoints.addAll(updatedAccessPoints);

        if (notificationMap != null && notificationMap.size() > 0) {
            for (AccessPoint accessPoint : updatedAccessPoints) {
                int notificationType = notificationMap.get(accessPoint.mId);
                AccessPoint.AccessPointListener listener = accessPoint.mAccessPointListener;
                if (notificationType == 0 || listener == null) {
                    continue;
                }

                if ((notificationType & AccessPointListenerAdapter.AP_CHANGED) != 0) {
                    listener.onAccessPointChanged(accessPoint);
                }

                if ((notificationType & AccessPointListenerAdapter.LEVEL_CHANGED) != 0) {
                    listener.onLevelChanged(accessPoint);
                }
            }
        }
    }
}