feat: recursive local wallpapers and filter for images only

app/src/main/java/com/bnyro/wallpaper/util/LocalWallpaperHelper.kt

@@ -1,14 +1,45 @@
 package com.bnyro.wallpaper.util
 
 import android.content.Context
+import android.graphics.BitmapFactory
 import androidx.core.net.toUri
 import androidx.documentfile.provider.DocumentFile
 import com.bnyro.wallpaper.enums.WallpaperConfig
 
 object LocalWallpaperHelper {
+    private fun getAllFilesInCurrentDir(directory: DocumentFile?): List<DocumentFile> {
+        val files = mutableListOf<DocumentFile>()
+
+        val contents = directory?.listFiles().orEmpty()
+        files.addAll(contents.filter { it.isFile })
+
+        contents.filter { it.isDirectory }.forEach {
+            files.addAll(getAllFilesInCurrentDir(it))
+        }
+
+        return files
+    }
+
+    private fun DocumentFile.isImage(context: Context): Boolean {
+        val bmOptions = BitmapFactory.Options().apply {
+            inJustDecodeBounds = true
+        }
+        return try {
+            context.contentResolver.openInputStream(uri).use {
+                BitmapFactory.decodeStream(it, null, bmOptions)
+            }
+            bmOptions.outWidth != -1 && bmOptions.outHeight != -1
+        } catch (_: Exception) {
+            false
+        }
+    }
+
     fun getLocalWalls(context: Context, config: WallpaperConfig): List<DocumentFile> {
         return config.localFolderUris.map {
-            DocumentFile.fromTreeUri(context, it.toUri())?.listFiles().orEmpty().toList()
-        }.flatten()
+            val dir = DocumentFile.fromTreeUri(context, it.toUri())
+            getAllFilesInCurrentDir(dir)
+        }
+            .flatten()
+            .filter { it.isImage(context) }
     }
 }