fix: Prevent race / crash when updating main drawer items (#1150)

Previous code could crash if the main drawer items weren't created
before setting the optional items (scheduled statuses, lists, etc).

Protect the drawer item manipulation with a mutex to prevent this.

app/src/main/java/app/pachli/MainActivity.kt

@@ -181,6 +181,8 @@ import kotlinx.coroutines.flow.distinctUntilChangedBy
 import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import timber.log.Timber
 
 @AndroidEntryPoint
@@ -254,6 +256,9 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, MenuProvider {
 
     private var pachliAccountId by Delegates.notNull<Long>()
 
+    /** Mutex to protect modifications to the drawer's items. */
+    private val drawerMutex = Mutex()
+
     @SuppressLint("RestrictedApi")
     override fun onCreate(savedInstanceState: Bundle?) {
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.S) {
@@ -761,7 +766,7 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, MenuProvider {
      * (because the top toolbar is hidden), false if any existing search item should be
      * removed.
      */
-    private fun bindMainDrawerSearch(context: Context, pachliAccountId: Long, showSearchItem: Boolean) {
+    private suspend fun bindMainDrawerSearch(context: Context, pachliAccountId: Long, showSearchItem: Boolean) = drawerMutex.withLock {
         val searchItemPosition = binding.mainDrawer.getPosition(DRAWER_ITEM_SEARCH)
         val showing = searchItemPosition != -1
 
@@ -802,7 +807,7 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, MenuProvider {
      * @param showSchedulePosts True if a "Scheduled posts" menu item should be added
      * to the list, false if any existing item should be removed.
      */
-    private fun bindMainDrawerScheduledPosts(context: Context, pachliAccountId: Long, showSchedulePosts: Boolean) {
+    private suspend fun bindMainDrawerScheduledPosts(context: Context, pachliAccountId: Long, showSchedulePosts: Boolean) = drawerMutex.withLock {
         val existingPosition = binding.mainDrawer.getPosition(DRAWER_ITEM_SCHEDULED_POSTS)
         val showing = existingPosition != -1
 
@@ -834,7 +839,7 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, MenuProvider {
     }
 
     /** Binds [lists] to the "Lists" section in the main drawer. */
-    private fun bindMainDrawerLists(pachliAccountId: Long, lists: List<MastodonList>) {
+    private suspend fun bindMainDrawerLists(pachliAccountId: Long, lists: List<MastodonList>) = drawerMutex.withLock {
         binding.mainDrawer.removeItems(*listDrawerItems.toTypedArray())
 
         listDrawerItems.clear()
@@ -868,7 +873,7 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, MenuProvider {
      *
      * See [bindMainDrawerLists] and [bindMainDrawerSearch].
      */
-    private fun bindMainDrawerItems(pachliAccount: PachliAccount, savedInstanceState: Bundle?) {
+    private suspend fun bindMainDrawerItems(pachliAccount: PachliAccount, savedInstanceState: Bundle?) = drawerMutex.withLock {
         val pachliAccountId = pachliAccount.id
 
         binding.mainDrawer.apply {
@@ -1398,7 +1403,7 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, MenuProvider {
      *
      * Shows/clears a badge showing the number of unread announcements.
      */
-    private fun bindMainDrawerAnnouncements(announcements: List<Announcement>) {
+    private suspend fun bindMainDrawerAnnouncements(announcements: List<Announcement>) = drawerMutex.withLock {
         val unread = announcements.count { !it.read }
         binding.mainDrawer.updateBadge(DRAWER_ITEM_ANNOUNCEMENTS, StringHolder(if (unread <= 0) null else unread.toString()))
     }