/**
  * Display a listing of the resource.
  *
  * @return Response
  */
 public function index(Request $request)
 {
     $storage_path = storage_path();
     $sms_request = $request->all();
     $phone_number = $sms_request['sender'];
     $description = json_encode($sms_request);
     $student = StudentQuery::retrieveByPhoneNumber($phone_number);
     if (is_null($student)) {
         $msg_text = 'Niste registrovani. Kontaktirajte administratora PMF-a.';
         //$this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     if ($sms_request['sms_prefix'] !== 'PRIJAVA_ISPITA') {
         $msg_text = "Nepostojeca komanda! Za prijavu ispita poslati: ‘PRIJAVA_ISPITA <šifra_predmeta> <ispitni_rok>'";
         $this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     $fullsms = explode(" ", $sms_request['fullsms']);
     $subject_code = isset($fullsms[1]) ? $fullsms[1] : null;
     $period_name = isset($fullsms[2]) ? $fullsms[2] : null;
     if (!isset($subject_code) && !isset($period_name)) {
         $msg_text = 'Doslo je do greske, proverite unete podatke.';
         $this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     $subject = SubjectQuery::retrieveByCode($subject_code);
     if (is_null($subject)) {
         $msg_text = 'Nepostojeca šifra predmeta.';
         $this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     $period = $this->getPeriodIdByName($period_name);
     if (is_null($period)) {
         $msg_text = 'Ispitni rok ne postoji';
         $this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     $school_year_id = $this->getSchoolYearIdByDate();
     $periodSchoolYear = PeriodSchoolYearQuery::create()->findPk([$period->getId(), $school_year_id]);
     if (is_null($periodSchoolYear)) {
         $msg_text = 'Ispitni rok ne postoji';
         $this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     $studyProgram = StudyProgramQuery::create()->findPk([$subject->getId(), $student->getCourseId()]);
     if (is_null($studyProgram)) {
         $msg_text = 'Ovaj predmet nije u vašem studijskom programu.';
         $this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     $msg_text = $this->allowedToApply($student->getId(), $subject, $period->getId(), $school_year_id);
     if ($msg_text !== null) {
         $this->sendSms($phone_number, $msg_text, $description);
         exit;
     }
     $application = new Application();
     $application->setStudentId($student->getId());
     $application->setSubjectId($subject->getId());
     $application->setPeriodId(8);
     $application->setSchoolYearId(8);
     $application->setApplicationDate(date('Y-m-d'));
     $application->save();
     $msg_text = 'Uspesno ste prijavili ispit.';
     $this->sendSms($phone_number, $msg_text, $description, $application->getId());
     exit;
 }