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wip: Alternate CachedTimelineRemoteMediator implementation #1243

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wip: Alternate CachedTimelineRemoteMediator implementation #1243

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101 changes: 45 additions & 56 deletions app/src/main/java/app/pachli/components/timeline/viewmodel/CachedTimelineRemoteMediator.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,12 @@ import retrofit2.HttpException
import retrofit2.Response
import timber.log.Timber

fun RemoteKeyKind.Companion.from(loadType: LoadType) = when (loadType) {
LoadType.REFRESH -> RemoteKeyKind.REFRESH
LoadType.PREPEND -> RemoteKeyKind.PREV
LoadType.APPEND -> RemoteKeyKind.NEXT
}

@OptIn(ExperimentalPagingApi::class)
class CachedTimelineRemoteMediator(
private val mastodonApi: MastodonApi,
Expand All @@ -54,86 +60,69 @@ class CachedTimelineRemoteMediator(
state: PagingState<Int, TimelineStatusWithAccount>,
): MediatorResult {
Timber.d("load(), account ID: %d, LoadType = %s", pachliAccountId, loadType)

return try {
val response = when (loadType) {
LoadType.REFRESH -> {
// Ignore the provided state, always try and fetch from the remote
// REFRESH key.
val statusId = remoteKeyDao.remoteKeyForKind(
pachliAccountId,
RKE_TIMELINE_ID,
RemoteKeyKind.REFRESH,
)?.key
Timber.d("Loading from item: %s", statusId)
getInitialPage(statusId, state.config.pageSize)
}
transactionProvider {
val remoteKey = remoteKeyDao.remoteKeyForKind(
pachliAccountId,
RKE_TIMELINE_ID,
RemoteKeyKind.from(loadType),
)?.key
Timber.d(" from remoteKey: %s", remoteKey)

LoadType.PREPEND -> {
val rke = remoteKeyDao.remoteKeyForKind(
pachliAccountId,
RKE_TIMELINE_ID,
RemoteKeyKind.PREV,
) ?: return MediatorResult.Success(endOfPaginationReached = true)
Timber.d("Loading from remoteKey: %s", rke)
mastodonApi.homeTimeline(minId = rke.key, limit = state.config.pageSize)
// - Load the data
val response = when (loadType) {
LoadType.REFRESH -> getInitialPage(remoteKey, state.config.pageSize)
LoadType.PREPEND -> mastodonApi.homeTimeline(minId = remoteKey, limit = state.config.pageSize)
LoadType.APPEND -> mastodonApi.homeTimeline(maxId = remoteKey, limit = state.config.pageSize)
}

LoadType.APPEND -> {
val rke = remoteKeyDao.remoteKeyForKind(
pachliAccountId,
RKE_TIMELINE_ID,
RemoteKeyKind.NEXT,
) ?: return MediatorResult.Success(endOfPaginationReached = true)
Timber.d("Loading from remoteKey: %s", rke)
mastodonApi.homeTimeline(maxId = rke.key, limit = state.config.pageSize)
val statuses = response.body()
if (!response.isSuccessful || statuses == null) {
return@transactionProvider MediatorResult.Error(HttpException(response))
}
}

val statuses = response.body()
if (!response.isSuccessful || statuses == null) {
return MediatorResult.Error(HttpException(response))
}
Timber.d(" %d - # statuses loaded", statuses.size)

Timber.d("%d - # statuses loaded", statuses.size)

// This request succeeded with no new data, and pagination ends (unless this is a
// REFRESH, which must always set endOfPaginationReached to false).
if (statuses.isEmpty()) {
return MediatorResult.Success(endOfPaginationReached = loadType != LoadType.REFRESH)
}
// This request succeeded with no new data, and pagination ends (unless this is a
// REFRESH, which must always set endOfPaginationReached to false).
if (statuses.isEmpty()) {
val endOfPaginationReached = loadType != LoadType.REFRESH
Timber.d(" No statuses found, returning Success(endOfPaginationReached = %s", endOfPaginationReached)
return@transactionProvider MediatorResult.Success(endOfPaginationReached)
}

Timber.d(" %s..%s", statuses.first().id, statuses.last().id)
Timber.d(" %s..%s", statuses.first().id, statuses.last().id)

val links = Links.from(response.headers()["link"])
val links = Links.from(response.headers()["link"])
val next = links.next ?: statuses.last().id
val prev = links.prev ?: statuses.first().id

transactionProvider {
when (loadType) {
LoadType.REFRESH -> {
remoteKeyDao.deletePrevNext(pachliAccountId, RKE_TIMELINE_ID)
timelineDao.deleteAllStatusesForAccount(pachliAccountId)

Timber.d(" Saving new prev key: %s", prev)
remoteKeyDao.upsert(
RemoteKeyEntity(
pachliAccountId,
RKE_TIMELINE_ID,
RemoteKeyKind.NEXT,
links.next,
RemoteKeyKind.PREV,
prev,
),
)

Timber.d(" Saving new next key: %s", next)
remoteKeyDao.upsert(
RemoteKeyEntity(
pachliAccountId,
RKE_TIMELINE_ID,
RemoteKeyKind.PREV,
links.prev,
RemoteKeyKind.NEXT,
next,
),
)
}
// links.prev may be null if there are no statuses, only set if non-null,
// https://github.com/mastodon/mastodon/issues/25760
LoadType.PREPEND -> links.prev?.let { prev ->

LoadType.PREPEND -> {
Timber.d(" Saving new prev key: %s", prev)
remoteKeyDao.upsert(
RemoteKeyEntity(
pachliAccountId,
Expand All @@ -143,9 +132,9 @@ class CachedTimelineRemoteMediator(
),
)
}
// links.next may be null if there are no statuses, only set if non-null,
// https://github.com/mastodon/mastodon/issues/25760
LoadType.APPEND -> links.next?.let { next ->

LoadType.APPEND -> {
Timber.d(" Saving new next key: %s", next)
remoteKeyDao.upsert(
RemoteKeyEntity(
pachliAccountId,
Expand Down
3 changes: 3 additions & 0 deletions core/database/src/main/kotlin/app/pachli/core/database/model/RemoteKeyEntity.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -70,5 +70,8 @@ data class RemoteKeyEntity(
* the list.
*/
REFRESH,
;

companion object
}
}
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