content: /*
   * Copyright 2013-2023 the original author or authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.alibaba.cloud.nacos.loadbalancer;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import java.util.regex.Pattern;
  import java.util.stream.Collectors;
  
  import com.alibaba.cloud.commons.lang.StringUtils;
  import com.alibaba.cloud.nacos.NacosDiscoveryProperties;
  import com.alibaba.cloud.nacos.util.InetIPv6Utils;
  import com.alibaba.nacos.client.naming.utils.CollectionUtils;
  import jakarta.annotation.PostConstruct;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import reactor.core.publisher.Mono;
  
  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.loadbalancer.core.NoopServiceInstanceListSupplier;
  import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;
  import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
  
  /**
   * see original.
   * {@link org.springframework.cloud.loadbalancer.core.RoundRobinLoadBalancer}
   *
   * @author XuDaojie
   * @since 2021.1
   */
  public class NacosLoadBalancer implements ReactorServiceInstanceLoadBalancer {
  
  	private static final Logger log = LoggerFactory.getLogger(NacosLoadBalancer.class);
  
  	private final String serviceId;
  
  	private final ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
  
  	private final NacosDiscoveryProperties nacosDiscoveryProperties;
  
  	private static final String IPV4_REGEX = "((2(5[0-5]|[0-4]\\d))|[0-1]?\\d{1,2})(.((2(5[0-5]|[0-4]\\d))|[0-1]?\\d{1,2})){3}";
  
  	private static final String IPV6_KEY = "IPv6";
  	/**
  	 * Storage local valid IPv6 address, it's a flag whether local machine support IPv6 address stack.
  	 */
  	public static String ipv6;
  
  	private final InetIPv6Utils inetIPv6Utils;
  
  	private final List<ServiceInstanceFilter> serviceInstanceFilters;
  
  	private final Map<String, LoadBalancerAlgorithm> loadBalancerAlgorithmMap;
  
  	@PostConstruct
  	public void init() {
  		String ip = nacosDiscoveryProperties.getIp();
  		if (StringUtils.isNotEmpty(ip)) {
  			ipv6 = Pattern.matches(IPV4_REGEX, ip) ? nacosDiscoveryProperties.getMetadata().get(IPV6_KEY) : ip;
  		}
  		else {
  			ipv6 = inetIPv6Utils.findIPv6Address();
  		}
  	}
  
  	private List<ServiceInstance> filterInstanceByIpType(List<ServiceInstance> instances) {
  		if (StringUtils.isNotEmpty(ipv6)) {
  			List<ServiceInstance> ipv6InstanceList = new ArrayList<>();
  			for (ServiceInstance instance : instances) {
  				if (Pattern.matches(IPV4_REGEX, instance.getHost())) {
  					if (StringUtils.isNotEmpty(instance.getMetadata().get(IPV6_KEY))) {
  						ipv6InstanceList.add(instance);
  					}
  				}
  				else {
  					ipv6InstanceList.add(instance);
  				}
  			}
  			// Provider has no IPv6, should use IPv4.
  			if (ipv6InstanceList.isEmpty()) {
  				return instances.stream()
  						.filter(instance -> Pattern.matches(IPV4_REGEX, instance.getHost()))
  						.collect(Collectors.toList());
  			}
  			else {
  				return ipv6InstanceList;
  			}
  		}
  		return instances.stream()
  				.filter(instance -> Pattern.matches(IPV4_REGEX, instance.getHost()))
  				.collect(Collectors.toList());
  	}
  
  	public NacosLoadBalancer(
  			ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider,
  			String serviceId, NacosDiscoveryProperties nacosDiscoveryProperties, InetIPv6Utils inetIPv6Utils,
  			List<ServiceInstanceFilter> serviceInstanceFilters,
  			Map<String, LoadBalancerAlgorithm> loadBalancerAlgorithmMap) {
  		this.serviceId = serviceId;
  		this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
  		this.nacosDiscoveryProperties = nacosDiscoveryProperties;
  		this.inetIPv6Utils = inetIPv6Utils;
  		this.serviceInstanceFilters = serviceInstanceFilters;
  		this.loadBalancerAlgorithmMap = loadBalancerAlgorithmMap;
  	}
  
  	@Override
  	public Mono<Response<ServiceInstance>> choose(Request request) {
  		ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider
  				.getIfAvailable(NoopServiceInstanceListSupplier::new);
  		return supplier.get(request).next().map(serviceInstances -> getInstanceResponse(request, serviceInstances));
  	}
  
  	private Response<ServiceInstance> getInstanceResponse(Request<?> request,
  			List<ServiceInstance> serviceInstances) {
  		if (serviceInstances.isEmpty()) {
  			log.warn("No servers available for service: {}", this.serviceId);
  			return new EmptyResponse();
  		}
  
  		try {
  			String clusterName = this.nacosDiscoveryProperties.getClusterName();
  
  			List<ServiceInstance> instancesToChoose = serviceInstances;
  			if (StringUtils.isNotBlank(clusterName)) {
  				List<ServiceInstance> sameClusterInstances = serviceInstances.stream()
  						.filter(serviceInstance -> {
  							String cluster = serviceInstance.getMetadata()
  									.get("nacos.cluster");
  							return StringUtils.equals(cluster, clusterName);
  						}).collect(Collectors.toList());
  				if (!CollectionUtils.isEmpty(sameClusterInstances)) {
  					instancesToChoose = sameClusterInstances;
  				}
  			}
  			else {
  				log.warn(
  						"A cross-cluster call occurs，name = {}, clusterName = {}, instance = {}",
  						serviceId, clusterName, serviceInstances);
  			}
  			instancesToChoose = this.filterInstanceByIpType(instancesToChoose);
  
  			// Filter the service list sequentially based on the order number
  			for (ServiceInstanceFilter filter : serviceInstanceFilters) {
  				instancesToChoose = filter.filterInstance(request, instancesToChoose);
  			}
  
  			ServiceInstance instance;
  			// Find the corresponding load balancing algorithm through the service ID and select the final service instance
  			if (loadBalancerAlgorithmMap.containsKey(serviceId)) {
  				instance = loadBalancerAlgorithmMap.get(serviceId).getInstance(request, instancesToChoose);
  			}
  			else {
  				instance = loadBalancerAlgorithmMap.get(LoadBalancerAlgorithm.DEFAULT_SERVICE_ID)
  						.getInstance(request, instancesToChoose);
  			}
  
  			return new DefaultResponse(instance);
  		}
  		catch (Exception e) {
  			log.warn("NacosLoadBalancer error", e);
  			return null;
  		}
  	}
  
  }
  