StupidIterator.kt

class StupidIterator(val source: Iterator<*>): Iterator<String> {
    private var nextElement: Any? = null

    init {
        acquireNextElement()
    }

    private fun acquireNextElement() {
        nextElement = if (source.hasNext()) source.next().let { if (it is Iterator<*>) StupidIterator(it) else it } else null
    }
    
    override fun hasNext(): Boolean {
        if (nextElement != null) {
            if (nextElement is Iterator<*>) {
                if ((nextElement as Iterator<*>).hasNext()) {
                    return true
                }
                acquireNextElement()
                return hasNext()
            }
            return true
        }
        return false
    }

    override fun next(): String {
        if (nextElement is Iterator<*>) {
            val iterator = nextElement as Iterator<*>
            return iterator.next().also { if (!iterator.hasNext()) acquireNextElement() } as String
        }
        return nextElement.also { acquireNextElement() } as String
    }

}