/**
  * @param $id
  * @return \Illuminate\Http\RedirectResponse
  */
 public function checkin($id)
 {
     $lastTransaction = Transaction::findLatest($id);
     if (!$lastTransaction->get()->isEmpty() && $lastTransaction->in_or_out == 'OUT') {
         $transaction = new Transaction();
         $transaction->in_or_out = 'IN';
         $transaction->transaction_id = $this->generateTransactionId($transaction->in_or_out);
         $transaction->due_date = NULL;
         $transaction->equipment_id = $id;
         $transaction->username = Auth::id();
         // temporary
         $transaction->person_id = $lastTransaction->person_id;
         // temporary
         $transaction->save();
         $this->generateReceiptEmail($transaction);
         return redirect()->route('inventory.index');
     } else {
         return redirect()->route('inventory.index');
     }
 }