package controller

import (
	"context"
	"fmt"
	"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"
	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"
)

// resyncInterval is the periodic requeue on a successful reconcile (DESIGN.md
// §5's general rule) — it exists to catch drift from someone changing state
// directly against the server's API/UI, not from a missed watch event.
const resyncInterval = 5 * time.Minute

// waitInterval is the requeue while waiting on an external condition to
// resolve (the credential Secret not existing yet, the server being
// unreachable) — shorter than resyncInterval, since these are expected to
// change sooner than "someone edited something out of band."
const waitInterval = 30 * time.Second

// TerdutServerReconciler reconciles a TerdutServer object.
//
// Stage 1 (ROADMAP.md): bootstrap/credentials only, bring-your-own path
// only. It never creates, updates, or deletes anything server-side or any
// Deployment/Service — it only reads a Secret the operator's own namespace
// already has and probes the server's /api/version. No finalizer: this
// controller owns nothing that needs cleaning up on delete (it never creates
// the credentials Secret itself, only ever adopts one a human already
// made) — revisit once self-registration (Stage 5) generates its own.
type TerdutServerReconciler struct {
	client.Client
	Scheme *runtime.Scheme

	// OperatorNamespace is where every credentials Secret this controller
	// reads or writes lives (DESIGN.md §6) — never the TerdutServer's own
	// namespace. Set from the POD_NAMESPACE downward-API env var in
	// production (cmd/main.go); tests set it directly.
	OperatorNamespace string

	// Recorder emits the Kubernetes Events DESIGN.md §12 asks for on every
	// externally-visible outcome. The events.k8s.io/v1 API, not the
	// deprecated core/v1 one GetEventRecorderFor still returns.
	Recorder recorder.EventRecorder

	// NewClient builds the terdut-server API client for a given endpoint.
	// A field, not a direct tdclient.New call, so tests can substitute an
	// httptest.Server's client without a real network round trip. Defaults
	// to tdclient.New via SetupWithManager.
	NewClient func(endpoint string) *tdclient.Client
}

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

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

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

	if srv.Spec.CredentialsSecretRef == nil {
		return r.setNotReady(ctx, &srv,
			terdutv1alpha1.ReasonCredentialsSecretRefRequired,
			"spec.credentialsSecretRef is unset; self-registration bootstrap isn't "+
				"implemented yet (Stage 5) — mint an instance-scoped service account "+
				"with your own admin session (POST /api/service-accounts) and set "+
				"this field to a Secret holding its key (DESIGN.md §6)")
	}
	ref := srv.Spec.CredentialsSecretRef

	var secret corev1.Secret
	secretKey := client.ObjectKey{Namespace: r.OperatorNamespace, Name: ref.Name}
	if err := r.Get(ctx, secretKey, &secret); err != nil {
		if apierrors.IsNotFound(err) {
			return r.setNotReady(ctx, &srv,
				terdutv1alpha1.ReasonCredentialsSecretNotFound,
				fmt.Sprintf("Secret %q not found in namespace %q", ref.Name, r.OperatorNamespace))
		}
		return ctrl.Result{}, err
	}

	raw, ok := secret.Data[ref.Key]
	if !ok || len(raw) == 0 {
		return r.setNotReady(ctx, &srv,
			terdutv1alpha1.ReasonCredentialsSecretInvalid,
			fmt.Sprintf("Secret %q has no data under key %q", ref.Name, ref.Key))
	}

	newClient := r.NewClient
	if newClient == nil {
		newClient = tdclient.New
	}
	if _, err := newClient(srv.Spec.Endpoint).Version(ctx); err != nil {
		return r.setNotReady(ctx, &srv,
			terdutv1alpha1.ReasonServerUnreachable,
			fmt.Sprintf("GET %s/api/version: %v", srv.Spec.Endpoint, err))
	}

	srv.Status.CredentialsSecretRef = ref.DeepCopy()
	meta.SetStatusCondition(&srv.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionBootstrapped,
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonAdopted,
		Message: fmt.Sprintf("adopted spec.credentialsSecretRef (Secret %q, key %q)", ref.Name, ref.Key),
	})
	meta.SetStatusCondition(&srv.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonAdopted,
		Message: "credentials adopted, server reachable",
	})
	srv.Status.ObservedGeneration = srv.Generation
	if err := r.Status().Update(ctx, &srv); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(&srv, nil, corev1.EventTypeNormal,
			terdutv1alpha1.ReasonAdopted, terdutv1alpha1.ReasonAdopted,
			"credentials adopted, server reachable")
	}
	log.Info("TerdutServer ready", "endpoint", srv.Spec.Endpoint)

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

// setNotReady records Ready: False with reason/message on both conditions,
// fires a Warning event, and requeues after waitInterval — every "waiting on
// something external" exit from Reconcile goes through here so the
// condition/event/requeue shape can't drift between them.
func (r *TerdutServerReconciler) setNotReady(
	ctx context.Context, srv *terdutv1alpha1.TerdutServer, reason, message string,
) (ctrl.Result, error) {
	meta.SetStatusCondition(&srv.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionFalse,
		Reason:  reason,
		Message: message,
	})
	srv.Status.ObservedGeneration = srv.Generation
	if err := r.Status().Update(ctx, srv); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(srv, nil, corev1.EventTypeWarning, reason, reason, message)
	}
	return ctrl.Result{RequeueAfter: waitInterval}, nil
}

// SetupWithManager sets up the controller with the Manager.
func (r *TerdutServerReconciler) SetupWithManager(mgr ctrl.Manager) error {
	if r.NewClient == nil {
		r.NewClient = tdclient.New
	}
	if r.Recorder == nil {
		r.Recorder = mgr.GetEventRecorder("terdutserver-controller")
	}
	return ctrl.NewControllerManagedBy(mgr).
		For(&terdutv1alpha1.TerdutServer{}).
		Named("terdutserver").
		Complete(r)
}