phon number cursor 1488 bug

private void setTexts() {
        Locale locale = getLocale();
        singInLabel.setValue(messageSource.getMessage("login.singInLabel", null, locale));
        loginTextField.setCaption(messageSource.getMessage("login.login", null, locale));
        loginTextField.setValue("Ext-N.Ovcharenko");
        passwordTextField.setCaption(messageSource.getMessage("login.password", null, locale));
        forgotLink.setCaption(messageSource.getMessage("login.forgot", null, locale));
        singInButton.setCaption(messageSource.getMessage("login.singIn", null, locale));


        TextField phoneNumberField = new TextField("phone number");
        String patternPhoneExtended = "^\\+7 \\d{3} \\d{3}-\\d{2}-\\d{2}$";
        Pattern patternPhoneSimple = Pattern.compile("^(8|\\+?7)\\d{10}$");
        phoneNumberField.addValidator(new RegexpValidator(patternPhoneExtended, messageSource.getMessage("fieldPhoneFormat", null, locale)));
        phoneNumberField.addTextChangeListener(textChangeEvent -> {
            String eventString = textChangeEvent.getText();
            String val = phoneNumberField.getValue();
            System.out.println("txt val/event: " + val + " / " + eventString);

            phoneNumberField.setValue(eventString.replaceAll("[\\+ ()-]", ""));

            int delta = countCursorOffset(eventString, phoneNumberField.getCursorPosition());

            System.out.print("cursor: " + phoneNumberField.getCursorPosition() + " -> ");
            System.out.print("(" + (delta > 0 ? "+" : "") + delta + ") -> ");
            phoneNumberField.setCursorPosition(phoneNumberField.getCursorPosition() + delta);
            System.out.println(phoneNumberField.getCursorPosition());
        });
        phoneNumberField.addValueChangeListener(valueChangeEvent -> {
            String val = phoneNumberField.getValue();
            Matcher m = patternPhoneSimple.matcher(val);
            if (m.matches()) {
                phoneNumberField.setValue(formatPhone(val));
            }
        });
        addComponent(phoneNumberField);
    }

    private int countCursorOffset(String number, int currPos) {
        final int PHONE_NUMBER_LEN = 10;
        List<Character> specChars = new ArrayList<>(Arrays.asList('+', '-', ' ', '(', ')'));

        if (number.contains(" ")) {
            String formattedPrefix = number.substring(0, currPos);
            String originalPrefix = formattedPrefix.replaceAll("[\\+ ()-]", "");

            return originalPrefix.length() - formattedPrefix.length();

        } else {
            //we cannot count formatted prefix since we do not have full valid 10-digit number yet
            // so let's extend number to its full len and count prefix len as
            StringBuilder sb = new StringBuilder(number);
            while (sb.length() < PHONE_NUMBER_LEN)
                sb.append("9");

            String formatted = formatPhone(sb.toString());

            int i = 0, j = 0, formattedPrefixLen = 0;
            while (i < currPos) {
                if (!specChars.contains(formatted.charAt(i))) {
                    if (formatted.charAt(i) == number.charAt(j)) {
                        formattedPrefixLen++;
                        j++;
                    }
                }
                i++;
            }
            String originalPrefix = number.substring(0, currPos);

            return formattedPrefixLen - originalPrefix.length();
        }
    }

    private String formatPhone(String val) {
        PhoneNumberUtil phoneNumberUtil = PhoneNumberUtil.getInstance();
        try {
            Phonenumber.PhoneNumber p = phoneNumberUtil.parse(val, "RU");
            return phoneNumberUtil.format(p, PhoneNumberUtil.PhoneNumberFormat.INTERNATIONAL);
        } catch (NumberParseException e) {
            LOG.error(ExceptionUtils.getStackTrace(e));
            return val;
        }
    }