/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:  
 *       "This product includes software developed by the 
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Ant", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.apache.tools.ant.util.regexp;

import org.apache.tools.ant.BuildException;

/**
 * Simple Factory Class that produces an implementation of
 * RegexpMatcher based on the system property
 * <code>ant.regexp.matcherimpl</code> and the classes
 * available.
 * 
 * <p>In a more general framework this class would be abstract and
 * have a static newInstance method.</p>
 *
 * @author <a href="mailto:stefan.bodewig@epost.de">Stefan Bodewig</a> 
 */
public class RegexpMatcherFactory {

    public RegexpMatcherFactory() {}

    public RegexpMatcher newRegexpMatcher() throws BuildException {
        String systemDefault = System.getProperty("ant.regexp.matcherimpl");
        if (systemDefault != null) {
            return createInstance(systemDefault);
            // XXX     should we silently possible exceptions and try to 
            //         load a different implementation?
        }

        try {
            return createInstance("org.apache.tools.ant.util.regexp.Jdk14RegexpMatcher");
        } catch (BuildException be) {}
        
        try {
            return createInstance("org.apache.tools.ant.util.regexp.JakartaOroMatcher");
        } catch (BuildException be) {}
        
        try {
            return createInstance("org.apache.tools.ant.util.regexp.JakartaRegexpMatcher");
        } catch (BuildException be) {}

        throw new BuildException("No supported regular expression matcher found");
   }

    protected RegexpMatcher createInstance(String className) 
        throws BuildException {
        try {
            Class implClass = Class.forName(className);
            return (RegexpMatcher) implClass.newInstance();
        } catch (Throwable t) {
            throw new BuildException(t);
        }
    }
}