kotlin view adding deleting updating books program

private fun updateBook() {
        println("Pick a book by its number to update:")
        viewBooks(false)
        println("\nSelection: ")
        val bookSelection = try {
            books[readLine()!!.toInt() - 1]
        } catch (e: Exception) {
            println("Invalid selection! Aborting..")
            return
        }
        println("\nSelected:\n$bookSelection.\n\nChoose a variable to update:")
        printBookVariables()
        println("\nSelection: ")
        val enumSelection = try {
            readLine()!!.toInt()
        } catch (e: Exception) {
            println("Invalid selection! Aborting..")
            return
        }

        val selected = BookVariables.values().associateBy(BookVariables::id)[enumSelection]
        println("\nSelected modifier:\n$selected\n\nType a new ${selected.toString().toLowerCase()}:")
        try {
            val newValue = readLine()!!
            if (newValue.isBlank()) {
                println("Modification can't be empty! Aborting..")
                return
            }
            when (enumSelection) {
                BookVariables.TITLE.id -> bookSelection.title = newValue
                BookVariables.AUTHOR.id -> bookSelection.author = newValue
                BookVariables.PUBLICATION_YEAR.id -> {
                    if (newValue.toInt() <= 1600) {
                        println("Publication year is too old! Aborting..")
                        return
                    }
                    bookSelection.publicationYear = newValue.toInt()
                }
                BookVariables.NUMBER_OF_PAGES.id -> {
                    if (newValue.toInt() <= 0) {
                        println("There must be at least one page! Aborting..")
                        return
                    }
                    bookSelection.numberOfPages = newValue.toInt()
                }
                BookVariables.ISBN_NUMBER.id -> bookSelection.isbn = newValue.toLong()
            }
        } catch (e: NumberFormatException) {
            println("Invalid selection! Aborting..")
            return
        }
        println("\nUpdated book info:\n$bookSelection")
    }

    private fun deleteBook() {
        println("Pick a book by its number to delete:")
        viewBooks(false)
        println("\nSelection: ")
        val bookSelection = try {
            books[readLine()!!.toInt() - 1]
        } catch (e: Exception) {
            println("Invalid selection! Aborting..")
            return
        }
        books.remove(bookSelection)
        println("Book deleted!")
    }

    private fun viewBookWithMostPages() {
        val find = books.maxByOrNull { it.numberOfPages }
        if (find == null) {
            println("No books found! Aborting..")
            return
        }
        println("Book with most pages:\n${find.title} (Pages: ${find.numberOfPages})")
    }

    private fun viewBookWithLeastPages() {
        val find = books.minByOrNull { it.numberOfPages }
        if (find == null) {
            println("No books found! Aborting..")
            return
        }
        println("Book with least pages:\n${find.title} (Pages: ${find.numberOfPages})")
    }

    private fun viewBooksPagesAboveOrEqual(number: Int) {
        println("Books with pages above or equal to $number:")
        val find = books.filter { it.numberOfPages >= number }
        viewBooks(false, find)
    }

    private fun viewBooksPagesBelow(number: Int) {
        println("Books with pages below $number:")
        val find = books.filter { it.numberOfPages < number }
        viewBooks(false, find)
    }

    private fun viewBooksPagesBetweenInclusive(min: Int, max: Int) {
        println("Books with pages between $min and $max:")
        val find = books.filter { it.numberOfPages in min..max }
        viewBooks(false, find)
    }

//    fun viewBooksWithPagesInRange(books: MutableList<Book>, range: IntRange = 0..Int.MAX_VALUE) {
//        val tempBooksList = mutableListOf<Book>()
//        println("Books with pages between ${range.first} and ${range.last}: ")
//        for (book in books) {
//            if(book.numberOfPages in range) {
//                tempBooksList.add(book)
//            }
//        }
//        printBooks(tempBooksList, false)
//    }
}

class Book(
    var title: String,
    var author: String,
    var publicationYear: Int,
    var numberOfPages: Int,
    var isbn: Long
) {
    override fun toString(): String {
        return "$title, $author, $publicationYear, $numberOfPages, https://biblio.com/$isbn"
    }

    fun toTab(): String {
        return "$title\t$author\t$publicationYear\t$numberOfPages\t$isbn"
    }
}