package foo;

import io.grpc.Attributes;
import io.grpc.EquivalentAddressGroup;
import io.grpc.NameResolver;
import io.grpc.NameResolverProvider;
import java.net.InetSocketAddress;
import java.net.URI;
import java.util.List;
import java.util.stream.Collectors;
import javax.annotation.Nullable;

public class StaticServerNameResolverFactory extends NameResolverProvider {

  private final String scheme;
  private final String authority;
  private final List<EquivalentAddressGroup> servers;

  public StaticServerNameResolverFactory(String scheme, String authority, List<String> servers) {
    this.scheme = scheme;
    this.authority = authority;
    this.servers = servers.stream()
        .map(server -> {
          URI uri = URI.create(scheme + "://" + server);
          return new EquivalentAddressGroup(InetSocketAddress.createUnresolved(uri.getHost(), uri.getPort()));
        })
        .collect(Collectors.toList());
  }

  @Nullable
  @Override
  public NameResolver newNameResolver(URI targetUri, Attributes params) {
    return new NameResolver() {
      @Override
      public String getServiceAuthority() {
        return authority;
      }

      @Override
      public void start(Listener listener) {
        // nothing to do
        listener.onAddresses(servers, Attributes.EMPTY);
      }

      @Override
      public void shutdown() {
        // nothing to do
      }
    };
  }

  @Override
  public String getDefaultScheme() {
    return scheme;
  }

  @Override
  protected boolean isAvailable() {
    return true;
  }

  @Override
  protected int priority() {
    return 0;
  }
}