/*
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.graal.test;

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

/**
 * 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.
     *
     * @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.
     */
    public static List<String> getVMCommandLine() {
        List<String> args = getProcessCommandLine();
        if (args == null) {
            return null;
        } else {
            int index = findMainClassIndex(args);
            return args.subList(0, index);
        }
    }

    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 (s.equals("-cp") || s.equals("-classpath")) {
                i += 2;
            } else {
                i++;
            }
        }
        throw new InternalError();
    }

}