/*

 * Copyright (c) 2005, 2018, 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.  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 java.io;

import java.util.*;

import jdk.internal.access.SharedSecrets;

/**

 * This class holds a set of filenames to be deleted on VM exit through a shutdown hook.

 * A set is used both to prevent double-insertion of the same file as well as offer

 * quick removal.

 */

class DeleteOnExitHook {

    private static LinkedHashSet<String> files = new LinkedHashSet<>();

    static {

        // DeleteOnExitHook must be the last shutdown hook to be invoked.

        // Application shutdown hooks may add the first file to the

        // delete on exit list and cause the DeleteOnExitHook to be

        // registered during shutdown in progress. So set the

        // registerShutdownInProgress parameter to true.

        SharedSecrets.getJavaLangAccess()

            .registerShutdownHook(2 /* Shutdown hook invocation order */,

                true /* register even if shutdown in progress */,

                new Runnable() {

                    public void run() {

                       runHooks();

                    }

                }

        );

    }

    private DeleteOnExitHook() {}

    static synchronized void add(String file) {

        if(files == null) {

            // DeleteOnExitHook is running. Too late to add a file

            throw new IllegalStateException("Shutdown in progress");

        }

        files.add(file);

    }

    static void runHooks() {

        LinkedHashSet<String> theFiles;

        synchronized (DeleteOnExitHook.class) {

            theFiles = files;

            files = null;

        }

        ArrayList<String> toBeDeleted = new ArrayList<>(theFiles);

        // reverse the list to maintain previous jdk deletion order.

        // Last in first deleted.

        Collections.reverse(toBeDeleted);

        for (String filename : toBeDeleted) {

            (new File(filename)).delete();

        }

    }

}