InputFilter to enter years from 1900 onwards

YearInputFilter.kt

val yearInputFilter: InputFilter = object : InputFilter {
        override fun filter(source: CharSequence?, start: Int, end: Int, dest: Spanned?, dStart: Int, dEnd: Int): CharSequence {
            if (source.isNullOrEmpty()) { //Delete. Do nothing.
                return source ?: ""
            } else {

                val p1 = dest?.toString()?.take(dStart) ?: ""
                val p2 = dest?.takeLast(dest.toString().length - dEnd)
                val endString = p1 + source + p2

                if (endString == "1" || endString == "2" ||
                        endString.startsWith("19") ||
                        endString.startsWith("20")) {
                    return source
                } else {
                    return ""
                }
            }
        }
    }