/*
 * 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 com.android.contacts.common.location;

import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationManager;
import android.preference.PreferenceManager;
import android.telephony.TelephonyManager;
import android.text.TextUtils;
import android.util.Log;
import com.android.dialer.util.PermissionsUtil;
import java.util.Locale;

/**
 * This class is used to detect the country where the user is. It is a simplified version of the
 * country detector service in the framework. The sources of country location are queried in the
 * following order of reliability:
 *
 * <ul>
 * <li>Mobile network
 * <li>Location manager
 * <li>SIM's country
 * <li>User's default locale
 * </ul>
 *
 * As far as possible this class tries to replicate the behavior of the system's country detector
 * service: 1) Order in priority of sources of country location 2) Mobile network information
 * provided by CDMA phones is ignored 3) Location information is updated every 12 hours (instead of
 * 24 hours in the system) 4) Location updates only uses the {@link
 * LocationManager#PASSIVE_PROVIDER} to avoid active use of the GPS 5) If a location is successfully
 * obtained and geocoded, we never fall back to use of the SIM's country (for the system, the
 * fallback never happens without a reboot) 6) Location is not used if the device does not implement
 * a {@link android.location.Geocoder}
 */
public class CountryDetector {

  public static final String KEY_PREFERENCE_TIME_UPDATED = "preference_time_updated";
  public static final String KEY_PREFERENCE_CURRENT_COUNTRY = "preference_current_country";
  private static final String TAG = "CountryDetector";
  // Wait 12 hours between updates
  private static final long TIME_BETWEEN_UPDATES_MS = 1000L * 60 * 60 * 12;
  // Minimum distance before an update is triggered, in meters. We don't need this to be too
  // exact because all we care about is what country the user is in.
  private static final long DISTANCE_BETWEEN_UPDATES_METERS = 5000;
  private static CountryDetector sInstance;
  private final TelephonyManager mTelephonyManager;
  private final LocationManager mLocationManager;
  private final LocaleProvider mLocaleProvider;
  // Used as a default country code when all the sources of country data have failed in the
  // exceedingly rare event that the device does not have a default locale set for some reason.
  private static final String DEFAULT_COUNTRY_ISO = "US";
  private final Context mContext;

  private CountryDetector(Context context) {
    this(
        context,
        (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE),
        (LocationManager) context.getSystemService(Context.LOCATION_SERVICE),
        new LocaleProvider());
  }

  private CountryDetector(
      Context context,
      TelephonyManager telephonyManager,
      LocationManager locationManager,
      LocaleProvider localeProvider) {
    mTelephonyManager = telephonyManager;
    mLocationManager = locationManager;
    mLocaleProvider = localeProvider;
    mContext = context;

    registerForLocationUpdates(context, mLocationManager);
  }

  public static void registerForLocationUpdates(Context context, LocationManager locationManager) {
    if (!PermissionsUtil.hasLocationPermissions(context)) {
      Log.w(TAG, "No location permissions, not registering for location updates.");
      return;
    }

    if (!Geocoder.isPresent()) {
      // Certain devices do not have an implementation of a geocoder - in that case there is
      // no point trying to get location updates because we cannot retrieve the country based
      // on the location anyway.
      return;
    }
    final Intent activeIntent = new Intent(context, LocationChangedReceiver.class);
    final PendingIntent pendingIntent =
        PendingIntent.getBroadcast(context, 0, activeIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    locationManager.requestLocationUpdates(
        LocationManager.PASSIVE_PROVIDER,
        TIME_BETWEEN_UPDATES_MS,
        DISTANCE_BETWEEN_UPDATES_METERS,
        pendingIntent);
  }

  /**
   * Returns the instance of the country detector. {@link #initialize(Context)} must have been
   * called previously.
   *
   * @return the initialized country detector.
   */
  public static synchronized CountryDetector getInstance(Context context) {
    if (sInstance == null) {
      sInstance = new CountryDetector(context.getApplicationContext());
    }
    return sInstance;
  }

  /** Factory method for {@link CountryDetector} that allows the caller to provide mock objects. */
  public CountryDetector getInstanceForTest(
      Context context,
      TelephonyManager telephonyManager,
      LocationManager locationManager,
      LocaleProvider localeProvider,
      Geocoder geocoder) {
    return new CountryDetector(context, telephonyManager, locationManager, localeProvider);
  }

  public String getCurrentCountryIso() {
    String result = null;
    if (isNetworkCountryCodeAvailable()) {
      result = getNetworkBasedCountryIso();
    }
    if (TextUtils.isEmpty(result)) {
      result = getLocationBasedCountryIso();
    }
    if (TextUtils.isEmpty(result)) {
      result = getSimBasedCountryIso();
    }
    if (TextUtils.isEmpty(result)) {
      result = getLocaleBasedCountryIso();
    }
    if (TextUtils.isEmpty(result)) {
      result = DEFAULT_COUNTRY_ISO;
    }
    return result.toUpperCase(Locale.US);
  }

  /** @return the country code of the current telephony network the user is connected to. */
  private String getNetworkBasedCountryIso() {
    return mTelephonyManager.getNetworkCountryIso();
  }

  /** @return the geocoded country code detected by the {@link LocationManager}. */
  private String getLocationBasedCountryIso() {
    if (!Geocoder.isPresent() || !PermissionsUtil.hasLocationPermissions(mContext)) {
      return null;
    }
    final SharedPreferences sharedPreferences =
        PreferenceManager.getDefaultSharedPreferences(mContext);
    return sharedPreferences.getString(KEY_PREFERENCE_CURRENT_COUNTRY, null);
  }

  /** @return the country code of the SIM card currently inserted in the device. */
  private String getSimBasedCountryIso() {
    return mTelephonyManager.getSimCountryIso();
  }

  /** @return the country code of the user's currently selected locale. */
  private String getLocaleBasedCountryIso() {
    Locale defaultLocale = mLocaleProvider.getDefaultLocale();
    if (defaultLocale != null) {
      return defaultLocale.getCountry();
    }
    return null;
  }

  private boolean isNetworkCountryCodeAvailable() {
    // On CDMA TelephonyManager.getNetworkCountryIso() just returns the SIM's country code.
    // In this case, we want to ignore the value returned and fallback to location instead.
    return mTelephonyManager.getPhoneType() == TelephonyManager.PHONE_TYPE_GSM;
  }

  /**
   * Class that can be used to return the user's default locale. This is in its own class so that it
   * can be mocked out.
   */
  public static class LocaleProvider {

    public Locale getDefaultLocale() {
      return Locale.getDefault();
    }
  }

  public static class LocationChangedReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, Intent intent) {
      if (!intent.hasExtra(LocationManager.KEY_LOCATION_CHANGED)) {
        return;
      }

      final Location location =
          (Location) intent.getExtras().get(LocationManager.KEY_LOCATION_CHANGED);

      UpdateCountryService.updateCountry(context, location);
    }
  }
}