Adds back navigation to spaces

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

@@ -72,6 +72,8 @@ class AppStateHandler @Inject constructor(
 
     val selectedRoomGroupingFlow = selectedSpaceDataSource.stream()
 
+    private val spaceBackstack = ArrayDeque<String?>()
+
     fun getCurrentRoomGroupingMethod(): RoomGroupingMethod? {
         // XXX we should somehow make it live :/ just a work around
         // For example just after creating a space and switching to it the
@@ -87,12 +89,16 @@ class AppStateHandler @Inject constructor(
         }
     }
 
-    fun setCurrentSpace(spaceId: String?, session: Session? = null, persistNow: Boolean = false) {
+    fun setCurrentSpace(spaceId: String?, session: Session? = null, persistNow: Boolean = false, isForwardNavigation: Boolean = true) {
+        val currentSpace = (selectedSpaceDataSource.currentValue?.orNull() as? RoomGroupingMethod.BySpace)?.space()
         val uSession = session ?: activeSessionHolder.getSafeActiveSession() ?: return
-        if (selectedSpaceDataSource.currentValue?.orNull() is RoomGroupingMethod.BySpace &&
+        if (currentSpace != null && spaceId == currentSpace.roomId) return
-                spaceId == selectedSpaceDataSource.currentValue?.orNull()?.space()?.roomId) return
         val spaceSum = spaceId?.let { uSession.getRoomSummary(spaceId) }
 
+        if (isForwardNavigation) {
+            spaceBackstack.addLast(currentSpace?.roomId)
+        }
+
         if (persistNow) {
             uiStateRepository.storeGroupingMethod(true, uSession.sessionId)
             uiStateRepository.storeSelectedSpace(spaceSum?.roomId, uSession.sessionId)
@@ -151,6 +157,8 @@ class AppStateHandler @Inject constructor(
                 }.launchIn(session.coroutineScope)
     }
 
+    fun getSpaceBackstack() = spaceBackstack
+
     fun safeActiveSpaceId(): String? {
         return (selectedSpaceDataSource.currentValue?.orNull() as? RoomGroupingMethod.BySpace)?.spaceSummary?.roomId
     }

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

@@ -146,7 +146,7 @@ class HomeDetailFragment @Inject constructor(
         }
 
         views.groupToolbarNavigateUp.setOnClickListener {
-            navigateUpOneSpace()
+            navigateBack()
         }
 
         viewModel.observeViewEvents { viewEvent ->
@@ -191,10 +191,23 @@ class HomeDetailFragment @Inject constructor(
                 }
     }
 
+    private fun navigateBack() {
+        try {
+            val lastSpace = appStateHandler.getSpaceBackstack().removeLast()
+            setCurrentSpace(lastSpace)
+        } catch (e: NoSuchElementException) {
+            navigateUpOneSpace()
+        }
+    }
+
+    private fun setCurrentSpace(spaceId: String?) {
+        appStateHandler.setCurrentSpace(spaceId, isForwardNavigation = false)
+        sharedActionViewModel.post(HomeActivitySharedAction.CloseGroup)
+    }
+
     private fun navigateUpOneSpace() {
         val parentId = getCurrentSpace()?.flattenParentIds?.lastOrNull()
-        appStateHandler.setCurrentSpace(parentId)
+        setCurrentSpace(parentId)
-        sharedActionViewModel.post(HomeActivitySharedAction.CloseGroup)
     }
 
     private fun getCurrentSpace() = (appStateHandler.getCurrentRoomGroupingMethod() as? RoomGroupingMethod.BySpace)?.spaceSummary
@@ -495,7 +508,7 @@ class HomeDetailFragment @Inject constructor(
     }
 
     override fun onBackPressed(toolbarButton: Boolean) = if (getCurrentSpace() != null) {
-        navigateUpOneSpace()
+        navigateBack()
         true
     } else {
         false