feat(cli): add transactional installation backups

2026-08-16 00:55:22 +02:00
parent 3e0c864c85
commit 11fbf0a138
8 changed files with 2088 additions and 0 deletions
@@ -0,0 +1,113 @@
+// Package lifecycle coordinates installation-wide mutating operations.
+package lifecycle
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+
+	"github.com/aritmolab/thothii/tools/tht/internal/config"
+)
+
+var (
+	ErrLocked    = errors.New("another lifecycle operation is already running for this installation")
+	ErrOwnership = errors.New("lifecycle lock ownership changed; refusing to remove it")
+)
+
+const lockFileName = "lifecycle.lock.owner.json"
+
+type owner struct {
+	Token     string    `json:"token"`
+	PID       int       `json:"pid"`
+	CreatedAt time.Time `json:"created_at"`
+}
+
+// Lock is an exclusively-created owner file scoped to one installation descriptor.
+type Lock struct {
+	path     string
+	token    string
+	mu       sync.Mutex
+	released bool
+}
+
+// Acquire obtains the shared lock used by backup, restore, Pi lifecycle and product updates.
+func Acquire(installation config.Installation) (*Lock, error) {
+	directory := installation.ControlDirectory()
+	if err := os.MkdirAll(directory, 0o700); err != nil {
+		return nil, fmt.Errorf("create lifecycle control directory: %w", err)
+	}
+	info, err := os.Lstat(directory)
+	if err != nil || !info.IsDir() || info.Mode()&os.ModeSymlink != 0 {
+		return nil, errors.New("lifecycle control directory is not a regular directory")
+	}
+	if err := os.Chmod(directory, 0o700); err != nil {
+		return nil, fmt.Errorf("protect lifecycle control directory: %w", err)
+	}
+
+	tokenBytes := make([]byte, 16)
+	if _, err := rand.Read(tokenBytes); err != nil {
+		return nil, fmt.Errorf("create lifecycle lock owner: %w", err)
+	}
+	token := hex.EncodeToString(tokenBytes)
+	path := filepath.Join(directory, lockFileName)
+	file, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o600)
+	if errors.Is(err, os.ErrExist) {
+		return nil, ErrLocked
+	}
+	if err != nil {
+		return nil, fmt.Errorf("acquire lifecycle lock: %w", err)
+	}
+	value := owner{Token: token, PID: os.Getpid(), CreatedAt: time.Now().UTC()}
+	encodeErr := json.NewEncoder(file).Encode(value)
+	if encodeErr == nil {
+		encodeErr = file.Sync()
+	}
+	closeErr := file.Close()
+	if encodeErr != nil || closeErr != nil {
+		_ = os.Remove(path)
+		return nil, fmt.Errorf("persist lifecycle lock owner: %w", errors.Join(encodeErr, closeErr))
+	}
+	return &Lock{path: path, token: token}, nil
+}
+
+// Path returns the installation-private owner-file path for diagnostics and tests.
+func (lock *Lock) Path() string {
+	if lock == nil {
+		return ""
+	}
+	return lock.path
+}
+
+// Release removes only the owner file created by this Lock.
+func (lock *Lock) Release() error {
+	if lock == nil {
+		return nil
+	}
+	lock.mu.Lock()
+	defer lock.mu.Unlock()
+	if lock.released {
+		return nil
+	}
+	contents, err := os.ReadFile(lock.path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return ErrOwnership
+		}
+		return fmt.Errorf("read lifecycle lock owner: %w", err)
+	}
+	var current owner
+	if json.Unmarshal(contents, &current) != nil || current.Token == "" || current.Token != lock.token {
+		return ErrOwnership
+	}
+	if err := os.Remove(lock.path); err != nil {
+		return fmt.Errorf("release lifecycle lock: %w", err)
+	}
+	lock.released = true
+	return nil
+}