ProductAdapter.kt

class ProductAdapter(
    private val products: ArrayList<ViewProduct>
) : RecyclerView.Adapter<ProductViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ProductViewHolder {
        return ProductViewHolder(
            LayoutInflater.from(parent.context).inflate(R.layout.product_item, parent, false)
        )
    }

    override fun getItemCount(): Int = products.size

    override fun onBindViewHolder(holder: ProductViewHolder, position: Int) {
        holder.bind(products[position])
    }

    override fun onBindViewHolder(
        holder: ProductViewHolder,
        position: Int,
        payloads: MutableList<Any>
    ) {
        if (payloads.isEmpty()) {
            onBindViewHolder(holder, position)
        } else {
            for (data in payloads) {
                when (data as Int) {
                    INVALID_PRODUCT_POSITION -> holder.updateProductQuantity(products[position].quantityInCart)
                }
            }
        }
    }

    fun updateProducts(products: List<ViewProduct>) {
        val result = DiffUtil.calculateDiff(ProductDiffUtilCallback(this.products, products))
        result.dispatchUpdatesTo(this)
        this.products.clear()
        this.products.addAll(products)
    }
    
    fun removeProduct(product: ViewProduct) {
        val index = products.indexOf(product)

        if (index == INVALID_PRODUCT_POSITION) {
            return
        }

        products.removeAt(index)
        notifyItemRemoved(index)
    }

    companion object {
        private const val INVALID_PRODUCT_POSITION = 1
    }
}