Make subfolder grouping follow file structure

This changes subfolder grouping to follow file hierarchy
to prevent unreliable behavior with middle folders missing
media.

This fixes #1886

app/src/main/kotlin/com/simplemobiletools/gallery/pro/extensions/Context.kt

@@ -195,37 +195,22 @@ fun Context.getDirsToShow(dirs: ArrayList<Directory>, allDirs: ArrayList<Directo
 
 fun Context.getDirectParentSubfolders(dirs: ArrayList<Directory>, currentPathPrefix: String): ArrayList<Directory> {
     val folders = dirs.map { it.path }.sorted().toMutableSet() as HashSet<String>
-    val currentPaths = LinkedHashSet<String>()
+    // Sort by path length, to ensure that parents get processed first
-    val foldersWithoutMediaFiles = ArrayList<String>()
+    val foldersByPathLength = dirs.filter { currentPathPrefix.isEmpty() || (it.path.startsWith(currentPathPrefix, true) && it.path != currentPathPrefix) }.sortedBy { it.path.length }
     var newDirId = 1000L
+    val groups = mutableMapOf<String, MutableList<Directory>>()
 
-    for (path in folders) {
+    for (folder in foldersByPathLength) {
-        if (path == RECYCLE_BIN || path == FAVORITES) {
+        val parent = groups.keys.firstOrNull { folder.path.startsWith(it, true) }
-            continue
+        if (parent != null) {
-        }
+            // If we have parent in top level groups
-
+            // Add this folder to that group,
-        if (currentPathPrefix.isNotEmpty()) {
+            // but also add all folders in between which may not have media files
-            if (!path.startsWith(currentPathPrefix, true)) {
+            groups.getOrPut(parent, ::mutableListOf).apply {
-                continue
+                var midParent = File(folder.path).parent
-            }
+                while (midParent != null && none { it.path.equals(midParent, true) }) {
-
-            if (!File(path).parent.equals(currentPathPrefix, true)) {
-                continue
-            }
-        }
-
-        if (currentPathPrefix.isNotEmpty() && path.equals(currentPathPrefix, true) || File(path).parent.equals(currentPathPrefix, true)) {
-            currentPaths.add(path)
-        } else if (folders.any { !it.equals(path, true) && (File(path).parent.equals(it, true) || File(it).parent.equals(File(path).parent, true)) }) {
-            // if we have folders like
-            // /storage/emulated/0/Pictures/Images and
-            // /storage/emulated/0/Pictures/Screenshots,
-            // but /storage/emulated/0/Pictures is empty, still Pictures with the first folders thumbnails and proper other info
-            val parent = File(path).parent
-            if (parent != null && !folders.contains(parent) && dirs.none { it.path.equals(parent, true) }) {
-                currentPaths.add(parent)
                     val isSortingAscending = config.sorting.isSortingAscending()
-                val subDirs = dirs.filter { File(it.path).parent.equals(File(path).parent, true) } as ArrayList<Directory>
+                    val subDirs = dirs.filter { File(it.path).parent.equals(midParent, true) } as ArrayList<Directory>
                     if (subDirs.isNotEmpty()) {
                         val lastModified = if (isSortingAscending) {
                             subDirs.minByOrNull { it.modified }?.modified
@@ -246,38 +231,46 @@ fun Context.getDirectParentSubfolders(dirs: ArrayList<Directory>, currentPathPre
 
                         val directory = Directory(
                             newDirId++,
-                        parent,
+                            midParent,
                             subDirs.first().tmb,
-                        getFolderNameFromPath(parent),
+                            getFolderNameFromPath(midParent),
                             subDirs.sumBy { it.mediaCnt },
                             lastModified,
                             dateTaken,
                             subDirs.sumByLong { it.size },
-                        getPathLocation(parent),
+                            getPathLocation(midParent),
                             mediaTypes,
                             ""
                         )
 
                         directory.containsMediaFilesDirectly = false
                         dirs.add(directory)
-                    currentPaths.add(parent)
+                        add(directory)
-                    foldersWithoutMediaFiles.add(parent)
                     }
+                    midParent = File(midParent).parent
+                }
+                add(folder)
             }
         } else {
-            currentPaths.add(path)
+            // If we have don't have parent in top level groups
+            // Set this folder as top level group if it is direct child
+            if (currentPathPrefix.isEmpty() || File(folder.path).parent.equals(currentPathPrefix, true)) {
+                groups.getOrPut(folder.path, ::mutableListOf).add(folder)
+            } else {
+                // Otherwise find its parent which is a direct child of current path prefix
+                // And create a group for it
+                var firstVisibleParent = File(folder.path).parent
+                while (firstVisibleParent != null && !File(firstVisibleParent).parent.equals(currentPathPrefix, true)) {
+                    firstVisibleParent = File(firstVisibleParent).parent
+                }
+                if (firstVisibleParent != null) {
+                    groups.getOrPut(firstVisibleParent, ::mutableListOf).add(folder)
+                }
+            }
         }
     }
 
-    var areDirectSubfoldersAvailable = false
+    val currentPaths = groups.keys.toMutableList()
-    currentPaths.forEach {
-        val path = it
-        currentPaths.forEach {
-            if (!foldersWithoutMediaFiles.contains(it) && !it.equals(path, true) && File(it).parent?.equals(path, true) == true) {
-                areDirectSubfoldersAvailable = true
-            }
-        }
-    }
 
     if (currentPathPrefix.isEmpty() && folders.contains(RECYCLE_BIN)) {
         currentPaths.add(RECYCLE_BIN)
@@ -294,12 +287,7 @@ fun Context.getDirectParentSubfolders(dirs: ArrayList<Directory>, currentPathPre
     folders.clear()
     folders.addAll(currentPaths)
 
-    val dirsToShow = dirs.filter { folders.contains(it.path) } as ArrayList<Directory>
+    return dirs.filter { folders.contains(it.path) } as ArrayList<Directory>
-    return if (areDirectSubfoldersAvailable) {
-        getDirectParentSubfolders(dirsToShow, currentPathPrefix)
-    } else {
-        dirsToShow
-    }
 }
 
 fun Context.updateSubfolderCounts(children: ArrayList<Directory>, parentDirs: ArrayList<Directory>) {