ListenableFuturePagingSource

import androidx.paging.ListenableFuturePagingSource
import androidx.paging.PagingState

class MyListenableFuturePagingSource(
    val myBackend: GuavaBackendService,
    val searchTerm: String
) : ListenableFuturePagingSource<String, Item>() {
    override fun loadFuture(
        params: LoadParams<String>
    ): ListenableFuture<LoadResult<String, Item>> {
        return myBackend
            .searchUsers(
                searchTerm = searchTerm,
                pageKey = params.key
            )
            .transform<LoadResult<String, Item>>(
                { response ->
                    LoadResult.Page(
                        data = response!!.items,
                        prevKey = response.prev,
                        nextKey = response.next
                    )
                },
                networkExecutor
            )
            // Retrofit calls that return the body type throw either IOException for
            // network failures, or HttpException for any non-2xx HTTP status codes.
            // This code reports all errors to the UI, but you can inspect/wrap the
            // exceptions to provide more context.
            .catching(
                IOException::class.java,
                { t: IOException? -> LoadResult.Error(t!!) },
                networkExecutor
            )
            .catching(
                HttpException::class.java,
                { t: HttpException? -> LoadResult.Error(t!!) },
                networkExecutor
            )
    }

    override fun getRefreshKey(state: PagingState<String, Item>): String? {
        return state.anchorPosition?.let { state.closestItemToPosition(it)?.id }
    }
}