/*
    * 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.shiro.session.mgt;
  
  import org.apache.shiro.session.ExpiredSessionException;
  import org.apache.shiro.session.InvalidSessionException;
  import org.apache.shiro.session.StoppedSessionException;
  import org.apache.shiro.util.CollectionUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.Serializable;
  import java.text.DateFormat;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Date;
  import java.util.HashMap;
  import java.util.Map;
  
  
  /**
   * Simple {@link org.apache.shiro.session.Session} JavaBeans-compatible POJO implementation, intended to be used on the
   * business/server tier.
   *
   * @since 0.1
   */
  @SuppressWarnings("checkstyle:MethodCount")
  public class SimpleSession implements ValidatingSession, Serializable {
  
      protected static final long MILLIS_PER_SECOND = 1000;
      protected static final long MILLIS_PER_MINUTE = 60 * MILLIS_PER_SECOND;
      protected static final long MILLIS_PER_HOUR = 60 * MILLIS_PER_MINUTE;
  
      //serialization bitmask fields. DO NOT CHANGE THE ORDER THEY ARE DECLARED!
      static int bitIndexCounter;
  
      // Serialization reminder:
      // You _MUST_ change this number if you introduce a change to this class
      // that is NOT serialization backwards compatible.  Serialization-compatible
      // changes do not require a change to this number.  If you need to generate
      // a new number in this case, use the JDK's 'serialver' program to generate it.
      private static final long serialVersionUID = -7125642695178165650L;
  
      private static final Logger LOGGER = LoggerFactory.getLogger(SimpleSession.class);
      private static final int ID_BIT_MASK = 1 << bitIndexCounter++;
      private static final int START_TIMESTAMP_BIT_MASK = 1 << bitIndexCounter++;
      private static final int STOP_TIMESTAMP_BIT_MASK = 1 << bitIndexCounter++;
      private static final int LAST_ACCESS_TIME_BIT_MASK = 1 << bitIndexCounter++;
      private static final int TIMEOUT_BIT_MASK = 1 << bitIndexCounter++;
      private static final int EXPIRED_BIT_MASK = 1 << bitIndexCounter++;
      private static final int HOST_BIT_MASK = 1 << bitIndexCounter++;
      private static final int ATTRIBUTES_BIT_MASK = 1 << bitIndexCounter++;
  
      // ==============================================================
      // NOTICE:
      //
      // The following fields are marked as transient to avoid double-serialization.
      // They are in fact serialized (even though 'transient' usually indicates otherwise),
      // but they are serialized explicitly via the writeObject and readObject implementations
      // in this class.
      //
      // If we didn't declare them as transient, the out.defaultWriteObject(); call in writeObject would
      // serialize all non-transient fields as well, effectively doubly serializing the fields (also
      // doubling the serialization size).
      //
      // This finding, with discussion, was covered here:
      //
      // http://mail-archives.apache.org/mod_mbox/shiro-user/201109.mbox/%3C4E81BCBD.8060909@metaphysis.net%3E
      //
      // ==============================================================
      private transient Serializable id;
      private transient Date startTimestamp;
      private transient Date stopTimestamp;
      private transient Date lastAccessTime;
      private transient long timeout;
      private transient boolean expired;
      private transient String host;
      private transient Map<Object, Object> attributes;
  
      public SimpleSession() {
         //TODO - remove concrete reference to DefaultSessionManager
         this.timeout = DefaultSessionManager.DEFAULT_GLOBAL_SESSION_TIMEOUT;
         this.startTimestamp = new Date();
         this.lastAccessTime = this.startTimestamp;
     }
 
     public SimpleSession(String host) {
         this();
         this.host = host;
     }
 
     public Serializable getId() {
         return this.id;
     }
 
     public void setId(Serializable id) {
         this.id = id;
     }
 
     public Date getStartTimestamp() {
         return startTimestamp;
     }
 
     public void setStartTimestamp(Date startTimestamp) {
         this.startTimestamp = startTimestamp;
     }
 
     /**
      * Returns the time the session was stopped, or <tt>null</tt> if the session is still active.
      * <p/>
      * A session may become stopped under a number of conditions:
      * <ul>
      * <li>If the user logs out of the system, their current session is terminated (released).</li>
      * <li>If the session expires</li>
      * <li>The application explicitly calls {@link #stop()}</li>
      * <li>If there is an internal system error and the session state can no longer accurately
      * reflect the user's behavior, such in the case of a system crash</li>
      * </ul>
      * <p/>
      * Once stopped, a session may no longer be used.  It is locked from all further activity.
      *
      * @return The time the session was stopped, or <tt>null</tt> if the session is still
      * active.
      */
     public Date getStopTimestamp() {
         return stopTimestamp;
     }
 
     public void setStopTimestamp(Date stopTimestamp) {
         this.stopTimestamp = stopTimestamp;
     }
 
     public Date getLastAccessTime() {
         return lastAccessTime;
     }
 
     public void setLastAccessTime(Date lastAccessTime) {
         this.lastAccessTime = lastAccessTime;
     }
 
     /**
      * Returns true if this session has expired, false otherwise.  If the session has
      * expired, no further user interaction with the system may be done under this session.
      *
      * @return true if this session has expired, false otherwise.
      */
     public boolean isExpired() {
         return expired;
     }
 
     public void setExpired(boolean expired) {
         this.expired = expired;
     }
 
     public long getTimeout() {
         return timeout;
     }
 
     public void setTimeout(long timeout) {
         this.timeout = timeout;
     }
 
     public String getHost() {
         return host;
     }
 
     public void setHost(String host) {
         this.host = host;
     }
 
     public Map<Object, Object> getAttributes() {
         return attributes;
     }
 
     public void setAttributes(Map<Object, Object> attributes) {
         this.attributes = attributes;
     }
 
     public void touch() {
         this.lastAccessTime = new Date();
     }
 
     public void stop() {
         if (this.stopTimestamp == null) {
             this.stopTimestamp = new Date();
         }
     }
 
     protected boolean isStopped() {
         return getStopTimestamp() != null;
     }
 
     protected void expire() {
         stop();
         this.expired = true;
     }
 
     /**
      * @since 0.9
      */
     public boolean isValid() {
         return !isStopped() && !isExpired();
     }
 
     /**
      * Determines if this session is expired.
      *
      * @return true if the specified session has expired, false otherwise.
      */
     protected boolean isTimedOut() {
 
         if (isExpired()) {
             return true;
         }
 
         long timeout = getTimeout();
 
         if (timeout >= 0L) {
 
             Date lastAccessTime = getLastAccessTime();
 
             if (lastAccessTime == null) {
                 String msg = "session.lastAccessTime for session with id ["
                         + getId() + "] is null.  This value must be set at "
                         + "least once, preferably at least upon instantiation.  Please check the "
                         + getClass().getName() + " implementation and ensure "
                         + "this value will be set (perhaps in the constructor?)";
                 throw new IllegalStateException(msg);
             }
 
             // Calculate at what time a session would have been last accessed
             // for it to be expired at this point.  In other words, subtract
             // from the current time the amount of time that a session can
             // be inactive before expiring.  If the session was last accessed
             // before this time, it is expired.
             long expireTimeMillis = System.currentTimeMillis() - timeout;
             Date expireTime = new Date(expireTimeMillis);
             return lastAccessTime.before(expireTime);
         } else {
             if (LOGGER.isTraceEnabled()) {
                 LOGGER.trace("No timeout for session with id [" + getId()
                         + "].  Session is not considered expired.");
             }
         }
 
         return false;
     }
 
     public void validate() throws InvalidSessionException {
         //check for stopped:
         if (isStopped()) {
             //timestamp is set, so the session is considered stopped:
             String msg = "Session with id [" + getId() + "] has been "
                     + "explicitly stopped.  No further interaction under this session is "
                     + "allowed.";
             throw new StoppedSessionException(msg);
         }
 
         //check for expiration
         if (isTimedOut()) {
             expire();
 
             //throw an exception explaining details of why it expired:
             Date lastAccessTime = getLastAccessTime();
             long timeout = getTimeout();
 
             Serializable sessionId = getId();
 
             DateFormat df = DateFormat.getInstance();
             String msg = "Session with id [" + sessionId + "] has expired. "
                     + "Last access time: " + df.format(lastAccessTime)
                     + ".  Current time: " + df.format(new Date())
                     + ".  Session timeout is set to " + timeout / MILLIS_PER_SECOND + " seconds ("
                     + timeout / MILLIS_PER_MINUTE + " minutes)";
             if (LOGGER.isTraceEnabled()) {
                 LOGGER.trace(msg);
             }
             throw new ExpiredSessionException(msg);
         }
     }
 
     private Map<Object, Object> getAttributesLazy() {
         Map<Object, Object> attributes = getAttributes();
         if (attributes == null) {
             attributes = new HashMap<Object, Object>();
             setAttributes(attributes);
         }
         return attributes;
     }
 
     public Collection<Object> getAttributeKeys() throws InvalidSessionException {
         Map<Object, Object> attributes = getAttributes();
         if (attributes == null) {
             return Collections.emptySet();
         }
         return attributes.keySet();
     }
 
     public Object getAttribute(Object key) {
         Map<Object, Object> attributes = getAttributes();
         if (attributes == null) {
             return null;
         }
         return attributes.get(key);
     }
 
     public void setAttribute(Object key, Object value) {
         if (value == null) {
             removeAttribute(key);
         } else {
             getAttributesLazy().put(key, value);
         }
     }
 
     public Object removeAttribute(Object key) {
         Map<Object, Object> attributes = getAttributes();
         if (attributes == null) {
             return null;
         } else {
             return attributes.remove(key);
         }
     }
 
     /**
      * Returns {@code true} if the specified argument is an {@code instanceof} {@code SimpleSession} and both
      * {@link #getId() id}s are equal.  If the argument is a {@code SimpleSession} and either 'this' or the argument
      * does not yet have an ID assigned, the value of {@link #onEquals(SimpleSession) onEquals} is returned, which
      * does a necessary attribute-based comparison when IDs are not available.
      * <p/>
      * Do your best to ensure {@code SimpleSession} instances receive an ID very early in their lifecycle to
      * avoid the more expensive attributes-based comparison.
      *
      * @param obj the object to compare with this one for equality.
      * @return {@code true} if this object is equivalent to the specified argument, {@code false} otherwise.
      */
     @Override
     public boolean equals(Object obj) {
         if (this == obj) {
             return true;
         }
         if (obj instanceof SimpleSession) {
             SimpleSession other = (SimpleSession) obj;
             Serializable thisId = getId();
             Serializable otherId = other.getId();
             if (thisId != null && otherId != null) {
                 return thisId.equals(otherId);
             } else {
                 //fall back to an attribute based comparison:
                 return onEquals(other);
             }
         }
         return false;
     }
 
     /**
      * Provides an attribute-based comparison (no ID comparison) - incurred <em>only</em> when 'this' or the
      * session object being compared for equality do not have a session id.
      *
      * @param ss the SimpleSession instance to compare for equality.
      * @return true if all the attributes, except the id, are equal to this object's attributes.
      * @since 1.0
      */
     @SuppressWarnings({"checkstyle:BooleanExpressionComplexity", "checkstyle:MethodCount"})
     protected boolean onEquals(SimpleSession ss) {
         return (getStartTimestamp() != null ? getStartTimestamp().equals(ss.getStartTimestamp()) : ss.getStartTimestamp() == null)
                 && (getStopTimestamp() != null ? getStopTimestamp().equals(ss.getStopTimestamp()) : ss.getStopTimestamp() == null)
                 && (getLastAccessTime() != null
                         ? getLastAccessTime().equals(ss.getLastAccessTime()) : ss.getLastAccessTime() == null)
                 && (getTimeout() == ss.getTimeout())
                 && (isExpired() == ss.isExpired())
                 && (getHost() != null ? getHost().equals(ss.getHost()) : ss.getHost() == null)
                 && (getAttributes() != null ? getAttributes().equals(ss.getAttributes()) : ss.getAttributes() == null);
     }
 
     /**
      * Returns the hashCode.  If the {@link #getId() id} is not {@code null}, its hashcode is returned immediately.
      * If it is {@code null}, an attributes-based hashCode will be calculated and returned.
      * <p/>
      * Do your best to ensure {@code SimpleSession} instances receive an ID very early in their lifecycle to
      * avoid the more expensive attributes-based calculation.
      *
      * @return this object's hashCode
      * @since 1.0
      */
     @Override
     public int hashCode() {
         Serializable id = getId();
         if (id != null) {
             return id.hashCode();
         }
         int hashCode = getStartTimestamp() != null ? getStartTimestamp().hashCode() : 0;
         hashCode = 31 * hashCode + (getStopTimestamp() != null ? getStopTimestamp().hashCode() : 0);
         hashCode = 31 * hashCode + (getLastAccessTime() != null ? getLastAccessTime().hashCode() : 0);
         hashCode = 31 * hashCode + Long.valueOf(Math.max(getTimeout(), 0)).hashCode();
         hashCode = 31 * hashCode + Boolean.valueOf(isExpired()).hashCode();
         hashCode = 31 * hashCode + (getHost() != null ? getHost().hashCode() : 0);
         hashCode = 31 * hashCode + (getAttributes() != null ? getAttributes().hashCode() : 0);
         return hashCode;
     }
 
     /**
      * Returns the string representation of this SimpleSession, equal to
      * <code>getClass().getName() + &quot;,id=&quot; + getId()</code>.
      *
      * @return the string representation of this SimpleSession, equal to
      * <code>getClass().getName() + &quot;,id=&quot; + getId()</code>.
      * @since 1.0
      */
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append(getClass().getName()).append(",id=").append(getId());
         return sb.toString();
     }
 
     /**
      * Serializes this object to the specified output stream for JDK Serialization.
      *
      * @param out output stream used for Object serialization.
      * @throws IOException if any of this object's fields cannot be written to the stream.
      * @since 1.0
      */
     @SuppressWarnings("checkstyle:NPathComplexity")
     private void writeObject(ObjectOutputStream out) throws IOException {
         out.defaultWriteObject();
         short alteredFieldsBitMask = getAlteredFieldsBitMask();
         out.writeShort(alteredFieldsBitMask);
         if (id != null) {
             out.writeObject(id);
         }
         if (startTimestamp != null) {
             out.writeObject(startTimestamp);
         }
         if (stopTimestamp != null) {
             out.writeObject(stopTimestamp);
         }
         if (lastAccessTime != null) {
             out.writeObject(lastAccessTime);
         }
         if (timeout != 0L) {
             out.writeLong(timeout);
         }
         if (expired) {
             out.writeBoolean(expired);
         }
         if (host != null) {
             out.writeUTF(host);
         }
         if (!CollectionUtils.isEmpty(attributes)) {
             out.writeObject(attributes);
         }
     }
 
     /**
      * Reconstitutes this object based on the specified InputStream for JDK Serialization.
      *
      * @param in the input stream to use for reading data to populate this object.
      * @throws IOException            if the input stream cannot be used.
      * @throws ClassNotFoundException if a required class needed for instantiation is not available in the present JVM
      * @since 1.0
      */
     @SuppressWarnings({"unchecked", "checkstyle:NPathComplexity"})
     private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
         in.defaultReadObject();
         short bitMask = in.readShort();
 
         if (isFieldPresent(bitMask, ID_BIT_MASK)) {
             this.id = (Serializable) in.readObject();
         }
         if (isFieldPresent(bitMask, START_TIMESTAMP_BIT_MASK)) {
             this.startTimestamp = (Date) in.readObject();
         }
         if (isFieldPresent(bitMask, STOP_TIMESTAMP_BIT_MASK)) {
             this.stopTimestamp = (Date) in.readObject();
         }
         if (isFieldPresent(bitMask, LAST_ACCESS_TIME_BIT_MASK)) {
             this.lastAccessTime = (Date) in.readObject();
         }
         if (isFieldPresent(bitMask, TIMEOUT_BIT_MASK)) {
             this.timeout = in.readLong();
         }
         if (isFieldPresent(bitMask, EXPIRED_BIT_MASK)) {
             this.expired = in.readBoolean();
         }
         if (isFieldPresent(bitMask, HOST_BIT_MASK)) {
             this.host = in.readUTF();
         }
         if (isFieldPresent(bitMask, ATTRIBUTES_BIT_MASK)) {
             this.attributes = (Map<Object, Object>) in.readObject();
         }
     }
 
     /**
      * Returns a bit mask used during serialization indicating which fields have been serialized. Fields that have been
      * altered (not null and/or not retaining the class defaults) will be serialized and have 1 in their respective
      * index, fields that are null and/or retain class default values have 0.
      *
      * @return a bit mask used during serialization indicating which fields have been serialized.
      * @since 1.0
      */
     @SuppressWarnings("checkstyle:NPathComplexity")
     private short getAlteredFieldsBitMask() {
         int bitMask = 0;
         bitMask = id != null ? bitMask | ID_BIT_MASK : bitMask;
         bitMask = startTimestamp != null ? bitMask | START_TIMESTAMP_BIT_MASK : bitMask;
         bitMask = stopTimestamp != null ? bitMask | STOP_TIMESTAMP_BIT_MASK : bitMask;
         bitMask = lastAccessTime != null ? bitMask | LAST_ACCESS_TIME_BIT_MASK : bitMask;
         bitMask = timeout != 0L ? bitMask | TIMEOUT_BIT_MASK : bitMask;
         bitMask = expired ? bitMask | EXPIRED_BIT_MASK : bitMask;
         bitMask = host != null ? bitMask | HOST_BIT_MASK : bitMask;
         bitMask = !CollectionUtils.isEmpty(attributes) ? bitMask | ATTRIBUTES_BIT_MASK : bitMask;
         return (short) bitMask;
     }
 
     /**
      * Returns {@code true} if the given {@code bitMask} argument indicates that the specified field has been
      * serialized and therefore should be read during deserialization, {@code false} otherwise.
      *
      * @param bitMask      the aggregate bitmask for all fields that have been serialized.  Individual bits represent
      *                     the fields that have been serialized.  A bit set to 1 means that corresponding field has
      *                     been serialized, 0 means it hasn't been serialized.
      * @param fieldBitMask the field bit mask constant identifying which bit to inspect (corresponds to a class attribute).
      * @return {@code true} if the given {@code bitMask} argument indicates that the specified field has been
      * serialized and therefore should be read during deserialization, {@code false} otherwise.
      * @since 1.0
      */
     private static boolean isFieldPresent(short bitMask, int fieldBitMask) {
         return (bitMask & fieldBitMask) != 0;
     }
 
 }