// Copyright 2013 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 scrape

import (
	"bytes"
	"context"
	"encoding/binary"
	"testing"

	"github.com/gogo/protobuf/proto"
	dto "github.com/prometheus/client_model/go"
	"github.com/stretchr/testify/require"

	"github.com/prometheus/prometheus/model/histogram"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/storage"
)

type nopAppendable struct{}

func (nopAppendable) AppenderV2(context.Context) storage.AppenderV2 {
	return nopAppender{}
}

type nopAppender struct{}

func (nopAppender) Append(ref storage.SeriesRef, ls labels.Labels, st, t int64, v float64, h *histogram.Histogram, fh *histogram.FloatHistogram, opts storage.AOptions) (storage.SeriesRef, error) {
	return 1, nil
}

func (nopAppender) Commit() error   { return nil }
func (nopAppender) Rollback() error { return nil }

// protoMarshalDelimited marshals a MetricFamily into a delimited
// Prometheus proto exposition format bytes (known as `encoding=delimited`)
//
// See also https://eli.thegreenplace.net/2011/08/02/length-prefix-framing-for-protocol-buffers
func protoMarshalDelimited(t *testing.T, mf *dto.MetricFamily) []byte {
	t.Helper()

	protoBuf, err := proto.Marshal(mf)
	require.NoError(t, err)

	varintBuf := make([]byte, binary.MaxVarintLen32)
	varintLength := binary.PutUvarint(varintBuf, uint64(len(protoBuf)))

	buf := &bytes.Buffer{}
	buf.Write(varintBuf[:varintLength])
	buf.Write(protoBuf)
	return buf.Bytes()
}