skeleton for kustomize function

api/internal/plugins/fnplugin/fnplugin.go

@@ -0,0 +1,91 @@
+package fnplugin
+
+import (
+	"sigs.k8s.io/kustomize/api/resmap"
+	"sigs.k8s.io/kustomize/api/resource"
+	"sigs.k8s.io/kustomize/kyaml/fn/runtime/runtimeutil"
+	"sigs.k8s.io/kustomize/kyaml/runfn"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+// FnPlugin holds the information about thie function
+type FnPlugin struct {
+	// Plugin configuration data.
+	cfg []byte
+
+	// PluginHelpers
+	h *resmap.PluginHelpers
+
+	// Function runner
+	RunFns runfn.RunFns
+}
+
+func bytesToRNode(yml []byte) (*yaml.RNode, error) {
+	rnode, err := yaml.Parse(string(yml))
+	if err != nil {
+		return nil, err
+	}
+	return rnode, nil
+}
+
+func resourceToRNode(res *resource.Resource) (*yaml.RNode, error) {
+	yml, err := res.AsYAML()
+	if err != nil {
+		return nil, err
+	}
+
+	return bytesToRNode(yml)
+}
+
+func getFunctionSpec(res *resource.Resource) *runtimeutil.FunctionSpec {
+	rnode, err := resourceToRNode(res)
+	if err != nil {
+		return nil
+	}
+
+	return runtimeutil.GetFunctionSpec(rnode)
+}
+
+// IsFnPlugin returns a resource is a function plugin spec or not
+func IsFnPlugin(res *resource.Resource) bool {
+	return getFunctionSpec(res) != nil
+}
+
+// NewFnPlugin returns a FnPlugin struct
+func NewFnPlugin(res *resource.Resource) *FnPlugin {
+	return &FnPlugin{}
+}
+
+// Config accepts the plugin helper and plugin config
+func (f *FnPlugin) Config(h *resmap.PluginHelpers, config []byte) error {
+	f.h = h
+	f.cfg = config
+	// config is the content of the config file for the functions.
+	// If there are multiple functions in on config file, they will
+	// be passed in one by one.
+	fn, err := bytesToRNode(config)
+	if err != nil {
+		return err
+	}
+
+	f.RunFns.Functions = append(f.RunFns.Functions, fn)
+
+	return nil
+}
+
+// Transform does the transformation when the plugin is a transformer
+func (f *FnPlugin) Transform(rm resmap.ResMap) error {
+	// convert input to ResourceList
+	// add functionConfig
+	// invoke function
+	// convert back to ResMap
+	return nil
+}
+
+// invoke call the actual function and send the input to it. It captures
+// and returns the output
+func (f *FnPlugin) invoke(input []byte) ([]byte, error) {
+	// setup input and output
+	var output []byte
+	return output, nil
+}