package a2s

import (
	"fmt"
	"log"
	"math/rand"
	"strings"
	"sync"
	"time"

	"github.com/golang/protobuf/proto"
	"github.com/nats-io/nats.go"
)

const (
	ID_LENGTH = 32
)

type (
	Bytes []byte
	//观察结果
	WatchResponse struct {
		lock  *sync.RWMutex
		cache map[string]chan Bytes
	}
	//坚听返回队列
	WatchNatsQueue struct {
		lock  *sync.RWMutex
		cache map[string]bool
	}
)

var (
	noice = "abcdefghijklmnopqrstuvwxyz0123456789"
	nc    *nats.Conn
	w     = &WatchResponse{new(sync.RWMutex), make(map[string]chan Bytes)}
	wnq   = &WatchNatsQueue{new(sync.RWMutex), make(map[string]bool)}
)

// id
func id() string {
	sb := new(strings.Builder)
	for i := 0; i < ID_LENGTH; i++ {
		sb.WriteByte(noice[rand.Intn(36)])
	}
	return sb.String()
}

// Add 方法调用时，添加观察
func (wr *WatchResponse) Add(msgId string, ch chan Bytes) {
	wr.lock.Lock()
	defer wr.lock.Unlock()
	wr.cache[msgId] = ch
}

// Del 超时/成功时，删除观察
func (wr *WatchResponse) Del(msgId string) {
	wr.lock.Lock()
	defer wr.lock.Unlock()
	if v, ok := wr.cache[msgId]; ok {
		close(v)
		delete(wr.cache, msgId)
	}
}

// Put 写入channel，select观察会有响应
func (wr *WatchResponse) Put(msgId string, data Bytes) {
	wr.lock.Lock()
	defer wr.lock.Unlock()
	if v, ok := wr.cache[msgId]; ok {
		v <- data
	}
}

// Watch
func (wnq *WatchNatsQueue) Watch(topic string) {
	wnq.lock.Lock()
	defer wnq.lock.Unlock()
	if _, ok := wnq.cache[topic]; ok {
		return
	} else {
		wnq.cache[topic] = true
		rawTopic := fmt.Sprintf("%s_resp", topic)
		nc.QueueSubscribe(rawTopic, rawTopic, func(msg *nats.Msg) {
			obj := new(NatsResponse)
			err := proto.Unmarshal(msg.Data, obj)
			if err == nil {
				w.Put(obj.GetMsgId(), obj.GetData())
			}
		})
	}
}

// ConnectNats
func ConnectNats(addr string) error {
	var err error
	natsAddr := fmt.Sprintf("nats://%s", addr)
	log.Println(natsAddr)
	nc, err = nats.Connect(natsAddr)
	return err
}

// SendMessage2Nats
func SendMessage2Nats(topic string,
	timeout int64,
	data []byte) (string, <-chan Bytes, error) {
	rawTopic := fmt.Sprintf("%s_req", topic)
	//
	msgId := id()
	rawData := &NatsRequest{
		MsgId:     msgId,
		Timestamp: time.Now().Unix(),
		Timeout:   timeout,
		Data:      data,
	}
	//
	bs, err := proto.Marshal(rawData)
	if err != nil {
		return "", nil, err
	}
	//发布消息到指定队列
	err = nc.Publish(rawTopic, bs)
	if err != nil {
		return "", nil, err
	}
	ch := make(chan Bytes, 1)
	//
	wnq.Watch(topic)
	//
	w.Add(msgId, ch)
	return msgId, ch, nil
}