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/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2017 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * 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 org.wildfly.common.net;

import static java.security.AccessController.doPrivileged;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.PrivilegedAction;
import java.util.regex.Pattern;

import org.wildfly.common.Assert;

/**
 * Methods for getting the system host name.  The host name is detected from the environment, but may be overridden by
 * use of the {@code jboss.host.name} and/or {@code jboss.qualified.host.name} system properties.
 *
 * @author David M. Lloyd
 */
public final class HostName {

    private static final Object lock = new Object();
    private static volatile String hostName;
    private static volatile String qualifiedHostName;
    private static volatile String nodeName;

    static {
        String[] names = doPrivileged((PrivilegedAction) () -> {
            // allow host name to be overridden
            String qualifiedHostName = System.getProperty("jboss.qualified.host.name");
            String providedHostName = System.getProperty("jboss.host.name");
            String providedNodeName = System.getProperty("jboss.node.name");
            if (qualifiedHostName == null) {
                // if host name is specified, don't pick a qualified host name that isn't related to it
                qualifiedHostName = providedHostName;
                if (qualifiedHostName == null) {
                    // POSIX-like OSes including Mac should have this set
                    qualifiedHostName = System.getenv("HOSTNAME");
                }
                if (qualifiedHostName == null) {
                    // Certain versions of Windows
                    qualifiedHostName = System.getenv("COMPUTERNAME");
                }
                if (qualifiedHostName == null) {
                    try {
                        qualifiedHostName = getLocalHost().getHostName();
                    } catch (UnknownHostException e) {
                        qualifiedHostName = null;
                    }
                }
                if (qualifiedHostName != null && Pattern.compile("^\\d+\\.\\d+\\.\\d+\\.\\d+$|:").matcher(qualifiedHostName).find()) {
                    // IP address is not acceptable
                    qualifiedHostName = null;
                }
                if (qualifiedHostName == null) {
                    // Give up
                    qualifiedHostName = "unknown-host.unknown-domain";
                } else {
                    qualifiedHostName = qualifiedHostName.trim().toLowerCase();
                }
            }
            if (providedHostName == null) {
                // Use the host part of the qualified host name
                final int idx = qualifiedHostName.indexOf('.');
                providedHostName  = idx == -1 ? qualifiedHostName : qualifiedHostName.substring(0, idx);
            }
            if (providedNodeName == null) {
                providedNodeName = providedHostName;
            }
            return new String[] {
                providedHostName,
                qualifiedHostName,
                providedNodeName
            };
        });
        hostName = names[0];
        qualifiedHostName = names[1];
        nodeName = names[2];
    }

    private HostName() {
    }

    static InetAddress getLocalHost() throws UnknownHostException {
        InetAddress addr;
        try {
            addr = InetAddress.getLocalHost();
        } catch (ArrayIndexOutOfBoundsException e) {  //this is workaround for mac osx bug see AS7-3223 and JGRP-1404
            addr = InetAddress.getByName(null);
        }
        return addr;
    }

    /**
     * Get the detected host name.
     *
     * @return the detected host name
     */
    public static String getHostName() {
        return hostName;
    }

    /**
     * Get the detected qualified host name.
     *
     * @return the detected qualified host name
     */
    public static String getQualifiedHostName() {
        return qualifiedHostName;
    }

    /**
     * Get the node name.
     *
     * @return the node name
     */
    public static String getNodeName() {
        return nodeName;
    }

    /**
     * Set the host name.  The qualified host name is set directly from the given value; the unqualified host name
     * is then re-derived from that value.  The node name is not changed by this method.
     *
     * @param qualifiedHostName the host name
     */
    public static void setQualifiedHostName(final String qualifiedHostName) {
        Assert.checkNotNullParam("qualifiedHostName", qualifiedHostName);
        synchronized (lock) {
            HostName.qualifiedHostName = qualifiedHostName;
            // Use the host part of the qualified host name
            final int idx = qualifiedHostName.indexOf('.');
            HostName.hostName = idx == -1 ? qualifiedHostName : qualifiedHostName.substring(0, idx);
        }
    }

    /**
     * Set the node name.
     *
     * @param nodeName the node name
     */
    public static void setNodeName(final String nodeName) {
        Assert.checkNotNullParam("nodeName", nodeName);
        HostName.nodeName = nodeName;
    }
}