func Parse()

in plugins/inputs/prometheus/parser.go [26:98]
58 lines of code
17 McCabe index (conditional complexity)

func Parse(buf []byte, header http.Header) ([]telegraf.Metric, error) {
	var metrics []telegraf.Metric
	var parser expfmt.TextParser
	// parse even if the buffer begins with a newline
	buf = bytes.TrimPrefix(buf, []byte("\n"))
	// Read raw data
	buffer := bytes.NewBuffer(buf)
	reader := bufio.NewReader(buffer)

	mediatype, params, err := mime.ParseMediaType(header.Get("Content-Type"))
	// Prepare output
	metricFamilies := make(map[string]*dto.MetricFamily)

	if err == nil && mediatype == "application/vnd.google.protobuf" &&
		params["encoding"] == "delimited" &&
		params["proto"] == "io.prometheus.client.MetricFamily" {
		for {
			mf := &dto.MetricFamily{}
			if _, ierr := pbutil.ReadDelimited(reader, mf); ierr != nil {
				if ierr == io.EOF {
					break
				}
				return nil, fmt.Errorf("reading metric family protocol buffer failed: %s", ierr)
			}
			metricFamilies[mf.GetName()] = mf
		}
	} else {
		metricFamilies, err = parser.TextToMetricFamilies(reader)
		if err != nil {
			return nil, fmt.Errorf("reading text format failed: %s", err)
		}
	}

	// read metrics
	for metricName, mf := range metricFamilies {
		for _, m := range mf.Metric {
			// reading tags
			tags := makeLabels(m)
			// reading fields
			fields := make(map[string]interface{})
			if mf.GetType() == dto.MetricType_SUMMARY {
				// summary metric
				fields = makeQuantiles(m)
				fields["count"] = float64(m.GetSummary().GetSampleCount())
				fields["sum"] = float64(m.GetSummary().GetSampleSum())
			} else if mf.GetType() == dto.MetricType_HISTOGRAM {
				// historgram metric
				fields = makeBuckets(m)
				fields["count"] = float64(m.GetHistogram().GetSampleCount())
				fields["sum"] = float64(m.GetHistogram().GetSampleSum())

			} else {
				// standard metric
				fields = getNameAndValue(m)
			}
			// converting to telegraf metric
			if len(fields) > 0 {
				var t time.Time
				if m.TimestampMs != nil && *m.TimestampMs > 0 {
					t = time.Unix(0, *m.TimestampMs*1000000)
				} else {
					t = time.Now()
				}
				metric, err := metric.New(metricName, tags, fields, t)
				if err == nil {
					metrics = append(metrics, metric)
				}
			}
		}
	}

	return metrics, err
}