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/*
 * PrimitiveValue.java July 2007
 *
 * Copyright (C) 2007, Niall Gallagher 
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General 
 * Public License along with this library; if not, write to the 
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
 * Boston, MA  02111-1307  USA
 */

package org.simpleframework.xml.load;

import org.simpleframework.xml.stream.InputNode;
import org.simpleframework.xml.stream.OutputNode;
import org.simpleframework.xml.stream.Style;


/**
 * The PrimitiveValue is used to serialize a primitive 
 * value to and from a node. If a value name is provided in the 
 * annotation then this will serialize and deserialize that value 
 * with the given name, if the value is primitive and no name is
 * specified then the value is written inline, that is without any
 * enclosing XML element.
 *  * 
 *    <entry key="one">example one</entry>
 *    <entry key="two">example two</entry>
 *    <entry key="three">example three</entry>    
 * 
 * 
 * Allowing the value to be written as either an XML element or an
 * inline text value enables a more flexible means for representing 
 * the value. The only condition for having an inline value is that
 * the key is specified as an attribute in the annotation.
 * 
 * @author Niall Gallagher
 * 
 * @see org.simpleframework.xml.load.CompositeMap
 */
class PrimitiveValue implements Converter {
   
   /**
    * The primitive factory used to resolve the primitive to a string.
    */
   private final PrimitiveFactory factory;
   
   /**
    * The primitive converter used to read the value from the node.
    */
   private final Primitive primitive;
   
   /**
    * This is the style used to style the XML names for the value.
    */
   private final Style style;
   
   /**
    * The entry object contains the details on how to write the value.
    */
   private final Entry entry; 
   
   /**
    * Represents the primitive type the value is serialized to and from.
    */
   private final Class type;
   
   /**
    * Constructor for the PrimitiveValue object. This is 
    * used to create the value object which converts the map value to 
    * an instance of the value type. This can also resolve references. 
    * 
    * @param root this is the context object used for serialization
    * @param entry this is the entry object that describes entries
    * @param type this is the type that this converter deals with
    */   
   public PrimitiveValue(Source root, Entry entry, Class type) {
      this.factory = new PrimitiveFactory(root, type);
      this.primitive = new Primitive(root, type);
      this.style = root.getStyle();
      this.entry = entry;
      this.type = type;
   }
   
   /**
    * This method is used to read the value value from the node. The 
    * value read from the node is resolved using the template filter.
    * If the value value can not be found according to the annotation
    * attributes then an exception is thrown.
    * 
    * @param node this is the node to read the value object from
    * 
    * @return this returns the value deserialized from the node
    */ 
   public Object read(InputNode node) throws Exception {
      String name = entry.getValue();
      
      if(name == null) {
         name = Factory.getName(type);
      }
      if(entry.isInline()) {
         return primitive.read(node);
      }
      return read(node, name);
   }
   
   /**
    * This method is used to read the value value from the node. The 
    * value read from the node is resolved using the template filter.
    * If the value value can not be found according to the annotation
    * attributes then null is assumed and returned.
    * 
    * @param node this is the node to read the value object from
    * @param key this is the name of the value XML element
    * 
    * @return this returns the value deserialized from the node
    */ 
   private Object read(InputNode node, String key) throws Exception {
      String name = style.getAttribute(key);
      InputNode child = node.getNext(name);
      
      if(child == null) {
         return null;        
      }
      return primitive.read(child);      
   }
   
   /**
    * This method is used to read the value value from the node. The 
    * value read from the node is resolved using the template filter.
    * If the value value can not be found according to the annotation
    * attributes then null is assumed and the node is valid.
    * 
    * @param node this is the node to read the value object from
    * 
    * @return this returns true if the primitive key is valid
    */ 
   public boolean validate(InputNode node) throws Exception {
      String name = entry.getValue();
      
      if(name == null) {
         name = Factory.getName(type);
      }
      return validate(node, name);
   }
   
   /**
    * This method is used to read the value value from the node. The 
    * value read from the node is resolved using the template filter.
    * If the value value can not be found according to the annotation
    * attributes then null is assumed and the node is valid.
    *  
    * @param node this is the node to read the value object from
    * @param key this is the name of the node to be validated
    * 
    * @return this returns true if the primitive key is valid
    */    
   private boolean validate(InputNode node, String key) throws Exception {
      String name = style.getAttribute(key);
      
      if(!entry.isInline()) {
         node = node.getNext(name);
      
         if(node == null) {
            return true;        
         }
      }
      return primitive.validate(node);
   }

   /**
    * This method is used to write the value to the specified node.
    * The value written to the node can be an attribute or an element
    * depending on the annotation attribute values. This method will
    * maintain references for serialized elements.
    * 
    * @param node this is the node that the value is written to
    * @param item this is the item that is to be written
    */
   public void write(OutputNode node, Object item) throws Exception {
      String name = entry.getValue();
      
      if(name == null) {
         name = Factory.getName(type);
      } 
      write(node, item, name);
   }
   
   /**
    * This method is used to write the value to the specified node.
    * The value written to the node can be an attribute or an element
    * depending on the annotation attribute values. This method will
    * maintain references for serialized elements.
    * 
    * @param node this is the node that the value is written to
    * @param item this is the item that is to be written
    * @param key this is the name of the node to be created
    */   
   private void write(OutputNode node, Object item, String key) throws Exception {
      String name = style.getAttribute(key);
      
      if(!entry.isInline()) {
         node = node.getChild(name);        
      }
      if(item != null) {        
         if(!isOverridden(node, item)) {
            primitive.write(node, item);
         }
      }
   }
   
   /**
    * This is used to determine whether the specified value has been
    * overriden by the strategy. If the item has been overridden
    * then no more serialization is require for that value, this is
    * effectively telling the serialization process to stop writing.
    * 
    * @param node the node that a potential override is written to
    * @param value this is the object instance to be serialized
    * 
    * @return returns true if the strategy overrides the object
    */
   private boolean isOverridden(OutputNode node, Object item) throws Exception{
      return factory.setOverride(type, item, node);
   }

}