// Copyright 2013 Prometheus Team
// 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 extraction

import (
	"fmt"
	"io"

	dto "github.com/prometheus/client_model/go"

	"github.com/matttproud/golang_protobuf_extensions/ext"

	"github.com/prometheus/client_golang/model"
)

type metricFamilyProcessor struct{}

// MetricFamilyProcessor decodes varint encoded record length-delimited streams
// of io.prometheus.client.MetricFamily.
//
// See http://godoc.org/github.com/matttproud/golang_protobuf_extensions/ext for
// more details.
var MetricFamilyProcessor = new(metricFamilyProcessor)

func (m *metricFamilyProcessor) ProcessSingle(i io.Reader, out Ingester, o *ProcessOptions) error {
	family := new(dto.MetricFamily)

	for {
		family.Reset()

		if _, err := ext.ReadDelimited(i, family); err != nil {
			if err == io.EOF {
				return nil
			}

			return err
		}

		switch *family.Type {
		case dto.MetricType_COUNTER:
			if err := extractCounter(out, o, family); err != nil {
				return err
			}
		case dto.MetricType_GAUGE:
			if err := extractGauge(out, o, family); err != nil {
				return err
			}
		case dto.MetricType_SUMMARY:
			if err := extractSummary(out, o, family); err != nil {
				return err
			}
		}
	}

	return 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)

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

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

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

		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.Gauge.GetValue())
	}

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

func extractSummary(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error {
	// BUG(matt): Lack of dumping of sum or count.
	samples := make(model.Samples, 0, len(f.Metric))

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

		for _, q := range m.Summary.Quantile {
			sample := new(model.Sample)
			samples = append(samples, sample)

			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())
			}
			// BUG(matt): Update other names to "quantile".
			metric[model.LabelName("quantile")] = model.LabelValue(fmt.Sprint(q.GetQuantile()))

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

			sample.Value = model.SampleValue(q.GetValue())
		}
	}

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