Use validation instead of two-way binding

This is insane, but it appears to be working. We essentially store
things in a separate class for editing, and then commit it back at a
given time.

This business with onViewStateRestored in both TunnelEditorFragment and
in TunnelDetailFragment is buggy and likely wrong.

In general TunnelEditorFragment should probably be rewritten. The
relationship with the changed name is not clear.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/android/fragment/TunnelDetailFragment.java

@@ -10,6 +10,7 @@ import android.view.ViewGroup;
 import com.wireguard.android.R;
 import com.wireguard.android.databinding.TunnelDetailFragmentBinding;
 import com.wireguard.android.model.Tunnel;
+import com.wireguard.config.Config;
 
 /**
  * Fragment that shows details about a specific tunnel.
@@ -18,6 +19,7 @@ import com.wireguard.android.model.Tunnel;
 public class TunnelDetailFragment extends BaseFragment {
     private TunnelDetailFragmentBinding binding;
     private boolean isViewStateRestored;
+    private String originalName;
 
     @Override
     public void onCreate(final Bundle savedInstanceState) {
@@ -45,16 +47,34 @@ public class TunnelDetailFragment extends BaseFragment {
         super.onDestroyView();
     }
 
+    private void onConfigLoaded(Config config) {
+        binding.setConfig(new Config.Observable(config, originalName));
+    }
+
     @Override
     public void onSelectedTunnelChanged(final Tunnel oldTunnel, final Tunnel newTunnel) {
-        if (binding != null && isViewStateRestored)
+        if (binding != null && isViewStateRestored) {
             binding.setTunnel(newTunnel);
+            if (newTunnel == null)
+                binding.setConfig(null);
+            else {
+                originalName = newTunnel.getName();
+                newTunnel.getConfigAsync().thenAccept(this::onConfigLoaded);
+            }
+        }
     }
 
     @Override
     public void onViewStateRestored(final Bundle savedInstanceState) {
         super.onViewStateRestored(savedInstanceState);
-        binding.setTunnel(getSelectedTunnel());
+        Tunnel tunnel = getSelectedTunnel();
+        binding.setTunnel(tunnel);
+        if (tunnel == null)
+            binding.setConfig(null);
+        else {
+            originalName = tunnel.getName();
+            tunnel.getConfigAsync().thenAccept(this::onConfigLoaded);
+        }
         isViewStateRestored = true;
     }
 }