/*
    * #%L
    * TimestampElement.java - mongodb-async-driver - Allanbank Consulting, Inc.
    * %%
    * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.
    * %%
    * 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.
   * #L%
   */
  package com.allanbank.mongodb.bson.element;
  
  import java.util.Date;
  
  import com.allanbank.mongodb.bson.Element;
  import com.allanbank.mongodb.bson.ElementType;
  import com.allanbank.mongodb.bson.Visitor;
  import com.allanbank.mongodb.bson.io.StringEncoder;
  
  /**
   * A wrapper for a BSON timestamp as the milliseconds since the epoch.
   * 
   * @api.yes This class is part of the driver's API. Public and protected members
   *          will be deprecated for at least 1 non-bugfix release (version
   *          numbers are <major>.<minor>.<bugfix>) before being
   *          removed or modified.
   * @copyright 2011-2013, Allanbank Consulting, Inc., All Rights Reserved
   */
  public class TimestampElement extends AbstractElement {
  
      /** The BSON type for a long. */
      public static final ElementType TYPE = ElementType.UTC_TIMESTAMP;
  
      /** Serialization version for the class. */
      private static final long serialVersionUID = 949598909338399091L;
  
      /**
       * Computes and returns the number of bytes that are used to encode the
       * element.
       * 
       * @param name
       *            The name for the element.
       * @return The size of the element when encoded in bytes.
       */
      private static long computeSize(final String name) {
          long result = 10; // type (1) + name null byte (1) + value (8).
          result += StringEncoder.utf8Size(name);
  
          return result;
      }
  
      /** The BSON timestamp value as the milliseconds since the epoch. */
      private final long myTimestamp;
  
      /**
       * Constructs a new {@link TimestampElement}.
       * 
       * @param name
       *            The name for the BSON long.
       * @param value
       *            The BSON timestamp value as the milliseconds since the epoch.
       * @throws IllegalArgumentException
       *             If the {@code name} is <code>null</code>.
       */
      public TimestampElement(final String name, final long value) {
          this(name, value, computeSize(name));
      }
  
      /**
       * Constructs a new {@link TimestampElement}.
       * 
       * @param name
       *            The name for the BSON long.
       * @param value
       *            The BSON timestamp value as the milliseconds since the epoch.
       * @param size
       *            The size of the element when encoded in bytes. If not known
       *            then use the
       *            {@link TimestampElement#TimestampElement(String, long)}
       *            constructor instead.
       * @throws IllegalArgumentException
       *             If the {@code name} is <code>null</code>.
       */
      public TimestampElement(final String name, final long value, final long size) {
          super(name, size);
  
          myTimestamp = value;
      }
  
      /**
      * Accepts the visitor and calls the {@link Visitor#visitTimestamp} method.
      * 
      * @see Element#accept(Visitor)
      */
     @Override
     public void accept(final Visitor visitor) {
         visitor.visitTimestamp(getName(), getTime());
     }
 
     /**
      * {@inheritDoc}
      * <p>
      * Overridden to compare the times if the base class comparison is equals.
      * </p>
      * <p>
      * Note that for MongoDB {@link MongoTimestampElement} and
      * {@link TimestampElement} will return equal based on the type. Care is
      * taken here to make sure that the values return the same value regardless
      * of comparison order.
      * </p>
      */
     @Override
     public int compareTo(final Element otherElement) {
         int result = super.compareTo(otherElement);
 
         if (result == 0) {
             // Might be a MongoTimestampElement or TimestampElement.
             final ElementType otherType = otherElement.getType();
 
             if (otherType == ElementType.UTC_TIMESTAMP) {
                 result = compare(getTime(),
                         ((TimestampElement) otherElement).getTime());
             }
             else {
                 result = compare(getTime(),
                         ((MongoTimestampElement) otherElement).getTime());
             }
         }
 
         return result;
     }
 
     /**
      * Determines if the passed object is of this same type as this object and
      * if so that its fields are equal.
      * 
      * @param object
      *            The object to compare to.
      * 
      * @see java.lang.Object#equals(java.lang.Object)
      */
     @Override
     public boolean equals(final Object object) {
         boolean result = false;
         if (this == object) {
             result = true;
         }
         else if ((object != null) && (getClass() == object.getClass())) {
             final TimestampElement other = (TimestampElement) object;
 
             result = super.equals(object) && (myTimestamp == other.myTimestamp);
         }
         return result;
     }
 
     /**
      * Returns the BSON timestamp value as the milliseconds since the epoch.
      * 
      * @return The BSON timestamp value as the milliseconds since the epoch.
      */
     public long getTime() {
         return myTimestamp;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public ElementType getType() {
         return TYPE;
     }
 
     /**
      * {@inheritDoc}
      * <p>
      * Returns the {@link Date}.
      * </p>
      */
     @Override
     public Date getValueAsObject() {
         return new Date(getTime());
     }
 
     /**
      * Computes a reasonable hash code.
      * 
      * @return The hash code value.
      */
     @Override
     public int hashCode() {
         int result = 1;
         result = (31 * result) + super.hashCode();
         result = (31 * result) + (int) (myTimestamp & 0xFFFFFFFF);
         result = (31 * result) + (int) ((myTimestamp >> 32) & 0xFFFFFFFF);
         return result;
     }
 
     /**
      * {@inheritDoc}
      * <p>
      * Returns a new {@link TimestampElement}.
      * </p>
      */
     @Override
     public TimestampElement withName(final String name) {
         if (getName().equals(name)) {
             return this;
         }
         return new TimestampElement(name, myTimestamp);
     }
 }