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/*
 *  eXist Open Source Native XML Database
 *  Copyright (C) 2001-06 Wolfgang M. Meier
 *  [email protected]
 *  http://exist.sourceforge.net
 *  
 *  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.xquery.value.Item;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.util.ExpressionDumper;

/**
 * Abstract base class for simple functions. Subclasses should overwrite
 * method {@link #eval(Sequence[], Sequence)}.
 *
 * @author Wolfgang Meier
 */
public abstract class BasicFunction extends Function {

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

    @Override
	public Sequence eval(Sequence contextSequence, final 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 (contextItem != null) {
            contextSequence = contextItem.toSequence();
        }

        final int argCount = getArgumentCount();
        final Sequence[] args = new Sequence[argCount];
        for (int i = 0; i < argCount; i++) {
            try {
                args[i] = getArgument(i).eval(contextSequence, contextItem);
            } catch (final XPathException e) {
                if (e.getErrorCode() == null || e.getErrorCode() == ErrorCodes.ERROR) {
                    e.prependMessage(
                            ErrorCodes.XPTY0004,
                            "checking function parameter " + (i + 1) + " in call " + ExpressionDumper.dump(this) + ": ");
                }

                throw e;
            }
        }

        final Sequence result = eval(args, contextSequence);

        if (context.getProfiler().isEnabled()) {
            context.getProfiler().end(this, "", result);
        }

        return result;
    }

    /**
     * Process the function. All arguments are passed in the array args. The number of
     * arguments, their type and cardinality have already been checked to match
     * the function signature.
     *
     * @param args The arguments given to the function.
     * @param contextSequence The context sequence for the function or null.
     * @throws XPathException An error occurred.
     *
     * @return The result of the XPath function
     */
    public abstract Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException;
}