package com.aps.gateway.config.loadBalancer;
import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.map.MapUtil;
import cn.hutool.core.util.RandomUtil;
import cn.hutool.core.util.StrUtil;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.apache.logging.log4j.util.Strings;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.gateway.support.NotFoundException;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.stream.Collectors;

@Slf4j
@RequiredArgsConstructor
@Component
public class VersionGrayLoadBalancer implements GrayLoadBalancer {

    private final DiscoveryClient discoveryClient;
    private final static String VERSION = "local";
    /**
     * 根据serviceId 筛选可用服务
     * @param serviceId 服务ID
     * @param request 当前请求
     * @return ServiceInstance
     */
    @Override
    public ServiceInstance choose(String serviceId, ServerHttpRequest request) {
        List<ServiceInstance> instances = discoveryClient.getInstances(serviceId);

        // 注册中心无实例 抛出异常
        if (instances.isEmpty()) {
            log.warn("No instance available for {}", serviceId);
            throw new NotFoundException("No instance available for " + serviceId);
        }

        // 获取请求version，无则随机返回可用实例
        String reqVersion = request.getHeaders().getFirst(VERSION);
        if (Strings.isBlank(reqVersion)) {
            return instances.get(RandomUtil.randomInt(instances.size()));
        }

        // 遍历可以实例元数据，若匹配则返回此实例
        List<ServiceInstance> availableList = instances.stream()
                .filter(instance -> reqVersion
                        .equalsIgnoreCase(MapUtil.getStr(instance.getMetadata(), VERSION)))
                .collect(Collectors.toList());

        if (CollUtil.isEmpty(availableList)) {
            return instances.get(RandomUtil.randomInt(instances.size()));
        }
        return availableList.get(RandomUtil.randomInt(availableList.size()));

    }
}