feat(#106): category tap on dashboard navigates to inventory with filter

- Change Screen.ItemList from data object to data class with optional categoryId
- DashboardScreen: make CategoryCard clickable with onCategoryClick callback
- ItemListViewModel: read initial categoryId from SavedStateHandle
- BollwerkNavGraph: wire category click to navigate with categoryId
- Add test for initial category filter from navigation args

app/src/main/java/de/bollwerk/app/ui/dashboard/DashboardScreen.kt

@@ -34,6 +34,7 @@ import kotlin.math.roundToInt
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 internal fun DashboardScreen(
+    onCategoryClick: (Int) -> Unit = {},
     viewModel: DashboardViewModel = hiltViewModel()
 ) {
     val uiState by viewModel.uiState.collectAsStateWithLifecycle()
@@ -77,7 +78,10 @@ internal fun DashboardScreen(
                         )
                     }
                     items(uiState.categorySummaries) { summary ->
-                        CategoryCard(summary)
+                        CategoryCard(
+                            summary = summary,
+                            onClick = { onCategoryClick(summary.categoryId) }
+                        )
                     }
                 }
 
@@ -201,11 +205,13 @@ private fun WarningsSummaryCard(expiryCount: Int) {
     }
 }
 
+@OptIn(ExperimentalMaterial3Api::class)
 @Composable
-private fun CategoryCard(summary: CategorySummary) {
+private fun CategoryCard(summary: CategorySummary, onClick: () -> Unit) {
     val currencyFormat = NumberFormat.getCurrencyInstance(Locale.GERMANY)
 
     Card(
+        onClick = onClick,
         modifier = Modifier.fillMaxWidth()
     ) {
         Row(

app/src/main/java/de/bollwerk/app/ui/item/ItemListViewModel.kt

@@ -1,5 +1,6 @@
 package de.bollwerk.app.ui.item
 
+import androidx.lifecycle.SavedStateHandle
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
@@ -52,12 +53,14 @@ internal data class ItemListUiState(
 
 @HiltViewModel
 internal class ItemListViewModel @Inject constructor(
+    savedStateHandle: SavedStateHandle,
     private val itemRepository: ItemRepository,
     private val categoryRepository: CategoryRepository,
     private val locationRepository: LocationRepository
 ) : ViewModel() {
 
-    private val _filterState = MutableStateFlow(FilterState())
+    private val initialCategoryId: Int? = savedStateHandle.get<Int>("categoryId")
+    private val _filterState = MutableStateFlow(FilterState(categoryId = initialCategoryId))
     private val _uiState = MutableStateFlow(ItemListUiState())
     val uiState: StateFlow<ItemListUiState> = _uiState.asStateFlow()
 

app/src/main/java/de/bollwerk/app/ui/navigation/BollwerkNavGraph.kt

@@ -27,7 +27,11 @@ internal fun BollwerkNavGraph(
         modifier = modifier
     ) {
         composable<Screen.Dashboard> {
-            DashboardScreen()
+            DashboardScreen(
+                onCategoryClick = { categoryId ->
+                    navController.navigate(Screen.ItemList(categoryId = categoryId))
+                }
+            )
         }
 
         composable<Screen.ItemList> {

app/src/main/java/de/bollwerk/app/ui/navigation/Screen.kt

@@ -9,7 +9,7 @@ internal sealed interface Screen {
     data object Dashboard : Screen
 
     @Serializable
-    data object ItemList : Screen
+    data class ItemList(val categoryId: Int? = null) : Screen
 
     @Serializable
     data class ItemForm(val itemId: String? = null, val prefillJson: String? = null) : Screen

app/src/main/java/de/bollwerk/app/ui/navigation/TopLevelDestination.kt

@@ -26,7 +26,7 @@ internal enum class TopLevelDestination(
         label = "Overview"
     ),
     INVENTORY(
-        route = Screen.ItemList,
+        route = Screen.ItemList(),
         selectedIcon = Icons.Filled.Warehouse,
         unselectedIcon = Icons.Outlined.Warehouse,
         label = "Storage"

app/src/test/java/de/bollwerk/app/ui/item/ItemListViewModelTest.kt

@@ -1,5 +1,6 @@
 package de.bollwerk.app.ui.item
 
+import androidx.lifecycle.SavedStateHandle
 import de.bollwerk.app.data.db.entity.CategoryEntity
 import de.bollwerk.app.data.db.entity.ItemEntity
 import de.bollwerk.app.data.db.entity.LocationEntity
@@ -40,6 +41,7 @@ class ItemListViewModelTest {
         fakeCategoryRepository = FakeCategoryRepository()
         fakeLocationRepository = FakeLocationRepository()
         viewModel = ItemListViewModel(
+            savedStateHandle = SavedStateHandle(),
             itemRepository = fakeItemRepository,
             categoryRepository = fakeCategoryRepository,
             locationRepository = fakeLocationRepository
@@ -543,6 +545,40 @@ class ItemListViewModelTest {
         assertEquals(2, viewModel.uiState.value.groupedItems.values.flatten().size)
     }
 
+    @Test
+    fun test_init_withCategoryIdFromNavigation_filterIsPreApplied() = runTest(testDispatcher) {
+        // Given
+        val vmWithCategory = ItemListViewModel(
+            savedStateHandle = SavedStateHandle(mapOf("categoryId" to 2)),
+            itemRepository = fakeItemRepository,
+            categoryRepository = fakeCategoryRepository,
+            locationRepository = fakeLocationRepository
+        )
+        fakeCategoryRepository.emit(
+            listOf(
+                CategoryEntity(id = 1, name = "Lebensmittel"),
+                CategoryEntity(id = 2, name = "Hygiene")
+            )
+        )
+        fakeLocationRepository.emit(listOf(LocationEntity(id = 1, name = "Keller")))
+        fakeItemRepository.emit(
+            listOf(
+                buildItemEntity(id = "a", name = "Reis", categoryId = 1),
+                buildItemEntity(id = "b", name = "Seife", categoryId = 2)
+            )
+        )
+
+        // When
+        advanceUntilIdle()
+
+        // Then
+        val state = vmWithCategory.uiState.value
+        assertEquals(2, state.selectedCategoryId)
+        val allItems = state.groupedItems.values.flatten()
+        assertEquals(1, allItems.size)
+        assertEquals("Seife", allItems.first().name)
+    }
+
     // endregion
 }
 

app/src/test/java/de/bollwerk/app/ui/navigation/ScreenTest.kt

@@ -9,10 +9,10 @@ class ScreenTest {
     @Test
     fun test_itemListRoute_isSingleton() {
         // Given & When
-        val route = Screen.ItemList
+        val route = Screen.ItemList()
 
         // Then
-        assertEquals(Screen.ItemList, route)
+        assertEquals(Screen.ItemList(), route)
     }
 
     @Test
@@ -73,4 +73,25 @@ class ScreenTest {
         // Then
         assert(route1 != route2)
     }
+
+    @Test
+    fun test_itemListRoute_withoutCategoryId_hasNullCategoryId() {
+        // Given & When
+        val route = Screen.ItemList()
+
+        // Then
+        assertNull(route.categoryId)
+    }
+
+    @Test
+    fun test_itemListRoute_withCategoryId_hasCorrectCategoryId() {
+        // Given
+        val expectedId = 5
+
+        // When
+        val route = Screen.ItemList(categoryId = expectedId)
+
+        // Then
+        assertEquals(expectedId, route.categoryId)
+    }
 }