/*******************************************************************************
 * Copyright (c) 2008 Standards for Technology in Automotive Retail
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     David Carver - STAR - bug 224197 - initial API and implementation
 *                    based on work from Apache Xalan 2.7.0
 *******************************************************************************/
/*
 * 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: ElemVariable.java,v 1.4 2008/03/28 02:38:15 dacarver Exp $
 */
package org.eclipse.wst.xsl.core.internal.compiler.xslt10.templates;

import javax.xml.transform.TransformerException;

import org.eclipse.wst.xsl.core.compiler.xslt10.res.XSLTErrorResources;
import org.eclipse.wst.xsl.core.internal.compiler.xslt10.transformer.TransformerImpl;
import org.apache.xml.utils.QName;
import org.eclipse.wst.xsl.core.internal.compiler.xslt10.xpath.XPath;
import org.apache.xpath.XPathContext;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.objects.XRTreeFrag;
import org.apache.xpath.objects.XRTreeFragSelectWrapper;
import org.apache.xpath.objects.XString;

/**
 * Implement xsl:variable.
 * 
 * <pre>
 * &lt;!ELEMENT xsl:variable %template;&gt;
 * &lt;!ATTLIST xsl:variable
 *   name %qname; #REQUIRED
 *   select %expr; #IMPLIED
 * &gt;
 * </pre>
 * 
 * @see <a href="http://www.w3.org/TR/xslt#variables">variables in XSLT
 *      Specification</a>
 * @xsl.usage advanced
 */
public class ElemVariable extends ElemTemplateElement {
	static final long serialVersionUID = 9111131075322790061L;

	/**
	 * Constructor ElemVariable
	 * 
	 */
	public ElemVariable() {
	}

	/**
	 * This is the index into the stack frame.
	 */
	protected int m_index;

	/**
	 * The stack frame size for this variable if it is a global variable that
	 * declares an RTF, which is equal to the maximum number of variables that
	 * can be declared in the variable at one time.
	 */
	int m_frameSize = -1;

	/**
	 * Sets the relative position of this variable within the stack frame (if
	 * local) or the global area (if global). Note that this should be called
	 * only for global variables since the local position is computed in the
	 * compose() method.
	 */
	public void setIndex(int index) {
		m_index = index;
	}

	/**
	 * If this element is not at the top-level, get the relative position of the
	 * variable into the stack frame. If this variable is at the top-level, get
	 * the relative position within the global area.
	 */
	public int getIndex() {
		return m_index;
	}

	/**
	 * The value of the "select" attribute.
	 * 
	 * @serial
	 */
	private XPath m_selectPattern;

	/**
	 * Set the "select" attribute. If the variable-binding element has a select
	 * attribute, then the value of the attribute must be an expression and the
	 * value of the variable is the object that results from evaluating the
	 * expression. In this case, the content of the variable must be empty.
	 * 
	 * @param v
	 *            Value to set for the "select" attribute.
	 */
	public void setSelect(XPath v) {
		m_selectPattern = v;
	}

	/**
	 * Get the "select" attribute. If the variable-binding element has a select
	 * attribute, then the value of the attribute must be an expression and the
	 * value of the variable is the object that results from evaluating the
	 * expression. In this case, the content of the variable must be empty.
	 * 
	 * @return Value of the "select" attribute.
	 */
	public XPath getSelect() {
		return m_selectPattern;
	}

	/**
	 * The value of the "name" attribute.
	 * 
	 * @serial
	 */
	protected QName m_qname;

	/**
	 * Set the "name" attribute. Both xsl:variable and xsl:param have a required
	 * name attribute, which specifies the name of the variable. The value of
	 * the name attribute is a QName, which is expanded as described in [2.4
	 * Qualified Names].
	 * 
	 * @see <a href="http://www.w3.org/TR/xslt#qname">qname in XSLT
	 *      Specification</a>
	 * 
	 * @param v
	 *            Value to set for the "name" attribute.
	 */
	public void setName(QName v) {
		m_qname = v;
	}

	/**
	 * Get the "name" attribute. Both xsl:variable and xsl:param have a required
	 * name attribute, which specifies the name of the variable. The value of
	 * the name attribute is a QName, which is expanded as described in [2.4
	 * Qualified Names].
	 * 
	 * @see <a href="http://www.w3.org/TR/xslt#qname">qname in XSLT
	 *      Specification</a>
	 * 
	 * @return Value of the "name" attribute.
	 */
	public QName getName() {
		return m_qname;
	}

	/**
	 * Tells if this is a top-level variable or param, or not.
	 * 
	 * @serial
	 */
	private boolean m_isTopLevel = false;

	/**
	 * Set if this is a top-level variable or param, or not.
	 * 
	 * @see <a
	 *      href="http://www.w3.org/TR/xslt#top-level-variables">top-level-variables
	 *      in XSLT Specification</a>
	 * 
	 * @param v
	 *            Boolean indicating whether this is a top-level variable or
	 *            param, or not.
	 */
	public void setIsTopLevel(boolean v) {
		m_isTopLevel = v;
	}

	/**
	 * Get if this is a top-level variable or param, or not.
	 * 
	 * @see <a
	 *      href="http://www.w3.org/TR/xslt#top-level-variables">top-level-variables
	 *      in XSLT Specification</a>
	 * 
	 * @return Boolean indicating whether this is a top-level variable or param,
	 *         or not.
	 */
	public boolean getIsTopLevel() {
		return m_isTopLevel;
	}

	/**
	 * Get an integer representation of the element type.
	 * 
	 * @return An integer representation of the element, defined in the
	 *         Constants class.
	 * @see org.apache.xalan.templates.Constants
	 */
	@Override
	public int getXSLToken() {
		return Constants.ELEMNAME_VARIABLE;
	}

	/**
	 * Return the node name.
	 * 
	 * @return The node name
	 */
	@Override
	public String getNodeName() {
		return Constants.ELEMNAME_VARIABLE_STRING;
	}

	/**
	 * Copy constructor.
	 * 
	 * @param param
	 *            An element created from an xsl:variable
	 * 
	 * @throws TransformerException
	 */
	public ElemVariable(ElemVariable param) throws TransformerException {

		m_selectPattern = param.m_selectPattern;
		m_qname = param.m_qname;
		m_isTopLevel = param.m_isTopLevel;

		// m_value = param.m_value;
		// m_varContext = param.m_varContext;
	}

	/**
	 * Execute a variable declaration and push it onto the variable stack.
	 * 
	 * @see <a href="http://www.w3.org/TR/xslt#variables">variables in XSLT
	 *      Specification</a>
	 * 
	 * @param transformer
	 *            non-null reference to the the current transform-time state.
	 * 
	 * @throws TransformerException
	 */
	@Override
	public void execute(TransformerImpl transformer)
			throws TransformerException {

		if (transformer.getDebug())
			transformer.getTraceManager().fireTraceEvent(this);

		int sourceNode = transformer.getXPathContext().getCurrentNode();

		XObject var = getValue(transformer, sourceNode);

		// transformer.getXPathContext().getVarStack().pushVariable(m_qname,
		// var);
		transformer.getXPathContext().getVarStack().setLocalVariable(m_index,
				var);

		if (transformer.getDebug())
			transformer.getTraceManager().fireTraceEndEvent(this);
	}

	/**
	 * Get the XObject representation of the variable.
	 * 
	 * @param transformer
	 *            non-null reference to the the current transform-time state.
	 * @param sourceNode
	 *            non-null reference to the <a
	 *            href="http://www.w3.org/TR/xslt#dt-current-node">current
	 *            source node</a>.
	 * 
	 * @return the XObject representation of the variable.
	 * 
	 * @throws TransformerException
	 */
	public XObject getValue(TransformerImpl transformer, int sourceNode)
			throws TransformerException {

		XObject var;
		XPathContext xctxt = transformer.getXPathContext();

		xctxt.pushCurrentNode(sourceNode);

		try {
			if (null != m_selectPattern) {
				var = m_selectPattern.execute(xctxt, sourceNode, this);

				var.allowDetachToRelease(false);

				if (transformer.getDebug())
					transformer.getTraceManager().fireSelectedEvent(sourceNode,
							this, "select", m_selectPattern, var);
			} else if (null == getFirstChildElem()) {
				var = XString.EMPTYSTRING;
			} else {

				// Use result tree fragment.
				// Global variables may be deferred (see XUnresolvedVariable)
				// and hence
				// need to be assigned to a different set of DTMs than local
				// variables
				// so they aren't popped off the stack on return from a
				// template.
				int df;

				// Bugzilla 7118: A variable set via an RTF may create local
				// variables during that computation. To keep them from
				// overwriting
				// variables at this level, push a new variable stack.
				// //// PROBLEM: This is provoking a variable-used-before-set
				// //// problem in parameters. Needs more study.
				try {
					// ////////xctxt.getVarStack().link(0);
					if (m_parentNode instanceof Stylesheet) // Global variable
						df = transformer.transformToGlobalRTF(this);
					else
						df = transformer.transformToRTF(this);
				} finally {
					// ////////////xctxt.getVarStack().unlink();
				}

				var = new XRTreeFrag(df, xctxt, this);
			}
		} finally {
			xctxt.popCurrentNode();
		}

		return var;
	}

	/**
	 * This function is called after everything else has been recomposed, and
	 * allows the template to set remaining values that may be based on some
	 * other property that depends on recomposition.
	 */
	@Override
	public void compose(StylesheetRoot sroot) throws TransformerException {
		// See if we can reduce an RTF to a select with a string expression.
		if (null == m_selectPattern && sroot.getOptimizer()) {
			XPath newSelect = rewriteChildToExpression(this);
			if (null != newSelect)
				m_selectPattern = newSelect;
		}

		StylesheetRoot.ComposeState cstate = sroot.getComposeState();

		// This should be done before addVariableName, so we don't have
		// visibility
		// to the variable now being defined.
		java.util.Vector vnames = cstate.getVariableNames();
		if (null != m_selectPattern)
			m_selectPattern.fixupVariables(vnames, cstate.getGlobalsSize());

		// Only add the variable if this is not a global. If it is a global,
		// it was already added by stylesheet root.
		if (!(m_parentNode instanceof Stylesheet) && m_qname != null) {
			m_index = cstate.addVariableName(m_qname) - cstate.getGlobalsSize();
		} else if (m_parentNode instanceof Stylesheet) {
			// If this is a global, then we need to treat it as if it's a
			// xsl:template,
			// and count the number of variables it contains. So we set the
			// count to
			// zero here.
			cstate.resetStackFrameSize();
		}

		// This has to be done after the addVariableName, so that the variable
		// pushed won't be immediately popped again in endCompose.
		super.compose(sroot);
	}

	/**
	 * This after the template's children have been composed. We have to get the
	 * count of how many variables have been declared, so we can do a link and
	 * unlink.
	 */
	@Override
	public void endCompose(StylesheetRoot sroot) throws TransformerException {
		super.endCompose(sroot);
		if (m_parentNode instanceof Stylesheet) {
			StylesheetRoot.ComposeState cstate = sroot.getComposeState();
			m_frameSize = cstate.getFrameSize();
			cstate.resetStackFrameSize();
		}
	}

	// /**
	// * This after the template's children have been composed.
	// */
	// public void endCompose() throws TransformerException
	// {
	// super.endCompose();
	// }

	/**
	 * If the children of a variable is a single xsl:value-of or text literal,
	 * it is cheaper to evaluate this as an expression, so try and adapt the
	 * child an an expression.
	 * 
	 * @param varElem
	 *            Should be a ElemParam, ElemVariable, or ElemWithParam.
	 * 
	 * @return An XPath if rewrite is possible, else null.
	 * 
	 * @throws TransformerException
	 */
	static XPath rewriteChildToExpression(ElemTemplateElement varElem)
			throws TransformerException {

		ElemTemplateElement t = varElem.getFirstChildElem();

		// Down the line this can be done with multiple string objects using
		// the concat function.
		if (null != t && null == t.getNextSiblingElem()) {
			int etype = t.getXSLToken();

			if (Constants.ELEMNAME_VALUEOF == etype) {
				ElemValueOf valueof = (ElemValueOf) t;

				// %TBD% I'm worried about extended attributes here.
				if (valueof.getDisableOutputEscaping() == false
						&& valueof.getDOMBackPointer() == null) {
					varElem.m_firstChild = null;

					return new XPath(new XRTreeFragSelectWrapper(valueof
							.getSelect().getExpression()));
				}
			} else if (Constants.ELEMNAME_TEXTLITERALRESULT == etype) {
				ElemTextLiteral lit = (ElemTextLiteral) t;

				if (lit.getDisableOutputEscaping() == false
						&& lit.getDOMBackPointer() == null) {
					String str = lit.getNodeValue();
					XString xstr = new XString(str);

					varElem.m_firstChild = null;

					return new XPath(new XRTreeFragSelectWrapper(xstr));
				}
			}
		}

		return null;
	}

	/**
	 * This function is called during recomposition to control how this element
	 * is composed.
	 * 
	 * @param root
	 *            The root stylesheet for this transformation.
	 */
	@Override
	public void recompose(StylesheetRoot root) {
		root.recomposeVariables(this);
	}

	/**
	 * Set the parent as an ElemTemplateElement.
	 * 
	 * @param p
	 *            This node's parent as an ElemTemplateElement
	 */
	@Override
	public void setParentElem(ElemTemplateElement p) {
		super.setParentElem(p);
		p.m_hasVariableDecl = true;
	}

	/**
	 * Accept a visitor and call the appropriate method for this class.
	 * 
	 * @param visitor
	 *            The visitor whose appropriate method will be called.
	 * @return true if the children of the object should be visited.
	 */
	@Override
	protected boolean accept(XSLTVisitor visitor) {
		return visitor.visitVariableOrParamDecl(this);
	}

	/**
	 * Call the children visitors.
	 * 
	 * @param visitor
	 *            The visitor whose appropriate method will be called.
	 */
	@Override
	protected void callChildVisitors(XSLTVisitor visitor, boolean callAttrs) {
		if (null != m_selectPattern)
			m_selectPattern.getExpression().callVisitors(m_selectPattern,
					visitor);
		super.callChildVisitors(visitor, callAttrs);
	}

	/**
	 * Tell if this is a psuedo variable reference, declared by Xalan instead of
	 * by the user.
	 */
	public boolean isPsuedoVar() {
		java.lang.String ns = m_qname.getNamespaceURI();
		if ((null != ns)
				&& ns.equals(RedundentExprEliminator.PSUEDOVARNAMESPACE)) {
			if (m_qname.getLocalName().startsWith("#"))
				return true;
		}
		return false;
	}

	/**
	 * Add a child to the child list. If the select attribute is present, an
	 * error will be raised.
	 * 
	 * @param elem
	 *            New element to append to this element's children list
	 * 
	 * @return null if the select attribute was present, otherwise the child
	 *         just added to the child list
	 */
	@Override
	public ElemTemplateElement appendChild(ElemTemplateElement elem) {
		// cannot have content and select
		if (m_selectPattern != null) {
			error(XSLTErrorResources.ER_CANT_HAVE_CONTENT_AND_SELECT,
					new Object[] { "xsl:" + this.getNodeName() });
			return null;
		}
		return super.appendChild(elem);
	}

}