pkg/utils: Resolve the actual container, image and release to be used

... based on the default values, and those overridden by the user.

https://github.com/containers/toolbox/pull/318

src/pkg/utils/utils.go

@@ -440,6 +440,53 @@ func JoinJSON(joinkey string, maps ...[]map[string]interface{}) []map[string]int
 	return json
 }
 
+// ResolveContainerAndImageNames takes care of standardizing names of containers and images.
+//
+// If no image name is specified then the base image will reflect the platform of the host (even the version).
+// If no container name is specified then the name of the image will be used.
+//
+// If the host system is unknown then the base image will be 'fedora-toolbox' with a default version
+func ResolveContainerAndImageNames(container, image, release string) (string, string, string, error) {
+	logrus.Debug("Resolving container and image names")
+	logrus.Debugf("Container: '%s'", container)
+	logrus.Debugf("Image: '%s'", image)
+	logrus.Debugf("Release: '%s'", release)
+
+	if release == "" {
+		release = releaseDefault
+	}
+
+	if image == "" {
+		image = "fedora-toolbox:" + release
+	} else {
+		release = ImageReferenceGetTag(image)
+		if release == "" {
+			release = releaseDefault
+		}
+	}
+
+	if container == "" {
+		basename := ImageReferenceGetBasename(image)
+		if basename == "" {
+			return "", "", "", fmt.Errorf("failed to get the basename of image %s", image)
+		}
+
+		container = basename
+
+		tag := ImageReferenceGetTag(image)
+		if tag != "" {
+			container = container + "-" + tag
+		}
+	}
+
+	logrus.Debug("Resolved container and image names")
+	logrus.Debugf("Container: '%s'", container)
+	logrus.Debugf("Image: '%s'", image)
+	logrus.Debugf("Release: '%s'", release)
+
+	return container, image, release, nil
+}
+
 func ShowManual(manual string) error {
 	manBinary, err := exec.LookPath("man")
 	if err != nil {