/*
 * Copyright (c) 1999, 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 sun.security.ssl;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Locale;
import javax.net.ssl.SSLSession;
import javax.net.ssl.SSLSessionContext;

import sun.security.action.GetIntegerAction;
import sun.security.util.Cache;


final class SSLSessionContextImpl implements SSLSessionContext {
    private final static int DEFAULT_MAX_CACHE_SIZE = 20480;

    private final Cache<SessionId, SSLSessionImpl> sessionCache;
                                        // session cache, session id as key
    private final Cache<String, SSLSessionImpl> sessionHostPortCache;
                                        // session cache, "host:port" as key
    private int cacheLimit;             // the max cache size
    private int timeout;                // timeout in seconds

    // package private
    SSLSessionContextImpl() {
        cacheLimit = getDefaultCacheLimit();    // default cache size
        timeout = 86400;                        // default, 24 hours

        // use soft reference
        sessionCache = Cache.newSoftMemoryCache(cacheLimit, timeout);
        sessionHostPortCache = Cache.newSoftMemoryCache(cacheLimit, timeout);
    }

    
Returns the SSLSession bound to the specified session id.
/**
     * Returns the <code>SSLSession</code> bound to the specified session id.
     */
    @Override
    public SSLSession getSession(byte[] sessionId) {
        if (sessionId == null) {
            throw new NullPointerException("session id cannot be null");
        }

        SSLSessionImpl sess = sessionCache.get(new SessionId(sessionId));
        if (!isTimedout(sess)) {
            return sess;
        }

        return null;
    }

    
Returns an enumeration of the active SSL sessions.
/**
     * Returns an enumeration of the active SSL sessions.
     */
    @Override
    public Enumeration<byte[]> getIds() {
        SessionCacheVisitor scVisitor = new SessionCacheVisitor();
        sessionCache.accept(scVisitor);

        return scVisitor.getSessionIds();
    }

    
Sets the timeout limit for cached SSLSession objects
Note that after reset the timeout, the cached session before
should be timed within the shorter one of the old timeout and the
new timeout.
/**
     * Sets the timeout limit for cached <code>SSLSession</code> objects
     *
     * Note that after reset the timeout, the cached session before
     * should be timed within the shorter one of the old timeout and the
     * new timeout.
     */
    @Override
    public void setSessionTimeout(int seconds)
                 throws IllegalArgumentException {
        if (seconds < 0) {
            throw new IllegalArgumentException();
        }

        if (timeout != seconds) {
            sessionCache.setTimeout(seconds);
            sessionHostPortCache.setTimeout(seconds);
            timeout = seconds;
        }
    }

    
Gets the timeout limit for cached SSLSession objects
/**
     * Gets the timeout limit for cached <code>SSLSession</code> objects
     */
    @Override
    public int getSessionTimeout() {
        return timeout;
    }

    
Sets the size of the cache used for storing
SSLSession objects.
/**
     * Sets the size of the cache used for storing
     * <code>SSLSession</code> objects.
     */
    @Override
    public void setSessionCacheSize(int size)
                 throws IllegalArgumentException {
        if (size < 0)
            throw new IllegalArgumentException();

        if (cacheLimit != size) {
            sessionCache.setCapacity(size);
            sessionHostPortCache.setCapacity(size);
            cacheLimit = size;
        }
    }

    
Gets the size of the cache used for storing
SSLSession objects.
/**
     * Gets the size of the cache used for storing
     * <code>SSLSession</code> objects.
     */
    @Override
    public int getSessionCacheSize() {
        return cacheLimit;
    }

    // package-private method, used ONLY by ServerHandshaker
    SSLSessionImpl get(byte[] id) {
        return (SSLSessionImpl)getSession(id);
    }

    // package-private method, used ONLY by ClientHandshaker
    SSLSessionImpl get(String hostname, int port) {
        /*
         * If no session caching info is available, we won't
         * get one, so exit before doing a lookup.
         */
        if (hostname == null && port == -1) {
            return null;
        }

        SSLSessionImpl sess = sessionHostPortCache.get(getKey(hostname, port));
        if (!isTimedout(sess)) {
            return sess;
        }

        return null;
    }

    private static String getKey(String hostname, int port) {
        return (hostname + ":" +
            String.valueOf(port)).toLowerCase(Locale.ENGLISH);
    }

    // cache a SSLSession
    //
    // In SunJSSE implementation, a session is created while getting a
    // client hello or a server hello message, and cached while the
    // handshaking finished.
    // Here we time the session from the time it cached instead of the
    // time it created, which is a little longer than the expected. So
    // please do check isTimedout() while getting entry from the cache.
    void put(SSLSessionImpl s) {
        sessionCache.put(s.getSessionId(), s);

        // If no hostname/port info is available, don't add this one.
        if ((s.getPeerHost() != null) && (s.getPeerPort() != -1)) {
            sessionHostPortCache.put(
                getKey(s.getPeerHost(), s.getPeerPort()), s);
        }

        s.setContext(this);
    }

    // package-private method, remove a cached SSLSession
    void remove(SessionId key) {
        SSLSessionImpl s = sessionCache.get(key);
        if (s != null) {
            sessionCache.remove(key);
            sessionHostPortCache.remove(
                    getKey(s.getPeerHost(), s.getPeerPort()));
        }
    }

    private static int getDefaultCacheLimit() {
        try {
            int defaultCacheLimit = GetIntegerAction.privilegedGetProperty(
                    "javax.net.ssl.sessionCacheSize", DEFAULT_MAX_CACHE_SIZE);

            if (defaultCacheLimit >= 0) {
                return defaultCacheLimit;
            } else if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
                SSLLogger.warning(
                    "invalid System Property javax.net.ssl.sessionCacheSize, " +
                    "use the default session cache size (" +
                    DEFAULT_MAX_CACHE_SIZE + ") instead");
            }
        } catch (Exception e) {
            // unlikely, log it for safe
            if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
                SSLLogger.warning(
                    "the System Property javax.net.ssl.sessionCacheSize is " +
                    "not available, use the default value (" +
                    DEFAULT_MAX_CACHE_SIZE + ") instead");
            }
        }

        return DEFAULT_MAX_CACHE_SIZE;
    }

    private boolean isTimedout(SSLSession sess) {
        if (timeout == 0) {
            return false;
        }

        if ((sess != null) && ((sess.getCreationTime() + timeout * 1000L)
                                        <= (System.currentTimeMillis()))) {
            sess.invalidate();
            return true;
        }

        return false;
    }

    private final class SessionCacheVisitor
            implements Cache.CacheVisitor<SessionId, SSLSessionImpl> {
        ArrayList<byte[]> ids = null;

        // public void visit(java.util.Map<K,V> map) {}
        @Override
        public void visit(java.util.Map<SessionId, SSLSessionImpl> map) {
            ids = new ArrayList<>(map.size());

            for (SessionId key : map.keySet()) {
                SSLSessionImpl value = map.get(key);
                if (!isTimedout(value)) {
                    ids.add(key.getId());
                }
            }
        }

        Enumeration<byte[]> getSessionIds() {
            return  ids != null ? Collections.enumeration(ids) :
                                  Collections.emptyEnumeration();
        }
    }
}