Use custom QueryPagingSource (#7321)

* Use custom QueryPagingSource

- Adds placeholder to make the list jump around less
- Fixes issue where SQLDelight QueryPagingSource would throw IndexOutOfBounds

* Review Changes

app/src/main/java/eu/kanade/data/AndroidDatabaseHandler.kt

@@ -2,8 +2,6 @@ package eu.kanade.data
 
 import androidx.paging.PagingSource
 import com.squareup.sqldelight.Query
-import com.squareup.sqldelight.Transacter
-import com.squareup.sqldelight.android.paging3.QueryPagingSource
 import com.squareup.sqldelight.db.SqlDriver
 import com.squareup.sqldelight.runtime.coroutines.asFlow
 import com.squareup.sqldelight.runtime.coroutines.mapToList
@@ -63,13 +61,11 @@ class AndroidDatabaseHandler(
 
     override fun <T : Any> subscribeToPagingSource(
         countQuery: Database.() -> Query<Long>,
-        transacter: Database.() -> Transacter,
         queryProvider: Database.(Long, Long) -> Query<T>,
     ): PagingSource<Long, T> {
         return QueryPagingSource(
-            countQuery = countQuery(db),
-            transacter = transacter(db),
-            dispatcher = queryDispatcher,
+            handler = this,
+            countQuery = countQuery,
             queryProvider = { limit, offset ->
                 queryProvider.invoke(db, limit, offset)
             },

app/src/main/java/eu/kanade/data/DatabaseHandler.kt

@@ -2,7 +2,6 @@ package eu.kanade.data
 
 import androidx.paging.PagingSource
 import com.squareup.sqldelight.Query
-import com.squareup.sqldelight.Transacter
 import eu.kanade.tachiyomi.Database
 import kotlinx.coroutines.flow.Flow
 
@@ -33,7 +32,6 @@ interface DatabaseHandler {
 
     fun <T : Any> subscribeToPagingSource(
         countQuery: Database.() -> Query<Long>,
-        transacter: Database.() -> Transacter,
         queryProvider: Database.(Long, Long) -> Query<T>,
     ): PagingSource<Long, T>
 }

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

@@ -0,0 +1,72 @@
+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()
+    }
+}

app/src/main/java/eu/kanade/data/history/HistoryRepositoryImpl.kt

@@ -19,7 +19,6 @@ class HistoryRepositoryImpl(
     override fun getHistory(query: String): PagingSource<Long, HistoryWithRelations> {
         return handler.subscribeToPagingSource(
             countQuery = { historyViewQueries.countHistory(query) },
-            transacter = { historyViewQueries },
             queryProvider = { limit, offset ->
                 historyViewQueries.history(query, limit, offset, historyWithRelationsMapper)
             },