1 files changed, 95 insertions, 30 deletions
diff --git a/object/store/packed/packed.go b/object/store/packed/packed.go
index c0961508..897b3b98 100644
--- a/object/store/packed/packed.go
+++ b/object/store/packed/packed.go
@@ -1,36 +1,101 @@
 package packed
 
-// import (
-// 	"os"
-//
-// 	"lindenii.org/go/furgit/object/id"
-// 	"lindenii.org/go/furgit/object/store"
-// )
+import (
+	"errors"
+	"os"
+	"sync"
+
+	"lindenii.org/go/furgit/internal/cache/clock"
+	"lindenii.org/go/furgit/internal/mru"
+	"lindenii.org/go/furgit/object/id"
+	"lindenii.org/go/furgit/object/store"
+)
+
+// ErrMalformedPackedStore reports that
+// a pack or pack index in the store is
+// truncated, inconsistent, or otherwise corrupt.
+var ErrMalformedPackedStore = errors.New("object/store/packed: malformed packed store")
+
+// Packed reads Git objects from pack/index files
+// under an objects/pack root.
 //
-// // Packed reads Git objects from pack/index files under an objects/pack root,
-// // and ingests incoming pack streams into it.
-// //
-// // Labels: Close-Caller.
-// type Packed struct {
-// 	// root is the objects/pack directory capability
-// 	// used for all pack and index file access.
-// 	// Packed borrows this root.
-// 	root *os.Root
-// 	// objectFormat is the expected object format for lookups.
-// 	objectFormat id.ObjectFormat
-// }
+// Packs appearing after construction are only visible
+// after an explicit [Packed.Refresh].
 //
-// var (
-// 	_ store.ObjectReader = (*Packed)(nil)
-// 	_ store.PackWriter   = (*Packed)(nil)
-// )
+// Labels: Close-Caller.
+type Packed struct {
+	// root is the objects/pack directory
+	// used for all pack and index file access.
+	root *os.Root
+
+	// objectFormat is the expected object format for lookups.
+	objectFormat id.ObjectFormat
+
+	// order contains the packs to probe, MRU-first.
+	order *mru.Order[*pack]
+
+	// baseCache caches delta bases consumed during resolution.
+	baseCache *clock.Clock[baseKey, cachedBase]
+
+	// refreshMu serializes Refresh.
+	// Readers uses none of these.
+	refreshMu sync.Mutex
+
+	// byName supports reusing surviving packs across Refresh,
+	// and retired holds dropped packs until Close,
+	// since concurrent readers may still use them.
+	byName map[string]*pack
+
+	retired []*pack
+}
+
+var _ store.ObjectReader = (*Packed)(nil)
+
+// New creates a packed-object store rooted at an objects/pack directory,
+// performing an initial Refresh.
 //
-// // New creates a packed-object store rooted at an objects/pack directory.
-// //
-// // Labels: Deps-Borrowed, Life-Parent.
-// func New(root *os.Root, objectFormat id.ObjectFormat) (*Packed, error)
+// Labels: Deps-Borrowed, Life-Parent.
+func New(root *os.Root, objectFormat id.ObjectFormat) (*Packed, error) {
+	if objectFormat.Size() == 0 {
+		return nil, id.ErrInvalidObjectFormat
+	}
+
+	packed := &Packed{
+		root:         root,
+		objectFormat: objectFormat,
+		order:        mru.New[*pack](mru.Options{Interval: 48}),
+		baseCache:    newBaseCache(),
+		refreshMu:    sync.Mutex{},
+		byName:       nil,
+		retired:      nil,
+	}
+
+	err := packed.Refresh()
+	if err != nil {
+		return nil, err
+	}
+
+	return packed, nil
+}
+
+// Close releases mapped pack/index resources associated with the store.
 //
-// // Close releases mapped pack/index resources associated with the store.
-// //
-// // Labels: MT-Unsafe.
-// func (packed *Packed) Close() error
+// Labels: MT-Unsafe.
+func (packed *Packed) Close() error {
+	errs := make([]error, 0, len(packed.byName)+len(packed.retired))
+
+	for _, p := range packed.byName {
+		errs = append(errs, p.close())
+	}
+
+	for _, p := range packed.retired {
+		errs = append(errs, p.close())
+	}
+
+	packed.byName = nil
+	packed.retired = nil
+
+	packed.baseCache.Clear()
+
+	return errors.Join(errs...)
+}