AUTH-2588 add DoH to service mode

overwatch/app_manager.go

@@ -0,0 +1,53 @@
+package overwatch
+
+// AppManager is the default implementation of overwatch service management
+type AppManager struct {
+	services  map[string]Service
+	errorChan chan error
+}
+
+// NewAppManager creates a new overwatch manager
+func NewAppManager(errorChan chan error) Manager {
+	return &AppManager{services: make(map[string]Service), errorChan: errorChan}
+}
+
+// Add takes in a new service to manage.
+// It stops the service if it already exist in the manager and is running
+// It then starts the newly added service
+func (m *AppManager) Add(service Service) {
+	// check for existing service
+	if currentService, ok := m.services[service.Name()]; ok {
+		if currentService.Hash() == service.Hash() {
+			return // the exact same service, no changes, so move along
+		}
+		currentService.Shutdown() //shutdown the listener since a new one is starting
+	}
+	m.services[service.Name()] = service
+
+	//start the service!
+	go m.serviceRun(service)
+}
+
+// Remove shutdowns the service by name and removes it from its current management list
+func (m *AppManager) Remove(name string) {
+	if currentService, ok := m.services[name]; ok {
+		currentService.Shutdown()
+	}
+	delete(m.services, name)
+}
+
+// Services returns all the current Services being managed
+func (m *AppManager) Services() []Service {
+	values := []Service{}
+	for _, value := range m.services {
+		values = append(values, value)
+	}
+	return values
+}
+
+func (m *AppManager) serviceRun(service Service) {
+	err := service.Run()
+	if err != nil && m.errorChan != nil {
+		m.errorChan <- err
+	}
+}