package reconnect

import (
	"context"
	"fmt"
	"log"
	"sync"
	"time"

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

// EtcdRegistryConfig etcd 服务注册配置
type EtcdRegistryConfig struct {
	// Endpoints etcd 服务地址列表
	Endpoints []string
	// DialTimeout 连接超时时间
	DialTimeout time.Duration
	// ReconnectConfig 重连配置
	ReconnectConfig Config
}

// EtcdRegistry etcd 服务注册（带自动重连）
type EtcdRegistry struct {
	config      EtcdRegistryConfig
	etcdClient  *EtcdClient
	cli         *clientv3.Client
	key         string
	val         string
	serviceName string
	ttl         int64
	leaseID     clientv3.LeaseID
	keepAliveCh <-chan *clientv3.LeaseKeepAliveResponse
	mu          sync.RWMutex
	ctx         context.Context
	cancel      context.CancelFunc
}

// NewEtcdRegistry 创建带重连功能的 etcd 服务注册器
func NewEtcdRegistry(cfg EtcdRegistryConfig) (*EtcdRegistry, error) {
	ctx, cancel := context.WithCancel(context.Background())

	// 创建带重连的 etcd 客户端
	etcdCfg := EtcdClientConfig{
		Endpoints:       cfg.Endpoints,
		DialTimeout:     cfg.DialTimeout,
		ReconnectConfig: cfg.ReconnectConfig,
	}

	etcdClient, err := NewEtcdClient(etcdCfg)
	if err != nil {
		cancel()
		return nil, err
	}

	return &EtcdRegistry{
		config:     cfg,
		etcdClient: etcdClient,
		cli:        etcdClient.GetClient(),
		ctx:        ctx,
		cancel:     cancel,
	}, nil
}

// Register 注册服务
func (r *EtcdRegistry) Register(serviceName, addr string, ttl int64) error {
	r.mu.Lock()
	r.serviceName = serviceName
	r.ttl = ttl
	r.key = fmt.Sprintf("/%s/%s", serviceName, addr)
	r.val = addr
	r.mu.Unlock()

	return r.registerWithKV(ttl)
}

func (r *EtcdRegistry) registerWithKV(ttl int64) error {
	r.mu.RLock()
	cli := r.cli
	key := r.key
	val := r.val
	r.mu.RUnlock()

	if cli == nil {
		// 尝试重新获取客户端
		if r.etcdClient != nil {
			r.mu.Lock()
			r.cli = r.etcdClient.GetClient()
			cli = r.cli
			r.mu.Unlock()
		}
		if cli == nil {
			return fmt.Errorf("etcd client is nil")
		}
	}

	resp, err := cli.Grant(context.Background(), ttl)
	if err != nil {
		return err
	}

	r.mu.Lock()
	r.leaseID = resp.ID
	r.mu.Unlock()

	_, err = cli.Put(context.Background(), key, val, clientv3.WithLease(resp.ID))
	if err != nil {
		return err
	}

	keepAliveCh, err := cli.KeepAlive(context.Background(), resp.ID)
	if err != nil {
		return err
	}

	r.mu.Lock()
	r.keepAliveCh = keepAliveCh
	r.mu.Unlock()

	go r.watcher(ttl)
	log.Printf("[EtcdRegistry] 服务注册成功: %s", key)
	return nil
}

// watcher 监听续约
func (r *EtcdRegistry) watcher(ttl int64) {
	for {
		select {
		case <-r.ctx.Done():
			log.Println("[EtcdRegistry] context done, watcher exiting.")
			return
		case ka, ok := <-r.keepAliveCh:
			if !ok {
				log.Println("[EtcdRegistry] keep-alive channel closed, attempting to re-register...")

				// 更新 cli 引用
				if r.etcdClient != nil {
					r.mu.Lock()
					r.cli = r.etcdClient.GetClient()
					r.mu.Unlock()
				}

				// 使用指数退避重试
				delay := time.Second
				maxDelay := 30 * time.Second

				for {
					select {
					case <-r.ctx.Done():
						return
					default:
					}

					if err := r.registerWithKV(ttl); err != nil {
						log.Printf("[EtcdRegistry] failed to re-register service: %v, retrying in %v...", err, delay)
						time.Sleep(delay)
						delay *= 2
						if delay > maxDelay {
							delay = maxDelay
						}
					} else {
						return // 退出当前 goroutine，让新的 watcher 启动
					}
				}
			}
			// 续约成功
			_ = ka
		}
	}
}

// UnRegister 注销服务
func (r *EtcdRegistry) UnRegister() {
	r.cancel() // 停止 watcher

	r.mu.RLock()
	cli := r.cli
	leaseID := r.leaseID
	key := r.key
	r.mu.RUnlock()

	if cli != nil {
		cli.Revoke(context.Background(), leaseID)
		cli.Delete(context.Background(), key)
		log.Printf("[EtcdRegistry] 服务注销成功: %s", key)
	}

	if r.etcdClient != nil {
		r.etcdClient.Close()
	}
}

// State 获取连接状态
func (r *EtcdRegistry) State() ConnectionState {
	if r.etcdClient != nil {
		return r.etcdClient.State()
	}
	return StateDisconnected
}