// Copyright 2023 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package fmtutil

import (
	"fmt"
	"io"
	"sort"
	"time"

	dto "github.com/prometheus/client_model/go"
	"github.com/prometheus/common/expfmt"
	"github.com/prometheus/common/model"

	"github.com/prometheus/prometheus/prompb"
)

var MetricMetadataTypeValue = map[string]int32{
	"UNKNOWN":        0,
	"COUNTER":        1,
	"GAUGE":          2,
	"HISTOGRAM":      3,
	"GAUGEHISTOGRAM": 4,
	"SUMMARY":        5,
	"INFO":           6,
	"STATESET":       7,
}

// FormatMetrics convert metric family to a writerequest.
func FormatMetrics(mf map[string]*dto.MetricFamily, extraLabels map[string]string) (*prompb.WriteRequest, error) {
	wr := &prompb.WriteRequest{}

	// build metric list
	sortedMetricNames := make([]string, 0, len(mf))
	for metric := range mf {
		sortedMetricNames = append(sortedMetricNames, metric)
	}
	// sort metrics name in lexicographical order
	sort.Strings(sortedMetricNames)

	for _, metricName := range sortedMetricNames {
		// Set metadata writerequest
		mtype := MetricMetadataTypeValue[mf[metricName].Type.String()]
		metadata := prompb.MetricMetadata{
			MetricFamilyName: mf[metricName].GetName(),
			Type:             prompb.MetricMetadata_MetricType(mtype),
			Help:             mf[metricName].GetHelp(),
		}
		wr.Metadata = append(wr.Metadata, metadata)

		for _, metric := range mf[metricName].Metric {
			var timeserie prompb.TimeSeries

			// build labels map
			labels := make(map[string]string, len(metric.Label)+len(extraLabels))
			labels[model.MetricNameLabel] = metricName

			// add extra labels
			for key, value := range extraLabels {
				labels[key] = value
			}

			// add metric labels
			for _, label := range metric.Label {
				labelname := label.GetName()
				if labelname == model.JobLabel {
					labelname = fmt.Sprintf("%s%s", model.ExportedLabelPrefix, labelname)
				}
				labels[labelname] = label.GetValue()
			}

			// build labels name list
			sortedLabelNames := make([]string, 0, len(labels))
			for label := range labels {
				sortedLabelNames = append(sortedLabelNames, label)
			}
			// sort labels name in lexicographical order
			sort.Strings(sortedLabelNames)

			for _, label := range sortedLabelNames {
				timeserie.Labels = append(timeserie.Labels, prompb.Label{
					Name:  label,
					Value: labels[label],
				})
			}

			timestamp := metric.GetTimestampMs()
			if timestamp == 0 {
				timestamp = time.Now().UnixNano() / int64(time.Millisecond)
			}

			timeserie.Samples = []prompb.Sample{
				{
					Timestamp: timestamp,
					Value:     getMetricsValue(metric),
				},
			}

			wr.Timeseries = append(wr.Timeseries, timeserie)
		}
	}
	return wr, nil
}

// getMetricsValue return the value of a timeserie without the need to give value type
func getMetricsValue(m *dto.Metric) float64 {
	switch {
	case m.Gauge != nil:
		return m.GetGauge().GetValue()
	case m.Counter != nil:
		return m.GetCounter().GetValue()
	case m.Untyped != nil:
		return m.GetUntyped().GetValue()
	default:
		return 0.
	}
}

// ParseMetricsTextReader consumes an io.Reader and returns the MetricFamily.
func ParseMetricsTextReader(input io.Reader) (map[string]*dto.MetricFamily, error) {
	var parser expfmt.TextParser
	mf, err := parser.TextToMetricFamilies(input)
	if err != nil {
		return nil, err
	}
	return mf, nil
}

// ParseMetricsTextAndFormat return the data in the expected prometheus metrics write request format.
func ParseMetricsTextAndFormat(input io.Reader, labels map[string]string) (*prompb.WriteRequest, error) {
	mf, err := ParseMetricsTextReader(input)
	if err != nil {
		return nil, err
	}
	return FormatMetrics(mf, labels)
}