Refactors space backstack handling

vector/src/main/java/im/vector/app/SpaceStateHandler.kt

@@ -51,11 +51,11 @@ interface SpaceStateHandler : DefaultLifecycleObserver {
     )
 
     /**
-     * Gets the current backstack of spaces (via their id).
+     * Gets the Space ID of the space on top of the backstack
      *
-     * null may be an entry in the ArrayDeque to indicate the root space (All Chats)
+     * May return null to indicate the All Chats space
      */
-    fun getSpaceBackstack(): ArrayDeque<String?>
+    fun popSpaceBackstack(): String?
 
     /**
      * Gets a flow of the selected space for clients to react immediately to space changes.

vector/src/main/java/im/vector/app/SpaceStateHandlerImpl.kt

@@ -138,7 +138,14 @@ class SpaceStateHandlerImpl @Inject constructor(
                 }.launchIn(session.coroutineScope)
     }
 
-    override fun getSpaceBackstack() = spaceBackstack
+    override fun popSpaceBackstack(): String? {
+        val poppedSpaceId = spaceBackstack.removeLast()
+        vectorPreferences.getPersistedSpaceBackstack().toMutableList().apply {
+            removeLast()
+            vectorPreferences.setPersistedSpaceBackstack(this)
+        }
+        return poppedSpaceId
+    }
 
     override fun getSelectedSpaceFlow() = selectedSpaceFlow
 

vector/src/main/java/im/vector/app/features/home/HomeDetailFragment.kt

@@ -183,7 +183,7 @@ class HomeDetailFragment @Inject constructor(
     }
 
     private fun navigateBack() {
-        val previousSpaceId = spaceStateHandler.getSpaceBackstack().removeLastOrNull()
+        val previousSpaceId = spaceStateHandler.popSpaceBackstack()
         val parentSpaceId = spaceStateHandler.getCurrentSpace()?.flattenParentIds?.lastOrNull()
         setCurrentSpace(previousSpaceId ?: parentSpaceId)
     }

vector/src/main/java/im/vector/app/features/home/NewHomeDetailFragment.kt

@@ -178,10 +178,8 @@ class NewHomeDetailFragment @Inject constructor(
     }
 
     private fun navigateBack() {
-        val spaceBackstack = spaceStateHandler.getSpaceBackstack()
-
         try {
-            val previousSpaceId = spaceBackstack.removeLast()
+            val previousSpaceId = spaceStateHandler.popSpaceBackstack()
             setCurrentSpace(previousSpaceId)
         } catch (e: NoSuchElementException) {
             requireActivity().finish()