package discover

import (
	"net/http"
	"time"
)

// SetLoadBalancer 设置全局负载均衡策略
func SetLoadBalancer(lb LoadBalancer) {
	settedLoadBalancer = lb
}

// LoadBalancer 负载均衡接口
type LoadBalancer interface {
	// Response 在每个请求完成后调用，用于更新节点状态
	Response(appClient *AppClient, node *NodeInfo, err error, response *http.Response, responseTime time.Duration)

	// Next 根据当前可用节点选择一个最优节点
	Next(appClient *AppClient, nodes []*NodeInfo, request *http.Request) *NodeInfo
}

// DefaultLoadBalancer 默认负载均衡器（简单权重轮询/得分最小者优先）
type DefaultLoadBalancer struct{}

func (lb *DefaultLoadBalancer) Response(appClient *AppClient, node *NodeInfo, err error, response *http.Response, responseTime time.Duration) {
	node.Data.Store("score", float64(node.UsedTimes)/float64(node.Weight))
}

func (lb *DefaultLoadBalancer) Next(appClient *AppClient, nodes []*NodeInfo, request *http.Request) *NodeInfo {
	var minScore float64 = -1
	var minNode *NodeInfo
	for _, node := range nodes {
		scoreValue, ok := node.Data.Load("score")
		if !ok {
			scoreValue = float64(node.UsedTimes) / float64(node.Weight)
			node.Data.Store("score", scoreValue)
		}
		score := scoreValue.(float64)
		if minNode == nil || score < minScore {
			minScore = score
			minNode = node
		}
	}
	return minNode
}