// == Process of Abstraction ==
// 1. Write something twice -> :: spidey sense!! ::
// 2. Compare, differences -> parameters
// 3. Create abstraction
// 4. Re-write #1 as special cases

























fun sortNumsByOp(nums: List<Int>, compareNumberOp: (Int, Int)->Boolean): List<Int> {
    fun insert(sortedList: List<Int>, num: Int): List<Int> {
        return when (sortedList.isEmpty()) {
            true -> listOf(num)
            false -> when (compareNumberOp(num, sortedList[0])) {
                true -> listOf(num) + sortedList
                false -> sortedList.take(1) + insert(sortedList.drop(1), num)
            }
        }
    }
    
    return nums.fold(emptyList<Int>(), ::insert)
}

fun sortIncreasing(nums: List<Int>): List<Int> {
    return sortNumsByOp(nums, ::lteNums)
}

fun sortDecreasing(nums: List<Int>): List<Int> {
    return sortNumsByOp(nums, ::gteNums)
}


// fun sortIncreasing(nums: List<Int>): List<Int> {
//     fun insert(sortedList: List<Int>, num: Int): List<Int> {
//         return when (sortedList.isEmpty()) {
//             true -> listOf(num)
//             false -> when (lteNums(num, sortedList[0])) {
//                 true -> listOf(num) + sortedList
//                 false -> sortedList.take(1) + insert(sortedList.drop(1), num)
//             }
//         }
//     }
    
//     return nums.fold(emptyList<Int>(), ::insert)
// }

// fun sortDecreasing(nums: List<Int>): List<Int> {
//     fun insert(sortedList: List<Int>, num: Int): List<Int> {
//         return when (sortedList.isEmpty()) {
//             true -> listOf(num)
//             false -> when (gteNums(num, sortedList[0])) {
//                 true -> listOf(num) + sortedList
//                 false -> sortedList.take(1) + insert(sortedList.drop(1), num)
//             }
//         }
//     }
    
//     return nums.fold(emptyList<Int>(), ::insert)
// }

// is the first less than or equal to the second?
fun lteNums(num1: Int, num2: Int): Boolean {
    return num1 <= num2
}

// is the first greater than or equal to the second?
fun gteNums(num1: Int, num2: Int): Boolean {
    return num1 >= num2
}

val exNums = listOf(9, 2, 5)

println(sortIncreasing(exNums))
println(sortDecreasing(exNums))