Paging3_JetpackAndroid

// PagingSource

private const val MOVIES_STARTING_PAGE_INDEX = 1

class MoviesPagingSource(
    private val apiHelper: ApiHelper
) : RxPagingSource<Int, ResultsItem>() {
    override fun loadSingle(params: LoadParams<Int>): Single<LoadResult<Int, ResultsItem>> {
        val position = params.key ?: MOVIES_STARTING_PAGE_INDEX
        Log.d("POSITION", position.toString())
        return try {
            apiHelper
                .getPopularMovies(position)
                ?.map {
                    LoadResult.Page(
                        it,
                        if (position == MOVIES_STARTING_PAGE_INDEX) null else position,
                        if (it.isEmpty()) null else position + 1
                    )
                }
                ?.compose(singleIo())
                ?.doOnError {
                    it.printStackTrace()
                    LoadResult.Error<Int, ResultsItem>(it)
                } as Single<LoadResult<Int, ResultsItem>>
        } catch (e: Exception) {
            e.printStackTrace()
            Single.just(LoadResult.Error(e))
        }
    }
}

// ViewModel

class PagingViewModel @Inject constructor(private val appDataManager: AppDataManager) :
    BaseObservableViewModel() {
    companion object {
        private const val NETWORK_PAGE_SIZE = 20
    }

    private var currentMovieResult: Flowable<PagingData<ResultsItem>> = Pager(
        config = PagingConfig(
            pageSize = NETWORK_PAGE_SIZE,
            enablePlaceholders = false
        ), pagingSourceFactory = { MoviesPagingSource(appDataManager) }
    ).flowable.cachedIn(viewModelScope)

    val mutableLiveDataItems = MutableLiveData<PagingData<ResultsItem>>()

    fun getMovies() {
        compositeDisposable.add(currentMovieResult
            .subscribe {
                mutableLiveDataItems.value = it
            })
    }
}

// PagingAdapter

class PagingAdapter : PagingDataAdapter<ResultsItem, PagingAdapter.ViewHolder>(REPO_COMPARATOR) {

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        getItem(position).takeIf { it != null }?.let {
            holder.bind(it)
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder =
        ViewHolder.create(parent)

    companion object {
        private val REPO_COMPARATOR = object : DiffUtil.ItemCallback<ResultsItem>() {
            override fun areItemsTheSame(oldItem: ResultsItem, newItem: ResultsItem): Boolean =
                oldItem.id == newItem.id

            override fun areContentsTheSame(oldItem: ResultsItem, newItem: ResultsItem): Boolean =
                oldItem == newItem
        }
    }

    class ViewHolder(private val binding: ItemMovieBinding) :
        RecyclerView.ViewHolder(binding.root) {
        fun bind(movie: ResultsItem) {
            binding.tvMoviesName.text = movie.title
        }

        companion object {
            fun create(parent: ViewGroup) = ViewHolder(
                ItemMovieBinding.inflate(LayoutInflater.from(parent.context), parent, false)
            )
        }
    }
}


// Observer Data di Fragmentnya

viewModel.getMovies()
        observe(viewModel.mutableLiveDataItems) {
            adapter.submitData(lifecycle, it)
        }

adapter.addLoadStateListener { loadState ->
            /*binding.progressBar.isVisible =
                (loadState.source.refresh is LoadState.Loading *//*|| loadState.source.append is LoadState.Loading*//*)

            val errorState = loadState.source.append as? LoadState.Error
                ?: loadState.source.prepend as? LoadState.Error
                ?: loadState.append as? LoadState.Error
                ?: loadState.prepend as? LoadState.Error

            if (errorState != null) {
                Toast.makeText(
                    requireContext(),
                    "\uD83D\uDE28 Wooops ${errorState.error}",
                    Toast.LENGTH_LONG
                ).show()
            }*/
        }