package controller

import (
	"context"
	"fmt"
	"strconv"
	"time"

	corev1 "k8s.io/api/core/v1"
	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/runtime"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/recorder"

	terdutv1alpha1 "git.ryuvia.com/niklas/terdut-operator/api/v1alpha1"
	"git.ryuvia.com/niklas/terdut-operator/internal/tdclient"
)

const alertSourceFinalizerName = "terdut.ryuvia.com/terdutalertsource"

// Data keys inside the generated webhook Secret (DESIGN.md §4.5). url/key
// are what a sender actually needs; integrationID exists purely so this
// Secret -- once written -- is also this CR's own record that a create
// already succeeded (see reconcileCreate's own comment for why that
// matters more here than for any other child kind).
const (
	webhookSecretURLKey           = "url"
	webhookSecretKeyDataKey       = "key"
	webhookSecretIntegrationIDKey = "integrationID"
)

// TerdutAlertSourceReconciler reconciles a TerdutAlertSource object.
type TerdutAlertSourceReconciler struct {
	client.Client
	Scheme *runtime.Scheme

	OperatorNamespace string
	Recorder          recorder.EventRecorder
	NewClient         func(endpoint string) *tdclient.Client
}

// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutalertsources,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutalertsources/status,verbs=get;update;patch
// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutalertsources/finalizers,verbs=update
// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutteams,verbs=get;list;watch
// +kubebuilder:rbac:groups="",resources=secrets,verbs=get;list;watch;create;update;patch
// +kubebuilder:rbac:groups=events.k8s.io,resources=events,verbs=create;patch

func (r *TerdutAlertSourceReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	log := logf.FromContext(ctx)

	var as terdutv1alpha1.TerdutAlertSource
	if err := r.Get(ctx, req.NamespacedName, &as); err != nil {
		if apierrors.IsNotFound(err) {
			return ctrl.Result{}, nil
		}
		return ctrl.Result{}, err
	}

	newClient := r.NewClient
	if newClient == nil {
		newClient = tdclient.New
	}

	if !as.DeletionTimestamp.IsZero() {
		return r.reconcileDelete(ctx, &as, newClient)
	}

	if !controllerutil.ContainsFinalizer(&as, alertSourceFinalizerName) {
		controllerutil.AddFinalizer(&as, alertSourceFinalizerName)
		if err := r.Update(ctx, &as); err != nil {
			return ctrl.Result{}, err
		}
		return ctrl.Result{}, nil
	}

	team, tc, resolveErr := resolveTeamAndClient(ctx, r.Client, r.OperatorNamespace, as.Namespace, as.Spec.TeamRef, newClient)
	if resolveErr != nil {
		return r.setNotReady(ctx, &as, resolveErr.reason, resolveErr.message, waitInterval)
	}
	teamID := team.Status.TeamID

	if as.Status.IntegrationID == 0 {
		if err := r.reconcileCreate(ctx, &as, tc, teamID); err != nil {
			return ctrl.Result{}, err
		}
	} else {
		secretName := webhookSecretName(&as)
		var secret corev1.Secret
		if err := r.Get(ctx, client.ObjectKey{Namespace: as.Namespace, Name: secretName}, &secret); err != nil {
			if !apierrors.IsNotFound(err) {
				return ctrl.Result{}, err
			}
			// Fail-closed, not self-healed (DESIGN.md §5): the key is
			// genuinely gone and can never be re-read from terdut-server,
			// so minting a replacement here would silently rotate a live
			// webhook URL with no spec change to explain why. Deleting
			// and recreating this CR is the supported recovery.
			return r.setNotReady(ctx, &as, terdutv1alpha1.ReasonWebhookSecretLost,
				fmt.Sprintf("webhook Secret %s/%s is gone; delete and recreate this TerdutAlertSource to rotate a new one", as.Namespace, secretName),
				waitInterval)
		}

		if as.Spec.Kind != as.Status.LastAppliedKind {
			if err := r.rotateKind(ctx, &as, tc, teamID); err != nil {
				return ctrl.Result{}, err
			}
		} else if err := tc.RenameIntegration(ctx, teamID, as.Status.IntegrationID, as.Spec.Name); err != nil {
			return ctrl.Result{}, fmt.Errorf("PATCH /api/teams/%d/integrations/%d: %w", teamID, as.Status.IntegrationID, err)
		}
	}

	meta.SetStatusCondition(&as.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonChildAdopted,
		Message: fmt.Sprintf("integration %d applied on team %d", as.Status.IntegrationID, teamID),
	})
	as.Status.ObservedGeneration = as.Generation
	if err := r.Status().Update(ctx, &as); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(&as, nil, corev1.EventTypeNormal, terdutv1alpha1.ReasonChildAdopted, terdutv1alpha1.ReasonChildAdopted,
			"alert source applied")
	}
	log.Info("TerdutAlertSource applied", "name", as.Name, "integrationID", as.Status.IntegrationID)

	return ctrl.Result{RequeueAfter: resyncInterval}, nil
}

// webhookSecretName is deterministic from this object's own, immutable
// metadata.name -- not spec.name, which can be renamed freely without the
// Secret needing to follow (DESIGN.md §4.5: renaming never rotates the key).
func webhookSecretName(as *terdutv1alpha1.TerdutAlertSource) string {
	return as.Name + "-terdut-webhook"
}

// reconcileCreate implements this resource's own idempotent-create shape --
// deliberately not list-and-match (TerdutDeadmanSwitch) or adopt-on-409
// (Team/service-account): terdut-server shows the webhook key exactly once,
// at creation, and never again (DESIGN.md §4.5), so there is no server-side
// lookup that could ever recover it. Instead, the webhook Secret itself --
// written immediately after a successful POST, before status is ever
// touched -- is this CR's only durable record that a create already
// succeeded. A crash between the POST and the Secret write is the one
// unrecoverable case: on the next reconcile the Secret still won't exist,
// so this mints a brand new integration rather than risk adopting an
// orphaned, keyless row by name -- same accepted tradeoff as the "orphaned
// first key some interrupted attempt minted and never used" footnote
// DESIGN.md §6 already documents for service-account keys.
func (r *TerdutAlertSourceReconciler) reconcileCreate(
	ctx context.Context, as *terdutv1alpha1.TerdutAlertSource, tc *tdclient.Client, teamID int64,
) error {
	secretName := webhookSecretName(as)

	var secret corev1.Secret
	err := r.Get(ctx, client.ObjectKey{Namespace: as.Namespace, Name: secretName}, &secret)
	switch {
	case err == nil:
		// Crash recovery: a previous reconcile got as far as writing the
		// Secret but died before writing status -- read the id back out
		// of it rather than calling the server again.
		id, parseErr := strconv.ParseInt(string(secret.Data[webhookSecretIntegrationIDKey]), 10, 64)
		if parseErr != nil {
			return fmt.Errorf("webhook Secret %s/%s has no valid %s: %w", as.Namespace, secretName, webhookSecretIntegrationIDKey, parseErr)
		}
		as.Status.IntegrationID = id
		as.Status.LastAppliedKind = as.Spec.Kind
		as.Status.WebhookURLSecretRef = &terdutv1alpha1.LocalSecretRef{Name: secretName}
		return nil
	case !apierrors.IsNotFound(err):
		return err
	}

	created, err := tc.CreateIntegration(ctx, teamID, as.Spec.Name, as.Spec.Kind)
	if err != nil {
		return fmt.Errorf("POST /api/teams/%d/integrations: %w", teamID, err)
	}
	if err := r.writeWebhookSecret(ctx, as, secretName, created); err != nil {
		return err
	}
	as.Status.IntegrationID = created.ID
	as.Status.LastAppliedKind = as.Spec.Kind
	as.Status.WebhookURLSecretRef = &terdutv1alpha1.LocalSecretRef{Name: secretName}
	return nil
}

// rotateKind deletes the currently-live integration and creates a fresh one
// under the new kind (DESIGN.md §5's reconciliation table: kind is the one
// spec field with no in-place update verb at all), firing a Warning event
// since this rotates the webhook key and breaks whatever still sends to the
// old URL.
func (r *TerdutAlertSourceReconciler) rotateKind(
	ctx context.Context, as *terdutv1alpha1.TerdutAlertSource, tc *tdclient.Client, teamID int64,
) error {
	oldKind, oldID := as.Status.LastAppliedKind, as.Status.IntegrationID
	if err := tc.DeleteIntegration(ctx, teamID, oldID); err != nil {
		return fmt.Errorf("DELETE /api/teams/%d/integrations/%d (rotating kind %q -> %q): %w",
			teamID, oldID, oldKind, as.Spec.Kind, err)
	}

	// reconcileCreate's own crash-recovery path trusts this Secret's mere
	// existence as "a create already succeeded" -- it must be gone before
	// calling it here, or rotation would misread the about-to-be-stale
	// old id right back out of it instead of minting a replacement.
	secretName := webhookSecretName(as)
	if err := r.Delete(ctx, &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: secretName, Namespace: as.Namespace}}); err != nil && !apierrors.IsNotFound(err) {
		return fmt.Errorf("deleting stale webhook Secret %s/%s: %w", as.Namespace, secretName, err)
	}

	as.Status.IntegrationID = 0
	as.Status.WebhookURLSecretRef = nil
	if err := r.reconcileCreate(ctx, as, tc, teamID); err != nil {
		return err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(as, nil, corev1.EventTypeWarning, terdutv1alpha1.ReasonKindRotated, terdutv1alpha1.ReasonKindRotated,
			"spec.kind changed from %q to %q: deleted integration %d and minted a new one (%d) -- the webhook URL/key changed, update whatever was sending to the old one",
			oldKind, as.Spec.Kind, oldID, as.Status.IntegrationID)
	}
	return nil
}

// writeWebhookSecret creates or replaces the generated Secret holding
// integ's key material, owned by as (plain OwnerReference, same namespace,
// per DESIGN.md §7 -- no finalizer needed for this one, unlike the
// cross-namespace credential Secrets elsewhere in this operator).
func (r *TerdutAlertSourceReconciler) writeWebhookSecret(
	ctx context.Context, as *terdutv1alpha1.TerdutAlertSource, name string, integ *tdclient.Integration,
) error {
	secret := &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: name, Namespace: as.Namespace}}
	_, err := controllerutil.CreateOrUpdate(ctx, r.Client, secret, func() error {
		secret.Data = map[string][]byte{
			webhookSecretURLKey:           []byte(integ.URL),
			webhookSecretKeyDataKey:       []byte(integ.Key),
			webhookSecretIntegrationIDKey: []byte(strconv.FormatInt(integ.ID, 10)),
		}
		return controllerutil.SetControllerReference(as, secret, r.Scheme)
	})
	return err
}

func (r *TerdutAlertSourceReconciler) setNotReady(
	ctx context.Context, as *terdutv1alpha1.TerdutAlertSource, reason, message string, d time.Duration,
) (ctrl.Result, error) {
	meta.SetStatusCondition(&as.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionFalse,
		Reason:  reason,
		Message: message,
	})
	as.Status.ObservedGeneration = as.Generation
	if err := r.Status().Update(ctx, as); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(as, nil, corev1.EventTypeWarning, reason, reason, message)
	}
	return ctrl.Result{RequeueAfter: d}, nil
}

// reconcileDelete calls the real DELETE this resource has (unlike
// TerdutEscalationRule) if the team is still resolvable and an integration
// was ever created, then removes the finalizer unconditionally. The
// webhook Secret needs no explicit cleanup here -- it's same-namespace and
// OwnerReference-GC'd (DESIGN.md §7), not this finalizer's job.
func (r *TerdutAlertSourceReconciler) reconcileDelete(
	ctx context.Context, as *terdutv1alpha1.TerdutAlertSource, newClient func(string) *tdclient.Client,
) (ctrl.Result, error) {
	if !controllerutil.ContainsFinalizer(as, alertSourceFinalizerName) {
		return ctrl.Result{}, nil
	}

	if as.Status.IntegrationID != 0 {
		if team, tc, resolveErr := resolveTeamAndClient(
			ctx, r.Client, r.OperatorNamespace, as.Namespace, as.Spec.TeamRef, newClient,
		); resolveErr == nil {
			if err := tc.DeleteIntegration(ctx, team.Status.TeamID, as.Status.IntegrationID); err != nil {
				if r.Recorder != nil {
					r.Recorder.Eventf(as, nil, corev1.EventTypeWarning, "DeleteFailed", "DeleteFailed", err.Error())
				}
				return ctrl.Result{}, err
			}
		}
	}

	controllerutil.RemoveFinalizer(as, alertSourceFinalizerName)
	return ctrl.Result{}, r.Update(ctx, as)
}

// SetupWithManager sets up the controller with the Manager.
func (r *TerdutAlertSourceReconciler) SetupWithManager(mgr ctrl.Manager) error {
	if r.NewClient == nil {
		r.NewClient = tdclient.New
	}
	if r.Recorder == nil {
		r.Recorder = mgr.GetEventRecorder("terdutalertsource-controller")
	}
	return ctrl.NewControllerManagedBy(mgr).
		For(&terdutv1alpha1.TerdutAlertSource{}).
		// Watched, not just the CR (DESIGN.md §5): the webhook Secret's
		// loss has to be noticed on its own, independent of any spec
		// change to this CR, for ReasonWebhookSecretLost to ever fire.
		Owns(&corev1.Secret{}).
		Named("terdutalertsource").
		Complete(r)
}