package etcd

import (
	"context"
	"fmt"
	"github.com/fox/fox/ksync"
	"github.com/fox/fox/log"
	"sync"
	"time"

	clientv3 "go.etcd.io/etcd/client/v3"
)

const (
	DefaultDialTimeout       = 3 * time.Second // 默认拨号超时时间
	DefaultLeaseTTL          = int64(10)       // 默认租约TTL为60秒
	DefaultKeepAliveInterval = 5 * time.Second // 默认续租间隔为30秒
	KeepAliveFailCount       = 1
)

type etcdRegistryImpl struct {
	cli          *clientv3.Client
	leaseID      clientv3.LeaseID
	meNodeKey    string // 自身节点key
	meNodeValue  string // 自身节点json
	cancelFunc   context.CancelFunc
	rootKey      string
	nodeOperator iNodeOperator
}

// 创建服务注册中心
func newServiceRegistryImpl(endpoints []string, rootKey, username, password string, operator iNodeOperator, meKey, meValue string) (*etcdRegistryImpl, error) {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   endpoints,
		DialTimeout: DefaultDialTimeout,
		Username:    username,
		Password:    password,
	})
	if err != nil {
		return nil, err
	}

	impl := &etcdRegistryImpl{
		cli:          cli,
		rootKey:      rootKey,
		nodeOperator: operator,
		meNodeKey:    meKey,
		meNodeValue:  meValue,
	}
	if err = impl.register(); err != nil {
		return nil, err
	}
	impl.watchServices()
	return impl, nil
}

// 注册服务 RegisterService
func (sr *etcdRegistryImpl) register() error {
	// 生成唯一服务key
	// /services/serviceType/serviceName
	log.DebugF("register key:%s value:%v to etcd", sr.meNodeKey, sr.meNodeValue)

	// 创建租约
	ctx, cancel := context.WithCancel(context.Background())
	sr.cancelFunc = cancel

	// 申请租约
	resp, err := sr.cli.Grant(ctx, DefaultLeaseTTL)
	if err != nil {
		return err
	}
	sr.leaseID = resp.ID

	// 序列化服务信息
	// data, err := json.Marshal(node)
	// if err != nil {
	// 	return err
	// }

	// 写入ETCD
	_, err = sr.cli.Put(ctx, sr.meNodeKey, sr.meNodeValue, clientv3.WithLease(sr.leaseID))
	if err != nil {
		return err
	}

	// 启动自动续租
	ksync.GoSafe(func() { sr.keepAlive(ctx) }, nil)

	if err = sr.discoverServices(); err == nil {
		// ss := sr.GetService()
		// for _, s := range ss {
		// 	log.Debug(fmt.Sprintf("Discovered services: %+v\n", s))
		// }

	}
	return nil
}

// 自动续租逻辑
func (sr *etcdRegistryImpl) keepAlive(ctx context.Context) {
	retryCount := 0
	ticker := time.NewTicker(DefaultKeepAliveInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			_, err := sr.cli.KeepAliveOnce(ctx, sr.leaseID)
			if err != nil {
				if retryCount > KeepAliveFailCount {
					log.DebugF("KeepAlive failed after %d retries: %v", KeepAliveFailCount, err)
					sr.UnregisterService()
					if err = sr.register(); err != nil {
						log.ErrorF("Reconnect failed: %v", err)
					} else {
						retryCount = 0
					}
					return
				}
				retryCount++
				// log.DebugF("KeepAlive error (retry %d/%d): %v", retryCount, KeepAliveFailCount, err)
			} else {
				retryCount = 0
			}
		case <-ctx.Done():
			return
		}
	}
}

// 反注册服务
func (sr *etcdRegistryImpl) UnregisterService() {
	if sr.cancelFunc != nil {
		sr.cancelFunc()
	}

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	if _, err := sr.cli.Delete(ctx, sr.meNodeKey); err != nil {
		log.ErrorF("unregister:%v failed:%v from etcd", sr.meNodeKey, err)
	} else {
		log.DebugF("unregister:%v from etcd", sr.meNodeKey)
	}
}

// 服务发现
func (sr *etcdRegistryImpl) discoverServices() error {
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	srv := fmt.Sprintf("/%s/", sr.rootKey)
	resp, err := sr.cli.Get(ctx, srv, clientv3.WithPrefix())
	if err != nil {
		return err
	}
	//log.Debug(fmt.Sprintf("discoverServices srv:%s", srv))

	newNodes := &sync.Map{}
	for _, kv := range resp.Kvs {
		sr.nodeOperator.saveNode(newNodes, kv.Value)
		//log.Debug(fmt.Sprintf("save node key:%s value:%s", string(kv.Key), string(kv.Value)))
	}
	sr.nodeOperator.replace(newNodes)

	return nil
}

// 监控服务变化
func (sr *etcdRegistryImpl) watchServices() {
	watchKey := fmt.Sprintf("/%s/", sr.rootKey)
	ksync.GoSafe(func() {
		rch := sr.cli.Watch(context.Background(), watchKey, clientv3.WithPrefix())
		for resp := range rch {
			for range resp.Events {
				// 当有变化时获取最新服务列表
				if err := sr.discoverServices(); err != nil {
					log.Error(err.Error())
				}
			}
		}
	}, nil)
}