GitHub authentication validation (login, authToken)

Validator.kt

object Validator {
    private const val LOGIN_PATTERN = "^[a-zA-Z0-9_-]{0,38}$"
    private const val AUTHORIZATION_TOKEN_PATTERN = "^gh[pousr]_[a-zA-Z0-9]{0,40}$"

    fun validateLogin(login: String): Validation {
        if (login.isEmpty()) return FieldValidation.Empty

        val matcher = Pattern.compile(LOGIN_PATTERN).matcher(login)
        return if (matcher.matches()) Validation.Correct else Validation.Incorrect
    }

    fun validateAuthorisationToken(authToken: String): Validation {
        if (authToken.isEmpty()) return FieldValidation.Empty

        val matcher = Pattern.compile(AUTHORIZATION_TOKEN_PATTERN).matcher(authToken)

        return if (matcher.matches()) Validation.Correct else Validation.Incorrect
    }
}

sealed interface Validation {
    object Correct : Validation
    object Incorrect : Validation
    object Empty : Validation
}