package org.apache.turbine.services.session;


/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */


import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import javax.servlet.http.HttpSession;

import org.apache.turbine.om.security.User;
import org.apache.turbine.services.TurbineBaseService;

/**
 * The SessionService allows thread-safe access to the current
 * sessions of the current context.  The session objects that are
 * cached by this service are obtained through a listener, which must
 * be configured via your web application's <code>web.xml</code>
 * deployment descriptor as follows:
 *
 * <pre>
 * &lt;listener&gt;
 *   &lt;listener-class&gt;
 *     org.apache.turbine.session.SessionListener
 *   &lt;/listener-class&gt;
 * &lt;/listener&gt;
 * </pre>
 *
 * @author <a href="mailto:quintonm@bellsouth.net">Quinton McCombs</a>
 * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
 * @since 2.3
 * @version $Id$
 * @see org.apache.turbine.services.session.SessionListener
 */
public class TurbineSessionService
        extends TurbineBaseService
        implements SessionService
{
    /** Map of active sessions */
    private ConcurrentMap<String, HttpSession> activeSessions;

    /**
     * Gets a list of the active sessions.
     *
     * @return A copy of the list of <code>HttpSession</code> objects.
     */
    @Override
    public Collection<HttpSession> getActiveSessions()
    {
        return new ArrayList<>(activeSessions.values());
    }

    /**
     * Adds a session to the current list.  This method should only be
     * called by the listener.
     *
     * @param session Session to add
     */
    @Override
    public void addSession(HttpSession session)
    {
        activeSessions.put(session.getId(), session);
    }

    /**
     * Removes a session from the current list.  This method should only be
     * called by the listener.
     *
     * @param session Session to remove
     */
    @Override
    public void removeSession(HttpSession session)
    {
        activeSessions.remove(session.getId());
    }

    /**
     * Determines if a given user is currently logged in.  The actual
     * implementation of the User object must implement the equals()
     * method.  By default, Torque based objects (liek TurbineUser)
     * have an implementation of equals() that will compare the
     * result of getPrimaryKey().
     *
     * @param user User to check for
     * @return true if the user is logged in on one of the
     * active sessions.
     */
    @Override
    public boolean isUserLoggedIn(User user)
    {
        return getActiveUsers().contains(user);
    }

    /**
     * Gets a collection of all user objects representing the users currently
     * logged in.  This will exclude any instances of anonymous user that
     * Turbine will use before the user actually logs on.
     *
     * @return A set of {@link org.apache.turbine.om.security.User} objects.
     */
    @Override
    public Collection<User> getActiveUsers()
    {
        Collection<User> users;
        // Pre-allocate a list which won't need expansion more
        // than once.
        users = new ArrayList<>((int) (activeSessions.size() * 0.7));
        for (HttpSession session : activeSessions.values())
        {
            User u = getUserFromSession(session);
            if (u != null && u.hasLoggedIn())
            {
                users.add(u);
            }
        }

        return users;
    }

    /**
     * Gets the User object of the the specified HttpSession.
     *
     * @param session The session from which to extract a user.
     * @return The Turbine User object.
     */
    @Override
    public User getUserFromSession(HttpSession session)
    {
        // Not sure of other containers, but Tomcat 5.0.28 sometimes returns
        // invalid sessions which will result in IllegalStateException when
        // session.getAttribute() is invoked below.
        try
        {
            return (User) session.getAttribute(User.SESSION_KEY);
        }
        catch (IllegalStateException e)
        {
            return null;
        }
    }

    /**
     * Gets the HttpSession by the session identifier
     *
     * @param sessionId The unique session identifier.
     * @return The session keyed by the specified identifier.
     */
    @Override
    public HttpSession getSession(String sessionId)
    {
        return this.activeSessions.get(sessionId);
    }

    /**
     * Get a collection of all session on which the given user
     * is logged in.
     *
     * @param user the user
     * @return Collection of HtttSession objects
     */
    @Override
    public Collection<HttpSession> getSessionsForUser(User user)
    {
        Collection<HttpSession> sessions = new ArrayList<>();
        for (HttpSession session : activeSessions.values())
        {
            User u = this.getUserFromSession(session);
            if (user.equals(u))
            {
                sessions.add(session);
            }
        }

        return sessions;
    }


    // ---- Service initialization ------------------------------------------

    /**
     * Initializes the service
     */
    @Override
    public void init()
    {
        this.activeSessions = new ConcurrentHashMap<>();

        setInit(true);
    }

    /**
     * Returns to uninitialized state.
     */
    @Override
    public void shutdown()
    {
        this.activeSessions = null;

        setInit(false);
    }

}
