cloudsave/pkg/tools/archive/archive.go

package archive

import (
	"archive/tar"
	"compress/gzip"
	"fmt"
	"io"
	"log/slog"
	"os"
	"path/filepath"
)

const (
	// Tune these to your app’s needs
	maxCompressedUpload   = 500 << 20  // 500 MiB compressed
	maxUncompressedOutput = 1000 << 20 // 100 MiB after inflate
)

func Untar(file io.Reader, path string) error {
	gzr, err := gzip.NewReader(file)
	if err != nil {
		return err
	}
	defer gzr.Close()

	tr := tar.NewReader(gzr)

	for {
		header, err := tr.Next()

		switch {

		// if no more files are found return
		case err == io.EOF:
			return nil

		// return any other error
		case err != nil:
			return err

		// if the header is nil, just skip it (not sure how this happens)
		case header == nil:
			continue
		}

		// the target location where the dir/file should be created
		target := filepath.Clean(filepath.Join(path, filepath.Clean(header.Name)))

		// the following switch could also be done using fi.Mode(), not sure if there
		// a benefit of using one vs. the other.
		// fi := header.FileInfo()

		// check the file type
		switch header.Typeflag {

		// if its a dir and it doesn't exist create it
		case tar.TypeDir:
			if _, err := os.Stat(target); err != nil {
				if err := os.MkdirAll(target, 0600); err != nil {
					return err
				}
			}

		// if it's a file create it
		case tar.TypeReg:
			f, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR, header.FileInfo().Mode())
			if err != nil {
				return err
			}

			limited := &io.LimitedReader{R: gzr, N: maxUncompressedOutput}

			// copy over contents
			if _, err := io.Copy(f, limited); err != nil {
				return err
			}

			// manually close here after each file operation; defering would cause each file close
			// to wait until all operations have completed.
			if err := f.Close(); err != nil {
				slog.Error("failed to close file", "err", err)
			}

			if limited.N == 0 {
				// Limit exhausted → likely bomb
				return fmt.Errorf("payload too large after decompression")
			}
		}
	}
}

func Tar(file io.Writer, root string) error {
	gw := gzip.NewWriter(file)
	defer gw.Close()

	tw := tar.NewWriter(gw)
	defer tw.Close()

	// Walk again to add files
	err := filepath.Walk(root, func(path string, info os.FileInfo, walkErr error) error {
		if walkErr != nil {
			return fmt.Errorf("failed to walk through the directory: %w", walkErr)
		}

		relpath, err := filepath.Rel(root, path)
		if err != nil {
			return fmt.Errorf("failed to make relative path: %w", err)
		}

		// Create tar header
		header, err := tar.FileInfoHeader(info, path)
		if err != nil {
			return fmt.Errorf("failed to make file info header: %w", err)
		}
		header.Name = relpath

		if err := tw.WriteHeader(header); err != nil {
			return fmt.Errorf("failed to write header: %w", err)
		}

		if !info.Mode().IsRegular() {
			return nil
		}

		file, err := os.Open(filepath.Clean(path))
		if err != nil {
			return fmt.Errorf("failed to open file: %w", err)
		}
		defer file.Close()
		if _, err := io.Copy(tw, file); err != nil {
			return fmt.Errorf("failed to copy file: %w", err)
		}
		return nil
	})
	if err != nil {
		return fmt.Errorf("writing tar entries: %w", err)
	}

	return nil
}