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package com.iailab.framework.env.core.fegin;
 
import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.util.StrUtil;
import com.iailab.framework.common.util.collection.CollectionUtils;
import com.iailab.framework.env.core.context.EnvContextHolder;
import com.iailab.framework.env.core.util.EnvUtils;
import com.alibaba.cloud.nacos.balancer.NacosBalancer;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.DefaultResponse;
import org.springframework.cloud.client.loadbalancer.EmptyResponse;
import org.springframework.cloud.client.loadbalancer.Request;
import org.springframework.cloud.client.loadbalancer.Response;
import org.springframework.cloud.client.loadbalancer.reactive.ReactiveLoadBalancer;
import org.springframework.cloud.loadbalancer.core.NoopServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import reactor.core.publisher.Mono;
 
import java.util.List;
 
/**
 * 多环境的 {@link org.springframework.cloud.client.loadbalancer.LoadBalancerClient} 实现类
 * 在从服务实例列表选择时，优先选择 tag 匹配的服务实例
 *
 * @author iailab
 */
@RequiredArgsConstructor
@Slf4j
public class EnvLoadBalancerClient implements ReactorServiceInstanceLoadBalancer {
 
    /**
     * 用于获取 serviceId 对应的服务实例的列表
     */
    private final ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
    /**
     * 需要获取的服务实例名
     *
     * 暂时用于打印 logger 日志
     */
    private final String serviceId;
    /**
     * 被代理的 ReactiveLoadBalancer 对象
     */
    private final ReactiveLoadBalancer<ServiceInstance> reactiveLoadBalancer;
 
    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        // 情况一，没有 tag 时，使用默认的 reactiveLoadBalancer 实现负载均衡
        String tag = EnvContextHolder.getTag();
        if (StrUtil.isEmpty(tag)) {
            return Mono.from(reactiveLoadBalancer.choose(request));
        }
 
        // 情况二，有 tag 时，使用 tag 匹配服务实例
        ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new);
        return supplier.get(request).next().map(list -> getInstanceResponse(list, tag));
    }
 
    private Response<ServiceInstance> getInstanceResponse(List<ServiceInstance> instances, String tag) {
        // 如果服务实例为空，则直接返回
        if (CollUtil.isEmpty(instances)) {
            log.warn("[getInstanceResponse][serviceId({}) 服务实例列表为空]", serviceId);
            return new EmptyResponse();
        }
 
        // 筛选满足条件的实例列表
        List<ServiceInstance> chooseInstances = CollectionUtils.filterList(instances, instance -> tag.equals(EnvUtils.getTag(instance)));
        if (CollUtil.isEmpty(chooseInstances)) {
            log.warn("[getInstanceResponse][serviceId({}) 没有满足 tag({}) 的服务实例列表，直接使用所有服务实例列表]", serviceId, tag);
            chooseInstances = instances;
        }
 
        // TODO iailab：https://juejin.cn/post/7056770721858469896 想通网段
 
        // 随机 + 权重获取实例列表 TODO iailab：目前直接使用 Nacos 提供的方法，如果替换注册中心，需要重新失败该方法
        return new DefaultResponse(NacosBalancer.getHostByRandomWeight3(chooseInstances));
    }
 
}