package index

import (
	
	
	
	
	
	
	
	

	
	
	

	
	
)

const (
	IndexFileExtension     = ".idx"
	ParquetCompactionTXKey = "compaction_tx"
	dirPerms               = os.FileMode(0o755)
	filePerms              = os.FileMode(0o640)
)

type Compaction func(w io.Writer, compact []parts.Part, options ...parquet.WriterOption) (int64, error)

type FileCompaction struct {
	// settings
	dir     string
	compact Compaction
	maxSize int64

	// internal data
	indexFiles []*os.File
	offset     int64          // Writing offsets into the file
	parts      sync.WaitGroup // Wait group for parts that are currently reference in this level.

	// Options
	logger log.Logger
}

func ( string,  int64,  Compaction,  log.Logger) (*FileCompaction, error) {
	 := &FileCompaction{
		dir:     ,
		compact: ,
		maxSize: ,
		logger:  ,
	}

	if  := os.MkdirAll(, dirPerms);  != nil {
		return nil, 
	}

	return , nil
}

func ( *FileCompaction) () int64 { return .maxSize }

// Snapshot takes a snapshot of the current level. It ignores the parts and just hard links the files into the snapshot directory.
// It will rotate the active file if it has data in it rendering all snapshotted files as immutable.
func ( *FileCompaction) ( []parts.Part,  func(parts.Part) error,  string) error {
	if  := os.MkdirAll(, dirPerms);  != nil {
		return 
	}

	for ,  := range .indexFiles {
		if  == len(.indexFiles)-1 {
			// Sync the last file if it has data in it.
			if .offset > 0 {
				if  := .Sync();  != nil {
					return 
				}
			} else {
				return nil // Skip empty file.
			}
		}

		// Hard link the file into the snapshot directory.
		if  := os.Link(.Name(), filepath.Join(, filepath.Base(.Name())));  != nil {
			return 
		}
	}

	// Rotate the active file if it has data in it.
	,  := .createIndexFile(len(.indexFiles))
	return 
}

func ( *FileCompaction) ( int) (*os.File, error) {
	,  := os.OpenFile(filepath.Join(.dir, fmt.Sprintf("%020d%s", , IndexFileExtension)), os.O_CREATE|os.O_RDWR, filePerms)
	if  != nil {
		return nil, 
	}

	.offset = 0
	.indexFiles = append(.indexFiles, )
	return , nil
}

func ( *FileCompaction) ( string) (*os.File, error) {
	,  := os.Open()
	if  != nil {
		return nil, 
	}

	.indexFiles = append(.indexFiles, )
	return , nil
}

// file returns the currently active index file.
func ( *FileCompaction) () *os.File {
	return .indexFiles[len(.indexFiles)-1]
}

// accountingWriter is a writer that accounts for the number of bytes written.
type accountingWriter struct {
	w io.Writer
	n int64
}

func ( *accountingWriter) ( []byte) (int, error) {
	,  := .w.Write()
	.n += int64()
	return , 
}

// Compact will compact the given parts into a Parquet file written to the next level file.
func ( *FileCompaction) ( []parts.Part,  ...parts.Option) ([]parts.Part, int64, int64, error) {
	if len() == 0 {
		return nil, 0, 0, fmt.Errorf("no parts to compact")
	}

	 := &accountingWriter{w: .file()}
	,  := .compact(, ,
		parquet.KeyValueMetadata(
			ParquetCompactionTXKey, // Compacting up through this transaction.
			fmt.Sprintf("%v", [0].TX()),
		),
	) // compact into the next level
	if  != nil {
		return nil, 0, 0, 
	}

	// Record the writing offset into the file.
	 := .offset

	// Record the file size for recovery.
	 := make([]byte, 8)
	binary.LittleEndian.PutUint64(, uint64(.n))
	if ,  := .file().Write();  != 8 {
		return nil, 0, 0, fmt.Errorf("failed to write size to file: %v", )
	}
	.offset += .n + 8

	// Sync file after writing.
	if  := .Sync();  != nil {
		return nil, 0, 0, fmt.Errorf("failed to sync file: %v", )
	}

	,  := parquet.OpenFile(io.NewSectionReader(.file(), , .n), .n)
	if  != nil {
		return nil, 0, 0, fmt.Errorf("failed to open file after compaction: %w", )
	}

	,  := dynparquet.NewSerializedBuffer()
	if  != nil {
		return nil, 0, 0, 
	}

	.parts.Add(1)
	return []parts.Part{parts.NewParquetPart([0].TX(), , append(, parts.WithRelease(.parts.Done))...)}, , .n, nil
}

// Reset is called when the level no longer has active parts in it at the end of a compaction.
func ( *FileCompaction) () {
	.parts.Wait() // Wait for all parts to be released.
	for ,  := range .indexFiles {
		if  := .Close();  != nil {
			level.Error(.logger).Log("msg", "failed to close level file", "err", )
		}
	}

	// Delete all the files in the directory level. And open a new file.
	if  := os.RemoveAll(.dir);  != nil {
		level.Error(.logger).Log("msg", "failed to remove level directory", "err", )
	}

	if  := os.MkdirAll(.dir, dirPerms);  != nil {
		level.Error(.logger).Log("msg", "failed to create level directory", "err", )
	}

	.indexFiles = nil
	,  := .createIndexFile(len(.indexFiles))
	if  != nil {
		level.Error(.logger).Log("msg", "failed to create new level file", "err", )
	}
}

// recovery the level from the given directory.
func ( *FileCompaction) ( ...parts.Option) ([]parts.Part, error) {
	defer func() {
		,  := .createIndexFile(len(.indexFiles))
		if  != nil {
			level.Error(.logger).Log("msg", "failed to create new level file", "err", )
		}
	}()
	 := []parts.Part{}
	 := filepath.WalkDir(.dir, func( string,  os.DirEntry,  error) error {
		if  != nil {
			return 
		}

		if filepath.Ext() != IndexFileExtension {
			return nil
		}

		,  := .Info()
		if  != nil {
			return fmt.Errorf("failed to get file info: %v", )
		}

		if .Size() == 0 { // file empty, nothing to recover.
			return nil
		}

		,  := .openIndexFile()
		if  != nil {
			return fmt.Errorf("failed to open file: %v", )
		}

		// Recover all parts from file.
		 := []parts.Part{}
		if  := func() error {
			for  := .Size();  > 0; {
				 -= 8
				 := make([]byte, 8)
				if ,  := .ReadAt(, );  != 8 {
					return fmt.Errorf("failed to read size from file: %v", )
				}
				 := int64(binary.LittleEndian.Uint64())
				 -= 

				,  := parquet.OpenFile(io.NewSectionReader(, , ), )
				if  != nil {
					return 
				}

				,  := dynparquet.NewSerializedBuffer()
				if  != nil {
					return 
				}

				var  int
				,  := .ParquetFile().Lookup(ParquetCompactionTXKey)
				if ! {
					level.Warn(.logger).Log("msg", "failed to find compaction_tx metadata", "file", .Name())
					 = 0 // Downgrade the compaction tx so that all future reads will be able to read this part.
				} else {
					,  = strconv.Atoi()
					if  != nil {
						level.Warn(.logger).Log("msg", "failed to parse compaction_tx metadata", "file", .Name(), "err", )
						 = 0 // Downgrade the compaction tx so that all future reads will be able to read this part.
					}
				}

				.parts.Add(1)
				 = append(, parts.NewParquetPart(uint64(), , append(, parts.WithRelease(.parts.Done))...))
			}

			return nil
		}();  != nil {
			for ,  := range  {
				.Release()
			}

			// If we failed to recover the file, remove it.
			if  := .file().Close();  != nil {
				level.Error(.logger).Log("msg", "failed to close level file after failed recovery", "err", )
			}
			.indexFiles = .indexFiles[:len(.indexFiles)-1] // Remove the file from the list of files.
			return 
		}

		 = append(, ...)
		return nil
	})
	if  != nil {
		return nil, 
	}

	return , nil
}

// Sync calls Sync on the underlying file.
func ( *FileCompaction) () error { return .file().Sync() }

type inMemoryLevel struct {
	compact Compaction
	maxSize int64
}

func ( *inMemoryLevel) () int64 { return .maxSize }
func ( *inMemoryLevel) ( []parts.Part,  func(parts.Part) error,  string) error {
	for ,  := range  {
		if  := ();  != nil {
			return 
		}
	}
	return nil
}
func ( *inMemoryLevel) () {}
func ( *inMemoryLevel) ( []parts.Part,  ...parts.Option) ([]parts.Part, int64, int64, error) {
	if len() == 0 {
		return nil, 0, 0, fmt.Errorf("no parts to compact")
	}

	var  bytes.Buffer
	,  := .compact(&, )
	if  != nil {
		return nil, 0, 0, 
	}

	,  := dynparquet.ReaderFromBytes(.Bytes())
	if  != nil {
		return nil, 0, 0, 
	}

	 := int64(.Len())
	return []parts.Part{parts.NewParquetPart([0].TX(), , ...)}, , , nil
}