// Init implements Command.Init.
func (c *listCommand) Init(args []string) (err error) {
	c.modelName, err = cmd.ZeroOrOneArgs(args)
	if err != nil {
		return err
	}
	return err
}

func (t *HelpToolCommand) Init(args []string) error {
	tool, err := cmd.ZeroOrOneArgs(args)
	if err == nil {
		t.tool = tool
	}
	return err
}

func (s *CmdSuite) TestZeroOrOneArgs(c *gc.C) {

	expectValue := func(args []string, expected string) {
		arg, err := cmd.ZeroOrOneArgs(args)
		c.Assert(arg, gc.Equals, expected)
		c.Assert(err, gc.IsNil)
	}

	expectValue(nil, "")
	expectValue([]string{}, "")
	expectValue([]string{"foo"}, "foo")

	arg, err := cmd.ZeroOrOneArgs([]string{"foo", "bar"})
	c.Assert(arg, gc.Equals, "")
	c.Assert(err, gc.ErrorMatches, `unrecognized args: \["bar"\]`)
}

// Init implements Command.Init.
func (c *loginCommand) Init(args []string) error {
	var err error
	c.User, err = cmd.ZeroOrOneArgs(args)
	if err != nil {
		return errors.Trace(err)
	}
	return nil
}

func (c *StorageListCommand) Init(args []string) (err error) {
	storageName, err := cmd.ZeroOrOneArgs(args)
	if err != nil {
		return err
	}
	c.storageName = storageName
	return nil
}

// Init implements Command.Init.
func (c *ChangePasswordCommand) Init(args []string) error {
	var err error
	c.User, err = cmd.ZeroOrOneArgs(args)
	if c.User == "" && c.OutPath != "" {
		return errors.New("output is only a valid option when changing another user's password")
	}
	return err
}

func (c *listCredentialsCommand) Init(args []string) error {
	cloudName, err := cmd.ZeroOrOneArgs(args)
	if err != nil {
		return errors.Trace(err)
	}
	c.cloudName = cloudName
	return nil
}

func (c *StorageGetCommand) Init(args []string) error {
	if c.storageTag == (names.StorageTag{}) {
		return errors.New("no storage instance specified")
	}
	key, err := cmd.ZeroOrOneArgs(args)
	if err != nil {
		return err
	}
	c.key = key
	return nil
}

// Init implements Command.Init.
func (c *createCommand) Init(args []string) error {
	notes, err := cmd.ZeroOrOneArgs(args)
	if err != nil {
		return err
	}
	c.Notes = notes

	if c.Filename != notset && c.NoDownload {
		return errors.Errorf("cannot mix --no-download and --filename")
	}
	if c.Filename == "" {
		return errors.Errorf("missing filename")
	}

	return nil
}

// Init implements part of the cmd.Command interface.
func (c *configCommand) Init(args []string) error {
	if c.reset {
		// We're doing resetConfig.
		if len(args) == 0 {
			return errors.New("no keys specified")
		}
		for _, k := range args {
			if k == config.AgentVersionKey {
				return errors.Errorf("agent-version cannot be reset")
			}
		}
		c.keys = args
		c.action = c.resetConfig
		return nil
	}

	if len(args) > 0 && strings.Contains(args[0], "=") {
		// We're setting values.
		options, err := keyvalues.Parse(args, true)
		if err != nil {
			return errors.Trace(err)
		}
		c.values = make(attributes)
		for k, v := range options {
			if k == config.AgentVersionKey {
				return errors.Errorf(`agent-version must be set via "upgrade-juju"`)
			}
			c.values[k] = v
		}

		c.action = c.setConfig
		return nil
	}

	val, err := cmd.ZeroOrOneArgs(args)
	if err != nil {
		return errors.New("can only retrieve a single value, or all values")
	}

	// We're doing getConfig.
	if val != "" {
		c.keys = []string{val}
	}
	c.action = c.getConfig
	return nil
}

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 *SwitchCommand) Init(args []string) (err error) {
	c.EnvName, err = cmd.ZeroOrOneArgs(args)
	return
}

func (c *GetEnvironmentCommand) Init(args []string) (err error) {
	c.key, err = cmd.ZeroOrOneArgs(args)
	return
}

func (c *getCommand) Init(args []string) (err error) {
	c.key, err = cmd.ZeroOrOneArgs(args)
	return
}