package controller

import (
	"context"
	"errors"
	"fmt"
	"net/http"

	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"
	"sigs.k8s.io/controller-runtime/pkg/handler"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/reconcile"
	"sigs.k8s.io/controller-runtime/pkg/recorder"

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

// teamFinalizerName deletes the team on the server before the CR goes.
const teamFinalizerName = "terdut.ryuvia.com/terdutteam"

// TerdutTeamReconciler reconciles a TerdutTeam: the team itself plus its
// escalation ladder and dead man's switches, all through the referenced
// TerdutServer's operator key.
type TerdutTeamReconciler struct {
	client.Client
	Scheme *runtime.Scheme

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

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

// teamExternalID is the identity this CR gives its team on the server, so the
// team is found by who owns it and not by its (editable, global) display name.
func teamExternalID(team *terdutv1alpha1.TerdutTeam) string {
	return team.Namespace + "/" + team.Name
}

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

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

	if !team.DeletionTimestamp.IsZero() {
		return r.reconcileTeamDelete(ctx, &team)
	}

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

	srv, resolveErr := r.resolveServerRef(ctx, &team)
	if resolveErr != nil {
		return r.setTeamNotReady(ctx, &team, resolveErr.reason, resolveErr.message)
	}
	if !meta.IsStatusConditionTrue(srv.Status.Conditions, terdutv1alpha1.ConditionReady) {
		return r.setTeamNotReady(ctx, &team, terdutv1alpha1.ReasonWaitingForServer,
			fmt.Sprintf("TerdutServer %q is not Ready yet", srv.Name))
	}

	tc, err := r.serverClient(ctx, srv)
	if err != nil {
		return ctrl.Result{}, err
	}

	// Idempotent on the external id: the same team comes back whether this is
	// the first reconcile, a retry after a lost status write, or a repair after
	// somebody deleted the team behind our back.
	created, err := tc.CreateTeam(ctx, team.Spec.DisplayName, teamExternalID(&team))
	if err != nil {
		if se, ok := errors.AsType[*tdclient.StatusError](err); ok && se.Code == http.StatusConflict {
			return r.setTeamNotReady(ctx, &team, terdutv1alpha1.ReasonTeamNameTaken, nameTakenMessage(&team))
		}
		return ctrl.Result{}, fmt.Errorf("POST /api/teams: %w", err)
	}
	team.Status.TeamID = created.ID

	if err := tc.RenameTeam(ctx, created.ID, team.Spec.DisplayName); err != nil {
		if se, ok := errors.AsType[*tdclient.StatusError](err); ok && se.Code == http.StatusConflict {
			return r.setTeamNotReady(ctx, &team, terdutv1alpha1.ReasonTeamNameTaken, nameTakenMessage(&team))
		}
		return ctrl.Result{}, fmt.Errorf("PUT /api/teams/%d: %w", created.ID, err)
	}
	if err := tc.SetTeamOIDCGroups(ctx, created.ID, team.Spec.OIDC.MemberGroup, team.Spec.OIDC.OwnerGroup); err != nil {
		return ctrl.Result{}, fmt.Errorf("PUT /api/teams/%d/oidc-groups: %w", created.ID, err)
	}

	if condErr, err := r.reconcileEscalation(ctx, tc, &team); err != nil {
		return ctrl.Result{}, err
	} else if condErr != nil {
		return r.setTeamNotReady(ctx, &team, condErr.reason, condErr.message)
	}
	if condErr, err := r.reconcileDeadmanSwitches(ctx, tc, &team); err != nil {
		return ctrl.Result{}, err
	} else if condErr != nil {
		return r.setTeamNotReady(ctx, &team, condErr.reason, condErr.message)
	}

	meta.SetStatusCondition(&team.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonTeamAdopted,
		Message: fmt.Sprintf("team %d applied", team.Status.TeamID),
	})
	team.Status.ObservedGeneration = team.Generation
	if err := r.Status().Update(ctx, &team); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(&team, nil, corev1.EventTypeNormal, terdutv1alpha1.ReasonTeamAdopted, terdutv1alpha1.ReasonTeamAdopted,
			"team applied")
	}
	log.Info("TerdutTeam ready", "name", team.Name, "teamID", team.Status.TeamID)

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

func nameTakenMessage(team *terdutv1alpha1.TerdutTeam) string {
	return fmt.Sprintf("the server already has a different team named %q; choose another spec.displayName, "+
		"or remove that team", team.Spec.DisplayName)
}

// serverClient builds a client for srv, authenticated with its operator key.
func (r *TerdutTeamReconciler) serverClient(ctx context.Context, srv *terdutv1alpha1.TerdutServer) (*tdclient.Client, error) {
	key, err := readOperatorKey(ctx, r.Client, srv)
	if err != nil {
		return nil, err
	}
	newClient := r.NewClient
	if newClient == nil {
		newClient = tdclient.New
	}
	return newClient(serviceURL(srv)).WithToken(key), nil
}

// teamError carries a condition reason/message, the same role databaseError
// plays for TerdutServer: an expected, requeue-and-retry outcome, not a
// reconcile failure.
type teamError struct {
	reason  string
	message string
}

func (e *teamError) Error() string { return e.message }

// resolveServerRef resolves spec.serverRef, including the cross-namespace
// consent check (DESIGN.md §4.6) when serverRef.namespace differs from this
// TerdutTeam's own.
func (r *TerdutTeamReconciler) resolveServerRef(ctx context.Context, team *terdutv1alpha1.TerdutTeam) (*terdutv1alpha1.TerdutServer, *teamError) {
	srv, ns, getErr := r.getServerRef(ctx, team)
	if getErr != nil {
		return nil, getErr
	}
	if ns == team.Namespace {
		return srv, nil
	}
	return r.checkConsent(ctx, team, srv, ns)
}

// getServerRef fetches the referenced TerdutServer and the namespace it was
// looked up in, without the consent check. Deleting a team uses it directly:
// consent gates what the operator will start acting on, not whether it may
// clean up after itself once the server owner has narrowed allowedTeams.
func (r *TerdutTeamReconciler) getServerRef(ctx context.Context, team *terdutv1alpha1.TerdutTeam) (*terdutv1alpha1.TerdutServer, string, *teamError) {
	ns := team.Spec.ServerRef.Namespace
	if ns == "" {
		ns = team.Namespace
	}

	var srv terdutv1alpha1.TerdutServer
	if err := r.Get(ctx, client.ObjectKey{Namespace: ns, Name: team.Spec.ServerRef.Name}, &srv); err != nil {
		if apierrors.IsNotFound(err) {
			return nil, ns, &teamError{
				reason:  terdutv1alpha1.ReasonServerRefNotFound,
				message: fmt.Sprintf("TerdutServer %q not found in namespace %q", team.Spec.ServerRef.Name, ns),
			}
		}
		return nil, ns, &teamError{reason: terdutv1alpha1.ReasonServerRefNotFound, message: err.Error()}
	}
	return &srv, ns, nil
}

// checkConsent applies DESIGN.md §4.6's allowedTeams gate to a cross-namespace
// reference.
func (r *TerdutTeamReconciler) checkConsent(ctx context.Context, team *terdutv1alpha1.TerdutTeam, srv *terdutv1alpha1.TerdutServer, ns string) (*terdutv1alpha1.TerdutServer, *teamError) {
	var ownNamespace corev1.Namespace
	if err := r.Get(ctx, client.ObjectKey{Name: team.Namespace}, &ownNamespace); err != nil {
		return nil, &teamError{
			reason:  terdutv1alpha1.ReasonRefNotPermitted,
			message: fmt.Sprintf("could not read this TerdutTeam's own namespace %q labels: %v", team.Namespace, err),
		}
	}
	permitted, err := allowedTeamsPermits(srv.Spec.AllowedTeams.Namespaces, ownNamespace.Labels)
	if err != nil {
		return nil, &teamError{reason: terdutv1alpha1.ReasonRefNotPermitted, message: err.Error()}
	}
	if !permitted {
		return nil, &teamError{
			reason: terdutv1alpha1.ReasonRefNotPermitted,
			message: fmt.Sprintf("TerdutServer %q/%q's spec.allowedTeams does not admit namespace %q",
				ns, team.Spec.ServerRef.Name, team.Namespace),
		}
	}
	return srv, nil
}

func (r *TerdutTeamReconciler) setTeamNotReady(
	ctx context.Context, team *terdutv1alpha1.TerdutTeam, reason, message string,
) (ctrl.Result, error) {
	meta.SetStatusCondition(&team.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionFalse,
		Reason:  reason,
		Message: message,
	})
	team.Status.ObservedGeneration = team.Generation
	if err := r.Status().Update(ctx, team); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(team, nil, corev1.EventTypeWarning, reason, reason, message)
	}
	return ctrl.Result{RequeueAfter: waitInterval}, nil
}

// reconcileTeamDelete removes the team on the server, then the finalizer. The
// server refuses while the team has open incidents (409), which surfaces as a
// retried error: tidying up must not be how a live page disappears.
func (r *TerdutTeamReconciler) reconcileTeamDelete(ctx context.Context, team *terdutv1alpha1.TerdutTeam) (ctrl.Result, error) {
	if !controllerutil.ContainsFinalizer(team, teamFinalizerName) {
		return ctrl.Result{}, nil
	}

	if team.Status.TeamID != 0 {
		if err := r.deleteTeamServerSide(ctx, team); err != nil {
			if r.Recorder != nil {
				r.Recorder.Eventf(team, nil, corev1.EventTypeWarning, "DeleteFailed", "DeleteFailed", err.Error())
			}
			return ctrl.Result{}, err
		}
	}

	controllerutil.RemoveFinalizer(team, teamFinalizerName)
	return ctrl.Result{}, r.Update(ctx, team)
}

func (r *TerdutTeamReconciler) deleteTeamServerSide(ctx context.Context, team *terdutv1alpha1.TerdutTeam) error {
	// Consent is deliberately not checked here: it gates what the operator
	// starts acting on, not whether it may clean up after itself once the
	// server owner has narrowed allowedTeams. Only a TerdutServer that is
	// really gone lets the delete proceed (there is nothing to delete against);
	// any other failure is retried rather than orphaning the team.
	srv, ns, getErr := r.getServerRef(ctx, team)
	if getErr != nil {
		var probe terdutv1alpha1.TerdutServer
		err := r.Get(ctx, client.ObjectKey{Namespace: ns, Name: team.Spec.ServerRef.Name}, &probe)
		if apierrors.IsNotFound(err) {
			return nil
		}
		return fmt.Errorf("reading TerdutServer %q/%q: %w", ns, team.Spec.ServerRef.Name, getErr)
	}
	tc, err := r.serverClient(ctx, srv)
	if err != nil {
		if apierrors.IsNotFound(err) {
			return nil // the key Secret went with its TerdutServer
		}
		return err
	}
	return tc.DeleteTeam(ctx, team.Status.TeamID)
}

// SetupWithManager sets up the controller with the Manager.
func (r *TerdutTeamReconciler) SetupWithManager(mgr ctrl.Manager) error {
	if r.NewClient == nil {
		r.NewClient = tdclient.New
	}
	if r.Recorder == nil {
		r.Recorder = mgr.GetEventRecorder("terdutteam-controller")
	}
	return ctrl.NewControllerManagedBy(mgr).
		For(&terdutv1alpha1.TerdutTeam{}).
		Watches(&terdutv1alpha1.TerdutServer{}, handler.EnqueueRequestsFromMapFunc(r.teamsForServer)).
		Named("terdutteam").
		Complete(r)
}

// teamsForServer re-reconciles every TerdutTeam that references a TerdutServer
// when it changes (becomes Ready, say), instead of polling for it.
func (r *TerdutTeamReconciler) teamsForServer(ctx context.Context, obj client.Object) []reconcile.Request {
	var teams terdutv1alpha1.TerdutTeamList
	if err := r.List(ctx, &teams); err != nil {
		return nil
	}
	var out []reconcile.Request
	for i := range teams.Items {
		t := &teams.Items[i]
		ns := t.Spec.ServerRef.Namespace
		if ns == "" {
			ns = t.Namespace
		}
		if t.Spec.ServerRef.Name == obj.GetName() && ns == obj.GetNamespace() {
			out = append(out, reconcile.Request{NamespacedName: client.ObjectKeyFromObject(t)})
		}
	}
	return out
}