package k8score

import (
	"bytes"
	"crypto/sha256"
	"encoding/hex"

	appsv1 "k8s.io/api/apps/v1"
	autoscalingv2 "k8s.io/api/autoscaling/v2"
	batchv1 "k8s.io/api/batch/v1"
	corev1 "k8s.io/api/core/v1"
	networkingv1 "k8s.io/api/networking/v1"
	policyv1 "k8s.io/api/policy/v1"
	storagev1 "k8s.io/api/storage/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
)

const lastAppliedAnnotation = "kubectl.kubernetes.io/last-applied-configuration"

// HelmReleaseSecretType is the type Helm gives the Secrets that store
// releases, one Secret per revision.
const HelmReleaseSecretType corev1.SecretType = "helm.sh/release.v1"

// DropManagedFields is a SharedInformer transform that reduces memory usage
// by removing managedFields and heavy annotations from cached objects.
// This is the union of transforms used by both Radar and skyhook-connector.
//
// It also replaces each value of a Helm release Secret (see
// IsHelmReleaseSecret) with a digest of it. Each value is a full encoded
// release, typically 30-400KB, and Helm keeps up to 10 revisions per release
// by default, so on a Helm-heavy cluster they are most of the cache. Keys stay,
// so key counts and key names are unchanged, and a changed value still
// compares as changed. The digests are not Secret data: anything that serves
// a cached Helm release Secret must use WithoutHelmReleaseValues, and
// anything that needs a value must read the Secret from the API server.
func DropManagedFields(obj any) (any, error) {
	if meta, ok := obj.(metav1.Object); ok {
		meta.SetManagedFields(nil)
	}

	if secret, ok := obj.(*corev1.Secret); ok && IsHelmReleaseSecret(secret) {
		for key, value := range secret.Data {
			// Watch-list informers run the transform twice on objects present
			// at startup, so a value may already be a digest.
			if !isHelmReleaseValueDigest(value) {
				secret.Data[key] = helmReleaseValueDigest(value)
			}
		}
	}

	// Special handling for Events — aggressively strip to essentials
	if event, ok := obj.(*corev1.Event); ok {
		return &corev1.Event{
			ObjectMeta: metav1.ObjectMeta{
				Name:              event.Name,
				Namespace:         event.Namespace,
				UID:               event.UID,
				ResourceVersion:   event.ResourceVersion,
				CreationTimestamp: event.CreationTimestamp,
			},
			InvolvedObject: event.InvolvedObject,
			Related:        event.Related,
			Reason:         event.Reason,
			Message:        event.Message,
			Type:           event.Type,
			Count:          event.Count,
			FirstTimestamp: event.FirstTimestamp,
			LastTimestamp:  event.LastTimestamp,
			// Events recorded through events.k8s.io carry their times here
			// instead of in First/LastTimestamp.
			EventTime: event.EventTime,
			Series:    event.Series,
		}, nil
	}

	// Drop heavy annotations from common resources
	switch obj.(type) {
	case *corev1.Pod, *corev1.Service, *corev1.Node, *corev1.Namespace,
		*corev1.PersistentVolumeClaim, *corev1.PersistentVolume,
		*corev1.ConfigMap, *corev1.Secret, *corev1.ServiceAccount,
		*appsv1.Deployment, *appsv1.DaemonSet, *appsv1.StatefulSet, *appsv1.ReplicaSet,
		*networkingv1.Ingress, *networkingv1.IngressClass,
		*batchv1.Job, *batchv1.CronJob,
		*autoscalingv2.HorizontalPodAutoscaler,
		*policyv1.PodDisruptionBudget, *storagev1.StorageClass:
		if meta, ok := obj.(metav1.Object); ok && meta.GetAnnotations() != nil {
			delete(meta.GetAnnotations(), lastAppliedAnnotation)
		}
	}

	return obj, nil
}

// IsHelmReleaseSecret reports whether secret is a Helm release Secret. The
// informer cache holds these with digests in place of their values (see
// DropManagedFields).
func IsHelmReleaseSecret(secret *corev1.Secret) bool {
	return secret != nil && secret.Type == HelmReleaseSecretType
}

// WithoutHelmReleaseValues returns secret as it may be served from the
// cache: for a Helm release Secret, a copy whose keys have no values; any
// other Secret unchanged. It never modifies secret.
func WithoutHelmReleaseValues(secret *corev1.Secret) *corev1.Secret {
	if !IsHelmReleaseSecret(secret) || len(secret.Data) == 0 {
		return secret
	}
	out := *secret
	out.Data = make(map[string][]byte, len(secret.Data))
	for key := range secret.Data {
		out.Data[key] = nil
	}
	return &out
}

const helmReleaseDigestPrefix = "radar-cache-digest:sha256:"

func helmReleaseValueDigest(value []byte) []byte {
	sum := sha256.Sum256(value)
	return []byte(helmReleaseDigestPrefix + hex.EncodeToString(sum[:]))
}

func isHelmReleaseValueDigest(value []byte) bool {
	return len(value) == len(helmReleaseDigestPrefix)+2*sha256.Size && bytes.HasPrefix(value, []byte(helmReleaseDigestPrefix))
}

// DropUnstructuredManagedFields is the dynamic-cache counterpart of
// DropManagedFields. It's the SharedInformer transform for dynamic
// informers — which carry *unstructured.Unstructured — and mirrors the
// typed-cache transform's intent: shrink cached objects before they hit
// the store.
//
// Mutates in-place. This is correct here: SharedInformer transforms run
// exactly once per object before the cache stores it, and the object is
// not visible to any other reader until after the transform returns. Do
// NOT call this from places that hand you an object off the cache —
// those need StripUnstructuredFields which deep-copies.
//
// Always strips:
//   - metadata.managedFields
//   - kubectl.kubernetes.io/last-applied-configuration. GitOps drift
//     detection needs this annotation, but it pulls live objects via a
//     dedicated direct-GET path (DynamicResourceCache.GetDirectPreserveLastApplied)
//     so the informer cache never has to retain it — which matters
//     because the dynamic cache can host core kinds (apps/Deployment,
//     /v1/Service, etc.) referenced from an Argo Application's
//     status.resources, where retaining last-applied across every object
//     cluster-wide would be a meaningful memory regression to power a
//     per-page diagnostic.
//
// For CustomResourceDefinitions specifically, also strips:
//   - spec.versions[].schema — the OpenAPI v3 schema. On operator-heavy
//     clusters a single CRD's schema is 50-100KB (ArgoCD, cert-manager,
//     Istio) and 100+ CRDs easily produce a multi-MB list response.
//     Radar doesn't render CRD schemas; a future "inspect CRD schema"
//     feature should fetch fresh from the API server.
//   - spec.conversion — webhook config. Not rendered.
//
// Explicitly preserves:
//   - spec.versions[].name and served/storage/deprecated flags
//   - spec.versions[].additionalPrinterColumns — drives column hints
//   - spec.group, spec.names, spec.scope, status.*
func DropUnstructuredManagedFields(obj any) (any, error) {
	u, ok := obj.(*unstructured.Unstructured)
	if !ok {
		// Dynamic informer should never hand us anything else, but be
		// defensive — return the object unchanged rather than erroring,
		// because a transform error is fatal for the informer.
		return obj, nil
	}

	unstructured.RemoveNestedField(u.Object, "metadata", "managedFields")
	unstructured.RemoveNestedField(u.Object, "metadata", "annotations", lastAppliedAnnotation)

	if u.GetKind() == "CustomResourceDefinition" {
		// Strip .schema from each version entry. Preserve everything
		// else (name, served, storage, deprecated, additionalPrinterColumns).
		if versions, found, _ := unstructured.NestedSlice(u.Object, "spec", "versions"); found {
			for i, v := range versions {
				vm, ok := v.(map[string]any)
				if !ok {
					continue
				}
				delete(vm, "schema")
				versions[i] = vm
			}
			// SetNestedSlice can only fail on non-serializable types; slices
			// of map[string]any are always fine. Ignoring the error is safe.
			_ = unstructured.SetNestedSlice(u.Object, versions, "spec", "versions")
		}

		// spec.conversion holds the webhook clientConfig (caBundle + URL)
		// for conversion webhooks. Not rendered by Radar.
		unstructured.RemoveNestedField(u.Object, "spec", "conversion")
	}

	return u, nil
}

// StripUnstructuredFields removes managedFields and heavy internal annotations
// from a deep copy of an unstructured object, so outward readers never leak a
// full desired manifest through last-applied. The informer transform already
// drops it from cached objects; GitOps drift reads it through
// GetDirectPreserveLastApplied instead.
func StripUnstructuredFields(u *unstructured.Unstructured) *unstructured.Unstructured {
	return stripUnstructuredFields(u, false)
}

// StripUnstructuredFieldsPreserveLastApplied removes managedFields from a deep
// copy while preserving kubectl last-applied. Use only for internal drift
// computation paths; API/UI/MCP payloads should call StripUnstructuredFields.
func StripUnstructuredFieldsPreserveLastApplied(u *unstructured.Unstructured) *unstructured.Unstructured {
	return stripUnstructuredFields(u, true)
}

func stripUnstructuredFields(u *unstructured.Unstructured, preserveLastApplied bool) *unstructured.Unstructured {
	if u == nil {
		return nil
	}

	cp := u.DeepCopy()
	unstructured.RemoveNestedField(cp.Object, "metadata", "managedFields")
	if !preserveLastApplied {
		if annotations := cp.GetAnnotations(); annotations != nil {
			delete(annotations, lastAppliedAnnotation)
			if len(annotations) == 0 {
				cp.SetAnnotations(nil)
			} else {
				cp.SetAnnotations(annotations)
			}
		}
	}
	return cp
}