// Copyright 2024 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.
// Provenance-includes-location: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/95e8f8fdc2a9dc87230406c9a3cf02be4fd68bea/pkg/translator/prometheusremotewrite/otlp_to_openmetrics_metadata.go
// Provenance-includes-license: Apache-2.0
// Provenance-includes-copyright: Copyright The OpenTelemetry Authors.

package prometheusremotewrite

import (
	"go.opentelemetry.io/collector/pdata/pmetric"

	"github.com/prometheus/prometheus/prompb"
	prometheustranslator "github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheus"
)

func otelMetricTypeToPromMetricType(otelMetric pmetric.Metric) prompb.MetricMetadata_MetricType {
	switch otelMetric.Type() {
	case pmetric.MetricTypeGauge:
		return prompb.MetricMetadata_GAUGE
	case pmetric.MetricTypeSum:
		metricType := prompb.MetricMetadata_GAUGE
		if otelMetric.Sum().IsMonotonic() {
			metricType = prompb.MetricMetadata_COUNTER
		}
		return metricType
	case pmetric.MetricTypeHistogram:
		return prompb.MetricMetadata_HISTOGRAM
	case pmetric.MetricTypeSummary:
		return prompb.MetricMetadata_SUMMARY
	case pmetric.MetricTypeExponentialHistogram:
		return prompb.MetricMetadata_HISTOGRAM
	}
	return prompb.MetricMetadata_UNKNOWN
}

func OtelMetricsToMetadata(md pmetric.Metrics, addMetricSuffixes bool) []*prompb.MetricMetadata {
	resourceMetricsSlice := md.ResourceMetrics()

	metadataLength := 0
	for i := 0; i < resourceMetricsSlice.Len(); i++ {
		scopeMetricsSlice := resourceMetricsSlice.At(i).ScopeMetrics()
		for j := 0; j < scopeMetricsSlice.Len(); j++ {
			metadataLength += scopeMetricsSlice.At(j).Metrics().Len()
		}
	}

	var metadata = make([]*prompb.MetricMetadata, 0, metadataLength)
	for i := 0; i < resourceMetricsSlice.Len(); i++ {
		resourceMetrics := resourceMetricsSlice.At(i)
		scopeMetricsSlice := resourceMetrics.ScopeMetrics()

		for j := 0; j < scopeMetricsSlice.Len(); j++ {
			scopeMetrics := scopeMetricsSlice.At(j)
			for k := 0; k < scopeMetrics.Metrics().Len(); k++ {
				metric := scopeMetrics.Metrics().At(k)
				entry := prompb.MetricMetadata{
					Type:             otelMetricTypeToPromMetricType(metric),
					MetricFamilyName: prometheustranslator.BuildCompliantName(metric, "", addMetricSuffixes),
					Help:             metric.Description(),
				}
				metadata = append(metadata, &entry)
			}
		}
	}

	return metadata
}
