[Refactor] Move image/ to internal

This PR is an effort towards reducing the public surface
of APIs. It move image/ to internal/image

Signed-off-by: Varsha Prasad Narsing <varshaprasad96@gmail.com>
(cherry picked from commit 1f5890709fdc17de6f44f42b5138dd0f7e64bc74)

api/internal/image/image.go

@@ -0,0 +1,66 @@
+// Copyright 2020 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package image
+
+import (
+	"regexp"
+	"strings"
+)
+
+// IsImageMatched returns true if the value of t is identical to the
+// image name in the full image name and tag as given by s.
+func IsImageMatched(s, t string) bool {
+	// Tag values are limited to [a-zA-Z0-9_.{}-].
+	// Some tools like Bazel rules_k8s allow tag patterns with {} characters.
+	// More info: https://github.com/bazelbuild/rules_k8s/pull/423
+	pattern, _ := regexp.Compile("^" + t + "(:[a-zA-Z0-9_.{}-]*)?(@sha256:[a-zA-Z0-9_.{}-]*)?$")
+	return pattern.MatchString(s)
+}
+
+// Split separates and returns the name and tag parts
+// from the image string using either colon `:` or at `@` separators.
+// image reference pattern: [[host[:port]/]component/]component[:tag][@digest]
+func Split(imageName string) (name string, tag string, digest string) {
+	// check if image name contains a domain
+	// if domain is present, ignore domain and check for `:`
+	searchName := imageName
+	slashIndex := strings.Index(imageName, "/")
+	if slashIndex > 0 {
+		searchName = imageName[slashIndex:]
+	} else {
+		slashIndex = 0
+	}
+
+	id := strings.Index(searchName, "@")
+	ic := strings.Index(searchName, ":")
+
+	// no tag or digest
+	if ic < 0 && id < 0 {
+		return imageName, "", ""
+	}
+
+	// digest only
+	if id >= 0 && (id < ic || ic < 0) {
+		id += slashIndex
+		name = imageName[:id]
+		digest = strings.TrimPrefix(imageName[id:], "@")
+		return name, "", digest
+	}
+
+	// tag and digest
+	if id >= 0 && ic >= 0 {
+		id += slashIndex
+		ic += slashIndex
+		name = imageName[:ic]
+		tag = strings.TrimPrefix(imageName[ic:id], ":")
+		digest = strings.TrimPrefix(imageName[id:], "@")
+		return name, tag, digest
+	}
+
+	// tag only
+	ic += slashIndex
+	name = imageName[:ic]
+	tag = strings.TrimPrefix(imageName[ic:], ":")
+	return name, tag, ""
+}

api/internal/image/image_test.go

@@ -0,0 +1,126 @@
+// Copyright 2020 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package image_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"sigs.k8s.io/kustomize/api/internal/image"
+)
+
+func TestIsImageMatched(t *testing.T) {
+	testCases := []struct {
+		testName  string
+		value     string
+		name      string
+		isMatched bool
+	}{
+		{
+			testName:  "identical",
+			value:     "nginx",
+			name:      "nginx",
+			isMatched: true,
+		},
+		{
+			testName:  "name is match with tag",
+			value:     "nginx:12345",
+			name:      "nginx",
+			isMatched: true,
+		},
+		{
+			testName:  "name is match with digest",
+			value:     "nginx@sha256:xyz",
+			name:      "nginx",
+			isMatched: true,
+		},
+		{
+			testName:  "name is match with tag and digest",
+			value:     "nginx:12345@sha256:xyz",
+			name:      "nginx",
+			isMatched: true,
+		},
+		{
+			testName:  "name is not a match",
+			value:     "apache:12345",
+			name:      "nginx",
+			isMatched: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.testName, func(t *testing.T) {
+			assert.Equal(t, tc.isMatched, image.IsImageMatched(tc.value, tc.name))
+		})
+	}
+}
+
+func TestSplit(t *testing.T) {
+	testCases := []struct {
+		testName string
+		value    string
+		name     string
+		tag      string
+		digest   string
+	}{
+		{
+			testName: "no tag",
+			value:    "nginx",
+			name:     "nginx",
+			tag:      "",
+			digest:   "",
+		},
+		{
+			testName: "with tag",
+			value:    "nginx:1.2.3",
+			name:     "nginx",
+			tag:      "1.2.3",
+			digest:   "",
+		},
+		{
+			testName: "with digest",
+			value:    "nginx@sha256:12345",
+			name:     "nginx",
+			tag:      "",
+			digest:   "sha256:12345",
+		},
+		{
+			testName: "with tag and digest",
+			value:    "nginx:1.2.3@sha256:12345",
+			name:     "nginx",
+			tag:      "1.2.3",
+			digest:   "sha256:12345",
+		},
+		{
+			testName: "with domain",
+			value:    "docker.io/nginx:1.2.3",
+			name:     "docker.io/nginx",
+			tag:      "1.2.3",
+			digest:   "",
+		},
+		{
+			testName: "with domain and port",
+			value:    "foo.com:443/nginx:1.2.3",
+			name:     "foo.com:443/nginx",
+			tag:      "1.2.3",
+			digest:   "",
+		},
+		{
+			testName: "with domain, port, tag and digest",
+			value:    "foo.com:443/nginx:1.2.3@sha256:12345",
+			name:     "foo.com:443/nginx",
+			tag:      "1.2.3",
+			digest:   "sha256:12345",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.testName, func(t *testing.T) {
+			name, tag, digest := image.Split(tc.value)
+			assert.Equal(t, tc.name, name)
+			assert.Equal(t, tc.tag, tag)
+			assert.Equal(t, tc.digest, digest)
+		})
+	}
+}