Save reader state on idle

app/src/main/java/org/koitharu/kotatsu/reader/ui/ReaderActivity.kt

@@ -40,6 +40,7 @@ import org.koitharu.kotatsu.reader.ui.thumbnails.OnPageSelectListener
 import org.koitharu.kotatsu.reader.ui.thumbnails.PagesThumbnailsSheet
 import org.koitharu.kotatsu.settings.SettingsActivity
 import org.koitharu.kotatsu.utils.GridTouchHelper
+import org.koitharu.kotatsu.utils.IdlingDetector
 import org.koitharu.kotatsu.utils.ShareHelper
 import org.koitharu.kotatsu.utils.ext.*
 
@@ -51,11 +52,14 @@ class ReaderActivity :
 	OnPageSelectListener,
 	ReaderConfigBottomSheet.Callback,
 	ReaderControlDelegate.OnInteractionListener,
-	OnApplyWindowInsetsListener {
+	OnApplyWindowInsetsListener,
+	IdlingDetector.Callback {
 
 	@Inject
 	lateinit var viewModelFactory: ReaderViewModel.Factory
 
+	private val idlingDetector = IdlingDetector(TimeUnit.SECONDS.toMillis(10), this)
+
 	val viewModel by assistedViewModels {
 		viewModelFactory.create(
 			intent = MangaIntent(intent),
@@ -89,6 +93,7 @@ class ReaderActivity :
 		binding.slider.setLabelFormatter(PageLabelFormatter())
 		ReaderSliderListener(this, viewModel).attachToSlider(binding.slider)
 		insetsDelegate.interceptingWindowInsetsListener = this
+		idlingDetector.bindToLifecycle(this)
 
 		viewModel.onError.observe(this, this::onError)
 		viewModel.readerMode.observe(this, this::onInitReader)
@@ -111,6 +116,11 @@ class ReaderActivity :
 	override fun onUserInteraction() {
 		super.onUserInteraction()
 		pageSwitchTimer.onUserInteraction()
+		idlingDetector.onUserInteraction()
+	}
+
+	override fun onIdle() {
+		viewModel.saveCurrentState(readerManager.currentReader?.getCurrentState())
 	}
 
 	private fun onInitReader(mode: ReaderMode) {

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

@@ -0,0 +1,37 @@
+package org.koitharu.kotatsu.utils
+
+import android.os.Handler
+import android.os.Looper
+import androidx.lifecycle.DefaultLifecycleObserver
+import androidx.lifecycle.LifecycleOwner
+
+class IdlingDetector(
+	private val timeoutMs: Long,
+	private val callback: Callback,
+) : DefaultLifecycleObserver {
+
+	private val handler = Handler(Looper.getMainLooper())
+	private val idleRunnable = Runnable {
+		callback.onIdle()
+	}
+
+	fun bindToLifecycle(owner: LifecycleOwner) {
+		owner.lifecycle.addObserver(this)
+	}
+
+	fun onUserInteraction() {
+		handler.removeCallbacks(idleRunnable)
+		handler.postDelayed(idleRunnable, timeoutMs)
+	}
+
+	override fun onDestroy(owner: LifecycleOwner) {
+		super.onDestroy(owner)
+		owner.lifecycle.removeObserver(this)
+		handler.removeCallbacks(idleRunnable)
+	}
+
+	fun interface Callback {
+
+		fun onIdle()
+	}
+}