Image Resolution Stage 1

This is the stage 1 effort for an image library that can be eventually used by buildah and
podman alike.  In eventuality, the main goal of the library (package) is to:

* provide a consistent approach to resolving image names in various forms (from users).
* based on the result of the above, provide image methods that in a singular spot but separate from the runtime.
* reduce the cruft and bloat in the current podman runtime.

The goal of stage 1 is to demonstrate fast, accurate image resolution for both local and remote images resulting in
an image object as part of the return.

Signed-off-by: baude <bbaude@redhat.com>

Closes: #463
Approved by: baude

1 files changed, 56 insertions, 0 deletions

diff --git a/libpod/image/parts.go b/libpod/image/parts.go
new file mode 100644
index 000000000..e4ae489f9
--- /dev/null
+++ b/libpod/image/parts.go
@@ -0,0 +1,56 @@
+package image
+
+import (
+	"fmt"
+
+	"github.com/containers/image/docker/reference"
+)
+
+// imageParts describes the parts of an image's name
+type imageParts struct {
+	transport   string
+	registry    string
+	name        string
+	tag         string
+	isTagged    bool
+	hasRegistry bool
+}
+
+// decompose breaks an input name into an imageParts description
+func decompose(input string) (imageParts, error) {
+	var (
+		parts       imageParts
+		hasRegistry bool
+		tag         string
+	)
+	imgRef, err := reference.Parse(input)
+	if err != nil {
+		return parts, err
+	}
+	ntag, isTagged, err := getTags(input)
+	if err != nil {
+		return parts, err
+	}
+	if !isTagged {
+		tag = "latest"
+	} else {
+		tag = ntag.Tag()
+	}
+	registry := reference.Domain(imgRef.(reference.Named))
+	if registry != "" {
+		hasRegistry = true
+	}
+	imageName := reference.Path(imgRef.(reference.Named))
+	return imageParts{
+		registry:    registry,
+		hasRegistry: hasRegistry,
+		name:        imageName,
+		tag:         tag,
+		isTagged:    isTagged,
+	}, nil
+}
+
+// assemble concatenates an image's parts into a string
+func (ip *imageParts) assemble() string {
+	return fmt.Sprintf("%s/%s:%s", ip.registry, ip.name, ip.tag)
+}