Events controller

[joelrebel]

Events controller abstracts the NATS JS, KV interaction for workqueue specific controllers.
This offloads all the boiler plate for NATS config and events, KV interaction from controllers.

Callers create a new controller instance with the required parameters,

nc := controller.NewNatsController(
	"flasher",
	facilityCode,
	"firmwareInstall",
	natsURL,
	natsCreds,
	"firmwareInstall",
	controller.WithConcurrency(10),
	controller.WithKVReplicas(1),
	controller.WithLogger(flasher.Logger),
	controller.WithConnectionTimeout(connectTimeout),
)

connect,

if err := nc.Connect(ctx); err != nil {
	flasher.Logger.Fatal(err)
}

register an event handler factory method and listen for events,

handlerFactory := func() controller.ConditionHandler {
	return &ConditionTaskHandler{
		store:          repository,
		syncWG:         &sync.WaitGroup{},
		logger:         logger,
		dryrun:         dryrun,
		faultInjection: faultInjection,
		facilityCode:   nc.FacilityCode(),
		controllerID:   nc.ID(),
	}
}

if err := nc.ListenEvents(ctx, handlerFactory); err != nil {
	logger.Fatal(err)
}

a functional implementation is here metal-toolbox/flasher#144

[DoctorVin]

A few comments. Apologies for the delay in getting this reviewed.

[DoctorVin]

I'm not really a fan of the factory idiom here. n.conditionHandler could be a function pointer (the equivalent of what is allocated from the factory).

[DoctorVin]

There's a need for offline discussion but this is functional now and can be revised later.