// Copyright The OpenTelemetry 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 metrics

import (
	"context"

	"go.opentelemetry.io/collector/client"
	"go.opentelemetry.io/collector/config"
	"go.opentelemetry.io/collector/consumer"
	"go.opentelemetry.io/collector/model/otlpgrpc"
	"go.opentelemetry.io/collector/model/pdata"
	"go.opentelemetry.io/collector/obsreport"
)

const (
	dataFormatProtobuf = "protobuf"
	receiverTransport  = "grpc"
)

// Receiver is the type used to handle metrics from OpenTelemetry exporters.
type Receiver struct {
	nextConsumer consumer.Metrics
	obsrecv      *obsreport.Receiver
}

// New creates a new Receiver reference.
func New(id config.ComponentID, nextConsumer consumer.Metrics) *Receiver {
	return &Receiver{
		nextConsumer: nextConsumer,
		obsrecv:      obsreport.NewReceiver(obsreport.ReceiverSettings{ReceiverID: id, Transport: receiverTransport}),
	}
}

// Export implements the service Export metrics func.
func (r *Receiver) Export(ctx context.Context, md pdata.Metrics) (otlpgrpc.MetricsResponse, error) {
	dataPointCount := md.DataPointCount()
	if dataPointCount == 0 {
		return otlpgrpc.NewMetricsResponse(), nil
	}

	if c, ok := client.FromGRPC(ctx); ok {
		ctx = client.NewContext(ctx, c)
	}

	ctx = r.obsrecv.StartMetricsOp(ctx)
	err := r.nextConsumer.ConsumeMetrics(ctx, md)
	r.obsrecv.EndMetricsOp(ctx, dataFormatProtobuf, dataPointCount, err)

	return otlpgrpc.NewMetricsResponse(), err
}
