// 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 exporterhelper

import (
	"context"
	"errors"

	"go.opentelemetry.io/collector/component"
	"go.opentelemetry.io/collector/config"
	"go.opentelemetry.io/collector/consumer"
	"go.opentelemetry.io/collector/consumer/consumererror"
	"go.opentelemetry.io/collector/consumer/consumerhelper"
	"go.opentelemetry.io/collector/model/otlp"
	"go.opentelemetry.io/collector/model/pdata"
)

var metricsMarshaler = otlp.NewProtobufMetricsMarshaler()
var metricsUnmarshaler = otlp.NewProtobufMetricsUnmarshaler()

type metricsRequest struct {
	baseRequest
	md     pdata.Metrics
	pusher consumerhelper.ConsumeMetricsFunc
}

func newMetricsRequest(ctx context.Context, md pdata.Metrics, pusher consumerhelper.ConsumeMetricsFunc) request {
	return &metricsRequest{
		baseRequest: baseRequest{ctx: ctx},
		md:          md,
		pusher:      pusher,
	}
}

func newMetricsRequestUnmarshalerFunc(pusher consumerhelper.ConsumeMetricsFunc) requestUnmarshaler {
	return func(bytes []byte) (request, error) {
		metrics, err := metricsUnmarshaler.UnmarshalMetrics(bytes)
		if err != nil {
			return nil, err
		}
		return newMetricsRequest(context.Background(), metrics, pusher), nil
	}
}

func (req *metricsRequest) onError(err error) request {
	var metricsError consumererror.Metrics
	if consumererror.AsMetrics(err, &metricsError) {
		return newMetricsRequest(req.ctx, metricsError.GetMetrics(), req.pusher)
	}
	return req
}

func (req *metricsRequest) export(ctx context.Context) error {
	return req.pusher(ctx, req.md)
}

func (req *metricsRequest) marshal() ([]byte, error) {
	return metricsMarshaler.MarshalMetrics(req.md)
}

func (req *metricsRequest) count() int {
	return req.md.DataPointCount()
}

type metricsExporter struct {
	*baseExporter
	consumer.Metrics
}

// NewMetricsExporter creates an MetricsExporter that records observability metrics and wraps every request with a Span.
func NewMetricsExporter(
	cfg config.Exporter,
	set component.ExporterCreateSettings,
	pusher consumerhelper.ConsumeMetricsFunc,
	options ...Option,
) (component.MetricsExporter, error) {
	if cfg == nil {
		return nil, errNilConfig
	}

	if set.Logger == nil {
		return nil, errNilLogger
	}

	if pusher == nil {
		return nil, errNilPushMetricsData
	}

	bs := fromOptions(options...)
	be := newBaseExporter(cfg, set, bs, config.MetricsDataType, newMetricsRequestUnmarshalerFunc(pusher))
	be.wrapConsumerSender(func(nextSender requestSender) requestSender {
		return &metricsSenderWithObservability{
			obsrep:     be.obsrep,
			nextSender: nextSender,
		}
	})

	mc, err := consumerhelper.NewMetrics(func(ctx context.Context, md pdata.Metrics) error {
		req := newMetricsRequest(ctx, md, pusher)
		err := be.sender.send(req)
		if errors.Is(err, errSendingQueueIsFull) {
			be.obsrep.recordMetricsEnqueueFailure(req.context(), req.count())
		}
		return err
	}, bs.consumerOptions...)

	return &metricsExporter{
		baseExporter: be,
		Metrics:      mc,
	}, err
}

type metricsSenderWithObservability struct {
	obsrep     *obsExporter
	nextSender requestSender
}

func (mewo *metricsSenderWithObservability) send(req request) error {
	req.setContext(mewo.obsrep.StartMetricsOp(req.context()))
	err := mewo.nextSender.send(req)
	mewo.obsrep.EndMetricsOp(req.context(), req.count(), err)
	return err
}
