upc.kt

// https://www.codewars.com/kata/568e111353952f6c82000014

fun main(args: Array<String>) {
//    print(Character.getNumericValue('5'))
    print(UPC("614141000030"))
}

fun UPC(s : String) : Boolean {

    //calculate the odd sum
    //calculate the even sum
    //multiply odd sum by 3 to ge weighted odd sum
    //add even sum + wieighted odd sum = weighted sum
    //take rem = wightedsum % 10
    //if rem == 0, then 0 is our check digit
    // else 10 - rem = check digit

    //verigy check digit
    //if it's the same as that in the UPC and 12 digits then it's valid

    if (s.length != 12) {
        return false
    }
    else {

        val initialCheckDigit = s.last()

        val oddSum = oddSum(s)
        val evenSum = evenSum(s)

        val weightedOddSum = weightedOddSum(oddSum)

        val weightedSum = weightedOddSum + evenSum
        val mod = weightedSum % 10

        val checkDigit = getCheckDigit(mod)

        return checkDigit.toString() == initialCheckDigit.toString()

    }


}

fun getCheckDigit(mod : Int) : Int {
    return if (mod == 0) {
        0
    }
    else {
        10 - mod
    }
}


fun weightedOddSum(oddSum : Int) : Int {
    return oddSum * 3
}

fun oddSum(s: String) : Int {
    //614141000036
    val sAsList = s.toCharArray().map { Character.getNumericValue(it) }
    var sum = 0
    for (i in 0..11 step 2) {
        sum += sAsList[i]
    }

    return sum
}

fun evenSum(s : String) : Int {
    val trimmed = s.substring(0, s.length - 1)

    val sAsList = trimmed.toCharArray().map { Character.getNumericValue(it) }
    var sum = 0

    for (i in 1..10 step 2) {
        sum += sAsList[i]
    }

    return sum
}