GitHubUserDataSource.kt

class UserDataSource(
    private val query: String,
    private val githubService: GitHubService,
    private val compositeDisposable: CompositeDisposable
) : PageKeyedDataSource<String, User>() {

    val lifecycle by lazy { MutableLiveData<DataSourceLifecycle>() }

    override fun loadInitial(
        params: LoadInitialParams<String>,
        callback: LoadInitialCallback<String, User>
    ) {
        compositeDisposable.add(
            githubService.getUsersCall(query)
                .single()
                .lifecycleResponse(lifecycle)
                .subscribe { response ->
                    val links = response.headers().get("Link")
                        ?.let { PageLinks(it) }
                    val users = response.body()?.items ?: emptyList()
                    callback.onResult(users, links?.prev, links?.next)
                }
        )
    }

    override fun loadAfter(params: LoadParams<String>, callback: LoadCallback<String, User>) {
        compositeDisposable.add(
            githubService.getUsersCallByUrl(params.key)
                .single()
                .lifecycleResponse(lifecycle)
                .subscribe { response ->
                    val links = response.headers().get("Link")
                        ?.let { PageLinks(it) }
                    val users = response.body()?.items ?: emptyList()
                    callback.onResult(users, links?.next)
                }
        )
    }

    override fun loadBefore(params: LoadParams<String>, callback: LoadCallback<String, User>) {
        compositeDisposable.add(
            githubService.getUsersCallByUrl(params.key)
                .single()
                .lifecycleResponse(lifecycle)
                .subscribe { response ->
                    val links = response.headers().get("Link")
                        ?.let { PageLinks(it) }
                    val users = response.body()?.items ?: emptyList()
                    callback.onResult(users, links?.prev)
                }
        )
    }
}