//go:build !standard

package controllers

import (
	"bytes"
	"compress/gzip"
	"context"
	"crypto/sha256"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"strings"
	"time"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/equality"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/client-go/util/workqueue"
	"k8s.io/utils/clock"
	"pkg.package-operator.run/boxcutter"
	"pkg.package-operator.run/boxcutter/machinery"
	machinerytypes "pkg.package-operator.run/boxcutter/machinery/types"
	"pkg.package-operator.run/boxcutter/ownerhandling"
	"pkg.package-operator.run/boxcutter/probing"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/builder"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/controller"
	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
	"sigs.k8s.io/controller-runtime/pkg/handler"
	"sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/predicate"
	"sigs.k8s.io/controller-runtime/pkg/source"

	ocv1 "github.com/operator-framework/operator-controller/api/v1"
	"github.com/operator-framework/operator-controller/internal/object-controller/status"
	"github.com/operator-framework/operator-controller/internal/shared/labels"
)

const (
	clusterObjectSetTeardownFinalizer = "olm.operatorframework.io/teardown"

	// validationRetryInterval is how often the reconciler re-checks a revision that is
	// Ready=False/PreconditionsNotMet. These failures stem from inputs that are not watched
	// — a mutable or changed referenced Secret, an invalid referenced manifest, or a
	// preflight dry-run rejected until RBAC or a dependency CRD propagates — and the ref
	// spec is immutable, so a periodic retry lets the revision recover (once the Secret is
	// replaced or the cluster state catches up) without a controller restart.
	validationRetryInterval = 10 * time.Second
)

// ClusterObjectSetReconciler manages the Kubernetes objects in a ClusterObjectSet.
type ClusterObjectSetReconciler struct {
	Client                client.Client
	RevisionEngineFactory RevisionEngineFactory
	TrackingCache         trackingCache
	Clock                 clock.Clock
}

//go:generate mockgen -source clusterobjectset_controller.go -destination mock_trackingcache_gen_test.go -package controllers -mock_names trackingCache=MockTrackingCache -exclude_interfaces Sourcoser
type trackingCache interface {
	client.Reader
	Source(handler handler.EventHandler, predicates ...predicate.Predicate) source.Source
	Watch(ctx context.Context, user client.Object, gvks sets.Set[schema.GroupVersionKind]) error
	Free(ctx context.Context, user client.Object) error
}

//+kubebuilder:rbac:groups=olm.operatorframework.io,resources=clusterobjectsets,verbs=get;list;watch;update;patch;create;delete
//+kubebuilder:rbac:groups=olm.operatorframework.io,resources=clusterobjectsets/status,verbs=update;patch
//+kubebuilder:rbac:groups=olm.operatorframework.io,resources=clusterobjectsets/finalizers,verbs=update
//+kubebuilder:rbac:groups="",resources=secrets,verbs=get;list;watch

func (c *ClusterObjectSetReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	l := log.FromContext(ctx).WithName("cluster-extension-revision")
	ctx = log.IntoContext(ctx, l)

	if c.Clock == nil {
		c.Clock = clock.RealClock{}
	}

	existingRev := &ocv1.ClusterObjectSet{}
	if err := c.Client.Get(ctx, req.NamespacedName, existingRev); err != nil {
		return ctrl.Result{}, client.IgnoreNotFound(err)
	}

	l.Info("reconcile starting")
	defer l.Info("reconcile ending")

	reconciledRev := existingRev.DeepCopy()
	res, reconcileErr := c.reconcile(ctx, reconciledRev)

	// Ensure an active revision always reports a Ready condition. If reconcile left it
	// absent — e.g. an early transient error returned before the first evaluation set a
	// concrete state — initialize it to Unknown/Pending. This runs after reconcile (past
	// any in-reconcile metadata patches that refresh the object), only sets Ready when
	// absent so it never overwrites a previously observed state, and is skipped for
	// revisions that are being deleted or archived.
	if reconciledRev.DeletionTimestamp.IsZero() &&
		reconciledRev.Spec.LifecycleState != ocv1.ClusterObjectSetLifecycleStateArchived &&
		meta.FindStatusCondition(reconciledRev.Status.Conditions, ocv1.ClusterObjectSetTypeReady) == nil {
		markAsPending(reconciledRev)
	}

	// Do checks before any Update()s, as Update() may modify the resource structure!
	updateStatus := !equality.Semantic.DeepEqual(existingRev.Status, reconciledRev.Status)

	unexpectedFieldsChanged := checkForUnexpectedClusterObjectSetFieldChange(*existingRev, *reconciledRev)
	if unexpectedFieldsChanged {
		panic("spec or metadata changed by reconciler")
	}

	// NOTE: finalizer updates are performed during c.reconcile as patches, so that reconcile can
	//   continue performing logic after successfully setting the finalizer. therefore we only need
	//   to set status here.

	if updateStatus {
		if err := c.Client.Status().Update(ctx, reconciledRev); err != nil {
			reconcileErr = errors.Join(reconcileErr, fmt.Errorf("error updating status: %v", err))
		}
	}

	return res, reconcileErr
}

// Compare resources - ignoring status & metadata.finalizers
func checkForUnexpectedClusterObjectSetFieldChange(a, b ocv1.ClusterObjectSet) bool {
	a.Status, b.Status = ocv1.ClusterObjectSetStatus{}, ocv1.ClusterObjectSetStatus{}

	// when finalizers are updated during reconcile, we expect finalizers, managedFields, and resourceVersion
	// to be updated, so we ignore changes in these fields.
	a.Finalizers, b.Finalizers = []string{}, []string{}
	a.ManagedFields, b.ManagedFields = nil, nil
	a.ResourceVersion, b.ResourceVersion = "", ""
	return !equality.Semantic.DeepEqual(a.Spec, b.Spec)
}

func (c *ClusterObjectSetReconciler) reconcile(ctx context.Context, cos *ocv1.ClusterObjectSet) (ctrl.Result, error) {
	l := log.FromContext(ctx)

	if !cos.DeletionTimestamp.IsZero() {
		return c.delete(ctx, cos)
	}

	remaining, hasDeadline := durationUntilDeadline(c.Clock, cos)
	isDeadlineExceeded := hasDeadline && remaining <= 0

	if err := c.verifyReferencedSecretsImmutable(ctx, cos); err != nil {
		var mutErr *mutableSecretError
		if errors.As(err, &mutErr) {
			// A confirmed mutable Secret requires user action (replacing the immutable Secret),
			// which is not watched, so keep retrying so the revision can recover.
			// PreconditionsNotMet takes precedence over ProgressDeadlineExceeded: it is more actionable.
			l.Error(err, "referenced Secret is mutable, marking revision not ready")
			markAsNotReady(cos, ocv1.ClusterObjectSetReasonPreconditionsNotMet, err.Error())
			return ctrl.Result{RequeueAfter: validationRetryInterval}, nil
		}
		// A Secret read error is transient; leave the Ready condition unchanged and
		// return the error for rate-limited backoff.
		return ctrl.Result{}, fmt.Errorf("verifying referenced Secrets: %v", err)
	}

	phases, currentPhases, opts, err := c.buildBoxcutterPhases(ctx, cos)
	if err != nil {
		var contentErr *referencedContentError
		if errors.As(err, &contentErr) {
			// Invalid referenced Secret content (missing key or malformed manifest). The Secret
			// is not watched and the ref is immutable, so keep retrying so the revision can
			// recover once the Secret is replaced with valid content.
			l.Error(err, "invalid referenced content, marking revision not ready")
			markAsNotReady(cos, ocv1.ClusterObjectSetReasonPreconditionsNotMet, fmt.Sprintf("Referenced content is invalid: %v. Fix the Secret content.", err))
			return ctrl.Result{RequeueAfter: validationRetryInterval}, nil
		}
		var cfgErr *configValidationError
		if errors.As(err, &cfgErr) {
			// Invalid revision spec; a spec edit (or a new revision) re-triggers reconciliation,
			// so no periodic retry is needed.
			l.Error(err, "invalid configuration, marking revision not ready")
			markAsNotReady(cos, ocv1.ClusterObjectSetReasonInvalidSpecification, fmt.Sprintf("The object set spec is invalid: %v.", err))
			return ctrl.Result{}, nil
		}
		// Invariant: the error sites in buildBoxcutterPhases classify every deterministic
		// (spec/content) failure as a *configValidationError or *referencedContentError,
		// handled above. Anything reaching here is therefore a transient infrastructure
		// error (e.g. listing sibling revisions or reading a referenced Secret failed), so
		// leave Ready unchanged and return the error for a rate-limited backoff requeue.
		// New deterministic failure modes added to buildBoxcutterPhases must be wrapped in
		// one of those typed errors so they are reported rather than retried forever.
		return ctrl.Result{}, fmt.Errorf("converting to boxcutter revision: %v", err)
	}

	if len(cos.Status.ObservedPhases) == 0 {
		cos.Status.ObservedPhases = currentPhases
	} else if err := verifyObservedPhases(cos.Status.ObservedPhases, currentPhases); err != nil {
		// The resolved content of a referenced Secret changed since first reconciliation.
		// Secrets are not watched, so keep retrying so the revision can recover once the
		// original content is restored.
		l.Error(err, "resolved phases content changed, marking revision not ready")
		markAsNotReady(cos, ocv1.ClusterObjectSetReasonPreconditionsNotMet, fmt.Sprintf("Referenced Secret content no longer matches the original rollout: %v. Restore the original content.", err))
		return ctrl.Result{RequeueAfter: validationRetryInterval}, nil
	}

	revisionEngine, err := c.RevisionEngineFactory.CreateRevisionEngine(ctx, cos)
	if err != nil {
		return ctrl.Result{}, fmt.Errorf("failed to create revision engine: %v", err)
	}

	revision := boxcutter.NewRevisionWithOwner(
		cos.Name,
		cos.Spec.Revision,
		phases,
		cos,
		ownerhandling.NewNative(c.Client.Scheme()),
	)

	if cos.Spec.LifecycleState == ocv1.ClusterObjectSetLifecycleStateArchived {
		if err := c.TrackingCache.Free(ctx, cos); err != nil {
			return ctrl.Result{}, fmt.Errorf("error stopping informers: %v", err)
		}
		return c.archive(ctx, revisionEngine, cos, revision)
	}

	if err := c.ensureFinalizer(ctx, cos, clusterObjectSetTeardownFinalizer); err != nil {
		return ctrl.Result{}, fmt.Errorf("error ensuring teardown finalizer: %v", err)
	}

	if err := c.establishWatch(ctx, cos, revision); err != nil {
		return ctrl.Result{}, fmt.Errorf("establish watch: %v", err)
	}

	rres, err := revisionEngine.Reconcile(ctx, revision, opts...)
	if err != nil {
		if rres != nil {
			// Log detailed reconcile reports only in debug mode (V(1)) to reduce verbosity.
			l.V(1).Info("reconcile report", "report", rres.String())
		}
		return ctrl.Result{}, fmt.Errorf("revision reconcile: %v", err)
	}

	// Set object counts
	status.FromReconcile(cos, rres)

	// Report revision-level preflight validation failures and re-check on a flat timer:
	// the dry-run can be rejected for reasons that clear without a spec change (e.g. RBAC
	// or a dependency CRD still propagating), and those inputs are not watched.
	if verr := rres.GetValidationError(); verr != nil {
		l.Error(fmt.Errorf("%w", verr), "preflight validation failed, retrying after 10s")
		markAsNotReady(cos, ocv1.ClusterObjectSetReasonPreconditionsNotMet, fmt.Sprintf("A pre-apply check rejected the revision: %v.", verr))
		return ctrl.Result{RequeueAfter: validationRetryInterval}, nil
	}

	// Phases are reconciled in order; once a phase is incomplete, later phases are
	// only observed read-only (paused). A paused phase's preflight dry-run can fail
	// for reasons that resolve once earlier phases roll out (e.g. a Namespace a
	// later phase depends on has not been created yet), so its validation error is
	// not actionable yet. Only treat a phase's validation error as a terminal
	// validation failure while every preceding phase is complete; otherwise skip it
	// and let the rollout status (and the progress deadline) below take over.
	// Collisions are still reported for paused phases below: an object owned by
	// another controller does not become ownable just because earlier phases roll
	// out, so it remains actionable regardless of phase ordering.
	precedingPhasesComplete := true
	for _, pres := range rres.GetPhases() {
		if verr := pres.GetValidationError(); verr != nil {
			if !precedingPhasesComplete {
				// Paused downstream phase: an earlier phase is still rolling out.
				l.V(1).Info("ignoring paused phase preflight validation error while an earlier phase rolls out", "phase", pres.GetName(), "err", verr.Error())
				continue
			}
			l.Error(fmt.Errorf("%w", verr), "phase preflight validation failed, retrying after 10s", "phase", pres.GetName())
			markAsNotReady(cos, ocv1.ClusterObjectSetReasonPreconditionsNotMet, fmt.Sprintf("A pre-apply check rejected phase %q: %v.", pres.GetName(), verr))
			return ctrl.Result{RequeueAfter: validationRetryInterval}, nil
		}

		if !pres.IsComplete() {
			precedingPhasesComplete = false
		}

		var collidingObjs []string
		for _, ores := range pres.GetObjects() {
			if ores.Action() != machinery.ActionCollision {
				continue
			}
			obj := ores.Object()
			name := obj.GetName()
			if ns := obj.GetNamespace(); ns != "" {
				name = ns + "/" + name
			}
			gvk := obj.GetObjectKind().GroupVersionKind()
			desc := fmt.Sprintf("%s.%s %q", gvk.Kind, gvk.GroupVersion().String(), name)
			if coll, ok := ores.(machinery.ObjectResultCollision); ok {
				if owner, hasOwner := coll.ConflictingOwner(); hasOwner {
					desc += fmt.Sprintf(" is owned by %s %q", owner.Kind, owner.Name)
				}
			}
			collidingObjs = append(collidingObjs, desc)
		}

		if len(collidingObjs) > 0 {
			l.Error(fmt.Errorf("object collision detected"), "object collision, retrying after 10s", "phase", pres.GetName(), "collisions", collidingObjs)
			setReadyWithDeadline(cos, metav1.ConditionFalse, ocv1.ClusterObjectSetReasonObjectCollision,
				fmt.Sprintf("Cannot take ownership of %d object(s) in phase %q because they are owned by another controller or already exist. Remove the conflicting owner or object, or create a new ClusterObjectSet with a more permissive collisionProtection setting.", len(collidingObjs), pres.GetName()),
				isDeadlineExceeded)
			return ctrl.Result{RequeueAfter: 10 * time.Second}, nil
		}
	}

	// A revision whose objects have all been adopted by a newer sibling revision can
	// report IsComplete() (progressed objects count as complete), but it is superseded,
	// not successfully rolled out: skip the completion branch so it does not archive
	// previous revisions, report AllObjectsReady, or record a first completion
	// (completedAt) that would identify it as the installed revision.
	superseded := hasSupersededObject(rres)

	//nolint:nestif
	if rres.IsComplete() && !superseded {
		// Archive previous revisions
		previous, err := c.listPreviousRevisions(ctx, cos)
		if err != nil {
			return ctrl.Result{}, fmt.Errorf("listing previous revisions: %v", err)
		}
		for _, a := range previous {
			patch := []byte(`{"spec":{"lifecycleState":"Archived"}}`)
			if err := c.Client.Patch(ctx, client.Object(a), client.RawPatch(types.MergePatchType, patch)); err != nil {
				// TODO: It feels like an error here needs to propagate to a status _somewhere_.
				//   Not sure the current COS makes sense? But it also feels off to set the CE
				//   status from outside the CE reconciler.
				return ctrl.Result{}, fmt.Errorf("archive previous Revision: %w", err)
			}
		}

		markAsReady(cos, ocv1.ClusterObjectSetReasonAllObjectsReady, "All objects are at the desired state")

		// Record the timestamp of the first time the revision was observed to be
		// ready. This is set once and never changes for subsequent reconciliations.
		// It also serves as the signal that the revision has completed its rollout,
		// which the ClusterExtension controller uses to determine the installed revision.
		if cos.Status.CompletedAt.IsZero() {
			cos.Status.CompletedAt = metav1.NewTime(c.Clock.Now())
		}
	} else {
		var notReadyMsgs []string
		for _, pres := range rres.GetPhases() {
			if pres.IsComplete() {
				continue
			}
			for _, ores := range pres.GetObjects() {
				if ores.IsPaused() && ores.Action() == machinery.ActionCreated {
					// Skip probe checks of objects not yet created
					continue
				}
				// we probably want an AvailabilityProbeType and run through all of them independently of whether
				// the revision is complete or not
				pr := ores.ProbeResults()[boxcutter.ProgressProbeType]
				if pr.Status == machinerytypes.ProbeStatusTrue {
					continue
				}
				obj := ores.Object()
				gvk := obj.GetObjectKind().GroupVersionKind()
				// Count every not-ready object (the condition reports the count); the
				// per-object detail here is for the V(1) debug log, not the message.
				notReadyMsgs = append(notReadyMsgs, fmt.Sprintf(
					"Object %s.%s %s/%s: %v",
					gvk.Kind, gvk.GroupVersion().String(),
					obj.GetNamespace(), obj.GetName(), strings.Join(pr.Messages, " and "),
				))
			}
		}

		// Generic summary used as the ProgressDeadlineExceeded "last status", kept
		// stable (not the volatile per-object detail) so the deadline message does not
		// churn. The non-deadline path reports the count. Per-object detail is kept out
		// of the condition message and logged at V(1) for debugging.
		const genericNotReadyMsg = "Objects are not yet ready."
		if len(notReadyMsgs) > 0 {
			l.V(1).Info("objects not yet ready", "count", len(notReadyMsgs), "details", notReadyMsgs)
		}
		// Precedence: ProgressDeadlineExceeded > Superseded > ObjectsNotReady.
		switch {
		case isDeadlineExceeded:
			setReadyWithDeadline(cos, metav1.ConditionFalse, ocv1.ClusterObjectSetReasonObjectsNotReady, genericNotReadyMsg, true)
		case superseded:
			markAsNotReady(cos, ocv1.ClusterObjectSetReasonSuperseded, "Object(s) have been adopted by a newer revision of the object set.")
		default:
			notReadyMsg := genericNotReadyMsg
			if len(notReadyMsgs) > 0 {
				notReadyMsg = fmt.Sprintf("%d object(s) are not yet ready.", len(notReadyMsgs))
			}
			setReadyWithDeadline(cos, metav1.ConditionFalse, ocv1.ClusterObjectSetReasonObjectsNotReady, notReadyMsg, false)
		}
		if hasDeadline && !isDeadlineExceeded {
			return ctrl.Result{RequeueAfter: remaining}, nil
		}
	}

	return ctrl.Result{}, nil
}

func (c *ClusterObjectSetReconciler) delete(ctx context.Context, cos *ocv1.ClusterObjectSet) (ctrl.Result, error) {
	if err := c.TrackingCache.Free(ctx, cos); err != nil {
		return ctrl.Result{}, fmt.Errorf("error stopping informers: %v", err)
	}
	if err := c.removeFinalizer(ctx, cos, clusterObjectSetTeardownFinalizer); err != nil {
		return ctrl.Result{}, fmt.Errorf("error removing teardown finalizer: %v", err)
	}
	return ctrl.Result{}, nil
}

func (c *ClusterObjectSetReconciler) archive(ctx context.Context, revisionEngine RevisionEngine, cos *ocv1.ClusterObjectSet, revision boxcutter.RevisionBuilder) (ctrl.Result, error) {
	tdres, err := revisionEngine.Teardown(ctx, revision, machinerytypes.WithObserveAfterIncomplete{})
	if err != nil {
		// Transient teardown error: leave the Ready condition unchanged and return
		// the error for rate-limited backoff.
		return ctrl.Result{}, fmt.Errorf("error archiving revision: %v", err)
	}
	// Set object counts
	status.FromTeardown(cos, tdres)
	if tdres != nil && !tdres.IsComplete() {
		markAsArchiving(cos)
		return ctrl.Result{RequeueAfter: 5 * time.Second}, nil
	}
	// Ensure conditions are set before removing the finalizer when archiving
	if markAsArchived(cos) {
		return ctrl.Result{}, nil
	}
	if err := c.removeFinalizer(ctx, cos, clusterObjectSetTeardownFinalizer); err != nil {
		return ctrl.Result{}, fmt.Errorf("error removing teardown finalizer: %v", err)
	}
	return ctrl.Result{}, nil
}

type Sourcoser interface {
	Source(handler handler.EventHandler, predicates ...predicate.Predicate) source.Source
}

func (c *ClusterObjectSetReconciler) SetupWithManager(mgr ctrl.Manager) error {
	c.Clock = clock.RealClock{}
	return ctrl.NewControllerManagedBy(mgr).
		WithOptions(controller.Options{
			RateLimiter: newDeadlineAwareRateLimiter(
				workqueue.DefaultTypedControllerRateLimiter[ctrl.Request](),
				mgr.GetClient(),
				c.Clock,
			),
		}).
		For(
			&ocv1.ClusterObjectSet{},
			builder.WithPredicates(
				predicate.ResourceVersionChangedPredicate{},
			),
		).
		WatchesRawSource(
			c.TrackingCache.Source(
				handler.EnqueueRequestForOwner(mgr.GetScheme(), mgr.GetRESTMapper(), &ocv1.ClusterObjectSet{}),
				predicate.ResourceVersionChangedPredicate{},
			),
		).
		Complete(c)
}

func (c *ClusterObjectSetReconciler) establishWatch(ctx context.Context, cos *ocv1.ClusterObjectSet, revision boxcutter.RevisionBuilder) error {
	gvks := sets.New[schema.GroupVersionKind]()
	for _, phase := range revision.GetPhases() {
		for _, obj := range phase.GetObjects() {
			gvks.Insert(obj.GetObjectKind().GroupVersionKind())
		}
	}

	return c.TrackingCache.Watch(ctx, cos, gvks)
}

func (c *ClusterObjectSetReconciler) ensureFinalizer(
	ctx context.Context, obj client.Object, finalizer string,
) error {
	if controllerutil.ContainsFinalizer(obj, finalizer) {
		return nil
	}

	controllerutil.AddFinalizer(obj, finalizer)
	patch := map[string]any{
		"metadata": map[string]any{
			"resourceVersion": obj.GetResourceVersion(),
			"finalizers":      obj.GetFinalizers(),
		},
	}
	patchJSON, err := json.Marshal(patch)
	if err != nil {
		return fmt.Errorf("marshalling patch to remove finalizer: %w", err)
	}
	if err := c.Client.Patch(ctx, obj, client.RawPatch(types.MergePatchType, patchJSON)); err != nil {
		return fmt.Errorf("adding finalizer: %w", err)
	}
	return nil
}

func (c *ClusterObjectSetReconciler) removeFinalizer(ctx context.Context, obj client.Object, finalizer string) error {
	if !controllerutil.ContainsFinalizer(obj, finalizer) {
		return nil
	}

	controllerutil.RemoveFinalizer(obj, finalizer)

	patch := map[string]any{
		"metadata": map[string]any{
			"resourceVersion": obj.GetResourceVersion(),
			"finalizers":      obj.GetFinalizers(),
		},
	}
	patchJSON, err := json.Marshal(patch)
	if err != nil {
		return fmt.Errorf("marshalling patch to remove finalizer: %w", err)
	}
	if err := c.Client.Patch(ctx, obj, client.RawPatch(types.MergePatchType, patchJSON)); err != nil {
		return fmt.Errorf("removing finalizer: %w", err)
	}
	return nil
}

// listSiblingRevisions returns all active revisions belonging to the same owner, excluding the current one.
// This includes both lower and higher revision numbers, enabling boxcutter to properly classify
// sibling owners and avoid reporting false collisions during revision handover.
func (c *ClusterObjectSetReconciler) listSiblingRevisions(ctx context.Context, cos *ocv1.ClusterObjectSet) ([]*ocv1.ClusterObjectSet, error) {
	return c.listOtherActiveRevisions(ctx, cos, func(*ocv1.ClusterObjectSet) bool { return true })
}

// listPreviousRevisions returns active revisions belonging to the same owner with lower revision numbers.
func (c *ClusterObjectSetReconciler) listPreviousRevisions(ctx context.Context, cos *ocv1.ClusterObjectSet) ([]*ocv1.ClusterObjectSet, error) {
	return c.listOtherActiveRevisions(ctx, cos, func(r *ocv1.ClusterObjectSet) bool {
		return r.Spec.Revision < cos.Spec.Revision
	})
}

func (c *ClusterObjectSetReconciler) listOtherActiveRevisions(
	ctx context.Context,
	cos *ocv1.ClusterObjectSet,
	predicate func(*ocv1.ClusterObjectSet) bool,
) ([]*ocv1.ClusterObjectSet, error) {
	ownerLabel, ok := cos.Labels[labels.OwnerNameKey]
	if !ok {
		return nil, nil
	}

	revList := &ocv1.ClusterObjectSetList{}
	if err := c.TrackingCache.List(ctx, revList, client.MatchingLabels{
		labels.OwnerNameKey: ownerLabel,
	}); err != nil {
		return nil, fmt.Errorf("listing revisions: %w", err)
	}

	result := make([]*ocv1.ClusterObjectSet, 0, len(revList.Items))
	for i := range revList.Items {
		r := &revList.Items[i]
		if r.Name == cos.Name {
			continue
		}
		if r.Spec.LifecycleState == ocv1.ClusterObjectSetLifecycleStateArchived ||
			!r.DeletionTimestamp.IsZero() {
			continue
		}
		if !predicate(r) {
			continue
		}
		result = append(result, r)
	}

	return result, nil
}

// configValidationError marks an error caused by invalid user-provided configuration in the
// revision spec (a malformed revision/phase object or a bad progression probe). The spec is
// either immutable or watched, so the reconciler reports it as Ready=False/InvalidSpecification
// without a periodic retry: a spec edit re-triggers reconciliation.
type configValidationError struct{ error }

// referencedContentError marks a validation failure caused by the content of a referenced
// Secret (a missing key or a malformed manifest). Referenced Secrets are not watched and the
// phase/ref spec is immutable, so the failure can only clear when the Secret is replaced.
// The reconciler reports it as Ready=False/PreconditionsNotMet but keeps retrying periodically
// so the revision can recover without a controller restart.
type referencedContentError struct{ error }

func (c *ClusterObjectSetReconciler) buildBoxcutterPhases(ctx context.Context, cos *ocv1.ClusterObjectSet) ([]boxcutter.Phase, []ocv1.ObservedPhase, []boxcutter.RevisionReconcileOption, error) {
	siblings, err := c.listSiblingRevisions(ctx, cos)
	if err != nil {
		return nil, nil, nil, fmt.Errorf("listing sibling revisions: %w", err)
	}

	siblingObjs := make([]client.Object, len(siblings))
	for i, rev := range siblings {
		siblingObjs[i] = rev
	}

	progressionProbes, err := buildProgressionProbes(cos.Spec.ProgressionProbes)
	if err != nil {
		return nil, nil, nil, err
	}

	opts := []boxcutter.RevisionReconcileOption{
		boxcutter.WithSiblingOwners(siblingObjs),
		boxcutter.WithProbe(boxcutter.ProgressProbeType, progressionProbes),
		boxcutter.WithAggregatePhaseReconcileErrors(),
		boxcutter.WithObserveAfterIncomplete{},
	}

	phases := make([]boxcutter.Phase, 0, len(cos.Spec.Phases))
	observedPhases := make([]ocv1.ObservedPhase, 0, len(cos.Spec.Phases))
	for _, specPhase := range cos.Spec.Phases {
		objs := make([]client.Object, 0, len(specPhase.Objects))
		for _, specObj := range specPhase.Objects {
			var obj *unstructured.Unstructured
			switch {
			case specObj.Object.Object != nil:
				obj = specObj.Object.DeepCopy()
			case specObj.Ref.Name != "":
				resolved, err := c.resolveObjectRef(ctx, specObj.Ref)
				if err != nil {
					return nil, nil, nil, fmt.Errorf("resolving ref in phase %q: %w", specPhase.Name, err)
				}
				obj = resolved
			default:
				return nil, nil, nil, &configValidationError{fmt.Errorf("an object in phase %q has neither an inline object nor a Secret reference", specPhase.Name)}
			}

			objs = append(objs, obj)
		}

		// Compute digest from the user-provided objects before controller mutations.
		digest, err := computePhaseDigest(specPhase.Name, objs)
		if err != nil {
			return nil, nil, nil, fmt.Errorf("computing phase digest: %w", err)
		}
		observedPhases = append(observedPhases, ocv1.ObservedPhase{Name: specPhase.Name, Digest: digest})

		// Apply controller mutations after digest computation.
		for i, obj := range objs {
			objLabels := obj.GetLabels()
			if objLabels == nil {
				objLabels = map[string]string{}
			}
			objLabels[labels.OwnerNameKey] = cos.Labels[labels.OwnerNameKey]
			obj.SetLabels(objLabels)

			switch cp := EffectiveCollisionProtection(cos.Spec.CollisionProtection, specPhase.CollisionProtection, specPhase.Objects[i].CollisionProtection); cp {
			case ocv1.CollisionProtectionIfNoController, ocv1.CollisionProtectionNone:
				opts = append(opts, boxcutter.WithObjectReconcileOptions(
					obj, boxcutter.WithCollisionProtection(cp)))
			}
		}

		phases = append(phases, boxcutter.NewPhase(specPhase.Name, objs))
	}
	return phases, observedPhases, opts, nil
}

// resolveObjectRef fetches the referenced Secret, reads the value at the specified key,
// auto-detects gzip compression, and deserializes into an unstructured.Unstructured.
func (c *ClusterObjectSetReconciler) resolveObjectRef(ctx context.Context, ref ocv1.ObjectSourceRef) (*unstructured.Unstructured, error) {
	secret := &corev1.Secret{}
	key := client.ObjectKey{Name: ref.Name, Namespace: ref.Namespace}
	if err := c.Client.Get(ctx, key, secret); err != nil {
		return nil, fmt.Errorf("getting Secret %s/%s: %w", ref.Namespace, ref.Name, err)
	}

	data, ok := secret.Data[ref.Key]
	if !ok {
		return nil, &referencedContentError{fmt.Errorf("key %q not found in Secret %s/%s", ref.Key, ref.Namespace, ref.Name)}
	}

	// Auto-detect gzip compression (magic bytes 0x1f 0x8b)
	if len(data) >= 2 && data[0] == 0x1f && data[1] == 0x8b {
		reader, err := gzip.NewReader(bytes.NewReader(data))
		if err != nil {
			return nil, &referencedContentError{fmt.Errorf("creating gzip reader for key %q in Secret %s/%s: %w", ref.Key, ref.Namespace, ref.Name, err)}
		}
		defer reader.Close()
		const maxDecompressedSize = 10 * 1024 * 1024 // 10 MiB
		limited := io.LimitReader(reader, maxDecompressedSize+1)
		decompressed, err := io.ReadAll(limited)
		if err != nil {
			return nil, &referencedContentError{fmt.Errorf("decompressing key %q in Secret %s/%s: %w", ref.Key, ref.Namespace, ref.Name, err)}
		}
		if len(decompressed) > maxDecompressedSize {
			return nil, &referencedContentError{fmt.Errorf("decompressed data for key %q in Secret %s/%s exceeds maximum size (%d bytes)", ref.Key, ref.Namespace, ref.Name, maxDecompressedSize)}
		}
		data = decompressed
	}

	obj := &unstructured.Unstructured{}
	if err := json.Unmarshal(data, &obj.Object); err != nil {
		return nil, &referencedContentError{fmt.Errorf("unmarshaling object from key %q in Secret %s/%s: %w", ref.Key, ref.Namespace, ref.Name, err)}
	}

	return obj, nil
}

// EffectiveCollisionProtection resolves the collision protection value using
// the inheritance hierarchy: object > phase > spec > default ("Prevent").
func EffectiveCollisionProtection(cp ...ocv1.CollisionProtection) ocv1.CollisionProtection {
	ecp := ocv1.CollisionProtectionPrevent
	for _, c := range cp {
		if c != "" {
			ecp = c
		}
	}
	return ecp
}

// buildProgressionProbes creates a set of boxcutter probes from the fields provided in the COS's spec.progressionProbes.
// Returns nil and an error if encountered while attempting to build the probes.
func buildProgressionProbes(progressionProbes []ocv1.ProgressionProbe) (probing.And, error) {
	userProbes := probing.And{}
	if len(progressionProbes) < 1 {
		return userProbes, nil
	}
	for _, progressionProbe := range progressionProbes {
		// Collect all user assertions into a single 'And'
		assertions := probing.And{}
		for _, probe := range progressionProbe.Assertions {
			switch probe.Type {
			// Switch based on the union discriminator
			case ocv1.ProbeTypeConditionEqual:
				conditionProbe := probing.ConditionProbe(probe.ConditionEqual)
				assertions = append(assertions, &conditionProbe)
			case ocv1.ProbeTypeFieldsEqual:
				fieldsEqualProbe := probing.FieldsEqualProbe(probe.FieldsEqual)
				assertions = append(assertions, &fieldsEqualProbe)
			case ocv1.ProbeTypeFieldValue:
				fieldValueProbe := probing.FieldValueProbe(probe.FieldValue)
				assertions = append(assertions, &fieldValueProbe)
			default:
				return nil, &configValidationError{fmt.Errorf("unknown progression probe assertion type %q", probe.Type)}
			}
		}

		// Create the selector probe based on user-requested type and provide the assertions
		var selectorProbe probing.Prober
		switch progressionProbe.Selector.Type {
		// Switch based on the union discriminator
		case ocv1.SelectorTypeGroupKind:
			selectorProbe = &probing.GroupKindSelector{
				GroupKind: schema.GroupKind(progressionProbe.Selector.GroupKind),
				Prober:    assertions,
			}
		case ocv1.SelectorTypeLabel:
			selector, err := metav1.LabelSelectorAsSelector(&progressionProbe.Selector.Label)
			if err != nil {
				return nil, &configValidationError{fmt.Errorf("a progression probe has an invalid label selector (%v): %w", progressionProbe.Selector.Label, err)}
			}
			selectorProbe = &probing.LabelSelector{
				Selector: selector,
				Prober:   assertions,
			}
		default:
			return nil, &configValidationError{fmt.Errorf("unknown progression probe selector type %q", progressionProbe.Selector.Type)}
		}
		userProbes = append(userProbes, &probing.ObservedGenerationProbe{
			Prober: selectorProbe,
		})
	}
	return userProbes, nil
}

// setReadyWithDeadline sets the Ready condition to the supplied status/reason/message,
// unless the progress deadline has been exceeded — in which case it reports
// Ready=False/ProgressDeadlineExceeded instead. This centralises the progress
// deadline enforcement for the Ready condition.
func setReadyWithDeadline(cos *ocv1.ClusterObjectSet, status metav1.ConditionStatus, reason, message string, isDeadlineExceeded bool) { // nolint:unparam
	if isDeadlineExceeded {
		markAsNotReady(cos, ocv1.ReasonProgressDeadlineExceeded,
			fmt.Sprintf("Revision has not rolled out for %d minute(s). Last status: %s", cos.Spec.ProgressDeadlineMinutes, message))
		return
	}
	meta.SetStatusCondition(&cos.Status.Conditions, metav1.Condition{
		Type:               ocv1.ClusterObjectSetTypeReady,
		Status:             status,
		Reason:             reason,
		Message:            message,
		ObservedGeneration: cos.Generation,
	})
}

func markAsReady(cos *ocv1.ClusterObjectSet, reason, message string) bool {
	return meta.SetStatusCondition(&cos.Status.Conditions, metav1.Condition{
		Type:               ocv1.ClusterObjectSetTypeReady,
		Status:             metav1.ConditionTrue,
		Reason:             reason,
		Message:            message,
		ObservedGeneration: cos.Generation,
	})
}

func markAsNotReady(cos *ocv1.ClusterObjectSet, reason, message string) bool {
	return meta.SetStatusCondition(&cos.Status.Conditions, metav1.Condition{
		Type:               ocv1.ClusterObjectSetTypeReady,
		Status:             metav1.ConditionFalse,
		Reason:             reason,
		Message:            message,
		ObservedGeneration: cos.Generation,
	})
}

// hasSupersededObject reports whether any object in the revision has been adopted
// by a newer sibling revision (machinery.ActionProgressed). boxcutter only emits
// ActionProgressed for a newer sibling (a foreign owner is a collision), so no
// revision comparison is needed here.
func hasSupersededObject(rres machinery.RevisionResult) bool {
	for _, pres := range rres.GetPhases() {
		for _, ores := range pres.GetObjects() {
			if ores.Action() == machinery.ActionProgressed {
				return true
			}
		}
	}
	return false
}

// markAsPending initializes Ready=Unknown/Pending. It is only used before the first
// evaluation (when Ready is absent), so a freshly created revision always reports an
// explicit Ready condition rather than an absent one.
func markAsPending(cos *ocv1.ClusterObjectSet) {
	meta.SetStatusCondition(&cos.Status.Conditions, metav1.Condition{
		Type:               ocv1.ClusterObjectSetTypeReady,
		Status:             metav1.ConditionUnknown,
		Reason:             ocv1.ClusterObjectSetReasonPending,
		Message:            "The revision has not yet been evaluated.",
		ObservedGeneration: cos.Generation,
	})
}

func markAsArchiving(cos *ocv1.ClusterObjectSet) {
	const msg = "The object set is being archived; removing owned objects."
	markAsNotReady(cos, ocv1.ClusterObjectSetReasonArchiving, msg)
}

func markAsArchived(cos *ocv1.ClusterObjectSet) bool {
	const msg = "revision is archived"
	return markAsNotReady(cos, ocv1.ClusterObjectSetReasonArchived, msg)
}

// computePhaseDigest computes a deterministic SHA-256 digest of a phase's
// resolved content (name + objects) before any controller mutations.
// JSON serialization of unstructured objects produces a canonical encoding
// with sorted map keys.
func computePhaseDigest(name string, objects []client.Object) (string, error) {
	phaseMap := map[string]any{
		"name":    name,
		"objects": objects,
	}
	data, err := json.Marshal(phaseMap)
	if err != nil {
		// A non-marshalable object is invalid spec content, not a transient error;
		// classify it so the reconciler reports InvalidSpecification instead of
		// retrying forever.
		return "", &configValidationError{fmt.Errorf("marshaling phase %q: %w", name, err)}
	}
	h := sha256.Sum256(data)
	return fmt.Sprintf("sha256:%x", h), nil
}

// verifyObservedPhases compares current per-phase digests against stored
// digests. Returns an error listing all mismatched phases.
func verifyObservedPhases(stored, current []ocv1.ObservedPhase) error {
	if len(stored) == 0 {
		return fmt.Errorf("stored observedPhases is unexpectedly empty")
	}
	if len(stored) != len(current) {
		return fmt.Errorf("number of phases has changed (expected %d phases, got %d)", len(stored), len(current))
	}
	storedMap := make(map[string]string, len(stored))
	for _, s := range stored {
		storedMap[s.Name] = s.Digest
	}
	var mismatches []string
	for _, c := range current {
		if prev, ok := storedMap[c.Name]; ok && prev != c.Digest {
			mismatches = append(mismatches, fmt.Sprintf("%q", c.Name))
		}
	}
	if len(mismatches) > 0 {
		return fmt.Errorf("resolved content of %d phase(s) has changed since first rollout: %s",
			len(mismatches), strings.Join(mismatches, ", "))
	}
	return nil
}

// mutableSecretError is returned by verifyReferencedSecretsImmutable when one or
// more referenced Secrets are confirmed to be mutable. It distinguishes a confirmed
// precondition failure (reported as PreconditionsNotMet and retried on a timer) from
// a transient Secret read error (surfaced as a plain error for backoff requeue).
type mutableSecretError struct {
	msg string
}

func (e *mutableSecretError) Error() string { return e.msg }

// verifyReferencedSecretsImmutable checks that all referenced Secrets
// have Immutable set to true. A confirmed mutable Secret is returned as a
// *mutableSecretError listing every misconfigured Secret; a failure to read a
// Secret is returned as a plain (retryable) error.
func (c *ClusterObjectSetReconciler) verifyReferencedSecretsImmutable(ctx context.Context, cos *ocv1.ClusterObjectSet) error {
	type secretRef struct {
		name      string
		namespace string
	}
	seen := make(map[secretRef]struct{})
	var refs []secretRef

	for _, phase := range cos.Spec.Phases {
		for _, obj := range phase.Objects {
			if obj.Ref.Name == "" {
				continue
			}
			sr := secretRef{name: obj.Ref.Name, namespace: obj.Ref.Namespace}
			if _, ok := seen[sr]; !ok {
				seen[sr] = struct{}{}
				refs = append(refs, sr)
			}
		}
	}

	var mutableSecrets []string
	var readErr error
	for _, ref := range refs {
		secret := &corev1.Secret{}
		key := client.ObjectKey{Name: ref.name, Namespace: ref.namespace}
		if err := c.Client.Get(ctx, key, secret); err != nil {
			if apierrors.IsNotFound(err) {
				// Secret not yet available — skip verification.
				// resolveObjectRef will handle the not-found with a retryable error.
				continue
			}
			// Remember the first read error but keep checking the remaining refs: a
			// confirmed mutable Secret is a more actionable failure and takes precedence
			// over a transient read error.
			if readErr == nil {
				readErr = fmt.Errorf("getting Secret %s/%s: %w", ref.namespace, ref.name, err)
			}
			continue
		}

		if secret.Immutable == nil || !*secret.Immutable {
			mutableSecrets = append(mutableSecrets, fmt.Sprintf("%s/%s", ref.namespace, ref.name))
		}
	}

	if len(mutableSecrets) > 0 {
		return &mutableSecretError{msg: fmt.Sprintf(
			"Referenced Secret(s) must be immutable but are not: %s. Recreate them with immutable set to true.",
			strings.Join(mutableSecrets, ", "))}
	}

	if readErr != nil {
		return readErr
	}

	return nil
}