/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/*

 * Copyright 2003-2004 The Apache Software Foundation.

 *

 * 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.

 */

/*

 * $Id: NamespaceMappings.java,v 1.2.4.1 2005/09/15 08:15:19 suresh_emailid Exp $

 */

package com.sun.org.apache.xml.internal.serializer;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Stack;

import org.xml.sax.ContentHandler;

import org.xml.sax.SAXException;

/**

 * This class keeps track of the currently defined namespaces. Conceptually the

 * prefix/uri/depth triplets are pushed on a stack pushed on a stack. The depth

 * indicates the nesting depth of the element for which the mapping was made.

 *

 * <p>For example:

 * <pre>

 * <chapter xmlns:p1="def">

 *   <paragraph xmlns:p2="ghi">

 *      <sentance xmlns:p3="jkl">

 *      </sentance>

 *    </paragraph>

 *    <paragraph xlmns:p4="mno">

 *    </paragraph>

 * </chapter>

 * </pre>

 *

 * When the <chapter> element is encounted the prefix "p1" associated with uri

 * "def" is pushed on the stack with depth 1.

 * When the first <paragraph> is encountered "p2" and "ghi" are pushed with

 * depth 2.

 * When the <sentance> is encountered "p3" and "jkl" are pushed with depth 3.

 * When </sentance> occurs the popNamespaces(3) will pop "p3"/"jkl" off the

 * stack.  Of course popNamespaces(2) would pop anything with depth 2 or

 * greater.

 *

 * So prefix/uri pairs are pushed and poped off the stack as elements are

 * processed.  At any given moment of processing the currently visible prefixes

 * are on the stack and a prefix can be found given a uri, or a uri can be found

 * given a prefix.

 *

 * This class is public only because it is used by Xalan. It is not a public API

 *

 * @xsl.usage internal

 */

public class NamespaceMappings

{

    /**

     * This member is continually incremented when new prefixes need to be

     * generated. ("ns0"  "ns1" ...)

     */

    private int count;

    /**

     * Each entry (prefix) in this hashmap points to a Stack of URIs

     * This maps a prefix (String) to a Stack of prefix mappings.

     * All mappings in that retrieved stack have the same prefix,

     * though possibly different URI's or depths. Such a stack must have

     * mappings at deeper depths push later on such a stack.  Mappings pushed

     * earlier on the stack will have smaller values for MappingRecord.m_declarationDepth.

     */

    private HashMap m_namespaces = new HashMap();

    /**

     * The top of this stack contains the MapRecord

     * of the last declared a namespace.

     * Used to know how many prefix mappings to pop when leaving

     * the current element depth.

     * For every prefix mapping the current element depth is

     * pushed on this stack.

     * That way all prefixes pushed at the current depth can be

     * removed at the same time.

     * Used to ensure prefix/uri map scopes are closed correctly

     *

     */

    private Stack m_nodeStack = new Stack();

    private static final String EMPTYSTRING = "";

    private static final String XML_PREFIX = "xml"; // was "xmlns"

    /**

     * Default constructor

     * @see java.lang.Object#Object()

     */

    public NamespaceMappings()

    {

        initNamespaces();

    }

    /**

     * This method initializes the namespace object with appropriate stacks

     * and predefines a few prefix/uri pairs which always exist.

     */

    private void initNamespaces()

    {

        // Define the default namespace (initially maps to "" uri)

        Stack stack;

        m_namespaces.put(EMPTYSTRING, stack = new Stack());

        stack.push(new MappingRecord(EMPTYSTRING,EMPTYSTRING,0));

        m_namespaces.put(XML_PREFIX, stack = new Stack());

        stack.push(new MappingRecord( XML_PREFIX,

            "http://www.w3.org/XML/1998/namespace",0));

        m_nodeStack.push(new MappingRecord(null,null,-1));

    }

    /**

     * Use a namespace prefix to lookup a namespace URI.

     *

     * @param prefix String the prefix of the namespace

     * @return the URI corresponding to the prefix

     */

    public String lookupNamespace(String prefix)

    {

        final Stack stack = (Stack) m_namespaces.get(prefix);

        return stack != null && !stack.isEmpty() ?

            ((MappingRecord) stack.peek()).m_uri : null;

    }

    MappingRecord getMappingFromPrefix(String prefix) {

        final Stack stack = (Stack) m_namespaces.get(prefix);

        return stack != null && !stack.isEmpty() ?

            ((MappingRecord) stack.peek()) : null;

    }

    /**

     * Given a namespace uri, and the namespaces mappings for the

     * current element, return the current prefix for that uri.

     *

     * @param uri the namespace URI to be search for

     * @return an existing prefix that maps to the given URI, null if no prefix

     * maps to the given namespace URI.

     */

    public String lookupPrefix(String uri)

    {

        String foundPrefix = null;

        Iterator<String> itr = m_namespaces.keySet().iterator();

        while (itr.hasNext()) {

            String prefix = itr.next();

            String uri2 = lookupNamespace(prefix);

            if (uri2 != null && uri2.equals(uri))

            {

                foundPrefix = prefix;

                break;

            }

        }

        return foundPrefix;

    }

    MappingRecord getMappingFromURI(String uri)

    {

        MappingRecord foundMap = null;

        Iterator<String> itr = m_namespaces.keySet().iterator();

        while (itr.hasNext())

        {

            String prefix = itr.next();

            MappingRecord map2 = getMappingFromPrefix(prefix);

            if (map2 != null && (map2.m_uri).equals(uri))

            {

                foundMap = map2;

                break;

            }

        }

        return foundMap;

    }

    /**

     * Undeclare the namespace that is currently pointed to by a given prefix

     */

    boolean popNamespace(String prefix)

    {

        // Prefixes "xml" and "xmlns" cannot be redefined

        if (prefix.startsWith(XML_PREFIX))

        {

            return false;

        }

        Stack stack;

        if ((stack = (Stack) m_namespaces.get(prefix)) != null)

        {

            stack.pop();

            return true;

        }

        return false;

    }

    /**

     * Declare a mapping of a prefix to namespace URI at the given element depth.

     * @param prefix a String with the prefix for a qualified name

     * @param uri a String with the uri to which the prefix is to map

     * @param elemDepth the depth of current declaration

     */

    boolean pushNamespace(String prefix, String uri, int elemDepth)

    {

        // Prefixes "xml" and "xmlns" cannot be redefined

        if (prefix.startsWith(XML_PREFIX))

        {

            return false;

        }

        Stack stack;

        // Get the stack that contains URIs for the specified prefix

        if ((stack = (Stack) m_namespaces.get(prefix)) == null)

        {

            m_namespaces.put(prefix, stack = new Stack());

        }

        if (!stack.empty() && uri.equals(((MappingRecord)stack.peek()).m_uri))

        {

            return false;

        }

        MappingRecord map = new MappingRecord(prefix,uri,elemDepth);

        stack.push(map);

        m_nodeStack.push(map);

        return true;

    }

    /**

     * Pop, or undeclare all namespace definitions that are currently

     * declared at the given element depth, or deepter.

     * @param elemDepth the element depth for which mappings declared at this

     * depth or deeper will no longer be valid

     * @param saxHandler The ContentHandler to notify of any endPrefixMapping()

     * calls.  This parameter can be null.

     */

    void popNamespaces(int elemDepth, ContentHandler saxHandler)

    {

        while (true)

        {

            if (m_nodeStack.isEmpty())

                return;

            MappingRecord map = (MappingRecord)(m_nodeStack.peek());

            int depth = map.m_declarationDepth;

            if (depth < elemDepth)

                return;

            /* the depth of the declared mapping is elemDepth or deeper

             * so get rid of it

             */

            map = (MappingRecord) m_nodeStack.pop();

            final String prefix = map.m_prefix;

            popNamespace(prefix);

            if (saxHandler != null)

            {

                try

                {

                    saxHandler.endPrefixMapping(prefix);

                }

                catch (SAXException e)

                {

                    // not much we can do if they aren't willing to listen

                }

            }

        }

    }

    /**

     * Generate a new namespace prefix ( ns0, ns1 ...) not used before

     * @return String a new namespace prefix ( ns0, ns1, ns2 ...)

     */

    public String generateNextPrefix()

    {

        return "ns" + (count++);

    }

    /**

     * This method makes a clone of this object.

     *

     */

    public Object clone() throws CloneNotSupportedException {

        NamespaceMappings clone = new NamespaceMappings();

        clone.m_nodeStack = (Stack) m_nodeStack.clone();

        clone.m_namespaces = (HashMap) m_namespaces.clone();

        clone.count = count;

        return clone;

    }

    final void reset()

    {

        this.count = 0;

        this.m_namespaces.clear();

        this.m_nodeStack.clear();

        initNamespaces();

    }

    class MappingRecord {

        final String m_prefix;  // the prefix

        final String m_uri;     // the uri

        // the depth of the element where declartion was made

        final int m_declarationDepth;

        MappingRecord(String prefix, String uri, int depth) {

            m_prefix = prefix;

            m_uri = uri;

            m_declarationDepth = depth;

        }

    }

}