Additions to domain/ and workspace/ chron-note packages

chron-note/internal/stores/cas/fs.go

@@ -0,0 +1,93 @@
+package cas
+
+import (
+	"context"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"git.michelsen.id/phill/chron/chron-note/internal/domain"
+	"git.michelsen.id/phill/chron/chron-note/internal/util"
+)
+
+var ErrBlobNotFound = errors.New("blob not found")
+
+type FS struct {
+	root string
+}
+
+func NewFS(root string) *FS {
+	return &FS{root: root}
+}
+
+func (s *FS) Put(ctx context.Context, data []byte) (domain.BlobID, error) {
+	_ = ctx
+
+	sum := util.Hash256(data)
+	var id domain.BlobID
+	copy(id[:], sum[:])
+
+	p := s.pathFor(id)
+
+	// Fast path: already exists
+	if _, err := os.Stat(p); err == nil {
+		return id, nil
+	}
+
+	if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
+		return domain.BlobID{}, err
+	}
+
+	tmp := p + ".tmp"
+	if err := os.WriteFile(tmp, data, 0o644); err != nil {
+		return domain.BlobID{}, err
+	}
+	if err := os.Rename(tmp, p); err != nil {
+		_ = os.Remove(tmp)
+		// If another writer won the race, accept it.
+		if _, statErr := os.Stat(p); statErr == nil {
+			return id, nil
+		}
+		return domain.BlobID{}, err
+	}
+
+	return id, nil
+}
+
+func (s *FS) Get(ctx context.Context, id domain.BlobID) ([]byte, error) {
+	_ = ctx
+	p := s.pathFor(id)
+	b, err := os.ReadFile(p)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, ErrBlobNotFound
+		}
+		return nil, err
+	}
+	return b, nil
+}
+
+func (s *FS) Has(ctx context.Context, id domain.BlobID) (bool, error) {
+	_ = ctx
+	p := s.pathFor(id)
+	_, err := os.Stat(p)
+	if err == nil {
+		return true, nil
+	}
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	return false, err
+}
+
+func (s *FS) pathFor(id domain.BlobID) string {
+	hexID := hex.EncodeToString(id[:])
+	if len(hexID) < 4 {
+		// should never happen
+		return filepath.Join(s.root, fmt.Sprintf("bad-%s", hexID))
+	}
+	// git-style fanout
+	return filepath.Join(s.root, hexID[:2], hexID[2:4], hexID)
+}