问分页3-如何处理自beta01以来出现的旧的APPEND RemoteMediator请求？

EN

private const val GITHUB_STARTING_PAGE_INDEX = 1

@OptIn(ExperimentalPagingApi::class)
class GithubRemoteMediator(
        private val query: String,
        private val service: GithubService,
        private val repoDatabase: RepoDatabase
) : RemoteMediator<Int, Repo>() {

    override suspend fun load(loadType: LoadType, state: PagingState<Int, Repo>): MediatorResult {

        val page = when (loadType) {
            LoadType.REFRESH -> GITHUB_STARTING_PAGE_INDEX
            LoadType.PREPEND -> return MediatorResult.Success(true)
            LoadType.APPEND -> {
                // this can run with an outdated PagingState from the previous RemoteMediator instance, causing the Exception to be thrown
                val remoteKeys = getRemoteKeyForLastItem(state)
                if (remoteKeys == null || remoteKeys.nextKey == null) {
                    throw InvalidObjectException("Remote key should not be null for $loadType")
                }
                remoteKeys.nextKey
            }

        }

        val apiQuery = query + IN_QUALIFIER

        try {
            val apiResponse = service.searchRepos(apiQuery, page, state.config.pageSize)

            val repos = apiResponse.items
            val endOfPaginationReached = repos.isEmpty()
            repoDatabase.withTransaction {
                if (loadType == LoadType.REFRESH) {
                    repoDatabase.remoteKeysDao().clearRemoteKeys()
                    repoDatabase.reposDao().clearRepos()
                }
                val prevKey = if (page == GITHUB_STARTING_PAGE_INDEX) null else page - 1
                val nextKey = if (endOfPaginationReached) null else page + 1
                val keys = repos.map {
                    RemoteKeys(repoId = it.id, prevKey = prevKey, nextKey = nextKey)
                }
                repoDatabase.remoteKeysDao().insertAll(keys)
                repoDatabase.reposDao().insertAll(repos)
            }
            return MediatorResult.Success(endOfPaginationReached = endOfPaginationReached)
        } catch (exception: IOException) {
            return MediatorResult.Error(exception)
        } catch (exception: HttpException) {
            return MediatorResult.Error(exception)
        }
    }

    private suspend fun getRemoteKeyForLastItem(state: PagingState<Int, Repo>): RemoteKeys? {
        return state.pages.lastOrNull() { it.data.isNotEmpty() }?.data?.lastOrNull()
                ?.let { repo ->
                    repoDatabase.remoteKeysDao().remoteKeysRepoId(repo.id)
                }
    }
}