feat(card-browser): snackbar on sort type change

Prep for issue 17732

Assisted-by: Claude Ops 4.7

Author: david-allison

AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserFragment.kt

@@ -1009,6 +1009,22 @@ class CardBrowserFragment :
             sortChip?.scaleY = if (reverse == false || reverse == null) 1.0f else -1.0f
         }
 
+        /** Displays a snackbar: Sort by Card Type · A-Z*/
+        fun onSortTypeChanged(notification: SortChangeNotification) {
+            val (title, subtitle) =
+                when (notification) {
+                    is SortChangeNotification.NoOrdering ->
+                        getString(R.string.card_browser_order_no_sorting_title) to null
+                    is SortChangeNotification.CollectionOrdering -> {
+                        val subtitleRes = notification.type.humanReadableExplanation(descending = notification.reverse)
+                        getString(R.string.card_browser_order_snackbar_sort_by, notification.columnLabel) to
+                            subtitleRes?.let(::getString)
+                    }
+                }
+            val text = if (subtitle != null) "$title · $subtitle" else title
+            showSnackbar(text, Snackbar.LENGTH_SHORT)
+        }
+
         activityViewModel.flowOfReverseDirection.launchCollectionInLifecycleScope(::reverseDirectionChanged)
         activityViewModel.flowOfIsTruncated.launchCollectionInLifecycleScope(::onIsTruncatedChanged)
         activityViewModel.flowOfSelectedRows.launchCollectionInLifecycleScope(::onSelectedRowsChanged)
@@ -1028,6 +1044,7 @@ class CardBrowserFragment :
         searchViewModel.submittedSearchFlow.filterNotNull().launchCollectionInLifecycleScope(::onSearchSubmitted)
         searchViewModel.userMessageFlow.filterNotNull().launchCollectionInLifecycleScope(::onUserMessage)
         activityViewModel.searchRequestFlow.launchCollectionInLifecycleScope(::onSearchRequestUpdated)
+        activityViewModel.flowOfSortTypeChanged.launchCollectionInLifecycleScope(::onSortTypeChanged)
     }
 
     private fun setupFragmentResultListeners() {

AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserViewModel.kt

@@ -198,6 +198,9 @@ class CardBrowserViewModel(
      */
     val flowOfReverseDirection: MutableStateFlow<ReverseDirection?> = MutableStateFlow(null)
 
+    /** Emits each time the user changes the sort order, with data for a snackbar */
+    val flowOfSortTypeChanged = MutableSharedFlow<SortChangeNotification>()
+
     /**
      * A map from column backend key to backend column definition
      *
@@ -865,9 +868,31 @@ class CardBrowserViewModel(
                 }
             }
 
+            flowOfSortTypeChanged.emit(buildSortChangeNotification(sortType))
+
             launchSearchForCards()
         }
 
+    private fun buildSortChangeNotification(sortType: SortType): SortChangeNotification =
+        when (sortType) {
+            is SortType.NoOrdering -> SortChangeNotification.NoOrdering
+            is SortType.CollectionOrdering -> {
+                val columnLabel =
+                    flowOfAllColumns.value[sortType.key.value]?.getLabel(cardsOrNotes)
+                        ?: sortType.key.value
+                val type =
+                    runCatching { CardBrowserColumn.fromColumnKey(sortType.key.value) }
+                        .getOrNull()
+                        ?.type(cardsOrNotes)
+                        ?: ColumnType.UNSPECIFIED
+                SortChangeNotification.CollectionOrdering(
+                    columnLabel = columnLabel,
+                    type = type,
+                    reverse = sortType.reverse,
+                )
+            }
+        }
+
     /**
      * Updates the backend with a new collection of columns
      *
@@ -1643,3 +1668,22 @@ data class ColumnHeading(
     val label: String,
     val ankiColumnKey: String,
 ) : Parcelable
+
+/**
+ * Data needed to show a snackbar when the sort order is changed
+ */
+sealed interface SortChangeNotification {
+    /** [SortType.NoOrdering] was selected */
+    data object NoOrdering : SortChangeNotification
+
+    /**
+     * @param columnLabel The localized label for the column
+     * @param type The data type of the column. Used to explain the sort direction
+     * @param reverse Whether the sort is ascending/descending
+     */
+    data class CollectionOrdering(
+        val columnLabel: String,
+        val type: ColumnType,
+        val reverse: Boolean,
+    ) : SortChangeNotification
+}

AnkiDroid/src/main/res/values/07-cardbrowser.xml

@@ -101,6 +101,7 @@
     <!-- Sort Order -->
     <string name="card_browser_order_no_sorting_title" comment="Title of the 'no sorting' row in the Choose Display Order bottom sheet">No sorting</string>
     <string name="card_browser_order_no_sorting_subtitle" comment="Subtitle for the 'no sorting' row noting that no-sort is faster than sorted queries">Faster</string>
+    <string name="card_browser_order_snackbar_sort_by" comment="Snackbar shown after sort changes. %1$s is the column name (e.g. 'Card Type')">Sort by %1$s</string>
 
     <string name="card_browser_order_subtitle_text_ascending" comment="Sort direction subtitle for text columns when ascending (A before Z)">A–Z</string>
     <string name="card_browser_order_subtitle_text_descending" comment="Sort direction subtitle for text columns when descending (Z before A)">Z–A</string>