package session

import (
	"encoding/json"
	"errors"
	"github.com/garyburd/redigo/redis"
	"sync"
)

type RedisSession struct {
	sessionId string
	pool      *redis.Pool
	//设置session key value
	sessionMap map[string]interface{}
	rwLock     sync.RWMutex
	flag       int
}

//用常量定义状态

const (
	//内存数据没变化
	SessionFlagNone = iota

	SessionFlagModify
)

//构造函数

func NewRedisSession(pool *redis.Pool, id string) *RedisSession {
	s := &RedisSession{
		sessionId:  id,
		pool:       pool,
		sessionMap: make(map[string]interface{}, 16),
		flag:       SessionFlagNone,
	}
	return s
}

func (r *RedisSession) Set(key string, value interface{}) (err error) {
	r.rwLock.Lock()
	defer r.rwLock.Unlock()
	r.sessionMap[key] = value
	//flag
	r.flag = SessionFlagModify
	return
}

func (r *RedisSession) Save() (err error) {
	r.rwLock.RLock()
	defer r.rwLock.RUnlock()
	//如果数据没变，不需要存
	if r.flag != SessionFlagModify {
		return
	}
	//内存中的sessionMap进行序列化
	data, err := json.Marshal(r.sessionMap)
	if err != nil {
		return
	}
	//获取redis链接
	_, err = r.pool.Get().Do("SET", r.sessionId, string(data))
	r.flag = SessionFlagNone
	if err != nil {
		return
	}
	return
}

func (r *RedisSession) Get(key string) (result interface{}, err error) {
	r.rwLock.RLock()
	defer r.rwLock.RUnlock()

	//判断内存有没有数据
	result, ok := r.sessionMap[key]
	if !ok {
		err = errors.New("key not found")
		return
	}
	return
}

//从redis里再次加载

func (r *RedisSession) LoadFormRedis() (err error) {
	reply, err := r.pool.Get().Do("GET", r.sessionId)
	if err != nil {
		return
	}
	//转字符串
	data, err := redis.String(reply, err)
	if err != nil {
		return
	}
	//取到的东西反序列化到内存的map中
	err = json.Unmarshal([]byte(data), &r.sessionMap)
	if err != nil {
		return
	}
	return
}

func (r *RedisSession) Del(key string) (err error) {
	r.rwLock.Lock()
	defer r.rwLock.Unlock()
	r.flag = SessionFlagModify
	delete(r.sessionMap, key)
	return
}