/*

 * Portions Copyright 2000-2006 Sun Microsystems, Inc.  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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5.internal.rcache;

import sun.security.krb5.KrbException;

import sun.security.krb5.Config;

import sun.security.krb5.internal.Krb5;

import java.util.LinkedList;

import java.util.ListIterator;

import sun.security.krb5.internal.KerberosTime;

/**

 * This class provides an efficient caching mechanism to store the timestamp of client authenticators.

 * The cache minimizes the memory usage by doing self-cleanup of expired items in the cache.

 *

 * @author Yanni Zhang

 */

public class ReplayCache extends LinkedList<AuthTime> {

    private static final long serialVersionUID = 2997933194993803994L;

    private String principal;

    private CacheTable table;

    private int nap = 10 * 60 * 1000; //10 minutes break

    private boolean DEBUG = Krb5.DEBUG;

    /**

     * Constructs a ReplayCache for a client principal in specified <code>CacheTable</code>.

     * @param p client principal name.

     * @param ct CacheTable.

     */

    public ReplayCache (String p, CacheTable ct) {

        principal = p;

        table = ct;

    }

    /**

     * Puts the authenticator timestamp into the cache in descending order.

     * @param t <code>AuthTime</code>

     */

    public synchronized void put(AuthTime t, long currentTime) {

        if (this.size() == 0) {

            addFirst(t);

        }

        else {

            AuthTime temp = getFirst();

            if (temp.kerberosTime < t.kerberosTime) {

                // in most cases, newly received authenticator has

                // larger timestamp.

                addFirst(t);

            }

            else if (temp.kerberosTime == t.kerberosTime) {

                if (temp.cusec < t.cusec) {

                    addFirst(t);

                }

            }

            else {

                //unless client clock being re-adjusted.

                ListIterator<AuthTime> it = listIterator(1);

                while (it.hasNext()) {

                    temp = it.next();

                    if (temp.kerberosTime < t.kerberosTime) {

                        add(indexOf(temp), t);

                        break;

                        //we always put the bigger timestamp at the front.

                    }

                    else if (temp.kerberosTime == t.kerberosTime) {

                        if (temp.cusec < t.cusec) {

                            add(indexOf(temp), t);

                            break;

                        }

                    }

                }

            }

        }

        // let us cleanup while we are here

        long timeLimit = currentTime - KerberosTime.getDefaultSkew() * 1000L;

        ListIterator<AuthTime> it = listIterator(0);

        AuthTime temp = null;

        int index = -1;

        while (it.hasNext()) {

            //search expired timestamps.

            temp = it.next();

            if (temp.kerberosTime < timeLimit) {

                index = indexOf(temp);

                break;

            }

        }

        if (index > -1) {

            do {

                //remove expired timestamps from the list.

                removeLast();

            } while(size() > index);

        }

        if (DEBUG) {

            printList();

        }

        // if there are no entries in the replay cache,

        // remove the replay cache from the table.

        if (this.size() == 0) {

            table.remove(principal);

        }

        if (DEBUG) {

            printList();

        }

    }

    /**

     * Printes out the debug message.

     */

    private void printList() {

        Object[] total = toArray();

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

            System.out.println("object " + i + ": " + ((AuthTime)total[i]).kerberosTime + "/"

                               + ((AuthTime)total[i]).cusec);

        }

    }

}