/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xalan.templates;

import java.util.Hashtable;
import java.util.Vector;
import java.util.Enumeration;

import java.io.Serializable;

//import org.w3c.dom.Node;
import org.apache.xml.dtm.DTM;

import org.apache.xml.dtm.ref.ExpandedNameTable;

import javax.xml.transform.TransformerException;

import org.apache.xml.utils.QName;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xpath.XPath;
import org.apache.xpath.compiler.PsuedoNames;
import org.apache.xpath.patterns.NodeTest;
import org.apache.xpath.Expression;
import org.apache.xalan.res.XSLTErrorResources;
import org.apache.xpath.XPathContext;
import org.apache.xpath.patterns.StepPattern;
import org.apache.xpath.patterns.UnionPattern;

/**
 * <meta name="usage" content="advanced"/>
 * Encapsulates a template list, and helps locate individual templates.
 */
public class TemplateList implements java.io.Serializable
{

  /**
   * Construct a TemplateList object. Needs to be public so it can
   * be invoked from the CompilingStylesheetHandler.
   */
  public TemplateList()
  {
    super();
  }

  /**
   * Add a template to the table of named templates and/or the table of templates
   * with match patterns.  This routine should
   * be called in decreasing order of precedence but it checks nonetheless.
   *
   * @param template
   */
  public void setTemplate(ElemTemplate template)
  {
    if (null != template.getName())
    {
      ElemTemplate existingTemplate = (ElemTemplate) m_namedTemplates.get(template.getName());
      if (null == existingTemplate)
      {
        m_namedTemplates.put(template.getName(), template);
      }
      else
      {
        int existingPrecedence =
                        existingTemplate.getStylesheetComposed().getImportCountComposed();
        int newPrecedence = template.getStylesheetComposed().getImportCountComposed();
        if (newPrecedence > existingPrecedence)
        {
          // This should never happen
          m_namedTemplates.put(template.getName(), template);
        }
        else if (newPrecedence == existingPrecedence)
          template.error(XSLTErrorResources.ER_DUPLICATE_NAMED_TEMPLATE,
                       new Object[]{ template.getName() });
      }
    }

    XPath matchXPath = template.getMatch();

    if (null != matchXPath)
    {
      Expression matchExpr = matchXPath.getExpression();

      if (matchExpr instanceof StepPattern)
      {
        insertPatternInTable((StepPattern) matchExpr, template);
      }
      else if (matchExpr instanceof UnionPattern)
      {
        UnionPattern upat = (UnionPattern) matchExpr;
        StepPattern[] pats = upat.getPatterns();
        int n = pats.length;

        for (int i = 0; i < n; i++)
        {
          insertPatternInTable(pats[i], template);
        }
      }
      else
      {

        // TODO: assert error
      }
    }
  }

  /** Flag to indicate whether in DEBUG mode          */
  static boolean DEBUG = false;

  /**
   * Dump all patterns and elements that match those patterns
   *
   */
  void dumpAssociationTables()
  {

    Enumeration associations = m_patternTable.elements();

    while (associations.hasMoreElements())
    {
      TemplateSubPatternAssociation head =
        (TemplateSubPatternAssociation) associations.nextElement();

      while (null != head)
      {
        System.out.print("(" + head.getTargetString() + ", "
                         + head.getPattern() + ")");

        head = head.getNext();
      }

      System.out.println("\n.....");
    }

    TemplateSubPatternAssociation head = m_wildCardPatterns;

    System.out.print("wild card list: ");

    while (null != head)
    {
      System.out.print("(" + head.getTargetString() + ", "
                       + head.getPattern() + ")");

      head = head.getNext();
    }

    System.out.println("\n.....");
  }

  /**
   * After all templates have been added, this function
   * should be called.
   */
  public void compose(StylesheetRoot sroot)
  {

    if (DEBUG)
    {
      System.out.println("Before wildcard insert...");
      dumpAssociationTables();
    }

    if (null != m_wildCardPatterns)
    {
      Enumeration associations = m_patternTable.elements();

      while (associations.hasMoreElements())
      {
        TemplateSubPatternAssociation head =
          (TemplateSubPatternAssociation) associations.nextElement();
        TemplateSubPatternAssociation wild = m_wildCardPatterns;

        while (null != wild)
        {
          try
          {
            head = insertAssociationIntoList(
              head, (TemplateSubPatternAssociation) wild.clone(), true);
          }
          catch (CloneNotSupportedException cnse){}

          wild = wild.getNext();
        }
      }
    }

    if (DEBUG)
    {
      System.out.println("After wildcard insert...");
      dumpAssociationTables();
    }
  }

  /**
   * Insert the given TemplateSubPatternAssociation into the the linked
   * list.  Sort by import precedence, then priority, then by document order.
   *
   * @param head The first TemplateSubPatternAssociation in the linked list.
   * @param item The item that we want to insert into the proper place.
   * @param isWildCardInsert <code>true</code> if we are inserting a wild card 
   *             template onto this list.
   * @return the new head of the list.
   */
  private TemplateSubPatternAssociation
              insertAssociationIntoList(TemplateSubPatternAssociation head,
                                         TemplateSubPatternAssociation item,
                                         boolean isWildCardInsert)
  {

    // Sort first by import level (higher level is at front),
    // then by priority (highest priority is at front),
    // then by document order (later in document is at front).

    double priority = getPriorityOrScore(item);
    double workPriority;
    int importLevel = item.getImportLevel();
    int docOrder = item.getDocOrderPos();
    TemplateSubPatternAssociation insertPoint = head;
    TemplateSubPatternAssociation next;
    boolean insertBefore;         // true means insert before insertPoint; otherwise after
                                  // This can only be true if insertPoint is pointing to
                                  // the first or last template.

    // Spin down so that insertPoint points to:
    // (a) the template immediately _before_ the first template on the chain with
    // a precedence that is either (i) less than ours or (ii) the same as ours but
    // the template document position is less than ours
    // -or-
    // (b) the last template on the chain if no such template described in (a) exists.
    // If we are pointing to the first template or the last template (that is, case b),
    // we need to determine whether to insert before or after the template.  Otherwise,
    // we always insert after the insertPoint.

    while (true)
    {
      next = insertPoint.getNext();
      if (null == next)
        break;
      else
      {
        workPriority = getPriorityOrScore(next);
        if (importLevel > next.getImportLevel())
          break;
        else if (importLevel < next.getImportLevel())
          insertPoint = next;
        else if (priority > workPriority)               // import precedence is equal
          break;
        else if (priority < workPriority)
          insertPoint = next;
        else if (docOrder >= next.getDocOrderPos())     // priorities, import are equal
          break;
        else
          insertPoint = next;
      }
    }

    if ( (null == next) || (insertPoint == head) )      // insert point is first or last
    {
      workPriority = getPriorityOrScore(insertPoint);
      if (importLevel > insertPoint.getImportLevel())
        insertBefore = true;
      else if (importLevel < insertPoint.getImportLevel())
        insertBefore = false;
      else if (priority > workPriority)
        insertBefore = true;
      else if (priority < workPriority)
        insertBefore = false;
      else if (docOrder >= insertPoint.getDocOrderPos())
        insertBefore = true;
      else
        insertBefore = false;
    }
    else
      insertBefore = false;

    // System.out.println("appending: "+target+" to "+matchPat.getPattern());
    
    if (isWildCardInsert)
    {
      if (insertBefore)
      {
        item.setNext(insertPoint);

        String key = insertPoint.getTargetString();

        item.setTargetString(key);
        putHead(key, item);
        return item;
      }
      else
      {
        item.setNext(next);
        insertPoint.setNext(item);
        return head;
      }
    }
    else
    {
      if (insertBefore)
      {
        item.setNext(insertPoint);

        if (insertPoint.isWild() || item.isWild())
          m_wildCardPatterns = item;
        else
          putHead(item.getTargetString(), item);
        return item;
      }
      else
      {
        item.setNext(next);
        insertPoint.setNext(item);
        return head;
      }
    }
  }

  /**
   * Add a template to the template list.
   *
   * @param pattern
   * @param template
   */
  private void insertPatternInTable(StepPattern pattern, ElemTemplate template)
  {

    String target = pattern.getTargetString();

    if (null != target)
    {
      String pstring = template.getMatch().getPatternString();
      TemplateSubPatternAssociation association =
        new TemplateSubPatternAssociation(template, pattern, pstring);

      // See if there's already one there
      boolean isWildCard = association.isWild();
      TemplateSubPatternAssociation head = isWildCard
                                           ? m_wildCardPatterns
                                           : getHead(target);

      if (null == head)
      {
        if (isWildCard)
          m_wildCardPatterns = association;
        else
          putHead(target, association);
      }
      else
      {
        insertAssociationIntoList(head, association, false);
      }
    }
  }

  /**
   * Given a match pattern and template association, return the 
   * score of that match.  This score or priority can always be 
   * statically calculated.
   *
   * @param matchPat The match pattern to template association.
   *
   * @return {@link org.apache.xpath.patterns.NodeTest#SCORE_NODETEST}, 
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_NONE}, 
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_NSWILD}, 
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_QNAME}, or
   *         {@link org.apache.xpath.patterns.NodeTest#SCORE_OTHER}, or 
   *         the value defined by the priority attribute of the template.
   *
   */
  private double getPriorityOrScore(TemplateSubPatternAssociation matchPat)
  {

    double priority = matchPat.getTemplate().getPriority();

    if (priority == XPath.MATCH_SCORE_NONE)
    {
      Expression ex = matchPat.getStepPattern();

      if (ex instanceof NodeTest)
      {
        return ((NodeTest) ex).getDefaultScore();
      }
    }

    return priority;
  }

  /**
   * Locate a named template.
   *
   * @param qname  Qualified name of the template.
   *
   * @return Template argument with the requested name, or null if not found.
   */
  public ElemTemplate getTemplate(QName qname)
  {
    return (ElemTemplate) m_namedTemplates.get(qname);
  }

  /**
   * Get the head of the most likely list of associations to check, based on 
   * the name and type of the targetNode argument.
   *
   * @param xctxt The XPath runtime context.
   * @param targetNode The target node that will be checked for a match.
   * @param dtm The dtm owner for the target node.
   *
   * @return The head of a linked list that contains all possible match pattern to 
   * template associations.
   */
  public TemplateSubPatternAssociation getHead(XPathContext xctxt, 
                                               int targetNode, DTM dtm)
  {
    short targetNodeType = dtm.getNodeType(targetNode);
    TemplateSubPatternAssociation head;

    switch (targetNodeType)
    {
    case DTM.ELEMENT_NODE :
    case DTM.ATTRIBUTE_NODE :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getLocalName(targetNode));
      break;
    case DTM.TEXT_NODE :
    case DTM.CDATA_SECTION_NODE :
      head = m_textPatterns;
      break;
    case DTM.ENTITY_REFERENCE_NODE :
    case DTM.ENTITY_NODE :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getNodeName(targetNode)); // %REVIEW% I think this is right
      break;
    case DTM.PROCESSING_INSTRUCTION_NODE :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getLocalName(targetNode));
      break;
    case DTM.COMMENT_NODE :
      head = m_commentPatterns;
      break;
    case DTM.DOCUMENT_NODE :
    case DTM.DOCUMENT_FRAGMENT_NODE :
      head = m_docPatterns;
      break;
    case DTM.NOTATION_NODE :
    default :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getNodeName(targetNode)); // %REVIEW% I think this is right
    }

    return (null == head) ? m_wildCardPatterns : head;
  }
  
  /**
   * Given a target element, find the template that best
   * matches in the given XSL document, according
   * to the rules specified in the xsl draft.  This variation of getTemplate 
   * assumes the current node and current expression node have already been 
   * pushed. 
   *
   * @param xctxt
   * @param targetNode
   * @param mode A string indicating the display mode.
   * @param maxImportLevel The maximum importCountComposed that we should consider or -1
   *        if we should consider all import levels.  This is used by apply-imports to
   *        access templates that have been overridden.
   * @param quietConflictWarnings
   * @return Rule that best matches targetElem.
   * @throws XSLProcessorException thrown if the active ProblemListener and XPathContext decide
   * the error condition is severe enough to halt processing.
   *
   * @throws TransformerException
   */
  public ElemTemplate getTemplateFast(XPathContext xctxt,
                                int targetNode,
                                int expTypeID,
                                QName mode,
                                int maxImportLevel,
                                boolean quietConflictWarnings,
                                DTM dtm)
            throws TransformerException
  {
    
    TemplateSubPatternAssociation head;

    switch (dtm.getNodeType(targetNode))
    {
    case DTM.ELEMENT_NODE :
    case DTM.ATTRIBUTE_NODE :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getLocalNameFromExpandedNameID(expTypeID));
      break;
    case DTM.TEXT_NODE :
    case DTM.CDATA_SECTION_NODE :
      head = m_textPatterns;
      break;
    case DTM.ENTITY_REFERENCE_NODE :
    case DTM.ENTITY_NODE :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getNodeName(targetNode)); // %REVIEW% I think this is right
      break;
    case DTM.PROCESSING_INSTRUCTION_NODE :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getLocalName(targetNode));
      break;
    case DTM.COMMENT_NODE :
      head = m_commentPatterns;
      break;
    case DTM.DOCUMENT_NODE :
    case DTM.DOCUMENT_FRAGMENT_NODE :
      head = m_docPatterns;
      break;
    case DTM.NOTATION_NODE :
    default :
      head = (TemplateSubPatternAssociation) m_patternTable.get(
        dtm.getNodeName(targetNode)); // %REVIEW% I think this is right
    }

    if(null == head)
    {
      head = m_wildCardPatterns;
      if(null == head)
        return null;
    }                                              

    // XSLT functions, such as xsl:key, need to be able to get to 
    // current ElemTemplateElement via a cast to the prefix resolver.
    // Setting this fixes bug idkey03.
    xctxt.pushNamespaceContextNull();
    try
    {
      do
      {
        if ( (maxImportLevel > -1) && (head.getImportLevel() > maxImportLevel) )
        {
          continue;
        }
        ElemTemplate template = head.getTemplate();        
        xctxt.setNamespaceContext(template);
        
        if ((head.m_stepPattern.execute(xctxt, targetNode, dtm, expTypeID) != NodeTest.SCORE_NONE)
                && head.matchMode(mode))
        {
          if (quietConflictWarnings)
            checkConflicts(head, xctxt, targetNode, mode);

          return template;
        }
      }
      while (null != (head = head.getNext()));
    }
    finally
    {
      xctxt.popNamespaceContext();
    }

    return null;
  }  // end findTemplate

  /**
   * Given a target element, find the template that best
   * matches in the given XSL document, according
   * to the rules specified in the xsl draft.
   *
   * @param xctxt
   * @param targetNode
   * @param mode A string indicating the display mode.
   * @param quietConflictWarnings
   * @return Rule that best matches targetElem.
   * @throws XSLProcessorException thrown if the active ProblemListener and XPathContext decide
   * the error condition is severe enough to halt processing.
   *
   * @throws TransformerException
   */
  public ElemTemplate getTemplate(XPathContext xctxt,
                                int targetNode,
                                QName mode,
                                boolean quietConflictWarnings,
                                DTM dtm)
            throws TransformerException
  {

    TemplateSubPatternAssociation head = getHead(xctxt, targetNode, dtm);

    if (null != head)
    {
      // XSLT functions, such as xsl:key, need to be able to get to 
      // current ElemTemplateElement via a cast to the prefix resolver.
      // Setting this fixes bug idkey03.
      xctxt.pushNamespaceContextNull();
      xctxt.pushCurrentNodeAndExpression(targetNode, targetNode);
      try
      {
        do
        {
          ElemTemplate template = head.getTemplate();        
          xctxt.setNamespaceContext(template);
          
          if ((head.m_stepPattern.execute(xctxt, targetNode) != NodeTest.SCORE_NONE)
                  && head.matchMode(mode))
          {
            if (quietConflictWarnings)
              checkConflicts(head, xctxt, targetNode, mode);

            return template;
          }
        }
        while (null != (head = head.getNext()));
      }
      finally
      {
        xctxt.popCurrentNodeAndExpression();
        xctxt.popNamespaceContext();
      }
    }

    return null;
  }  // end findTemplate
  
  /**
   * Given a target element, find the template that best
   * matches in the given XSL document, according
   * to the rules specified in the xsl draft.
   *
   * @param xctxt
   * @param targetNode
   * @param mode A string indicating the display mode.
   * @param maxImportLevel The maximum importCountComposed that we should consider or -1
   *        if we should consider all import levels.  This is used by apply-imports to
   *        access templates that have been overridden.
   * @param maxEndImportLevel The count of composed imports
   * @param quietConflictWarnings
   * @return Rule that best matches targetElem.
   * @throws XSLProcessorException thrown if the active ProblemListener and XPathContext decide
   * the error condition is severe enough to halt processing.
   *
   * @throws TransformerException
   */
  public ElemTemplate getTemplate(XPathContext xctxt,
                                int targetNode,
                                QName mode,
                                int maxImportLevel, int endImportLevel,
                                boolean quietConflictWarnings,
                                DTM dtm)
            throws TransformerException
  {

    TemplateSubPatternAssociation head = getHead(xctxt, targetNode, dtm);

    if (null != head)
    {
      // XSLT functions, such as xsl:key, need to be able to get to 
      // current ElemTemplateElement via a cast to the prefix resolver.
      // Setting this fixes bug idkey03.
      xctxt.pushNamespaceContextNull();
      xctxt.pushCurrentNodeAndExpression(targetNode, targetNode);
      try
      {
        do
        {
          if ( (maxImportLevel > -1) && (head.getImportLevel() > maxImportLevel))
          {
            continue;
          }
          if (head.getImportLevel()<= maxImportLevel - endImportLevel)
            return null;
          ElemTemplate template = head.getTemplate();        
          xctxt.setNamespaceContext(template);
          
          if ((head.m_stepPattern.execute(xctxt, targetNode) != NodeTest.SCORE_NONE)
                  && head.matchMode(mode))
          {
            if (quietConflictWarnings)
              checkConflicts(head, xctxt, targetNode, mode);

            return template;
          }
        }
        while (null != (head = head.getNext()));
      }
      finally
      {
        xctxt.popCurrentNodeAndExpression();
        xctxt.popNamespaceContext();
      }
    }

    return null;
  }  // end findTemplate

  /**
   * Get a TemplateWalker for use by a compiler.  See the documentation for
   * the TreeWalker inner class for further details.
   */
  public TemplateWalker getWalker()
  {
    return new TemplateWalker();
  }

  /**
   * Check for match conflicts, and warn the stylesheet author.
   *
   * @param head Template pattern
   * @param xctxt Current XPath context
   * @param targetNode Node matching the pattern
   * @param mode reference, which may be null, to the <a href="http://www.w3.org/TR/xslt#modes">current mode</a>.
   */
  private void checkConflicts(TemplateSubPatternAssociation head,
                              XPathContext xctxt, int targetNode, QName mode)
  {

    // TODO: Check for conflicts.
  }

  /**
   * Add object to vector if not already there.
   *
   * @param obj
   * @param v
   */
  private void addObjectIfNotFound(Object obj, Vector v)
  {

    int n = v.size();
    boolean addIt = true;

    for (int i = 0; i < n; i++)
    {
      if (v.elementAt(i) == obj)
      {
        addIt = false;

        break;
      }
    }

    if (addIt)
    {
      v.addElement(obj);
    }
  }

  /**
   * Keyed on string macro names, and holding values
   * that are macro elements in the XSL DOM tree.
   * Initialized in initMacroLookupTable, and used in
   * findNamedTemplate.
   * @serial
   */
  private Hashtable m_namedTemplates = new Hashtable(89);

  /**
   * This table is keyed on the target elements
   * of patterns, and contains linked lists of
   * the actual patterns that match the target element
   * to some degree of specifity.
   * @serial
   */
  private Hashtable m_patternTable = new Hashtable(89);

  /** Wildcard patterns.
   *  @serial          */
  private TemplateSubPatternAssociation m_wildCardPatterns = null;

  /** Text Patterns.
   *  @serial          */
  private TemplateSubPatternAssociation m_textPatterns = null;

  /** Root document Patterns.
   *  @serial          */
  private TemplateSubPatternAssociation m_docPatterns = null;

  /** Comment Patterns.
   *  @serial          */
  private TemplateSubPatternAssociation m_commentPatterns = null;

  /**
   * Get table of named Templates.
   * These are keyed on template names, and holding values
   * that are template elements.
   *
   * @return A Hashtable dictionary that contains {@link java.lang.String}s 
   * as the keys, and {@link org.apache.xalan.templates.ElemTemplate}s as the 
   * values. 
   */
  private Hashtable getNamedTemplates()
  {
    return m_namedTemplates;
  }

  /**
   * Set table of named Templates.
   * These are keyed on string macro names, and holding values
   * that are template elements in the XSL DOM tree.
   *
   * @param v Hashtable dictionary that contains {@link java.lang.String}s 
   * as the keys, and {@link org.apache.xalan.templates.ElemTemplate}s as the 
   * values.
   */
  private void setNamedTemplates(Hashtable v)
  {
    m_namedTemplates = v;
  }

  /**
   * Get the head of the assocation list that is keyed by target.
   *
   * @param key The name of a node. 
   *
   * @return The head of a linked list that contains all possible match pattern to 
   * template associations for the given key.
   */
  private TemplateSubPatternAssociation getHead(String key)
  {
    return (TemplateSubPatternAssociation) m_patternTable.get(key);
  }

  /**
   * Get the head of the assocation list that is keyed by target.
   *
   * @param key
   * @param assoc
   */
  private void putHead(String key, TemplateSubPatternAssociation assoc)
  {

    if (key.equals(PsuedoNames.PSEUDONAME_TEXT))
      m_textPatterns = assoc;
    else if (key.equals(PsuedoNames.PSEUDONAME_ROOT))
      m_docPatterns = assoc;
    else if (key.equals(PsuedoNames.PSEUDONAME_COMMENT))
      m_commentPatterns = assoc;

    m_patternTable.put(key, assoc);
  }

  /**
   * An inner class used by a compiler to iterate over all of the ElemTemplates
   * stored in this TemplateList.  The compiler can replace returned templates
   * with their compiled equivalent.
   */
  public class TemplateWalker
  {
    private Enumeration hashIterator;
    private boolean inPatterns;
    private TemplateSubPatternAssociation curPattern;

    private Hashtable m_compilerCache = new Hashtable();

    private TemplateWalker()
    {
      hashIterator = m_patternTable.elements();
      inPatterns = true;
      curPattern = null;
    }

    public ElemTemplate next()
    {

      ElemTemplate retValue = null;
      ElemTemplate ct;

      while (true)
      {
        if (inPatterns)
        {
          if (null != curPattern)
            curPattern = curPattern.getNext();

          if (null != curPattern)
            retValue = curPattern.getTemplate();
          else
          {
            if (hashIterator.hasMoreElements())
            {
              curPattern = (TemplateSubPatternAssociation) hashIterator.nextElement();
              retValue =  curPattern.getTemplate();
            }
            else
            {
              inPatterns = false;
              hashIterator = m_namedTemplates.elements();
            }
          }
        }

        if (!inPatterns)
        {
          if (hashIterator.hasMoreElements())
            retValue = (ElemTemplate) hashIterator.nextElement();
          else
            return null;
        }

        ct = (ElemTemplate) m_compilerCache.get(new Integer(retValue.getUid()));
        if (null == ct)
        {
          m_compilerCache.put(new Integer(retValue.getUid()), retValue);
          return retValue;
        }
      }
    }
  }

}