func (s *macOSXVersionSuite) TestOSVersion(c *gc.C) {
	knownSeries := set.Strings{}
	for _, series := range macOSXSeries {
		knownSeries.Add(series)
	}
	c.Check(osVersion(), jc.Satisfies, knownSeries.Contains)
}

// collect calls f on all values in src and returns an alphabetically
// ordered list of the returned results without duplicates.
func (src List) collect(f func(*Tools) string) []string {
	var seen set.Strings
	for _, tools := range src {
		seen.Add(f(tools))
	}
	return seen.SortedValues()
}

func (*statusContext) processRelations(service *state.Service) (related map[string][]string, subord []string, err error) {
	// TODO(mue) This way the same relation is read twice (for each service).
	// Maybe add Relations() to state, read them only once and pass them to each
	// call of this function.
	relations, err := service.Relations()
	if err != nil {
		return nil, nil, err
	}
	var subordSet set.Strings
	related = make(map[string][]string)
	for _, relation := range relations {
		ep, err := relation.Endpoint(service.Name())
		if err != nil {
			return nil, nil, err
		}
		relationName := ep.Relation.Name
		eps, err := relation.RelatedEndpoints(service.Name())
		if err != nil {
			return nil, nil, err
		}
		for _, ep := range eps {
			if ep.Scope == charm.ScopeContainer && !service.IsPrincipal() {
				subordSet.Add(ep.ServiceName)
			}
			related[relationName] = append(related[relationName], ep.ServiceName)
		}
	}
	for relationName, serviceNames := range related {
		sn := set.NewStrings(serviceNames...)
		related[relationName] = sn.SortedValues()
	}
	return related, subordSet.SortedValues(), nil
}

// fetchMachines returns a map from top level machine id to machines, where machines[0] is the host
// machine and machines[1..n] are any containers (including nested ones).
//
// If machineIds is non-nil, only machines whose IDs are in the set are returned.
func fetchMachines(st *state.State, machineIds *set.Strings) (map[string][]*state.Machine, error) {
	v := make(map[string][]*state.Machine)
	machines, err := st.AllMachines()
	if err != nil {
		return nil, err
	}
	// AllMachines gives us machines sorted by id.
	for _, m := range machines {
		if machineIds != nil && !machineIds.Contains(m.Id()) {
			continue
		}
		parentId, ok := m.ParentId()
		if !ok {
			// Only top level host machines go directly into the machine map.
			v[m.Id()] = []*state.Machine{m}
		} else {
			topParentId := state.TopParentId(m.Id())
			machines, ok := v[topParentId]
			if !ok {
				panic(fmt.Errorf("unexpected machine id %q", parentId))
			}
			machines = append(machines, m)
			v[topParentId] = machines
		}
	}
	return v, nil
}

// storeManifest stores, into dataPath, the supplied manifest for the supplied charm.
func (d *manifestDeployer) storeManifest(url *charm.URL, manifest set.Strings) error {
	if err := os.MkdirAll(d.DataPath(manifestsDataPath), 0755); err != nil {
		return err
	}
	name := charm.Quote(url.String())
	path := filepath.Join(d.DataPath(manifestsDataPath), name)
	return utils.WriteYaml(path, manifest.SortedValues())
}

// ParseMetadataFromStorage loads ImageMetadata from the specified storage reader.
func ParseMetadataFromStorage(c *gc.C, stor storage.StorageReader) []*imagemetadata.ImageMetadata {
	source := storage.NewStorageSimpleStreamsDataSource("test storage reader", stor, "images")

	// Find the simplestreams index file.
	params := simplestreams.ValueParams{
		DataType:      "image-ids",
		ValueTemplate: imagemetadata.ImageMetadata{},
	}
	const requireSigned = false
	indexPath := simplestreams.UnsignedIndex
	indexRef, err := simplestreams.GetIndexWithFormat(
		source, indexPath, "index:1.0", requireSigned, simplestreams.CloudSpec{}, params)
	c.Assert(err, gc.IsNil)
	c.Assert(indexRef.Indexes, gc.HasLen, 1)

	imageIndexMetadata := indexRef.Indexes["com.ubuntu.cloud:custom"]
	c.Assert(imageIndexMetadata, gc.NotNil)

	// Read the products file contents.
	r, err := stor.Get(path.Join("images", imageIndexMetadata.ProductsFilePath))
	defer r.Close()
	c.Assert(err, gc.IsNil)
	data, err := ioutil.ReadAll(r)
	c.Assert(err, gc.IsNil)

	// Parse the products file metadata.
	url, err := source.URL(imageIndexMetadata.ProductsFilePath)
	c.Assert(err, gc.IsNil)
	cloudMetadata, err := simplestreams.ParseCloudMetadata(data, "products:1.0", url, imagemetadata.ImageMetadata{})
	c.Assert(err, gc.IsNil)

	// Collate the metadata.
	imageMetadataMap := make(map[string]*imagemetadata.ImageMetadata)
	var expectedProductIds set.Strings
	var imageVersions set.Strings
	for _, mc := range cloudMetadata.Products {
		for _, items := range mc.Items {
			for key, item := range items.Items {
				imageMetadata := item.(*imagemetadata.ImageMetadata)
				imageMetadataMap[key] = imageMetadata
				imageVersions.Add(key)
				productId := fmt.Sprintf("com.ubuntu.cloud:server:%s:%s", mc.Version, imageMetadata.Arch)
				expectedProductIds.Add(productId)
			}
		}
	}

	// Make sure index's product IDs are all represented in the products metadata.
	sort.Strings(imageIndexMetadata.ProductIds)
	c.Assert(imageIndexMetadata.ProductIds, gc.DeepEquals, expectedProductIds.SortedValues())

	imageMetadata := make([]*imagemetadata.ImageMetadata, len(imageMetadataMap))
	for i, key := range imageVersions.SortedValues() {
		imageMetadata[i] = imageMetadataMap[key]
	}
	return imageMetadata
}

// removeDiff removes every path in oldManifest that is not present in newManifest.
func (d *manifestDeployer) removeDiff(oldManifest, newManifest set.Strings) error {
	diff := oldManifest.Difference(newManifest)
	for _, path := range diff.SortedValues() {
		fullPath := filepath.Join(d.charmPath, filepath.FromSlash(path))
		if err := os.RemoveAll(fullPath); err != nil {
			return err
		}
	}
	return nil
}

func (w *minUnitsWatcher) initial() (*set.Strings, error) {
	serviceNames := new(set.Strings)
	doc := &minUnitsDoc{}
	iter := w.st.minUnits.Find(nil).Iter()
	for iter.Next(doc) {
		w.known[doc.ServiceName] = doc.Revno
		serviceNames.Add(doc.ServiceName)
	}
	return serviceNames, iter.Err()
}

func mergedAddresses(machineAddresses, providerAddresses []address) []instance.Address {
	merged := make([]instance.Address, len(providerAddresses), len(providerAddresses)+len(machineAddresses))
	var providerValues set.Strings
	for i, address := range providerAddresses {
		providerValues.Add(address.Value)
		merged[i] = address.InstanceAddress()
	}
	for _, address := range machineAddresses {
		if !providerValues.Contains(address.Value) {
			merged = append(merged, address.InstanceAddress())
		}
	}
	return merged
}

func (w *minUnitsWatcher) merge(serviceNames *set.Strings, change watcher.Change) error {
	serviceName := change.Id.(string)
	if change.Revno == -1 {
		delete(w.known, serviceName)
		serviceNames.Remove(serviceName)
		return nil
	}
	doc := minUnitsDoc{}
	if err := w.st.minUnits.FindId(serviceName).One(&doc); err != nil {
		return err
	}
	revno, known := w.known[serviceName]
	w.known[serviceName] = doc.Revno
	if !known || doc.Revno > revno {
		serviceNames.Add(serviceName)
	}
	return nil
}

// fetchUnitMachineIds returns a set of IDs for machines that
// the specified units reside on, and those machines' ancestors.
func fetchUnitMachineIds(units map[string]map[string]*state.Unit) (*set.Strings, error) {
	machineIds := new(set.Strings)
	for _, svcUnitMap := range units {
		for _, unit := range svcUnitMap {
			if !unit.IsPrincipal() {
				continue
			}
			mid, err := unit.AssignedMachineId()
			if err != nil {
				return nil, err
			}
			for mid != "" {
				machineIds.Add(mid)
				mid = state.ParentId(mid)
			}
		}
	}
	return machineIds, nil
}

// commonServiceInstances returns instances with
// services in common with the specified machine.
func commonServiceInstances(st *state.State, m *state.Machine) ([]instance.Id, error) {
	units, err := m.Units()
	if err != nil {
		return nil, err
	}
	var instanceIdSet set.Strings
	for _, unit := range units {
		if !unit.IsPrincipal() {
			continue
		}
		service, err := unit.Service()
		if err != nil {
			return nil, err
		}
		allUnits, err := service.AllUnits()
		if err != nil {
			return nil, err
		}
		for _, unit := range allUnits {
			machineId, err := unit.AssignedMachineId()
			if state.IsNotAssigned(err) {
				continue
			} else if err != nil {
				return nil, err
			}
			machine, err := st.Machine(machineId)
			if err != nil {
				return nil, err
			}
			instanceId, err := machine.InstanceId()
			if err == nil {
				instanceIdSet.Add(string(instanceId))
			} else if state.IsNotProvisionedError(err) {
				continue
			} else {
				return nil, err
			}
		}
	}
	instanceIds := make([]instance.Id, instanceIdSet.Size())
	// Sort values to simplify testing.
	for i, instanceId := range instanceIdSet.SortedValues() {
		instanceIds[i] = instance.Id(instanceId)
	}
	return instanceIds, nil
}

// Helper methods for the tests.
func AssertValues(c *gc.C, s set.Strings, expected ...string) {
	values := s.Values()
	// Expect an empty slice, not a nil slice for values.
	if expected == nil {
		expected = []string{}
	}
	sort.Strings(expected)
	sort.Strings(values)
	c.Assert(values, gc.DeepEquals, expected)
	c.Assert(s.Size(), gc.Equals, len(expected))
	// Check the sorted values too.
	sorted := s.SortedValues()
	c.Assert(sorted, gc.DeepEquals, expected)
}

func (stringSetSuite) TestUninitialized(c *gc.C) {
	var uninitialized set.Strings
	c.Assert(uninitialized.Size(), gc.Equals, 0)
	c.Assert(uninitialized.IsEmpty(), gc.Equals, true)
	// You can get values and sorted values from an unitialized set.
	AssertValues(c, uninitialized)
	// All contains checks are false
	c.Assert(uninitialized.Contains("foo"), gc.Equals, false)
	// Remove works on an uninitialized Strings
	uninitialized.Remove("foo")

	var other set.Strings
	// Union returns a new set that is empty but initialized.
	c.Assert(uninitialized.Union(other), gc.DeepEquals, set.NewStrings())
	c.Assert(uninitialized.Intersection(other), gc.DeepEquals, set.NewStrings())
	c.Assert(uninitialized.Difference(other), gc.DeepEquals, set.NewStrings())

	other = set.NewStrings("foo", "bar")
	c.Assert(uninitialized.Union(other), gc.DeepEquals, other)
	c.Assert(uninitialized.Intersection(other), gc.DeepEquals, set.NewStrings())
	c.Assert(uninitialized.Difference(other), gc.DeepEquals, set.NewStrings())
	c.Assert(other.Union(uninitialized), gc.DeepEquals, other)
	c.Assert(other.Intersection(uninitialized), gc.DeepEquals, set.NewStrings())
	c.Assert(other.Difference(uninitialized), gc.DeepEquals, other)

	// Once something is added, the set becomes initialized.
	uninitialized.Add("foo")
	AssertValues(c, uninitialized, "foo")
}

// ParseMetadataFromStorage loads ToolsMetadata from the specified storage reader.
func ParseMetadataFromStorage(c *gc.C, stor storage.StorageReader, expectMirrors bool) []*tools.ToolsMetadata {
	source := storage.NewStorageSimpleStreamsDataSource("test storage reader", stor, "tools")
	params := simplestreams.ValueParams{
		DataType:      tools.ContentDownload,
		ValueTemplate: tools.ToolsMetadata{},
	}

	const requireSigned = false
	indexPath := simplestreams.UnsignedIndex
	indexRef, err := simplestreams.GetIndexWithFormat(
		source, indexPath, "index:1.0", requireSigned, simplestreams.CloudSpec{}, params)
	c.Assert(err, gc.IsNil)
	c.Assert(indexRef.Indexes, gc.HasLen, 1)

	toolsIndexMetadata := indexRef.Indexes["com.ubuntu.juju:released:tools"]
	c.Assert(toolsIndexMetadata, gc.NotNil)

	// Read the products file contents.
	r, err := stor.Get(path.Join("tools", toolsIndexMetadata.ProductsFilePath))
	defer r.Close()
	c.Assert(err, gc.IsNil)
	data, err := ioutil.ReadAll(r)
	c.Assert(err, gc.IsNil)

	url, err := source.URL(toolsIndexMetadata.ProductsFilePath)
	c.Assert(err, gc.IsNil)
	cloudMetadata, err := simplestreams.ParseCloudMetadata(data, "products:1.0", url, tools.ToolsMetadata{})
	c.Assert(err, gc.IsNil)

	toolsMetadataMap := make(map[string]*tools.ToolsMetadata)
	var expectedProductIds set.Strings
	var toolsVersions set.Strings
	for _, mc := range cloudMetadata.Products {
		for _, items := range mc.Items {
			for key, item := range items.Items {
				toolsMetadata := item.(*tools.ToolsMetadata)
				toolsMetadataMap[key] = toolsMetadata
				toolsVersions.Add(key)
				seriesVersion, err := ubuntu.SeriesVersion(toolsMetadata.Release)
				c.Assert(err, gc.IsNil)
				productId := fmt.Sprintf("com.ubuntu.juju:%s:%s", seriesVersion, toolsMetadata.Arch)
				expectedProductIds.Add(productId)
			}
		}
	}

	// Make sure index's product IDs are all represented in the products metadata.
	sort.Strings(toolsIndexMetadata.ProductIds)
	c.Assert(toolsIndexMetadata.ProductIds, gc.DeepEquals, expectedProductIds.SortedValues())

	toolsMetadata := make([]*tools.ToolsMetadata, len(toolsMetadataMap))
	for i, key := range toolsVersions.SortedValues() {
		toolsMetadata[i] = toolsMetadataMap[key]
	}

	if expectMirrors {
		r, err = stor.Get(path.Join("tools", simplestreams.UnsignedMirror))
		defer r.Close()
		c.Assert(err, gc.IsNil)
		data, err = ioutil.ReadAll(r)
		c.Assert(err, gc.IsNil)
		c.Assert(string(data), jc.Contains, `"mirrors":`)
		c.Assert(err, gc.IsNil)
	}
	return toolsMetadata
}