create MultiStackNavigationExecutor in ViewModel

navigation/src/androidMain/kotlin/com/hoc081098/solivagant/navigation/internal/savedStateHandleAndroidSupport.android.kt

@@ -5,7 +5,7 @@ import android.os.Bundle
 import android.os.Parcelable
 import androidx.lifecycle.SavedStateHandle
 
-internal actual fun SavedStateHandle.setSavedStateProvider(
+internal actual fun SavedStateHandle.setSavedStateProviderX(
   key: String,
   savedStateFactory: () -> Map<String, Any?>,
 ) = setSavedStateProvider(key) {

navigation/src/commonMain/kotlin/com/hoc081098/solivagant/navigation/internal/MultiStackNavigationExecutor.kt

@@ -37,15 +37,7 @@ internal class MultiStackNavigationExecutor(
   val canNavigateBack: State<Boolean>
     get() = stack.canNavigateBack
 
-  internal fun saveState() {
-    viewModel.globalSavedStateHandle[SAVED_STATE_STACK] = stack.saveState()
-  }
-
   init {
-    viewModel
-      .globalSavedStateHandle
-      .setSavedStateProvider(SAVED_STATE_STACK, stack::saveState)
-
     _lifecycleOwner
       .flatMapLatest { it?.lifecycle?.eventFlow ?: emptyFlow() }
       .onEach(stack::handleLifecycleEvent)
@@ -121,10 +113,7 @@ internal class MultiStackNavigationExecutor(
     _lifecycleOwner.value = lifecycleOwner
   }
 
-  internal companion object {
-    const val SAVED_STATE_STACK = "com.hoc081098.solivagant.navigation.stack"
-  }
-
+  //region RememberObserver
   override fun onAbandoned() {
     _lifecycleOwner.value = null
     scope.cancel()
@@ -136,4 +125,5 @@ internal class MultiStackNavigationExecutor(
   }
 
   override fun onRemembered() = Unit
+  //endregion
 }

navigation/src/commonMain/kotlin/com/hoc081098/solivagant/navigation/internal/MultiStackNavigationExecutorBuilder.kt

@@ -23,44 +23,17 @@ internal fun rememberNavigationExecutor(
     },
   ),
 ): MultiStackNavigationExecutor {
-  val lifecycleOwner = LocalLifecycleOwner.current
-
+  // setInputStartRoot must be called before getMultiStackNavigationExecutor
   viewModel.setInputStartRoot(startRoot)
 
+  val lifecycleOwner = LocalLifecycleOwner.current
   val executor = remember(viewModel) {
-    val contentDestinations = destinations.filterIsInstance<ContentDestination<*>>()
-
-    val navState = viewModel.getSavedStackState()
-    val hostLifecycleState = lifecycleOwner.lifecycle.currentState
-
-    val stack = if (navState == null) {
-      MultiStack.createWith(
-        root = viewModel.savedNavRoot!!,
-        destinations = contentDestinations,
-        hostLifecycleState = hostLifecycleState,
-        onStackEntryRemoved = viewModel::removeEntry,
-      )
-    } else {
-      MultiStack.fromState(
-        root = viewModel.savedNavRoot!!,
-        bundle = navState,
-        destinations = contentDestinations,
-        hostLifecycleState = hostLifecycleState,
-        onStackEntryRemoved = viewModel::removeEntry,
-      )
-    }
-
-    @Suppress("ViewModelForwarding")
-    MultiStackNavigationExecutor(
-      stack = stack,
-      viewModel = viewModel,
-      onRootChanged = viewModel::setStartRoot,
+    viewModel.createMultiStackNavigationExecutor(
+      contentDestinations = destinations.filterIsInstance<ContentDestination<*>>(),
+      hostLifecycleState = lifecycleOwner.lifecycle.currentState,
     )
   }
-
   executor.setLifecycleOwner(lifecycleOwner)
 
-  NonAndroidSaveStackState(executor)
-
   return executor
 }

navigation/src/commonMain/kotlin/com/hoc081098/solivagant/navigation/internal/StoreViewModel.kt

@@ -3,10 +3,11 @@ package com.hoc081098.solivagant.navigation.internal
 import com.hoc081098.kmp.viewmodel.SavedStateHandle
 import com.hoc081098.kmp.viewmodel.SavedStateHandleFactory
 import com.hoc081098.kmp.viewmodel.ViewModel
+import com.hoc081098.solivagant.lifecycle.Lifecycle
 import com.hoc081098.solivagant.navigation.BaseRoute
+import com.hoc081098.solivagant.navigation.ContentDestination
 import com.hoc081098.solivagant.navigation.EXTRA_ROUTE
 import com.hoc081098.solivagant.navigation.NavRoot
-import com.hoc081098.solivagant.navigation.internal.MultiStackNavigationExecutor.Companion.SAVED_STATE_STACK
 
 internal class StoreViewModel(
   internal val globalSavedStateHandle: SavedStateHandle,
@@ -15,7 +16,14 @@ internal class StoreViewModel(
   private val savedStateHandles = mutableMapOf<StackEntry.Id, SavedStateHandle>()
   private val savedStateHandleFactories = mutableMapOf<StackEntry.Id, SavedStateHandleFactory>()
 
-  internal val savedNavRoot: NavRoot? get() = globalSavedStateHandle[SAVED_START_ROOT_KEY]
+  private var stack: MultiStack? = null
+  private var executor: MultiStackNavigationExecutor? = null
+
+  init {
+    globalSavedStateHandle.setSavedStateProviderX(SAVED_STATE_STACK) {
+      checkNotNull(stack) { "Stack is null. This should never happen" }.saveState()
+    }
+  }
 
   internal fun provideStore(id: StackEntry.Id): NavigationExecutor.Store {
     return stores.getOrPut(id) { NavigationExecutorStore() }
@@ -34,7 +42,7 @@ internal class StoreViewModel(
     }
   }
 
-  internal fun removeEntry(id: StackEntry.Id) {
+  private fun removeEntry(id: StackEntry.Id) {
     val store = stores.remove(id)
     store?.close()
 
@@ -82,14 +90,49 @@ internal class StoreViewModel(
     }
   }
 
-  internal fun setStartRoot(root: NavRoot) {
+  private fun setStartRoot(root: NavRoot) {
     globalSavedStateHandle[SAVED_START_ROOT_KEY] = root
   }
 
-  internal fun getSavedStackState(): Map<String, Any?>? =
-    globalSavedStateHandle.getAsMap(SAVED_STATE_STACK)
+  fun createMultiStackNavigationExecutor(
+    contentDestinations: List<ContentDestination<*>>,
+    hostLifecycleState: Lifecycle.State,
+  ): MultiStackNavigationExecutor =
+    executor
+      ?: MultiStackNavigationExecutor(
+        stack = createMultiStackIfNeeded(contentDestinations, hostLifecycleState),
+        viewModel = this,
+        onRootChanged = ::setStartRoot,
+      ).also { this.executor = it }
+
+  private fun createMultiStackIfNeeded(
+    contentDestinations: List<ContentDestination<*>>,
+    hostLifecycleState: Lifecycle.State,
+  ): MultiStack {
+    this.stack?.let { return it }
+
+    val navState = globalSavedStateHandle.getAsMap(SAVED_STATE_STACK)
+    val savedNavRoot: NavRoot? = globalSavedStateHandle[SAVED_START_ROOT_KEY]
+    return if (navState == null) {
+      MultiStack.createWith(
+        root = savedNavRoot!!,
+        destinations = contentDestinations,
+        hostLifecycleState = hostLifecycleState,
+        onStackEntryRemoved = ::removeEntry,
+      )
+    } else {
+      MultiStack.fromState(
+        root = savedNavRoot!!,
+        bundle = navState,
+        destinations = contentDestinations,
+        hostLifecycleState = hostLifecycleState,
+        onStackEntryRemoved = ::removeEntry,
+      )
+    }.also { this.stack = it }
+  }
 
   private companion object {
+    private const val SAVED_STATE_STACK = "com.hoc081098.solivagant.navigation.stack"
     private const val SAVED_START_ROOT_KEY = "com.hoc081098.solivagant.navigation.store.start_root"
     private const val SAVED_INPUT_START_ROOT_KEY = "com.hoc081098.solivagant.navigation.store.input_start_root"
   }

navigation/src/commonMain/kotlin/com/hoc081098/solivagant/navigation/internal/savedStateHandleAndroidSupport.kt

@@ -2,7 +2,7 @@ package com.hoc081098.solivagant.navigation.internal
 
 import com.hoc081098.kmp.viewmodel.SavedStateHandle
 
-internal expect fun SavedStateHandle.setSavedStateProvider(
+internal expect fun SavedStateHandle.setSavedStateProviderX(
   key: String,
   savedStateFactory: () -> Map<String, Any?>,
 )

navigation/src/nonAndroidMain/kotlin/com/hoc081098/solivagant/navigation/internal/savedStateHandleAndroidSupport.nonAndroid.kt

@@ -2,7 +2,7 @@ package com.hoc081098.solivagant.navigation.internal
 
 import com.hoc081098.kmp.viewmodel.SavedStateHandle
 
-internal actual fun SavedStateHandle.setSavedStateProvider(
+internal actual fun SavedStateHandle.setSavedStateProviderX(
   key: String,
   savedStateFactory: () -> Map<String, Any?>,
 ) {