Fix manga downloading

app/src/main/java/org/koitharu/kotatsu/utils/RecyclerViewScrollCallback.kt

@@ -1,10 +1,15 @@
 package org.koitharu.kotatsu.utils
 
+import androidx.annotation.Px
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import java.lang.ref.WeakReference
 
-class RecyclerViewScrollCallback(recyclerView: RecyclerView, private val position: Int) : Runnable {
+class RecyclerViewScrollCallback(
+	recyclerView: RecyclerView,
+	private val position: Int,
+	@Px private val offset: Int,
+) : Runnable {
 
 	private val recyclerViewRef = WeakReference(recyclerView)
 
@@ -13,7 +18,7 @@ class RecyclerViewScrollCallback(recyclerView: RecyclerView, private val positio
 		val lm = rv.layoutManager ?: return
 		rv.stopScroll()
 		if (lm is LinearLayoutManager) {
-			lm.scrollToPositionWithOffset(position, 0)
+			lm.scrollToPositionWithOffset(position, offset)
 		} else {
 			lm.scrollToPosition(position)
 		}

app/src/main/java/org/koitharu/kotatsu/utils/ext/FlowExt.kt

@@ -1,9 +1,11 @@
 package org.koitharu.kotatsu.utils.ext
 
+import android.os.SystemClock
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
-import kotlinx.coroutines.flow.transform
+import kotlinx.coroutines.flow.transformLatest
 
 fun <T> Flow<T>.onFirst(action: suspend (T) -> Unit): Flow<T> {
 	var isFirstCall = true
@@ -17,4 +19,19 @@ fun <T> Flow<T>.onFirst(action: suspend (T) -> Unit): Flow<T> {
 
 inline fun <T, R> Flow<List<T>>.mapItems(crossinline transform: (T) -> R): Flow<List<R>> {
 	return map { list -> list.map(transform) }
+}
+
+fun <T> Flow<T>.throttle(timeoutMillis: (T) -> Long): Flow<T> {
+	var lastEmittedAt = 0L
+	return transformLatest { value ->
+		val delay = timeoutMillis(value)
+		val now = SystemClock.elapsedRealtime()
+		if (delay > 0L) {
+			if (lastEmittedAt + delay < now) {
+				delay(lastEmittedAt + delay - now)
+			}
+		}
+		emit(value)
+		lastEmittedAt = now
+	}
 }