For #1406, #1465 - Only pop browser when all sessions have been removed

app/src/main/java/org/mozilla/fenix/HomeActivity.kt

@@ -16,6 +16,7 @@ import androidx.navigation.ui.AppBarConfiguration
 import androidx.navigation.ui.NavigationUI
 import mozilla.components.browser.search.SearchEngine
 import mozilla.components.browser.session.Session
+import mozilla.components.browser.session.SessionManager
 import mozilla.components.concept.engine.EngineView
 import mozilla.components.feature.intent.IntentProcessor
 import mozilla.components.lib.crash.Crash
@@ -35,6 +36,8 @@ import org.mozilla.fenix.settings.SettingsFragmentDirections
 @SuppressWarnings("TooManyFunctions")
 open class HomeActivity : AppCompatActivity() {
     open val isCustomTab = false
+    private var sessionObserver: SessionManager.Observer? = null
+    var allSessionsRemoved = false
 
     val themeManager = DefaultThemeManager().also {
         it.onThemeChange = { theme ->
@@ -51,6 +54,7 @@ open class HomeActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+        sessionObserver = subscribeToSessions()
 
         setTheme(themeManager.currentTheme)
         DefaultThemeManager.applyStatusBarTheme(window, themeManager, this)
@@ -82,9 +86,17 @@ open class HomeActivity : AppCompatActivity() {
 
     override fun onResume() {
         super.onResume()
-        // No session or timed out; we should try to pop inclusive to browser if not in private mode
-        if (components.core.sessionStorage.current() == null && !browsingModeManager.isPrivate) {
+        // All sessions have been removed; we should try to pop inclusive to browser if not in private mode
+        if (allSessionsRemoved && !browsingModeManager.isPrivate) {
             navHost.navController.popBackStack(R.id.browserFragment, true)
+            allSessionsRemoved = false
+        }
+    }
+
+    override fun onDestroy() {
+        super.onDestroy()
+        sessionObserver?.let {
+            components.core.sessionManager.unregister(it)
         }
     }
 
@@ -190,6 +202,17 @@ open class HomeActivity : AppCompatActivity() {
         }
     }
 
+    private fun subscribeToSessions(): SessionManager.Observer {
+        val observer = object : SessionManager.Observer {
+            override fun onAllSessionsRemoved() {
+                super.onAllSessionsRemoved()
+                allSessionsRemoved = true
+            }
+        }
+        components.core.sessionManager.register(observer)
+        return observer
+    }
+
     companion object {
         const val OPEN_TO_BROWSER = "open_to_browser"
     }