The ability to choose between async and sync diff calculations

differs.kt

interface ListDiffer<T> {
    val currentList: List<T>

    fun submitList(list: List<T>)
}

class SyncListDiffer<T : Any>(
        private val adapter: RecyclerView.Adapter<*>,
        private val callbackFactory: DiffCallbackFactory<T> = { old, new -> SimpleDiffCallback(old, new) }
) : ListDiffer<T> {
    override var currentList: List<T> = emptyList()
        private set

    override fun submitList(list: List<T>) {
        val diffResult = DiffUtil.calculateDiff(callbackFactory(currentList, list))
        currentList = list
        diffResult.dispatchUpdatesTo(adapter)
    }
}

class AsyncListDifferAdapter<T>(private val origin: AsyncListDiffer<T>) : ListDiffer<T> {

    override val currentList: List<T> get() = origin.currentList

    override fun submitList(list: List<T>) = origin.submitList(list)
}