core: Reference logic implementation, and InvalidObject ObjectType

1 files changed, 124 insertions, 0 deletions

diff --git a/core/reference.go b/core/reference.go
new file mode 100644
index 0000000..9114b58
--- /dev/null
+++ b/core/reference.go
@@ -0,0 +1,124 @@
+package core
+
+import "strings"
+
+const (
+	refPrefix       = "refs/"
+	refHeadPrefix   = refPrefix + "heads/"
+	refTagPrefix    = refPrefix + "tags/"
+	refRemotePrefix = refPrefix + "remotes/"
+	refNotePrefix   = refPrefix + "notes/"
+	symrefPrefix    = "ref: "
+)
+
+// ReferenceType reference type's
+type ReferenceType int8
+
+const (
+	InvalidReference  ReferenceType = 0
+	HashReference     ReferenceType = 1
+	SymbolicReference ReferenceType = 2
+)
+
+// ReferenceName reference name's
+type ReferenceName string
+
+const (
+	HEAD ReferenceName = "HEAD"
+)
+
+// Reference is a representation of git reference
+type Reference struct {
+	t      ReferenceType
+	n      ReferenceName
+	h      Hash
+	target ReferenceName
+}
+
+// NewReferenceFromStrings creates a reference from name and target as string,
+// the resulting reference can be a SymbolicReference or a HashReference base
+// on the target provided
+func NewReferenceFromStrings(name, target string) *Reference {
+	r := &Reference{n: ReferenceName(name)}
+
+	if strings.HasPrefix(target, symrefPrefix) {
+		r.t = SymbolicReference
+		r.target = ReferenceName(target[len(symrefPrefix):])
+		return r
+	}
+
+	r.t = HashReference
+	r.h = NewHash(target)
+	return r
+}
+
+// NewSymbolicReference creates a new SymbolicReference reference
+func NewSymbolicReference(n, target ReferenceName) *Reference {
+	return &Reference{
+		t:      SymbolicReference,
+		n:      n,
+		target: target,
+	}
+}
+
+// NewHashReference creates a new HashReference reference
+func NewHashReference(n ReferenceName, h Hash) *Reference {
+	return &Reference{
+		t: HashReference,
+		n: n,
+		h: h,
+	}
+}
+
+// Type return the type of a reference
+func (r *Reference) Type() ReferenceType {
+	return r.t
+}
+
+// Name return the name of a reference
+func (r *Reference) Name() ReferenceName {
+	return r.n
+}
+
+// Hash return the hash of a hash reference
+func (r *Reference) Hash() Hash {
+	return r.h
+}
+
+// Target return the target of a symbolic reference
+func (r *Reference) Target() ReferenceName {
+	return r.target
+}
+
+// IsBranch check if a reference is a branch
+func (r *Reference) IsBranch() bool {
+	return strings.HasPrefix(string(r.n), refHeadPrefix)
+}
+
+// IsNote check if a reference is a note
+func (r *Reference) IsNote() bool {
+	return strings.HasPrefix(string(r.n), refNotePrefix)
+}
+
+// IsRemote check if a reference is a remote
+func (r *Reference) IsRemote() bool {
+	return strings.HasPrefix(string(r.n), refRemotePrefix)
+}
+
+// IsTag check if a reference is a tag
+func (r *Reference) IsTag() bool {
+	return strings.HasPrefix(string(r.n), refTagPrefix)
+}
+
+// ReferenceStorage generic storage of references
+type ReferenceStorage interface {
+	Set(Reference) error
+	Get(ReferenceName) (Reference, error)
+	Iter(ObjectType) (ReferenceIter, error)
+}
+
+// ReferenceIter is a generic closable interface for iterating over references
+type ReferenceIter interface {
+	Next() (Reference, error)
+	Close()
+}