package etcdv3

import (
	"sync"
	"time"

	"go.etcd.io/etcd/clientv3"
)

import (
	"github.com/coreos/etcd/mvcc/mvccpb"
)

import (
	"github.com/apache/dubbo-go/common/logger"
	"github.com/apache/dubbo-go/remoting"
)

type EventListener struct {
	client     *Client
	keyMapLock sync.Mutex
	keyMap     map[string]struct{}
	wg         sync.WaitGroup
}

func NewEventListener(client *Client) *EventListener {
	return &EventListener{
		client: client,
		keyMap: make(map[string]struct{}),
	}
}
func (l *EventListener) SetClient(client *Client) {
	l.client = client
}

// Listen on a spec key
// this method will return true when spec key deleted,
// this method will return false when deep layer connection lose
func (l *EventListener) ListenServiceNodeEvent(key string, listener ...remoting.DataListener) bool {
	l.wg.Add(1)
	defer l.wg.Done()
	for {
		keyEventCh, err := l.client.WatchExist(key)
		if err != nil {
			logger.Warnf("WatchExist{key:%s} = error{%v}", key, err)
			return false
		}

		select {
		// client watch ctx stop
		// server stopped
		case <-l.client.cs.ctx.Done():
			return false

		// client stopped
		case <-l.client.Done():
			return false

		// etcd event stream
		case e := <-keyEventCh:

			if e.Err() != nil {
				logger.Errorf("get a etcdv3 event {err: %s}", e.Err())
				continue
			}
			for _, event := range e.Events {
				if l.handleEvents(event, listener...) {
					return true
				}
			}
		}
	}

	return false
}

// return true mean the event type is DELETE
// return false mean the event type is CREATE || UPDATE
func (l *EventListener) handleEvents(event *clientv3.Event, listeners ...remoting.DataListener) bool {

	logger.Warnf("get a etcdv3 Event {type: %s, key: %s}", event.Type, event.Kv.Key)

	switch event.Type {
	// the etcdv3 event just include PUT && DELETE
	case mvccpb.PUT:
		for _, listener := range listeners {
			switch event.IsCreate() {
			case true:
				logger.Warnf("etcdv3.ExistW(key{%s}) = event{EventNodeDataCreated}", event.Kv.Key)
				listener.DataChange(remoting.Event{
					Path:    string(event.Kv.Key),
					Action:  remoting.EventTypeAdd,
					Content: string(event.Kv.Value),
				})
			case false:
				logger.Warnf("etcdv3.ExistW(key{%s}) = event{EventNodeDataChanged}", event.Kv.Key)
				listener.DataChange(remoting.Event{
					Path:    string(event.Kv.Key),
					Action:  remoting.EvnetTypeUpdate,
					Content: string(event.Kv.Value),
				})
			}
		}
		return false
	case mvccpb.DELETE:
		logger.Warnf("etcdv3.ExistW(key{%s}) = event{EventNodeDeleted}", event.Kv.Key)
		return true
	}

	panic("unreachable")
}

// Listen on a set of key with spec prefix
func (l *EventListener) ListenServiceNodeEventWithPrefix(prefix string, listener ...remoting.DataListener) {

	l.wg.Add(1)
	defer l.wg.Done()
	for {
		_, _, wc, err := l.client.WatchChildren(prefix)
		if err != nil {
			logger.Warnf("listenDirEvent(key{%s}) = error{%v}", prefix, err)
		}

		select {

		// client watch ctx stop
		// server stopped
		case <-l.client.cs.ctx.Done():
			logger.Warn("etcd listener service node with prefix etcd server stopped")
			return

		// client stopped
		case <-l.client.Done():
			logger.Warn("etcdv3 client stopped")
			return

			// etcd event stream
		case e := <-wc:
			if e.Err() != nil {
				logger.Errorf("get a etcdv3 event {err: %s}", e.Err())
				continue
			}
			for _, event := range e.Events {
				l.handleEvents(event, listener...)
			}
		}
	}
}

func timeSecondDuration(sec int) time.Duration {
	return time.Duration(sec) * time.Second
}

// this func is invoked by etcdv3 ConsumerRegistry::Registe/ etcdv3 ConsumerRegistry::get/etcdv3 ConsumerRegistry::getListener
// registry.go:Listen -> listenServiceEvent -> listenDirEvent -> ListenServiceNodeEvent
//                            |
//                            --------> ListenServiceNodeEvent
func (l *EventListener) ListenServiceEvent(key string, listener remoting.DataListener) {

	l.keyMapLock.Lock()
	_, ok := l.keyMap[key]
	l.keyMapLock.Unlock()
	if ok {
		logger.Warnf("etcdv3 key %s has already been listened.", key)
		return
	}

	l.keyMapLock.Lock()
	l.keyMap[key] = struct{}{}
	l.keyMapLock.Unlock()

	logger.Infof("listen dubbo provider key{%s} event and wait to get all provider etcdv3 nodes", key)
	go func(key string, listener remoting.DataListener) {
		l.ListenServiceNodeEventWithPrefix(key, listener)
		logger.Warnf("listenDirEvent(key{%s}) goroutine exit now", key)
	}(key, listener)

	logger.Infof("listen dubbo service key{%s}", key)
	go func(key string) {
		if l.ListenServiceNodeEvent(key) {
			listener.DataChange(remoting.Event{Path: key, Action: remoting.EventTypeDel})
		}
		logger.Warnf("listenSelf(etcd key{%s}) goroutine exit now", key)
	}(key)
}

func (l *EventListener) valid() bool {
	return l.client.Valid()
}

func (l *EventListener) Close() {
	l.wg.Wait()
}