buildr/internal/archive/tree.go

package archive

import (
	"archive/tar"
	"errors"
	"fmt"
	"io/fs"
	"path"
	"path/filepath"
	"strings"
	"time"

	"code.icb4dc0.de/buildr/buildr/internal/ioutils"
)

var defaultCreationTime = time.Unix(0, 0)

type fileToTar struct {
	sourcePath     string
	targetFileName string
}

type filesToTar []fileToTar

func (files *filesToTar) IsEmpty() bool {
	return len(*files) == 0
}

func (files *filesToTar) Add(toAdd fileToTar) {
	ref := *files
	ref = append(ref, toAdd)
	*files = ref
}

func (files *filesToTar) Remove(toRemove string) bool {
	ref := *files

	for i := range ref {
		if ref[i].targetFileName == toRemove {
			ref = append(ref[:i], ref[i+1:]...)
			*files = ref
			return true
		}
	}

	return false
}

func newNode() *archiveNode {
	return &archiveNode{
		children: make(map[string]*archiveNode),
		files:    new(filesToTar),
	}
}

type archiveNode struct {
	children map[string]*archiveNode
	files    *filesToTar
}

func (n *archiveNode) writeToTar(writer *tar.Writer, fileSystem fs.StatFS, parent string) error {
	for segment, child := range n.children {
		if child.isEmpty() {
			continue
		}
		segmentPath := filepath.Join(parent, segment)
		header := &tar.Header{
			Name:     segmentPath,
			Typeflag: tar.TypeDir,
			// Use a fixed Mode, so that this isn't sensitive to the directory and umask
			// under which it was created. Additionally, windows can only set 0222,
			// 0444, or 0666, none of which are executable.
			Mode:    0o555,
			ModTime: defaultCreationTime,
		}

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

		if err := child.writeToTar(writer, fileSystem, segmentPath); err != nil {
			return err
		}
	}

	for _, fileSpec := range *n.files {
		info, err := fileSystem.Stat(fileSpec.sourcePath)
		if err != nil {
			return err
		}

		f, err := fileSystem.Open(fileSpec.sourcePath)
		if err != nil {
			return err
		}

		header, err := tar.FileInfoHeader(info, path.Join(parent, fileSpec.targetFileName))
		if err != nil {
			return err
		}

		header.Name = path.Join(parent, fileSpec.targetFileName)

		if err = writer.WriteHeader(header); err != nil {
			return errors.Join(err, f.Close())
		}

		if _, err = ioutils.CopyWithPooledBuffer(writer, f); err != nil {
			return errors.Join(err, f.Close())
		}

		if err := f.Close(); err != nil {
			return err
		}
	}

	return nil
}

func (n *archiveNode) remove(pathToRemove string) bool {
	if pathToRemove == "" {
		return false
	}

	split := strings.Split(pathToRemove, "/")

	last := split[len(split)-1]

	current := n
	for _, segment := range split[:len(split)-1] {
		if child, ok := current.children[segment]; ok {
			current = child
			continue
		} else {
			return false
		}
	}

	if _, ok := current.children[last]; ok {
		delete(current.children, last)
		return true
	} else {
		return current.files.Remove(last)
	}
}

func (n *archiveNode) addFile(sourcePath, targetPath string) {
	dirPath, fileName := filepath.Split(targetPath)
	current := n
	for _, segment := range strings.Split(dirPath, "/") {
		if segment == "" {
			continue
		}
		if child, ok := current.children[segment]; ok {
			current = child
		} else {
			newNode := &archiveNode{
				children: make(map[string]*archiveNode),
				files:    new(filesToTar),
			}
			current.children[segment] = newNode
			current = newNode
		}
	}

	current.files.Add(fileToTar{
		sourcePath:     sourcePath,
		targetFileName: fileName,
	})
}

func (n *archiveNode) addDir(dirPath string) {
	current := n
	for _, segment := range strings.Split(dirPath, "/") {
		if segment == "" {
			continue
		}

		if child, ok := current.children[segment]; ok {
			current = child
		} else {
			newNode := newNode()
			current.children[segment] = newNode
			current = newNode
		}
	}
}

func (n *archiveNode) isEmpty() bool {
	return len(n.children) == 0 && n.files.IsEmpty()
}