/*
 *  eXist Open Source Native XML Database
 *  Copyright (C) 2001-04 Wolfgang M. Meier
 *  wolfgang@exist-db.org
 *  http://exist-db.org
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * 
 *  $Id$
 */
package org.exist.xquery;

import org.exist.dom.memtree.MemTreeBuilder;
import org.exist.xquery.util.ExpressionDumper;
import org.exist.xquery.value.Item;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceIterator;


/**
 * Implements a dynamic text constructor. Contrary to {@link org.exist.xquery.TextConstructor},
 * the character content of a DynamicTextConstructor is determined only at evaluation time.
 * 
 * @author wolf
 */
public class DynamicTextConstructor extends NodeConstructor {

    final private Expression content;
    
    /**
     * @param context
     */
    public DynamicTextConstructor(XQueryContext context, Expression contentExpr) {
        super(context);
        this.content = contentExpr;
    }

    public Expression getContent() {
        return content;
    }
    
    /* (non-Javadoc)
     * @see org.exist.xquery.Expression#analyze(org.exist.xquery.AnalyzeContextInfo)
     */
    public void analyze(AnalyzeContextInfo contextInfo) throws XPathException {
        super.analyze(contextInfo);
        contextInfo.setParent(this);
        content.analyze(contextInfo);
    }
    
    /* (non-Javadoc)
     * @see org.exist.xquery.Expression#eval(org.exist.xquery.value.Sequence, org.exist.xquery.value.Item)
     */
    public Sequence eval(Sequence contextSequence, Item contextItem) throws XPathException {
        if (context.getProfiler().isEnabled()) {
            context.getProfiler().start(this);       
            context.getProfiler().message(this, Profiler.DEPENDENCIES, "DEPENDENCIES", Dependency.getDependenciesName(this.getDependencies()));
            if (contextSequence != null)
                {context.getProfiler().message(this, Profiler.START_SEQUENCES, "CONTEXT SEQUENCE", contextSequence);}
            if (contextItem != null)
                {context.getProfiler().message(this, Profiler.START_SEQUENCES, "CONTEXT ITEM", contextItem.toSequence());}
        }

        if (newDocumentContext)
            {context.pushDocumentContext();}
        
        Sequence result;
        try {
            final Sequence contentSeq = content.eval(contextSequence, contextItem);

            if(contentSeq.isEmpty())
            	{result = Sequence.EMPTY_SEQUENCE;}
            else {
                final MemTreeBuilder builder = context.getDocumentBuilder();
                context.proceed(this, builder);
                final StringBuilder buf = new StringBuilder();
                for(final SequenceIterator i = Atomize.atomize(contentSeq).iterate(); i.hasNext(); ) {
                    context.proceed(this, builder);
                    final Item next = i.nextItem();
                    if(buf.length() > 0)
                        {buf.append(' ');}
                    buf.append(next.toString());
                }
                //It is possible for a text node constructor to construct a text node containing a zero-length string.
                //However, if used in the content of a constructed element or document node,
                //such a text node will be deleted or merged with another text node.
                if (!newDocumentContext && buf.length() == 0)
                    {result = Sequence.EMPTY_SEQUENCE;}
                else {
                    final int nodeNr = builder.characters(buf);
                    result = builder.getDocument().getNode(nodeNr);
                }
            }
        } finally {
            if (newDocumentContext)
                {context.popDocumentContext();}
        }

        if (context.getProfiler().isEnabled())           
            {context.getProfiler().end(this, "", result);}
        
        return result;
        
    }
    
    /* (non-Javadoc)
     * @see org.exist.xquery.Expression#dump(org.exist.xquery.util.ExpressionDumper)
     */
    public void dump(ExpressionDumper dumper) {
        dumper.display("text {");
        dumper.startIndent();
        content.dump(dumper);
        dumper.endIndent();
        dumper.nl().display("}");
    }
    
    public String toString() {
        return "text {" + content.toString() + "}";
    }    

    public void resetState(boolean postOptimization) {
    	super.resetState(postOptimization);
    	content.resetState(postOptimization);
    }

    public void accept(ExpressionVisitor visitor) {
        visitor.visitTextConstructor(this);
    }
}