// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package controllers

import (
	"context"
	"errors"
	"fmt"

	"github.com/go-logr/logr"
	corev1 "k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/tools/record"
	"k8s.io/client-go/tools/reference"
	"k8s.io/utils/pointer"
	capiv1 "sigs.k8s.io/cluster-api/api/v1alpha3"
	"sigs.k8s.io/cluster-api/util"
	"sigs.k8s.io/cluster-api/util/patch"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/controller"
	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"

	infrav1 "github.com/talos-systems/sidero/app/caps-controller-manager/api/v1alpha3"
	"github.com/talos-systems/sidero/app/caps-controller-manager/pkg/constants"
	metalv1alpha1 "github.com/talos-systems/sidero/app/sidero-controller-manager/api/v1alpha1"
)

var ErrNoServersInServerClass = errors.New("no servers available in serverclass")

// MetalMachineReconciler reconciles a MetalMachine object.
type MetalMachineReconciler struct {
	client.Client
	Log      logr.Logger
	Scheme   *runtime.Scheme
	Recorder record.EventRecorder
}

// +kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=metalmachines,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=metalmachines/status,verbs=get;update;patch
// +kubebuilder:rbac:groups=cluster.x-k8s.io,resources=machines;machines/status,verbs=get;list;watch
// +kubebuilder:rbac:groups=metal.sidero.dev,resources=serverclasses,verbs=get;list;watch;
// +kubebuilder:rbac:groups=metal.sidero.dev,resources=serverclasses/status,verbs=get;list;watch;
// +kubebuilder:rbac:groups=metal.sidero.dev,resources=servers,verbs=get;list;watch;
// +kubebuilder:rbac:groups=metal.sidero.dev,resources=servers/status,verbs=get;update;patch
// +kubebuilder:rbac:groups="",resources=secrets,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups="",resources=events,verbs=create;patch

func (r *MetalMachineReconciler) Reconcile(req ctrl.Request) (_ ctrl.Result, err error) {
	ctx := context.Background()
	logger := r.Log.WithValues("metalmachine", req.NamespacedName)

	// Fetch the metalMachine instance.
	metalMachine := &infrav1.MetalMachine{}

	err = r.Get(ctx, req.NamespacedName, metalMachine)
	if apierrors.IsNotFound(err) {
		return ctrl.Result{}, nil
	}

	if err != nil {
		return ctrl.Result{}, err
	}

	machine, err := util.GetOwnerMachine(ctx, r.Client, metalMachine.ObjectMeta)
	if err != nil {
		r.Log.Error(err, "Failed to get machine")

		return ctrl.Result{RequeueAfter: constants.DefaultRequeueAfter}, nil
	}

	if machine == nil {
		logger.Info("No ownerref for metalmachine")

		return ctrl.Result{RequeueAfter: constants.DefaultRequeueAfter}, nil
	}

	logger = logger.WithName(fmt.Sprintf("machine=%s", machine.Name))

	cluster, err := util.GetClusterFromMetadata(ctx, r.Client, machine.ObjectMeta)
	if err != nil {
		return ctrl.Result{}, fmt.Errorf("no cluster label or cluster does not exist")
	}

	logger = logger.WithName(fmt.Sprintf("cluster=%s", cluster.Name))

	if !cluster.Status.InfrastructureReady {
		logger.Error(err, "Cluster infrastructure is not ready", "cluster", cluster.Name)

		return ctrl.Result{RequeueAfter: constants.DefaultRequeueAfter}, nil
	}

	if machine.Spec.Bootstrap.DataSecretName == nil {
		logger.Info(" Bootstrap secret is not available yet")

		return ctrl.Result{RequeueAfter: constants.DefaultRequeueAfter}, nil
	}

	// Initialize the patch helper
	patchHelper, err := patch.NewHelper(metalMachine, r)
	if err != nil {
		return ctrl.Result{}, err
	}

	// Always attempt to Patch the MetalMachine object and status after each reconciliation.
	defer func() {
		if e := patchHelper.Patch(ctx, metalMachine); e != nil {
			logger.Error(e, "failed to patch metalMachine")

			if err == nil {
				err = e
			}
		}
	}()

	// Handle deleted machines
	if !metalMachine.ObjectMeta.DeletionTimestamp.IsZero() {
		logger.Info("deleting metalmachine")

		return r.reconcileDelete(ctx, metalMachine)
	}

	controllerutil.AddFinalizer(metalMachine, infrav1.MachineFinalizer)

	// If server ref is already provided, server binding controller is going to reconcile matching server binding
	// if server binding is missing, need to pick up a server
	if metalMachine.Spec.ServerRef == nil {
		if metalMachine.Spec.ServerClassRef == nil {
			return ctrl.Result{}, fmt.Errorf("either a server or serverclass ref must be supplied")
		}

		serverResource, err := r.fetchServerFromClass(ctx, logger, metalMachine.Spec.ServerClassRef, metalMachine)
		if err != nil {
			if errors.Is(err, ErrNoServersInServerClass) {
				return ctrl.Result{RequeueAfter: constants.DefaultRequeueAfter}, nil
			}

			return ctrl.Result{}, err
		}

		metalMachine.Spec.ServerRef = &corev1.ObjectReference{
			Kind: serverResource.Kind,
			Name: serverResource.Name,
		}
	}

	// Set the providerID, as its required in upstream capi for machine lifecycle
	metalMachine.Spec.ProviderID = pointer.StringPtr(fmt.Sprintf("%s://%s", constants.ProviderID, metalMachine.Spec.ServerRef.Name))

	err = r.patchProviderID(ctx, cluster, metalMachine)
	if err != nil {
		logger.Info("Failed to set provider ID", "error", err)

		return ctrl.Result{RequeueAfter: constants.DefaultRequeueAfter}, nil
	}

	metalMachine.Status.Ready = true

	return ctrl.Result{}, nil
}

func (r *MetalMachineReconciler) reconcileDelete(ctx context.Context, metalMachine *infrav1.MetalMachine) (ctrl.Result, error) {
	if metalMachine.Spec.ServerRef != nil {
		var serverBinding infrav1.ServerBinding

		err := r.Get(ctx, types.NamespacedName{Namespace: metalMachine.Spec.ServerRef.Namespace, Name: metalMachine.Spec.ServerRef.Name}, &serverBinding)
		if err == nil {
			return ctrl.Result{Requeue: true}, r.Delete(ctx, &serverBinding)
		}

		if !apierrors.IsNotFound(err) {
			return ctrl.Result{}, err
		}
	}

	metalMachine.Spec.ServerRef = nil

	controllerutil.RemoveFinalizer(metalMachine, infrav1.MachineFinalizer)

	return ctrl.Result{}, nil
}

func (r *MetalMachineReconciler) SetupWithManager(mgr ctrl.Manager, options controller.Options) error {
	if err := mgr.GetFieldIndexer().IndexField(&infrav1.ServerBinding{}, infrav1.ServerBindingMetalMachineRefField, func(rawObj runtime.Object) []string {
		serverBinding := rawObj.(*infrav1.ServerBinding)

		return []string{serverBinding.Spec.MetalMachineRef.Name}
	}); err != nil {
		return err
	}

	return ctrl.NewControllerManagedBy(mgr).
		WithOptions(options).
		For(&infrav1.MetalMachine{}).
		Complete(r)
}

func (r *MetalMachineReconciler) fetchServerFromClass(ctx context.Context, logger logr.Logger, classRef *corev1.ObjectReference, metalMachine *infrav1.MetalMachine) (*metalv1alpha1.Server, error) {
	// First, check if there is already existing serverBinding for this metalmachine
	var serverBindingList infrav1.ServerBindingList

	if err := r.List(ctx, &serverBindingList, client.MatchingFields(fields.Set{infrav1.ServerBindingMetalMachineRefField: metalMachine.Name})); err != nil {
		return nil, err
	}

	for _, serverBinding := range serverBindingList.Items {
		if serverBinding.Spec.MetalMachineRef.Namespace == metalMachine.Namespace && serverBinding.Spec.MetalMachineRef.Name == metalMachine.Name {
			// found existing serverBinding for this metalMachine
			var server metalv1alpha1.Server

			if err := r.Get(ctx, types.NamespacedName{Namespace: serverBinding.Namespace, Name: serverBinding.Name}, &server); err != nil {
				return nil, err
			}

			logger.Info("reconciled missing server ref", "metalmachine", metalMachine.Name, "server", server.Name)

			return &server, nil
		}
	}

	// Grab server class and validate that we have nodes available
	serverClassResource, err := r.fetchServerClass(ctx, classRef)
	if err != nil {
		return nil, err
	}

	if len(serverClassResource.Status.ServersAvailable) == 0 {
		return nil, ErrNoServersInServerClass
	}

	// Fetch server from available list
	// NB: we added this loop to double check that an available server isn't "in use" because
	//     we saw raciness between server selection and it being removed from the ServersAvailable list.
	for _, availServer := range serverClassResource.Status.ServersAvailable {
		serverObj := &metalv1alpha1.Server{}

		namespacedName := types.NamespacedName{
			Namespace: "",
			Name:      availServer,
		}

		if err := r.Get(ctx, namespacedName, serverObj); err != nil {
			return nil, err
		}

		if serverObj.Status.InUse {
			continue
		}

		if !serverObj.Status.IsClean {
			continue
		}

		if err := r.createServerBinding(ctx, serverClassResource, serverObj, metalMachine); err != nil {
			// the server we picked was updated by another metalmachine before we finished.
			// move on to the next one.
			if apierrors.IsAlreadyExists(err) {
				continue
			}

			return nil, err
		}

		logger.Info("allocated new server", "metalmachine", metalMachine.Name, "server", serverObj.Name, "serverclass", serverClassResource.Name)

		return serverObj, nil
	}

	return nil, ErrNoServersInServerClass
}

func (r *MetalMachineReconciler) patchProviderID(ctx context.Context, cluster *capiv1.Cluster, metalMachine *infrav1.MetalMachine) error {
	kubeconfigSecret := &corev1.Secret{}

	err := r.Client.Get(ctx,
		types.NamespacedName{
			Namespace: cluster.Namespace,
			Name:      cluster.Name + "-kubeconfig",
		},
		kubeconfigSecret,
	)
	if err != nil {
		return err
	}

	config, err := clientcmd.RESTConfigFromKubeConfig(kubeconfigSecret.Data["value"])
	if err != nil {
		return err
	}

	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		return err
	}

	label := fmt.Sprintf("metal.sidero.dev/uuid=%s", metalMachine.Spec.ServerRef.Name)

	r.Log.Info("Searching for node", "label", label)

	nodes, err := clientset.CoreV1().Nodes().List(
		metav1.ListOptions{
			LabelSelector: label,
		},
	)
	if err != nil {
		return err
	}

	if len(nodes.Items) == 0 {
		return fmt.Errorf("no matching nodes found")
	}

	if len(nodes.Items) > 1 {
		return fmt.Errorf("multiple nodes found with same uuid label")
	}

	providerID := fmt.Sprintf("%s://%s", constants.ProviderID, metalMachine.Spec.ServerRef.Name)

	r.Log.Info("Setting provider ID", "id", providerID)

	for _, node := range nodes.Items {
		node := node

		if node.Spec.ProviderID == providerID {
			continue
		}

		node.Spec.ProviderID = providerID

		_, err = clientset.CoreV1().Nodes().Update(&node)
		if err != nil {
			return err
		}
	}

	return nil
}

// createServerBinding updates a server to mark it as "in use" via ServerBinding resource.
func (r *MetalMachineReconciler) createServerBinding(ctx context.Context, serverClass *metalv1alpha1.ServerClass, serverObj *metalv1alpha1.Server, metalMachine *infrav1.MetalMachine) error {
	serverRef, err := reference.GetReference(r.Scheme, serverObj)
	if err != nil {
		return err
	}

	var serverBinding infrav1.ServerBinding

	serverBinding.Namespace = serverObj.Namespace
	serverBinding.Name = serverObj.Name
	serverBinding.Labels = make(map[string]string)
	serverBinding.Spec.MetalMachineRef = corev1.ObjectReference{
		Kind:      metalMachine.Kind,
		UID:       metalMachine.UID,
		Namespace: metalMachine.Namespace,
		Name:      metalMachine.Name,
	}

	if serverClass != nil {
		serverBinding.Spec.ServerClassRef = &corev1.ObjectReference{
			Kind: serverClass.Kind,
			Name: serverClass.Name,
		}
	}

	for label, value := range metalMachine.Labels {
		serverBinding.Labels[label] = value
	}

	err = r.Create(ctx, &serverBinding)
	if err == nil {
		r.Recorder.Event(serverRef, corev1.EventTypeNormal, "Server Allocation", fmt.Sprintf("Server as allocated via serverclass %q for metal machine %q.", serverClass.Name, metalMachine.Name))
	}

	return err
}

func (r *MetalMachineReconciler) fetchServerClass(ctx context.Context, classRef *corev1.ObjectReference) (*metalv1alpha1.ServerClass, error) {
	serverClassResource := &metalv1alpha1.ServerClass{}

	namespacedName := types.NamespacedName{
		Namespace: classRef.Namespace,
		Name:      classRef.Name,
	}

	if err := r.Get(ctx, namespacedName, serverClassResource); err != nil {
		return nil, err
	}

	return serverClassResource, nil
}