/*
 * Copyright (c) 2002 World Wide Web Consortium,
 * (Massachusetts Institute of Technology, Institut National de
 * Recherche en Informatique et en Automatique, Keio University). All
 * Rights Reserved. This program is distributed under the W3C's Software
 * Intellectual Property License. This program 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 W3C License http://www.w3.org/Consortium/Legal/ for more details.
 */

package org.w3c.dom.xpath;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

/**
 * The <code>XPathResult</code> interface represents the result of the 
 * evaluation of an XPath expression within the context of a particular 
 * node. Since evaluation of an XPath expression can result in various 
 * result types, this object makes it possible to discover and manipulate 
 * the type and value of the result.Should there be a flag on the result to 
 * say whether an iteration has become invalid?Yes.Added the boolean 
 * attribute <code>invalidIteratorState</code>Should there be a reset method 
 * on the result in case someone wants to iterate the result multiple times?
 * It may be more trouble than it is worth, because the user can request a 
 * new query. See if there are use cases.It might be better to consolidate 
 * the interfaces and just move the snapshot and iterator functions to the 
 * result object.Yes.The result of the consolidation looks good and unless 
 * there are great objections, this is how it will be.There is concern that 
 * the result cannot represent multiple strings, which is a possible result 
 * of XPath 2.0. on them?No change.This is not part of the XPath 1.0 data 
 * model. We cannot plan well for the XPath 2.0 data model at this point. 
 * Most likely a new API will be required for XPath 2.0
 * <p>See also the <a href='http://www.w3.org/TR/2002/WD-DOM-Level-3-XPath-20020328'>Document Object Model (DOM) Level 3 XPath Specification</a>.
 */
public interface XPathResult {
    // XPathResultType
    /**
     * This code does not represent a specific type. An evaluation of an XPath 
     * expression will never produce this type. If this type is requested, 
     * then the evaluation returns whatever type naturally results from 
     * evaluation of the expression. 
     * <br>If the natural result is a node set when <code>ANY_TYPE</code> was 
     * requested, then <code>UNORDERED_NODE_ITERATOR_TYPE</code> is always 
     * the resulting type. Any other representation of a node set must be 
     * explicitly requested.
     */
    public static final short ANY_TYPE                  = 0;
    /**
     * The result is a number as defined by . Document modification does not 
     * invalidate the number, but may mean that reevaluation would not yield 
     * the same number.
     */
    public static final short NUMBER_TYPE               = 1;
    /**
     * The result is a string as defined by . Document modification does not 
     * invalidate the string, but may mean that the string no longer 
     * corresponds to the current document.
     */
    public static final short STRING_TYPE               = 2;
    /**
     * The result is a boolean as defined by . Document modification does not 
     * invalidate the boolean, but may mean that reevaluation would not 
     * yield the same boolean.
     */
    public static final short BOOLEAN_TYPE              = 3;
    /**
     * The result is a node set as defined by  that will be accessed 
     * iteratively, which may not produce nodes in a particular order. 
     * Document modification invalidates the iteration.
     * <br>This is the default type returned if the result is a node set and 
     * <code>ANY_TYPE</code> is requested.
     */
    public static final short UNORDERED_NODE_ITERATOR_TYPE = 4;
    /**
     * The result is a node set as defined by  that will be accessed 
     * iteratively, which will produce document-ordered nodes. Document 
     * modification invalidates the iteration.
     */
    public static final short ORDERED_NODE_ITERATOR_TYPE = 5;
    /**
     * The result is a node set as defined by  that will be accessed as a 
     * snapshot list of nodes that may not be in a particular order. 
     * Document modification does not invalidate the snapshot but may mean 
     * that reevaluation would not yield the same snapshot and nodes in the 
     * snapshot may have been altered, moved, or removed from the document.
     */
    public static final short UNORDERED_NODE_SNAPSHOT_TYPE = 6;
    /**
     * The result is a node set as defined by  that will be accessed as a 
     * snapshot list of nodes that will be in original document order. 
     * Document modification does not invalidate the snapshot but may mean 
     * that reevaluation would not yield the same snapshot and nodes in the 
     * snapshot may have been altered, moved, or removed from the document.
     */
    public static final short ORDERED_NODE_SNAPSHOT_TYPE = 7;
    /**
     * The result is a node set as defined by  and will be accessed as a 
     * single node, which may be <code>null</code>if the node set is empty. 
     * Document modification does not invalidate the node, but may mean that 
     * the result node no longer corresponds to the current document. This 
     * is a convenience that permits optimization since the implementation 
     * can stop once any node in the in the resulting set has been found.
     * <br>If there are more than one node in the actual result, the single 
     * node returned may not be the first in document order.
     */
    public static final short ANY_UNORDERED_NODE_TYPE   = 8;
    /**
     * The result is a node set as defined by  and will be accessed as a 
     * single node, which may be <code>null</code> if the node set is empty. 
     * Document modification does not invalidate the node, but may mean that 
     * the result node no longer corresponds to the current document. This 
     * is a convenience that permits optimization since the implementation 
     * can stop once the first node in document order of the resulting set 
     * has been found.
     * <br>If there are more than one node in the actual result, the single 
     * node returned will be the first in document order.
     */
    public static final short FIRST_ORDERED_NODE_TYPE   = 9;

    /**
     * A code representing the type of this result, as defined by the type 
     * constants.
     */
    public short getResultType();

    /**
     * The value of this number result.
     * @exception XPathException
     *   TYPE_ERR: raised if <code>resultType</code> is not 
     *   <code>NUMBER_TYPE</code>.
     */
    public double getNumberValue()
                             throws XPathException;

    /**
     * The value of this string result.
     * @exception XPathException
     *   TYPE_ERR: raised if <code>resultType</code> is not 
     *   <code>STRING_TYPE</code>.
     */
    public String getStringValue()
                             throws XPathException;

    /**
     * The value of this boolean result.
     * @exception XPathException
     *   TYPE_ERR: raised if <code>resultType</code> is not 
     *   <code>BOOLEAN_TYPE</code>.
     */
    public boolean getBooleanValue()
                             throws XPathException;

    /**
     * The value of this single node result, which may be <code>null</code>.
     * @exception XPathException
     *   TYPE_ERR: raised if <code>resultType</code> is not 
     *   <code>ANY_UNORDERED_NODE_TYPE</code> or 
     *   <code>FIRST_ORDERED_NODE_TYPE</code>.
     */
    public Node getSingleNodeValue()
                             throws XPathException;

    /**
     * Signifies that the iterator has become invalid. True if 
     * <code>resultType</code> is <code>UNORDERED_NODE_ITERATOR_TYPE</code> 
     * or <code>ORDERED_NODE_ITERATOR_TYPE</code> and the document has been 
     * modified since this result was returned.
     */
    public boolean getInvalidIteratorState();

    /**
     * The number of nodes in the result snapshot. Valid values for 
     * snapshotItem indices are <code>0</code> to 
     * <code>snapshotLength-1</code> inclusive.
     * @exception XPathException
     *   TYPE_ERR: raised if <code>resultType</code> is not 
     *   <code>UNORDERED_NODE_SNAPSHOT_TYPE</code> or 
     *   <code>ORDERED_NODE_SNAPSHOT_TYPE</code>.
     */
    public int getSnapshotLength()
                             throws XPathException;

    /**
     * Iterates and returns the next node from the node set or 
     * <code>null</code>if there are no more nodes.
     * @return Returns the next node.
     * @exception XPathException
     *   TYPE_ERR: raised if <code>resultType</code> is not 
     *   <code>UNORDERED_NODE_ITERATOR_TYPE</code> or 
     *   <code>ORDERED_NODE_ITERATOR_TYPE</code>.
     * @exception DOMException
     *   INVALID_STATE_ERR: The document has been mutated since the result was 
     *   returned.
     */
    public Node iterateNext()
                            throws XPathException, DOMException;

    /**
     * Returns the <code>index</code>th item in the snapshot collection. If 
     * <code>index</code> is greater than or equal to the number of nodes in 
     * the list, this method returns <code>null</code>. Unlike the iterator 
     * result, the snapshot does not become invalid, but may not correspond 
     * to the current document if it is mutated.
     * @param index Index into the snapshot collection.
     * @return The node at the <code>index</code>th position in the 
     *   <code>NodeList</code>, or <code>null</code> if that is not a valid 
     *   index.
     * @exception XPathException
     *   TYPE_ERR: raised if <code>resultType</code> is not 
     *   <code>UNORDERED_NODE_SNAPSHOT_TYPE</code> or 
     *   <code>ORDERED_NODE_SNAPSHOT_TYPE</code>.
     */
    public Node snapshotItem(int index)
                             throws XPathException;

}