refactor: Introduce nested navigation graphs and share ViewModels

This commit refactors the navigation structure to use nested navigation graphs, improving organization and state management. It also modifies how ViewModels are scoped to share instances between screens within the same navigation graph, preserving UI state across tabs.

### Key Changes:

*   **Nested Navigation Graphs (`AppNavigation.kt`, `AppRoute.kt`):**
    *   Introduced a `MainGraph` to encapsulate the primary application screens (`ProjectAnalyzer`, `StorageAnalyzer`) and a `SplashGraph` for the initial launch flow (`Splash`, `Onboarding`).
    *   This groups related destinations, simplifying navigation logic and making the flow more robust.

*   **ViewModel Sharing (`ProjectAnalyzerScreen.kt`, `StorageAnalyzerScreen.kt`):**
    *   `ProjectAnalyzerViewModel` and `StorageAnalyzerViewModel` are now scoped to the `MainGraph`.
    *   This is achieved by passing the `NavBackStackEntry` of the parent graph (`MainGraph`) to the `koinViewModel` factory.
    *   As a result, the ViewModels are shared across the composables within the `MainGraph`, preserving the state of each screen when switching between the "Project" and "Storage" tabs.

*   **Navigation Logic Cleanup (`AppNavigation.kt`):**
    *   Removed manual `popUpTo` logic with `findStartDestination()`. The new navigation structure with `launchSingleTop = true` and `restoreState = true` handles this more cleanly.

*   **UI Enhancements (`TopAppBar.kt`):**
    *   The `TopAppBar` now supports an optional back navigation icon, which can be enabled by providing a `navigationOnClick` lambda.

Author: Coding-Meet

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/components/TopAppBar.kt

@@ -4,9 +4,12 @@ import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.RowScope
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.width
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
 import androidx.compose.material3.CenterAlignedTopAppBar
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.material3.TopAppBarDefaults
@@ -22,9 +25,20 @@ import androidx.compose.ui.unit.dp
 fun TopAppBar(
     title: String,
     icon: ImageVector,
+    navigationOnClick: (() -> Unit)? = null,
     actions: @Composable RowScope.() -> Unit = {}
 ) {
     CenterAlignedTopAppBar(
+        navigationIcon = {
+            navigationOnClick?.let {
+                IconButton(onClick = it) {
+                    Icon(
+                        imageVector = Icons.AutoMirrored.Filled.ArrowBack,
+                        contentDescription = "Back"
+                    )
+                }
+            }
+        },
         title = {
             Row(verticalAlignment = Alignment.CenterVertically) {
                 Icon(
@@ -42,7 +56,8 @@ fun TopAppBar(
         colors = TopAppBarDefaults.centerAlignedTopAppBarColors(
             containerColor = MaterialTheme.colorScheme.primary,
             titleContentColor = MaterialTheme.colorScheme.onPrimary,
-            actionIconContentColor = MaterialTheme.colorScheme.onPrimary
+            actionIconContentColor = MaterialTheme.colorScheme.onPrimary,
+            navigationIconContentColor = MaterialTheme.colorScheme.onPrimary
         ),
         actions = actions
     )

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/navigation/AppNavigation.kt

@@ -14,10 +14,10 @@ import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
-import androidx.navigation.NavGraph.Companion.findStartDestination
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.currentBackStackEntryAsState
+import androidx.navigation.compose.navigation
 import androidx.navigation.compose.rememberNavController
 import com.meet.dev.analyzer.presentation.navigation.navigation_bar.NavigationItem
 import com.meet.dev.analyzer.presentation.navigation.navigation_bar.NavigationRailLayout
@@ -57,29 +57,14 @@ fun AppNavigation(
             AnimatedVisibility(
                 visible = currentNavigationItem != null,
                 modifier = Modifier.background(MaterialTheme.colorScheme.surface),
-                enter = slideInHorizontally(
-                    // Slide in from the left
-                    initialOffsetX = { fullWidth -> -fullWidth }
-                ),
-                exit = slideOutHorizontally(
-                    // Slide out to the right
-                    targetOffsetX = { fullWidth -> -fullWidth }
-                ),
+                enter = slideInHorizontally { -it },
+                exit = slideOutHorizontally { it },
             ) {
                 NavigationRailLayout(
                     currentNavigationItem = currentNavigationItem,
                     onNavigate = {
                         navController.navigate(it.appRoute) {
-                            // Pop up to the start destination of the graph to
-                            // avoid building up a large stack of destinations
-                            // on the back stack as users select items
-                            popUpTo(navController.graph.findStartDestination().id) {
-                                saveState = true
-                            }
-                            // Avoid multiple copies of the same destination when
-                            // re-selecting the same item
                             launchSingleTop = true
-                            // Restore state when re-selecting a previously selected item
                             restoreState = true
                         }
                     },
@@ -92,36 +77,49 @@ fun AppNavigation(
     ) {
         NavHost(
             navController = navController,
-            startDestination = AppRoute.Splash
+            startDestination = AppRoute.SplashGraph
         ) {
-            composable<AppRoute.Splash> {
-                SplashScreen(
-                    onSplashFinished = { appRoute ->
-                        navController.navigate(appRoute) {
-                            popUpTo(AppRoute.Splash) {
-                                inclusive = true
+            // Splash + Onboarding Graph
+            navigation<AppRoute.SplashGraph>(
+                startDestination = AppRoute.Splash
+            ) {
+                composable<AppRoute.Splash> {
+                    SplashScreen(
+                        onSplashFinished = { route ->
+                            navController.navigate(route) {
+                                popUpTo(AppRoute.SplashGraph) { inclusive = true }
                             }
                         }
-                    }
-                )
-            }
-            composable<AppRoute.Onboarding> {
-                OnboardingScreen(
-                    onComplete = {
-                        navController.navigate(AppRoute.ProjectAnalyzer) {
-                            popUpTo(AppRoute.Onboarding) {
-                                inclusive = true
+                    )
+                }
+                composable<AppRoute.Onboarding> {
+                    OnboardingScreen(
+                        onComplete = {
+                            navController.navigate(AppRoute.MainGraph) {
+                                popUpTo(AppRoute.SplashGraph) { inclusive = true }
                             }
                         }
-                    }
-                )
-            }
-            composable<AppRoute.ProjectAnalyzer> {
-                ProjectAnalyzerScreen()
+                    )
+                }
             }
-            composable<AppRoute.StorageAnalyzer> {
-                StorageAnalyzerScreen()
+
+            // Main Graph (tabs)
+            navigation<AppRoute.MainGraph>(
+                startDestination = AppRoute.ProjectAnalyzer
+            ) {
+                composable<AppRoute.ProjectAnalyzer> {
+                    val parentEntry = remember(navController) {
+                        navController.getBackStackEntry(AppRoute.MainGraph)
+                    }
+                    ProjectAnalyzerScreen(parentEntry = parentEntry)
+                }
+                composable<AppRoute.StorageAnalyzer> {
+                    val parentEntry = remember(navController) {
+                        navController.getBackStackEntry(AppRoute.MainGraph)
+                    }
+                    StorageAnalyzerScreen(parentEntry = parentEntry)
+                }
             }
         }
     }
-}
+}

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/navigation/AppRoute.kt

@@ -4,12 +4,17 @@ import kotlinx.serialization.Serializable
 
 sealed interface AppRoute {
 
+    @Serializable
+    data object SplashGraph : AppRoute
     @Serializable
     data object Splash : AppRoute
 
     @Serializable
     data object Onboarding : AppRoute
 
+    @Serializable
+    data object MainGraph : AppRoute
+
     @Serializable
     data object ProjectAnalyzer : AppRoute
 

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/screen/project/ProjectAnalyzerScreen.kt

@@ -22,6 +22,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.input.pointer.PointerIcon
 import androidx.compose.ui.input.pointer.pointerHoverIcon
 import androidx.compose.ui.unit.dp
+import androidx.navigation.NavBackStackEntry
 import com.meet.dev.analyzer.core.utility.ProjectScreenTabs
 import com.meet.dev.analyzer.presentation.components.EmptyStateCardLayout
 import com.meet.dev.analyzer.presentation.components.TabLayout
@@ -43,8 +44,12 @@ import java.awt.Cursor
 import java.io.File
 
 @Composable
-fun ProjectAnalyzerScreen() {
-    val viewModel = koinViewModel<ProjectAnalyzerViewModel>()
+fun ProjectAnalyzerScreen(
+    parentEntry: NavBackStackEntry
+) {
+    val viewModel = koinViewModel<ProjectAnalyzerViewModel>(
+        viewModelStoreOwner = parentEntry
+    )
     val uiState by viewModel.uiState.collectAsState()
     val coroutineScope = rememberCoroutineScope()
 

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/screen/project/ProjectAnalyzerViewModel.kt

@@ -26,6 +26,10 @@ class ProjectAnalyzerViewModel(
     private val _uiState = MutableStateFlow(ProjectAnalyzerUiState())
     val uiState = _uiState.asStateFlow()
 
+    init {
+        AppLogger.d(TAG) { "ViewModel initialized" }
+    }
+
     fun handleIntent(intent: ProjectAnalyzerIntent) {
         when (intent) {
             is ProjectAnalyzerIntent.SelectProject -> {

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/screen/splash/SplashViewModel.kt

@@ -44,7 +44,7 @@ class SplashViewModel(
             delay(2000)
             val isOnboardingDone = appUiState.value
             val appRoute =
-                if (isOnboardingDone) AppRoute.ProjectAnalyzer else AppRoute.Onboarding
+                if (isOnboardingDone) AppRoute.MainGraph else AppRoute.Onboarding
             _effect.emit(SplashEffect.OnSplashCompleted(appRoute))
         }
     }

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/screen/storage/StorageAnalyzerScreen.kt

@@ -27,6 +27,7 @@ import androidx.compose.ui.input.pointer.pointerHoverIcon
 import androidx.compose.ui.platform.ClipEntry
 import androidx.compose.ui.platform.LocalClipboard
 import androidx.compose.ui.unit.dp
+import androidx.navigation.NavBackStackEntry
 import com.meet.dev.analyzer.core.utility.StorageAnalyzerTabs
 import com.meet.dev.analyzer.presentation.components.ErrorLayout
 import com.meet.dev.analyzer.presentation.components.ProgressStatusLayout
@@ -47,8 +48,12 @@ import java.awt.Cursor
 import java.awt.datatransfer.StringSelection
 
 @Composable
-fun StorageAnalyzerScreen() {
-    val viewModel = koinViewModel<StorageAnalyzerViewModel>()
+fun StorageAnalyzerScreen(
+    parentEntry: NavBackStackEntry,
+) {
+    val viewModel = koinViewModel<StorageAnalyzerViewModel>(
+        viewModelStoreOwner = parentEntry
+    )
     val uiState by viewModel.uiState.collectAsState()
 
 //    DataClassTOJson(

composeApp/src/jvmMain/kotlin/com/meet/dev/analyzer/presentation/screen/storage/StorageAnalyzerViewModel.kt

@@ -42,6 +42,7 @@ class StorageAnalyzerViewModel(
     private var loadAllJob: Job? = null
 
     init {
+        AppLogger.d(TAG) { "ViewModel initialized" }
         handleIntent(StorageAnalyzerIntent.LoadAllData)
     }