content: /*
   * Copyright (C) 2016 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.util;
  
  import static android.provider.Settings.Global.NETWORK_AVOID_BAD_WIFI;
  import static android.provider.Settings.Global.NETWORK_METERED_MULTIPATH_PREFERENCE;
  
  import android.annotation.NonNull;
  import android.content.BroadcastReceiver;
  import android.content.ContentResolver;
  import android.content.Context;
  import android.content.Intent;
  import android.content.IntentFilter;
  import android.content.res.Resources;
  import android.database.ContentObserver;
  import android.net.Uri;
  import android.os.Handler;
  import android.os.UserHandle;
  import android.provider.Settings;
  import android.telephony.PhoneStateListener;
  import android.telephony.SubscriptionManager;
  import android.telephony.TelephonyManager;
  import android.util.Slog;
  
  import com.android.internal.R;
  import com.android.internal.annotations.VisibleForTesting;
  
  import java.util.Arrays;
  import java.util.List;
  
  /**
   * A class to encapsulate management of the "Smart Networking" capability of
   * avoiding bad Wi-Fi when, for example upstream connectivity is lost or
   * certain critical link failures occur.
   *
   * This enables the device to switch to another form of connectivity, like
   * mobile, if it's available and working.
   *
   * The Runnable |avoidBadWifiCallback|, if given, is posted to the supplied
   * Handler' whenever the computed "avoid bad wifi" value changes.
   *
   * Disabling this reverts the device to a level of networking sophistication
   * circa 2012-13 by disabling disparate code paths each of which contribute to
   * maintaining continuous, working Internet connectivity.
   *
   * @hide
   */
  public class MultinetworkPolicyTracker {
      private static String TAG = MultinetworkPolicyTracker.class.getSimpleName();
  
      private final Context mContext;
      private final Handler mHandler;
      private final Runnable mReevaluateRunnable;
      private final List<Uri> mSettingsUris;
      private final ContentResolver mResolver;
      private final SettingObserver mSettingObserver;
      private final BroadcastReceiver mBroadcastReceiver;
  
      private volatile boolean mAvoidBadWifi = true;
      private volatile int mMeteredMultipathPreference;
      private int mActiveSubId = SubscriptionManager.INVALID_SUBSCRIPTION_ID;
  
      public MultinetworkPolicyTracker(Context ctx, Handler handler) {
          this(ctx, handler, null);
      }
  
      public MultinetworkPolicyTracker(Context ctx, Handler handler, Runnable avoidBadWifiCallback) {
          mContext = ctx;
          mHandler = handler;
          mReevaluateRunnable = () -> {
              if (updateAvoidBadWifi() && avoidBadWifiCallback != null) {
                  avoidBadWifiCallback.run();
              }
              updateMeteredMultipathPreference();
          };
          mSettingsUris = Arrays.asList(
              Settings.Global.getUriFor(NETWORK_AVOID_BAD_WIFI),
              Settings.Global.getUriFor(NETWORK_METERED_MULTIPATH_PREFERENCE));
          mResolver = mContext.getContentResolver();
          mSettingObserver = new SettingObserver();
          mBroadcastReceiver = new BroadcastReceiver() {
              @Override
              public void onReceive(Context context, Intent intent) {
                  reevaluate();
              }
          };
  
          TelephonyManager.from(ctx).listen(new PhoneStateListener() {
              @Override
              public void onActiveDataSubscriptionIdChanged(int subId) {
                  mActiveSubId = subId;
                  reevaluate();
              }
          }, PhoneStateListener.LISTEN_ACTIVE_DATA_SUBSCRIPTION_ID_CHANGE);
  
          updateAvoidBadWifi();
          updateMeteredMultipathPreference();
      }
  
      public void start() {
          for (Uri uri : mSettingsUris) {
              mResolver.registerContentObserver(uri, false, mSettingObserver);
          }
  
          final IntentFilter intentFilter = new IntentFilter();
          intentFilter.addAction(Intent.ACTION_CONFIGURATION_CHANGED);
          mContext.registerReceiverAsUser(
                  mBroadcastReceiver, UserHandle.ALL, intentFilter, null, null);
  
          reevaluate();
      }
  
      public void shutdown() {
          mResolver.unregisterContentObserver(mSettingObserver);
  
          mContext.unregisterReceiver(mBroadcastReceiver);
      }
  
      public boolean getAvoidBadWifi() {
          return mAvoidBadWifi;
      }
  
      // TODO: move this to MultipathPolicyTracker.
      public int getMeteredMultipathPreference() {
          return mMeteredMultipathPreference;
      }
  
      /**
       * Whether the device or carrier configuration disables avoiding bad wifi by default.
       */
      public boolean configRestrictsAvoidBadWifi() {
          return (getResourcesForActiveSubId().getInteger(R.integer.config_networkAvoidBadWifi) == 0);
      }
  
      @NonNull
      private Resources getResourcesForActiveSubId() {
          return SubscriptionManager.getResourcesForSubId(mContext, mActiveSubId);
      }
  
      /**
       * Whether we should display a notification when wifi becomes unvalidated.
       */
      public boolean shouldNotifyWifiUnvalidated() {
          return configRestrictsAvoidBadWifi() && getAvoidBadWifiSetting() == null;
      }
  
      public String getAvoidBadWifiSetting() {
          return Settings.Global.getString(mResolver, NETWORK_AVOID_BAD_WIFI);
      }
  
      @VisibleForTesting
      public void reevaluate() {
          mHandler.post(mReevaluateRunnable);
      }
  
      public boolean updateAvoidBadWifi() {
          final boolean settingAvoidBadWifi = "1".equals(getAvoidBadWifiSetting());
          final boolean prev = mAvoidBadWifi;
          mAvoidBadWifi = settingAvoidBadWifi || !configRestrictsAvoidBadWifi();
          return mAvoidBadWifi != prev;
      }
  
      /**
       * The default (device and carrier-dependent) value for metered multipath preference.
       */
      public int configMeteredMultipathPreference() {
          return mContext.getResources().getInteger(
                  R.integer.config_networkMeteredMultipathPreference);
      }
  
      public void updateMeteredMultipathPreference() {
          String setting = Settings.Global.getString(mResolver, NETWORK_METERED_MULTIPATH_PREFERENCE);
          try {
              mMeteredMultipathPreference = Integer.parseInt(setting);
          } catch (NumberFormatException e) {
              mMeteredMultipathPreference = configMeteredMultipathPreference();
          }
      }
  
      private class SettingObserver extends ContentObserver {
          public SettingObserver() {
              super(null);
          }
  
          @Override
          public void onChange(boolean selfChange) {
              Slog.wtf(TAG, "Should never be reached.");
          }
  
          @Override
          public void onChange(boolean selfChange, Uri uri) {
              if (!mSettingsUris.contains(uri)) {
                  Slog.wtf(TAG, "Unexpected settings observation: " + uri);
              }
              reevaluate();
          }
      }
  }
  