MoviePagingSource.kt

class MoviePagingSource(private val service: MovieServices = MovieServiceBuilder.build()) : PagingSource<Int, ResponseModel.MovieModel>() {

    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, ResponseModel.MovieModel> {

        val pagePosition = params.key ?: STARTING_PAGE_INDEX

        return try {

            val data = service.getMovie(API_KEY, LANGUAGE, pagePosition).movieList //using retrofit
            val prevKey = if (pagePosition == STARTING_PAGE_INDEX) null else pagePosition - 1
            val nextKey = if (data.isEmpty()) null else pagePosition + 1

            LoadResult.Page(data, prevKey, nextKey)
        } catch (exception: Exception){
            LoadResult.Error(exception)
        }
    }

    companion object{
        private const val STARTING_PAGE_INDEX = 1
        private const val API_KEY = "......."
        private const val LANGUAGE = "en-EN"
    }
}