/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
 *
 *     http://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 org.apache.servicecomb.loadbalance.filterext;

import java.util.ArrayList;
import java.util.List;

import org.apache.servicecomb.core.Invocation;
import org.apache.servicecomb.loadbalance.ServerListFilterExt;
import org.apache.servicecomb.loadbalance.ServiceCombServer;
import org.apache.servicecomb.serviceregistry.RegistryUtils;
import org.apache.servicecomb.serviceregistry.api.registry.MicroserviceInstance;

import com.netflix.config.DynamicPropertyFactory;

public class ZoneAwareDiscoveryFilter implements ServerListFilterExt {

  @Override
  public int getOrder() {
    return ORDER_ZONE_AWARE;
  }

  @Override
  public boolean enabled() {
    return DynamicPropertyFactory.getInstance()
        .getBooleanProperty(ZONE_AWARE_FILTER_ENABLED, true)
        .get();
  }

  @Override
  public List<ServiceCombServer> getFilteredListOfServers(List<ServiceCombServer> servers,
      Invocation invocation) {
    MicroserviceInstance myself = RegistryUtils.getMicroserviceInstance();

    List<ServiceCombServer> instancesRegionAndAZMatch = new ArrayList<>();
    List<ServiceCombServer> instancesAZMatch = new ArrayList<>();
    List<ServiceCombServer> instancesNoMatch = new ArrayList<>();
    servers.forEach((server) -> {
      if (regionAndAZMatch(myself, server.getInstance())) {
        instancesRegionAndAZMatch.add(server);
      } else if (regionMatch(myself, server.getInstance())) {
        instancesAZMatch.add(server);
      } else {
        instancesNoMatch.add(server);
      }
    });
    if (!instancesRegionAndAZMatch.isEmpty()) {
      return instancesRegionAndAZMatch;
    } else if (!instancesAZMatch.isEmpty()) {
      return instancesAZMatch;
    }
    return instancesNoMatch;
  }

  private boolean regionAndAZMatch(MicroserviceInstance myself, MicroserviceInstance target) {
    if (myself == null || myself.getDataCenterInfo() == null) {
      // when instance have no datacenter info, it will match all other datacenters
      return true;
    }
    if (target.getDataCenterInfo() != null) {
      return myself.getDataCenterInfo().getRegion().equals(target.getDataCenterInfo().getRegion()) &&
          myself.getDataCenterInfo().getAvailableZone().equals(target.getDataCenterInfo().getAvailableZone());
    }
    return false;
  }

  private boolean regionMatch(MicroserviceInstance myself, MicroserviceInstance target) {
    if (target.getDataCenterInfo() != null) {
      return myself.getDataCenterInfo().getRegion().equals(target.getDataCenterInfo().getRegion());
    }
    return false;
  }
}
