/*

 * 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: ElemContext.java,v 1.2.4.1 2005/09/15 08:15:15 suresh_emailid Exp $

 */

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

/**

 * This class is a stack frame that consists of

 * information about the element currently being processed

 * by a serializer. Consider this example:

 * <pre>

 *   <A>

 *     <B1>

 *     </B1>

 *     <B2>

 *     </B2>

 *   <A>

 * </pre>

 *

 * A stack frame will be pushed for "A" at depth 1,

 * then another one for "B1" at depth 2.

 * Then "B1" stackframe is popped.  When the stack frame for "B2" is

 * pushed, this implementation re-uses the old stack fram object used

 * by "B1" to be efficient at not creating too many of these object.

 *

 * This is by no means a public class, and neither are its fields or methods,

 * they are all helper fields for a serializer.

 *

 * The purpose of this class is to be more consistent with pushing information

 * when a new element is being serialized and more quickly restoring the old

 * information about the parent element with a simple pop() when the

 * child element is done.  Previously there was some redundant and error-prone

 * calculations going on to retore information.

 *

 * @xsl.usage internal

 */

final class ElemContext

{

    // Fields that form the context of the element

    /**

     * The nesting depth of the element inside other elements.

     */

    final int m_currentElemDepth;

    /** HTML field, the element description of the HTML element */

    ElemDesc m_elementDesc = null;

    /**

     * The local name of the element.

     */

    String m_elementLocalName = null;

    /**

     * The fully qualified name of the element (with prefix, if any).

     */

    String m_elementName = null;

    /**

     * The URI of the element.

     */

    String m_elementURI = null;

    /** If the element is in the cdata-section-names list

     * then the value is true. If it is true the text children of the element

     * should be output in CDATA section blocks.

     */

    boolean m_isCdataSection;

    /** True if the current element has output escaping disabled.

     * This is true for SCRIPT and STYLE elements.

     */

    boolean m_isRaw = false;

    /** The next element "stack frame". This value will only be

     * set once as deeper stack frames are not deleted when popped off,

     * but are rather re-used when a push is required.

     *

     * This makes for very fast pushing and popping of stack frames

     * because very few stack frame objects are ever created, they are

     * mostly re-used.  This re-use saves object creation but it also means

     * that connections between the frames via m_next and m_prev

     * never changes either. Just the contents of the frames change

     * as they are re-used. Only the reference to the current stack frame, which

     * is held by the serializer is changed via a quick pop() or push().

     */

    private ElemContext m_next;

    /** The previous element "stack frame". */

    final ElemContext m_prev;

    /**

     * Set to true when a start tag is started, or open, but not all the

     * attributes or namespace information is yet collected.

     */

    boolean m_startTagOpen = false;

    /**

     * Constructor to create the root of the element contexts.

     *

     */

    ElemContext()

    {

        // this assignment means can never pop this context off

        m_prev = this;

        // depth 0 because it doesn't correspond to any element

        m_currentElemDepth = 0;

    }

    /**

     * Constructor to create the "stack frame" for a given element depth.

     *

     * This implementation will re-use the context at each depth. If

     * a documents deepest element depth is N then there will be (N+1)

     * such objects created, no more than that.

     *

     * @param previous The "stack frame" corresponding to the new

     * elements parent element.

     */

    private ElemContext(final ElemContext previous)

    {

        m_prev = previous;

        m_currentElemDepth = previous.m_currentElemDepth + 1;

    }

    /**

     * Pop the current "stack frame".

     * @return Returns the parent "stack frame" of the one popped.

     */

    final ElemContext pop()

    {

        /* a very simple pop.  No clean up is done of the deeper

         * stack frame.  All deeper stack frames are still attached

         * but dormant, just waiting to be re-used.

         */

        return this.m_prev;

    }

    /**

     * This method pushes an element "stack frame"

     * but with no initialization of values in that frame.

     * This method is used for optimization purposes, like when pushing

     * a stack frame for an HTML "IMG" tag which has no children and

     * the stack frame will almost immediately be popped.

     */

    final ElemContext push()

    {

        ElemContext frame = this.m_next;

        if (frame == null)

        {

            /* We have never been at this depth yet, and there is no

             * stack frame to re-use, so we now make a new one.

             */

            frame = new ElemContext(this);

            this.m_next = frame;

        }

        /*

         * We shouldn't need to set this true because we should just

         * be pushing a dummy stack frame that will be instantly popped.

         * Yet we need to be ready in case this element does have

         * unexpected children.

         */

        frame.m_startTagOpen = true;

        return frame;

    }

    /**

     * Push an element context on the stack. This context keeps track of

     * information gathered about the element.

     * @param uri The URI for the namespace for the element name,

     * can be null if it is not yet known.

     * @param localName The local name of the element (no prefix),

     * can be null.

     * @param qName The qualified name (with prefix, if any)

     * of the element, this parameter is required.

     */

    final ElemContext push(

        final String uri,

        final String localName,

        final String qName)

    {

        ElemContext frame = this.m_next;

        if (frame == null)

        {

            /* We have never been at this depth yet, and there is no

             * stack frame to re-use, so we now make a new one.

             */

            frame = new ElemContext(this);

            this.m_next = frame;

        }

        // Initialize, or reset values in the new or re-used stack frame.

        frame.m_elementName = qName;

        frame.m_elementLocalName = localName;

        frame.m_elementURI = uri;

        frame.m_isCdataSection = false;

        frame.m_startTagOpen = true;

        // is_Raw is already set in the HTML startElement() method

        // frame.m_isRaw = false;

        return frame;

    }

}