feat(android): support reading from res/

Closes #19

README.md

@@ -44,8 +44,11 @@ const text = await FileSystem.readFile(Dirs.CacheDir + '/test.txt');
 `FileSystem.cp(source: string, target: string): Promise<void>`
 - Copy a file.
 
-`FileSystem.cpAsset(asset: string, target: string): Promise<void>`
+`FileSystem.cpAsset(asset: string, target: string, type?: 'asset' | 'resource'): Promise<void>`
 - Copy a bundled asset file.
+  - Default `type` is `asset`. Prefer this when possible.
+  - `resource` uses the Android `res/` folder, and inherits the associated
+    naming restrictions.
 
 `FileSystem.cpExternal(source: string, targetName: string, dir: 'audio' | 'downloads' | 'images' | 'video'): Promise<void>`
 - Copy a file to an externally controlled location.

android/src/main/java/com/alpha0010/fs/FileAccessModule.kt

@@ -88,9 +88,18 @@ class FileAccessModule(reactContext: ReactApplicationContext) : ReactContextBase
   }
 
   @ReactMethod
-  fun cpAsset(asset: String, target: String, promise: Promise) {
+  fun cpAsset(asset: String, target: String, type: String, promise: Promise) {
     try {
-      reactApplicationContext.assets.open(asset).use { assetStream ->
+      if (type == "resource") {
+        val id = reactApplicationContext.resources.getIdentifier(
+          asset,
+          null,
+          reactApplicationContext.packageName
+        )
+        reactApplicationContext.resources.openRawResource(id)
+      } else {
+        reactApplicationContext.assets.open(asset)
+      }.use { assetStream ->
         parsePathToFile(target).outputStream().use { assetStream.copyTo(it) }
       }
       promise.resolve(null)

example/android/app/src/main/res/raw/android_resource.txt

@@ -0,0 +1 @@
+Bundled raw resource.

example/src/App.tsx

@@ -44,6 +44,26 @@ export function App() {
         })
       );
 
+    if (Platform.OS === 'android') {
+      FileSystem.cpAsset(
+        'raw/android_resource',
+        Dirs.CacheDir + '/android_resource.txt',
+        'resource'
+      )
+        .then(() =>
+          FileSystem.readFile(Dirs.CacheDir + '/android_resource.txt')
+        )
+        .then((res) =>
+          setInfo((prev) => {
+            prev.push({
+              key: 'readFile(CacheDir/android_resource.txt)',
+              value: JSON.stringify(res),
+            });
+            return prev.slice();
+          })
+        );
+    }
+
     // Disk usage.
     FileSystem.df().then((res) =>
       setInfo((prev) => {

src/index.ts

@@ -1,6 +1,7 @@
 import { NativeModules, Platform } from 'react-native';
 import { FileAccessNative } from './native';
 import type {
+  AssetType,
   Encoding,
   ExternalDir,
   FetchResult,
@@ -10,6 +11,7 @@ import type {
 } from './types';
 
 export type {
+  AssetType,
   Encoding,
   ExternalDir,
   FetchResult,
@@ -46,9 +48,17 @@ export const FileSystem = {
 
   /**
    * Copy a bundled asset file.
-   */
-  cpAsset(asset: string, target: string) {
-    return FileAccessNative.cpAsset(asset, target);
+   *
+   * When using Android asset type 'resource', include the folder, but skip the
+   * file extension. For example use 'raw/foo', for the file 'res/raw/foo.txt'.
+   * When possible, prefer using the 'assets/' folder; files in 'res/' have
+   * naming restrictions imposed by Android.
+   * https://developer.android.com/guide/topics/resources/providing-resources.html#OriginalFiles
+   */
+  cpAsset(asset: string, target: string, type: AssetType = 'asset') {
+    return Platform.OS === 'android'
+      ? FileAccessNative.cpAsset(asset, target, type)
+      : FileAccessNative.cpAsset(asset, target);
   },
 
   /**

src/native.ts

@@ -1,5 +1,6 @@
 import { NativeModules } from 'react-native';
 import type {
+  AssetType,
   Encoding,
   ExternalDir,
   FetchResult,
@@ -12,7 +13,10 @@ type FileAccessType = {
   appendFile(path: string, data: string, encoding: Encoding): Promise<void>;
   concatFiles(source: string, target: string): Promise<number>;
   cp(source: string, target: string): Promise<void>;
-  cpAsset(asset: string, target: string): Promise<void>;
+  /**
+   * `type` only used on Android.
+   */
+  cpAsset(asset: string, target: string, type?: AssetType): Promise<void>;
   cpExternal(
     source: string,
     targetName: string,

src/types.ts

@@ -1,3 +1,9 @@
+/**
+ * asset - Android `assets/` folder or iOS main bundle.
+ * resource - Android `res/` folder.
+ */
+export type AssetType = 'asset' | 'resource';
+
 export type Encoding = 'utf8' | 'base64';
 
 export type ExternalDir = 'audio' | 'downloads' | 'images' | 'video';