/*
 * eXist Open Source Native XML Database
 * Copyright (C) 2001-2007 The eXist Project
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *  
 *  $Id$
 */
package org.exist.xquery;

import org.exist.xquery.util.ExpressionDumper;
import org.exist.xquery.value.Item;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.ValueSequence;

/**
 * An XQuery sequence constructor ",". For example, ($a, $b) constructs a new
 * sequence containing items $a and $b.
 * 
 * @author wolf
 */
public class SequenceConstructor extends PathExpr {

    /**
     * @param context
     */
    public SequenceConstructor(XQueryContext context) {
        super(context);
    }

    public void analyze(AnalyzeContextInfo contextInfo) throws XPathException {
        contextInfo.setParent(this);
        inPredicate = (contextInfo.getFlags() & IN_PREDICATE) > 0;
        unordered = (contextInfo.getFlags() & UNORDERED) > 0;
        contextId = contextInfo.getContextId();
        int staticType = Type.ANY_TYPE;
        for (int i = 0 ; i < steps.size() ; i++) {
            final Expression expr = steps.get(i);
            //Create a new context info because each sequence expression could modify it (add/remove flags...)
            final AnalyzeContextInfo info = new AnalyzeContextInfo(contextInfo);
            expr.analyze(info);
            if (staticType == Type.ANY_TYPE)
                {staticType = info.getStaticReturnType();}
            else if (staticType != Type.ITEM && staticType != info.getStaticReturnType())
                {staticType = Type.ITEM;}
        }
        contextInfo.setStaticReturnType(staticType);
    }

    /* (non-Javadoc)
     * @see org.exist.xquery.Expression#eval(org.exist.dom.persistent.DocumentSet, 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());}
        }
        final ValueSequence result = new ValueSequence();
        result.keepUnOrdered(unordered);
        for(final Expression step : steps) {
            context.pushDocumentContext();
            try {
                final Sequence temp = step.eval(contextSequence, contextItem);
                if(temp != null && !temp.isEmpty()) {
                      result.addAll(temp);
                }
            } finally {
                context.popDocumentContext();
            }
        }
        if (context.getProfiler().isEnabled()) 
            {context.getProfiler().end(this, "", result);}
        return result;
    }

    /* (non-Javadoc)
     * @see org.exist.xquery.PathExpr#dump(org.exist.xquery.util.ExpressionDumper)
     */
    public void dump(ExpressionDumper dumper) {
        dumper.display("(");
        dumper.startIndent();
        boolean moreThanOne = false;
        for(final Expression step : steps) {
            if (moreThanOne)
                {dumper.display(", ");}
            moreThanOne = true;
            step.dump(dumper);
        }
        dumper.endIndent();
        dumper.nl().display(")");
    }

    public String toString() {
        final StringBuilder result = new StringBuilder();
        result.append("( ");
        boolean moreThanOne = false;
        for (final Expression step : steps) {
            if (moreThanOne)
                {result.append(", ");}
            moreThanOne = true;
            result.append(step.toString());
        }
        result.append(" )");
        return result.toString();
    }

    /* (non-Javadoc)
     * @see org.exist.xquery.Expression#returnsType()
     */
    public int returnsType() {
        return Type.ITEM;
    }

    /* (non-Javadoc)
     * @see org.exist.xquery.AbstractExpression#getCardinality()
     */
    public int getCardinality() {
        return Cardinality.ZERO_OR_MORE;
    }

    @Override
    public boolean allowMixedNodesInReturn() {
        return true;
    }

    /* (non-Javadoc)
     * @see org.exist.xquery.AbstractExpression#resetState()
     */
    public void resetState(boolean postOptimization) {
        super.resetState(postOptimization);
    }
}