/*
 * Copyright (c) 2015, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */
package org.graalvm.compiler.test;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.Arrays;
import java.util.List;

Utility methods for spawning a VM in a subprocess during unit tests.
/**
 * Utility methods for spawning a VM in a subprocess during unit tests.
 */
public final class SubprocessUtil {

    private SubprocessUtil() {
    }

    
Gets the command line for the current process.
Returns:
the command line arguments for the current process or null if they are not available/**
     * Gets the command line for the current process.
     *
     * @return the command line arguments for the current process or {@code null} if they are not
     *         available
     */
    public static List<String> getProcessCommandLine() {
        String processArgsFile = System.getenv().get("MX_SUBPROCESS_COMMAND_FILE");
        if (processArgsFile != null) {
            try {
                return Files.readAllLines(new File(processArgsFile).toPath());
            } catch (IOException e) {
            }
        }
        return null;
    }

    
Gets the command line used to start the current Java VM, including all VM arguments, but not
including the main class or any Java arguments. This can be used to spawn an identical VM,
but running different Java code.
/**
     * Gets the command line used to start the current Java VM, including all VM arguments, but not
     * including the main class or any Java arguments. This can be used to spawn an identical VM,
     * but running different Java code.
     */
    public static List<String> getVMCommandLine() {
        List<String> args = getProcessCommandLine();
        if (args == null) {
            return null;
        } else {
            int index = findMainClassIndex(args);
            return args.subList(0, index);
        }
    }

    public static final List<String> JVM_OPTIONS_WITH_ONE_ARG = System.getProperty("java.specification.version").compareTo("1.9") < 0 ? //
                    Arrays.asList("-cp", "-classpath") : //
                    Arrays.asList("-cp", "-classpath", "-mp", "-modulepath", "-upgrademodulepath", "-addmods", "-m", "-limitmods");

    private static int findMainClassIndex(List<String> commandLine) {
        int i = 1; // Skip the java executable

        while (i < commandLine.size()) {
            String s = commandLine.get(i);
            if (s.charAt(0) != '-') {
                return i;
            } else if (JVM_OPTIONS_WITH_ONE_ARG.contains(s)) {
                i += 2;
            } else {
                i++;
            }
        }
        throw new InternalError();
    }

}