feat: character state management with ViewModel (Closes #23) (#60)

sharedUI/src/commonMain/kotlin/org/shahondin1624/App.kt

@@ -10,6 +10,7 @@ import androidx.compose.material.icons.filled.Settings
 import androidx.compose.material3.*
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.setValue
 import androidx.compose.runtime.rememberCoroutineScope
@@ -17,6 +18,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.unit.dp
+import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.navigation.NavHostController
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
@@ -28,12 +30,12 @@ import org.shahondin1624.lib.components.TestTags
 import org.shahondin1624.lib.components.UiConstants
 import org.shahondin1624.lib.components.charactermodel.CharacterSheetPage
 import org.shahondin1624.lib.components.settings.SettingsPage
-import org.shahondin1624.model.EXAMPLE_CHARACTER
 import org.shahondin1624.navigation.AppRoutes
 import org.shahondin1624.theme.AppTheme
 import org.shahondin1624.theme.LocalThemeIsDark
 import org.shahondin1624.theme.LocalWindowSizeClass
 import org.shahondin1624.theme.WindowSizeClass
+import org.shahondin1624.viewmodel.CharacterViewModel
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Preview
@@ -46,20 +48,21 @@ fun App(
 
         CompositionLocalProvider(LocalWindowSizeClass provides windowSizeClass) {
             val navController = rememberNavController()
-            AppContent(navController)
+            val characterViewModel: CharacterViewModel = viewModel { CharacterViewModel() }
+            AppContent(navController, characterViewModel)
         }
     }
 }
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-private fun AppContent(navController: NavHostController) {
+private fun AppContent(navController: NavHostController, characterViewModel: CharacterViewModel) {
     val windowSizeClass = LocalWindowSizeClass.current
 
     when (windowSizeClass) {
-        WindowSizeClass.Compact -> CompactNavigation(navController)
+        WindowSizeClass.Compact -> CompactNavigation(navController, characterViewModel)
-        WindowSizeClass.Medium -> MediumNavigation(navController)
+        WindowSizeClass.Medium -> MediumNavigation(navController, characterViewModel)
-        WindowSizeClass.Expanded -> ExpandedNavigation(navController)
+        WindowSizeClass.Expanded -> ExpandedNavigation(navController, characterViewModel)
     }
 }
 
@@ -91,7 +94,7 @@ private fun navigateTo(navController: NavHostController, route: String) {
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-private fun CompactNavigation(navController: NavHostController) {
+private fun CompactNavigation(navController: NavHostController, characterViewModel: CharacterViewModel) {
     val drawerState = rememberDrawerState(initialValue = DrawerValue.Closed)
     val scope = rememberCoroutineScope()
     val currentRoute = currentRoute(navController)
@@ -112,6 +115,7 @@ private fun CompactNavigation(navController: NavHostController) {
     ) {
         MainScaffold(
             navController = navController,
+            characterViewModel = characterViewModel,
             showMenuButton = true,
             onMenuClick = {
                 scope.launch {
@@ -127,7 +131,7 @@ private fun CompactNavigation(navController: NavHostController) {
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-private fun MediumNavigation(navController: NavHostController) {
+private fun MediumNavigation(navController: NavHostController, characterViewModel: CharacterViewModel) {
     val currentRoute = currentRoute(navController)
 
     Row(modifier = Modifier.fillMaxSize()) {
@@ -152,6 +156,7 @@ private fun MediumNavigation(navController: NavHostController) {
         }
         MainScaffold(
             navController = navController,
+            characterViewModel = characterViewModel,
             showMenuButton = false,
             onMenuClick = {},
             modifier = Modifier.weight(1f)
@@ -164,7 +169,7 @@ private fun MediumNavigation(navController: NavHostController) {
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
-private fun ExpandedNavigation(navController: NavHostController) {
+private fun ExpandedNavigation(navController: NavHostController, characterViewModel: CharacterViewModel) {
     val currentRoute = currentRoute(navController)
 
     PermanentNavigationDrawer(
@@ -179,6 +184,7 @@ private fun ExpandedNavigation(navController: NavHostController) {
     ) {
         MainScaffold(
             navController = navController,
+            characterViewModel = characterViewModel,
             showMenuButton = false,
             onMenuClick = {}
         )
@@ -225,25 +231,22 @@ private fun DrawerContent(
 
 /**
  * Main scaffold with top app bar and routed content area.
- *
- * @param navController the NavHostController for page routing
- * @param showMenuButton whether to show the hamburger menu icon (hidden when nav is persistent)
- * @param onMenuClick callback for hamburger menu button click
- * @param modifier optional modifier (e.g., weight in Row for Medium layout)
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 private fun MainScaffold(
     navController: NavHostController,
+    characterViewModel: CharacterViewModel,
     showMenuButton: Boolean,
     onMenuClick: () -> Unit,
     modifier: Modifier = Modifier
 ) {
     var isDark by LocalThemeIsDark.current
     val currentRoute = currentRoute(navController)
+    val character by characterViewModel.character.collectAsState()
 
     val topBarTitle = when (currentRoute) {
-        AppRoutes.CHARACTER_SHEET -> EXAMPLE_CHARACTER.characterData.name
+        AppRoutes.CHARACTER_SHEET -> character.characterData.name
         AppRoutes.SETTINGS -> "Settings"
         else -> "Shadowrun Character Sheet"
     }
@@ -301,7 +304,7 @@ private fun MainScaffold(
                     .padding(contentPadding)
             ) {
                 composable(AppRoutes.CHARACTER_SHEET) {
-                    CharacterSheetPage(EXAMPLE_CHARACTER, contentPadding)
+                    CharacterSheetPage(character, contentPadding)
                 }
                 composable(AppRoutes.SETTINGS) {
                     SettingsPage()

sharedUI/src/commonMain/kotlin/org/shahondin1624/viewmodel/CharacterViewModel.kt

@@ -0,0 +1,34 @@
+package org.shahondin1624.viewmodel
+
+import androidx.lifecycle.ViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import org.shahondin1624.model.EXAMPLE_CHARACTER
+import org.shahondin1624.model.charactermodel.ShadowrunCharacter
+
+/**
+ * ViewModel holding the current character as observable state.
+ * Foundation for all editing stories (6.2-6.6) and interactive features.
+ */
+class CharacterViewModel : ViewModel() {
+
+    private val _character = MutableStateFlow(EXAMPLE_CHARACTER)
+
+    /** Observable character state. */
+    val character: StateFlow<ShadowrunCharacter> = _character.asStateFlow()
+
+    /**
+     * Replace the current character entirely.
+     */
+    fun setCharacter(character: ShadowrunCharacter) {
+        _character.value = character
+    }
+
+    /**
+     * Update the character by applying a transformation function.
+     */
+    fun updateCharacter(transform: (ShadowrunCharacter) -> ShadowrunCharacter) {
+        _character.value = transform(_character.value)
+    }
+}