/* Copyright 2002-2004 Elliotte Rusty Harold
   
   This library is free software; you can redistribute it and/or modify
   it under the terms of version 2.1 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
   
   You can contact Elliotte Rusty Harold by sending e-mail to
   elharo@metalab.unc.edu. Please include the word "XOM" in the
   subject line. The XOM home page is located at http://www.xom.nu/
*/

package nu.xom;

/**
 *  <p>
 * The <code>Document</code> class represents
 * a complete XML document including its root element,
 * prolog, and epilog.
 * </p>
 * 
 * @author Elliotte Rusty Harold
 * @version 1.0b4
 * 
 */
public class Document extends ParentNode {

    /**
     * <p>
     * Creates a new <code>Document</code> object with the
     * specified root element.
     * </p>
     * 
     * @param root the root element of this document
     * 
     * @throws NullPointerException if <code>root</code> is null
     * @throws MultipleParentException if <code>root</code> already 
     *     has a parent
     */
    public Document(Element root) {
        _insertChild(root, 0);
    }

    
    /**
     * <p>
     * Creates a copy of this document.
     * </p>
     * 
     * @param doc the document to copy
     * 
     * @throws NullPointerException if <code>doc</code> is null
     */
    public Document(Document doc) {

      insertChild(doc.getRootElement().copy(), 0);
      for (int i = 0; i < doc.getChildCount(); i++) {
          Node child = doc.getChild(i);
          if (!(child.isElement())) {
              this.insertChild(child.copy(), i);
          }
      }
      this.actualBaseURI = doc.actualBaseURI;

    }


    final void insertionAllowed(Node child, int position) {
        
        if (child == null) {
            throw new NullPointerException(
             "Tried to insert a null child in the document");
        }
        else if (child.getParent() != null) {
            throw new MultipleParentException("Child already has a parent.");
        }
        else if (child.isComment() || child.isProcessingInstruction()) {
            return;
        }
        else if (child.isDocType()) {
            if (position <= getRootPosition()) {
                DocType oldDocType = getDocType(); 
                if (oldDocType != null) {
                    throw new IllegalAddException(
                      "Tried to insert a second DOCTYPE"
                    );   
                }
                return;
            }
            else {
                throw new IllegalAddException(
                  "Cannot add a document type declaration "
                  + "after the root element"
                );               
            }
        }
        else if (child.isElement()) {
            if (getChildCount() == 0) return;
            else {
                throw new IllegalAddException(
                  "Cannot add a second root element to a Document."
                );
            }
        }
        else {
            throw new IllegalAddException("Cannot add a "
             + child.getClass().getName() + " to a Document.");
        }

    }
    

    private int getRootPosition() {
        
        // This looks like an infinite loop but it isn't
        // because all documents have root elements
        for (int i = 0; ; i++) {
             Node child = getChild(i);
             if (child.isElement()) {
                return i;
             }
         }
        
    }
    
    
    /**
     * <p>
     * Returns this document's document type declaration, 
     * or null if it doesn't have one.
     * </p>
     * 
     * @return the document type declaration
     * 
     * @see #setDocType
     *
     */
    public final DocType getDocType() {
        
        for (int i = 0; i < getChildCount(); i++) {
             Node child = getChild(i);
             if (child.isDocType()) {
                return (DocType) child;
             }
         }
         return null;
         
    }

    
    /**
     * <p>
     * Sets this document's document type declaration.
     * If this document already has a document type declaration,
     * then it's inserted at that position. Otherwise, it's inserted
     * at the beginning of the document.
     * </p>
     * 
     * @param doctype the document type declaration
     * 
     * @throws MultipleParentException if <code>doctype</code> belongs 
     *      to another document
     * @throws NullPointerException if <code>doctype</code> is null
     * 
     */
    public void setDocType(DocType doctype) {
        
        DocType oldDocType = getDocType();
        if (doctype == null) {
            throw new NullPointerException("Null DocType");
        }
        else if (doctype == oldDocType) return; 
        else if (doctype.getParent() != null) {
            throw new MultipleParentException("DocType belongs to another document");
        }
        
        if (oldDocType == null) insertChild(doctype, 0);
        else {
            int position = indexOf(oldDocType);
            children.remove(position);
            children.add(position, doctype);
            oldDocType.setParent(null);
            doctype.setParent(this);
        }
        
    }


    /**
     * <p>
     * Returns this document's root element.
     * This is guaranteed to be non-null.
     * </p>
     * 
     * @return the root element
     */
    public final Element getRootElement() {
        
        // This looks like an infinite loop but it isn't because
        // all documents have root elements.
        for (int i = 0; ; i++) {
             Node child = getChild(i);
             if (child.isElement()) {
                return (Element) child;
             }
         }
        
    }

    
    /**
     * <p>
     * Replaces the current root element with a different root element.
     * </p>
     * 
     * @param root the new root element
     * 
     * @throws MultipleParentException if root has a parent
     * @throws NullPointerException if root is null
     */
    public void setRootElement(Element root) {
        
        Element oldRoot = this.getRootElement(); 
        if (root == oldRoot) return;
        else if (root == null) {
            throw new NullPointerException("Root element cannot be null");
        }
        else if (root.getParent() != null) {
            throw new MultipleParentException(root.getQualifiedName()
              + " already has a parent");
        }
        
        fillInBaseURI(oldRoot);
        int index = indexOf(oldRoot);
        
        oldRoot.setParent(null);
        children.remove(index);
        children.add(index, root);
        root.setParent(this);
        
    }
    
    
    /**
     * <p>
     * Sets the URI from which this document was loaded, and
     * against which relative URLs in this document will be resolved.
     * Setting the base URI to null or the empty string removes any
     * existing base URI.
     * </p>
     * 
     * @param URI the base URI of this document 
     * 
     * @throws MalformedURIException if <code>URI</code> is 
     *     not a legal absolute URI
     */
    public void setBaseURI(String URI) { 
        setActualBaseURI(URI);       
    }
    
    
    /**
     * <p>
     *   Returns the absolute URI from which this document was loaded.
     *   This method returns the empty string if the base URI is not 
     *   known; for instance if the document was created in memory with
     *   a constructor rather than by parsing an existing document.
     * </p>
     * 
     * @return the base URI of this document 
     */
    public final String getBaseURI() {       
        return getActualBaseURI();
    }

    
    /**
     * <p>
     * Removes the child of this document at the specified position.
     * Indexes begin at 0 and count up to one less than the number
     * of children of this document. The root element cannot be 
     * removed. Instead, use <code>setRootElement</code> to replace
     * the existing root element with a different element.
     * </p>
     * 
     * @param position index of the node to remove
     * 
     * @return the node which was removed
     * 
     * @throws IndexOutOfBoundsException if the index is negative or 
     *    greater than the number of children of this document - 1
     * @throws WellformednessException if the index points 
     *     to the root element
     */
    public Node removeChild(int position) {
        
        if (position == getRootPosition()) {
            throw new WellformednessException(
              "Cannot remove the root element"
            );
        }
        return super.removeChild(position);
        
    }

    
    /**
     * <p>
     * Removes the specified child from this document.
     * The root element cannot be removed.
     * Instead, use <code>setRootElement</code> to replace the
     * existing root element with a different element.
     * </p>
     * 
     * @param child node to remove
     * 
     * @return the node which was removed
     * 
     * @throws NoSuchChildException if the node is not a
     *   child of this node
     * @throws WellformednessException if child is the root element
     */
    public Node removeChild(Node child) {
        
        if (child == getRootElement()) {
            throw new WellformednessException(
              "Cannot remove the root element");
        }
        return super.removeChild(child);
        
    }

    
    /**
     * <p>
     * Replaces an existing child with a new child node.
     * If <code>oldChild</code> is not a child of this node, 
     * then a <code>NoSuchChildException</code> is thrown. 
     * The root element can only be replaced by another element.
     * </p>
     * 
     * @param oldChild the node removed from the tree
     * @param newChild the node inserted into the tree
     * 
     * @throws MultipleParentException if <code>newChild</code> already
     *     has a parent
     * @throws NoSuchChildException if <code>oldChild</code> 
     *     is not a child of this node
     * @throws NullPointerException if either argument is null
     * @throws IllegalAddException if <code>newChild</code> is an
     *     attribute or a text node
     * @throws WellformednessException if <code>newChild</code> 
     *     <code>oldChild</code> is an element and 
     *     <code>newChild</code> is not
     */
    public void replaceChild(Node oldChild, Node newChild) {
          
        if (oldChild == getRootElement() 
          && newChild != null && newChild.isElement()) {
            setRootElement((Element) newChild);
        } 
        else if (oldChild == getDocType() 
          && newChild != null && newChild.isDocType()) {
            setDocType((DocType) newChild);
        }
        else {
            super.replaceChild(oldChild, newChild);
        }
        
    }


    /**
     * <p>
     * Returns the value of the document as defined by XPath 1.0.
     * This is the same as the value of the root element, which 
     * is the complete PCDATA content of the root element, without 
     * any tags, comments, or processing instructions after all 
     * entity and character references have been resolved.
     * </p>
     * 
     * @return  value of the root element of this document
     * 
     */
    public final String getValue() {
        return getRootElement().getValue();
    }

    
    /**
     * <p>
     * Returns the actual complete, well-formed XML document as a 
     * <code>String</code>. Significant white space is preserved. 
     * Insignificant white space in tags, the prolog, the epilog, 
     * and the internal DTD subset is not preserved.
     * Entity and character references are not preserved. 
     * The entire document is contained in this one string.
     * </p>
     * 
     * @return a string containing this entire XML document
     */
    public final String toXML() {
    
        StringBuffer result = new StringBuffer();

        // XML declaration
        result.append("<?xml version=\"1.0\"?>\n");
        
        // children
        for (int i = 0; i < getChildCount(); i++) {
            result.append(getChild(i).toXML());
            result.append("\n");  
        }
        
        return result.toString();
        
    }

    
    /**
     * <p>
     * Returns a complete copy of this document.
     * </p>
     * 
     * @return a deep copy of this <code>Document</code> object
     */
    public Node copy() {
        return new Document(this);
    }

    
    boolean isDocument() {
        return true;   
    }

    
    /**
     * <p>
     * Returns a string representation of this document suitable 
     * for debugging and diagnosis. This is <em>not</em>
     * the XML representation of this document.
     * </p>
     * 
     * @return a non-XML string representation of this document
     */
    public final String toString() {
        return "[" + getClass().getName() + ": " 
          + getRootElement().getQualifiedName() + "]"; 
    }

    
}