feat: add kustomization

apptests/kustomize/kustomize.go

@@ -0,0 +1,83 @@
+package kustomize
+
+import (
+	"github.com/drone/envsubst"
+	"sigs.k8s.io/kustomize/api/krusty"
+	"sigs.k8s.io/kustomize/api/resmap"
+	"sigs.k8s.io/kustomize/api/resource"
+	"sigs.k8s.io/kustomize/kyaml/filesys"
+)
+
+type Kustomize struct {
+	directory   string            // The directory where the kustomization file is located
+	substitutes map[string]string // The map of environment variables to substitute in the resources
+	resources   resmap.ResMap     // The map of resources generated by the kustomization process
+}
+
+// New creates a new Kustomize instance with the given directory and substitutes.
+func New(dir string, subs map[string]string) *Kustomize {
+	return &Kustomize{
+		directory:   dir,
+		substitutes: subs,
+		resources:   resmap.New(),
+	}
+}
+
+// Build runs the kustomization process on the directory and substitutes the
+// environment variables in the resources.
+func (k *Kustomize) Build() error {
+	opts := krusty.MakeDefaultOptions()
+	opts.Reorder = krusty.ReorderOptionLegacy
+
+	kustomizer := krusty.MakeKustomizer(opts)
+
+	// Run the kustomizer on the directory and get the resource map
+	resourceMap, err := kustomizer.Run(filesys.MakeFsOnDisk(), k.directory)
+	if err != nil {
+		return err
+	}
+
+	k.resources.Clear()
+	for _, r := range resourceMap.Resources() {
+		yaml, err := r.AsYAML()
+		if err != nil {
+			return err
+		}
+
+		out, err := envsubst.Eval(string(yaml), func(s string) string {
+			return k.substitutes[s]
+		})
+		if err != nil {
+			return err
+		}
+
+		// Convert the output string to a resource and append it to the resources map
+		res, err := newResourceFromString(out)
+		if err != nil {
+			return err
+		}
+		k.resources.Append(res)
+	}
+
+	return nil
+}
+
+// Output returns the YAML representation of the resources map as a string.
+func (k *Kustomize) Output() (string, error) {
+	yml, err := k.resources.AsYaml()
+	if err != nil {
+		return "", err
+	}
+	return string(yml), nil
+}
+
+// newResourceFromString converts a given string to a Kubernetes resource.
+func newResourceFromString(str string) (*resource.Resource, error) {
+	fc := resmap.NewFactory(&resource.Factory{})
+	resource, err := fc.NewResMapFromBytes([]byte(str))
+	if err != nil {
+		return nil, err
+	}
+
+	return resource.Resources()[0], nil
+}

apptests/kustomize/kustomize_test.go

@@ -0,0 +1,37 @@
+package kustomize
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuild(t *testing.T) {
+	wd, err := os.Getwd()
+	assert.NoError(t, err)
+
+	builder := New(
+		filepath.Join(wd, "testdata"),
+		map[string]string{
+			"name":      "test",
+			"namespace": "test",
+		},
+	)
+	err = builder.Build()
+	assert.NoError(t, err)
+
+	output, err := builder.Output()
+	assert.NoError(t, err)
+
+	// define the expected output
+	expected := `apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: test
+  namespace: test
+`
+
+	assert.Equal(t, output, expected)
+}

apptests/kustomize/testdata/kustomization.yaml

@@ -0,0 +1,4 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+- sample.yaml

apptests/kustomize/testdata/sample.yaml

@@ -0,0 +1,6 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: ${name}
+  namespace: ${namespace}