// Copyright 2020 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 chunks

import (
	"encoding/binary"
	"io/ioutil"
	"math/rand"
	"os"
	"testing"

	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/prometheus/prometheus/util/testutil"
)

func TestHeadReadWriter_WriteChunk_Chunk_IterateChunks(t *testing.T) {
	hrw, close := testHeadReadWriter(t)
	defer func() {
		testutil.Ok(t, hrw.Close())
		close()
	}()

	expectedBytes := []byte{}
	nextChunkOffset := uint64(HeadChunkFileHeaderSize)
	chkCRC32 := newCRC32()

	type expectedDataType struct {
		seriesRef, chunkRef uint64
		mint, maxt          int64
		numSamples          uint16
		chunk               chunkenc.Chunk
	}
	expectedData := []expectedDataType{}

	var buf [MaxHeadChunkMetaSize]byte
	totalChunks := 0
	var firstFileName string
	for hrw.curFileSequence < 3 || hrw.chkWriter.Buffered() == 0 {
		addChunks := func(numChunks int) {
			for i := 0; i < numChunks; i++ {
				seriesRef, chkRef, mint, maxt, chunk := createChunk(t, totalChunks, hrw)
				totalChunks++
				expectedData = append(expectedData, expectedDataType{
					seriesRef:  seriesRef,
					mint:       mint,
					maxt:       maxt,
					chunkRef:   chkRef,
					chunk:      chunk,
					numSamples: uint16(chunk.NumSamples()),
				})

				if hrw.curFileSequence != 1 {
					// We are checking for bytes written only for the first file.
					continue
				}

				// Calculating expected bytes written on disk for first file.
				firstFileName = hrw.curFile.Name()
				testutil.Equals(t, chunkRef(1, nextChunkOffset), chkRef)

				bytesWritten := 0
				chkCRC32.Reset()

				binary.BigEndian.PutUint64(buf[bytesWritten:], seriesRef)
				bytesWritten += SeriesRefSize
				binary.BigEndian.PutUint64(buf[bytesWritten:], uint64(mint))
				bytesWritten += MintMaxtSize
				binary.BigEndian.PutUint64(buf[bytesWritten:], uint64(maxt))
				bytesWritten += MintMaxtSize
				buf[bytesWritten] = byte(chunk.Encoding())
				bytesWritten += ChunkEncodingSize
				n := binary.PutUvarint(buf[bytesWritten:], uint64(len(chunk.Bytes())))
				bytesWritten += n

				expectedBytes = append(expectedBytes, buf[:bytesWritten]...)
				_, err := chkCRC32.Write(buf[:bytesWritten])
				testutil.Ok(t, err)
				expectedBytes = append(expectedBytes, chunk.Bytes()...)
				_, err = chkCRC32.Write(chunk.Bytes())
				testutil.Ok(t, err)

				expectedBytes = append(expectedBytes, chkCRC32.Sum(nil)...)

				// += seriesRef, mint, maxt, encoding, chunk data len, chunk data, CRC.
				nextChunkOffset += SeriesRefSize + 2*MintMaxtSize + ChunkEncodingSize + uint64(n) + uint64(len(chunk.Bytes())) + CRCSize
			}
		}
		addChunks(100)
		hrw.CutNewFile()
		addChunks(10) // For chunks in in-memory buffer.
	}

	// Checking on-disk bytes for the first file.
	testutil.Assert(t, len(hrw.mmappedChunkFiles) == 3 && len(hrw.closers) == 3, "expected 3 mmapped files, got %d", len(hrw.mmappedChunkFiles))

	actualBytes, err := ioutil.ReadFile(firstFileName)
	testutil.Ok(t, err)

	// Check header of the segment file.
	testutil.Equals(t, MagicHeadChunks, int(binary.BigEndian.Uint32(actualBytes[0:MagicChunksSize])))
	testutil.Equals(t, chunksFormatV1, int(actualBytes[MagicChunksSize]))

	// Remaining chunk data.
	fileEnd := HeadChunkFileHeaderSize + len(expectedBytes)
	testutil.Equals(t, expectedBytes, actualBytes[HeadChunkFileHeaderSize:fileEnd])

	// Test for the next chunk header to be all 0s. That marks the end of the file.
	for _, b := range actualBytes[fileEnd : fileEnd+MaxHeadChunkMetaSize] {
		testutil.Equals(t, byte(0), b)
	}

	// Testing reading of chunks.
	for _, exp := range expectedData {
		actChunk, err := hrw.Chunk(exp.chunkRef)
		testutil.Ok(t, err)
		testutil.Equals(t, exp.chunk.Bytes(), actChunk.Bytes())
	}

	// Testing IterateAllChunks method.
	dir := hrw.dir.Name()
	testutil.Ok(t, hrw.Close())
	hrw, err = NewChunkDiskMapper(dir, chunkenc.NewPool())
	testutil.Ok(t, err)

	idx := 0
	err = hrw.IterateAllChunks(func(seriesRef, chunkRef uint64, mint, maxt int64, numSamples uint16) error {
		t.Helper()

		expData := expectedData[idx]
		testutil.Equals(t, expData.seriesRef, seriesRef)
		testutil.Equals(t, expData.chunkRef, chunkRef)
		testutil.Equals(t, expData.maxt, maxt)
		testutil.Equals(t, expData.maxt, maxt)
		testutil.Equals(t, expData.numSamples, numSamples)

		actChunk, err := hrw.Chunk(expData.chunkRef)
		testutil.Ok(t, err)
		testutil.Equals(t, expData.chunk.Bytes(), actChunk.Bytes())

		idx++
		return nil
	})
	testutil.Ok(t, err)
	testutil.Equals(t, len(expectedData), idx)

}

// TestHeadReadWriter_Truncate tests
// * If truncation is happening properly based on the time passed.
// * The active file is not deleted even if the passed time makes it eligible to be deleted.
// * Empty current file does not lead to creation of another file after truncation.
// * Non-empty current file leads to creation of another file after truncation.
func TestHeadReadWriter_Truncate(t *testing.T) {
	hrw, close := testHeadReadWriter(t)
	defer func() {
		testutil.Ok(t, hrw.Close())
		close()
	}()

	timeRange := 0
	fileTimeStep := 100
	totalFiles := 7
	startIndexAfter1stTruncation, startIndexAfter2ndTruncation := 3, 6
	filesDeletedAfter1stTruncation, filesDeletedAfter2ndTruncation := 2, 5
	var timeToTruncate, timeToTruncateAfterRestart int64

	addChunk := func() int {
		mint := timeRange + 1                // Just after the the new file cut.
		maxt := timeRange + fileTimeStep - 1 // Just before the next file.

		// Write a chunks to set maxt for the segment.
		_, err := hrw.WriteChunk(1, int64(mint), int64(maxt), randomChunk(t))
		testutil.Ok(t, err)

		timeRange += fileTimeStep

		return mint
	}

	cutFile := func(i int) {
		testutil.Ok(t, hrw.CutNewFile())

		mint := addChunk()

		if i == startIndexAfter1stTruncation {
			timeToTruncate = int64(mint)
		} else if i == startIndexAfter2ndTruncation {
			timeToTruncateAfterRestart = int64(mint)
		}
	}

	// Cut segments.
	for i := 1; i <= totalFiles; i++ {
		cutFile(i)
	}

	// Verifying the files.
	verifyFiles := func(remainingFiles, startIndex int) {
		t.Helper()

		files, err := ioutil.ReadDir(hrw.dir.Name())
		testutil.Ok(t, err)
		testutil.Equals(t, remainingFiles, len(files), "files on disk")
		testutil.Equals(t, remainingFiles, len(hrw.mmappedChunkFiles), "hrw.mmappedChunkFiles")
		testutil.Equals(t, remainingFiles, len(hrw.closers), "closers")

		for i := 1; i <= totalFiles; i++ {
			_, ok := hrw.mmappedChunkFiles[i]
			if i < startIndex {
				testutil.Equals(t, false, ok)
			} else {
				testutil.Equals(t, true, ok)
			}
		}
	}

	// Verify the number of segments.
	verifyFiles(totalFiles, 1)

	// Truncating files.
	testutil.Ok(t, hrw.Truncate(timeToTruncate))
	totalFiles++ // Truncation creates a new file as the last file is not empty.
	verifyFiles(totalFiles-filesDeletedAfter1stTruncation, startIndexAfter1stTruncation)
	addChunk() // Add a chunk so that new file is not truncated.

	dir := hrw.dir.Name()
	testutil.Ok(t, hrw.Close())

	// Restarted.
	var err error
	hrw, err = NewChunkDiskMapper(dir, chunkenc.NewPool())
	testutil.Ok(t, err)

	testutil.Assert(t, !hrw.fileMaxtSet, "")
	testutil.Ok(t, hrw.IterateAllChunks(func(_, _ uint64, _, _ int64, _ uint16) error { return nil }))
	testutil.Assert(t, hrw.fileMaxtSet, "")

	// Truncating files after restart. As the last file was empty, this creates no new files.
	testutil.Ok(t, hrw.Truncate(timeToTruncateAfterRestart))
	verifyFiles(totalFiles-filesDeletedAfter2ndTruncation, startIndexAfter2ndTruncation)

	// First chunk after restart creates a new file.
	addChunk()
	totalFiles++

	// Truncating till current time should not delete the current active file.
	testutil.Ok(t, hrw.Truncate(int64(timeRange+fileTimeStep)))
	verifyFiles(2, totalFiles) // One file is the active file and one was newly created.
}

// TestHeadReadWriter_Truncate_NoUnsequentialFiles tests
// that truncation leaves no unsequential files on disk, mainly under the following case
// * There is an empty file in between the sequence while the truncation
//   deletes files only upto a sequence before that (i.e. stops deleting
//   after it has found a file that is not deletable).
// This tests https://github.com/prometheus/prometheus/issues/7412 where
// the truncation used to check all the files for deletion and end up
// deleting empty files in between and breaking the sequence.
func TestHeadReadWriter_Truncate_NoUnsequentialFiles(t *testing.T) {
	hrw, close := testHeadReadWriter(t)
	defer func() {
		testutil.Ok(t, hrw.Close())
		close()
	}()

	timeRange := 0
	addChunk := func() {
		step := 100
		mint, maxt := timeRange+1, timeRange+step-1
		_, err := hrw.WriteChunk(1, int64(mint), int64(maxt), randomChunk(t))
		testutil.Ok(t, err)
		timeRange += step
	}
	emptyFile := func() {
		testutil.Ok(t, hrw.CutNewFile())
	}
	nonEmptyFile := func() {
		emptyFile()
		addChunk()
	}

	addChunk()     // 1. Created with the first chunk.
	nonEmptyFile() // 2.
	nonEmptyFile() // 3.
	emptyFile()    // 4.
	nonEmptyFile() // 5.
	emptyFile()    // 6.

	// Verifying the files.
	verifyFiles := func(remainingFiles []int) {
		t.Helper()

		files, err := ioutil.ReadDir(hrw.dir.Name())
		testutil.Ok(t, err)
		testutil.Equals(t, len(remainingFiles), len(files), "files on disk")
		testutil.Equals(t, len(remainingFiles), len(hrw.mmappedChunkFiles), "hrw.mmappedChunkFiles")
		testutil.Equals(t, len(remainingFiles), len(hrw.closers), "closers")

		for _, i := range remainingFiles {
			_, ok := hrw.mmappedChunkFiles[i]
			testutil.Equals(t, true, ok)
		}
	}

	verifyFiles([]int{1, 2, 3, 4, 5, 6})

	// Truncating files till 2. It should not delete anything after 3 (inclusive)
	// though files 4 and 6 are empty.
	file2Maxt := hrw.mmappedChunkFiles[2].maxt
	testutil.Ok(t, hrw.Truncate(file2Maxt+1))
	// As 6 was empty, it should not create another file.
	verifyFiles([]int{3, 4, 5, 6})

	addChunk()
	// Truncate creates another file as 6 is not empty now.
	testutil.Ok(t, hrw.Truncate(file2Maxt+1))
	verifyFiles([]int{3, 4, 5, 6, 7})

	dir := hrw.dir.Name()
	testutil.Ok(t, hrw.Close())

	// Restarting checks for unsequential files.
	var err error
	hrw, err = NewChunkDiskMapper(dir, chunkenc.NewPool())
	testutil.Ok(t, err)
	verifyFiles([]int{3, 4, 5, 6, 7})
}

func testHeadReadWriter(t *testing.T) (hrw *ChunkDiskMapper, close func()) {
	tmpdir, err := ioutil.TempDir("", "data")
	testutil.Ok(t, err)
	hrw, err = NewChunkDiskMapper(tmpdir, chunkenc.NewPool())
	testutil.Ok(t, err)
	testutil.Assert(t, !hrw.fileMaxtSet, "")
	testutil.Ok(t, hrw.IterateAllChunks(func(_, _ uint64, _, _ int64, _ uint16) error { return nil }))
	testutil.Assert(t, hrw.fileMaxtSet, "")
	return hrw, func() {
		testutil.Ok(t, os.RemoveAll(tmpdir))
	}
}

func randomChunk(t *testing.T) chunkenc.Chunk {
	chunk := chunkenc.NewXORChunk()
	len := rand.Int() % 120
	app, err := chunk.Appender()
	testutil.Ok(t, err)
	for i := 0; i < len; i++ {
		app.Append(rand.Int63(), rand.Float64())
	}
	return chunk
}

func createChunk(t *testing.T, idx int, hrw *ChunkDiskMapper) (seriesRef uint64, chunkRef uint64, mint, maxt int64, chunk chunkenc.Chunk) {
	var err error
	seriesRef = uint64(rand.Int63())
	mint = int64((idx)*1000 + 1)
	maxt = int64((idx + 1) * 1000)
	chunk = randomChunk(t)
	chunkRef, err = hrw.WriteChunk(seriesRef, mint, maxt, chunk)
	testutil.Ok(t, err)
	return
}