/*
    * Copyright 2009-2010 Capgemini Licensed 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 net.sourceforge.statelessfilter.session;
  
  import java.io.Serializable;
  import java.security.NoSuchAlgorithmException;
  import java.security.SecureRandom;
  import java.util.Enumeration;
  import java.util.List;
  import java.util.Map;
  import java.util.Vector;
  import java.util.concurrent.ConcurrentHashMap;
  
  import javax.servlet.ServletContext;
  import javax.servlet.http.HttpSession;
  import javax.servlet.http.HttpSessionContext;
  
  import net.sourceforge.statelessfilter.backend.ISessionData;
  import net.sourceforge.statelessfilter.wrappers.StatelessRequestWrapper;
  
  import org.apache.commons.codec.binary.Hex;
  import org.apache.commons.collections.IteratorUtils;
  import org.apache.commons.lang.NotImplementedException;
  
  /**
   * Stateless session object, returned by the wrapped request.
   * 
   * @author Nicolas Richeton - Capgemini
   * 
   */
  public class StatelessSession implements HttpSession, Serializable {
  	final private static String SECURE_ALGORITHM = "SHA1PRNG"; //$NON-NLS-1$
  
  	final private static String NULL_VALUE = "net.sourceforge.statelessfilter.session.NullValue";
  	/**
  	 * Generated serial ID
  	 */
  	private static final long serialVersionUID = 3707021777892035588L;
  	private Map<String, Object> content;
  
  	private long creationTime;
  
  	private String id;
  	private boolean isNew;
  	private final long lastAccessedTime = 0;
  	private int maxInactiveInterval = 30 * 60;
  
  	/**
  	 * Modified attributes during the current request.
  	 */
  	private volatile List<String> modifiedAttributes = new Vector<String>();
  
  	/**
  	 * Were this session properties (validity, maxInactiveInterval) modified
  	 * during the current request.
  	 */
  	private volatile boolean propertyDirty = false;
  
  	/**
  	 * Was this session modified during the current request.
  	 */
  	private volatile boolean dirty = false;
  
  	private final StatelessRequestWrapper request;
  	private boolean valid;
  
  	/**
  	 * Creates a new StatelessSession.
  	 * 
  	 * @param request
  	 */
  	public StatelessSession(StatelessRequestWrapper request) {
  		this.request = request;
  	}
  
  	/**
  	 * @see javax.servlet.http.HttpSession#getAttribute(java.lang.String)
  	 */
  	public Object getAttribute(String name) {
  		Object result = content.get(name);
  
  		if (result instanceof String && NULL_VALUE.equals(result)) {
  			result = null;
  		}
  
  		return result;
  	}
  
 	/**
 	 * @see javax.servlet.http.HttpSession#getAttributeNames()
 	 */
 	@SuppressWarnings("unchecked")
 	public Enumeration getAttributeNames() {
 		return IteratorUtils.asEnumeration(content.keySet().iterator());
 	}
 
 	/**
 	 * Get all session content.
 	 * 
 	 * @return
 	 */
 	public Map<String, Object> getContent() {
 		return content;
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getCreationTime()
 	 */
 	public long getCreationTime() {
 		return creationTime;
 	}
 
 	public List<String> getDirtyAttributes() {
 		return modifiedAttributes;
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getId()
 	 */
 	public String getId() {
 		return id;
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getLastAccessedTime()
 	 */
 	public long getLastAccessedTime() {
 		return lastAccessedTime;
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getMaxInactiveInterval()
 	 */
 	public int getMaxInactiveInterval() {
 		return maxInactiveInterval;
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getServletContext()
 	 */
 	public ServletContext getServletContext() {
 		return request.getServerSession().getServletContext();
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getSessionContext()
 	 * @deprecated
 	 */
 	@Deprecated
 	public HttpSessionContext getSessionContext() {
 		throw new NotImplementedException();
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getValue(java.lang.String)
 	 * @deprecated
 	 */
 	@Deprecated
 	public Object getValue(String name) {
 		return getAttribute(name);
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#getValueNames()
 	 * @deprecated
 	 */
 	@Deprecated
 	public String[] getValueNames() {
 		return (String[]) content.keySet().toArray();
 	}
 
 	/**
 	 * Init session internal values.
 	 * 
 	 * @throws NoSuchAlgorithmException
 	 *             - if strong random generator not available
 	 */
 	public void init() throws NoSuchAlgorithmException {
 		init(true);
 	}
 
 	/**
 	 * Init session internal values.
 	 * <ul>
 	 * <li>As a new session if newSession is true</li>
 	 * <li>As an existing session if new Session if false</li>
 	 * </ul
 	 * 
 	 * 
 	 * @param newSession
 	 * @throws NoSuchAlgorithmException
 	 */
 	public void init(boolean newSession) throws NoSuchAlgorithmException {
 
 		if (newSession) {
 			SecureRandom rand = SecureRandom.getInstance(SECURE_ALGORITHM);
 			byte[] data = new byte[32];
 			rand.nextBytes(data);
 			creationTime = System.currentTimeMillis();
 			id = new String(Hex.encodeHex(data)) + creationTime;
 			valid = true;
 			setPropertyDirty();
 		}
 
 		content = new ConcurrentHashMap<String, Object>();
 		isNew = newSession;
 		dirty = newSession;
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#invalidate()
 	 */
 	public void invalidate() {
 		valid = false;
 		setPropertyDirty();
 		content = new ConcurrentHashMap<String, Object>();
 	}
 
 	public boolean isDirty() {
 		return dirty;
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#isNew()
 	 */
 	public boolean isNew() {
 		return isNew;
 	}
 
 	public boolean isPropertyDirty() {
 		return propertyDirty;
 	}
 
 	/**
 	 * Checks session validity
 	 * 
 	 * @return
 	 */
 	public boolean isValid() {
 		return valid;
 	}
 
 	/**
 	 * Merge session data with an external ISessionData object.
 	 * 
 	 * @param data
 	 */
 	public void merge(ISessionData data) {
 		content.putAll(data.getContent());
 		id = data.getId();
 		valid = data.isValid();
 		creationTime = data.getCreationTime();
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#putValue(java.lang.String,
 	 *      java.lang.Object)
 	 * @deprecated
 	 */
 	@Deprecated
 	public void putValue(String name, Object value) {
 		setAttribute(name, value);
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#removeAttribute(java.lang.String)
 	 */
 	public void removeAttribute(String name) {
 		content.remove(name);
 		setAttributeDirty(name);
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#removeValue(java.lang.String)
 	 * @deprecated
 	 */
 	@Deprecated
 	public void removeValue(String name) {
 		removeAttribute(name);
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#setAttribute(java.lang.String,
 	 *      java.lang.Object)
 	 */
 	public void setAttribute(String name, Object value) {
 		Object toInsert = value;
 
 		if (toInsert == null) {
 			toInsert = NULL_VALUE;
 		}
 
 		content.put(name, toInsert);
 		setAttributeDirty(name);
 	}
 
 	/**
 	 * @see javax.servlet.http.HttpSession#setMaxInactiveInterval(int)
 	 */
 	public void setMaxInactiveInterval(int interval) {
 		this.maxInactiveInterval = interval;
 		setPropertyDirty();
 	}
 
 	/**
 	 * Set session new state.
 	 * 
 	 * @param b
 	 */
 	public void setNew(boolean b) {
 		this.isNew = b;
 	}
 
 	/**
 	 * Set the dirty flag for attributeName and for the whole session.
 	 * 
 	 * @param attrName
 	 *            Name of the attribute to be flagged.
 	 */
 	private void setAttributeDirty(String attrName) {
 		if (!modifiedAttributes.contains(attrName)) {
 			modifiedAttributes.add(attrName);
 		}
 		dirty = true;
 	}
 
 	private void setPropertyDirty() {
 		dirty = true;
 		propertyDirty = true;
 	}
 }