fix(android-auto): run server connection check off the main thread (#1920)

Android Auto browsing could freeze and crash the app (phone app "closes",
Android Auto shows a generic connection error) whenever the Capacitor
webview had not yet established the server connection.

Root cause: onLoadChildren runs on the media browser service main thread.
It calls loadAndroidAutoItems -> checkSetValidServerConnectionConfig, which
used runBlocking to ping every saved server config and authorize the user.
That blocked the main thread on network I/O. Android Auto (plus Assistant)
re-request the browse root every ~2s, and every onGetRoot flags a reload
while disconnected, so the blocking work was triggered repeatedly and
re-entrantly, producing an ANR.

Changes:
- checkSetValidServerConnectionConfig now runs on a dedicated
  Dispatchers.IO scope instead of runBlocking, so pings/authorize never
  block the caller. The callback contract is unchanged; downstream Android
  Auto callbacks already ran off the main thread.
- loadAndroidAutoItems coalesces overlapping calls into a single in-flight
  load and fires all queued callbacks on completion, so the browse-root
  polling storm can no longer spawn concurrent loads racing shared state.
- Fix latent bug in checkResetServerItems: server config id was compared
  with !== (reference identity) instead of != (value), causing spurious
  cache resets that fed the reload storm.

Co-authored-by: databoy2k <18686442+databoy2k@users.noreply.github.com>

android/app/src/main/java/com/audiobookshelf/app/media/MediaManager.kt

@@ -9,8 +9,11 @@ import com.audiobookshelf.app.device.DeviceManager
 import com.audiobookshelf.app.server.ApiHandler
 import com.getcapacitor.JSObject
 import java.util.*
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.coroutineScope
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.launch
 import org.json.JSONException
 import org.json.JSONObject
 import kotlin.coroutines.resume
@@ -46,6 +49,16 @@ class MediaManager(private var apiHandler: ApiHandler, var ctx: Context) {
 
   var userSettingsPlaybackRate:Float? = null
 
+  // Android Auto browses on the media browser service main thread, so the server pings
+  // and authorize call must not run there or they block it and trigger an ANR
+  private val androidAutoIOScope = CoroutineScope(Dispatchers.IO + SupervisorJob())
+
+  // Android Auto re-requests the browse root every ~2s and multiple clients do so at once,
+  // so overlapping loads are coalesced into one to avoid racing on the shared server state
+  private var isLoadingAndroidAutoItems = false
+  private val pendingAndroidAutoLoadCallbacks = mutableListOf<() -> Unit>()
+  private val androidAutoLoadLock = Any()
+
   fun getIsLibrary(id:String) : Boolean {
     return serverLibraries.find { it.id == id } != null
   }
@@ -136,7 +149,7 @@ class MediaManager(private var apiHandler: ApiHandler, var ctx: Context) {
     //   and reset any server data already set
     val serverConnConfig = if (DeviceManager.isConnectedToServer) DeviceManager.serverConnectionConfig else DeviceManager.deviceData.getLastServerConnectionConfig()
 
-    if (!DeviceManager.isConnectedToServer || !DeviceManager.checkConnectivity(ctx) || serverConnConfig == null || serverConnConfig.id !== serverConfigIdUsed) {
+    if (!DeviceManager.isConnectedToServer || !DeviceManager.checkConnectivity(ctx) || serverConnConfig == null || serverConnConfig.id != serverConfigIdUsed) {
       podcastEpisodeLibraryItemMap = mutableMapOf()
       serverLibraries = listOf()
       serverLibraryItems = mutableListOf()
@@ -730,7 +743,10 @@ class MediaManager(private var apiHandler: ApiHandler, var ctx: Context) {
     return mediaProgress
   }
 
-  private fun checkSetValidServerConnectionConfig(cb: (Boolean) -> Unit) = runBlocking {
+  // Runs on [androidAutoIOScope] rather than blocking the caller: this is reached from
+  // onLoadChildren on the media browser service main thread, and the pings/authorize below
+  // are network calls, so runBlocking here caused ANRs while browsing in Android Auto
+  private fun checkSetValidServerConnectionConfig(cb: (Boolean) -> Unit) = androidAutoIOScope.launch {
     Log.d(tag, "checkSetValidServerConnectionConfig | serverConfigIdUsed=$serverConfigIdUsed | lastServerConnectionConfigId=${DeviceManager.deviceData.lastServerConnectionConfigId}")
 
     coroutineScope {
@@ -835,6 +851,26 @@ class MediaManager(private var apiHandler: ApiHandler, var ctx: Context) {
   fun loadAndroidAutoItems(cb: () -> Unit) {
     Log.d(tag, "Load android auto items")
 
+    // Coalesce overlapping calls into a single load, every caller still gets its callback
+    synchronized(androidAutoLoadLock) {
+      pendingAndroidAutoLoadCallbacks.add(cb)
+      if (isLoadingAndroidAutoItems) {
+        Log.d(tag, "loadAndroidAutoItems: Load already in progress, queued callback")
+        return
+      }
+      isLoadingAndroidAutoItems = true
+    }
+
+    val onLoadFinished = {
+      val callbacks: List<() -> Unit>
+      synchronized(androidAutoLoadLock) {
+        isLoadingAndroidAutoItems = false
+        callbacks = pendingAndroidAutoLoadCallbacks.toList()
+        pendingAndroidAutoLoadCallbacks.clear()
+      }
+      callbacks.forEach { it() }
+    }
+
     // Check if any valid server connection if not use locally downloaded books
     checkSetValidServerConnectionConfig { isConnected ->
       if (isConnected) {
@@ -844,14 +880,14 @@ class MediaManager(private var apiHandler: ApiHandler, var ctx: Context) {
         loadLibraries { libraries ->
           if (libraries.isEmpty()) {
             Log.w(tag, "No libraries returned from server request")
-            cb()
+            onLoadFinished()
           } else {
-            cb() // Fully loaded
+            onLoadFinished() // Fully loaded
           }
         }
       } else { // Not connected to server
         Log.d(tag, "loadAndroidAutoItems: Not connected to server")
-        cb()
+        onLoadFinished()
       }
     }
   }