Add drag and tap gestures to select images

app/src/main/java/fr/free/nrw/commons/customselector/ui/screens/CustomSelectorEvent.kt

@@ -2,5 +2,6 @@ package fr.free.nrw.commons.customselector.ui.screens
 
 interface CustomSelectorEvent {
     data class OnFolderClick(val bucketId: Long): CustomSelectorEvent
-    data class OnImageSelect(val imageId: Long): CustomSelectorEvent
+    data class OnImageSelection(val imageId: Long): CustomSelectorEvent
+    data class OnDragImageSelection(val imageIds: Set<Long>): CustomSelectorEvent
 }

app/src/main/java/fr/free/nrw/commons/customselector/ui/screens/CustomSelectorState.kt

@@ -5,5 +5,9 @@ import fr.free.nrw.commons.customselector.model.Image
 data class CustomSelectorState(
     val isLoading: Boolean = false,
     val folders: List<Folder> = emptyList(),
-    val filteredImages: List<Image> = emptyList()
-)
+    val filteredImages: List<Image> = emptyList(),
+    val selectedImageIds: Set<Long> = emptySet()
+) {
+    val inSelectionMode: Boolean
+        get() = selectedImageIds.isNotEmpty()
+}

app/src/main/java/fr/free/nrw/commons/customselector/ui/screens/CustomSelectorViewModel.kt

@@ -1,6 +1,5 @@
 package fr.free.nrw.commons.customselector.ui.screens
 
-import androidx.compose.runtime.mutableStateListOf
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import fr.free.nrw.commons.customselector.data.MediaReader
@@ -17,9 +16,6 @@ class CustomSelectorViewModel(private val mediaReader: MediaReader): ViewModel()
 
     private val foldersMap = mutableMapOf<Long, MutableList<Image>>()
 
-    private var _selectedImageIds = mutableStateListOf<Long>()
-    val selectedImageIds = _selectedImageIds
-
     init {
         _uiState.update { it.copy(isLoading = true) }
         viewModelScope.launch {
@@ -46,14 +42,21 @@ class CustomSelectorViewModel(private val mediaReader: MediaReader): ViewModel()
                 }
             }
 
-            is CustomSelectorEvent.OnImageSelect -> {
-                if(_selectedImageIds.contains(e.imageId)) {
-                    _selectedImageIds.remove(e.imageId)
-                } else {
-                    _selectedImageIds.add(e.imageId)
+            is CustomSelectorEvent.OnImageSelection -> {
+                _uiState.update { state ->
+                    val updatedSelectedIds = if (state.selectedImageIds.contains(e.imageId)) {
+                        state.selectedImageIds - e.imageId // Remove if already selected
+                    } else{
+                        state.selectedImageIds + e.imageId // Add if not selected
+                    }
+                    state.copy(selectedImageIds = updatedSelectedIds)
                 }
             }
 
+            is CustomSelectorEvent.OnDragImageSelection-> {
+                _uiState.update { it.copy(selectedImageIds = e.imageIds) }
+            }
+
             else -> {}
         }
     }

app/src/main/java/fr/free/nrw/commons/customselector/ui/screens/ImagesPane.kt

@@ -1,5 +1,8 @@
 package fr.free.nrw.commons.customselector.ui.screens
 
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.animation.slideInVertically
+import androidx.compose.animation.slideOutVertically
 import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
@@ -26,6 +29,7 @@ import androidx.compose.material.icons.rounded.Check
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Surface
 import androidx.compose.material3.adaptive.WindowAdaptiveInfo
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
@@ -41,30 +45,42 @@ import androidx.compose.ui.graphics.painter.Painter
 import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.round
 import androidx.compose.ui.unit.toIntRect
 import androidx.window.core.layout.WindowWidthSizeClass
 import coil.compose.rememberAsyncImagePainter
+import fr.free.nrw.commons.R
 import fr.free.nrw.commons.customselector.model.Image
+import fr.free.nrw.commons.customselector.ui.components.CustomSelectorBottomBar
 import fr.free.nrw.commons.customselector.ui.components.CustomSelectorTopBar
 import fr.free.nrw.commons.customselector.ui.components.PartialStorageAccessDialog
+import fr.free.nrw.commons.ui.theme.CommonsTheme
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.isActive
 
 @OptIn(ExperimentalFoundationApi::class)
 @Composable
 fun ImagesPane(
+    uiState: CustomSelectorState,
     selectedFolder: Folder,
-    selectedImages: List<Long>,
-    imageList: List<Image>,
-    onNavigateBack: ()-> Unit,
-    onToggleImageSelection: (Long) -> Unit,
-    adaptiveInfo: WindowAdaptiveInfo
+    selectedImages: () -> Set<Long>,
+    onNavigateBack: () -> Unit,
+    onEvent: (CustomSelectorEvent) -> Unit,
+    adaptiveInfo: WindowAdaptiveInfo,
+    hasPartialAccess: Boolean = false
 ) {
-    val inSelectionMode by remember { derivedStateOf { selectedImages.isNotEmpty() } }
+//    val inSelectionMode by remember { derivedStateOf { selectedImages().isNotEmpty() } }
     val lazyGridState = rememberLazyGridState()
     var autoScrollSpeed by remember { mutableFloatStateOf(0f) }
+    val isCompatWidth by remember(adaptiveInfo.windowSizeClass) {
+        derivedStateOf {
+            adaptiveInfo.windowSizeClass
+                .windowWidthSizeClass == WindowWidthSizeClass.COMPACT
+        }
+    }
 
     LaunchedEffect(autoScrollSpeed) {
         if (autoScrollSpeed != 0f) {
@@ -81,17 +97,35 @@ fun ImagesPane(
                 primaryText = selectedFolder.bucketName,
                 secondaryText = "${selectedFolder.itemsCount} images",
                 onNavigateBack = onNavigateBack,
-                showNavigationIcon = adaptiveInfo.windowSizeClass
-                    .windowWidthSizeClass == WindowWidthSizeClass.COMPACT
+                showNavigationIcon = isCompatWidth,
+                showAlertIcon = selectedImages().size > 20,
+                selectionCount = selectedImages().size,
+                showSelectionCount = uiState.inSelectionMode
             )
+        },
+        bottomBar = {
+            AnimatedVisibility(
+                visible = uiState.inSelectionMode && isCompatWidth,
+                enter = slideInVertically(initialOffsetY = { it }),
+                exit = slideOutVertically(targetOffsetY = { it })
+            ) {
+                Surface(tonalElevation = 1.dp) {
+                    CustomSelectorBottomBar(
+                        onPrimaryAction = { /*TODO("Implement action to upload selected images")*/ },
+                        onSecondaryAction = { /*TODO("Implement action to mark/unmark as not for upload")*/ },
+                        modifier = Modifier.padding(horizontal = 16.dp, vertical = 8.dp)
+                    )
+                }
+            }
         }
-    ) { innerPadding->
+    ) { innerPadding ->
         Column(modifier = Modifier.padding(innerPadding)) {
-            PartialStorageAccessDialog(
-                isVisible = true,
-                onManage = { /*TODO*/ },
-                modifier = Modifier.padding(8.dp)
-            )
+            if (hasPartialAccess) {
+                PartialStorageAccessDialog(
+                    onManageAction = { /*TODO("Request permission[READ_MEDIA_IMAGES]")*/ },
+                    modifier = Modifier.padding(8.dp)
+                )
+            }
 
             LazyVerticalGrid(
                 columns = GridCells.Adaptive(116.dp),
@@ -99,9 +133,11 @@ fun ImagesPane(
                     .fillMaxSize()
                     .imageGridDragHandler(
                         gridState = lazyGridState,
-                        imageList = imageList,
-                        selectedImageIds = { selectedImages },
-                        onImageSelect = { onToggleImageSelection(it) },
+                        imageList = uiState.filteredImages,
+                        selectedImageIds = selectedImages,
+                        setSelectedImageIds = {
+                            onEvent(CustomSelectorEvent.OnDragImageSelection(it))
+                        },
                         autoScrollThreshold = with(LocalDensity.current) { 40.dp.toPx() },
                         setAutoScrollSpeed = { autoScrollSpeed = it }
                     ),
@@ -110,23 +146,23 @@ fun ImagesPane(
                 horizontalArrangement = Arrangement.spacedBy(8.dp),
                 contentPadding = PaddingValues(8.dp)
             ) {
-                items(imageList, key = { it.id }) { image->
+                items(uiState.filteredImages, key = { it.id }) { image ->
                     val isSelected by remember {
-                        derivedStateOf { selectedImages.contains(image.id) }
+                        derivedStateOf { selectedImages().contains(image.id) }
                     }
 
                     ImageItem(
                         imagePainter = rememberAsyncImagePainter(model = image.uri),
                         isSelected = isSelected,
-                        inSelectionMode = inSelectionMode,
+                        inSelectionMode = uiState.inSelectionMode,
                         modifier = Modifier.combinedClickable(
                             onClick = {
-                                if(inSelectionMode) {
-                                    onToggleImageSelection(image.id)
+                                if (uiState.inSelectionMode) {
+                                    onEvent(CustomSelectorEvent.OnImageSelection(image.id))
                                 }
                             },
                             onLongClick = {
-                                onToggleImageSelection(image.id)
+                                onEvent(CustomSelectorEvent.OnImageSelection(image.id))
                             }
                         )
                     )
@@ -153,8 +189,8 @@ fun ImageItem(
             contentScale = ContentScale.Crop
         )
 
-        if(inSelectionMode) {
-            if(isSelected) {
+        if (inSelectionMode) {
+            if (isSelected) {
                 Icon(
                     imageVector = Icons.Rounded.Check,
                     contentDescription = null,
@@ -181,14 +217,44 @@ fun ImageItem(
     }
 }
 
+@Preview
+@Composable
+private fun ImageItemPreview() {
+    CommonsTheme {
+        Surface {
+            ImageItem(
+                imagePainter = painterResource(id = R.drawable.image_placeholder_96),
+                isSelected = false,
+                inSelectionMode = true,
+                modifier = Modifier
+                    .padding(16.dp)
+                    .size(116.dp)
+            )
+        }
+    }
+}
+
+/**
+ * A modifier that handles drag gestures on an image grid to allow for selecting multiple images.
+ *
+ * This modifier detects drag gestures and updates the selected images based on the drag position.
+ * It also handles auto-scrolling when the drag reaches the edges of the grid.
+ *
+ * @param gridState The state of the lazy grid.
+ * @param imageList The list of images displayed in the grid.
+ * @param selectedImageIds A function that returns the currently selected image IDs.
+ * @param autoScrollThreshold The distance from the edge of the grid at which auto-scrolling should start.
+ * @param setSelectedImageIds A callback function that is invoked when the selected images change.
+ * @param setAutoScrollSpeed A callback function that is invoked to set the auto-scroll speed.
+ */
 fun Modifier.imageGridDragHandler(
     gridState: LazyGridState,
     imageList: List<Image>,
-    selectedImageIds:()-> List<Long>,
+    selectedImageIds: () -> Set<Long>,
     autoScrollThreshold: Float,
-    onImageSelect: (Long) -> Unit = { },
-    setAutoScrollSpeed: (Float) -> Unit = { },
-) = pointerInput(autoScrollThreshold, setAutoScrollSpeed, onImageSelect) {
+    setSelectedImageIds: (Set<Long>) -> Unit,
+    setAutoScrollSpeed: (Float) -> Unit,
+) = pointerInput(autoScrollThreshold, setAutoScrollSpeed, setSelectedImageIds, imageList) {
 
     fun imageIndexAtOffset(hitPoint: Offset): Int? =
         gridState.layoutInfo.visibleItemsInfo.find { itemInfo ->
@@ -200,33 +266,56 @@ fun Modifier.imageGridDragHandler(
     var isSelecting = true
 
     detectDragGestures(
-        onDragStart = { offset->
+        onDragStart = { offset ->
             imageIndexAtOffset(offset)?.let {
                 val imageId = imageList[it].id
-                if(!selectedImageIds().contains(imageId)) {
-                    dragStartIndex = it
-                    currentDragIndex = it
-                    onImageSelect(imageList[it].id)
+                dragStartIndex = it
+                currentDragIndex = it
+
+                if (!selectedImageIds().contains(imageId)) {
+                    isSelecting = true
+                    setSelectedImageIds(selectedImageIds().plus(imageId))
+                } else {
+                    isSelecting = false
+                    setSelectedImageIds(selectedImageIds().minus(imageId))
                 }
             }
         },
         onDragEnd = { setAutoScrollSpeed(0f); dragStartIndex = null },
         onDragCancel = { setAutoScrollSpeed(0f); dragStartIndex = null },
-        onDrag = { change, _->
-            dragStartIndex?.let { startIndex->
-                currentDragIndex?.let { endIndex->
-                    val start = minOf(startIndex, endIndex)
-                    val end = maxOf(start, endIndex)
+        onDrag = { change, _ ->
+            dragStartIndex?.let { startIndex ->
+                val distFromBottom = gridState.layoutInfo.viewportSize.height - change.position.y
+                val distFromTop = change.position.y
+                setAutoScrollSpeed(
+                    when {
+                        distFromBottom < autoScrollThreshold -> autoScrollThreshold - distFromBottom
+                        distFromTop < autoScrollThreshold -> -(autoScrollThreshold - distFromTop)
+                        else -> 0f
+                    }
+                )
 
-                    (start..end).forEach { index->
-                        val imageId = imageList[index].id
-                        val ifContains = selectedImageIds().contains(imageId)
-                        if (isSelecting && !selectedImageIds().contains(imageId)) {
-                            println("Selecting...")
-                            println("contains: $ifContains")
-                            onImageSelect(imageId)
-                        } else if (!isSelecting && selectedImageIds().contains(imageId)) {
-                            onImageSelect(imageId)
+                currentDragIndex?.let { currentIndex ->
+                    imageIndexAtOffset(change.position)?.let { pointerIndex ->
+                        if (currentIndex != pointerIndex) {
+                            if (isSelecting) {
+                                setSelectedImageIds(
+                                    selectedImageIds().minus(
+                                        imageList.getImageIdsInRange(startIndex, currentIndex)
+                                    ).plus(
+                                        imageList.getImageIdsInRange(startIndex, pointerIndex)
+                                    )
+                                )
+                            } else {
+                                setSelectedImageIds(
+                                    selectedImageIds().plus(
+                                        imageList.getImageIdsInRange(currentIndex, pointerIndex)
+                                    ).minus(
+                                        imageList.getImageIdsInRange(startIndex, pointerIndex)
+                                    )
+                                )
+                            }
+                            currentDragIndex = pointerIndex
                         }
                     }
                 }
@@ -235,26 +324,23 @@ fun Modifier.imageGridDragHandler(
     )
 }
 
-private fun Set<Int>.addUpTo(
-    initialKey: Int?,
-    pointerKey: Int?
-): Set<Int> {
-    return if(initialKey == null || pointerKey == null) {
-        this
+/**
+ * Calculates a set of image IDs within a given range of indices in a list of images.
+ *
+ * @param initialKey The starting index of the range.
+ * @param pointerKey The ending index of the range.
+ * @return A set of image IDs within the specified range.
+ */
+fun List<Image>.getImageIdsInRange(initialKey: Int, pointerKey: Int): Set<Long> {
+    val setOfKeys = mutableSetOf<Long>()
+    if (initialKey < pointerKey) {
+        (initialKey..pointerKey).forEach {
+            setOfKeys.add(this[it].id)
+        }
     } else {
-        this.plus(initialKey..pointerKey)
-            .plus(pointerKey..initialKey)
-    }
-}
-
-private fun Set<Int>.removeUpTo(
-    initialKey: Int?,
-    previousPointerKey: Int?
-): Set<Int> {
-    return if(initialKey == null || previousPointerKey == null) {
-        this
-    } else {
-        this.minus(initialKey..previousPointerKey)
-            .minus(previousPointerKey..initialKey)
+        (pointerKey..initialKey).forEach {
+            setOfKeys.add(this[it].id)
+        }
     }
+    return setOfKeys
 }