Fall back to session installer when chosen installer is unavailable

Address #1386

The Shizuku branch of getPreferredInstaller() already fell back to the
session installer, but the guard hasShizukuPerm() called
Shizuku.checkSelfPermission(), which throws when the binder is not alive
(Shizuku disabled). The exception escaped before the fallback could run,
so installs failed instead of falling back.

- Guard hasShizukuPerm() on Shizuku.pingBinder() and swallow failures so
  it returns false (instead of throwing) when Shizuku is unavailable,
  letting the existing fallback run. This also fixes canInstallSilently().
- Detect when any chosen installer resolves to the default and optionally
  inform the user via a toast, gated by notifyOnFallback so cancel/remove
  callers stay silent while real install paths surface it.

app/src/main/java/com/aurora/store/data/helper/DownloadHelper.kt

@@ -174,8 +174,9 @@ class DownloadHelper @Inject constructor(
         if (existing != null && existing.versionCode == download.versionCode) {
             if (existing.canInstall(context)) {
                 Log.i(TAG, "${download.packageName} already downloaded, installing directly")
-                runCatching { appInstaller.getPreferredInstaller().install(existing) }
-                    .onFailure { Log.e(TAG, "Failed to install ${download.packageName}", it) }
+                runCatching {
+                    appInstaller.getPreferredInstaller(notifyOnFallback = true).install(existing)
+                }.onFailure { Log.e(TAG, "Failed to install ${download.packageName}", it) }
                 return
             }
             if (existing.isActive) {

app/src/main/java/com/aurora/store/data/installer/AppInstaller.kt

@@ -25,13 +25,17 @@ import android.content.Intent
 import android.content.pm.PackageManager
 import android.net.Uri
 import android.os.Build
+import android.util.Log
 import androidx.core.content.pm.PackageInfoCompat
 import com.aurora.Constants.PACKAGE_NAME_GMS
+import com.aurora.extensions.TAG
 import com.aurora.extensions.getUpdateOwnerPackageNameCompat
 import com.aurora.extensions.isOAndAbove
 import com.aurora.extensions.isPAndAbove
 import com.aurora.extensions.isSAndAbove
+import com.aurora.extensions.toast
 import com.aurora.store.BuildConfig
+import com.aurora.store.R
 import com.aurora.store.data.installer.ShizukuInstaller.Companion.SHIZUKU_PACKAGE_NAME
 import com.aurora.store.data.installer.base.IInstaller
 import com.aurora.store.data.model.Installer
@@ -172,8 +176,15 @@ class AppInstaller @Inject constructor(
         fun hasShizukuOrSui(context: Context): Boolean = isOAndAbove &&
             (PackageUtil.isInstalled(context, SHIZUKU_PACKAGE_NAME) || Sui.isSui())
 
-        fun hasShizukuPerm(): Boolean =
-            Shizuku.checkSelfPermission() == PackageManager.PERMISSION_GRANTED
+        // Shizuku.checkSelfPermission() throws when the binder is not alive (Shizuku
+        // disabled/not running), so guard on pingBinder() and swallow any failure to let
+        // callers fall back gracefully instead of crashing.
+        fun hasShizukuPerm(): Boolean = try {
+            Shizuku.pingBinder() &&
+                Shizuku.checkSelfPermission() == PackageManager.PERMISSION_GRANTED
+        } catch (_: Exception) {
+            false
+        }
 
         fun uninstall(context: Context, packageName: String) {
             val intent = Intent().apply {
@@ -196,31 +207,47 @@ class AppInstaller @Inject constructor(
 
     fun getMicroGInstaller(): IInstaller = microGInstaller
 
-    fun getPreferredInstaller(): IInstaller = when (getCurrentInstaller(context)) {
-        Installer.SESSION -> sessionInstaller
+    /**
+     * Returns the installer for the user's chosen mode, transparently falling back to the
+     * default (session) installer when that mode is currently unavailable, e.g. the chosen
+     * Shizuku installer when Shizuku is disabled.
+     * @param notifyOnFallback Whether to inform the user via a toast when a fallback happens
+     */
+    fun getPreferredInstaller(notifyOnFallback: Boolean = false): IInstaller {
+        val selected = getCurrentInstaller(context)
+        val installer = when (selected) {
+            Installer.SESSION -> sessionInstaller
 
-        Installer.NATIVE -> nativeInstaller
+            Installer.NATIVE -> nativeInstaller
 
-        Installer.ROOT -> if (hasRootAccess()) rootInstaller else defaultInstaller
+            Installer.ROOT -> if (hasRootAccess()) rootInstaller else defaultInstaller
 
-        Installer.SERVICE -> if (hasAuroraService(context)) {
-            serviceInstaller
-        } else {
-            defaultInstaller
+            Installer.SERVICE -> if (hasAuroraService(context)) {
+                serviceInstaller
+            } else {
+                defaultInstaller
+            }
+
+            Installer.AM -> if (hasAppManager(context)) amInstaller else defaultInstaller
+
+            Installer.SHIZUKU -> if (hasShizukuOrSui(context) && hasShizukuPerm()) {
+                shizukuInstaller
+            } else {
+                defaultInstaller
+            }
+
+            Installer.MICROG -> if (hasMicroGInstaller(context)) {
+                microGInstaller
+            } else {
+                defaultInstaller
+            }
         }
 
-        Installer.AM -> if (hasAppManager(context)) amInstaller else defaultInstaller
-
-        Installer.SHIZUKU -> if (hasShizukuOrSui(context) && hasShizukuPerm()) {
-            shizukuInstaller
-        } else {
-            defaultInstaller
+        if (selected != Installer.SESSION && installer === defaultInstaller) {
+            Log.i(TAG, "$selected installer unavailable, falling back to session installer")
+            if (notifyOnFallback) context.toast(R.string.installer_fallback_session)
         }
 
-        Installer.MICROG -> if (hasMicroGInstaller(context)) {
-            microGInstaller
-        } else {
-            defaultInstaller
-        }
+        return installer
     }
 }

app/src/main/java/com/aurora/store/data/work/DownloadWorker.kt

@@ -252,7 +252,7 @@ class DownloadWorker @AssistedInject constructor(
     private suspend fun onSuccess(): Result {
         return withContext(NonCancellable) {
             return@withContext try {
-                appInstaller.getPreferredInstaller().install(download)
+                appInstaller.getPreferredInstaller(notifyOnFallback = true).install(download)
                 Result.success()
             } catch (exception: Exception) {
                 Log.e(TAG, "Failed to install ${download.packageName}", exception)

app/src/main/java/com/aurora/store/viewmodel/downloads/DownloadsViewModel.kt

@@ -75,7 +75,7 @@ class DownloadsViewModel @Inject constructor(
 
     fun install(download: Download) {
         try {
-            appInstaller.getPreferredInstaller().install(download)
+            appInstaller.getPreferredInstaller(notifyOnFallback = true).install(download)
         } catch (exception: Exception) {
             Log.e(TAG, "Failed to install ${download.packageName}", exception)
         }