1 files changed, 144 insertions, 49 deletions

diff --git a/object.go b/object.go
index 20cee85..1981980 100644
--- a/object.go
+++ b/object.go
@@ -4,7 +4,11 @@ package git
 #include <git2.h>
 */
 import "C"
-import "runtime"
+import (
+	"errors"
+	"fmt"
+	"runtime"
+)
 
 type ObjectType int
 
@@ -17,14 +21,7 @@ const (
 	ObjectTag    ObjectType = C.GIT_OBJ_TAG
 )
 
-type Object interface {
-	Free()
-	Id() *Oid
-	Type() ObjectType
-	Owner() *Repository
-}
-
-type gitObject struct {
+type Object struct {
 	ptr  *C.git_object
 	repo *Repository
 }
@@ -48,65 +45,163 @@ func (t ObjectType) String() string {
 	return ""
 }
 
-func (o gitObject) Id() *Oid {
+func (o *Object) Id() *Oid {
 	return newOidFromC(C.git_object_id(o.ptr))
 }
 
-func (o gitObject) Type() ObjectType {
+func (o *Object) Type() ObjectType {
 	return ObjectType(C.git_object_type(o.ptr))
 }
 
 // Owner returns a weak reference to the repository which owns this
-// object
-func (o gitObject) Owner() *Repository {
+// object. This won't keep the underlying repository alive.
+func (o *Object) Owner() *Repository {
 	return &Repository{
 		ptr: C.git_object_owner(o.ptr),
 	}
 }
 
-func (o *gitObject) Free() {
+func dupObject(obj *Object, kind ObjectType) (*C.git_object, error) {
+	if obj.Type() != kind {
+		return nil, errors.New(fmt.Sprintf("object is not a %v", kind))
+	}
+
+	var cobj *C.git_object
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	if err := C.git_object_dup(&cobj, obj.ptr); err < 0 {
+		return nil, MakeGitError(err)
+	}
+
+	return cobj, nil
+}
+
+func allocTree(ptr *C.git_tree, repo *Repository) *Tree {
+	tree := &Tree{
+		Object: Object{
+			ptr:  (*C.git_object)(ptr),
+			repo: repo,
+		},
+		cast_ptr: ptr,
+	}
+	runtime.SetFinalizer(tree, (*Tree).Free)
+
+	return tree
+}
+
+func (o *Object) AsTree() (*Tree, error) {
+	cobj, err := dupObject(o, ObjectTree)
+	if err != nil {
+		return nil, err
+	}
+
+	return allocTree((*C.git_tree)(cobj), o.repo), nil
+}
+
+func allocCommit(ptr *C.git_commit, repo *Repository) *Commit {
+	commit := &Commit{
+		Object: Object{
+			ptr:  (*C.git_object)(ptr),
+			repo: repo,
+		},
+		cast_ptr: ptr,
+	}
+	runtime.SetFinalizer(commit, (*Commit).Free)
+
+	return commit
+}
+
+func (o *Object) AsCommit() (*Commit, error) {
+	cobj, err := dupObject(o, ObjectCommit)
+	if err != nil {
+		return nil, err
+	}
+
+	return allocCommit((*C.git_commit)(cobj), o.repo), nil
+}
+
+func allocBlob(ptr *C.git_blob, repo *Repository) *Blob {
+	blob := &Blob{
+		Object: Object{
+			ptr:  (*C.git_object)(ptr),
+			repo: repo,
+		},
+		cast_ptr: ptr,
+	}
+	runtime.SetFinalizer(blob, (*Blob).Free)
+
+	return blob
+}
+
+func (o *Object) AsBlob() (*Blob, error) {
+	cobj, err := dupObject(o, ObjectBlob)
+	if err != nil {
+		return nil, err
+	}
+
+	return allocBlob((*C.git_blob)(cobj), o.repo), nil
+}
+
+func allocTag(ptr *C.git_tag, repo *Repository) *Tag {
+	tag := &Tag{
+		Object: Object{
+			ptr:  (*C.git_object)(ptr),
+			repo: repo,
+		},
+		cast_ptr: ptr,
+	}
+	runtime.SetFinalizer(tag, (*Tag).Free)
+
+	return tag
+}
+
+func (o *Object) AsTag() (*Tag, error) {
+	cobj, err := dupObject(o, ObjectTag)
+	if err != nil {
+		return nil, err
+	}
+
+	return allocTag((*C.git_tag)(cobj), o.repo), nil
+}
+
+func (o *Object) Free() {
 	runtime.SetFinalizer(o, nil)
 	C.git_object_free(o.ptr)
 }
 
-func allocObject(cobj *C.git_object, repo *Repository) Object {
-	obj := gitObject{
-		ptr:  cobj,
-		repo: repo,
-	}
+// Peel recursively peels an object until an object of the specified type is met.
+//
+// If the query cannot be satisfied due to the object model, ErrInvalidSpec
+// will be returned (e.g. trying to peel a blob to a tree).
+//
+// If you pass ObjectAny as the target type, then the object will be peeled
+// until the type changes. A tag will be peeled until the referenced object
+// is no longer a tag, and a commit will be peeled to a tree. Any other object
+// type will return ErrInvalidSpec.
+//
+// If peeling a tag we discover an object which cannot be peeled to the target
+// type due to the object model, an error will be returned.
+func (o *Object) Peel(t ObjectType) (*Object, error) {
+	var cobj *C.git_object
 
-	switch ObjectType(C.git_object_type(cobj)) {
-	case ObjectCommit:
-		commit := &Commit{
-			gitObject: obj,
-			cast_ptr:  (*C.git_commit)(cobj),
-		}
-		runtime.SetFinalizer(commit, (*Commit).Free)
-		return commit
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
 
-	case ObjectTree:
-		tree := &Tree{
-			gitObject: obj,
-			cast_ptr:  (*C.git_tree)(cobj),
-		}
-		runtime.SetFinalizer(tree, (*Tree).Free)
-		return tree
+	if err := C.git_object_peel(&cobj, o.ptr, C.git_otype(t)); err < 0 {
+		return nil, MakeGitError(err)
+	}
 
-	case ObjectBlob:
-		blob := &Blob{
-			gitObject: obj,
-			cast_ptr:  (*C.git_blob)(cobj),
-		}
-		runtime.SetFinalizer(blob, (*Blob).Free)
-		return blob
-	case ObjectTag:
-		tag := &Tag{
-			gitObject: obj,
-			cast_ptr:  (*C.git_tag)(cobj),
-		}
-		runtime.SetFinalizer(tag, (*Tag).Free)
-		return tag
+	return allocObject(cobj, o.repo), nil
+}
+
+func allocObject(cobj *C.git_object, repo *Repository) *Object {
+	obj := &Object{
+		ptr:  cobj,
+		repo: repo,
 	}
+	runtime.SetFinalizer(obj, (*Object).Free)
 
-	return nil
+	return obj
 }