SwapiPeopleDataSource.kt

class SwapiPeopleDataSource(val useCase: GetPeopleUseCase) : PageKeyedDataSource<Int, Person?>() {

    override fun loadInitial(params: LoadInitialParams<Int>, callback: LoadInitialCallback<Int, Person?>) {
        async {
            val items = useCase.execute(page = 1).await()
            callback.onResult(items.orEmpty(), null, 2)
        }
    }

    override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, Person?>) {
        async {
            val items = useCase.execute(page = params.key).await()
            callback.onResult(items.orEmpty(), params.key.inc())
        }
    }

    override fun loadBefore(params: LoadParams<Int>, callback: LoadCallback<Int, Person?>) {
        async {
            val items = useCase.execute(page = params.key).await()
            callback.onResult(items.orEmpty(), params.key.dec())
        }
    }
}