// Parse command and flags and infer resource, action, href and params
func (a *Api) ParseCommandAndFlags(cmd, hrefPrefix string, values ActionCommands) (*CommandTarget, []string, error) {
	resource, vars, err := a.parseResource(cmd, hrefPrefix, values)
	if err != nil {
		return nil, nil, err
	}
	var action *metadata.Action
	elems := strings.Split(cmd, " ")
	actionName := elems[len(elems)-1]
	for _, a := range resource.Actions {
		if a.Name == actionName {
			action = a
			break
		}
	}
	if action == nil {
		supported := make([]string, len(resource.Actions))
		for i, a := range resource.Actions {
			supported[i] = a.Name
		}
		return nil, nil, fmt.Errorf("Unknown %s action '%s'. Supported actions are: %s",
			resource.Name, actionName, strings.Join(supported, ", "))
	}

	path, err := action.Url(vars)
	if err != nil {
		return nil, nil, err
	}
	flags := values[cmd]

	return &CommandTarget{resource, action, path, flags.Href}, flags.Params, nil
}

// IdentifyParams organizes the given params in two groups: the payload params and the query params.
func IdentifyParams(a *metadata.Action, params APIParams) (payloadParams APIParams, queryParams APIParams) {
	payloadParamNames := a.PayloadParamNames()
	payloadParams = make(APIParams)
	for _, n := range payloadParamNames {
		if p, ok := params[n]; ok {
			payloadParams[n] = p
		}
	}
	queryParamNames := a.QueryParamNames()
	queryParams = make(APIParams)
	for _, n := range queryParamNames {
		if p, ok := params[n]; ok {
			queryParams[n] = p
		}
	}
	return payloadParams, queryParams
}

// ActionPath computes the path to the given resource action. For example given the href
// "/api/servers/123" calling ActionPath with resource "servers" and action "clone" returns the path
// "/api/servers/123/clone" and verb POST.
// The algorithm consists of extracting the variables from the href by looking up a matching
// pattern from the resource metadata. The variables are then substituted in the action path.
// If there are more than one pattern that match the href then the algorithm picks the one that can
// substitute the most variables.
func (r *Href) ActionPath(rName, aName string) (*metadata.ActionPath, error) {
	res, ok := GenMetadata[rName]
	if !ok {
		return nil, fmt.Errorf("No resource with name '%s'", rName)
	}
	var action *metadata.Action
	for _, a := range res.Actions {
		if a.Name == aName {
			action = a
			break
		}
	}
	if action == nil {
		return nil, fmt.Errorf("No action with name '%s' on %s", aName, rName)
	}
	vars, err := res.ExtractVariables(string(*r))
	if err != nil {
		return nil, err
	}
	return action.Url(vars)
}

			It("returns an empty string and the unmatched variables", func() {
				Ω(path).Should(BeEmpty())
				Ω(names).Should(Equal([]string{"d"}))
			})
		})
	})

	Context("Action Url", func() {
		var (
			// In
			action    *metadata.Action
			variables []*metadata.PathVariable

			// Out
			url string
			err error

			// Test data
			prefix = "/a/path/pattern/with/one/"
			p1     = &metadata.PathPattern{"GET", prefix + "%s", []string{"a"}, nil}
			p2     = &metadata.PathPattern{"GET", "%s%s", []string{"a", "b"}, nil}
			a      = metadata.PathVariable{"a", "1"}
			b      = metadata.PathVariable{"b", "2"}
		)

		JustBeforeEach(func() {
			var p *metadata.ActionPath
			p, err = action.Url(variables)
			if err == nil {
				url = p.Path
			}
		})

			It("returns an empty string and the unmatched variables", func() {
				Ω(path).Should(BeEmpty())
				Ω(names).Should(Equal([]string{"d"}))
			})
		})
	})

	Context("Action Url", func() {
		var (
			// In
			action    *metadata.Action
			variables []*metadata.PathVariable

			// Out
			url string
			err error

			// Test data
			prefix = "/a/path/pattern/with/one/"
			p1     = &metadata.PathPattern{"GET", prefix + "%s", []string{"a"}, nil}
			p2     = &metadata.PathPattern{"GET", "%s%s", []string{"a", "b"}, nil}
			a      = metadata.PathVariable{"a", "1"}
			b      = metadata.PathVariable{"b", "2"}
		)

		JustBeforeEach(func() {
			var p *metadata.ActionPath
			p, err = action.URL(variables)
			if err == nil {
				url = p.Path
			}
		})