Runtime public download destinations

CHANGELOG.md

@@ -2,6 +2,15 @@
 
 ## Unreleased
 
+Profile-controlled public downloads.
+
+- Adds a compiled Public Downloads runtime flag used by Android DownloadManager.
+- Android 10+ writes enabled downloads to the shared user-visible Downloads directory.
+- Android 6 through 9 request WRITE_EXTERNAL_STORAGE only when public downloads are enabled.
+- Legacy devices fall back to app-specific external storage if storage permission is unavailable.
+- Disabling Public Downloads intentionally keeps downloaded files inside app-specific external storage.
+- Keeps authenticated download cookies, wrapper request headers and Android 6/API 23 compatibility.
+
 Configurable native interface controls.
 
 - Adds profile-controlled pull-to-refresh using Android SwipeRefreshLayout.

app/src/main/java/de/starlightunit/wrapper/MainActivity.java

@@ -1,8 +1,10 @@
 package de.starlightunit.wrapper;
 
+import android.Manifest;
 import android.app.Activity;
 import android.content.ActivityNotFoundException;
 import android.content.Intent;
+import android.content.pm.PackageManager;
 import android.graphics.Color;
 import android.os.Build;
 import android.os.Bundle;
@@ -24,6 +26,7 @@
 import de.starlightunit.wrapper.bridge.QuantumNativeMediaBridge;
 import de.starlightunit.wrapper.config.AppConfig;
 import de.starlightunit.wrapper.download.AppDownloadListener;
+import de.starlightunit.wrapper.download.DownloadDestinationPolicy;
 import de.starlightunit.wrapper.launch.QuantumIntroController;
 import de.starlightunit.wrapper.media.QuantumNativeMediaPlayer;
 import de.starlightunit.wrapper.navigation.NavigationPolicy;
@@ -42,6 +45,7 @@ public final class MainActivity extends Activity
         GameWebChromeClient.Callbacks {
 
     private static final int FILE_CHOOSER_REQUEST = 7001;
+    private static final int LEGACY_DOWNLOAD_PERMISSION_REQUEST = 7002;
 
     private WebView webView;
     private LoadingIndicatorController loadingIndicator;
@@ -119,6 +123,7 @@ protected void onCreate(Bundle savedInstanceState) {
         chromeClient = new GameWebChromeClient(fullscreenContainer, this, this);
         webView.setWebChromeClient(chromeClient);
         webView.setDownloadListener(new AppDownloadListener(this, requestHeaders));
+        requestLegacyPublicDownloadPermissionIfNeeded();
 
         retryButton.setOnClickListener(v -> {
             errorPanel.setVisibility(View.GONE);
@@ -142,6 +147,21 @@ private void loadTrustedUrl(String requestedUrl) {
         webView.loadUrl(targetUrl, requestHeaders);
     }
 
+    private void requestLegacyPublicDownloadPermissionIfNeeded() {
+        boolean granted = checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
+                == PackageManager.PERMISSION_GRANTED;
+        if (DownloadDestinationPolicy.needsLegacyWritePermission(
+                AppConfig.PUBLIC_DOWNLOADS_ENABLED,
+                Build.VERSION.SDK_INT,
+                granted
+        )) {
+            requestPermissions(
+                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
+                    LEGACY_DOWNLOAD_PERMISSION_REQUEST
+            );
+        }
+    }
+
     private void configureWindow() {
         Window window = getWindow();
         window.setStatusBarColor(Color.BLACK);

app/src/main/java/de/starlightunit/wrapper/config/AppConfig.java

@@ -42,6 +42,7 @@ public final class AppConfig {
     public static final int FONT_SCALE_PERCENT = 100;
     public static final boolean ALLOW_AUTOPLAY_MEDIA = true;
     public static final boolean ALLOW_THIRD_PARTY_COOKIES = true;
+    public static final boolean PUBLIC_DOWNLOADS_ENABLED = true;
 
     private AppConfig() {
     }

app/src/main/java/de/starlightunit/wrapper/download/AppDownloadListener.java

@@ -17,6 +17,7 @@
 import java.util.Map;
 
 import de.starlightunit.wrapper.R;
+import de.starlightunit.wrapper.config.AppConfig;
 
 public final class AppDownloadListener implements DownloadListener {
     private final Context context;
@@ -72,7 +73,13 @@ public void onDownloadStart(
                 request.addRequestHeader("Cookie", cookies);
             }
 
-            if (canWritePublicDownloads()) {
+            boolean legacyPermissionGranted = context.checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
+                    == PackageManager.PERMISSION_GRANTED;
+            if (DownloadDestinationPolicy.usePublicDownloads(
+                    AppConfig.PUBLIC_DOWNLOADS_ENABLED,
+                    Build.VERSION.SDK_INT,
+                    legacyPermissionGranted
+            )) {
                 request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, fileName);
             } else {
                 request.setDestinationInExternalFilesDir(context, Environment.DIRECTORY_DOWNLOADS, fileName);
@@ -104,11 +111,4 @@ private static boolean isDownloadSafeHeader(String name, String value) {
                 && !"connection".equals(normalized);
     }
 
-    private boolean canWritePublicDownloads() {
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-            return true;
-        }
-        return context.checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
-                == PackageManager.PERMISSION_GRANTED;
-    }
 }

app/src/main/java/de/starlightunit/wrapper/download/DownloadDestinationPolicy.java

@@ -0,0 +1,31 @@
+package de.starlightunit.wrapper.download;
+
+public final class DownloadDestinationPolicy {
+    private DownloadDestinationPolicy() {
+    }
+
+    public static boolean usePublicDownloads(
+            boolean publicDownloadsEnabled,
+            int sdkInt,
+            boolean legacyWritePermissionGranted
+    ) {
+        if (!publicDownloadsEnabled) {
+            return false;
+        }
+        if (sdkInt >= 29) {
+            return true;
+        }
+        return legacyWritePermissionGranted;
+    }
+
+    public static boolean needsLegacyWritePermission(
+            boolean publicDownloadsEnabled,
+            int sdkInt,
+            boolean legacyWritePermissionGranted
+    ) {
+        return publicDownloadsEnabled
+                && sdkInt >= 23
+                && sdkInt <= 28
+                && !legacyWritePermissionGranted;
+    }
+}

app/src/test/java/de/starlightunit/wrapper/download/DownloadDestinationPolicyTest.java

@@ -0,0 +1,37 @@
+package de.starlightunit.wrapper.download;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public final class DownloadDestinationPolicyTest {
+    @Test
+    public void android10PlusUsesPublicDownloadsWhenEnabled() {
+        assertTrue(DownloadDestinationPolicy.usePublicDownloads(true, 29, false));
+        assertTrue(DownloadDestinationPolicy.usePublicDownloads(true, 36, false));
+    }
+
+    @Test
+    public void disabledAlwaysUsesAppPrivateDestination() {
+        assertFalse(DownloadDestinationPolicy.usePublicDownloads(false, 36, true));
+        assertFalse(DownloadDestinationPolicy.usePublicDownloads(false, 28, true));
+    }
+
+    @Test
+    public void android6Through9RequireLegacyPermission() {
+        assertFalse(DownloadDestinationPolicy.usePublicDownloads(true, 23, false));
+        assertTrue(DownloadDestinationPolicy.usePublicDownloads(true, 23, true));
+        assertFalse(DownloadDestinationPolicy.usePublicDownloads(true, 28, false));
+        assertTrue(DownloadDestinationPolicy.usePublicDownloads(true, 28, true));
+    }
+
+    @Test
+    public void legacyPermissionPromptOnlyNeededOnApi23Through28() {
+        assertTrue(DownloadDestinationPolicy.needsLegacyWritePermission(true, 23, false));
+        assertTrue(DownloadDestinationPolicy.needsLegacyWritePermission(true, 28, false));
+        assertFalse(DownloadDestinationPolicy.needsLegacyWritePermission(true, 29, false));
+        assertFalse(DownloadDestinationPolicy.needsLegacyWritePermission(false, 28, false));
+        assertFalse(DownloadDestinationPolicy.needsLegacyWritePermission(true, 28, true));
+    }
+}