// Copyright 2017 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 tsdb

import (
	"context"
	"encoding/binary"
	"errors"
	"fmt"
	"hash/crc32"
	"math/rand"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"testing"

	"github.com/go-kit/log"
	prom_testutil "github.com/prometheus/client_golang/prometheus/testutil"
	"github.com/stretchr/testify/require"

	"github.com/prometheus/prometheus/model/histogram"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/storage"
	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/prometheus/prometheus/tsdb/chunks"
	"github.com/prometheus/prometheus/tsdb/fileutil"
	"github.com/prometheus/prometheus/tsdb/index"
	"github.com/prometheus/prometheus/tsdb/wlog"
)

// In Prometheus 2.1.0 we had a bug where the meta.json version was falsely bumped
// to 2. We had a migration in place resetting it to 1 but we should move immediately to
// version 3 next time to avoid confusion and issues.
func TestBlockMetaMustNeverBeVersion2(t *testing.T) {
	dir := t.TempDir()

	_, err := writeMetaFile(log.NewNopLogger(), dir, &BlockMeta{})
	require.NoError(t, err)

	meta, _, err := readMetaFile(dir)
	require.NoError(t, err)
	require.NotEqual(t, 2, meta.Version, "meta.json version must never be 2")
}

func TestSetCompactionFailed(t *testing.T) {
	tmpdir := t.TempDir()

	blockDir := createBlock(t, tmpdir, genSeries(1, 1, 0, 1))
	b, err := OpenBlock(nil, blockDir, nil)
	require.NoError(t, err)
	require.False(t, b.meta.Compaction.Failed)
	require.NoError(t, b.setCompactionFailed())
	require.True(t, b.meta.Compaction.Failed)
	require.NoError(t, b.Close())

	b, err = OpenBlock(nil, blockDir, nil)
	require.NoError(t, err)
	require.True(t, b.meta.Compaction.Failed)
	require.NoError(t, b.Close())
}

func TestCreateBlock(t *testing.T) {
	tmpdir := t.TempDir()
	b, err := OpenBlock(nil, createBlock(t, tmpdir, genSeries(1, 1, 0, 10)), nil)
	require.NoError(t, err)
	require.NoError(t, b.Close())
}

func BenchmarkOpenBlock(b *testing.B) {
	tmpdir := b.TempDir()
	blockDir := createBlock(b, tmpdir, genSeries(1e6, 20, 0, 10))
	b.Run("benchmark", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			block, err := OpenBlock(nil, blockDir, nil)
			require.NoError(b, err)
			require.NoError(b, block.Close())
		}
	})
}

func TestCorruptedChunk(t *testing.T) {
	for _, tc := range []struct {
		name     string
		corrFunc func(f *os.File) // Func that applies the corruption.
		openErr  error
		iterErr  error
	}{
		{
			name: "invalid header size",
			corrFunc: func(f *os.File) {
				require.NoError(t, f.Truncate(1))
			},
			openErr: errors.New("invalid segment header in segment 0: invalid size"),
		},
		{
			name: "invalid magic number",
			corrFunc: func(f *os.File) {
				magicChunksOffset := int64(0)
				_, err := f.Seek(magicChunksOffset, 0)
				require.NoError(t, err)

				// Set invalid magic number.
				b := make([]byte, chunks.MagicChunksSize)
				binary.BigEndian.PutUint32(b[:chunks.MagicChunksSize], 0x00000000)
				n, err := f.Write(b)
				require.NoError(t, err)
				require.Equal(t, chunks.MagicChunksSize, n)
			},
			openErr: errors.New("invalid magic number 0"),
		},
		{
			name: "invalid chunk format version",
			corrFunc: func(f *os.File) {
				chunksFormatVersionOffset := int64(4)
				_, err := f.Seek(chunksFormatVersionOffset, 0)
				require.NoError(t, err)

				// Set invalid chunk format version.
				b := make([]byte, chunks.ChunksFormatVersionSize)
				b[0] = 0
				n, err := f.Write(b)
				require.NoError(t, err)
				require.Equal(t, chunks.ChunksFormatVersionSize, n)
			},
			openErr: errors.New("invalid chunk format version 0"),
		},
		{
			name: "chunk not enough bytes to read the chunk length",
			corrFunc: func(f *os.File) {
				// Truncate one byte after the segment header.
				require.NoError(t, f.Truncate(chunks.SegmentHeaderSize+1))
			},
			iterErr: errors.New("cannot populate chunk 8 from block 00000000000000000000000000: segment doesn't include enough bytes to read the chunk size data field - required:13, available:9"),
		},
		{
			name: "chunk not enough bytes to read the data",
			corrFunc: func(f *os.File) {
				fi, err := f.Stat()
				require.NoError(t, err)
				require.NoError(t, f.Truncate(fi.Size()-1))
			},
			iterErr: errors.New("cannot populate chunk 8 from block 00000000000000000000000000: segment doesn't include enough bytes to read the chunk - required:26, available:25"),
		},
		{
			name: "checksum mismatch",
			corrFunc: func(f *os.File) {
				fi, err := f.Stat()
				require.NoError(t, err)

				// Get the chunk data end offset.
				chkEndOffset := int(fi.Size()) - crc32.Size

				// Seek to the last byte of chunk data and modify it.
				_, err = f.Seek(int64(chkEndOffset-1), 0)
				require.NoError(t, err)
				n, err := f.Write([]byte("x"))
				require.NoError(t, err)
				require.Equal(t, 1, n)
			},
			iterErr: errors.New("cannot populate chunk 8 from block 00000000000000000000000000: checksum mismatch expected:cfc0526c, actual:34815eae"),
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			tmpdir := t.TempDir()

			series := storage.NewListSeries(labels.FromStrings("a", "b"), []chunks.Sample{sample{1, 1, nil, nil}})
			blockDir := createBlock(t, tmpdir, []storage.Series{series})
			files, err := sequenceFiles(chunkDir(blockDir))
			require.NoError(t, err)
			require.NotEmpty(t, files, "No chunk created.")

			f, err := os.OpenFile(files[0], os.O_RDWR, 0o666)
			require.NoError(t, err)

			// Apply corruption function.
			tc.corrFunc(f)
			require.NoError(t, f.Close())

			// Check open err.
			b, err := OpenBlock(nil, blockDir, nil)
			if tc.openErr != nil {
				require.Equal(t, tc.openErr.Error(), err.Error())
				return
			}
			defer func() { require.NoError(t, b.Close()) }()

			querier, err := NewBlockQuerier(b, 0, 1)
			require.NoError(t, err)
			defer func() { require.NoError(t, querier.Close()) }()
			set := querier.Select(context.Background(), false, nil, labels.MustNewMatcher(labels.MatchEqual, "a", "b"))

			// Check chunk errors during iter time.
			require.True(t, set.Next())
			it := set.At().Iterator(nil)
			require.Equal(t, chunkenc.ValNone, it.Next())
			require.Equal(t, tc.iterErr.Error(), it.Err().Error())
		})
	}
}

func sequenceFiles(dir string) ([]string, error) {
	files, err := os.ReadDir(dir)
	if err != nil {
		return nil, err
	}
	var res []string

	for _, fi := range files {
		if _, err := strconv.ParseUint(fi.Name(), 10, 64); err != nil {
			continue
		}
		res = append(res, filepath.Join(dir, fi.Name()))
	}
	return res, nil
}

func TestLabelValuesWithMatchers(t *testing.T) {
	tmpdir := t.TempDir()
	ctx := context.Background()

	var seriesEntries []storage.Series
	for i := 0; i < 100; i++ {
		seriesEntries = append(seriesEntries, storage.NewListSeries(labels.FromStrings(
			"tens", fmt.Sprintf("value%d", i/10),
			"unique", fmt.Sprintf("value%d", i),
		), []chunks.Sample{sample{100, 0, nil, nil}}))
	}

	blockDir := createBlock(t, tmpdir, seriesEntries)
	files, err := sequenceFiles(chunkDir(blockDir))
	require.NoError(t, err)
	require.NotEmpty(t, files, "No chunk created.")

	// Check open err.
	block, err := OpenBlock(nil, blockDir, nil)
	require.NoError(t, err)
	defer func() { require.NoError(t, block.Close()) }()

	indexReader, err := block.Index()
	require.NoError(t, err)
	defer func() { require.NoError(t, indexReader.Close()) }()

	var uniqueWithout30s []string
	for i := 0; i < 100; i++ {
		if i/10 != 3 {
			uniqueWithout30s = append(uniqueWithout30s, fmt.Sprintf("value%d", i))
		}
	}
	sort.Strings(uniqueWithout30s)
	testCases := []struct {
		name           string
		labelName      string
		matchers       []*labels.Matcher
		expectedValues []string
	}{
		{
			name:           "get tens based on unique id",
			labelName:      "tens",
			matchers:       []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, "unique", "value35")},
			expectedValues: []string{"value3"},
		}, {
			name:           "get unique ids based on a ten",
			labelName:      "unique",
			matchers:       []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, "tens", "value1")},
			expectedValues: []string{"value10", "value11", "value12", "value13", "value14", "value15", "value16", "value17", "value18", "value19"},
		}, {
			name:           "get tens by pattern matching on unique id",
			labelName:      "tens",
			matchers:       []*labels.Matcher{labels.MustNewMatcher(labels.MatchRegexp, "unique", "value[5-7]5")},
			expectedValues: []string{"value5", "value6", "value7"},
		}, {
			name:           "get tens by matching for presence of unique label",
			labelName:      "tens",
			matchers:       []*labels.Matcher{labels.MustNewMatcher(labels.MatchNotEqual, "unique", "")},
			expectedValues: []string{"value0", "value1", "value2", "value3", "value4", "value5", "value6", "value7", "value8", "value9"},
		}, {
			name:      "get unique IDs based on tens not being equal to a certain value, while not empty",
			labelName: "unique",
			matchers: []*labels.Matcher{
				labels.MustNewMatcher(labels.MatchNotEqual, "tens", "value3"),
				labels.MustNewMatcher(labels.MatchNotEqual, "tens", ""),
			},
			expectedValues: uniqueWithout30s,
		},
	}

	for _, tt := range testCases {
		t.Run(tt.name, func(t *testing.T) {
			actualValues, err := indexReader.SortedLabelValues(ctx, tt.labelName, tt.matchers...)
			require.NoError(t, err)
			require.Equal(t, tt.expectedValues, actualValues)

			actualValues, err = indexReader.LabelValues(ctx, tt.labelName, tt.matchers...)
			sort.Strings(actualValues)
			require.NoError(t, err)
			require.Equal(t, tt.expectedValues, actualValues)
		})
	}
}

// TestBlockSize ensures that the block size is calculated correctly.
func TestBlockSize(t *testing.T) {
	tmpdir := t.TempDir()

	var (
		blockInit    *Block
		expSizeInit  int64
		blockDirInit string
		err          error
	)

	// Create a block and compare the reported size vs actual disk size.
	{
		blockDirInit = createBlock(t, tmpdir, genSeries(10, 1, 1, 100))
		blockInit, err = OpenBlock(nil, blockDirInit, nil)
		require.NoError(t, err)
		defer func() {
			require.NoError(t, blockInit.Close())
		}()
		expSizeInit = blockInit.Size()
		actSizeInit, err := fileutil.DirSize(blockInit.Dir())
		require.NoError(t, err)
		require.Equal(t, expSizeInit, actSizeInit)
	}

	// Delete some series and check the sizes again.
	{
		require.NoError(t, blockInit.Delete(context.Background(), 1, 10, labels.MustNewMatcher(labels.MatchRegexp, "", ".*")))
		expAfterDelete := blockInit.Size()
		require.Greater(t, expAfterDelete, expSizeInit, "after a delete the block size should be bigger as the tombstone file should grow %v > %v", expAfterDelete, expSizeInit)
		actAfterDelete, err := fileutil.DirSize(blockDirInit)
		require.NoError(t, err)
		require.Equal(t, expAfterDelete, actAfterDelete, "after a delete reported block size doesn't match actual disk size")

		c, err := NewLeveledCompactor(context.Background(), nil, log.NewNopLogger(), []int64{0}, nil, nil)
		require.NoError(t, err)
		blockDirAfterCompact, err := c.Compact(tmpdir, []string{blockInit.Dir()}, nil)
		require.NoError(t, err)
		blockAfterCompact, err := OpenBlock(nil, filepath.Join(tmpdir, blockDirAfterCompact.String()), nil)
		require.NoError(t, err)
		defer func() {
			require.NoError(t, blockAfterCompact.Close())
		}()
		expAfterCompact := blockAfterCompact.Size()
		actAfterCompact, err := fileutil.DirSize(blockAfterCompact.Dir())
		require.NoError(t, err)
		require.Greater(t, actAfterDelete, actAfterCompact, "after a delete and compaction the block size should be smaller %v,%v", actAfterDelete, actAfterCompact)
		require.Equal(t, expAfterCompact, actAfterCompact, "after a delete and compaction reported block size doesn't match actual disk size")
	}
}

func TestReadIndexFormatV1(t *testing.T) {
	/* The block here was produced at the commit
	    706602daed1487f7849990678b4ece4599745905 used in 2.0.0 with:
	   db, _ := Open("v1db", nil, nil, nil)
	   app := db.Appender()
	   app.Add(labels.FromStrings("foo", "bar"), 1, 2)
	   app.Add(labels.FromStrings("foo", "baz"), 3, 4)
	   app.Add(labels.FromStrings("foo", "meh"), 1000*3600*4, 4) // Not in the block.
	   // Make sure we've enough values for the lack of sorting of postings offsets to show up.
	   for i := 0; i < 100; i++ {
	     app.Add(labels.FromStrings("bar", strconv.FormatInt(int64(i), 10)), 0, 0)
	   }
	   app.Commit()
	   db.compact()
	   db.Close()
	*/

	blockDir := filepath.Join("testdata", "index_format_v1")
	block, err := OpenBlock(nil, blockDir, nil)
	require.NoError(t, err)

	q, err := NewBlockQuerier(block, 0, 1000)
	require.NoError(t, err)
	require.Equal(t, map[string][]chunks.Sample{`{foo="bar"}`: {sample{t: 1, f: 2}}}, query(t, q, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar")))

	q, err = NewBlockQuerier(block, 0, 1000)
	require.NoError(t, err)
	require.Equal(t, map[string][]chunks.Sample{
		`{foo="bar"}`: {sample{t: 1, f: 2}},
		`{foo="baz"}`: {sample{t: 3, f: 4}},
	}, query(t, q, labels.MustNewMatcher(labels.MatchNotRegexp, "foo", "^.?$")))
}

func BenchmarkLabelValuesWithMatchers(b *testing.B) {
	tmpdir := b.TempDir()
	ctx := context.Background()

	var seriesEntries []storage.Series
	metricCount := 1000000
	for i := 0; i < metricCount; i++ {
		// Note these series are not created in sort order: 'value2' sorts after 'value10'.
		// This makes a big difference to the benchmark timing.
		seriesEntries = append(seriesEntries, storage.NewListSeries(labels.FromStrings(
			"a_unique", fmt.Sprintf("value%d", i),
			"b_tens", fmt.Sprintf("value%d", i/(metricCount/10)),
			"c_ninety", fmt.Sprintf("value%d", i/(metricCount/10)/9), // "0" for the first 90%, then "1"
		), []chunks.Sample{sample{100, 0, nil, nil}}))
	}

	blockDir := createBlock(b, tmpdir, seriesEntries)
	files, err := sequenceFiles(chunkDir(blockDir))
	require.NoError(b, err)
	require.NotEmpty(b, files, "No chunk created.")

	// Check open err.
	block, err := OpenBlock(nil, blockDir, nil)
	require.NoError(b, err)
	defer func() { require.NoError(b, block.Close()) }()

	indexReader, err := block.Index()
	require.NoError(b, err)
	defer func() { require.NoError(b, indexReader.Close()) }()

	matchers := []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, "c_ninety", "value0")}

	b.ResetTimer()
	b.ReportAllocs()

	for benchIdx := 0; benchIdx < b.N; benchIdx++ {
		actualValues, err := indexReader.LabelValues(ctx, "b_tens", matchers...)
		require.NoError(b, err)
		require.Len(b, actualValues, 9)
	}
}

func TestLabelNamesWithMatchers(t *testing.T) {
	tmpdir := t.TempDir()
	ctx := context.Background()

	var seriesEntries []storage.Series
	for i := 0; i < 100; i++ {
		seriesEntries = append(seriesEntries, storage.NewListSeries(labels.FromStrings(
			"unique", fmt.Sprintf("value%d", i),
		), []chunks.Sample{sample{100, 0, nil, nil}}))

		if i%10 == 0 {
			seriesEntries = append(seriesEntries, storage.NewListSeries(labels.FromStrings(
				"tens", fmt.Sprintf("value%d", i/10),
				"unique", fmt.Sprintf("value%d", i),
			), []chunks.Sample{sample{100, 0, nil, nil}}))
		}

		if i%20 == 0 {
			seriesEntries = append(seriesEntries, storage.NewListSeries(labels.FromStrings(
				"tens", fmt.Sprintf("value%d", i/10),
				"twenties", fmt.Sprintf("value%d", i/20),
				"unique", fmt.Sprintf("value%d", i),
			), []chunks.Sample{sample{100, 0, nil, nil}}))
		}
	}

	blockDir := createBlock(t, tmpdir, seriesEntries)
	files, err := sequenceFiles(chunkDir(blockDir))
	require.NoError(t, err)
	require.NotEmpty(t, files, "No chunk created.")

	// Check open err.
	block, err := OpenBlock(nil, blockDir, nil)
	require.NoError(t, err)
	t.Cleanup(func() { require.NoError(t, block.Close()) })

	indexReader, err := block.Index()
	require.NoError(t, err)
	t.Cleanup(func() { require.NoError(t, indexReader.Close()) })

	testCases := []struct {
		name          string
		labelName     string
		matchers      []*labels.Matcher
		expectedNames []string
	}{
		{
			name:          "get with non-empty unique: all",
			matchers:      []*labels.Matcher{labels.MustNewMatcher(labels.MatchNotEqual, "unique", "")},
			expectedNames: []string{"tens", "twenties", "unique"},
		}, {
			name:          "get with unique ending in 1: only unique",
			matchers:      []*labels.Matcher{labels.MustNewMatcher(labels.MatchRegexp, "unique", "value.*1")},
			expectedNames: []string{"unique"},
		}, {
			name:          "get with unique = value20: all",
			matchers:      []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, "unique", "value20")},
			expectedNames: []string{"tens", "twenties", "unique"},
		}, {
			name:          "get tens = 1: unique & tens",
			matchers:      []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, "tens", "value1")},
			expectedNames: []string{"tens", "unique"},
		},
	}

	for _, tt := range testCases {
		t.Run(tt.name, func(t *testing.T) {
			actualNames, err := indexReader.LabelNames(ctx, tt.matchers...)
			require.NoError(t, err)
			require.Equal(t, tt.expectedNames, actualNames)
		})
	}
}

func TestBlockIndexReader_PostingsForLabelMatching(t *testing.T) {
	testPostingsForLabelMatching(t, 2, func(t *testing.T, series []labels.Labels) IndexReader {
		var seriesEntries []storage.Series
		for _, s := range series {
			seriesEntries = append(seriesEntries, storage.NewListSeries(s, []chunks.Sample{sample{100, 0, nil, nil}}))
		}

		blockDir := createBlock(t, t.TempDir(), seriesEntries)
		files, err := sequenceFiles(chunkDir(blockDir))
		require.NoError(t, err)
		require.NotEmpty(t, files, "No chunk created.")

		block, err := OpenBlock(nil, blockDir, nil)
		require.NoError(t, err)
		t.Cleanup(func() { require.NoError(t, block.Close()) })

		ir, err := block.Index()
		require.NoError(t, err)
		return ir
	})
}

func testPostingsForLabelMatching(t *testing.T, offset storage.SeriesRef, setUp func(*testing.T, []labels.Labels) IndexReader) {
	t.Helper()

	ctx := context.Background()
	series := []labels.Labels{
		labels.FromStrings("n", "1"),
		labels.FromStrings("n", "1", "i", "a"),
		labels.FromStrings("n", "1", "i", "b"),
		labels.FromStrings("n", "2"),
		labels.FromStrings("n", "2.5"),
	}
	ir := setUp(t, series)
	t.Cleanup(func() {
		require.NoError(t, ir.Close())
	})

	testCases := []struct {
		name      string
		labelName string
		match     func(string) bool
		exp       []storage.SeriesRef
	}{
		{
			name:      "n=1",
			labelName: "n",
			match: func(val string) bool {
				return val == "1"
			},
			exp: []storage.SeriesRef{offset + 1, offset + 2, offset + 3},
		},
		{
			name:      "n=2",
			labelName: "n",
			match: func(val string) bool {
				return val == "2"
			},
			exp: []storage.SeriesRef{offset + 4},
		},
		{
			name:      "missing label",
			labelName: "missing",
			match: func(val string) bool {
				return true
			},
			exp: nil,
		},
	}
	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			p := ir.PostingsForLabelMatching(ctx, tc.labelName, tc.match)
			require.NotNil(t, p)
			srs, err := index.ExpandPostings(p)
			require.NoError(t, err)
			require.Equal(t, tc.exp, srs)
		})
	}
}

// createBlock creates a block with given set of series and returns its dir.
func createBlock(tb testing.TB, dir string, series []storage.Series) string {
	blockDir, err := CreateBlock(series, dir, 0, log.NewNopLogger())
	require.NoError(tb, err)
	return blockDir
}

func createBlockFromHead(tb testing.TB, dir string, head *Head) string {
	compactor, err := NewLeveledCompactor(context.Background(), nil, log.NewNopLogger(), []int64{1000000}, nil, nil)
	require.NoError(tb, err)

	require.NoError(tb, os.MkdirAll(dir, 0o777))

	// Add +1 millisecond to block maxt because block intervals are half-open: [b.MinTime, b.MaxTime).
	// Because of this block intervals are always +1 than the total samples it includes.
	ulid, err := compactor.Write(dir, head, head.MinTime(), head.MaxTime()+1, nil)
	require.NoError(tb, err)
	return filepath.Join(dir, ulid.String())
}

func createBlockFromOOOHead(tb testing.TB, dir string, head *OOOCompactionHead) string {
	compactor, err := NewLeveledCompactor(context.Background(), nil, log.NewNopLogger(), []int64{1000000}, nil, nil)
	require.NoError(tb, err)

	require.NoError(tb, os.MkdirAll(dir, 0o777))

	// Add +1 millisecond to block maxt because block intervals are half-open: [b.MinTime, b.MaxTime).
	// Because of this block intervals are always +1 than the total samples it includes.
	ulid, err := compactor.Write(dir, head, head.MinTime(), head.MaxTime()+1, nil)
	require.NoError(tb, err)
	return filepath.Join(dir, ulid.String())
}

func createHead(tb testing.TB, w *wlog.WL, series []storage.Series, chunkDir string) *Head {
	opts := DefaultHeadOptions()
	opts.ChunkDirRoot = chunkDir
	head, err := NewHead(nil, nil, w, nil, opts, nil)
	require.NoError(tb, err)

	var it chunkenc.Iterator
	ctx := context.Background()
	app := head.Appender(ctx)
	for _, s := range series {
		ref := storage.SeriesRef(0)
		it = s.Iterator(it)
		lset := s.Labels()
		typ := it.Next()
		lastTyp := typ
		for ; typ != chunkenc.ValNone; typ = it.Next() {
			if lastTyp != typ {
				// The behaviour of appender is undefined if samples of different types
				// are appended to the same series in a single Commit().
				require.NoError(tb, app.Commit())
				app = head.Appender(ctx)
			}

			switch typ {
			case chunkenc.ValFloat:
				t, v := it.At()
				ref, err = app.Append(ref, lset, t, v)
			case chunkenc.ValHistogram:
				t, h := it.AtHistogram(nil)
				ref, err = app.AppendHistogram(ref, lset, t, h, nil)
			case chunkenc.ValFloatHistogram:
				t, fh := it.AtFloatHistogram(nil)
				ref, err = app.AppendHistogram(ref, lset, t, nil, fh)
			default:
				err = fmt.Errorf("unknown sample type %s", typ.String())
			}
			require.NoError(tb, err)
			lastTyp = typ
		}
		require.NoError(tb, it.Err())
	}
	require.NoError(tb, app.Commit())
	return head
}

func createHeadWithOOOSamples(tb testing.TB, w *wlog.WL, series []storage.Series, chunkDir string, oooSampleFrequency int) *Head {
	opts := DefaultHeadOptions()
	opts.ChunkDirRoot = chunkDir
	opts.OutOfOrderTimeWindow.Store(10000000000)
	head, err := NewHead(nil, nil, w, nil, opts, nil)
	require.NoError(tb, err)

	oooSampleLabels := make([]labels.Labels, 0, len(series))
	oooSamples := make([]chunks.SampleSlice, 0, len(series))

	var it chunkenc.Iterator
	totalSamples := 0
	app := head.Appender(context.Background())
	for _, s := range series {
		ref := storage.SeriesRef(0)
		it = s.Iterator(it)
		lset := s.Labels()
		os := chunks.SampleSlice{}
		count := 0
		for it.Next() == chunkenc.ValFloat {
			totalSamples++
			count++
			t, v := it.At()
			if count%oooSampleFrequency == 0 {
				os = append(os, sample{t: t, f: v})
				continue
			}
			ref, err = app.Append(ref, lset, t, v)
			require.NoError(tb, err)
		}
		require.NoError(tb, it.Err())
		if len(os) > 0 {
			oooSampleLabels = append(oooSampleLabels, lset)
			oooSamples = append(oooSamples, os)
		}
	}
	require.NoError(tb, app.Commit())

	oooSamplesAppended := 0
	require.Equal(tb, float64(0), prom_testutil.ToFloat64(head.metrics.outOfOrderSamplesAppended))

	app = head.Appender(context.Background())
	for i, lset := range oooSampleLabels {
		ref := storage.SeriesRef(0)
		for _, sample := range oooSamples[i] {
			ref, err = app.Append(ref, lset, sample.T(), sample.F())
			require.NoError(tb, err)
			oooSamplesAppended++
		}
	}
	require.NoError(tb, app.Commit())

	actOOOAppended := prom_testutil.ToFloat64(head.metrics.outOfOrderSamplesAppended)
	require.GreaterOrEqual(tb, actOOOAppended, float64(oooSamplesAppended-len(series)))
	require.LessOrEqual(tb, actOOOAppended, float64(oooSamplesAppended))

	require.Equal(tb, float64(totalSamples), prom_testutil.ToFloat64(head.metrics.samplesAppended))

	return head
}

const (
	defaultLabelName  = "labelName"
	defaultLabelValue = "labelValue"
)

// genSeries generates series of float64 samples with a given number of labels and values.
func genSeries(totalSeries, labelCount int, mint, maxt int64) []storage.Series {
	return genSeriesFromSampleGenerator(totalSeries, labelCount, mint, maxt, 1, func(ts int64) chunks.Sample {
		return sample{t: ts, f: rand.Float64()}
	})
}

// genHistogramSeries generates series of histogram samples with a given number of labels and values.
func genHistogramSeries(totalSeries, labelCount int, mint, maxt, step int64, floatHistogram bool) []storage.Series {
	return genSeriesFromSampleGenerator(totalSeries, labelCount, mint, maxt, step, func(ts int64) chunks.Sample {
		h := &histogram.Histogram{
			Count:         7 + uint64(ts*5),
			ZeroCount:     2 + uint64(ts),
			ZeroThreshold: 0.001,
			Sum:           18.4 * rand.Float64(),
			Schema:        1,
			PositiveSpans: []histogram.Span{
				{Offset: 0, Length: 2},
				{Offset: 1, Length: 2},
			},
			PositiveBuckets: []int64{ts + 1, 1, -1, 0},
		}
		if ts != mint {
			// By setting the counter reset hint to "no counter
			// reset" for all histograms but the first, we cover the
			// most common cases. If the series is manipulated later
			// or spans more than one block when ingested into the
			// storage, the hint has to be adjusted. Note that the
			// storage itself treats this particular hint the same
			// as "unknown".
			h.CounterResetHint = histogram.NotCounterReset
		}
		if floatHistogram {
			return sample{t: ts, fh: h.ToFloat(nil)}
		}
		return sample{t: ts, h: h}
	})
}

// genHistogramAndFloatSeries generates series of mixed histogram and float64 samples with a given number of labels and values.
func genHistogramAndFloatSeries(totalSeries, labelCount int, mint, maxt, step int64, floatHistogram bool) []storage.Series {
	floatSample := false
	count := 0
	return genSeriesFromSampleGenerator(totalSeries, labelCount, mint, maxt, step, func(ts int64) chunks.Sample {
		count++
		var s sample
		if floatSample {
			s = sample{t: ts, f: rand.Float64()}
		} else {
			h := &histogram.Histogram{
				Count:         7 + uint64(ts*5),
				ZeroCount:     2 + uint64(ts),
				ZeroThreshold: 0.001,
				Sum:           18.4 * rand.Float64(),
				Schema:        1,
				PositiveSpans: []histogram.Span{
					{Offset: 0, Length: 2},
					{Offset: 1, Length: 2},
				},
				PositiveBuckets: []int64{ts + 1, 1, -1, 0},
			}
			if count > 1 && count%5 != 1 {
				// Same rationale for this as above in
				// genHistogramSeries, just that we have to be
				// smarter to find out if the previous sample
				// was a histogram, too.
				h.CounterResetHint = histogram.NotCounterReset
			}
			if floatHistogram {
				s = sample{t: ts, fh: h.ToFloat(nil)}
			} else {
				s = sample{t: ts, h: h}
			}
		}

		if count%5 == 0 {
			// Flip the sample type for every 5 samples.
			floatSample = !floatSample
		}

		return s
	})
}

func genSeriesFromSampleGenerator(totalSeries, labelCount int, mint, maxt, step int64, generator func(ts int64) chunks.Sample) []storage.Series {
	if totalSeries == 0 || labelCount == 0 {
		return nil
	}

	series := make([]storage.Series, totalSeries)

	for i := 0; i < totalSeries; i++ {
		lbls := make(map[string]string, labelCount)
		lbls[defaultLabelName] = strconv.Itoa(i)
		for j := 1; len(lbls) < labelCount; j++ {
			lbls[defaultLabelName+strconv.Itoa(j)] = defaultLabelValue + strconv.Itoa(j)
		}
		samples := make([]chunks.Sample, 0, (maxt-mint)/step+1)
		for t := mint; t < maxt; t += step {
			samples = append(samples, generator(t))
		}
		series[i] = storage.NewListSeries(labels.FromMap(lbls), samples)
	}
	return series
}

// populateSeries generates series from given labels, mint and maxt.
func populateSeries(lbls []map[string]string, mint, maxt int64) []storage.Series {
	if len(lbls) == 0 {
		return nil
	}

	series := make([]storage.Series, 0, len(lbls))
	for _, lbl := range lbls {
		if len(lbl) == 0 {
			continue
		}
		samples := make([]chunks.Sample, 0, maxt-mint+1)
		for t := mint; t <= maxt; t++ {
			samples = append(samples, sample{t: t, f: rand.Float64()})
		}
		series = append(series, storage.NewListSeries(labels.FromMap(lbl), samples))
	}
	return series
}
