private SignupInfo validateAccountCreationForm()

in core/src/main/java/hudson/security/HudsonPrivateSecurityRealm.java [406:457]
40 lines of code
20 McCabe index (conditional complexity)

    private SignupInfo validateAccountCreationForm(StaplerRequest req, boolean validateCaptcha) {
        // form field validation
        // this pattern needs to be generalized and moved to stapler
        SignupInfo si = new SignupInfo(req);

        if (validateCaptcha && !validateCaptcha(si.captcha)) {
            si.errors.put("captcha", Messages.HudsonPrivateSecurityRealm_CreateAccount_TextNotMatchWordInImage());
        }

        if (si.username == null || si.username.length() == 0) {
            si.errors.put("username", Messages.HudsonPrivateSecurityRealm_CreateAccount_UserNameRequired());
        } else if(!containsOnlyAcceptableCharacters(si.username)) {
            if (ID_REGEX == null) {
                si.errors.put("username", Messages.HudsonPrivateSecurityRealm_CreateAccount_UserNameInvalidCharacters());
            } else {
                si.errors.put("username", Messages.HudsonPrivateSecurityRealm_CreateAccount_UserNameInvalidCharactersCustom(ID_REGEX));
            }
        } else {
            // do not create the user - we just want to check if the user already exists but is not a "login" user.
            User user = User.getById(si.username, false);
            if (null != user)
                // Allow sign up. SCM people has no such property.
                if (user.getProperty(Details.class) != null)
                    si.errors.put("username", Messages.HudsonPrivateSecurityRealm_CreateAccount_UserNameAlreadyTaken());
        }

        if (si.password1 != null && !si.password1.equals(si.password2)) {
            si.errors.put("password1", Messages.HudsonPrivateSecurityRealm_CreateAccount_PasswordNotMatch());
        }

        if (!(si.password1 != null && si.password1.length() != 0)) {
            si.errors.put("password1", Messages.HudsonPrivateSecurityRealm_CreateAccount_PasswordRequired());
        }

        if (si.fullname == null || si.fullname.length() == 0) {
            si.fullname = si.username;
        }

        if (isMailerPluginPresent() && (si.email == null || !si.email.contains("@"))) {
            si.errors.put("email", Messages.HudsonPrivateSecurityRealm_CreateAccount_InvalidEmailAddress());
        }

        if (!User.isIdOrFullnameAllowed(si.username)) {
            si.errors.put("username", hudson.model.Messages.User_IllegalUsername(si.username));
        }

        if (!User.isIdOrFullnameAllowed(si.fullname)) {
            si.errors.put("fullname", hudson.model.Messages.User_IllegalFullname(si.fullname));
        }
        req.setAttribute("data", si); // for error messages in the view
        return si;
    }