1 files changed, 108 insertions, 0 deletions
diff --git a/pkg/name/tag.go b/pkg/name/tag.go
new file mode 100644
index 0000000..66bd1be
--- /dev/null
+++ b/pkg/name/tag.go
@@ -0,0 +1,108 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package name
+
+import (
+	"strings"
+)
+
+const (
+	// TODO(dekkagaijin): use the docker/distribution regexes for validation.
+	tagChars = "abcdefghijklmnopqrstuvwxyz0123456789_-.ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	tagDelim = ":"
+)
+
+// Tag stores a docker tag name in a structured form.
+type Tag struct {
+	Repository
+	tag      string
+	original string
+}
+
+// Ensure Tag implements Reference
+var _ Reference = (*Tag)(nil)
+
+// Context implements Reference.
+func (t Tag) Context() Repository {
+	return t.Repository
+}
+
+// Identifier implements Reference.
+func (t Tag) Identifier() string {
+	return t.TagStr()
+}
+
+// TagStr returns the tag component of the Tag.
+func (t Tag) TagStr() string {
+	return t.tag
+}
+
+// Name returns the name from which the Tag was derived.
+func (t Tag) Name() string {
+	return t.Repository.Name() + tagDelim + t.TagStr()
+}
+
+// String returns the original input string.
+func (t Tag) String() string {
+	return t.original
+}
+
+// Scope returns the scope required to perform the given action on the tag.
+func (t Tag) Scope(action string) string {
+	return t.Repository.Scope(action)
+}
+
+func checkTag(name string) error {
+	return checkElement("tag", name, tagChars, 1, 128)
+}
+
+// NewTag returns a new Tag representing the given name, according to the given strictness.
+func NewTag(name string, opts ...Option) (Tag, error) {
+	opt := makeOptions(opts...)
+	base := name
+	tag := ""
+
+	// Split on ":"
+	parts := strings.Split(name, tagDelim)
+	// Verify that we aren't confusing a tag for a hostname w/ port for the purposes of weak validation.
+	if len(parts) > 1 && !strings.Contains(parts[len(parts)-1], regRepoDelimiter) {
+		base = strings.Join(parts[:len(parts)-1], tagDelim)
+		tag = parts[len(parts)-1]
+	}
+
+	// We don't require a tag, but if we get one check it's valid,
+	// even when not being strict.
+	// If we are being strict, we want to validate the tag regardless in case
+	// it's empty.
+	if tag != "" || opt.strict {
+		if err := checkTag(tag); err != nil {
+			return Tag{}, err
+		}
+	}
+
+	if tag == "" {
+		tag = opt.defaultTag
+	}
+
+	repo, err := NewRepository(base, opts...)
+	if err != nil {
+		return Tag{}, err
+	}
+	return Tag{
+		Repository: repo,
+		tag:        tag,
+		original:   name,
+	}, nil
+}