♻️ Refactor synchronization service

internal/syncer/backend/snapshotstore/blob/localfs/store.go

@@ -0,0 +1,182 @@
+package localfs
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"voidraft/internal/syncer/backend/snapshotstore/blob"
+)
+
+// Store 提供基于本地目录的 blob 存储实现。
+type Store struct {
+	rootPath string
+}
+
+// New 创建新的 localfs blob 存储。
+func New(rootPath string) (*Store, error) {
+	if strings.TrimSpace(rootPath) == "" {
+		return nil, errors.New("localfs root path is required")
+	}
+	if err := os.MkdirAll(rootPath, 0755); err != nil {
+		return nil, fmt.Errorf("create localfs root path: %w", err)
+	}
+	return &Store{rootPath: rootPath}, nil
+}
+
+// Get 读取对象内容。
+func (s *Store) Get(ctx context.Context, key string) (io.ReadCloser, blob.ObjectInfo, error) {
+	_ = ctx
+
+	info, err := s.Stat(ctx, key)
+	if err != nil {
+		return nil, blob.ObjectInfo{}, err
+	}
+
+	path, err := s.resolvePath(key)
+	if err != nil {
+		return nil, blob.ObjectInfo{}, err
+	}
+
+	reader, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, blob.ObjectInfo{}, blob.ErrObjectNotFound
+		}
+		return nil, blob.ObjectInfo{}, err
+	}
+
+	return reader, info, nil
+}
+
+// Put 写入对象内容。
+func (s *Store) Put(ctx context.Context, key string, body io.Reader, options blob.PutOptions) (blob.ObjectInfo, error) {
+	_ = ctx
+
+	path, err := s.resolvePath(key)
+	if err != nil {
+		return blob.ObjectInfo{}, err
+	}
+
+	if options.IfMatch != "" {
+		currentInfo, err := s.Stat(ctx, key)
+		if err != nil {
+			if errors.Is(err, blob.ErrObjectNotFound) {
+				return blob.ObjectInfo{}, blob.ErrConditionNotMet
+			}
+			return blob.ObjectInfo{}, err
+		}
+		if currentInfo.Revision != options.IfMatch {
+			return blob.ObjectInfo{}, blob.ErrConditionNotMet
+		}
+	}
+
+	data, err := io.ReadAll(body)
+	if err != nil {
+		return blob.ObjectInfo{}, err
+	}
+
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+		return blob.ObjectInfo{}, err
+	}
+
+	tempFile, err := os.CreateTemp(filepath.Dir(path), "blob-put-*")
+	if err != nil {
+		return blob.ObjectInfo{}, err
+	}
+	tempName := tempFile.Name()
+
+	if _, err := tempFile.Write(data); err != nil {
+		tempFile.Close()
+		_ = os.Remove(tempName)
+		return blob.ObjectInfo{}, err
+	}
+	if err := tempFile.Close(); err != nil {
+		_ = os.Remove(tempName)
+		return blob.ObjectInfo{}, err
+	}
+	if err := os.Rename(tempName, path); err != nil {
+		_ = os.Remove(tempName)
+		return blob.ObjectInfo{}, err
+	}
+
+	return blob.ObjectInfo{
+		Key:      key,
+		Revision: digest(data),
+		Size:     int64(len(data)),
+	}, nil
+}
+
+// Stat 返回对象元信息。
+func (s *Store) Stat(ctx context.Context, key string) (blob.ObjectInfo, error) {
+	_ = ctx
+
+	path, err := s.resolvePath(key)
+	if err != nil {
+		return blob.ObjectInfo{}, err
+	}
+
+	file, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return blob.ObjectInfo{}, blob.ErrObjectNotFound
+		}
+		return blob.ObjectInfo{}, err
+	}
+	defer file.Close()
+
+	hash := sha256.New()
+	size, err := io.Copy(hash, file)
+	if err != nil {
+		return blob.ObjectInfo{}, err
+	}
+
+	return blob.ObjectInfo{
+		Key:      key,
+		Revision: hex.EncodeToString(hash.Sum(nil)),
+		Size:     size,
+	}, nil
+}
+
+// Delete 删除指定对象。
+func (s *Store) Delete(ctx context.Context, key string) error {
+	_ = ctx
+
+	path, err := s.resolvePath(key)
+	if err != nil {
+		return err
+	}
+	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
+
+// resolvePath 将对象键转换为安全路径。
+func (s *Store) resolvePath(key string) (string, error) {
+	normalized := filepath.Clean(filepath.FromSlash(key))
+	if normalized == "." || normalized == string(filepath.Separator) {
+		return "", errors.New("invalid blob key")
+	}
+
+	path := filepath.Join(s.rootPath, normalized)
+	rel, err := filepath.Rel(s.rootPath, path)
+	if err != nil {
+		return "", err
+	}
+	if strings.HasPrefix(rel, "..") {
+		return "", errors.New("blob key escapes root path")
+	}
+	return path, nil
+}
+
+// digest 计算内容摘要。
+func digest(data []byte) string {
+	sum := sha256.Sum256(data)
+	return hex.EncodeToString(sum[:])
+}