func parsePlacement(spec string) (*instance.Placement, error) {
	placement, err := instance.ParsePlacement(spec)
	if err == instance.ErrPlacementScopeMissing {
		spec = "env-uuid" + ":" + spec
		placement, err = instance.ParsePlacement(spec)
	}
	if err != nil {
		return nil, errors.Errorf("invalid --to parameter %q", spec)
	}
	return placement, nil
}

func (c *ensureAvailabilityCommand) Init(args []string) error {
	if c.NumStateServers < 0 || (c.NumStateServers%2 != 1 && c.NumStateServers != 0) {
		return fmt.Errorf("must specify a number of state servers odd and non-negative")
	}
	if c.PlacementSpec != "" {
		placementSpecs := strings.Split(c.PlacementSpec, ",")
		c.Placement = make([]string, len(placementSpecs))
		for i, spec := range placementSpecs {
			p, err := instance.ParsePlacement(strings.TrimSpace(spec))
			if err == nil && names.IsContainerMachine(p.Directive) {
				return errors.New("ensure-availability cannot be used with container placement directives")
			}
			if err == nil && p.Scope == instance.MachineScope {
				// Targeting machines is ok.
				c.Placement[i] = p.String()
				continue
			}
			if err != instance.ErrPlacementScopeMissing {
				return fmt.Errorf("unsupported ensure-availability placement directive %q", spec)
			}
			c.Placement[i] = spec
		}
	}
	return cmd.CheckEmpty(args)
}

func (c *BootstrapCommand) Init(args []string) (err error) {
	if len(c.Series) > 0 && !c.UploadTools {
		return fmt.Errorf("--upload-series requires --upload-tools")
	}
	if len(c.seriesOld) > 0 && !c.UploadTools {
		return fmt.Errorf("--series requires --upload-tools")
	}
	if len(c.Series) > 0 && len(c.seriesOld) > 0 {
		return fmt.Errorf("--upload-series and --series can't be used together")
	}
	if len(c.seriesOld) > 0 {
		c.Series = c.seriesOld
	}

	// Parse the placement directive. Bootstrap currently only
	// supports provider-specific placement directives.
	if c.Placement != "" {
		_, err = instance.ParsePlacement(c.Placement)
		if err != instance.ErrPlacementScopeMissing {
			// We only support unscoped placement directives for bootstrap.
			return fmt.Errorf("unsupported bootstrap placement directive %q", c.Placement)
		}
	}
	return cmd.CheckEmpty(args)
}

func (c *bootstrapCommand) Init(args []string) (err error) {
	if c.showClouds && c.showRegionsForCloud != "" {
		return errors.New("--clouds and --regions can't be used together")
	}
	if c.showClouds {
		return cmd.CheckEmpty(args)
	}
	if c.showRegionsForCloud != "" {
		return cmd.CheckEmpty(args)
	}
	if c.AgentVersionParam != "" && c.BuildAgent {
		return errors.New("--agent-version and --build-agent can't be used together")
	}
	if c.BootstrapSeries != "" && !charm.IsValidSeries(c.BootstrapSeries) {
		return errors.NotValidf("series %q", c.BootstrapSeries)
	}

	// Parse the placement directive. Bootstrap currently only
	// supports provider-specific placement directives.
	if c.Placement != "" {
		_, err = instance.ParsePlacement(c.Placement)
		if err != instance.ErrPlacementScopeMissing {
			// We only support unscoped placement directives for bootstrap.
			return errors.Errorf("unsupported bootstrap placement directive %q", c.Placement)
		}
	}
	if !c.AutoUpgrade {
		// With no auto upgrade chosen, we default to the version matching the bootstrap client.
		vers := jujuversion.Current
		c.AgentVersion = &vers
	}
	if c.AgentVersionParam != "" {
		if vers, err := version.ParseBinary(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers.Number
		} else if vers, err := version.Parse(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers
		} else {
			return err
		}
	}
	if c.AgentVersion != nil && (c.AgentVersion.Major != jujuversion.Current.Major || c.AgentVersion.Minor != jujuversion.Current.Minor) {
		return errors.New("requested agent version major.minor mismatch")
	}

	switch len(args) {
	case 0:
		// no args or flags, go interactive.
		c.interactive = true
		return nil
	}
	c.Cloud = args[0]
	if i := strings.IndexRune(c.Cloud, '/'); i > 0 {
		c.Cloud, c.Region = c.Cloud[:i], c.Cloud[i+1:]
	}
	if len(args) > 1 {
		c.controllerName = args[1]
		return cmd.CheckEmpty(args[2:])
	}
	return nil
}

func (c *bootstrapCommand) Init(args []string) (err error) {
	if c.AgentVersionParam != "" && c.UploadTools {
		return fmt.Errorf("--agent-version and --upload-tools can't be used together")
	}
	if c.BootstrapSeries != "" && !charm.IsValidSeries(c.BootstrapSeries) {
		return errors.NotValidf("series %q", c.BootstrapSeries)
	}
	if c.BootstrapImage != "" {
		if c.BootstrapSeries == "" {
			return errors.Errorf("--bootstrap-image must be used with --bootstrap-series")
		}
		cons, err := constraints.Merge(c.Constraints, c.BootstrapConstraints)
		if err != nil {
			return errors.Trace(err)
		}
		if !cons.HasArch() {
			return errors.Errorf("--bootstrap-image must be used with --bootstrap-constraints, specifying architecture")
		}
	}

	// Parse the placement directive. Bootstrap currently only
	// supports provider-specific placement directives.
	if c.Placement != "" {
		_, err = instance.ParsePlacement(c.Placement)
		if err != instance.ErrPlacementScopeMissing {
			// We only support unscoped placement directives for bootstrap.
			return fmt.Errorf("unsupported bootstrap placement directive %q", c.Placement)
		}
	}
	if !c.AutoUpgrade {
		// With no auto upgrade chosen, we default to the version matching the bootstrap client.
		vers := jujuversion.Current
		c.AgentVersion = &vers
	}
	if c.AgentVersionParam != "" {
		if vers, err := version.ParseBinary(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers.Number
		} else if vers, err := version.Parse(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers
		} else {
			return err
		}
	}
	if c.AgentVersion != nil && (c.AgentVersion.Major != jujuversion.Current.Major || c.AgentVersion.Minor != jujuversion.Current.Minor) {
		return fmt.Errorf("requested agent version major.minor mismatch")
	}

	// The user must specify two positional arguments: the controller name,
	// and the cloud name (optionally with region specified).
	if len(args) < 2 {
		return errors.New("controller name and cloud name are required")
	}
	c.controllerName = bootstrappedControllerName(args[0])
	c.Cloud = args[1]
	if i := strings.IndexRune(c.Cloud, '/'); i > 0 {
		c.Cloud, c.Region = c.Cloud[:i], c.Cloud[i+1:]
	}
	return cmd.CheckEmpty(args[2:])
}

func (c *AddMachineCommand) Init(args []string) error {
	if c.Constraints.Container != nil {
		return fmt.Errorf("container constraint %q not allowed when adding a machine", *c.Constraints.Container)
	}
	placement, err := cmd.ZeroOrOneArgs(args)
	if err != nil {
		return err
	}
	c.Placement, err = instance.ParsePlacement(placement)
	if err == instance.ErrPlacementScopeMissing {
		placement = c.EnvName + ":" + placement
		c.Placement, err = instance.ParsePlacement(placement)
	}
	if err != nil {
		return err
	}
	return nil
}

func (c *addCommand) Init(args []string) error {
	if c.Constraints.Container != nil {
		return fmt.Errorf("container constraint %q not allowed when adding a machine", *c.Constraints.Container)
	}
	placement, err := cmd.ZeroOrOneArgs(args)
	if err != nil {
		return err
	}
	c.Placement, err = instance.ParsePlacement(placement)
	if err == instance.ErrPlacementScopeMissing {
		placement = "model-uuid" + ":" + placement
		c.Placement, err = instance.ParsePlacement(placement)
	}
	if err != nil {
		return err
	}
	if c.NumMachines > 1 && c.Placement != nil && c.Placement.Directive != "" {
		return fmt.Errorf("cannot use -n when specifying a placement directive")
	}
	return nil
}

func (c *bootstrapCommand) Init(args []string) (err error) {
	if c.AgentVersionParam != "" && c.UploadTools {
		return fmt.Errorf("--agent-version and --upload-tools can't be used together")
	}
	if c.BootstrapSeries != "" && !charm.IsValidSeries(c.BootstrapSeries) {
		return errors.NotValidf("series %q", c.BootstrapSeries)
	}
	if c.BootstrapImage != "" {
		if c.BootstrapSeries == "" {
			return errors.Errorf("--bootstrap-image must be used with --bootstrap-series")
		}
		cons, err := constraints.Merge(c.Constraints, c.BootstrapConstraints)
		if err != nil {
			return errors.Trace(err)
		}
		if !cons.HasArch() {
			return errors.Errorf("--bootstrap-image must be used with --bootstrap-constraints, specifying architecture")
		}
	}

	// Parse the placement directive. Bootstrap currently only
	// supports provider-specific placement directives.
	if c.Placement != "" {
		_, err = instance.ParsePlacement(c.Placement)
		if err != instance.ErrPlacementScopeMissing {
			// We only support unscoped placement directives for bootstrap.
			return fmt.Errorf("unsupported bootstrap placement directive %q", c.Placement)
		}
	}
	if !c.AutoUpgrade {
		// With no auto upgrade chosen, we default to the version matching the bootstrap client.
		vers := version.Current
		c.AgentVersion = &vers
	}
	if c.AgentVersionParam != "" {
		if vers, err := version.ParseBinary(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers.Number
		} else if vers, err := version.Parse(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers
		} else {
			return err
		}
	}
	if c.AgentVersion != nil && (c.AgentVersion.Major != version.Current.Major || c.AgentVersion.Minor != version.Current.Minor) {
		return fmt.Errorf("requested agent version major.minor mismatch")
	}
	return cmd.CheckEmpty(args)
}

func (c *BootstrapCommand) Init(args []string) (err error) {
	if len(c.Series) > 0 && !c.UploadTools {
		return fmt.Errorf("--upload-series requires --upload-tools")
	}
	if len(c.seriesOld) > 0 && !c.UploadTools {
		return fmt.Errorf("--series requires --upload-tools")
	}
	if len(c.Series) > 0 && len(c.seriesOld) > 0 {
		return fmt.Errorf("--upload-series and --series can't be used together")
	}
	if c.AgentVersionParam != "" && c.UploadTools {
		return fmt.Errorf("--agent-version and --upload-tools can't be used together")
	}
	if c.AgentVersionParam != "" && c.NoAutoUpgrade {
		return fmt.Errorf("--agent-version and --no-auto-upgrade can't be used together")
	}

	// Parse the placement directive. Bootstrap currently only
	// supports provider-specific placement directives.
	if c.Placement != "" {
		_, err = instance.ParsePlacement(c.Placement)
		if err != instance.ErrPlacementScopeMissing {
			// We only support unscoped placement directives for bootstrap.
			return fmt.Errorf("unsupported bootstrap placement directive %q", c.Placement)
		}
	}
	if c.NoAutoUpgrade {
		vers := version.Current.Number
		c.AgentVersion = &vers
	} else if c.AgentVersionParam != "" {
		if vers, err := version.ParseBinary(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers.Number
		} else if vers, err := version.Parse(c.AgentVersionParam); err == nil {
			c.AgentVersion = &vers
		} else {
			return err
		}
	}
	if c.AgentVersion != nil && (c.AgentVersion.Major != version.Current.Major || c.AgentVersion.Minor != version.Current.Minor) {
		return fmt.Errorf("requested agent version major.minor mismatch")
	}
	return cmd.CheckEmpty(args)
}

func (f *fakeHAClient) EnsureAvailability(numStateServers int, cons constraints.Value,
	series string, placement []string) (params.StateServersChanges, error) {

	f.numStateServers = numStateServers
	f.cons = cons
	f.series = series
	f.placement = placement

	if f.err != nil {
		return f.result, f.err
	}

	if numStateServers == 1 {
		return f.result, nil
	}

	// In the real HAClient, specifying a numStateServers value of 0
	// indicates that the default value (3) should be used
	if numStateServers == 0 {
		numStateServers = 3
	}

	f.result.Maintained = append(f.result.Maintained, "machine-0")

	for _, p := range placement {
		m, err := instance.ParsePlacement(p)
		if err == nil && m.Scope == instance.MachineScope {
			f.result.Converted = append(f.result.Converted, "machine-"+m.Directive)
		}
	}

	// We may need to pretend that we added some machines.
	for i := len(f.result.Converted) + 1; i < numStateServers; i++ {
		f.result.Added = append(f.result.Added, fmt.Sprintf("machine-%d", i))
	}

	return f.result, nil
}

// ensureAvailabilityIntentions returns what we would like
// to do to maintain the availability of the existing servers
// mentioned in the given info, including:
//   demoting unavailable, voting machines;
//   removing unavailable, non-voting, non-vote-holding machines;
//   gathering available, non-voting machines that may be promoted;
func (st *State) ensureAvailabilityIntentions(info *StateServerInfo, placement []string) (*ensureAvailabilityIntent, error) {
	var intent ensureAvailabilityIntent
	for _, s := range placement {
		// TODO(natefinch): unscoped placements shouldn't ever get here (though
		// they do currently).  We should fix up the CLI to always add a scope
		// to placements and then we can remove the need to deal with unscoped
		// placements.
		p, err := instance.ParsePlacement(s)
		if err == instance.ErrPlacementScopeMissing {
			intent.placement = append(intent.placement, s)
			continue
		}
		if err == nil && p.Scope == instance.MachineScope {
			// TODO(natefinch) add env provider policy to check if conversion is
			// possible (e.g. cannot be supported by Azure in HA mode).

			if names.IsContainerMachine(p.Directive) {
				return nil, errors.New("container placement directives not supported")
			}

			m, err := st.Machine(p.Directive)
			if err != nil {
				return nil, errors.Annotatef(err, "can't find machine for placement directive %q", s)
			}
			if m.IsManager() {
				return nil, errors.Errorf("machine for placement directive %q is already a state server", s)
			}
			intent.convert = append(intent.convert, m)
			intent.placement = append(intent.placement, s)
			continue
		}
		return nil, errors.Errorf("unsupported placement directive %q", s)
	}

	for _, mid := range info.MachineIds {
		m, err := st.Machine(mid)
		if err != nil {
			return nil, err
		}
		available, err := stateServerAvailable(m)
		if err != nil {
			return nil, err
		}
		logger.Infof("machine %q, available %v, wants vote %v, has vote %v", m, available, m.WantsVote(), m.HasVote())
		if available {
			if m.WantsVote() {
				intent.maintain = append(intent.maintain, m)
			} else {
				intent.promote = append(intent.promote, m)
			}
			continue
		}
		if m.WantsVote() {
			// The machine wants to vote, so we simply set novote and allow it
			// to run its course to have its vote removed by the worker that
			// maintains the replicaset. We will replace it with an existing
			// non-voting state server if there is one, starting a new one if
			// not.
			intent.demote = append(intent.demote, m)
		} else if m.HasVote() {
			// The machine still has a vote, so keep it around for now.
			intent.maintain = append(intent.maintain, m)
		} else {
			// The machine neither wants to nor has a vote, so remove its
			// JobManageEnviron job immediately.
			intent.remove = append(intent.remove, m)
		}
	}
	logger.Infof("initial intentions: promote %v; maintain %v; demote %v; remove %v; convert: %v",
		intent.promote, intent.maintain, intent.demote, intent.remove, intent.convert)
	return &intent, nil
}

func (s *PlacementSuite) TestParsePlacement(c *gc.C) {
	parsePlacementTests := []struct {
		arg                          string
		expectScope, expectDirective string
		err                          string
	}{{
		arg: "",
	}, {
		arg:             "0",
		expectScope:     instance.MachineScope,
		expectDirective: "0",
	}, {
		arg:             "0/lxc/0",
		expectScope:     instance.MachineScope,
		expectDirective: "0/lxc/0",
	}, {
		arg: "#:x",
		err: `invalid value "x" for "#" scope: expected machine-id`,
	}, {
		arg: "lxc:x",
		err: `invalid value "x" for "lxc" scope: expected machine-id`,
	}, {
		arg: "kvm:x",
		err: `invalid value "x" for "kvm" scope: expected machine-id`,
	}, {
		arg:             "kvm:123",
		expectScope:     string(instance.KVM),
		expectDirective: "123",
	}, {
		arg:         "lxc",
		expectScope: string(instance.LXC),
	}, {
		arg: "non-standard",
		err: "placement scope missing",
	}, {
		arg: ":non-standard",
		err: "placement scope missing",
	}, {
		arg:             "non:standard",
		expectScope:     "non",
		expectDirective: "standard",
	}}

	for i, t := range parsePlacementTests {
		c.Logf("test %d: %s", i, t.arg)
		p, err := instance.ParsePlacement(t.arg)
		if t.err != "" {
			c.Assert(err, gc.ErrorMatches, t.err)
		} else {
			c.Assert(err, jc.ErrorIsNil)
		}
		if t.expectScope == "" && t.expectDirective == "" {
			c.Assert(p, gc.IsNil)
		} else {
			c.Assert(p, gc.DeepEquals, &instance.Placement{
				Scope:     t.expectScope,
				Directive: t.expectDirective,
			})
		}
	}
}