// startUnit creates a new data value for tracking details of the unit
// The provided machineTag must be the tag for the machine the unit was last
// observed to be assigned to.
func (fw *Firewaller) startUnit(unit *firewaller.Unit, machineTag names.MachineTag) error {
	service, err := unit.Service()
	if err != nil {
		return err
	}
	serviceTag := service.Tag()
	unitTag := unit.Tag()
	if err != nil {
		return err
	}
	unitd := &unitData{
		fw:   fw,
		unit: unit,
		tag:  unitTag,
	}
	fw.unitds[unitTag] = unitd

	unitd.machined = fw.machineds[machineTag]
	unitd.machined.unitds[unitTag] = unitd
	if fw.serviceds[serviceTag] == nil {
		err := fw.startService(service)
		if err != nil {
			delete(fw.unitds, unitTag)
			return err
		}
	}
	unitd.serviced = fw.serviceds[serviceTag]
	unitd.serviced.unitds[unitTag] = unitd

	m, err := unitd.machined.machine()
	if err != nil {
		return err
	}

	// check if the machine has ports open on any networks
	networkTags, err := m.ActiveNetworks()
	if err != nil {
		return errors.Annotatef(err, "failed getting %q active networks", machineTag)
	}
	for _, networkTag := range networkTags {
		err := fw.openedPortsChanged(machineTag, networkTag)
		if err != nil {
			return err
		}
	}

	return nil
}

// startUnit creates a new data value for tracking details of the unit
// The provided machineTag must be the tag for the machine the unit was last
// observed to be assigned to.
func (fw *Firewaller) startUnit(unit *firewaller.Unit, machineTag names.MachineTag) error {
	application, err := unit.Application()
	if err != nil {
		return err
	}
	applicationTag := application.Tag()
	unitTag := unit.Tag()
	if err != nil {
		return err
	}
	unitd := &unitData{
		fw:   fw,
		unit: unit,
		tag:  unitTag,
	}
	fw.unitds[unitTag] = unitd

	unitd.machined = fw.machineds[machineTag]
	unitd.machined.unitds[unitTag] = unitd
	if fw.applicationids[applicationTag] == nil {
		err := fw.startService(application)
		if err != nil {
			delete(fw.unitds, unitTag)
			return err
		}
	}
	unitd.serviced = fw.applicationids[applicationTag]
	unitd.serviced.unitds[unitTag] = unitd

	m, err := unitd.machined.machine()
	if err != nil {
		return err
	}

	// check if the machine has ports open on any subnets
	subnetTags, err := m.ActiveSubnets()
	if err != nil {
		return errors.Annotatef(err, "failed getting %q active subnets", machineTag)
	}
	for _, subnetTag := range subnetTags {
		err := fw.openedPortsChanged(machineTag, subnetTag)
		if err != nil {
			return err
		}
	}

	return nil
}

// startUnit creates a new data value for tracking details of the unit
// and starts watching the unit for port changes. The provided
// machineTag must be the tag for the machine the unit was last
// observed to be assigned to.
func (fw *Firewaller) startUnit(unit *apifirewaller.Unit, machineTag string) error {
	service, err := unit.Service()
	if err != nil {
		return err
	}
	serviceName := service.Name()
	unitName := unit.Name()
	openedPorts, err := unit.OpenedPorts()
	if err != nil {
		return err
	}
	unitd := &unitData{
		fw:    fw,
		unit:  unit,
		ports: openedPorts,
	}
	fw.unitds[unitName] = unitd

	unitd.machined = fw.machineds[machineTag]
	unitd.machined.unitds[unitName] = unitd
	if fw.serviceds[serviceName] == nil {
		err := fw.startService(service)
		if err != nil {
			delete(fw.unitds, unitName)
			return err
		}
	}
	unitd.serviced = fw.serviceds[serviceName]
	unitd.serviced.unitds[unitName] = unitd

	ports := make([]network.Port, len(unitd.ports))
	copy(ports, unitd.ports)

	go unitd.watchLoop(ports)
	return nil
}