package com.react.bridge.firebase;

import android.content.Context;
import android.content.SharedPreferences;
import android.provider.Settings.Secure;
import android.telephony.TelephonyManager;
import android.util.Log;

import com.google.firebase.iid.FirebaseInstanceId;

import java.io.UnsupportedEncodingException;
import java.util.UUID;

public class RNBridgeFirebaseDeviceUid {
  protected static final String PREFS_FILE      = "device_id.xml";
  protected static final String PREFS_DEVICE_ID = "device_id";

  protected static UUID uuid;

  public RNBridgeFirebaseDeviceUid(Context context) {
    if (uuid != null) return;

    try {
      final SharedPreferences prefs = context.getSharedPreferences(PREFS_FILE, 0);

      do {
        final String id = prefs.getString(PREFS_DEVICE_ID, null);

        if (id != null) {
          uuid = UUID.fromString(id);
          break;
        }

        final String androidId = Secure.getString(context.getContentResolver(), Secure.ANDROID_ID);

        if (androidId != null && (!"9774d56d682e549c".equals(androidId))) {
          uuid = UUID.nameUUIDFromBytes(androidId.getBytes("utf8"));
          break;
        }

        final String iid = FirebaseInstanceId.getInstance().getId();

        if (iid != null) {
          uuid = UUID.nameUUIDFromBytes(iid.getBytes("utf8"));
          break;
        }

        final String deviceId = ((TelephonyManager) context.getApplicationContext().getSystemService(Context.TELEPHONY_SERVICE)).getDeviceId();
        if(deviceId != null) {
          uuid = UUID.nameUUIDFromBytes(deviceId.getBytes("utf8"));
          break;
        }

        uuid = UUID.randomUUID();
      } while (false);

      if (uuid != null) prefs.edit().putString(PREFS_DEVICE_ID, uuid.toString()).commit();
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Returns a unique UUID for the current android device. As with all UUIDs,
   * this unique ID is "very highly likely" to be unique across all Android
   * devices. Much more so than ANDROID_ID is.
   *
   * The UUID is generated by using ANDROID_ID as the base key if appropriate,
   * falling back on TelephonyManager.getDeviceID() if ANDROID_ID is known to be
   * incorrect, and finally falling back on a random UUID that's persisted to
   * SharedPreferences if getDeviceID() does not return a usable value.
   *
   * In some rare circumstances, this ID may change. In particular, if the
   * device is factory reset a new device ID may be generated. In addition, if a
   * user upgrades their phone from certain buggy implementations of Android 2.2
   * to a newer, non-buggy version of Android, the device ID may change. Or, if
   * a user uninstalls your app on a device that has neither a proper Android ID
   * nor a Device ID, this ID may change on reinstallation.
   *
   * Note that if the code falls back on using TelephonyManager.getDeviceId(),
   * the resulting ID will NOT change after a factory reset. Something to be
   * aware of.
   *
   * Works around a bug in Android 2.2 for many devices when using ANDROID_ID
   * directly.
   *
   * @see http://code.google.com/p/android/issues/detail?id=10603
   *
   * @return a UUID that may be used to uniquely identify your device for most
   *         purposes.
   */
  public UUID getDeviceUid() {
    return uuid;
  }
}