scale.go

// SPDX-License-Identifier: Apache-2.0

package typeset

import "k8s.io/apimachinery/pkg/runtime/schema"

// ScaleSourceBuiltinRegistry labels a ScaleBinding resolved from the built-in
// registry below, so it reads identically to a CRD-sourced binding for the writer.
const ScaleSourceBuiltinRegistry = "builtin-registry"

// builtinSpecReplicasPath is the parent replica path every currently-served
// built-in scalable resource maps scale.spec.replicas onto. The version is
// intentionally ignored: this path is stable for these resources across their
// served versions.
const builtinSpecReplicasPath = ".spec.replicas"

// builtinScaleResponseGVK is the standardized object Kubernetes returns for a
// built-in /scale call.
func builtinScaleResponseGVK() schema.GroupVersionKind {
	return schema.GroupVersionKind{Group: "autoscaling", Version: "v1", Kind: "Scale"}
}

// builtinScalable is the closed set of currently-served built-in scalable
// resources, keyed by API group and plural resource. Each maps scale.spec.replicas
// to the parent's .spec.replicas. CRDs draw the path from the CRD definition and
// aggregated APIs have no generic discovery field, so neither is listed here; both
// must resolve their own binding rather than default to .spec.replicas.
func builtinScalable(group, resource string) bool {
	switch {
	case group == "apps" && resource == "deployments",
		group == "apps" && resource == "statefulsets",
		group == "apps" && resource == "replicasets",
		group == "" && resource == "replicationcontrollers":
		return true
	default:
		return false
	}
}

// BuiltinScale returns the /scale binding for a currently-served built-in scalable
// resource identified by API group and plural resource. ok is false for any other
// resource — a CRD, an aggregated API, or a non-scalable built-in — in which case
// the scale event must be resolved elsewhere or dropped, never defaulted to
// .spec.replicas. It is the single source of built-in scale facts, shared by the
// cluster registry (origin/scale enrichment) and the audit consumer (scale write).
func BuiltinScale(group, resource string) (ScaleBinding, bool) {
	if !builtinScalable(group, resource) {
		return ScaleBinding{}, false
	}
	return ScaleBinding{
		Enabled:          true,
		Source:           ScaleSourceBuiltinRegistry,
		ResponseGVK:      builtinScaleResponseGVK(),
		SpecReplicasPath: builtinSpecReplicasPath,
		Usable:           true,
	}, true
}