save and restoring state view model

domains/android/compose-core/src/main/kotlin/app/dapk/st/core/ActivityExtensions.kt

@@ -3,7 +3,11 @@ package app.dapk.st.core
 import androidx.activity.ComponentActivity
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelLazy
+import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.ViewModelProvider.*
+import androidx.lifecycle.ViewModelStore
+import androidx.lifecycle.viewmodel.CreationExtras
+import kotlin.reflect.KClass
 
 inline fun <reified VM : ViewModel> ComponentActivity.viewModel(
     noinline factory: () -> VM
@@ -17,3 +21,53 @@ inline fun <reified VM : ViewModel> ComponentActivity.viewModel(
     }
     return ViewModelLazy(VM::class, { viewModelStore }, { factoryPromise })
 }
+
+
+inline fun <reified S, E> ComponentActivity.state(
+    noinline factory: () -> StateViewModel<S, E>
+): Lazy<State<S, E>> {
+    val factoryPromise = object : Factory {
+        override fun <T : ViewModel> create(modelClass: Class<T>): T {
+            return when(modelClass) {
+                StateViewModel::class.java -> factory() as T
+                else -> throw Error()
+            }
+        }
+    }
+    return FooViewModelLazy(
+        key = S::class.java.canonicalName!!,
+        StateViewModel::class,
+        { viewModelStore },
+        { factoryPromise }
+    ) as Lazy<State<S, E>>
+}
+
+class FooViewModelLazy<VM : ViewModel> @JvmOverloads constructor(
+    private val key: String,
+    private val viewModelClass: KClass<VM>,
+    private val storeProducer: () -> ViewModelStore,
+    private val factoryProducer: () -> ViewModelProvider.Factory,
+    private val extrasProducer: () -> CreationExtras = { CreationExtras.Empty }
+) : Lazy<VM> {
+    private var cached: VM? = null
+
+    override val value: VM
+        get() {
+            val viewModel = cached
+            return if (viewModel == null) {
+                val factory = factoryProducer()
+                val store = storeProducer()
+                ViewModelProvider(
+                    store,
+                    factory,
+                    extrasProducer()
+                ).get(key, viewModelClass.java).also {
+                    cached = it
+                }
+            } else {
+                viewModel
+            }
+        }
+
+    override fun isInitialized(): Boolean = cached != null
+}

domains/android/compose-core/src/main/kotlin/app/dapk/st/core/StateViewModel.kt

@@ -16,11 +16,11 @@ import kotlinx.coroutines.launch
 class StateViewModel<S, E>(
     reducerFactory: ReducerFactory<S>,
     eventSource: MutableSharedFlow<E>,
-) : ViewModel(), StateStore<S, E> {
+) : ViewModel(), State<S, E> {
 
     private val store: Store<S> = createStore(reducerFactory, viewModelScope)
     override val events: SharedFlow<E> = eventSource
-    override val state
+    override val current
         get() = _state!!
     private var _state: S by mutableStateOf(store.getState())
 
@@ -42,8 +42,8 @@ fun <S, E> createStateViewModel(block: (suspend (E) -> Unit) -> ReducerFactory<S
     return StateViewModel(reducer, eventSource)
 }
 
-interface StateStore<S, E> {
+interface State<S, E> {
     fun dispatch(action: Action)
     val events: SharedFlow<E>
-    val state: S
+    val current: S
 }

features/directory/src/main/kotlin/app/dapk/st/directory/DirectoryListingScreen.kt

@@ -35,9 +35,13 @@ import app.dapk.st.design.components.CircleishAvatar
 import app.dapk.st.design.components.GenericEmpty
 import app.dapk.st.design.components.GenericError
 import app.dapk.st.design.components.Toolbar
-import app.dapk.st.directory.DirectoryEvent.OpenDownloadUrl
+import app.dapk.st.directory.state.DirectoryEvent.OpenDownloadUrl
-import app.dapk.st.directory.DirectoryScreenState.Content
+import app.dapk.st.directory.state.DirectoryScreenState.Content
-import app.dapk.st.directory.DirectoryScreenState.EmptyLoading
+import app.dapk.st.directory.state.DirectoryScreenState.EmptyLoading
+import app.dapk.st.directory.state.ComponentLifecycle
+import app.dapk.st.directory.state.DirectoryEvent
+import app.dapk.st.directory.state.DirectoryScreenState
+import app.dapk.st.directory.state.DirectoryState
 import app.dapk.st.engine.DirectoryItem
 import app.dapk.st.engine.RoomOverview
 import app.dapk.st.engine.Typing
@@ -53,8 +57,8 @@ import java.time.temporal.ChronoUnit
 import kotlin.math.roundToInt
 
 @Composable
-fun DirectoryScreen(directoryViewModel: DirectoryViewModel) {
+fun DirectoryScreen(directoryViewModel: DirectoryState) {
-    val state = directoryViewModel.state
+    val state = directoryViewModel.current
 
     val listState: LazyListState = rememberLazyListState(
         initialFirstVisibleItemIndex = 0,
@@ -101,7 +105,7 @@ fun DirectoryScreen(directoryViewModel: DirectoryViewModel) {
 }
 
 @Composable
-private fun DirectoryViewModel.ObserveEvents(listState: LazyListState, toolbarPosition: MutableState<Float>) {
+private fun DirectoryState.ObserveEvents(listState: LazyListState, toolbarPosition: MutableState<Float>) {
     val context = LocalContext.current
     StartObserving {
         this@ObserveEvents.events.launch {

features/directory/src/main/kotlin/app/dapk/st/directory/DirectoryModule.kt

@@ -4,6 +4,9 @@ import android.content.Context
 import app.dapk.st.core.ProvidableModule
 import app.dapk.st.core.StateViewModel
 import app.dapk.st.core.createStateViewModel
+import app.dapk.st.directory.state.DirectoryEvent
+import app.dapk.st.directory.state.DirectoryScreenState
+import app.dapk.st.directory.state.directoryReducer
 import app.dapk.st.engine.ChatEngine
 
 class DirectoryModule(

features/directory/src/main/kotlin/app/dapk/st/directory/state/DirectoryAction.kt

@@ -0,0 +1,18 @@
+package app.dapk.st.directory.state
+
+import app.dapk.st.engine.DirectoryState
+import app.dapk.state.Action
+
+sealed interface ComponentLifecycle : Action {
+    object OnVisible : ComponentLifecycle
+    object OnGone : ComponentLifecycle
+}
+
+sealed interface DirectorySideEffect : Action {
+    object ScrollToTop : DirectorySideEffect
+}
+
+sealed interface DirectoryStateChange : Action {
+    object Empty : DirectoryStateChange
+    data class Content(val content: DirectoryState) : DirectoryStateChange
+}

features/directory/src/main/kotlin/app/dapk/st/directory/state/DirectoryReducer.kt

@@ -1,15 +1,12 @@
-package app.dapk.st.directory
+package app.dapk.st.directory.state
 
-import app.dapk.st.core.StateStore
+import app.dapk.st.directory.ShortcutHandler
 import app.dapk.st.engine.ChatEngine
-import app.dapk.st.engine.DirectoryState
 import app.dapk.state.*
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 
-typealias DirectoryViewModel = StateStore<DirectoryScreenState, DirectoryEvent>
-
 fun directoryReducer(
     chatEngine: ChatEngine,
     shortcutHandler: ShortcutHandler,
@@ -18,6 +15,7 @@ fun directoryReducer(
     var syncJob: Job? = null
     return createReducer(
         initialState = DirectoryScreenState.EmptyLoading,
+
         multi(ComponentLifecycle::class) { action ->
             when (action) {
                 ComponentLifecycle.OnVisible -> async { _ ->
@@ -33,28 +31,16 @@ fun directoryReducer(
                 ComponentLifecycle.OnGone -> sideEffect { _, _ -> syncJob?.cancel() }
             }
         },
+
         change(DirectoryStateChange::class) { action, _ ->
             when (action) {
                 is DirectoryStateChange.Content -> DirectoryScreenState.Content(action.content)
                 DirectoryStateChange.Empty -> DirectoryScreenState.Empty
             }
         },
+
         sideEffect(DirectorySideEffect.ScrollToTop::class) { _, _ ->
             eventEmitter(DirectoryEvent.ScrollToTop)
         }
     )
 }
-
-sealed interface ComponentLifecycle : Action {
-    object OnVisible : ComponentLifecycle
-    object OnGone : ComponentLifecycle
-}
-
-sealed interface DirectorySideEffect : Action {
-    object ScrollToTop : DirectorySideEffect
-}
-
-sealed interface DirectoryStateChange : Action {
-    object Empty : DirectoryStateChange
-    data class Content(val content: DirectoryState) : DirectoryStateChange
-}

features/directory/src/main/kotlin/app/dapk/st/directory/state/DirectoryState.kt

@@ -1,9 +1,11 @@
-package app.dapk.st.directory
+package app.dapk.st.directory.state
 
+import app.dapk.st.core.State
 import app.dapk.st.engine.DirectoryState
 
-sealed interface DirectoryScreenState {
+typealias DirectoryState = State<DirectoryScreenState, DirectoryEvent>
 
+sealed interface DirectoryScreenState {
     object EmptyLoading : DirectoryScreenState
     object Empty : DirectoryScreenState
     data class Content(
@@ -15,4 +17,3 @@ sealed interface DirectoryEvent {
     data class OpenDownloadUrl(val url: String) : DirectoryEvent
     object ScrollToTop : DirectoryEvent
 }
-

features/directory/src/test/kotlin/app/dapk/st/directory/DirectoryViewModelTest.kt

@@ -1,6 +1,8 @@
 package app.dapk.st.directory
 
 import ViewModelTest
+import app.dapk.st.directory.state.DirectoryScreenState
+import app.dapk.st.directory.state.DirectoryState
 import app.dapk.st.engine.DirectoryItem
 import app.dapk.st.engine.UnreadCount
 import fake.FakeChatEngine
@@ -18,7 +20,7 @@ class DirectoryViewModelTest {
     private val fakeShortcutHandler = FakeShortcutHandler()
     private val fakeChatEngine = FakeChatEngine()
 
-    private val viewModel = DirectoryViewModel(
+    private val viewModel = DirectoryState(
         fakeShortcutHandler.instance,
         fakeChatEngine,
         runViewModelTest.testMutableStateFactory(),

features/home/src/main/kotlin/app/dapk/st/home/HomeModule.kt

@@ -1,7 +1,7 @@
 package app.dapk.st.home
 
 import app.dapk.st.core.ProvidableModule
-import app.dapk.st.directory.DirectoryViewModel
+import app.dapk.st.directory.state.DirectoryState
 import app.dapk.st.domain.StoreModule
 import app.dapk.st.engine.ChatEngine
 import app.dapk.st.login.LoginViewModel
@@ -13,7 +13,7 @@ class HomeModule(
     val betaVersionUpgradeUseCase: BetaVersionUpgradeUseCase,
 ) : ProvidableModule {
 
-    fun homeViewModel(directory: DirectoryViewModel, login: LoginViewModel, profileViewModel: ProfileViewModel): HomeViewModel {
+    fun homeViewModel(directory: DirectoryState, login: LoginViewModel, profileViewModel: ProfileViewModel): HomeViewModel {
         return HomeViewModel(
             chatEngine,
             storeModule.credentialsStore(),

features/home/src/main/kotlin/app/dapk/st/home/HomeViewModel.kt

@@ -1,8 +1,8 @@
 package app.dapk.st.home
 
 import androidx.lifecycle.viewModelScope
-import app.dapk.st.directory.DirectorySideEffect
+import app.dapk.st.directory.state.DirectorySideEffect
-import app.dapk.st.directory.DirectoryViewModel
+import app.dapk.st.directory.state.DirectoryState
 import app.dapk.st.domain.StoreCleaner
 import app.dapk.st.engine.ChatEngine
 import app.dapk.st.home.HomeScreenState.*
@@ -21,7 +21,7 @@ import kotlinx.coroutines.launch
 class HomeViewModel(
     private val chatEngine: ChatEngine,
     private val credentialsProvider: CredentialsStore,
-    private val directoryViewModel: DirectoryViewModel,
+    private val directoryViewModel: DirectoryState,
     private val loginViewModel: LoginViewModel,
     private val profileViewModel: ProfileViewModel,
     private val cacheCleaner: StoreCleaner,

features/home/src/main/kotlin/app/dapk/st/home/MainActivity.kt

@@ -14,8 +14,9 @@ import androidx.lifecycle.lifecycleScope
 import app.dapk.st.core.DapkActivity
 import app.dapk.st.core.module
 import app.dapk.st.core.viewModel
+import app.dapk.st.core.state
 import app.dapk.st.directory.DirectoryModule
-import app.dapk.st.directory.DirectoryViewModel
+import app.dapk.st.directory.state.DirectoryState
 import app.dapk.st.login.LoginModule
 import app.dapk.st.profile.ProfileModule
 import kotlinx.coroutines.flow.launchIn
@@ -23,7 +24,7 @@ import kotlinx.coroutines.flow.onEach
 
 class MainActivity : DapkActivity() {
 
-    private val directoryViewModel: DirectoryViewModel by viewModel { module<DirectoryModule>().directoryViewModel() }
+    private val directoryViewModel: DirectoryState by state { module<DirectoryModule>().directoryViewModel() }
     private val loginViewModel by viewModel { module<LoginModule>().loginViewModel() }
     private val profileViewModel by viewModel { module<ProfileModule>().profileViewModel() }
     private val homeViewModel by viewModel { module<HomeModule>().homeViewModel(directoryViewModel, loginViewModel, profileViewModel) }