content: /*
   * VersionLabel.java July 2008
   *
   * Copyright (C) 2008, 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 com.aliyun.odps.simpleframework.xml.core;
  
  import com.aliyun.odps.simpleframework.xml.Version;
  import com.aliyun.odps.simpleframework.xml.strategy.Type;
  import com.aliyun.odps.simpleframework.xml.stream.Format;
  import com.aliyun.odps.simpleframework.xml.stream.Style;
  import java.lang.annotation.Annotation;
  
  /**
   * The <code>VersionLabel</code> object is used convert any double
   * retrieved from an XML attribute to a version revision. The version
   * is used to determine how to perform serialization of a composite
   * by determining version compatibility. 
   * 
   * @author Niall Gallagher
   */
  class VersionLabel extends TemplateLabel {
     
     /**
      * This is the decorator that is associated with the attribute.
      */
     private Decorator decorator;
  
     /**
      * This contains the details of the annotated contact object.
      */
     private Introspector detail;
     
     /**
      * This is the path that is used to represent this version.
      */
     private Expression path;
     
     /**
      * Represents the annotation used to label the field.
      */
     private Version label;
     
     /**
      * This is used to format the paths associated with this.
      */ 
     private Format format;
     
     /**
      * This is the type that the field object references. 
      */
     private Class type;
     
     /**
      * This is the name of the element for this label instance.
      */
     private String name;
     
     /**
      * This is used to determine if the attribute is required.
      */
     private boolean required;
     
     /**
      * Constructor for the <code>VersionLabel</code> object. This is
      * used to create a label that can convert from a double to an
      * XML attribute and vice versa. This requires the annotation and
      * contact extracted from the XML schema class.
      * 
      * @param contact this is the field from the XML schema class
      * @param label represents the annotation for the field
      * @param format this is the format used to style the paths
      */
     public VersionLabel(Contact contact, Version label, Format format) {
        this.detail = new Introspector(contact, this, format);
        this.decorator = new Qualifier(contact);
        this.required = label.required();
        this.type = contact.getType();
        this.name = label.name();      
        this.format = format;
        this.label = label;
     }   
     
     /**
      * This is used to acquire the <code>Decorator</code> for this.
      * A decorator is an object that adds various details to the
      * node without changing the overall structure of the node. For
      * example comments and namespaces can be added to the node with
      * a decorator as they do not affect the deserialization.
      * 
      * @return this returns the decorator associated with this
      */
     public Decorator getDecorator() throws Exception {
        return decorator;
     }
     
     /**
      * Creates a <code>Converter</code> that can convert an attribute
      * to a double value. This requires the context object used for
      * the current instance of XML serialization being performed.
      * 
      * @param context this is context object used for serialization
      * 
      * @return this returns the converted for this attribute object
      */
     public Converter getConverter(Context context) throws Exception {
        String ignore = getEmpty(context);
        Type type = getContact();
        
        if(!context.isFloat(type)) {
           throw new AttributeException("Cannot use %s to represent %s", label, type);
        }
        return new Primitive(context, type, ignore);
     }
     
     /**
      * This is used to provide a configured empty value used when the
      * annotated value is null. This ensures that XML can be created
      * with required details regardless of whether values are null or
      * not. It also provides a means for sensible default values.
      * 
      * @param context this is the context object for the serialization
      * 
      * @return this returns the string to use for default values
      */
     public String getEmpty(Context context) {
        return null;
     }
     
     /**
      * This is used to acquire the name of the element or attribute
      * that is used by the class schema. The name is determined by
      * checking for an override within the annotation. If it contains
      * a name then that is used, if however the annotation does not
      * specify a name the the field or method name is used instead.
      *
      * @return returns the name that is used for the XML property
      */
     public String getName() throws Exception {
        Style style = format.getStyle();
        String name = detail.getName();
        
        return style.getAttribute(name);
     }
     
     /**
      * This is used to acquire the path of the element or attribute
      * that is used by the class schema. The path is determined by
      * acquiring the XPath expression and appending the name of the
      * label to form a fully qualified path.
      * 
      * @return returns the path that is used for the XML property
      */
     public String getPath() throws Exception {
        Expression path = getExpression();
        String name = getName();
        
        return path.getAttribute(name);  
     }
     
     /**
      * This method is used to return an XPath expression that is 
      * used to represent the position of this label. If there is no
      * XPath expression associated with this then an empty path is
      * returned. This will never return a null expression.
      * 
      * @return the XPath expression identifying the location
      */
     public Expression getExpression() throws Exception {
        if(path == null) {
           path = detail.getExpression();
        }
        return path;
     }
     
     /**
      * This acquires the annotation associated with this label. This
      * is typically the annotation acquired from the field or method.
      * However, in the case of unions this will return the actual
      * annotation within the union group that this represents.
      * 
      * @return this returns the annotation that this represents
      */
     public Annotation getAnnotation() {
        return label;
     }
     
     /**
      * This is used to acquire the name of the element or attribute
      * as taken from the annotation. If the element or attribute
      * explicitly specifies a name then that name is used for the
      * XML element or attribute used. If however no overriding name
      * is provided then the method or field is used for the name. 
      * 
      * @return returns the name of the annotation for the contact
      */
     public String getOverride(){
        return name;
     }
     
     /**
      * This is used to acquire the contact object for this label. The 
      * contact retrieved can be used to set any object or primitive that
      * has been deserialized, and can also be used to acquire values to
      * be serialized in the case of object persistence. All contacts
      * that are retrieved from this method will be accessible. 
      * 
      * @return returns the contact that this label is representing
      */   
     public Contact getContact() {
        return detail.getContact();
     }
     
     /**
      * This acts as a convenience method used to determine the type of
      * the contact this represents. This will be a primitive type of a
      * primitive type from the <code>java.lang</code> primitives.
      * 
      * @return this returns the type of the contact class
      */  
     public Class getType() {
        return type;
     }
     
     /**
      * This method is used to determine if the label represents an
      * attribute. This is used to style the name so that elements
      * are styled as elements and attributes are styled as required.
      * 
      * @return this is used to determine if this is an attribute
      */
     public boolean isAttribute() {
        return true;
     }
     
     /**
      * This is used to determine whether the attribute is required. 
      * This ensures that if an attribute is missing from a document
      * that deserialization can continue. Also, in the process of
      * serialization, if a value is null it does not need to be 
      * written to the resulting XML document.
      * 
      * @return true if the label represents a some required data
      */  
     public boolean isRequired() {
        return required;
     }
     
     /**
      * Because the attribute can contain only simple text values it
      * is never required to specified as anything other than text.
      * Therefore this will always return false as CDATA does not
      * apply to the attribute values.
      *
      * @return this will always return false for XML attributes
      */
     public boolean isData() {
        return false;
     }
     
     /**
      * This is used to describe the annotation and method or field
      * that this label represents. This is used to provide error
      * messages that can be used to debug issues that occur when
      * processing a method. This will provide enough information
      * such that the problem can be isolated correctly. 
      * 
      * @return this returns a string representation of the label
      */
     public String toString() {
        return detail.toString();
     }
  }
  