func ReadEmptyTests(p metric.Persistence, t test.Tester) {
	hasLabelPair := func(x int) (success bool) {
		fingerprints, err := p.GetFingerprintsForLabelMatchers(metric.LabelMatchers{{
			Type:  metric.Equal,
			Name:  clientmodel.LabelName(string(x)),
			Value: clientmodel.LabelValue(string(x)),
		}})
		if err != nil {
			t.Error(err)
			return
		}

		success = len(fingerprints) == 0
		if !success {
			t.Errorf("unexpected fingerprint length %d, got %d", 0, len(fingerprints))
		}

		return
	}

	err := quick.Check(hasLabelPair, nil)
	if err != nil {
		t.Error(err)
		return
	}

	hasLabelName := func(x int) (success bool) {
		labelName := clientmodel.LabelName(string(x))

		values, err := p.GetLabelValuesForLabelName(labelName)
		if err != nil {
			t.Error(err)
			return
		}

		success = len(values) == 0
		if !success {
			t.Errorf("unexpected values length %d, got %d", 0, len(values))
		}

		return
	}

	err = quick.Check(hasLabelName, nil)
	if err != nil {
		t.Error(err)
		return
	}
}

func AppendSampleAsPureSparseAppendTests(p metric.Persistence, t test.Tester) {
	appendSample := func(x int) (success bool) {
		v := clientmodel.SampleValue(x)
		ts := clientmodel.TimestampFromUnix(int64(x))
		labelName := clientmodel.LabelName(x)
		labelValue := clientmodel.LabelValue(x)
		l := clientmodel.Metric{labelName: labelValue}

		sample := &clientmodel.Sample{
			Value:     v,
			Timestamp: ts,
			Metric:    l,
		}

		err := p.AppendSamples(clientmodel.Samples{sample})

		success = err == nil
		if !success {
			t.Error(err)
		}

		return
	}

	if err := quick.Check(appendSample, nil); err != nil {
		t.Error(err)
	}
}

func (s *testNotificationScenario) test(i int, t *testing.T) {
	h := NewNotificationHandler(&NotificationHandlerOptions{
		AlertmanagerURL: "alertmanager_url",
		QueueCapacity:   0,
		Deadline:        10 * time.Second,
	})
	defer h.Stop()

	receivedPost := make(chan bool, 1)
	poster := testHTTPPoster{receivedPost: receivedPost}
	h.httpClient = &poster

	go h.Run()

	h.SubmitReqs(NotificationReqs{
		{
			Summary:     s.summary,
			Description: s.description,
			Labels: clientmodel.LabelSet{
				clientmodel.LabelName("instance"): clientmodel.LabelValue("testinstance"),
			},
			Value:        clientmodel.SampleValue(1.0 / 3.0),
			ActiveSince:  time.Time{},
			RuleString:   "Test rule string",
			GeneratorURL: "prometheus_url",
		},
	})

	<-receivedPost
	if poster.message != s.message {
		t.Fatalf("%d. Expected '%s', received '%s'", i, s.message, poster.message)
	}
}

func (s *testNotificationScenario) test(i int, t *testing.T) {
	notifications := make(chan NotificationReqs)
	defer close(notifications)
	h := NewNotificationHandler("alertmanager_url", notifications)

	receivedPost := make(chan bool, 1)
	poster := testHttpPoster{receivedPost: receivedPost}
	h.httpClient = &poster

	go h.Run()

	notifications <- NotificationReqs{
		{
			Summary:     s.summary,
			Description: s.description,
			Labels: clientmodel.LabelSet{
				clientmodel.LabelName("instance"): clientmodel.LabelValue("testinstance"),
			},
			Value:        clientmodel.SampleValue(1.0 / 3.0),
			ActiveSince:  time.Time{},
			RuleString:   "Test rule string",
			GeneratorUrl: "prometheus_url",
		},
	}

	<-receivedPost
	if poster.message != s.message {
		t.Fatalf("%d. Expected '%s', received '%s'", i, s.message, poster.message)
	}
}

func parseServersetMember(data []byte, path string) (*clientmodel.LabelSet, error) {
	member := serversetMember{}
	err := json.Unmarshal(data, &member)
	if err != nil {
		return nil, fmt.Errorf("error unmarshaling serverset member %q: %s", path, err)
	}

	labels := clientmodel.LabelSet{}
	labels[serversetPathLabel] = clientmodel.LabelValue(path)
	labels[clientmodel.AddressLabel] = clientmodel.LabelValue(
		fmt.Sprintf("%s:%d", member.ServiceEndpoint.Host, member.ServiceEndpoint.Port))

	labels[serversetEndpointLabelPrefix+"_host"] = clientmodel.LabelValue(member.ServiceEndpoint.Host)
	labels[serversetEndpointLabelPrefix+"_port"] = clientmodel.LabelValue(fmt.Sprintf("%d", member.ServiceEndpoint.Port))

	for name, endpoint := range member.AdditionalEndpoints {
		cleanName := clientmodel.LabelName(invalidLabelCharRE.ReplaceAllString(name, "_"))
		labels[serversetEndpointLabelPrefix+"_host_"+cleanName] = clientmodel.LabelValue(
			endpoint.Host)
		labels[serversetEndpointLabelPrefix+"_port_"+cleanName] = clientmodel.LabelValue(
			fmt.Sprintf("%d", endpoint.Port))

	}

	labels[serversetStatusLabel] = clientmodel.LabelValue(member.Status)

	return &labels, nil
}

func extractCounter(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error {
	samples := make(model.Samples, 0, len(f.Metric))

	for _, m := range f.Metric {
		if m.Counter == nil {
			continue
		}

		sample := new(model.Sample)
		samples = append(samples, sample)

		if m.TimestampMs != nil {
			sample.Timestamp = model.TimestampFromUnix(*m.TimestampMs / 1000)
		} else {
			sample.Timestamp = o.Timestamp
		}
		sample.Metric = model.Metric{}
		metric := sample.Metric

		for _, p := range m.Label {
			metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
		}

		metric[model.MetricNameLabel] = model.LabelValue(f.GetName())

		sample.Value = model.SampleValue(m.Counter.GetValue())
	}

	return out.Ingest(&Result{Samples: samples})
}

func extractUntyped(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error {
	samples := make(model.Samples, 0, len(f.Metric))

	for _, m := range f.Metric {
		if m.Untyped == nil {
			continue
		}

		sample := &model.Sample{
			Metric: model.Metric{},
			Value:  model.SampleValue(m.Untyped.GetValue()),
		}
		samples = append(samples, sample)

		if m.TimestampMs != nil {
			sample.Timestamp = model.TimestampFromUnixNano(*m.TimestampMs * 1000000)
		} else {
			sample.Timestamp = o.Timestamp
		}

		metric := sample.Metric
		for _, p := range m.Label {
			metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
		}
		metric[model.MetricNameLabel] = model.LabelValue(f.GetName())
	}

	return out.Ingest(samples)
}

func dumpMetric(d *dto.Metric, m clientmodel.Metric) {
	d.Reset()

	metricLength := len(m)
	labelNames := make([]string, 0, metricLength)

	for labelName := range m {
		labelNames = append(labelNames, string(labelName))
	}

	sort.Strings(labelNames)

	pairs := make([]*dto.LabelPair, 0, metricLength)

	for _, labelName := range labelNames {
		l := clientmodel.LabelName(labelName)
		labelValue := m[l]
		labelPair := &dto.LabelPair{
			Name:  proto.String(string(labelName)),
			Value: proto.String(string(labelValue)),
		}

		pairs = append(pairs, labelPair)
	}

	d.LabelPair = pairs
}

func (m *targetManager) AddTargetsFromConfig(config config.Config) {
	for _, job := range config.Jobs() {
		if job.SdName != nil {
			m.Lock()
			m.targetPoolForJob(job)
			m.Unlock()
			continue
		}

		for _, targetGroup := range job.TargetGroup {
			baseLabels := clientmodel.LabelSet{
				clientmodel.JobLabel: clientmodel.LabelValue(job.GetName()),
			}
			if targetGroup.Labels != nil {
				for _, label := range targetGroup.Labels.Label {
					baseLabels[clientmodel.LabelName(label.GetName())] = clientmodel.LabelValue(label.GetValue())
				}
			}

			for _, endpoint := range targetGroup.Target {
				target := NewTarget(endpoint, job.ScrapeTimeout(), baseLabels)
				m.AddTarget(job, target)
			}
		}
	}
}

// Helper function to convert map[string]string into LabelSet.
//
// NOTE: This should be deleted when support for go 1.0.3 is removed; 1.1 is
//       smart enough to unmarshal JSON objects into LabelSet directly.
func labelSet(labels map[string]string) model.LabelSet {
	labelset := make(model.LabelSet, len(labels))

	for k, v := range labels {
		labelset[model.LabelName(k)] = model.LabelValue(v)
	}

	return labelset
}

// Return the global labels as a LabelSet.
func (c Config) GlobalLabels() clientmodel.LabelSet {
	labels := clientmodel.LabelSet{}
	if c.Global.Labels != nil {
		for _, label := range c.Global.Labels.Label {
			labels[clientmodel.LabelName(label.GetName())] = clientmodel.LabelValue(label.GetValue())
		}
	}
	return labels
}

// === label_replace(vector ExprVector, dst_label, replacement, src_labelname, regex ExprString) Vector ===
func funcLabelReplace(ev *evaluator, args Expressions) Value {
	var (
		vector   = ev.evalVector(args[0])
		dst      = clientmodel.LabelName(ev.evalString(args[1]).Value)
		repl     = ev.evalString(args[2]).Value
		src      = clientmodel.LabelName(ev.evalString(args[3]).Value)
		regexStr = ev.evalString(args[4]).Value
	)

	regex, err := regexp.Compile(regexStr)
	if err != nil {
		ev.errorf("invalid regular expression in label_replace(): %s", regexStr)
	}
	if !clientmodel.LabelNameRE.MatchString(string(dst)) {
		ev.errorf("invalid destination label name in label_replace(): %s", dst)
	}

	outSet := make(map[clientmodel.Fingerprint]struct{}, len(vector))
	for _, el := range vector {
		srcVal := string(el.Metric.Metric[src])
		indexes := regex.FindStringSubmatchIndex(srcVal)
		// If there is no match, no replacement should take place.
		if indexes == nil {
			continue
		}
		res := regex.ExpandString([]byte{}, repl, srcVal, indexes)
		if len(res) == 0 {
			el.Metric.Delete(dst)
		} else {
			el.Metric.Set(dst, clientmodel.LabelValue(res))
		}

		fp := el.Metric.Metric.Fingerprint()
		if _, exists := outSet[fp]; exists {
			ev.errorf("duplicated label set in output of label_replace(): %s", el.Metric.Metric)
		} else {
			outSet[fp] = struct{}{}
		}
	}

	return vector
}

func (api *API) labelValues(r *http.Request) (interface{}, *apiError) {
	name := route.Param(api.context(r), "name")

	if !clientmodel.LabelNameRE.MatchString(name) {
		return nil, &apiError{errorBadData, fmt.Errorf("invalid label name: %q", name)}
	}
	vals := api.Storage.LabelValuesForLabelName(clientmodel.LabelName(name))
	sort.Sort(vals)

	return vals, nil
}

func AppendSampleAsSparseAppendWithReadsTests(p metric.Persistence, t test.Tester) {
	appendSample := func(x int) (success bool) {
		v := clientmodel.SampleValue(x)
		ts := clientmodel.TimestampFromUnix(int64(x))
		labelName := clientmodel.LabelName(x)
		labelValue := clientmodel.LabelValue(x)
		l := clientmodel.Metric{labelName: labelValue}

		sample := &clientmodel.Sample{
			Value:     v,
			Timestamp: ts,
			Metric:    l,
		}

		err := p.AppendSamples(clientmodel.Samples{sample})
		if err != nil {
			t.Error(err)
			return
		}

		values, err := p.GetLabelValuesForLabelName(labelName)
		if err != nil {
			t.Error(err)
			return
		}
		if len(values) != 1 {
			t.Errorf("expected label values count of %d, got %d", 1, len(values))
			return
		}

		fingerprints, err := p.GetFingerprintsForLabelMatchers(metric.LabelMatchers{{
			Type:  metric.Equal,
			Name:  labelName,
			Value: labelValue,
		}})
		if err != nil {
			t.Error(err)
			return
		}
		if len(fingerprints) != 1 {
			t.Errorf("expected fingerprint count of %d, got %d", 1, len(fingerprints))
			return
		}

		return true
	}

	if err := quick.Check(appendSample, nil); err != nil {
		t.Error(err)
	}
}

func (kd *KubernetesDiscovery) updateServiceTargetGroup(service *Service, endpoints *Endpoints) *config.TargetGroup {
	tg := &config.TargetGroup{
		Source: serviceSource(service),
		Labels: clientmodel.LabelSet{
			serviceNamespaceLabel: clientmodel.LabelValue(service.ObjectMeta.Namespace),
			serviceNameLabel:      clientmodel.LabelValue(service.ObjectMeta.Name),
		},
	}

	for k, v := range service.ObjectMeta.Labels {
		labelName := strutil.SanitizeLabelName(serviceLabelPrefix + k)
		tg.Labels[clientmodel.LabelName(labelName)] = clientmodel.LabelValue(v)
	}

	for k, v := range service.ObjectMeta.Annotations {
		labelName := strutil.SanitizeLabelName(serviceAnnotationPrefix + k)
		tg.Labels[clientmodel.LabelName(labelName)] = clientmodel.LabelValue(v)
	}

	// Now let's loop through the endpoints & add them to the target group with appropriate labels.
	for _, eps := range endpoints.Subsets {
		epPort := eps.Ports[0].Port

		for _, addr := range eps.Addresses {
			ipAddr := addr.IP
			if len(ipAddr) == net.IPv6len {
				ipAddr = "[" + ipAddr + "]"
			}
			address := fmt.Sprintf("%s:%d", ipAddr, epPort)

			t := clientmodel.LabelSet{clientmodel.AddressLabel: clientmodel.LabelValue(address)}

			tg.Targets = append(tg.Targets, t)
		}
	}

	return tg
}

// UnmarshalBinary implements encoding.BinaryUnmarshaler.
func (lp *LabelPair) UnmarshalBinary(buf []byte) error {
	r := bytes.NewReader(buf)
	n, err := decodeString(r)
	if err != nil {
		return err
	}
	v, err := decodeString(r)
	if err != nil {
		return err
	}
	lp.Name = clientmodel.LabelName(n)
	lp.Value = clientmodel.LabelValue(v)
	return nil
}

func relabel(labels clientmodel.LabelSet, cfg *config.RelabelConfig) (clientmodel.LabelSet, error) {
	values := make([]string, 0, len(cfg.SourceLabels))
	for _, ln := range cfg.SourceLabels {
		values = append(values, string(labels[ln]))
	}
	val := strings.Join(values, cfg.Separator)

	switch cfg.Action {
	case config.RelabelDrop:
		if cfg.Regex.MatchString(val) {
			return nil, nil
		}
	case config.RelabelKeep:
		if !cfg.Regex.MatchString(val) {
			return nil, nil
		}
	case config.RelabelReplace:
		indexes := cfg.Regex.FindStringSubmatchIndex(val)
		// If there is no match no replacement must take place.
		if indexes == nil {
			break
		}
		res := cfg.Regex.ExpandString([]byte{}, cfg.Replacement, val, indexes)
		if len(res) == 0 {
			delete(labels, cfg.TargetLabel)
		} else {
			labels[cfg.TargetLabel] = clientmodel.LabelValue(res)
		}
	case config.RelabelHashMod:
		mod := sum64(md5.Sum([]byte(val))) % cfg.Modulus
		labels[cfg.TargetLabel] = clientmodel.LabelValue(fmt.Sprintf("%d", mod))
	case config.RelabelLabelMap:
		out := make(clientmodel.LabelSet, len(labels))
		// Take a copy to avoid infinite loops.
		for ln, lv := range labels {
			out[ln] = lv
		}
		for ln, lv := range labels {
			if cfg.Regex.MatchString(string(ln)) {
				res := cfg.Regex.ReplaceAllString(string(ln), cfg.Replacement)
				out[clientmodel.LabelName(res)] = lv
			}
		}
		labels = out
	default:
		panic(fmt.Errorf("retrieval.relabel: unknown relabel action type %q", cfg.Action))
	}
	return labels, nil
}

// Lookup implements FingerprintMetricIndex.
func (i *LevelDBFingerprintMetricIndex) Lookup(f *clientmodel.Fingerprint) (m clientmodel.Metric, ok bool, err error) {
	k := &dto.Fingerprint{}
	dumpFingerprint(k, f)
	v := &dto.Metric{}
	if ok, err := i.LevelDBPersistence.Get(k, v); !ok {
		return nil, false, nil
	} else if err != nil {
		return nil, false, err
	}

	m = clientmodel.Metric{}

	for _, pair := range v.LabelPair {
		m[clientmodel.LabelName(pair.GetName())] = clientmodel.LabelValue(pair.GetValue())
	}

	return m, true, nil
}

// labels parses a list of labelnames.
//
//		'(' <label_name>, ... ')'
//
func (p *parser) labels() clientmodel.LabelNames {
	const ctx = "grouping opts"

	p.expect(itemLeftParen, ctx)

	labels := clientmodel.LabelNames{}
	for {
		id := p.expect(itemIdentifier, ctx)
		labels = append(labels, clientmodel.LabelName(id.val))

		if p.peek().typ != itemComma {
			break
		}
		p.next()
	}
	p.expect(itemRightParen, ctx)

	return labels
}

// UnmarshalFromReader unmarshals a Metric from a reader that implements
// both, io.Reader and io.ByteReader. It can be used with the zero value of
// Metric.
func (m *Metric) UnmarshalFromReader(r byteReader) error {
	numLabelPairs, err := binary.ReadVarint(r)
	if err != nil {
		return err
	}
	*m = make(Metric, numLabelPairs)

	for ; numLabelPairs > 0; numLabelPairs-- {
		ln, err := decodeString(r)
		if err != nil {
			return err
		}
		lv, err := decodeString(r)
		if err != nil {
			return err
		}
		(*m)[clientmodel.LabelName(ln)] = clientmodel.LabelValue(lv)
	}
	return nil
}