scotty/internal/archive/archive.go

/*
Copyright © 2025 Philipp Wolfer <phw@uploadedlobster.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

// Implements generic access to files inside an archive.
//
// An archive in this context can be any container that holds files.
// In this implementation the archive can be a ZIP file or a directory.
package archive

import (
	"archive/zip"
	"fmt"
	"io"
	"io/fs"
	"os"
	"path/filepath"
)

// Generic interface to access files inside an archive.
type ArchiveReader interface {
	io.Closer

	// Open the file inside the archive identified by the given path.
	// The path is relative to the archive's root.
	// The caller must call [fs.File.Close] when finished using the file.
	Open(path string) (fs.File, error)

	// List files inside the archive which satisfy the given glob pattern.
	// This method only returns files, not directories.
	Glob(pattern string) ([]FileInfo, error)
}

// Open an archive in path.
// The archive can be a ZIP file or a directory. The implementation
// will detect the type of archive and return the appropriate
// implementation of the Archive interface.
func OpenArchive(path string) (ArchiveReader, error) {
	fi, err := os.Stat(path)
	if err != nil {
		return nil, err
	}
	switch mode := fi.Mode(); {
	case mode.IsRegular():
		archive := &zipArchive{}
		err := archive.OpenArchive(path)
		if err != nil {
			return nil, err
		}
		return archive, nil
	case mode.IsDir():
		archive := &dirArchive{}
		err := archive.OpenArchive(path)
		if err != nil {
			return nil, err
		}
		return archive, nil
	default:
		return nil, fmt.Errorf("unsupported file mode: %s", mode)
	}
}

// Interface for a file that can be opened when needed.
type OpenableFile interface {
	// Open the file for reading.
	// The caller is responsible to call [io.ReadCloser.Close] when
	// finished reading the file.
	Open() (io.ReadCloser, error)
}

// Generic information about a file inside an archive.
// This provides the filename and allows opening the file for reading.
type FileInfo struct {
	Name string
	File OpenableFile
}

// A openable file in the filesystem.
type filesystemFile struct {
	path string
}

func (f *filesystemFile) Open() (io.ReadCloser, error) {
	return os.Open(f.path)
}

// An implementation of the archiveBackend interface for zip files.
type zipArchive struct {
	zip *zip.ReadCloser
}

func (a *zipArchive) OpenArchive(path string) error {
	zip, err := zip.OpenReader(path)
	if err != nil {
		return err
	}
	a.zip = zip
	return nil
}

func (a *zipArchive) Close() error {
	if a.zip == nil {
		return nil
	}
	return a.zip.Close()
}

func (a *zipArchive) Glob(pattern string) ([]FileInfo, error) {
	result := make([]FileInfo, 0)
	for _, file := range a.zip.File {
		if file.FileInfo().IsDir() {
			continue
		}

		if matched, err := filepath.Match(pattern, file.Name); matched {
			if err != nil {
				return nil, err
			}
			info := FileInfo{
				Name: file.Name,
				File: file,
			}
			result = append(result, info)
		}
	}

	return result, nil
}

func (a *zipArchive) Open(path string) (fs.File, error) {
	file, err := a.zip.Open(path)
	if err != nil {
		return nil, err
	}
	return file, nil
}

// An implementation of the archiveBackend interface for directories.
type dirArchive struct {
	path  string
	dirFS fs.FS
}

func (a *dirArchive) OpenArchive(path string) error {
	a.path = filepath.Clean(path)
	a.dirFS = os.DirFS(path)
	return nil
}

func (a *dirArchive) Close() error {
	return nil
}

// Open opens the named file in the archive.
// [fs.File.Close] must be called to release any associated resources.
func (a *dirArchive) Open(path string) (fs.File, error) {
	return a.dirFS.Open(path)
}

func (a *dirArchive) Glob(pattern string) ([]FileInfo, error) {
	files, err := fs.Glob(a.dirFS, pattern)
	if err != nil {
		return nil, err
	}
	result := make([]FileInfo, 0)
	for _, name := range files {
		stat, err := fs.Stat(a.dirFS, name)
		if err != nil {
			return nil, err
		}
		if stat.IsDir() {
			continue
		}

		fullPath := filepath.Join(a.path, name)
		info := FileInfo{
			Name: name,
			File: &filesystemFile{path: fullPath},
		}
		result = append(result, info)
	}

	return result, nil
}