package service_base

import (
	"app/internal/msg_inner"
	"core/tools"
	"time"
)

type LB_TYPE int32

const (
	LBTypeNone LB_TYPE = iota
	LBTypeFrontend
	LBTypeBackend
)
const (
	CHECK_ALIVE_RETRY_MAX            = 3  //被动检测存活 重试次数
	FRONTEND_CHECKALIVE_INTERVAL     = 30 //前端检测存活的间隔 秒
	FRONTEND_ROUTER_REFRESH_INTERVAL = 60 //前端路由刷新时间 秒
	BAKCEND_REPORT_INTERVAL          = 30 //后端主动上报的间隔 秒
)

func NewLoadBalanceManager() ILoadBalanceManager {
	return &LoadBalanceManager{
		backendMap: make(map[string]*LoadBalanceNode),
	}
}

var _ ILoadBalanceManager = (*LoadBalanceManager)(nil) //interface实现检查
type ILoadBalanceManager interface {
	Init(serviceBase IServiceBase) ILoadBalanceManager
	StartAsFrontend()                     //作为前端启动
	StartAsBackend(frontendAppId string)  //作为后端启动
	GetBestBackend() (addr, appId string) //获得路由后的后端地址 目前策略：根据后端上报的rank选择最优
}
type LoadBalanceManager struct {
	serviceBase      IServiceBase
	frontendAppId    string
	bestBackendAppId string
	backendMap       map[string]*LoadBalanceNode
	lbType           LB_TYPE
}

type LoadBalanceNode struct {
	appId   string
	address string
	rank    float64
	isAlive bool
}

func (s *LoadBalanceManager) Init(serviceBase IServiceBase) ILoadBalanceManager {
	s.serviceBase = serviceBase
	s.initAPI()
	return s
}

func (s *LoadBalanceManager) StartAsFrontend() {
	tools.AssertTrue(s.lbType == LBTypeNone, "StartAsFrontend fail, lbType is not LBTypeNone")
	s.lbType = LBTypeFrontend
	act := s.serviceBase.Actor()
	act.AddTimer(time.Second*FRONTEND_CHECKALIVE_INTERVAL, -1, func(dt int64) {
		for _, node := range s.backendMap {
			var timerId int64
			retry := CHECK_ALIVE_RETRY_MAX
			act.Send(act.Id(), func() {
				timerId = act.AddTimer(time.Second, -1, func(dt int64) {
					if _, err := act.RequestWait(node.appId, &msg_inner.CheckAlive{}); err == nil {
						act.CancelTimer(timerId)
						node.isAlive = true
					} else {
						retry--
						if retry < 0 {
							act.CancelTimer(timerId)
							node.isAlive = false
						}
					}
				})
			})
		}
	})
	act.AddTimer(time.Second*FRONTEND_ROUTER_REFRESH_INTERVAL, -1, func(dt int64) {
		if len(s.backendMap) == 0 {
			return
		}
		var bestAppId string
		var bestRank float64
		for _, node := range s.backendMap {
			if bestAppId == "" || node.rank < bestRank {
				bestAppId = node.appId
				bestRank = node.rank
			}
		}
		s.bestBackendAppId = bestAppId
	})
}

func (s *LoadBalanceManager) StartAsBackend(frontendAppId string) {
	tools.AssertTrue(s.lbType == LBTypeNone, "StartAsFrontend fail, lbType is not LBTypeNone")
	s.lbType = LBTypeBackend
	s.frontendAppId = frontendAppId
	var addr string
	if s.serviceBase.Config().Has("client_addr") {
		_, port := tools.AddressSplit(s.serviceBase.Config().String("client_addr"))
		addr = tools.AddressMerge(tools.GetOutboundIP().String(), port)
	}
	act := s.serviceBase.Actor()
	act.AddTimer(time.Second*BAKCEND_REPORT_INTERVAL, -1, func(dt int64) {
		act.Send(s.frontendAppId, &msg_inner.LoadBalanceReport{
			Rank:    0,
			Address: addr,
		})
	})
}

func (s *LoadBalanceManager) GetBestBackend() (addr, appId string) {
	tools.AssertTrue(s.lbType == LBTypeFrontend, "GetBestBackend fail, lbType is not LBTypeFrontend")
	if node, ok := s.backendMap[s.bestBackendAppId]; ok {
		addr, appId = node.address, node.appId
	}
	return
}