Avoid resolution of current page in DocumentScreen

app/src/main/java/org/fairscan/app/MainActivity.kt

@@ -62,7 +62,6 @@ import org.fairscan.app.ui.screens.about.createEmailWithImageIntent
 import org.fairscan.app.ui.screens.camera.CameraEvent
 import org.fairscan.app.ui.screens.camera.CameraScreen
 import org.fairscan.app.ui.screens.camera.CameraViewModel
-import org.fairscan.app.ui.screens.document.DocumentUiState
 import org.fairscan.app.ui.screens.export.ExportActions
 import org.fairscan.app.ui.screens.export.ExportEvent
 import org.fairscan.app.ui.screens.export.ExportResult
@@ -182,9 +181,9 @@ class MainActivity : ComponentActivity() {
                             uiState = documentUiState,
                             navigation = navigation,
                             onExportClick = onExportClick,
-                            onDeleteImage =  { id -> viewModel.deletePage(id) },
-                            onRotateImage = { id, clockwise -> viewModel.rotateImage(id, clockwise) },
-                            onToggleColorMode = { id -> viewModel.togglePageColorMode(id) },
+                            onDeleteImage =  { viewModel.deleteCurrentPage() },
+                            onRotateImage = { clockwise -> viewModel.rotateCurrentPage(clockwise) },
+                            onToggleColorMode = { viewModel.toggleCurrentPageColorMode() },
                             onPageReorder = { id, newIndex -> viewModel.movePage(id, newIndex) },
                             onPageSelected = viewModel::onPageSelected
                         )

app/src/main/java/org/fairscan/app/MainViewModel.kt

@@ -14,7 +14,6 @@
  */
 package org.fairscan.app
 
-import android.graphics.Bitmap
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import kotlinx.collections.immutable.persistentListOf
@@ -43,6 +42,7 @@ import org.fairscan.app.ui.screens.document.DocumentUiState
 import org.fairscan.app.ui.state.DocumentUiModel
 import org.fairscan.app.ui.state.PageThumbnail
 import org.fairscan.imageprocessing.ColorMode
+import java.lang.IllegalStateException
 import kotlin.math.min
 
 @OptIn(ExperimentalCoroutinesApi::class)
@@ -77,15 +77,16 @@ class MainViewModel(val imageRepository: ImageRepository, launchMode: LaunchMode
 
     private val _currentPageIndex = MutableStateFlow(0)
 
-    val currentPageUiState: Flow<CurrentPageUiState> =
+    private val currentPageUiState: Flow<CurrentPageUiState?> =
         combine(_currentPageIndex, _pages) { index, pages -> pages.getOrNull(index) }
             .mapLatest { page ->
                 page?.let {
                     CurrentPageUiState(
+                        page.id,
                         imageRepository.jpegBytes(it.key())?.toBitmap(),
                         page.colorMode
                     )
-                } ?: CurrentPageUiState()
+                }
             }
             .flowOn(Dispatchers.IO)
 
@@ -95,7 +96,7 @@ class MainViewModel(val imageRepository: ImageRepository, launchMode: LaunchMode
         }
             .stateIn(
                 viewModelScope, SharingStarted.Eagerly,
-                DocumentUiState(0, CurrentPageUiState(), DocumentUiModel())
+                DocumentUiState(0, null, DocumentUiModel())
             )
 
     fun onPageSelected(index: Int) {
@@ -116,10 +117,10 @@ class MainViewModel(val imageRepository: ImageRepository, launchMode: LaunchMode
         _navigationState.update { stack -> stack.navigateBack() }
     }
 
-    fun rotateImage(id: String, clockwise: Boolean) {
+    fun rotateCurrentPage(clockwise: Boolean) {
         viewModelScope.launch {
             val pages = withContext(Dispatchers.IO) {
-                imageRepository.rotate(id, clockwise)
+                imageRepository.rotate(currentPage().id, clockwise)
                 imageRepository.pages()
             }
             _pages.value = pages
@@ -136,10 +137,10 @@ class MainViewModel(val imageRepository: ImageRepository, launchMode: LaunchMode
         }
     }
 
-    fun deletePage(id: String) {
+    fun deleteCurrentPage() {
         viewModelScope.launch {
             val pages = withContext(Dispatchers.IO) {
-                imageRepository.delete(id)
+                imageRepository.delete(currentPage().id)
                 imageRepository.pages()
             }
 
@@ -153,14 +154,14 @@ class MainViewModel(val imageRepository: ImageRepository, launchMode: LaunchMode
         }
     }
 
-    fun togglePageColorMode(id: String) {
+    fun toggleCurrentPageColorMode() {
         viewModelScope.launch {
-            val currentColorMode = _pages.value.find { p -> p.id == id }?.colorMode
-            currentColorMode?.let {
+            val currentPage = currentPage()
+            currentPage.colorMode?.let {
                 val newColorMode =
                     if (it == ColorMode.COLOR) ColorMode.GRAYSCALE else ColorMode.COLOR
                 val pages = withContext(Dispatchers.IO) {
-                    imageRepository.setColorMode(id, newColorMode)
+                    imageRepository.setColorMode(currentPage.id, newColorMode)
                     imageRepository.pages()
                 }
                 _pages.value = pages
@@ -168,6 +169,13 @@ class MainViewModel(val imageRepository: ImageRepository, launchMode: LaunchMode
         }
     }
 
+    private fun currentPage(): ScanPage {
+        val index = _currentPageIndex.value
+        val pages = _pages.value
+        return pages.getOrNull(index) ?: throw IllegalStateException(
+            "No current page for index $index (${pages.size} pages)")
+    }
+
     fun startNewDocument() {
         _pages.value = persistentListOf()
         viewModelScope.launch {

app/src/main/java/org/fairscan/app/ui/screens/document/DocumentScreen.kt

@@ -86,9 +86,9 @@ fun DocumentScreen(
     uiState: DocumentUiState,
     navigation: Navigation,
     onExportClick: () -> Unit,
-    onDeleteImage: (String) -> Unit,
-    onRotateImage: (String, Boolean) -> Unit,
-    onToggleColorMode: (String) -> Unit,
+    onDeleteImage: () -> Unit,
+    onRotateImage: (Boolean) -> Unit,
+    onToggleColorMode: () -> Unit,
     onPageReorder: (String, Int) -> Unit,
     onPageSelected: (Int) -> Unit,
 ) {
@@ -130,7 +130,7 @@ fun DocumentScreen(
                 title = stringResource(R.string.delete_page),
                 message = stringResource(R.string.delete_page_warning),
                 showDialog = showDeletePageDialog
-            ) { onDeleteImage(document.pageId(currentPageIndex)) }
+            ) { onDeleteImage() }
         }
     }
 }
@@ -138,14 +138,13 @@ fun DocumentScreen(
 @Composable
 private fun DocumentPreview(
     uiState: DocumentUiState,
-    onDeleteImage: (String) -> Unit,
-    onRotateImage: (String, Boolean) -> Unit,
-    onToggleColorMode: (String) -> Unit,
+    onDeleteImage: () -> Unit,
+    onRotateImage: (Boolean) -> Unit,
+    onToggleColorMode: () -> Unit,
     modifier: Modifier,
 ) {
     val currentPageIndex = uiState.currentPageIndex
     val document = uiState.document
-    val imageId = document.pageId(currentPageIndex)
     Column (
         modifier = modifier
             .background(MaterialTheme.colorScheme.surfaceContainerLow)
@@ -153,10 +152,11 @@ private fun DocumentPreview(
         Box (
             modifier = Modifier.fillMaxSize()
         ) {
-            val bitmap = uiState.currentPage.bitmap
-            if (bitmap != null) {
+            val bitmap = uiState.currentPage?.bitmap
+            val pageId = uiState.currentPage?.id
+            if (bitmap != null && pageId != null) {
                 val imageBitmap = bitmap.asImageBitmap()
-                val zoomState = remember(imageId) {
+                val zoomState = remember(pageId) {
                     ZoomState(
                         contentSize = Size(bitmap.width.toFloat(), bitmap.height.toFloat())
                     )
@@ -175,20 +175,20 @@ private fun DocumentPreview(
                     )
                 }
             }
-            uiState.currentPage.colorMode?.let {
+            uiState.currentPage?.colorMode?.let {
                 ColorModeButton(
                     currentColorMode = it,
-                    onToggle = { onToggleColorMode(imageId) },
+                    onToggle = { onToggleColorMode() },
                     modifier = Modifier
                         .align(Alignment.BottomStart)
                         .padding(8.dp)
                 )
             }
-            RotationButtons(imageId, onRotateImage, Modifier.align(Alignment.BottomCenter))
+            RotationButtons(onRotateImage, Modifier.align(Alignment.BottomCenter))
             SecondaryActionButton(
                 Icons.Outlined.Delete,
                 contentDescription = stringResource(R.string.delete_page),
-                onClick = { onDeleteImage(imageId) },
+                onClick = { onDeleteImage() },
                 modifier = Modifier
                     .align(Alignment.BottomEnd)
                     .padding(8.dp)
@@ -210,8 +210,7 @@ private fun DocumentPreview(
 
 @Composable
 fun RotationButtons(
-    imageId: String,
-    onRotateImage: (String, Boolean) -> Unit,
+    onRotateImage: (Boolean) -> Unit,
     modifier: Modifier = Modifier
 ) {
     // RotateLeft on the left, RotateRight on the right: for both LTR and RTL languages
@@ -222,14 +221,14 @@ fun RotationButtons(
             SecondaryActionButton(
                 icon = Icons.Default.RotateLeft,
                 contentDescription = stringResource(R.string.rotate_left),
-                onClick = { onRotateImage(imageId, false) }
+                onClick = { onRotateImage(false) }
             )
             Spacer(Modifier.width(8.dp))
             @Suppress("DEPRECATION")
             SecondaryActionButton(
                 icon = Icons.Default.RotateRight,
                 contentDescription = stringResource(R.string.rotate_right),
-                onClick = { onRotateImage(imageId, true) }
+                onClick = { onRotateImage(true) }
             )
         }
     }
@@ -307,12 +306,12 @@ fun DocumentScreenPreview() {
             LocalContext.current
         )
         DocumentScreen(
-            uiState = DocumentUiState(1, CurrentPageUiState(image, COLOR), document),
+            uiState = DocumentUiState(1, CurrentPageUiState("123",image, COLOR), document),
             navigation = dummyNavigation(),
             onExportClick = {},
-            onDeleteImage = { _ -> },
-            onRotateImage = { _,_ -> },
-            onToggleColorMode = { _ -> },
+            onDeleteImage = { },
+            onRotateImage = { _ -> },
+            onToggleColorMode = { },
             onPageReorder = { _,_ -> },
             onPageSelected = { _ -> },
         )

app/src/main/java/org/fairscan/app/ui/screens/document/DocumentUiState.kt

@@ -20,11 +20,12 @@ import org.fairscan.imageprocessing.ColorMode
 
 data class DocumentUiState(
     val currentPageIndex: Int,
-    val currentPage: CurrentPageUiState,
+    val currentPage: CurrentPageUiState?,
     val document: DocumentUiModel,
 )
 
 data class CurrentPageUiState(
-    val bitmap: Bitmap? = null,
-    val colorMode: ColorMode? = null,
+    val id: String,
+    val bitmap: Bitmap?,
+    val colorMode: ColorMode?,
 )

app/src/main/java/org/fairscan/app/ui/state/DocumentUiModel.kt

@@ -25,9 +25,6 @@ data class DocumentUiModel(
     fun pageCount(): Int {
         return pages.size
     }
-    fun pageId(index: Int): String {
-        return pages[index].key.pageId
-    }
     fun isEmpty(): Boolean {
         return pages.isEmpty()
     }