// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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 com.google.devtools.build.lib.util;

import java.net.InetAddress;
import java.net.UnknownHostException;

/**
 * Various utility methods for network related stuff.
 */
public final class NetUtil {

  private static String hostname;

  private NetUtil() {
  }

  /**
   * Returns the *cached* short hostname (computed at most once per the lifetime of a server). Can
   * take seconds to complete when the cache is cold.
   */
  public static String getCachedShortHostName() {
    if (hostname == null) {
      synchronized (NetUtil.class) {
        if (hostname == null) {
          hostname = computeShortHostName();
        }
      }
    }
    return hostname;
  }

  /**
   * Returns the short hostname or <code>unknown</code> if the host name could not be determined.
   * Performs reverse DNS lookup and can take seconds to complete.
   */
  private static String computeShortHostName() {
    try {
      return InetAddress.getLocalHost().getHostName();
    } catch (UnknownHostException e) {
      return "unknown";
    }
  }
}

@@ -653,16 +653,208 @@
 .util;%0A%0A
+import static com.google.common.base.MoreObjects.firstNonNull;%0Aimport static com.google.common.base.Preconditions.checkNotNull;%0Aimport static com.google.common.base.Preconditions.checkState;%0A%0A
 import j
@@ -911,16 +911,52 @@
 ception;
+%0Aimport java.util.function.Supplier;
 %0A%0A/**%0A *
@@ -1073,16 +1073,107 @@
 hostname
+ = null;%0A  private static Supplier%3CString%3E hostnameSupplier = NetUtil::computeShortHostName
 ;%0A%0A  pri
@@ -1188,19 +1188,16 @@
 Util() %7B
-%0A  
 %7D%0A%0A  /**
@@ -1524,23 +1524,234 @@
 tname = 
-compute
+firstNonNull(hostnameSupplier.get(), %22unknown%22);%0A          hostnameSupplier = null;%0A        %7D%0A      %7D%0A    %7D%0A    return hostname;%0A  %7D%0A%0A  /**%0A   * Sets a %7B@link Supplier%7D for the hostname to return from %7B@link #getCached
 ShortHos
@@ -1759,55 +1759,456 @@
 Name
-();
+%7D.
 %0A   
+*%0A
    
-  %7D%0A      %7D%0A    %7D%0A    return hostname
+* %3Cp%3EIf not called, the hostname comes from %7B@link #computeShortHostName%7D. To prevent multiple%0A   * different hostnames from being used, it is illegal to call this after %7B@link%0A   * #getCachedShortHostName%7D has been called.%0A   */%0A  public static synchronized void overrideHostnameSupplier(Supplier%3CString%3E override) %7B%0A    checkState(hostname == null, %22Hostname already set to %25s%22, hostname);%0A    hostnameSupplier = checkNotNull(override)
 ;%0A  

Allow overriding the methodology of determining the hostname.