Add directory related functions to AndroidAssetReader

crates/bevy_asset/src/io/android.rs

@@ -1,16 +1,15 @@
-use crate::io::{
-    get_meta_path, AssetReader, AssetReaderError, EmptyPathStream, PathStream, Reader, VecReader,
-};
-use alloc::ffi::CString;
+use crate::io::{get_meta_path, AssetReader, AssetReaderError, PathStream, Reader, VecReader};
 use bevy_utils::tracing::error;
-use std::path::Path;
+use futures_lite::stream;
+use std::{ffi::CString, path::Path};
 
 /// [`AssetReader`] implementation for Android devices, built on top of Android's [`AssetManager`].
 ///
 /// Implementation details:
 ///
-/// - [`load_path`](AssetIo::load_path) uses the [`AssetManager`] to load files.
-/// - [`read_directory`](AssetIo::read_directory) always returns an empty iterator.
+/// - All functions use the [`AssetManager`] to load files.
+/// - [`is_directory`](AssetReader::is_directory) tries to open the path
+/// as a normal file and treats an error as if the path is a directory.
 /// - Watching for changes is not supported. The watcher method will do nothing.
 ///
 /// [AssetManager]: https://developer.android.com/reference/android/content/res/AssetManager
@@ -46,15 +45,53 @@ impl AssetReader for AndroidAssetReader {
 
     async fn read_directory<'a>(
         &'a self,
-        _path: &'a Path,
+        path: &'a Path,
     ) -> Result<Box<PathStream>, AssetReaderError> {
-        let stream: Box<PathStream> = Box::new(EmptyPathStream);
-        error!("Reading directories is not supported with the AndroidAssetReader");
-        Ok(stream)
+        let asset_manager = bevy_winit::ANDROID_APP
+            .get()
+            .expect("Bevy must be setup with the #[bevy_main] macro on Android")
+            .asset_manager();
+        let opened_assets_dir = asset_manager
+            .open_dir(&CString::new(path.to_str().unwrap()).unwrap())
+            .ok_or(AssetReaderError::NotFound(path.to_path_buf()))?;
+
+        let mapped_stream = opened_assets_dir
+            .filter_map(move |f| {
+                let file_path = path.join(Path::new(f.to_str().unwrap()));
+                // filter out meta files as they are not considered assets
+                if let Some(ext) = file_path.extension().and_then(|e| e.to_str()) {
+                    if ext.eq_ignore_ascii_case("meta") {
+                        return None;
+                    }
+                }
+                Some(file_path.to_owned())
+            })
+            .collect::<Vec<_>>();
+
+        let read_dir: Box<PathStream> = Box::new(stream::iter(mapped_stream));
+        Ok(read_dir)
     }
 
-    async fn is_directory<'a>(&'a self, _path: &'a Path) -> Result<bool, AssetReaderError> {
-        error!("Reading directories is not supported with the AndroidAssetReader");
-        Ok(false)
+    async fn is_directory<'a>(
+        &'a self,
+        path: &'a Path,
+    ) -> std::result::Result<bool, AssetReaderError> {
+        let asset_manager = bevy_winit::ANDROID_APP
+            .get()
+            .expect("Bevy must be setup with the #[bevy_main] macro on Android")
+            .asset_manager();
+        // HACK: `AssetManager` does not provide a way to check if path
+        // points to a directory or a file
+        // `open_dir` succeeds for both files and directories and will only
+        // fail if the path does not exist at all
+        // `open` will fail for directories, but it will work for files
+        // The solution here was to first use `open_dir` to eliminate the case
+        // when the path does not exist at all, and then to use `open` to
+        // see if that path is a file or a directory
+        let cpath = CString::new(path.to_str().unwrap()).unwrap();
+        let _ = asset_manager
+            .open_dir(&cpath)
+            .ok_or(AssetReaderError::NotFound(path.to_path_buf()))?;
+        Ok(asset_manager.open(&cpath).is_none())
     }
 }