Base adapter that holds all delegates and differFactory for producing diffs

DelegatesAdapter.kt

open class DelegatesAdapter<I : Any>(
        private val differFactory: (RecyclerView.Adapter<*>) -> ListDiffer<I>,
        vararg delegates: ItemDelegate<out I, *>
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    private val delegatesIndexMap: Map<Class<*>, Int>
    private val delegatesList: List<ItemDelegate<I, RecyclerView.ViewHolder>>
    private val listDiffer: ListDiffer<I> by lazy { differFactory(this) }

    val items: List<I> get() = listDiffer.currentList

    constructor(vararg delegates: ItemDelegate<out I, *>): this({ SyncListDiffer(it) }, *delegates)

    init {
        val map = mutableMapOf<Class<*>, Int>()
        delegates.forEachIndexed { index, delegate ->
            if (map.put(delegate.itemType(), index) != null) {
                throw IllegalArgumentException()
            }
        }

        delegatesIndexMap = map
        delegatesList = delegates.map {
            @Suppress("UNCHECKED_CAST")
            it as? ItemDelegate<I, RecyclerView.ViewHolder>
                    ?: throw IllegalArgumentException()
        }
    }

    override fun getItemViewType(position: Int): Int = delegatesIndexMap[items[position]::class.java]
            ?: throw IllegalStateException("There is no delegate for item with type: ${items[position]::class.java}")

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = delegatesList[viewType].createVewHolder(parent)

    override fun getItemCount() = items.size

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        delegatesList[getItemViewType(position)].bindView(position, items[position], holder)
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int, payloads: MutableList<Any>) {
        if (payloads.isEmpty()) {
            super.onBindViewHolder(holder, position, payloads)
        } else {
            delegatesList[getItemViewType(position)].bindView(position, items[position], holder, payloads)
        }
    }

    fun updateItem(old: I, new: I) {
        val newList = items.toMutableList()
        if (newList.updateFirst(new, { it == old })) {
            submitList(newList)
        }
    }

    fun submitList(list: List<I>) = listDiffer.submitList(list)
}