content: /*
   * OutputElement.java July 2006
   *
   * Copyright (C) 2006, 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.stream;
  
  /**
   * The <code>OutputElement</code> object represents an XML element.  
   * Attributes can be added to this before ant child element has been
   * acquired from it. Once a child element has been acquired the
   * attributes will be written an can no longer be manipulated, the
   * same applies to any text value set for the element.
   * 
   * @author Niall Gallagher
   */ 
  class OutputElement implements OutputNode {
     
     /**
      * Represents the attributes that have been set for the element.
      */         
     private OutputNodeMap table;
  
     /**
      * This is the namespace map that contains the namespaces.
      */ 
     private NamespaceMap scope;
     
     /**
      * Used to write the start tag and attributes for the document.
      */ 
     private NodeWriter writer;
     
     /**
      * This is the parent XML element to this output node.
      */
     private OutputNode parent;
     
     /**
      * This is the namespace reference URI associated with this.
      */ 
     private String reference;
     
     /**
      * This is the comment that has been set on this element.
      */
     private String comment;
     
     /**
      * Represents the value that has been set for the element.
      */ 
     private String value;
  
     /**
      * Represents the name of the element for this output node.
      */ 
     private String name;
     
     /**
      * This is the output mode that this element object is using.
      */
     private Mode mode;
     
     /**
      * Constructor for the <code>OutputElement</code> object. This is
      * used to create an output element that can create elements for
      * an XML document. This requires the writer that is used to 
      * generate the actual document and the name of this node.
      *
      * @param parent this is the parent node to this output node
      * @param writer this is the writer used to generate the file
      * @param name this is the name of the element this represents
      */ 
     public OutputElement(OutputNode parent, NodeWriter writer, String name) {
        this.scope = new PrefixResolver(parent);
        this.table = new OutputNodeMap(this);
        this.mode = Mode.INHERIT;
        this.writer = writer;           
        this.parent = parent;
        this.name = name;
     }     
  
     /**
      * This is used to acquire the prefix for this output node. This 
      * will search its parent nodes until the prefix that is currently
      * in scope is found.  If a prefix is not found in the parent 
      * nodes then a prefix in the current nodes namespace mappings is
      * searched, failing that the prefix returned is null.
      *
      * @return this returns the prefix associated with this node
      */  
     public String getPrefix() {
        return getPrefix(true);
     }
     
     /**
      * This is used to acquire the prefix for this output node. If
      * the output node is an element then this will search its parent
      * nodes until the prefix that is currently in scope is found. 
      * If however this node is an attribute then the hierarchy of 
      * nodes is not searched as attributes to not inherit namespaces.
      *
      * @param inherit if there is no explicit prefix then inherit
      *
      * @return this returns the prefix associated with this node
      */  
     public String getPrefix(boolean inherit) {
        String prefix = scope.getPrefix(reference);
  
        if(inherit) {
           if(prefix == null) {
              return parent.getPrefix();
           }
        }
        return prefix;
     }
     
     /**
      * This is used to acquire the namespace URI reference associated
      * with this node. Although it is recommended that the namespace
      * reference is a URI it does not have to be, it can be any unique
      * identifier that can be used to distinguish the qualified names.
      *
      * @return this returns the namespace URI reference for this
      */
     public String getReference() {
        return reference;
     }
    
     /**
      * This is used to set the reference for the node. Setting the
      * reference implies that the node is a qualified node within the
      * XML document. Both elements and attributes can be qualified.
      * Depending on the prefix set on this node or, failing that, any
      * parent node for the reference, the element will appear in the
      * XML document with that string prefixed to the node name.
      *
      * @param reference this is used to set the reference for the node
      */  
     public void setReference(String reference) {
        this.reference = reference;
     }
    
     /**
      * This returns the <code>NamespaceMap</code> for this node. Only
      * an element can have namespaces, so if this node represents an
      * attribute the elements namespaces will be provided when this is
      * requested. By adding a namespace it becomes in scope for the
      * current element all all child elements of that element.
      *
      * @return this returns the namespaces associated with the node
      */ 
     public NamespaceMap getNamespaces() {
        return scope;
     }
     
     /**
      * This is used to acquire the <code>Node</code> that is the
      * parent of this node. This will return the node that is
      * the direct parent of this node and allows for siblings to
      * make use of nodes with their parents if required.  
      *   
      * @return this returns the parent node for this node
      */
     public OutputNode getParent() {
        return parent;
     }
     
     /**
      * Returns the name of the node that this represents. This is
      * an immutable property and cannot be changed. This will be
      * written as the tag name when this has been committed.
      *  
      * @return returns the name of the node that this represents
      */   
     public String getName() {
        return name;           
     }
    
     /**
      * Returns the value for the node that this represents. This 
      * is a modifiable property for the node and can be changed,
      * however once committed any change will be irrelevant.
      * 
      * @return the name of the value for this node instance
      */   
     public String getValue() {
        return value;
     }
     
     /**
      * This is used to get the text comment for the element. This can
      * be null if no comment has been set. If no comment is set on 
      * the node then no comment will be written to the resulting XML.
      * 
      * @return this is the comment associated with this element
      */
     public String getComment() {
        return comment;
     }
     
     /**
      * This method is used to determine if this node is the root 
      * node for the XML document. The root node is the first node
      * in the document and has no sibling nodes. This is false
      * if the node has a parent node or a sibling node.
      * 
      * @return true if this is the root node within the document
      */
     public boolean isRoot() {
        return writer.isRoot(this);
     }
     
     /**
      * The <code>Mode</code> is used to indicate the output mode
      * of this node. Three modes are possible, each determines
      * how a value, if specified, is written to the resulting XML
      * document. This is determined by the <code>setData</code>
      * method which will set the output to be CDATA or escaped, 
      * if neither is specified the mode is inherited.
      * 
      * @return this returns the mode of this output node object
      */
     public Mode getMode() {
        return mode;
     }
     
     /**
      * This is used to set the output mode of this node to either
      * be CDATA, escaped, or inherited. If the mode is set to data
      * then any value specified will be written in a CDATA block, 
      * if this is set to escaped values are escaped. If however 
      * this method is set to inherited then the mode is inherited
      * from the parent node.
      * 
      * @param mode this is the output mode to set the node to 
      */
     public void setMode(Mode mode) {
        this.mode = mode;
     }
     
     /**
      * This returns a <code>NodeMap</code> which can be used to add
      * nodes to the element before that element has been committed. 
      * Nodes can be removed or added to the map and will appear as
      * attributes on the written element when it is committed.
      *
      * @return returns the node map used to manipulate attributes
      */    
     public OutputNodeMap getAttributes() {
        return table;
     }
     
     /**
      * This is used to set a text comment to the element. This will
      * be written just before the actual element is written. Only a
      * single comment can be set for each output node written. 
      * 
      * @param comment this is the comment to set on the node
      */
     public void setComment(String comment) {
        this.comment = comment;
     }
  
     /**
      * This is used to set a text value to the element. This should
      * be added to the element if the element contains no child
      * elements. If the value cannot be added an exception is thrown.
      * 
      * @param value this is the text value to add to this element
      */    
     public void setValue(String value) {
        this.value = value;
     }
     
     /**
      * This is used to change the name of an output node. This will
      * only affect the name of the node if the node has not yet been
      * committed. If the node is committed then this will not be
      * reflected in the resulting XML generated.
      * 
      * @param name this is the name to change the node to
      */
     public void setName(String name) {
        this.name = name;
     }
     
     /**
      * This is used to set the output mode of this node to either
      * be CDATA or escaped. If this is set to true the any value
      * specified will be written in a CDATA block, if this is set
      * to false the values is escaped. If however this method is
      * never invoked then the mode is inherited from the parent.
      * 
      * @param data if true the value is written as a CDATA block
      */
     public void setData(boolean data) {
        if(data) {
           mode = Mode.DATA;
        } else {
           mode = Mode.ESCAPE;
        }      
     }
  
     /**
      * This method is used for convinience to add an attribute node 
      * to the attribute <code>NodeMap</code>. The attribute added
      * can be removed from the element by useing the node map.
      * 
      * @param name this is the name of the attribute to be added
      * @param value this is the value of the node to be added
      *
      * @return this will return the attribute that was just set
      */    
     public OutputNode setAttribute(String name, String value) {
        return table.put(name, value);
     }
  
     /**
      * This is used to create a child element within the element that
      * this object represents. When a new child is created with this
      * method then the previous child is committed to the document.
      * The created <code>OutputNode</code> object can be used to add
      * attributes to the child element as well as other elements.
      *
      * @param name this is the name of the child element to create
      */    
     public OutputNode getChild(String name) throws Exception {
        return writer.writeElement(this, name);
     }
     
     /**
      * This is used to remove any uncommitted changes. Removal of an
      * output node can only be done if it has no siblings and has
      * not yet been committed. If the node is committed then this 
      * will throw an exception to indicate that it cannot be removed. 
      * 
      * @throws Exception thrown if the node cannot be removed
      */
     public void remove() throws Exception {
        writer.remove(this);
     }
     
     /**
      * This will commit this element and any uncommitted elements
      * elements that are decendents of this node. For instance if
      * any child or grand child remains open under this element
      * then those elements will be closed before this is closed.
      *
      * @throws Exception this is thrown if there is an I/O error
      */ 
     public void commit() throws Exception{
        writer.commit(this);
     }
    
     /**
      * This is used to determine whether this node has been committed.
      * If the node is committed then no further child elements can
      * be created from this node instance. A node is considered to
      * be committed if a parent creates another child element or if
      * the <code>commit</code> method is invoked.
      *
      * @return true if the node has been committed
      */  
     public boolean isCommitted() {
        return writer.isCommitted(this);
     }
     
     /**
      * This is the string representation of the element. It is
      * used for debugging purposes. When evaluating the element
      * the to string can be used to print out the element name.
      * 
      * @return this returns a text description of the element
      */
     public String toString() {
        return String.format("element %s", name);
     }
  }
  