package controller

import (
	"context"
	"errors"
	"fmt"
	"time"

	appsv1 "k8s.io/api/apps/v1"
	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"
	"k8s.io/apimachinery/pkg/runtime/schema"
	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"
)

// 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. It
// also doubles as the eventual-rotation-detection interval for the Zalando
// database path (§8 asks for a live Secret watch; this controller doesn't
// have one yet, so a rotated credential is noticed on the next resync
// rather than immediately — a known simplification, not a design decision).
const resyncInterval = 5 * time.Minute

// waitInterval is the requeue while waiting on an external condition to
// resolve (the Deployment not ready yet, a Zalando cluster not found yet) —
// shorter than resyncInterval, since these are expected to change sooner
// than "someone edited something out of band."
const waitInterval = 15 * time.Second

// finalizerName cleans up the credentials Secret(s) this controller
// generates in the operator's own namespace on delete — the Deployment and
// Service are owned (OwnerReference, DESIGN.md §7) and need no finalizer of
// their own.
const finalizerName = "terdut.ryuvia.com/terdutserver"

// serviceAccountName is the name the operator registers itself under
// server-side (DESIGN.md §6) — a fixed, repo-wide constant, not a spec
// field: it names the automation, not anything about this one TerdutServer.
const serviceAccountName = "terdut-operator"

// bootstrapUsername/bootstrapEmail found the one human-shaped user every
// fresh install needs (terdut-server's handleBootstrap requires both).
// Nobody signs in as this user afterward — its only purpose is minting the
// admin key the controller immediately trades for a real service-account
// key — so these are fixed, not spec fields.
const (
	bootstrapUsername = "terdut-operator-bootstrap"
	bootstrapEmail    = "bootstrap@terdut-operator.local"
)

// postgresqlGVK is the Zalando postgres-operator's CR (DESIGN.md §8).
// Resolved via unstructured rather than vendoring Zalando's own client, to
// keep this operator's dependency on it to "an optional CRD read" rather
// than a library — matches §9's "degrade gracefully if the CRD isn't
// installed" stance.
var postgresqlGVK = schema.GroupVersionKind{Group: "acid.zalan.do", Version: "v1", Kind: "postgresql"}

// TerdutServerReconciler reconciles a TerdutServer object.
//
// Stage 1 (ROADMAP.md): full lifecycle. The operator creates and owns every
// TerdutServer it manages (DESIGN.md §1) — there is no adopt path.
type TerdutServerReconciler struct {
	client.Client
	Scheme *runtime.Scheme

	// OperatorNamespace is where every credentials Secret this controller
	// generates 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.
	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;create;update;patch;delete
// +kubebuilder:rbac:groups="",resources=services,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=apps,resources=deployments,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=acid.zalan.do,resources=postgresqls,verbs=get;list;watch
// +kubebuilder:rbac:groups=events.k8s.io,resources=events,verbs=create;patch

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.DeletionTimestamp.IsZero() {
		return r.reconcileDelete(ctx, &srv)
	}

	if !controllerutil.ContainsFinalizer(&srv, finalizerName) {
		controllerutil.AddFinalizer(&srv, finalizerName)
		if err := r.Update(ctx, &srv); err != nil {
			return ctrl.Result{}, err
		}
		// The Update above re-triggers a reconcile via the watch; nothing
		// further to do on this pass.
		return ctrl.Result{}, nil
	}

	dbEnv, dbErr := r.resolveDatabaseEnv(ctx, &srv)
	if dbErr != nil {
		return r.setNotReady(ctx, &srv, dbErr.reason, dbErr.message, waitInterval)
	}

	deploy, err := r.reconcileDeployment(ctx, &srv, dbEnv)
	if err != nil {
		return ctrl.Result{}, err
	}
	if err := r.reconcileService(ctx, &srv); err != nil {
		return ctrl.Result{}, err
	}

	meta.SetStatusCondition(&srv.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionDatabaseReady,
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonAdopted,
		Message: "database resolved",
	})

	if deploy.Status.ReadyReplicas < 1 {
		return r.setNotReady(ctx, &srv,
			terdutv1alpha1.ReasonWaitingForDeployment,
			fmt.Sprintf("Deployment %q has no ready replica yet", deploy.Name),
			waitInterval)
	}

	if srv.Status.CredentialsSecretRef == nil {
		if err := r.reconcileBootstrap(ctx, &srv); err != nil {
			if pending, ok := errors.AsType[*bootstrapStateLostError](err); ok {
				return r.setNotReady(ctx, &srv, terdutv1alpha1.ReasonBootstrapStateLost, pending.Error(), waitInterval)
			}
			return ctrl.Result{}, err
		}
	}

	meta.SetStatusCondition(&srv.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionBootstrapped,
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonAdopted,
		Message: fmt.Sprintf("credentials in Secret %q", srv.Status.CredentialsSecretRef.Name),
	})
	meta.SetStatusCondition(&srv.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonAdopted,
		Message: "deployment ready, database resolved, credentials bootstrapped",
	})
	srv.Status.ServiceName = srv.Name
	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,
			"terdut-server ready")
	}
	log.Info("TerdutServer ready", "name", srv.Name)

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

// setNotReady records Ready: False with reason/message, fires a Warning
// event, and requeues after d. Every "waiting on something" 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, d time.Duration,
) (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: d}, nil
}

// reconcileDelete cleans up the credentials Secret(s) this controller
// generated in the operator's own namespace. The Deployment and Service are
// owned (OwnerReference, DESIGN.md §7) and need no attention here — normal
// GC handles them. There is no server-side "delete this install" call to
// make: bootstrap created a user and a service account, and terdut-server's
// API has no way to delete either (only to revoke individual keys), so
// there is nothing meaningful to undo there either.
func (r *TerdutServerReconciler) reconcileDelete(ctx context.Context, srv *terdutv1alpha1.TerdutServer) (ctrl.Result, error) {
	if !controllerutil.ContainsFinalizer(srv, finalizerName) {
		return ctrl.Result{}, nil
	}
	for _, name := range []string{checkpointSecretName(srv), credentialsSecretName(srv)} {
		sec := &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: name, Namespace: r.OperatorNamespace}}
		if err := r.Delete(ctx, sec); err != nil && !apierrors.IsNotFound(err) {
			return ctrl.Result{}, err
		}
	}
	controllerutil.RemoveFinalizer(srv, finalizerName)
	if err := r.Update(ctx, srv); err != nil {
		return ctrl.Result{}, err
	}
	return ctrl.Result{}, 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{}).
		Owns(&appsv1.Deployment{}).
		Owns(&corev1.Service{}).
		Named("terdutserver").
		Complete(r)
}

// --- naming ---

func checkpointSecretName(srv *terdutv1alpha1.TerdutServer) string {
	return fmt.Sprintf("%s.%s-bootstrap-admin", srv.Namespace, srv.Name)
}

func credentialsSecretName(srv *terdutv1alpha1.TerdutServer) string {
	return fmt.Sprintf("%s.%s-instance-credentials", srv.Namespace, srv.Name)
}

func serviceURL(srv *terdutv1alpha1.TerdutServer) string {
	port := srv.Spec.Networking.ServicePort
	if port == 0 {
		port = 8080
	}
	return fmt.Sprintf("http://%s.%s.svc:%d", srv.Name, srv.Namespace, port)
}