/*
 * DateTransform.java May 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * 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 org.simpleframework.xml.transform;

import java.util.Date;

/**
 * The <code>DateTransform</code> object is used to transform date
 * values to and from string representations, which will be inserted
 * in the generated XML document as the value place holder. The
 * value must be readable and writable in the same format. Fields
 * and methods annotated with the XML attribute annotation will use
 * this to persist and retrieve the value to and from the XML source.
 * <pre>
 * 
 *    &#64;Attribute
 *    private Date date;
 *    
 * </pre>
 * As well as the XML attribute values using transforms, fields and
 * methods annotated with the XML element annotation will use this.
 * Aside from the obvious difference, the element annotation has an
 * advantage over the attribute annotation in that it can maintain
 * any references using the <code>CycleStrategy</code> object. 
 * 
 * @author Niall Gallagher
 */
class DateTransform<T extends Date> implements Transform<T> {
   
   /**
    * This represents the constructor used for creating the date.
    */
   private final DateFactory<T> factory;

   /**
    * Constructor for the <code>DateTransform</code> object. This is
    * used to create a transform using a specified date format. The
    * format should typically contain enough information to create
    * the date using a different locale or time zone between read and
    * write operations.
    * 
    * @param type this is the type of date to be created by this
    */
   public DateTransform(Class<T> type) throws Exception {
      this.factory = new DateFactory<T>(type);
   }
   
   /**
    * This method is used to convert the string value given to an
    * appropriate representation. This is used when an object is
    * being deserialized from the XML document and the value for
    * the string representation is required.
    * 
    * @param text the string representation of the date value 
    * 
    * @return this returns an appropriate instanced to be used
    */
   public synchronized T read(String text) throws Exception {      
      Date date = DateType.getDate(text);
      Long time = date.getTime();
      
      return factory.getInstance(time);
   }
   
   /**
    * This method is used to convert the provided value into an XML
    * usable format. This is used in the serialization process when
    * there is a need to convert a field value in to a string so 
    * that that value can be written as a valid XML entity.
    * 
    * @param date this is the value to be converted to a string
    * 
    * @return this is the string representation of the given date
    */
   public synchronized String write(T date) throws Exception {
      return DateType.getText(date);     
   }
}
