Keep the loaded detail on screen while it re-reads (#196)

app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailViewModel.kt

@@ -48,9 +48,14 @@ class EventDetailViewModel @Inject constructor(
 ) : ViewModel() {
 
     private val _target = MutableStateFlow<Target?>(null)
-    // Bumped by retry() to re-run the load for the same target.
+    // Bumped by retry() and by re-opening the target already shown, to re-run
+    // the load without changing the target.
     private val _reload = MutableStateFlow(0)
 
+    // Last target whose content is already on screen; a re-read of it skips the
+    // Loading skeleton so the sheet doesn't blank out between two identical reads.
+    private var loadedTarget: Target? = null
+
     private val _deleteState = MutableStateFlow<DeleteUiState>(DeleteUiState.Idle)
     val deleteState: StateFlow<DeleteUiState> = _deleteState.asStateFlow()
 
@@ -58,11 +63,14 @@ class EventDetailViewModel @Inject constructor(
         combine(_target, _reload) { target, _ -> target }
             .flatMapLatest { target ->
                 if (target == null) {
+                    loadedTarget = null
                     flowOf<EventDetailUiState>(EventDetailUiState.Loading)
                 } else {
                     flow {
-                        emit(EventDetailUiState.Loading)
-                        emit(loadDetail(target))
+                        if (loadedTarget != target) emit(EventDetailUiState.Loading)
+                        val loaded = loadDetail(target)
+                        loadedTarget = target.takeIf { loaded is EventDetailUiState.Success }
+                        emit(loaded)
                     }
                 }
             }

app/src/test/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailViewModelTest.kt

@@ -32,6 +32,8 @@ import kotlin.time.Instant
 /**
  * Re-opening an occurrence must re-read it (#196): the view model outlives the
  * sheet, so an edit that changed no time would otherwise show the pre-save row.
+ * The re-read stays silent — the loaded content must not blink back to the
+ * skeleton on the way.
  */
 @OptIn(ExperimentalCoroutinesApi::class)
 class EventDetailViewModelTest {
@@ -72,19 +74,20 @@ class EventDetailViewModelTest {
         return EventDetailViewModel(repo, IcsExporter(ContextWrapper(null)), dispatcher)
     }
 
-    @Test
-    fun `re-opening the same occurrence re-reads it`(@TempDir tempDir: Path) = runTest(dispatcher) {
-        var stored: String? = null
-        val fake = FakeCalendarDataSource().apply {
+    private fun fakeSource(description: () -> String?) = FakeCalendarDataSource().apply {
         calendarsResult = listOf(
             CalendarSource(
                 id = 1L, displayName = "Cal", accountName = "acc@local", accountType = "LOCAL",
                 color = 0xFF112233.toInt(), isVisibleInSystem = true, canModifyContents = true,
             ),
         )
-            eventDetailResult = { detail(stored) }
+        eventDetailResult = { detail(description()) }
     }
-        val vm = viewModel(tempDir, fake)
+
+    @Test
+    fun `re-opening the same occurrence re-reads it`(@TempDir tempDir: Path) = runTest(dispatcher) {
+        var stored: String? = null
+        val vm = viewModel(tempDir, fakeSource { stored })
         val collector = launch(Job()) { vm.state.collect {} }
 
         vm.open(42L, beginMillis, endMillis)
@@ -100,4 +103,22 @@ class EventDetailViewModelTest {
 
         collector.cancel()
     }
+
+    @Test
+    fun `the re-read does not fall back to the skeleton`(@TempDir tempDir: Path) = runTest(dispatcher) {
+        val vm = viewModel(tempDir, fakeSource { null })
+        val seen = mutableListOf<EventDetailUiState>()
+        val collector = launch(Job()) { vm.state.collect { seen += it } }
+
+        vm.open(42L, beginMillis, endMillis)
+        advanceUntilIdle()
+        assertThat(vm.state.value).isInstanceOf(EventDetailUiState.Success::class.java)
+
+        seen.clear()
+        vm.open(42L, beginMillis, endMillis)
+        advanceUntilIdle()
+        assertThat(seen).doesNotContain(EventDetailUiState.Loading)
+
+        collector.cancel()
+    }
 }