1 files changed, 203 insertions, 0 deletions
diff --git a/object/store/loose/quarantine.go b/object/store/loose/quarantine.go
new file mode 100644
index 00000000..cd337670
--- /dev/null
+++ b/object/store/loose/quarantine.go
@@ -0,0 +1,203 @@
+package loose
+
+import (
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+
+	"lindenii.org/go/furgit/object/store"
+)
+
+var (
+	_ store.ObjectQuarantiner = (*Loose)(nil)
+	_ store.ObjectQuarantine  = (*objectQuarantine)(nil)
+)
+
+// objectQuarantine is one quarantined loose store
+// rooted privately beneath a destination loose root.
+type objectQuarantine struct {
+	*Loose
+
+	parent   *Loose
+	tempName string
+	tempRoot *os.Root
+}
+
+// BeginObjectQuarantine creates one quarantined loose store rooted privately
+// beneath the destination loose root.
+//
+// Labels: Deps-Borrowed, Life-Parent, Close-No.
+func (loose *Loose) BeginObjectQuarantine(_ store.ObjectQuarantineOptions) (store.ObjectQuarantine, error) {
+	tempName, tempRoot, err := createLooseQuarantineRoot(loose.root)
+	if err != nil {
+		return nil, err
+	}
+
+	quarantineStore, err := New(tempRoot, loose.objectFormat)
+	if err != nil {
+		_ = tempRoot.Close()
+		_ = loose.root.RemoveAll(tempName)
+
+		return nil, err
+	}
+
+	return &objectQuarantine{
+		Loose:    quarantineStore,
+		parent:   loose,
+		tempName: tempName,
+		tempRoot: tempRoot,
+	}, nil
+}
+
+// Discard removes the quarantine and invalidates the receiver.
+func (quarantine *objectQuarantine) Discard() error {
+	closeErr := quarantine.Close()
+	tempRootErr := quarantine.tempRoot.Close()
+	removeErr := quarantine.parent.root.RemoveAll(quarantine.tempName)
+
+	if closeErr != nil {
+		return closeErr
+	}
+
+	if tempRootErr != nil {
+		return fmt.Errorf("object/store/loose: %w", tempRootErr)
+	}
+
+	if removeErr != nil {
+		return fmt.Errorf("object/store/loose: %w", removeErr)
+	}
+
+	return nil
+}
+
+// Promote publishes all quarantined loose objects into the parent loose store
+// and invalidates the receiver.
+func (quarantine *objectQuarantine) Promote() error {
+	closeErr := quarantine.Close()
+	promoteErr := promoteLooseQuarantine(quarantine.parent, quarantine.tempName, quarantine.tempRoot)
+	tempRootErr := quarantine.tempRoot.Close()
+	removeErr := quarantine.parent.root.RemoveAll(quarantine.tempName)
+
+	if closeErr != nil {
+		return closeErr
+	}
+
+	if promoteErr != nil {
+		return promoteErr
+	}
+
+	if tempRootErr != nil {
+		return fmt.Errorf("object/store/loose: %w", tempRootErr)
+	}
+
+	if removeErr != nil {
+		return fmt.Errorf("object/store/loose: %w", removeErr)
+	}
+
+	return nil
+}
+
+func createLooseQuarantineRoot(parent *os.Root) (string, *os.Root, error) {
+	var lastErr error
+
+	for range 32 {
+		name := "tmp_looseq_" + rand.Text()
+
+		err := parent.Mkdir(name, 0o700)
+		if err == nil {
+			root, err := parent.OpenRoot(name)
+			if err == nil {
+				return name, root, nil
+			}
+
+			_ = parent.RemoveAll(name)
+
+			return "", nil, fmt.Errorf("object/store/loose: %w", err)
+		}
+
+		lastErr = err
+
+		if errors.Is(err, fs.ErrExist) {
+			continue
+		}
+
+		return "", nil, fmt.Errorf("object/store/loose: %w", err)
+	}
+
+	return "", nil, fmt.Errorf("object/store/loose: failed to create quarantine directory: %w", lastErr)
+}
+
+func promoteLooseQuarantine(parent *Loose, tempName string, tempRoot *os.Root) error {
+	entries, err := fs.ReadDir(tempRoot.FS(), ".")
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return fmt.Errorf("object/store/loose: %w", err)
+	}
+
+	for _, entry := range entries {
+		if !entry.IsDir() {
+			return fmt.Errorf("%w: quarantine contains unexpected file %q", store.ErrInvalidObject, entry.Name())
+		}
+
+		err := promoteLooseQuarantineShard(parent, tempName, tempRoot, entry.Name())
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func promoteLooseQuarantineShard(parent *Loose, tempName string, tempRoot *os.Root, shard string) error {
+	entries, err := fs.ReadDir(tempRoot.FS(), shard)
+	if err != nil {
+		return fmt.Errorf("object/store/loose: %w", err)
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			return fmt.Errorf("%w: quarantine shard %q contains unexpected directory %q", store.ErrInvalidObject, shard, entry.Name())
+		}
+
+		objectID, err := parent.objectFormat.FromString(shard + entry.Name())
+		if err != nil {
+			return fmt.Errorf("%w: quarantine shard %q contains invalid object %q: %w", store.ErrInvalidObject, shard, entry.Name(), err)
+		}
+
+		dst, err := parent.objectPath(objectID)
+		if err != nil {
+			return err
+		}
+
+		err = parent.root.MkdirAll(shard, 0o755)
+		if err != nil {
+			return fmt.Errorf("object/store/loose: %w", err)
+		}
+
+		err = promoteLooseQuarantineObject(parent.root, filepath.Join(tempName, shard, entry.Name()), dst)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func promoteLooseQuarantineObject(root *os.Root, src, dst string) error {
+	err := root.Link(src, dst)
+	if err == nil {
+		_ = root.Remove(src)
+
+		return nil
+	}
+
+	if errors.Is(err, fs.ErrExist) {
+		_ = root.Remove(src)
+
+		return nil
+	}
+
+	return fmt.Errorf("object/store/loose: promote quarantine %q -> %q: %w", src, dst, err)
+}