implement notification click handler

app/src/main/java/chat/rocket/android/activity/AbstractAuthedActivity.java

 package chat.rocket.android.activity;
 
+import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Bundle;
+import android.support.annotation.Nullable;
 import chat.rocket.android.LaunchUtil;
 import chat.rocket.android.RocketChatCache;
 import chat.rocket.android.model.ServerConfig;
@@ -34,6 +36,25 @@ abstract class AbstractAuthedActivity extends AbstractFragmentActivity {
         }
       };
 
+  @Override protected void onCreate(@Nullable Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    if (savedInstanceState == null) {
+      Intent intent = getIntent();
+      if (intent != null) {
+        if (intent.hasExtra("serverConfigId")) {
+          SharedPreferences.Editor editor = RocketChatCache.get(this).edit();
+          editor.putString(RocketChatCache.KEY_SELECTED_SERVER_CONFIG_ID,
+              intent.getStringExtra("serverConfigId"));
+
+          if (intent.hasExtra("roomId")) {
+            editor.putString(RocketChatCache.KEY_SELECTED_ROOM_ID, intent.getStringExtra("roomId"));
+          }
+          editor.apply();
+        }
+      }
+    }
+  }
+
   private void updateServerConfigIdIfNeeded(SharedPreferences prefs) {
     String newServerConfigId = prefs.getString(RocketChatCache.KEY_SELECTED_SERVER_CONFIG_ID, null);
     if (serverConfigId == null) {

app/src/main/java/chat/rocket/android/notification/StreamNotifyUserNotifier.java

 package chat.rocket.android.notification;
 
 import android.app.Notification;
+import android.app.PendingIntent;
 import android.content.Context;
+import android.content.Intent;
 import android.graphics.Bitmap;
 import android.support.v4.app.NotificationCompat;
 import android.support.v4.app.NotificationManagerCompat;
 import android.support.v4.content.ContextCompat;
 import bolts.Task;
 import chat.rocket.android.R;
+import chat.rocket.android.activity.MainActivity;
 import chat.rocket.android.helper.Avatar;
+import chat.rocket.android.model.ServerConfig;
+import chat.rocket.android.realm_helper.RealmStore;
+import org.json.JSONException;
 import org.json.JSONObject;
 
 /**
@@ -71,12 +77,28 @@ public class StreamNotifyUserNotifier implements Notifier {
   }
 
   private Notification generateNotification(Bitmap largeIcon) {
+    Intent intent = new Intent(context, MainActivity.class);
+    intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT | Intent.FLAG_ACTIVITY_CLEAR_TOP);
+    ServerConfig config = RealmStore.getDefault().executeTransactionForRead(realm ->
+      realm.where(ServerConfig.class).equalTo("hostname", hostname).findFirst());
+    if (config != null) {
+      intent.putExtra("serverConfigId", config.getServerConfigId());
+      try {
+        intent.putExtra("roomId", payload.getString("rid"));
+      } catch (JSONException exception) {
+      }
+    }
+    PendingIntent pendingIntent = PendingIntent.getActivity(context.getApplicationContext(),
+        (int) (System.currentTimeMillis() % Integer.MAX_VALUE),
+        intent, PendingIntent.FLAG_ONE_SHOT);
+
     NotificationCompat.Builder builder = new NotificationCompat.Builder(context)
         .setContentTitle(title)
         .setContentText(text)
         .setAutoCancel(true)
         .setColor(ContextCompat.getColor(context, R.color.colorPrimary))
-        .setSmallIcon(R.drawable.rocket_chat_notification_24dp);
+        .setSmallIcon(R.drawable.rocket_chat_notification_24dp)
+        .setContentIntent(pendingIntent);
     if (largeIcon != null) {
       builder.setLargeIcon(largeIcon);
     }