tachiyomi/app/src/main/java/eu/kanade/data/QueryPagingSource.kt

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2.4 KiB
Kotlin
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package eu.kanade.data
import androidx.paging.PagingSource
import androidx.paging.PagingState
import com.squareup.sqldelight.Query
import eu.kanade.tachiyomi.Database
import kotlin.properties.Delegates
class QueryPagingSource<RowType : Any>(
val handler: DatabaseHandler,
val countQuery: Database.() -> Query<Long>,
val queryProvider: Database.(Long, Long) -> Query<RowType>,
) : PagingSource<Long, RowType>(), Query.Listener {
override val jumpingSupported: Boolean = true
private var currentQuery: Query<RowType>? by Delegates.observable(null) { _, old, new ->
old?.removeListener(this)
new?.addListener(this)
}
init {
registerInvalidatedCallback {
currentQuery?.removeListener(this)
currentQuery = null
}
}
override suspend fun load(params: LoadParams<Long>): LoadResult<Long, RowType> {
try {
val key = params.key ?: 0L
val loadSize = params.loadSize
val count = handler.awaitOne { countQuery() }
val (offset, limit) = when (params) {
is LoadParams.Prepend -> key - loadSize to loadSize.toLong()
else -> key to loadSize.toLong()
}
val data = handler.awaitList {
queryProvider(limit, offset)
.also { currentQuery = it }
}
val (prevKey, nextKey) = when (params) {
is LoadParams.Append -> { offset - loadSize to offset + loadSize }
else -> { offset to offset + loadSize }
}
return LoadResult.Page(
data = data,
prevKey = if (offset <= 0L || prevKey < 0L) null else prevKey,
nextKey = if (offset + loadSize >= count) null else nextKey,
itemsBefore = maxOf(0L, offset).toInt(),
itemsAfter = maxOf(0L, count - (offset + loadSize)).toInt(),
)
} catch (e: Exception) {
return LoadResult.Error(throwable = e)
}
}
override fun getRefreshKey(state: PagingState<Long, RowType>): Long? {
return state.anchorPosition?.let { anchorPosition ->
val anchorPage = state.closestPageToPosition(anchorPosition)
anchorPage?.prevKey ?: anchorPage?.nextKey
}
}
override fun queryResultsChanged() {
invalidate()
}
}