nbxShift.kt

inline fun <I: Item> ItemContainer<I>.nbxShift(predicate: (I) -> Boolean = Item::isInvalidItem) {
    var firstSlotToFill = -1
    var currentSlot = 0
    var item: Item
    while (currentSlot < items.size) {
        item = this[currentSlot]
        if (predicate(item)) {
            if (firstSlotToFill < 0) firstSlotToFill = currentSlot
            currentSlot += 1
            continue
        }
        if (firstSlotToFill >= 0) {
            this[firstSlotToFill] = item.icopy()
            items[currentSlot] = InvalidItem
            currentSlot = firstSlotToFill + 1
            firstSlotToFill = -1
            continue
        }
        currentSlot += 1
    }
}