lib: controller now check for existing registered clients

The server controller now check that there is no client registered for the given
room before creating one.

lib/controller.js

@@ -27,6 +27,10 @@ const create = (runner, modules, config) => {
   const controller = {
     registry: {},
     client: room => {
+      if (room in controller.registry) {
+        return null;
+      }
+
       controller.registry[room] = runner.run(modules,
                                              config.visio.url,
                                              room,

lib/controller.test.js

@@ -48,4 +48,16 @@ describe('controller', () => {
     const client = controller.client('test');
     expect(controller.registry).toHaveProperty('test', client);
   });
+
+  test('should return null when trying to create a client for an existing room', () => {
+    controller.client('test');
+    const client2 = controller.client('test');
+    expect(client2).toBeNull();
+  });
+
+  test('should not replace the client for an existing room', () => {
+    const client1 = controller.client('test');
+    controller.client('test');
+    expect(controller.registry).toHaveProperty('test', client1);
+  });
 });