package mongos

import (
	"context"
	"time"
	"videoweb/pub/models/utils"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo"
)

const notFindMsg = "mongo: no documents in result"

type lid struct {
	db         *Collection // 数据库连接
	businessId string      // 业务id
	ch         chan int64  // id缓冲池
	min, max   int64       // id段最小值，最大值
}

// newLid 创建一个lid,db:数据库连接；businessId：业务id;len：缓冲池大小
func newLid(db *Collection, businessId string, len int) (*lid, error) {
	lid := lid{
		db:         db,
		businessId: businessId,
		ch:         make(chan int64, len),
	}
	go lid.productId()
	return &lid, nil
}

// Get 获取自增id
func (l *lid) Get() int64 {
	return <-l.ch
}

// productId 生产id
func (l *lid) productId() {
	l.reset()
	for {
		if l.min >= l.max {
			l.reset()

		}

		l.min++
		l.ch <- l.min
	}
}

// reset 不断尝试从数据库获取，直到成功
func (l *lid) reset() {
	for {
		err := l.getFromDB()
		if err == nil {
			return
		}
		time.Sleep(time.Second)
		continue
	}
}

func (l *lid) getFromDB() error {
	var (
		max_id int64
		step   int64
		//idModel IdModel
		idModel utils.GenerateId
	)
	businessIdfilter := bson.M{utils.FN.GenerateId.BusinessId: l.businessId}
	txErr := Shop.Transaction(context.Background(), func(sctx mongo.SessionContext) (err error) {
		err = l.db.FindOneEx(sctx, &idModel, businessIdfilter)
		if err != nil {
			if err == mongo.ErrNoDocuments {
				idModel.MaxId = 10000
				_, err = l.db.InsertOne(sctx,
					bson.M{
						utils.FN.GenerateId.BusinessId: l.businessId,
						utils.FN.GenerateId.MaxId:      0,
						utils.FN.GenerateId.Step:       10,
						utils.FN.GenerateId.Desc:       "id自增器",
						utils.FN.GenerateId.CreateAt:   time.Now(),
						utils.FN.GenerateId.UpdateAt:   time.Now()})
				if err != nil {
					return
				}
			} else {
				return
			}
		}
		max_id = idModel.MaxId
		step = idModel.Step
		_, err = l.db.UpdateOne(sctx, businessIdfilter, bson.M{"$set": bson.M{utils.FN.GenerateId.MaxId: max_id + step}})
		if err != nil {
			return
		}
		l.min = max_id
		l.max = max_id + step
		return
	})
	return txErr
}