settings: diff-only configs, machine-state split, backup CLI

- settings.json/session.json now store only values that differ from spec defaults - Machine-specific state moves out of settings.json into session.json - Add dms backup create/restore: tar.gz of ~/.config/DankMaterialShell fixes #3027
2026-08-13 00:48:29 -04:00 · 2026-08-11 15:32:01 -04:00
parent 373a3d3136
commit 7974887295
22 changed files with 748 additions and 252 deletions
@@ -0,0 +1,198 @@
+package backup
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+const dirName = "DankMaterialShell"
+
+func ConfigDir() (string, error) {
+	configDir, err := os.UserConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(configDir, dirName), nil
+}
+
+func DefaultArchiveName() string {
+	return fmt.Sprintf("dms-backup-%s.tar.gz", time.Now().Format("20060102-150405"))
+}
+
+func Create(outputPath string) error {
+	srcDir, err := ConfigDir()
+	if err != nil {
+		return err
+	}
+	if _, err := os.Stat(srcDir); err != nil {
+		return fmt.Errorf("no DMS configuration found at %s: %w", srcDir, err)
+	}
+
+	out, err := os.Create(outputPath)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	gz := gzip.NewWriter(out)
+	defer gz.Close()
+	tw := tar.NewWriter(gz)
+	defer tw.Close()
+
+	return filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		rel, err := filepath.Rel(srcDir, path)
+		if err != nil {
+			return err
+		}
+		if rel == "." {
+			return nil
+		}
+
+		var link string
+		if info.Mode()&os.ModeSymlink != 0 {
+			if link, err = os.Readlink(path); err != nil {
+				return err
+			}
+		}
+
+		header, err := tar.FileInfoHeader(info, link)
+		if err != nil {
+			return err
+		}
+		header.Name = filepath.ToSlash(filepath.Join(dirName, rel))
+
+		if err := tw.WriteHeader(header); err != nil {
+			return err
+		}
+		if !info.Mode().IsRegular() {
+			return nil
+		}
+
+		f, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		_, err = io.Copy(tw, f)
+		return err
+	})
+}
+
+func Restore(archivePath string) (string, error) {
+	dstDir, err := ConfigDir()
+	if err != nil {
+		return "", err
+	}
+
+	if err := validateArchive(archivePath); err != nil {
+		return "", err
+	}
+
+	previous := ""
+	if _, err := os.Stat(dstDir); err == nil {
+		previous = dstDir + ".pre-restore-" + time.Now().Format("20060102-150405")
+		if err := os.Rename(dstDir, previous); err != nil {
+			return "", fmt.Errorf("failed to move existing configuration aside: %w", err)
+		}
+	}
+
+	if err := extract(archivePath, filepath.Dir(dstDir)); err != nil {
+		if previous != "" {
+			os.RemoveAll(dstDir)
+			os.Rename(previous, dstDir)
+		}
+		return "", err
+	}
+	return previous, nil
+}
+
+func validateArchive(archivePath string) error {
+	hasSettings := false
+	err := walkArchive(archivePath, func(header *tar.Header, _ *tar.Reader) error {
+		name := filepath.ToSlash(filepath.Clean(header.Name))
+		if strings.HasPrefix(name, "..") || filepath.IsAbs(header.Name) {
+			return fmt.Errorf("unsafe path in archive: %s", header.Name)
+		}
+		if !strings.HasPrefix(name, dirName+"/") && name != dirName {
+			return fmt.Errorf("not a DMS backup: unexpected entry %s", header.Name)
+		}
+		if name == dirName+"/settings.json" {
+			hasSettings = true
+		}
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	if !hasSettings {
+		return fmt.Errorf("not a DMS backup: settings.json missing from archive")
+	}
+	return nil
+}
+
+func extract(archivePath, destParent string) error {
+	return walkArchive(archivePath, func(header *tar.Header, tr *tar.Reader) error {
+		target := filepath.Join(destParent, filepath.Clean(header.Name))
+
+		switch header.Typeflag {
+		case tar.TypeDir:
+			return os.MkdirAll(target, os.FileMode(header.Mode))
+		case tar.TypeSymlink:
+			if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
+				return err
+			}
+			return os.Symlink(header.Linkname, target)
+		case tar.TypeReg:
+			if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
+				return err
+			}
+			f, err := os.OpenFile(target, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, os.FileMode(header.Mode))
+			if err != nil {
+				return err
+			}
+			defer f.Close()
+			_, err = io.Copy(f, tr)
+			return err
+		default:
+			return nil
+		}
+	})
+}
+
+func walkArchive(archivePath string, visit func(*tar.Header, *tar.Reader) error) error {
+	f, err := os.Open(archivePath)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	gz, err := gzip.NewReader(f)
+	if err != nil {
+		return fmt.Errorf("not a gzip archive: %w", err)
+	}
+	defer gz.Close()
+
+	tr := tar.NewReader(gz)
+	for {
+		header, err := tr.Next()
+		if err == io.EOF {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		if err := visit(header, tr); err != nil {
+			return err
+		}
+	}
+}