package etcd

import (
	"context"
	"fmt"
	"git.diulo.com/mogfee/kit/registry"
	clientv3 "go.etcd.io/etcd/client/v3"
	"math/rand"
	"time"
)

type Option func(o *options)

type options struct {
	ctx       context.Context
	namespace string
	ttl       time.Duration
	maxRetry  int
}

func Context(ctx context.Context) Option {
	return func(o *options) {
		o.ctx = ctx
	}
}
func Namespace(ns string) Option {
	return func(o *options) {
		o.namespace = ns
	}
}
func RegisterTTL(ttl time.Duration) Option {
	return func(o *options) {
		o.ttl = ttl
	}
}
func MaxRetry(num int) Option {
	return func(o *options) {
		o.maxRetry = num
	}
}

type Registry struct {
	opts   *options
	client *clientv3.Client
	kv     clientv3.KV
	lease  clientv3.Lease
}

func New(client *clientv3.Client, opts ...Option) *Registry {
	op := &options{
		ctx:       context.Background(),
		namespace: "/microservices",
		ttl:       time.Second * 5,
		maxRetry:  5,
	}
	for _, o := range opts {
		o(op)
	}
	return &Registry{
		opts:   op,
		client: client,
		kv:     clientv3.NewKV(client),
	}
}

func (r *Registry) Register(ctx context.Context, service *registry.ServiceInstance) error {
	key := fmt.Sprintf("%s/%s/%s", r.opts.namespace, service.Name, service.ID)
	value, err := marshal(service)
	if err != nil {
		return err
	}
	if r.lease != nil {
		r.lease.Close()
	}
	r.lease = clientv3.NewLease(r.client)
	leaseId, err := r.registerWithKV(ctx, key, value)
	if err != nil {
		return err
	}
	go r.heartBeat(r.opts.ctx, leaseId, key, value)
	return nil
}

func (r *Registry) Deregister(ctx context.Context, service *registry.ServiceInstance) error {
	key := fmt.Sprintf("%s/%s/%s", r.opts.namespace, service.Name, service.ID)
	_, err := r.client.Delete(ctx, key)
	return err
}
func (r *Registry) GetService(ctx context.Context, serverName string) ([]*registry.ServiceInstance, error) {
	key := fmt.Sprintf("%s/%s", r.opts.namespace, serverName)
	resp, err := r.kv.Get(ctx, key, clientv3.WithPrefix())
	if err != nil {
		return nil, err
	}
	items := make([]*registry.ServiceInstance, 0)
	for _, kv := range resp.Kvs {
		si, err := unmarshal(kv.Value)
		if err != nil {
			return nil, err
		}
		if si.Name != serverName {
			continue
		}
		items = append(items, si)
	}
	return items, nil
}

func (r *Registry) Watch(ctx context.Context, serviceName string) (registry.Watcher, error) {
	key := fmt.Sprintf("%s/%s", r.opts.namespace, serviceName)
	return newWatcher(ctx, key, serviceName, r.client)
}
func (r *Registry) registerWithKV(ctx context.Context, key string, value string) (clientv3.LeaseID, error) {
	grant, err := r.client.Grant(ctx, int64(r.opts.ttl.Seconds()))
	if err != nil {
		return 0, err
	}
	_, err = r.client.Put(ctx, key, value, clientv3.WithLease(grant.ID))
	if err != nil {
		return 0, err
	}
	return grant.ID, nil
}
func (r *Registry) heartBeat(ctx context.Context, leaseId clientv3.LeaseID, key string, value string) {
	curLeaseId := leaseId
	kac, err := r.client.KeepAlive(ctx, leaseId)
	if err != nil {
		curLeaseId = 0
	}
	rand.Seed(time.Now().Unix())
	for {
		if curLeaseId == 0 {
			var retreat []int
			for retryCnt := 0; retryCnt < r.opts.maxRetry; retryCnt++ {
				if ctx.Err() != nil {
					return
				}

				idChan := make(chan clientv3.LeaseID, 1)
				errChan := make(chan error, 1)
				cancelCtx, cancel := context.WithCancel(ctx)
				go func() {
					defer cancel()
					id, registerErr := r.registerWithKV(cancelCtx, key, value)
					if registerErr != nil {
						errChan <- registerErr
					} else {
						idChan <- id
					}
				}()

				select {
				case <-time.After(3 * time.Second):
					cancel()
					continue
				case <-errChan:
					continue
				case curLeaseId = <-idChan:
				}
				kac, err = r.client.KeepAlive(ctx, curLeaseId)
				if err != nil {
					break
				}
				retreat := append(retreat, 1<<retryCnt)
				time.Sleep(time.Duration(retreat[rand.Intn(len(retreat))]) * time.Second)
			}
			if _, ok := <-kac; !ok {
				return
			}
		}

		select {
		case _, ok := <-kac:
			if !ok {
				if ctx.Err() != nil {
					return
				}
				curLeaseId = 0
				continue
			}
		case <-r.opts.ctx.Done():
			return
		}
	}
}