/*

 * 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.sun.jndi.ldap;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLClassLoader;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

public final class VersionHelper {

    private static final VersionHelper helper = new VersionHelper();

    /**

     * Determines whether classes may be loaded from an arbitrary URL code base.

     */

    private static final boolean trustURLCodebase;

    static {

        // System property to control whether classes may be loaded from an

        // arbitrary URL code base

        PrivilegedAction<String> act =

                () -> System.getProperty("com.sun.jndi.ldap.object.trustURLCodebase", "false");

        String trust = AccessController.doPrivileged(act);

        trustURLCodebase = "true".equalsIgnoreCase(trust);

    }

    private VersionHelper() { }

    static VersionHelper getVersionHelper() {

        return helper;

    }

    ClassLoader getURLClassLoader(String[] url) throws MalformedURLException {

        ClassLoader parent = getContextClassLoader();

        /*

         * Classes may only be loaded from an arbitrary URL code base when

         * the system property com.sun.jndi.ldap.object.trustURLCodebase

         * has been set to "true".

         */

        if (url != null && trustURLCodebase) {

            return URLClassLoader.newInstance(getUrlArray(url), parent);

        } else {

            return parent;

        }

    }

    Class<?> loadClass(String className) throws ClassNotFoundException {

        return Class.forName(className, true, getContextClassLoader());

    }

    Thread createThread(Runnable r) {

        AccessControlContext acc = AccessController.getContext();

        // 4290486: doPrivileged is needed to create a thread in

        // an environment that restricts "modifyThreadGroup".

        PrivilegedAction<Thread> act =

                () -> SharedSecrets.getJavaLangAccess().newThreadWithAcc(r, acc);

        return AccessController.doPrivileged(act);

    }

    private ClassLoader getContextClassLoader() {

        PrivilegedAction<ClassLoader> act =

                Thread.currentThread()::getContextClassLoader;

        return AccessController.doPrivileged(act);

    }

    private static URL[] getUrlArray(String[] url) throws MalformedURLException {

        URL[] urlArray = new URL[url.length];

        for (int i = 0; i < urlArray.length; i++) {

            urlArray[i] = new URL(url[i]);

        }

        return urlArray;

    }

}