OO NineNine

NineNine.kt

package ninenine

interface NineNine {
    fun print99(formatter: String)
}

class Table(internal val width: Int, internal val height: Int, private val sections: Int = if (width >= 6) 2 else 1) : NineNine {
    private val lists = IntRange(1, width).map { Sheet(it, height) }.toList()

    override fun print99(formatter: String) {
        for (i in 0 until sections) {
            val start = i * width / sections
            val end = (i + 1) * width / sections
            BlockPrinter(start, end).printBlockly(formatter)
            println()
        }
    }

    private inner class BlockPrinter(private val start: Int, private val end: Int) {
        internal fun printBlockly(formatter: String) {
            val iterators = (start until end).map { lists[it].iterator() }
            repeat(height) {
                iterators.map {
                    it.next().print99(formatter)
                    print(if (it == iterators.last()) "\n" else "  ")
                }
            }
        }
    }
}

class Sheet(internal val x: Int, internal val height: Int): NineNine, Iterable<Item> {
    private val items = IntRange(1, height).map { Item(x, it) }.toList()

    override fun print99(formatter: String) = items.forEach {
        it.print99(formatter)
        print(if (it == items.last()) "" else "\n")
    }

    override fun iterator(): Iterator<Item> = items.iterator()
}

class Item(internal val x: Int, internal val y: Int) : NineNine {
    override fun print99(formatter: String) = print(formatter.format(x , y, x * y))
}

private inline fun <reified C : NineNine> C.print99() {
    val formatter = when (this) {
        is Table -> formatterHelper(width, height)
        is Sheet -> formatterHelper(x, height)
        is Item -> formatterHelper(x, y)
        else -> TODO("This function doesn't support ${C::class} yet")
    }
    print99(formatter)
}

private fun formatterHelper(x: Int, y: Int) = "%${x.digit}d x %${y.digit}d = %${(x * y).digit}d"

private val Int.digit: Int
    get() = toString().length

fun main(args: Array<String>) {
    var nineNine: NineNine

    nineNine = Table(10, 10, 2)
    nineNine.print99() // (1 ~ 5), (6 ~ 10)

    nineNine = Table(12, 10, 3)
    nineNine.print99() // (1 ~ 4) + (5 ~ 8) + (9 ~ 12)

    nineNine = Sheet(3, 12)
    nineNine.print99() // 3 x 1 = 3 ... 3 x 12 = 36

    println()
    println()

    // Customized formatter:
    nineNine = Item(7, 2)
    nineNine.print99("%d * %d -> %2d") // 7 * 2 -> 14
}