package apackage;

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

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

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

  protected static UUID         uuid;

  public DeviceUuidFactory(Context context)
  {

    if (uuid == null)
    {
      synchronized (DeviceUuidFactory.class)
      {
        if (uuid == null)
        {
          final SharedPreferences prefs = context.getSharedPreferences(PREFS_FILE, 0);
          final String id = prefs.getString(PREFS_DEVICE_ID, null);

          if (id != null)
          {
            // Use the ids previously computed and stored in the prefs file
            uuid = UUID.fromString(id);

          } else
          {

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

            // Use the Android ID unless it's broken, in which case fallback on
            // deviceId,
            // unless it's not available, then fallback on a random number which
            // we store
            // to a prefs file
            try
            {
              if (androidId != null && (!"9774d56d682e549c".equals(androidId)))
              {
                uuid = UUID.nameUUIDFromBytes(androidId.getBytes("utf8"));
              } else
              {
                final String deviceId = ((TelephonyManager) context.getApplicationContext().getSystemService(Context.TELEPHONY_SERVICE)).getDeviceId();
                if(deviceId == null)
                {
                  uuid = UUID.randomUUID();
                  prefs.edit().putString(PREFS_DEVICE_ID, uuid.toString()).commit();
                  
                }else{
                  uuid = deviceId != null ? UUID.nameUUIDFromBytes(deviceId.getBytes("utf8")) : UUID.randomUUID();
                  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 getDeviceUuid()
  {
    return uuid;
  }
}