// remove will remove the supplied unit from state. It will panic if it
// observes inconsistent internal state.
func (d *Deployer) remove(unit *apideployer.Unit) error {
	unitName := unit.Name()
	if d.deployed.Contains(unitName) {
		panic("must not remove a deployed unit")
	} else if unit.Life() == params.Alive {
		panic("must not remove an Alive unit")
	}
	logger.Infof("removing unit %q", unitName)
	return unit.Remove()
}

// deploy will deploy the supplied unit with the deployer's manager. It will
// panic if it observes inconsistent internal state.
func (d *Deployer) deploy(unit *apideployer.Unit) error {
	unitName := unit.Name()
	if d.deployed.Contains(unit.Name()) {
		panic("must not re-deploy a deployed unit")
	}
	if err := unit.SetStatus(status.Waiting, status.MessageInstallingAgent, nil); err != nil {
		return errors.Trace(err)
	}
	logger.Infof("deploying unit %q", unitName)
	initialPassword, err := utils.RandomPassword()
	if err != nil {
		return err
	}
	if err := unit.SetPassword(initialPassword); err != nil {
		return fmt.Errorf("cannot set password for unit %q: %v", unitName, err)
	}
	if err := d.ctx.DeployUnit(unitName, initialPassword); err != nil {
		return err
	}
	d.deployed.Add(unitName)
	return nil
}