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High-performance asynchronous HTTP client and server.
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/*
 * Copyright (C) 2015 SoftIndex LLC.
 *
 * 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
 *
 * 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 io.datakernel.dns;

import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;

import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.concurrent.Executor;

import static com.google.common.collect.Lists.newArrayList;

/**
 * SimpleDnsResolver is realization of the {@link BlockingDnsResolver}. For resolving domain it is used
 * java.net.* .
 */
public final class SimpleDnsResolver extends BlockingDnsResolver {
	public SimpleDnsResolver(Executor executor) {
		super(executor);
	}

	@Override
	protected ResolvedAddress doResolve(String host, final boolean ipv6) {
		ResolvedAddress resolvedAddress;
		try {
			InetAddress[] addresses = InetAddress.getAllByName(host);

			// remove unsolicited addresses
			ArrayList addressList = new ArrayList<>(Arrays.asList(addresses));
			ArrayList filteredAddresses = newArrayList(Iterables.filter(addressList, new Predicate() {
				@Override
				public boolean apply(InetAddress input) {
					if (ipv6) {
						return input instanceof Inet6Address;
					} else {
						return input instanceof Inet4Address;
					}
				}
			}));

			addresses = filteredAddresses.toArray(new InetAddress[filteredAddresses.size()]);

			resolvedAddress = new ResolvedAddress(addresses, positiveKeepMillis);
		} catch (Exception e) {
			if (logger.isWarnEnabled()) {
				logger.warn("Failed to resolve address by host name {}: {}", host, e);
			}
			return new ResolvedAddress(null, negativeKeepMillis);
		}
		if (logger.isDebugEnabled()) {
			logger.debug("Resolved addresses: {} for host: {}", resolvedAddress.getAllAddresses(), host);
		}
		return resolvedAddress;
	}
}