Urgh I made some wrong amends and I'm too tired to separate the commits out this time

ancestor: Split out of reachability
mergebase: Add merge base routines
internal/commitquery: Add commit query context engine thingy
internal/peel: Shared tag peeling
errors: Shared object query errors
internal/testgit: Add rooted repo helpers; remove raw path access
objectstore/memory: Add in-memory object store
objectid: Add Compare helper

9 files changed, 160 insertions, 0 deletions

diff --git a/objectstore/memory/add.go b/objectstore/memory/add.go
new file mode 100644
index 00000000..80d0022f
--- /dev/null
+++ b/objectstore/memory/add.go
@@ -0,0 +1,21 @@
+package memory
+
+import (
+	"codeberg.org/lindenii/furgit/objectheader"
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+// AddObject stores one object body and returns its object ID.
+func (store *Store) AddObject(ty objecttype.Type, body []byte) objectid.ObjectID {
+	header, ok := objectheader.Encode(ty, int64(len(body)))
+	if !ok {
+		panic("failed to encode object header")
+	}
+
+	raw := append(append([]byte(nil), header...), body...)
+	id := store.algo.Sum(raw)
+	store.objects[id] = storedObject{ty: ty, content: append([]byte(nil), body...)}
+
+	return id
+}
diff --git a/objectstore/memory/algorithm.go b/objectstore/memory/algorithm.go
new file mode 100644
index 00000000..db43272e
--- /dev/null
+++ b/objectstore/memory/algorithm.go
@@ -0,0 +1,8 @@
+package memory
+
+import "codeberg.org/lindenii/furgit/objectid"
+
+// Algorithm returns the object ID algorithm used by the store.
+func (store *Store) Algorithm() objectid.Algorithm {
+	return store.algo
+}
diff --git a/objectstore/memory/doc.go b/objectstore/memory/doc.go
new file mode 100644
index 00000000..cb40d466
--- /dev/null
+++ b/objectstore/memory/doc.go
@@ -0,0 +1,2 @@
+// Package memory provides one in-memory object store.
+package memory
diff --git a/objectstore/memory/object.go b/objectstore/memory/object.go
new file mode 100644
index 00000000..940af328
--- /dev/null
+++ b/objectstore/memory/object.go
@@ -0,0 +1,9 @@
+package memory
+
+import "codeberg.org/lindenii/furgit/objecttype"
+
+// storedObject is one in-memory object entry.
+type storedObject struct {
+	ty      objecttype.Type
+	content []byte
+}
diff --git a/objectstore/memory/read_bytes.go b/objectstore/memory/read_bytes.go
new file mode 100644
index 00000000..31c5b3d1
--- /dev/null
+++ b/objectstore/memory/read_bytes.go
@@ -0,0 +1,37 @@
+package memory
+
+import (
+	"codeberg.org/lindenii/furgit/objectheader"
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objectstore"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+// ReadBytesFull reads one full object, including the object header.
+func (store *Store) ReadBytesFull(id objectid.ObjectID) ([]byte, error) {
+	obj, ok := store.objects[id]
+	if !ok {
+		return nil, objectstore.ErrObjectNotFound
+	}
+
+	header, ok := objectheader.Encode(obj.ty, int64(len(obj.content)))
+	if !ok {
+		panic("failed to encode object header")
+	}
+
+	raw := make([]byte, len(header)+len(obj.content))
+	copy(raw, header)
+	copy(raw[len(header):], obj.content)
+
+	return raw, nil
+}
+
+// ReadBytesContent reads one object body.
+func (store *Store) ReadBytesContent(id objectid.ObjectID) (objecttype.Type, []byte, error) {
+	obj, ok := store.objects[id]
+	if !ok {
+		return objecttype.TypeInvalid, nil, objectstore.ErrObjectNotFound
+	}
+
+	return obj.ty, append([]byte(nil), obj.content...), nil
+}
diff --git a/objectstore/memory/read_header.go b/objectstore/memory/read_header.go
new file mode 100644
index 00000000..1d0aff15
--- /dev/null
+++ b/objectstore/memory/read_header.go
@@ -0,0 +1,17 @@
+package memory
+
+import (
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objectstore"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+// ReadHeader reads one object header.
+func (store *Store) ReadHeader(id objectid.ObjectID) (objecttype.Type, int64, error) {
+	obj, ok := store.objects[id]
+	if !ok {
+		return objecttype.TypeInvalid, 0, objectstore.ErrObjectNotFound
+	}
+
+	return obj.ty, int64(len(obj.content)), nil
+}
diff --git a/objectstore/memory/read_reader.go b/objectstore/memory/read_reader.go
new file mode 100644
index 00000000..2e3feda1
--- /dev/null
+++ b/objectstore/memory/read_reader.go
@@ -0,0 +1,29 @@
+package memory
+
+import (
+	"bytes"
+	"io"
+
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objecttype"
+)
+
+// ReadReaderFull reads one full object through a reader.
+func (store *Store) ReadReaderFull(id objectid.ObjectID) (io.ReadCloser, error) {
+	raw, err := store.ReadBytesFull(id)
+	if err != nil {
+		return nil, err
+	}
+
+	return io.NopCloser(bytes.NewReader(raw)), nil
+}
+
+// ReadReaderContent reads one object body through a reader.
+func (store *Store) ReadReaderContent(id objectid.ObjectID) (objecttype.Type, int64, io.ReadCloser, error) {
+	ty, content, err := store.ReadBytesContent(id)
+	if err != nil {
+		return objecttype.TypeInvalid, 0, nil, err
+	}
+
+	return ty, int64(len(content)), io.NopCloser(bytes.NewReader(content)), nil
+}
diff --git a/objectstore/memory/read_size.go b/objectstore/memory/read_size.go
new file mode 100644
index 00000000..3ca7789a
--- /dev/null
+++ b/objectstore/memory/read_size.go
@@ -0,0 +1,13 @@
+package memory
+
+import "codeberg.org/lindenii/furgit/objectid"
+
+// ReadSize reads one object size.
+func (store *Store) ReadSize(id objectid.ObjectID) (int64, error) {
+	_, size, err := store.ReadHeader(id)
+	if err != nil {
+		return 0, err
+	}
+
+	return size, nil
+}
diff --git a/objectstore/memory/store.go b/objectstore/memory/store.go
new file mode 100644
index 00000000..f7513094
--- /dev/null
+++ b/objectstore/memory/store.go
@@ -0,0 +1,24 @@
+package memory
+
+import (
+	"codeberg.org/lindenii/furgit/objectid"
+)
+
+// Store is one in-memory object store.
+type Store struct {
+	algo    objectid.Algorithm
+	objects map[objectid.ObjectID]storedObject
+}
+
+// New builds one empty in-memory store for one object format.
+func New(algo objectid.Algorithm) *Store {
+	return &Store{
+		algo:    algo,
+		objects: make(map[objectid.ObjectID]storedObject),
+	}
+}
+
+// Close closes the in-memory store.
+func (store *Store) Close() error {
+	return nil
+}