[fenix] Issue 5736 Improve pop behavior after deleting tabs in settings (https://github.com/mozilla-mobile/fenix/pull/7478)

app/src/androidTest/java/org/mozilla/fenix/ui/SettingsPrivacyTest.kt

@@ -265,6 +265,11 @@ class SettingsPrivacyTest {
         // Return to home screen and verify that all tabs, history and collection are gone
         //
         // Verify xxx
+        //
+        // New: If coming from  tab -> settings -> delete browsing data
+        // then expect to return to home screen
+        // If coming from tab -> home -> settings -> delete browsing data
+        // then expect return to settings (after which you can return to home manually)
     }
 
     @Ignore("This is a stub test, ignore for now")

app/src/main/java/org/mozilla/fenix/settings/deletebrowsingdata/DeleteBrowsingDataFragment.kt

@@ -153,7 +153,7 @@ class DeleteBrowsingDataFragment : Fragment(R.layout.fragment_delete_browsing_da
         if (popAfter) viewLifecycleOwner.lifecycleScope.launch(
             Dispatchers.Main
         ) {
-            findNavController().popBackStack(R.id.homeFragment, false)
+            returnToDeletionOrigin()
         }
     }
 
@@ -239,6 +239,46 @@ class DeleteBrowsingDataFragment : Fragment(R.layout.fragment_delete_browsing_da
             fragmentView.site_permissions_item
         )
     }
+    // If coming from Open Tab -> Settings, pop back to Home
+    // If coming from Home -> Settings, pop back to Settings
+    private fun returnToDeletionOrigin() {
+        // If Delete browsing data fragment isn't in the backstack
+        // then Android may have changed their naming convention
+        // and we want to prevent a crash by defaulting to pop home behavior
+        if (checkIfFragmentInBackStack(R.id.deleteBrowsingDataFragment)) {
+            // If Settings is in the backstack then we can continue with intended behavior
+            if (checkIfFragmentInBackStack(R.id.browserFragment)) findNavController().popBackStack(
+                R.id.homeFragment,
+                false
+            )
+            else findNavController().popBackStack()
+        } else {
+            findNavController().popBackStack(
+                R.id.homeFragment,
+                false
+            )
+        }
+    }
+
+    // For some reason, the only way you can tell if you came from
+    // BrowserFrag -> Settings OR BrowserFrag -> HomeFrag -> Settings is to check whether
+    // there is a browser fragment entry in the back stack. If there is, it means you came from BrowserFrag -> Settings
+    // if there isn't, it means you came from HomeFrag -> Settings
+    private fun checkIfFragmentInBackStack(res: Int): Boolean {
+        val backStackEntryCount = parentFragmentManager.backStackEntryCount
+        for (i in 0 until backStackEntryCount) {
+            if (getResIdFromBackstack(parentFragmentManager.getBackStackEntryAt(i).name) == res) {
+                return true
+            }
+        }
+
+        return false
+    }
+
+    private fun getResIdFromBackstack(name: String?): Int {
+        val idString = name?.split("-")
+        return idString!![1].toInt()
+    }
 
     companion object {
         private const val ENABLED_ALPHA = 1f