1 files changed, 268 insertions, 0 deletions
diff --git a/plumbing/object/tag.go b/plumbing/object/tag.go
new file mode 100644
index 0000000..5ca363d
--- /dev/null
+++ b/plumbing/object/tag.go
@@ -0,0 +1,268 @@
+package object
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	stdioutil "io/ioutil"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+	"gopkg.in/src-d/go-git.v4/utils/ioutil"
+)
+
+// Tag represents an annotated tag object. It points to a single git object of
+// any type, but tags typically are applied to commit or blob objects. It
+// provides a reference that associates the target with a tag name. It also
+// contains meta-information about the tag, including the tagger, tag date and
+// message.
+//
+// https://git-scm.com/book/en/v2/Git-Internals-Git-References#Tags
+type Tag struct {
+	Hash       plumbing.Hash
+	Name       string
+	Tagger     Signature
+	Message    string
+	TargetType plumbing.ObjectType
+	Target     plumbing.Hash
+
+	s storer.EncodedObjectStorer
+}
+
+// GetTag gets a tag from an object storer and decodes it.
+func GetTag(s storer.EncodedObjectStorer, h plumbing.Hash) (*Tag, error) {
+	o, err := s.EncodedObject(plumbing.TagObject, h)
+	if err != nil {
+		return nil, err
+	}
+
+	return DecodeTag(s, o)
+}
+
+// DecodeTag decodes an encoded object into a *Commit and associates it to the
+// given object storer.
+func DecodeTag(s storer.EncodedObjectStorer, o plumbing.EncodedObject) (*Tag, error) {
+	t := &Tag{s: s}
+	if err := t.Decode(o); err != nil {
+		return nil, err
+	}
+
+	return t, nil
+}
+
+// ID returns the object ID of the tag, not the object that the tag references.
+// The returned value will always match the current value of Tag.Hash.
+//
+// ID is present to fulfill the Object interface.
+func (t *Tag) ID() plumbing.Hash {
+	return t.Hash
+}
+
+// Type returns the type of object. It always returns plumbing.TagObject.
+//
+// Type is present to fulfill the Object interface.
+func (t *Tag) Type() plumbing.ObjectType {
+	return plumbing.TagObject
+}
+
+// Decode transforms a plumbing.EncodedObject into a Tag struct.
+func (t *Tag) Decode(o plumbing.EncodedObject) (err error) {
+	if o.Type() != plumbing.TagObject {
+		return ErrUnsupportedObject
+	}
+
+	t.Hash = o.Hash()
+
+	reader, err := o.Reader()
+	if err != nil {
+		return err
+	}
+	defer ioutil.CheckClose(reader, &err)
+
+	r := bufio.NewReader(reader)
+	for {
+		line, err := r.ReadSlice('\n')
+		if err != nil && err != io.EOF {
+			return err
+		}
+
+		line = bytes.TrimSpace(line)
+		if len(line) == 0 {
+			break // Start of message
+		}
+
+		split := bytes.SplitN(line, []byte{' '}, 2)
+		switch string(split[0]) {
+		case "object":
+			t.Target = plumbing.NewHash(string(split[1]))
+		case "type":
+			t.TargetType, err = plumbing.ParseObjectType(string(split[1]))
+			if err != nil {
+				return err
+			}
+		case "tag":
+			t.Name = string(split[1])
+		case "tagger":
+			t.Tagger.Decode(split[1])
+		}
+
+		if err == io.EOF {
+			return nil
+		}
+	}
+
+	data, err := stdioutil.ReadAll(r)
+	if err != nil {
+		return err
+	}
+	t.Message = string(data)
+
+	return nil
+}
+
+// Encode transforms a Tag into a plumbing.EncodedObject.
+func (t *Tag) Encode(o plumbing.EncodedObject) error {
+	o.SetType(plumbing.TagObject)
+	w, err := o.Writer()
+	if err != nil {
+		return err
+	}
+	defer ioutil.CheckClose(w, &err)
+
+	if _, err = fmt.Fprintf(w,
+		"object %s\ntype %s\ntag %s\ntagger ",
+		t.Target.String(), t.TargetType.Bytes(), t.Name); err != nil {
+		return err
+	}
+
+	if err = t.Tagger.Encode(w); err != nil {
+		return err
+	}
+
+	if _, err = fmt.Fprint(w, "\n\n"); err != nil {
+		return err
+	}
+
+	if _, err = fmt.Fprint(w, t.Message); err != nil {
+		return err
+	}
+
+	return err
+}
+
+// Commit returns the commit pointed to by the tag. If the tag points to a
+// different type of object ErrUnsupportedObject will be returned.
+func (t *Tag) Commit() (*Commit, error) {
+	if t.TargetType != plumbing.CommitObject {
+		return nil, ErrUnsupportedObject
+	}
+
+	o, err := t.s.EncodedObject(plumbing.CommitObject, t.Target)
+	if err != nil {
+		return nil, err
+	}
+
+	return DecodeCommit(t.s, o)
+}
+
+// Tree returns the tree pointed to by the tag. If the tag points to a commit
+// object the tree of that commit will be returned. If the tag does not point
+// to a commit or tree object ErrUnsupportedObject will be returned.
+func (t *Tag) Tree() (*Tree, error) {
+	switch t.TargetType {
+	case plumbing.CommitObject:
+		c, err := t.Commit()
+		if err != nil {
+			return nil, err
+		}
+
+		return c.Tree()
+	case plumbing.TreeObject:
+		return GetTree(t.s, t.Target)
+	default:
+		return nil, ErrUnsupportedObject
+	}
+}
+
+// Blob returns the blob pointed to by the tag. If the tag points to a
+// different type of object ErrUnsupportedObject will be returned.
+func (t *Tag) Blob() (*Blob, error) {
+	if t.TargetType != plumbing.BlobObject {
+		return nil, ErrUnsupportedObject
+	}
+
+	return GetBlob(t.s, t.Target)
+}
+
+// Object returns the object pointed to by the tag.
+func (t *Tag) Object() (Object, error) {
+	o, err := t.s.EncodedObject(t.TargetType, t.Target)
+	if err != nil {
+		return nil, err
+	}
+
+	return DecodeObject(t.s, o)
+}
+
+// String returns the meta information contained in the tag as a formatted
+// string.
+func (t *Tag) String() string {
+	obj, _ := t.Object()
+
+	return fmt.Sprintf(
+		"%s %s\nTagger: %s\nDate:   %s\n\n%s\n%s",
+		plumbing.TagObject, t.Name, t.Tagger.String(), t.Tagger.When.Format(DateFormat),
+		t.Message, objectAsString(obj),
+	)
+}
+
+// TagIter provides an iterator for a set of tags.
+type TagIter struct {
+	storer.EncodedObjectIter
+	s storer.EncodedObjectStorer
+}
+
+// NewTagIter returns a TagIter for the given object storer and underlying
+// object iterator.
+//
+// The returned TagIter will automatically skip over non-tag objects.
+func NewTagIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) *TagIter {
+	return &TagIter{iter, s}
+}
+
+// Next moves the iterator to the next tag and returns a pointer to it. If it
+// has reached the end of the set it will return io.EOF.
+func (iter *TagIter) Next() (*Tag, error) {
+	obj, err := iter.EncodedObjectIter.Next()
+	if err != nil {
+		return nil, err
+	}
+
+	return DecodeTag(iter.s, obj)
+}
+
+// ForEach call the cb function for each tag contained on this iter until
+// an error happends or the end of the iter is reached. If ErrStop is sent
+// the iteration is stop but no error is returned. The iterator is closed.
+func (iter *TagIter) ForEach(cb func(*Tag) error) error {
+	return iter.EncodedObjectIter.ForEach(func(obj plumbing.EncodedObject) error {
+		t, err := DecodeTag(iter.s, obj)
+		if err != nil {
+			return err
+		}
+
+		return cb(t)
+	})
+}
+
+func objectAsString(obj Object) string {
+	switch o := obj.(type) {
+	case *Commit:
+		return o.String()
+	case *Tag:
+		return o.String()
+	}
+
+	return ""
+}