/*
 * 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.
 */

package org.apache.catalina.ha.session;

import java.io.Externalizable;
import java.io.IOException;
import java.io.NotSerializableException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.io.Serializable;
import java.security.Principal;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionContext;

import org.apache.catalina.Manager;
import org.apache.catalina.ha.ClusterManager;
import org.apache.catalina.ha.ClusterSession;
import org.apache.catalina.realm.GenericPrincipal;
import org.apache.catalina.session.StandardSession;
import org.apache.catalina.tribes.io.ReplicationStream;
import org.apache.catalina.tribes.tipis.ReplicatedMapEntry;
import org.apache.catalina.util.Enumerator;
import org.apache.catalina.util.StringManager;
import org.apache.catalina.session.StandardManager;
import org.apache.catalina.session.ManagerBase;

/**
 *
 * Similar to the StandardSession except that this session will keep
 * track of deltas during a request.
 *
 * @author Filip Hanik
 * @version $Revision$ $Date$
 */

public class DeltaSession extends StandardSession implements Externalizable,ClusterSession,ReplicatedMapEntry {

    public static org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(DeltaSession.class);

    /**
     * The string manager for this package.
     */
    protected static StringManager sm = StringManager.getManager(Constants.Package);

    // ----------------------------------------------------- Instance Variables

    /**
     * only the primary session will expire, or be able to expire due to
     * inactivity. This is set to false as soon as I receive this session over
     * the wire in a session message. That means that someone else has made a
     * request on another server.
     */
    private transient boolean isPrimarySession = true;

    /**
     * The delta request contains all the action info
     *
     */
    private transient DeltaRequest deltaRequest = null;

    /**
     * Last time the session was replicatd, used for distributed expiring of
     * session
     */
    private transient long lastTimeReplicated = System.currentTimeMillis();


    protected Lock diffLock = new ReentrantReadWriteLock().writeLock();

    private long version;

    // ----------------------------------------------------------- Constructors

    /**
     * Construct a new Session associated with the specified Manager.
     *
     * @param manager
     *            The manager with which this Session is associated
     */
    public DeltaSession() {
        this(null);
    }

    public DeltaSession(Manager manager) {
        super(manager);
        this.resetDeltaRequest();
    }

    // ----------------------------------------------------- ReplicatedMapEntry

    /**
         * Has the object changed since last replication
         * and is not in a locked state
         * @return boolean
         */
        public boolean isDirty() {
            return getDeltaRequest().getSize()>0;
        }

        /**
         * If this returns true, the map will extract the diff using getDiff()
         * Otherwise it will serialize the entire object.
         * @return boolean
         */
        public boolean isDiffable() {
            return true;
        }

        /**
         * Returns a diff and sets the dirty map to false
         * @return byte[]
         * @throws IOException
         */
        public byte[] getDiff() throws IOException {
            return getDeltaRequest().serialize();
        }

        public ClassLoader[] getClassLoaders() {
            if ( manager instanceof BackupManager ) return ((BackupManager)manager).getClassLoaders();
            else if ( manager instanceof ClusterManagerBase ) return ((ClusterManagerBase)manager).getClassLoaders();
            else if ( manager instanceof StandardManager ) {
                StandardManager sm = (StandardManager)manager;
                return ClusterManagerBase.getClassLoaders(sm.getContainer());
            } else if ( manager instanceof ManagerBase ) {
                ManagerBase mb = (ManagerBase)manager;
                return ClusterManagerBase.getClassLoaders(mb.getContainer());
            }//end if
            return null;
        }

        /**
         * Applies a diff to an existing object.
         * @param diff byte[]
         * @param offset int
         * @param length int
         * @throws IOException
         */
        public void applyDiff(byte[] diff, int offset, int length) throws IOException, ClassNotFoundException {
            ReplicationStream stream = ((ClusterManager)getManager()).getReplicationStream(diff,offset,length);
            getDeltaRequest().readExternal(stream);
            ClassLoader contextLoader = Thread.currentThread().getContextClassLoader();
            try {
                ClassLoader[] loaders = getClassLoaders();
                if ( loaders != null && loaders.length >0 ) Thread.currentThread().setContextClassLoader(loaders[0]);
                getDeltaRequest().execute(this);
            }finally {
                Thread.currentThread().setContextClassLoader(contextLoader);
            }
        }

        /**
         * Resets the current diff state and resets the dirty flag
         */
        public void resetDiff() {
            resetDeltaRequest();
        }

        /**
         * Lock during serialization
         */
        public void lock() {
            diffLock.lock();
        }

        /**
         * Unlock after serialization
         */
        public void unlock() {
            diffLock.unlock();
        }

        public void setOwner(Object owner) {
            if ( owner instanceof ClusterManager && getManager()==null) {
                ClusterManager cm = (ClusterManager)owner;
                this.setManager(cm);
                this.setValid(true);
                this.setPrimarySession(false);
                this.access();
                if (cm.isNotifyListenersOnReplication()) this.setId(getIdInternal());
                this.resetDeltaRequest();
                this.endAccess();
            }
        }
    // ----------------------------------------------------- Session Properties

    /**
     * returns true if this session is the primary session, if that is the case,
     * the manager can expire it upon timeout.
     */
    public boolean isPrimarySession() {
        return isPrimarySession;
    }

    /**
     * Sets whether this is the primary session or not.
     *
     * @param primarySession
     *            Flag value
     */
    public void setPrimarySession(boolean primarySession) {
        this.isPrimarySession = primarySession;
    }

    /**
     * Set the session identifier for this session without notify listeners.
     *
     * @param id
     *            The new session identifier
     */
    public void setIdInternal(String id) {
        super.setId(id);
        resetDeltaRequest();
    }

    /**
     * Set the session identifier for this session.
     *
     * @param id
     *            The new session identifier
     */
    public void setId(String id) {
        setIdInternal(id);
    }

   
    /**
     * Return the last client access time without invalidation check
     * @see #getLastAccessedTime().
     */
    public long getLastAccessedTimeInternal() {
        return (this.lastAccessedTime);
    }


    public void setMaxInactiveInterval(int interval, boolean addDeltaRequest) {
        super.maxInactiveInterval = interval;
        if (isValid && interval == 0) {
            expire();
        } else {
            if (addDeltaRequest && (deltaRequest != null))
                deltaRequest.setMaxInactiveInterval(interval);
        }
    }

    /**
     * Set the <code>isNew</code> flag for this session.
     *
     * @param isNew
     *            The new value for the <code>isNew</code> flag
     */
    public void setNew(boolean isNew) {
        setNew(isNew, true);
    }

    public void setNew(boolean isNew, boolean addDeltaRequest) {
        super.setNew(isNew);
        if (addDeltaRequest && (deltaRequest != null))
            deltaRequest.setNew(isNew);
    }

    /**
     * Set the authenticated Principal that is associated with this Session.
     * This provides an <code>Authenticator</code> with a means to cache a
     * previously authenticated Principal, and avoid potentially expensive
     * <code>Realm.authenticate()</code> calls on every request.
     *
     * @param principal
     *            The new Principal, or <code>null</code> if none
     */
    public void setPrincipal(Principal principal) {
        setPrincipal(principal, true);
    }

    public void setPrincipal(Principal principal, boolean addDeltaRequest) {
        try { 
            lock();
            super.setPrincipal(principal);
            if (addDeltaRequest && (deltaRequest != null))
                deltaRequest.setPrincipal(principal);
        } finally {
            unlock();
        }
    }

    /**
     * Return the <code>isValid</code> flag for this session.
     */
    public boolean isValid() {
        if (this.expiring) {
            return true;
        }
        if (!this.isValid) {
            return false;
        }
        if (accessCount > 0) {
            return true;
        }
        if (maxInactiveInterval >= 0) {
            long timeNow = System.currentTimeMillis();
            int timeIdle = (int) ( (timeNow - thisAccessedTime) / 1000L);
            if (isPrimarySession()) {
                if (timeIdle >= maxInactiveInterval) {
                    expire(true);
                }
            } else {
                if (timeIdle >= (2 * maxInactiveInterval)) {
                    //if the session has been idle twice as long as allowed,
                    //the primary session has probably crashed, and no other
                    //requests are coming in. that is why we do this. otherwise
                    //we would have a memory leak
                    expire(true, false);
                }
            }
        }
        return (this.isValid);
    }

    // ------------------------------------------------- Session Public Methods

    /**
     * Perform the internal processing required to invalidate this session,
     * without triggering an exception if the session has already expired.
     *
     * @param notify
     *            Should we notify listeners about the demise of this session?
     */
    public void expire(boolean notify) {
        expire(notify, true);
    }

    public void expire(boolean notify, boolean notifyCluster) {
        String expiredId = getIdInternal();
        super.expire(notify);

        if (notifyCluster) {
            if (log.isDebugEnabled())
                log.debug(sm.getString("deltaSession.notifying",
                                       ((DeltaManager)manager).getName(), 
                                       new Boolean(isPrimarySession()), 
                                       expiredId));
            if ( manager instanceof DeltaManager ) {
                ( (DeltaManager) manager).sessionExpired(expiredId);
            }
        }
    }

    /**
     * Release all object references, and initialize instance variables, in
     * preparation for reuse of this object.
     */
    public void recycle() {
        super.recycle();
        deltaRequest.clear();
    }


    /**
     * Return a string representation of this object.
     */
    public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append("DeltaSession[");
        sb.append(id);
        sb.append("]");
        return (sb.toString());
    }

    // ------------------------------------------------ Session Package Methods

    public synchronized void readExternal(ObjectInput in) throws IOException,ClassNotFoundException {
        readObjectData(in);
    }


    /**
     * Read a serialized version of the contents of this session object from the
     * specified object input stream, without requiring that the StandardSession
     * itself have been serialized.
     *
     * @param stream
     *            The object input stream to read from
     *
     * @exception ClassNotFoundException
     *                if an unknown class is specified
     * @exception IOException
     *                if an input/output error occurs
     */
    public void readObjectData(ObjectInput stream) throws ClassNotFoundException, IOException {
        readObject(stream);
    }

    /**
     * Write a serialized version of the contents of this session object to the
     * specified object output stream, without requiring that the
     * StandardSession itself have been serialized.
     *
     * @param stream
     *            The object output stream to write to
     *
     * @exception IOException
     *                if an input/output error occurs
     */
    public void writeObjectData(ObjectOutput stream) throws IOException {
        writeObject(stream);
    }

    public void resetDeltaRequest() {
        if (deltaRequest == null) {
            deltaRequest = new DeltaRequest(getIdInternal(), false);
        } else {
            deltaRequest.reset();
            deltaRequest.setSessionId(getIdInternal());
        }
    }

    public DeltaRequest getDeltaRequest() {
        if (deltaRequest == null) resetDeltaRequest();
        return deltaRequest;
    }

    // ------------------------------------------------- HttpSession Properties

    // ----------------------------------------------HttpSession Public Methods


    /**
     * Remove the object bound with the specified name from this session. If the
     * session does not have an object bound with this name, this method does
     * nothing.
     * <p>
     * After this method executes, and if the object implements
     * <code>HttpSessionBindingListener</code>, the container calls
     * <code>valueUnbound()</code> on the object.
     *
     * @param name
     *            Name of the object to remove from this session.
     * @param notify
     *            Should we notify interested listeners that this attribute is
     *            being removed?
     *
     * @exception IllegalStateException
     *                if this method is called on an invalidated session
     */
    public void removeAttribute(String name, boolean notify) {
        removeAttribute(name, notify, true);
    }

    public void removeAttribute(String name, boolean notify,boolean addDeltaRequest) {
        // Validate our current state
        if (!isValid()) throw new IllegalStateException(sm.getString("standardSession.removeAttribute.ise"));
        removeAttributeInternal(name, notify, addDeltaRequest);
    }

    /**
     * Bind an object to this session, using the specified name. If an object of
     * the same name is already bound to this session, the object is replaced.
     * <p>
     * After this method executes, and if the object implements
     * <code>HttpSessionBindingListener</code>, the container calls
     * <code>valueBound()</code> on the object.
     *
     * @param name
     *            Name to which the object is bound, cannot be null
     * @param value
     *            Object to be bound, cannot be null
     *
     * @exception IllegalArgumentException
     *                if an attempt is made to add a non-serializable object in
     *                an environment marked distributable.
     * @exception IllegalStateException
     *                if this method is called on an invalidated session
     */
    public void setAttribute(String name, Object value) {
        setAttribute(name, value, true, true);
    }

    public void setAttribute(String name, Object value, boolean notify,boolean addDeltaRequest) {

        // Name cannot be null
        if (name == null) throw new IllegalArgumentException(sm.getString("standardSession.setAttribute.namenull"));

        // Null value is the same as removeAttribute()
        if (value == null) {
            removeAttribute(name);
            return;
        }

        try {
            lock();
            super.setAttribute(name,value, notify);
            if (addDeltaRequest && (deltaRequest != null)) deltaRequest.setAttribute(name, value);
        } finally {
            unlock();
        }
    }

    // -------------------------------------------- HttpSession Private Methods

    /**
     * Read a serialized version of this session object from the specified
     * object input stream.
     * <p>
     * <b>IMPLEMENTATION NOTE </b>: The reference to the owning Manager is not
     * restored by this method, and must be set explicitly.
     *
     * @param stream
     *            The input stream to read from
     *
     * @exception ClassNotFoundException
     *                if an unknown class is specified
     * @exception IOException
     *                if an input/output error occurs
     */
    private void readObject(ObjectInput stream) throws ClassNotFoundException, IOException {

        // Deserialize the scalar instance variables (except Manager)
        authType = null; // Transient only
        creationTime = ( (Long) stream.readObject()).longValue();
        lastAccessedTime = ( (Long) stream.readObject()).longValue();
        maxInactiveInterval = ( (Integer) stream.readObject()).intValue();
        isNew = ( (Boolean) stream.readObject()).booleanValue();
        isValid = ( (Boolean) stream.readObject()).booleanValue();
        thisAccessedTime = ( (Long) stream.readObject()).longValue();
        version = ( (Long) stream.readObject()).longValue();
        boolean hasPrincipal = stream.readBoolean();
        principal = null;
        if (hasPrincipal) {
            principal = SerializablePrincipal.readPrincipal(stream,getManager().getContainer().getRealm());
        }

        //        setId((String) stream.readObject());
        id = (String) stream.readObject();
        if (log.isDebugEnabled()) log.debug(sm.getString("deltaSession.readSession", id));

        // Deserialize the attribute count and attribute values
        if (attributes == null) attributes = new Hashtable();
        int n = ( (Integer) stream.readObject()).intValue();
        boolean isValidSave = isValid;
        isValid = true;
        for (int i = 0; i < n; i++) {
            String name = (String) stream.readObject();
            Object value = (Object) stream.readObject();
            if ( (value instanceof String) && (value.equals(NOT_SERIALIZED)))
                continue;
            attributes.put(name, value);
        }
        isValid = isValidSave;

        if (listeners == null) {
            listeners = new ArrayList();
        }

        if (notes == null) {
            notes = new Hashtable();
        }
    }

    public synchronized void writeExternal(ObjectOutput out ) throws java.io.IOException {
        writeObject(out);
    }


    /**
     * Write a serialized version of this session object to the specified object
     * output stream.
     * <p>
     * <b>IMPLEMENTATION NOTE </b>: The owning Manager will not be stored in the
     * serialized representation of this Session. After calling
     * <code>readObject()</code>, you must set the associated Manager
     * explicitly.
     * <p>
     * <b>IMPLEMENTATION NOTE </b>: Any attribute that is not Serializable will
     * be unbound from the session, with appropriate actions if it implements
     * HttpSessionBindingListener. If you do not want any such attributes, be
     * sure the <code>distributable</code> property of the associated Manager
     * is set to <code>true</code>.
     *
     * @param stream
     *            The output stream to write to
     *
     * @exception IOException
     *                if an input/output error occurs
     */
    private void writeObject(ObjectOutput stream) throws IOException {

        // Write the scalar instance variables (except Manager)
        stream.writeObject(new Long(creationTime));
        stream.writeObject(new Long(lastAccessedTime));
        stream.writeObject(new Integer(maxInactiveInterval));
        stream.writeObject(new Boolean(isNew));
        stream.writeObject(new Boolean(isValid));
        stream.writeObject(new Long(thisAccessedTime));
        stream.writeObject(new Long(version));
        stream.writeBoolean(getPrincipal() != null);
        if (getPrincipal() != null) {
            SerializablePrincipal.writePrincipal((GenericPrincipal) principal,stream);
        }

        stream.writeObject(id);
        if (log.isDebugEnabled()) log.debug(sm.getString("deltaSession.writeSession", id));

        // Accumulate the names of serializable and non-serializable attributes
        String keys[] = keys();
        ArrayList saveNames = new ArrayList();
        ArrayList saveValues = new ArrayList();
        for (int i = 0; i < keys.length; i++) {
            Object value = null;
            value = attributes.get(keys[i]);
            if (value == null)
                continue;
            else if (value instanceof Serializable) {
                saveNames.add(keys[i]);
                saveValues.add(value);
            }
        }

        // Serialize the attribute count and the Serializable attributes
        int n = saveNames.size();
        stream.writeObject(new Integer(n));
        for (int i = 0; i < n; i++) {
            stream.writeObject( (String) saveNames.get(i));
            try {
                stream.writeObject(saveValues.get(i));
            } catch (NotSerializableException e) {
                log.error(sm.getString("standardSession.notSerializable",saveNames.get(i), id), e);
                stream.writeObject(NOT_SERIALIZED);
                log.error("  storing attribute '" + saveNames.get(i)+ "' with value NOT_SERIALIZED");
            }
        }

    }

    // -------------------------------------------------------- Private Methods

    
    /**
     * Return the value of an attribute without a check for validity.
     */
    protected Object getAttributeInternal(String name) {
        return (attributes.get(name));
    }

    protected void removeAttributeInternal(String name, boolean notify,
                                           boolean addDeltaRequest) {
        try {
            lock();
            // Remove this attribute from our collection
            Object value = attributes.get(name);
            if (value == null) return;

            super.removeAttributeInternal(name,notify);
            if (addDeltaRequest && (deltaRequest != null)) deltaRequest.removeAttribute(name);

        }finally {
            unlock();
        }
    }

    protected long getLastTimeReplicated() {
        return lastTimeReplicated;
    }

    public long getVersion() {
        return version;
    }

    protected void setLastTimeReplicated(long lastTimeReplicated) {
        this.lastTimeReplicated = lastTimeReplicated;
    }

    public void setVersion(long version) {
        this.version = version;
    }

    protected void setAccessCount(int count) {
        super.accessCount = count;
    }
}

// -------------------------------------------------------------- Private Class

/**
 * This class is a dummy implementation of the <code>HttpSessionContext</code>
 * interface, to conform to the requirement that such an object be returned when
 * <code>HttpSession.getSessionContext()</code> is called.
 *
 * @author Craig R. McClanahan
 *
 * @deprecated As of Java Servlet API 2.1 with no replacement. The interface
 *             will be removed in a future version of this API.
 */

final class StandardSessionContext
    implements HttpSessionContext {

    private HashMap dummy = new HashMap();

    /**
     * Return the session identifiers of all sessions defined within this
     * context.
     *
     * @deprecated As of Java Servlet API 2.1 with no replacement. This method
     *             must return an empty <code>Enumeration</code> and will be
     *             removed in a future version of the API.
     */
    public Enumeration getIds() {
        return (new Enumerator(dummy));
    }

    /**
     * Return the <code>HttpSession</code> associated with the specified
     * session identifier.
     *
     * @param id
     *            Session identifier for which to look up a session
     *
     * @deprecated As of Java Servlet API 2.1 with no replacement. This method
     *             must return null and will be removed in a future version of
     *             the API.
     */
    public HttpSession getSession(String id) {
        return (null);
    }

}