/*
 * eXist Open Source Native XML Database
 * Copyright (C) 2001-2016 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.
 */
package org.exist.xquery.functions.fn;

import org.exist.dom.QName;
import org.exist.dom.persistent.NodeProxy;
import org.exist.xquery.*;
import org.exist.xquery.value.*;
import org.w3c.dom.Node;

public class FnHasChildren extends Function {

    private final static QName QN_HAS_CHILDREN = new QName("has-children", Function.BUILTIN_FUNCTION_NS);

    public final static FunctionSignature FNS_HAS_CHILDREN_0 = new FunctionSignature(
            QN_HAS_CHILDREN,
            "Returns true if the context item has one or more child nodes",
            FunctionSignature.NO_ARGS,
            new FunctionReturnSequenceType(Type.BOOLEAN, Cardinality.EXACTLY_ONE, "true if the context item has one of more child nodes, false otherwise")
    );

    public final static FunctionSignature FNS_HAS_CHILDREN_1 = new FunctionSignature(
            QN_HAS_CHILDREN,
            "Returns true if the supplied node has one or more child nodes",
            new SequenceType[] {
                    new FunctionParameterSequenceType("node", Type.NODE, Cardinality.ZERO_OR_ONE, "The node to test")
            },
            new FunctionReturnSequenceType(Type.BOOLEAN, Cardinality.EXACTLY_ONE, "true if $node has one of more child nodes, false otherwise")
    );

    public FnHasChildren(final XQueryContext context, final FunctionSignature signature) {
        super(context, signature);
    }

    @Override
    public Sequence eval(Sequence contextSequence, final Item contextItem) throws XPathException {
        final NodeValue node;

        if(getArgumentCount() == 0) {
            // default to the context item

            if(contextItem == null) {
                throw new XPathException(this, ErrorCodes.XPDY0002, "Context item is absent");
            }

            contextSequence = contextItem.toSequence();

            if(contextSequence.isEmpty()) {
                return BooleanValue.FALSE;
            }

            final Item item = contextSequence.itemAt(0);
            if(!Type.subTypeOf(item.getType(), Type.NODE)) {
                throw new XPathException(this, ErrorCodes.XPTY0004, "Context item is not a node()");
            }

            node = (NodeValue)item;

        } else {
            final Sequence arg0 = getArgument(0).eval(contextSequence, contextItem);
            if(getArgumentCount() == 1 && arg0.isEmpty()) {
                return BooleanValue.FALSE;
            } else {
                node = (NodeValue)arg0.itemAt(0);
            }
        }

        final Node w3cNode;
        if(node instanceof NodeProxy) {
            w3cNode = node.getNode();
        } else if(node instanceof org.exist.dom.memtree.NodeImpl) {
            w3cNode = ((org.exist.dom.memtree.NodeImpl)node);
        } else {
            throw new XPathException(this, ErrorCodes.XPTY0004, "Context item is not a node()");
        }

        return BooleanValue.valueOf(w3cNode.hasChildNodes());
    }
}