/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/*

 * Copyright 1999-2004 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: UnionPathIterator.java,v 1.2.4.1 2005/09/14 19:43:25 jeffsuttor Exp $

 */

package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.Axis;

import com.sun.org.apache.xml.internal.dtm.DTM;

import com.sun.org.apache.xml.internal.dtm.DTMIterator;

import com.sun.org.apache.xpath.internal.Expression;

import com.sun.org.apache.xpath.internal.ExpressionOwner;

import com.sun.org.apache.xpath.internal.XPathVisitor;

import com.sun.org.apache.xpath.internal.compiler.Compiler;

import com.sun.org.apache.xpath.internal.compiler.OpCodes;

/**

 * This class extends NodeSetDTM, which implements DTMIterator,

 * and fetches nodes one at a time in document order based on a XPath

 * <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.

 * As each node is iterated via nextNode(), the node is also stored

 * in the NodeVector, so that previousNode() can easily be done.

 * @xsl.usage advanced

 */

public class UnionPathIterator extends LocPathIterator

        implements Cloneable, DTMIterator, java.io.Serializable, PathComponent

{

    static final long serialVersionUID = -3910351546843826781L;

  /**

   * Constructor to create an instance which you can add location paths to.

   */

  public UnionPathIterator()

  {

    super();

    // m_mutable = false;

    // m_cacheNodes = false;

    m_iterators = null;

    m_exprs = null;

  }

  /**

   * Initialize the context values for this expression

   * after it is cloned.

   *

   * @param context The XPath runtime context for this

   * transformation.

   */

  public void setRoot(int context, Object environment)

  {

    super.setRoot(context, environment);

    try

    {

      if (null != m_exprs)

      {

        int n = m_exprs.length;

        DTMIterator newIters[] = new DTMIterator[n];

        for (int i = 0; i < n; i++)

        {

          DTMIterator iter = m_exprs[i].asIterator(m_execContext, context);

          newIters[i] = iter;

          iter.nextNode();

        }

        m_iterators = newIters;

      }

    }

    catch(Exception e)

    {

      throw new com.sun.org.apache.xml.internal.utils.WrappedRuntimeException(e);

    }

  }

  /**

   * Add an iterator to the union list.

   *

   * @param expr non-null reference to a location path iterator.

   */

  public void addIterator(DTMIterator expr)

  {

    // Increase array size by only 1 at a time.  Fix this

    // if it looks to be a problem.

    if (null == m_iterators)

    {

      m_iterators = new DTMIterator[1];

      m_iterators[0] = expr;

    }

    else

    {

      DTMIterator[] exprs = m_iterators;

      int len = m_iterators.length;

      m_iterators = new DTMIterator[len + 1];

      System.arraycopy(exprs, 0, m_iterators, 0, len);

      m_iterators[len] = expr;

    }

    expr.nextNode();

    if(expr instanceof Expression)

        ((Expression)expr).exprSetParent(this);

  }

  /**

   *  Detaches the iterator from the set which it iterated over, releasing

   * any computational resources and placing the iterator in the INVALID

   * state. After<code>detach</code> has been invoked, calls to

   * <code>nextNode</code> or<code>previousNode</code> will raise the

   * exception INVALID_STATE_ERR.

   */

  public void detach()

  {

          if(m_allowDetach && null != m_iterators){

                  int n = m_iterators.length;

                  for(int i = 0; i < n; i++)

                  {

                          m_iterators[i].detach();

                  }

                  m_iterators = null;

          }

  }

  /**

   * Create a UnionPathIterator object, including creation

   * of location path iterators from the opcode list, and call back

   * into the Compiler to create predicate expressions.

   *

   * @param compiler The Compiler which is creating

   * this expression.

   * @param opPos The position of this iterator in the

   * opcode list from the compiler.

   *

   * @throws javax.xml.transform.TransformerException

   */

  public UnionPathIterator(Compiler compiler, int opPos)

          throws javax.xml.transform.TransformerException

  {

    super();

    loadLocationPaths(compiler, opPos, 0);

  }

  /**

   * This will return an iterator capable of handling the union of paths given.

   *

   * @param compiler The Compiler which is creating

   * this expression.

   * @param opPos The position of this iterator in the

   * opcode list from the compiler.

   *

   * @return Object that is derived from LocPathIterator.

   *

   * @throws javax.xml.transform.TransformerException

   */

  public static LocPathIterator createUnionIterator(Compiler compiler, int opPos)

          throws javax.xml.transform.TransformerException

  {

        // For the moment, I'm going to first create a full UnionPathIterator, and

        // then see if I can reduce it to a UnionChildIterator.  It would obviously

        // be more effecient to just test for the conditions for a UnionChildIterator,

        // and then create that directly.

        UnionPathIterator upi = new UnionPathIterator(compiler, opPos);

        int nPaths = upi.m_exprs.length;

        boolean isAllChildIterators = true;

        for(int i = 0; i < nPaths; i++)

        {

                LocPathIterator lpi = upi.m_exprs[i];

                if(lpi.getAxis() != Axis.CHILD)

                {

                        isAllChildIterators = false;

                        break;

                }

                else

                {

                        // check for positional predicates or position function, which won't work.

                        if(HasPositionalPredChecker.check(lpi))

                        {

                                isAllChildIterators = false;

                                break;

                        }

                }

        }

        if(isAllChildIterators)

        {

                UnionChildIterator uci = new UnionChildIterator();

                for(int i = 0; i < nPaths; i++)

                {

                        PredicatedNodeTest lpi = upi.m_exprs[i];

                        // I could strip the lpi down to a pure PredicatedNodeTest, but

                        // I don't think it's worth it.  Note that the test can be used

                        // as a static object... so it doesn't have to be cloned.

                        uci.addNodeTest(lpi);

                }

                return uci;

        }

        else

                return upi;

  }

  /**

   * Get the analysis bits for this walker, as defined in the WalkerFactory.

   * @return One of WalkerFactory#BIT_DESCENDANT, etc.

   */

  public int getAnalysisBits()

  {

    int bits = 0;

    if (m_exprs != null)

    {

      int n = m_exprs.length;

      for (int i = 0; i < n; i++)

      {

        int bit = m_exprs[i].getAnalysisBits();

        bits |= bit;

      }

    }

    return bits;

  }

  /**

   * Read the object from a serialization stream.

   *

   * @param stream Input stream to read from

   *

   * @throws java.io.IOException

   * @throws javax.xml.transform.TransformerException

   */

  private void readObject(java.io.ObjectInputStream stream)

          throws java.io.IOException, javax.xml.transform.TransformerException

  {

    try

    {

      stream.defaultReadObject();

      m_clones =  new IteratorPool(this);

    }

    catch (ClassNotFoundException cnfe)

    {

      throw new javax.xml.transform.TransformerException(cnfe);

    }

  }

  /**

   * Get a cloned LocPathIterator that holds the same

   * position as this iterator.

   *

   * @return A clone of this iterator that holds the same node position.

   *

   * @throws CloneNotSupportedException

   */

  public Object clone() throws CloneNotSupportedException

  {

    UnionPathIterator clone = (UnionPathIterator) super.clone();

    if (m_iterators != null)

    {

      int n = m_iterators.length;

      clone.m_iterators = new DTMIterator[n];

      for (int i = 0; i < n; i++)

      {

        clone.m_iterators[i] = (DTMIterator)m_iterators[i].clone();

      }

    }

    return clone;

  }

  /**

   * Create a new location path iterator.

   *

   * @param compiler The Compiler which is creating

   * this expression.

   * @param opPos The position of this iterator in the

   *

   * @return New location path iterator.

   *

   * @throws javax.xml.transform.TransformerException

   */

  protected LocPathIterator createDTMIterator(

          Compiler compiler, int opPos) throws javax.xml.transform.TransformerException

  {

    LocPathIterator lpi = (LocPathIterator)WalkerFactory.newDTMIterator(compiler, opPos,

                                      (compiler.getLocationPathDepth() <= 0));

    return lpi;

  }

  /**

   * Initialize the location path iterators.  Recursive.

   *

   * @param compiler The Compiler which is creating

   * this expression.

   * @param opPos The position of this iterator in the

   * opcode list from the compiler.

   * @param count The insert position of the iterator.

   *

   * @throws javax.xml.transform.TransformerException

   */

  protected void loadLocationPaths(Compiler compiler, int opPos, int count)

          throws javax.xml.transform.TransformerException

  {

    // TODO: Handle unwrapped FilterExpr

    int steptype = compiler.getOp(opPos);

    if (steptype == OpCodes.OP_LOCATIONPATH)

    {

      loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

      m_exprs[count] = createDTMIterator(compiler, opPos);

      m_exprs[count].exprSetParent(this);

    }

    else

    {

      // Have to check for unwrapped functions, which the LocPathIterator

      // doesn't handle.

      switch (steptype)

      {

      case OpCodes.OP_VARIABLE :

      case OpCodes.OP_EXTFUNCTION :

      case OpCodes.OP_FUNCTION :

      case OpCodes.OP_GROUP :

        loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

        WalkingIterator iter =

          new WalkingIterator(compiler.getNamespaceContext());

        iter.exprSetParent(this);

        if(compiler.getLocationPathDepth() <= 0)

          iter.setIsTopLevel(true);

        iter.m_firstWalker = new com.sun.org.apache.xpath.internal.axes.FilterExprWalker(iter);

        iter.m_firstWalker.init(compiler, opPos, steptype);

        m_exprs[count] = iter;

        break;

      default :

        m_exprs = new LocPathIterator[count];

      }

    }

  }

  /**

   *  Returns the next node in the set and advances the position of the

   * iterator in the set. After a DTMIterator is created, the first call

   * to nextNode() returns the first node in the set.

   * @return  The next <code>Node</code> in the set being iterated over, or

   *   <code>null</code> if there are no more members in that set.

   */

  public int nextNode()

  {

        if(m_foundLast)

                return DTM.NULL;

    // Loop through the iterators getting the current fetched

    // node, and get the earliest occuring in document order

    int earliestNode = DTM.NULL;

    if (null != m_iterators)

    {

      int n = m_iterators.length;

      int iteratorUsed = -1;

      for (int i = 0; i < n; i++)

      {

        int node = m_iterators[i].getCurrentNode();

        if (DTM.NULL == node)

          continue;

        else if (DTM.NULL == earliestNode)

        {

          iteratorUsed = i;

          earliestNode = node;

        }

        else

        {

          if (node == earliestNode)

          {

            // Found a duplicate, so skip past it.

            m_iterators[i].nextNode();

          }

          else

          {

            DTM dtm = getDTM(node);

            if (dtm.isNodeAfter(node, earliestNode))

            {

              iteratorUsed = i;

              earliestNode = node;

            }

          }

        }

      }

      if (DTM.NULL != earliestNode)

      {

        m_iterators[iteratorUsed].nextNode();

        incrementCurrentPos();

      }

      else

        m_foundLast = true;

    }

    m_lastFetched = earliestNode;

    return earliestNode;

  }

  /**

   * This function is used to fixup variables from QNames to stack frame

   * indexes at stylesheet build time.

   * @param vars List of QNames that correspond to variables.  This list

   * should be searched backwards for the first qualified name that

   * corresponds to the variable reference qname.  The position of the

   * QName in the vector from the start of the vector will be its position

   * in the stack frame (but variables above the globalsTop value will need

   * to be offset to the current stack frame).

   */

  public void fixupVariables(java.util.Vector vars, int globalsSize)

  {

    for (int i = 0; i < m_exprs.length; i++)

    {

      m_exprs[i].fixupVariables(vars, globalsSize);

    }

  }

  /**

   * The location path iterators, one for each

   * <a href="http://www.w3.org/TR/xpath#NT-LocationPath">location

   * path</a> contained in the union expression.

   * @serial

   */

  protected LocPathIterator[] m_exprs;

  /**

   * The location path iterators, one for each

   * <a href="http://www.w3.org/TR/xpath#NT-LocationPath">location

   * path</a> contained in the union expression.

   * @serial

   */

  protected DTMIterator[] m_iterators;

  /**

   * Returns the axis being iterated, if it is known.

   *

   * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple

   * types.

   */

  public int getAxis()

  {

    // Could be smarter.

    return -1;

  }

  class iterOwner implements ExpressionOwner

  {

        int m_index;

        iterOwner(int index)

        {

                m_index = index;

        }

    /**

     * @see ExpressionOwner#getExpression()

     */

    public Expression getExpression()

    {

      return m_exprs[m_index];

    }

    /**

     * @see ExpressionOwner#setExpression(Expression)

     */

    public void setExpression(Expression exp)

    {

        if(!(exp instanceof LocPathIterator))

        {

                // Yuck.  Need FilterExprIter.  Or make it so m_exprs can be just

                // plain expressions?

                WalkingIterator wi = new WalkingIterator(getPrefixResolver());

                FilterExprWalker few = new FilterExprWalker(wi);

                wi.setFirstWalker(few);

                few.setInnerExpression(exp);

                wi.exprSetParent(UnionPathIterator.this);

                few.exprSetParent(wi);

                exp.exprSetParent(few);

                exp = wi;

        }