package vkubelet

import (
	"context"
	"time"

	"github.com/cpuguy83/strongerrors/status/ocstatus"
	pkgerrors "github.com/pkg/errors"
	"github.com/virtual-kubelet/virtual-kubelet/log"
	"github.com/virtual-kubelet/virtual-kubelet/providers"
	"github.com/virtual-kubelet/virtual-kubelet/trace"
	coord "k8s.io/api/coordination/v1beta1"
	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes/typed/coordination/v1beta1"
	v1 "k8s.io/client-go/kubernetes/typed/core/v1"
)

// NewNode creates a new node.
// This does not have any side-effects on the system or kubernetes.
//
// Use the node's `Run` method to register and run the loops to update the node
// in Kubernetes.
func NewNode(p providers.NodeProvider, node *corev1.Node, leases v1beta1.LeaseInterface, nodes v1.NodeInterface, opts ...NodeOpt) (*Node, error) {
	n := &Node{p: p, n: node, leases: leases, nodes: nodes}
	for _, o := range opts {
		if err := o(n); err != nil {
			return nil, pkgerrors.Wrap(err, "error applying node option")
		}
	}
	return n, nil
}

// NodeOpt are the functional options used for configuring a node
type NodeOpt func(*Node) error

// WithNodeDisableLease forces node leases to be disabled and to only update
// using node status
// Note that this will force status updates to occur on the ping interval frequency
func WithNodeDisableLease(v bool) NodeOpt {
	return func(n *Node) error {
		n.disableLease = v
		return nil
	}
}

// WithNodePingInterval sets the inteval for checking node status
func WithNodePingInterval(d time.Duration) NodeOpt {
	return func(n *Node) error {
		n.pingInterval = d
		return nil
	}
}

// WithNodeStatusUpdateInterval sets the interval for updating node status
// This is only used when leases are supported and only for updating the actual
// node status, not the node lease.
func WithNodeStatusUpdateInterval(d time.Duration) NodeOpt {
	return func(n *Node) error {
		n.statusInterval = d
		return nil
	}
}

// WithNodeLease sets the base node lease to use.
// If a lease time is set, it will be ignored.
func WithNodeLease(l *coord.Lease) NodeOpt {
	return func(n *Node) error {
		n.lease = l
		return nil
	}
}

// Node deals with creating and managing a node object in Kubernetes.
// It can register a node with Kubernetes and periodically update its status.
type Node struct {
	p providers.NodeProvider
	n *corev1.Node

	leases v1beta1.LeaseInterface
	nodes  v1.NodeInterface

	disableLease   bool
	pingInterval   time.Duration
	statusInterval time.Duration
	lease          *coord.Lease
	chStatusUpdate chan *corev1.Node
}

// The default intervals used for lease and status updates.
const (
	DefaultPingInterval         = 5 * time.Second
	DefaultStatusUpdateInterval = 1 * time.Minute
)

// Run registers the node in kubernetes and starts loops for updating the node
// status in Kubernetes.
//
// The node status must be updated periodically in Kubertnetes to keep the node
// active. Newer versions of Kubernetes support node leases, which are
// essentially light weight pings. Older versions of Kubernetes require updating
// the node status periodically.
//
// If Kubernetes supports node leases this will use leases with a much slower
// node status update (because some things still expect the node to be updated
// periodically), otherwise it will only use node status update with the configured
// ping interval.
func (n *Node) Run(ctx context.Context) error {
	if n.pingInterval == time.Duration(0) {
		n.pingInterval = DefaultPingInterval
	}
	if n.statusInterval == time.Duration(0) {
		n.statusInterval = DefaultStatusUpdateInterval
	}

	if err := n.updateStatus(ctx); err != nil {
		return pkgerrors.Wrap(err, "error registering node with kubernetes")
	}
	log.G(ctx).Info("Created node")

	n.chStatusUpdate = make(chan *corev1.Node)
	n.p.NotifyNodeStatus(ctx, func(node *corev1.Node) {
		n.chStatusUpdate <- node
	})

	if !n.disableLease {
		n.lease = newLease(n.lease)
		setLeaseAttrs(n.lease, n.n, n.pingInterval*5)

		l, err := ensureLease(ctx, n.leases, n.lease)
		if err != nil {
			if errors.IsNotFound(err) {
				n.disableLease = true
			} else {
				return pkgerrors.Wrap(err, "error creating node lease")
			}
		}
		log.G(ctx).Debug("Created node lease")

		n.lease = l
	}

	if n.disableLease {
		log.G(ctx).Info("Node leases not supported, falling back to only node status updates")
	}

	n.controlLoop(ctx)
	return nil
}

func (n *Node) controlLoop(ctx context.Context) {
	pingTimer := time.NewTimer(n.pingInterval)
	defer pingTimer.Stop()

	statusTimer := time.NewTimer(n.statusInterval)
	defer statusTimer.Stop()
	if n.disableLease {
		// hack to make sure this channel always blocks since we won't be using it
		if !statusTimer.Stop() {
			<-statusTimer.C
		}
	}

	for {
		select {
		case <-ctx.Done():
			return
		case updated := <-n.chStatusUpdate:
			var t *time.Timer
			if n.disableLease {
				t = pingTimer
			} else {
				t = statusTimer
			}

			log.G(ctx).Debug("Received node status update")
			// Performing a status update so stop/reset the status update timer in this
			// branch otherwise there could be an uneccessary status update.
			if !t.Stop() {
				<-t.C
			}

			n.n.Status = updated.Status
			if err := n.updateStatus(ctx); err != nil {
				log.G(ctx).WithError(err).Error("Error handling node status update")
			}
			t.Reset(n.statusInterval)
		case <-statusTimer.C:
			if err := n.updateStatus(ctx); err != nil {
				log.G(ctx).WithError(err).Error("Error handling node status update")
			}
			statusTimer.Reset(n.statusInterval)
		case <-pingTimer.C:
			if err := n.handlePing(ctx); err != nil {
				log.G(ctx).WithError(err).Error("Error while handling node ping")
			} else {
				log.G(ctx).Debug("Successful node ping")
			}
			pingTimer.Reset(n.pingInterval)
		}
	}
}

func (n *Node) handlePing(ctx context.Context) (retErr error) {
	ctx, span := trace.StartSpan(ctx, "node.handlePing")
	defer span.End()
	defer func() {
		span.SetStatus(ocstatus.FromError(retErr))
	}()

	if err := n.p.Ping(ctx); err != nil {
		return pkgerrors.Wrap(err, "error whiling pinging node provider")
	}

	if n.disableLease {
		return n.updateStatus(ctx)
	}

	return n.updateLease(ctx)
}

func (n *Node) updateLease(ctx context.Context) error {
	l, err := UpdateNodeLease(ctx, n.leases, newLease(n.lease))
	if err != nil {
		return err
	}

	n.lease = l
	return nil
}

func (n *Node) updateStatus(ctx context.Context) error {
	updateNodeStatusHeartbeat(n.n)

	node, err := UpdateNodeStatus(ctx, n.nodes, n.n)
	if err != nil {
		return err
	}

	n.n = node
	return nil
}

func ensureLease(ctx context.Context, leases v1beta1.LeaseInterface, lease *coord.Lease) (*coord.Lease, error) {
	l, err := leases.Create(lease)
	if err != nil {
		switch {
		case errors.IsNotFound(err):
			log.G(ctx).WithError(err).Info("Node lease not supported")
			return nil, err
		case errors.IsAlreadyExists(err):
			if err := leases.Delete(lease.Name, nil); err != nil && !errors.IsNotFound(err) {
				log.G(ctx).WithError(err).Error("could not delete old node lease")
				return nil, pkgerrors.Wrap(err, "old lease exists but could not delete it")
			}
			l, err = leases.Create(lease)
		}
	}

	return l, err
}

// UpdateNodeLease updates the node lease.
//
// If this function returns an errors.IsNotFound(err) error, this likely means
// that node leases are not supported, if this is the case, call UpdateNodeStatus
// instead.
//
// If you use this function, it is up to you to syncronize this with other operations.
func UpdateNodeLease(ctx context.Context, leases v1beta1.LeaseInterface, lease *coord.Lease) (*coord.Lease, error) {
	ctx, span := trace.StartSpan(ctx, "node.UpdateNodeLease")
	defer span.End()

	ctx = span.WithFields(ctx, log.Fields{
		"lease.name": lease.Name,
		"lease.time": lease.Spec.RenewTime,
	})

	if lease.Spec.LeaseDurationSeconds != nil {
		ctx = span.WithField(ctx, "lease.expiresSeconds", *lease.Spec.LeaseDurationSeconds)
	}

	l, err := leases.Update(lease)
	if err != nil {
		if errors.IsNotFound(err) {
			log.G(ctx).Debug("lease not found")
			l, err = ensureLease(ctx, leases, lease)
		}
		if err != nil {
			span.SetStatus(ocstatus.FromError(err))
			return nil, err
		}
		log.G(ctx).Debug("created new lease")
	} else {
		log.G(ctx).Debug("updated lease")
	}

	return l, nil
}

// just so we don't have to allocate this on every get request
var emptyGetOptions = metav1.GetOptions{}

// UpdateNodeStatus triggers an update to the node status in Kubernetes.
// It first fetches the current node details and then sets the status according
// to the passed in node object.
//
// If you use this function, it is up to you to syncronize this with other operations.
func UpdateNodeStatus(ctx context.Context, nodes v1.NodeInterface, n *corev1.Node) (*corev1.Node, error) {
	ctx, span := trace.StartSpan(ctx, "UpdateNodeStatus")
	defer span.End()

	node, err := nodes.Get(n.Name, emptyGetOptions)
	if err != nil {
		if !errors.IsNotFound(err) {
			span.SetStatus(ocstatus.FromError(err))
			return nil, err
		}

		log.G(ctx).Debug("node not found")
		node, err = nodes.Create(n.DeepCopy())
		if err != nil {
			return nil, err
		}
		log.G(ctx).Debug("created new node")
		return node, nil
	}

	log.G(ctx).Debug("got node from api server")

	node.ResourceVersion = ""
	node.Status = n.Status

	ctx = addNodeAttributes(ctx, span, node)

	updated, err := nodes.UpdateStatus(node)
	if err != nil {
		return nil, err
	}

	log.G(ctx).WithField("resourceVersion", updated.ResourceVersion).Debug("updated node status in api server")
	return updated, nil
}

func newLease(base *coord.Lease) *coord.Lease {
	var lease *coord.Lease
	if base == nil {
		lease = &coord.Lease{}
	} else {
		lease = base.DeepCopy()
	}

	lease.Spec.RenewTime = &metav1.MicroTime{Time: time.Now()}
	return lease
}

func setLeaseAttrs(l *coord.Lease, n *corev1.Node, dur time.Duration) {
	if l.Name == "" {
		l.Name = n.Name
	}
	if l.Spec.HolderIdentity == nil {
		l.Spec.HolderIdentity = &n.Name
	}

	if l.Spec.LeaseDurationSeconds == nil {
		d := int32(dur.Seconds()) * 5
		l.Spec.LeaseDurationSeconds = &d
	}
}

func updateNodeStatusHeartbeat(n *corev1.Node) {
	now := metav1.NewTime(time.Now())
	for i, _ := range n.Status.Conditions {
		n.Status.Conditions[i].LastHeartbeatTime = now
	}
}

// NaiveNodeProvider is a basic node provider that only uses the passed in context
// on `Ping` to determine if the node is healthy.
type NaiveNodeProvider struct{}

// Ping just implements the NodeProvider interface.
// It returns the error from the passed in context only.
func (NaiveNodeProvider) Ping(ctx context.Context) error {
	return ctx.Err()
}

// NotifyNodeStatus implements the NodeProvider interface.
//
// This NaiveNodeProvider does not support updating node status and so this
// function is a no-op.
func (NaiveNodeProvider) NotifyNodeStatus(ctx context.Context, f func(*corev1.Node)) {
}

type taintsStringer []corev1.Taint

func (t taintsStringer) String() string {
	var s string
	for _, taint := range t {
		if s == "" {
			s = taint.Key + "=" + taint.Value + ":" + string(taint.Effect)
		} else {
			s += ", " + taint.Key + "=" + taint.Value + ":" + string(taint.Effect)
		}
	}
	return s
}

func addNodeAttributes(ctx context.Context, span trace.Span, n *corev1.Node) context.Context {
	return span.WithFields(ctx, log.Fields{
		"node.UID":     string(n.UID),
		"node.name":    n.Name,
		"node.cluster": n.ClusterName,
		"node.taints":  taintsStringer(n.Spec.Taints),
	})
}