/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002 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"
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 *
 * 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
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 * 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.types.selectors;

import java.io.File;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.BuildException;
import  org.apache.tools.ant.types.DataType;

/**
 * A convenience base class that you can subclass Selectors from. It
 * provides some helpful common behaviour. Note that there is no need
 * for Selectors to inherit from this class, it is only necessary that
 * they implement FileSelector.
 *
 * @author <a href="mailto:bruce@callenish.com">Bruce Atherton</a>
 * @since 1.5
 */
public abstract class BaseSelector extends DataType implements FileSelector {

    private String errmsg = null;


    /**
     * Do nothing constructor.
     */
    public BaseSelector() {
    }

    /**
     * Allows all selectors to indicate a setup error. Note that only
     * the first error message is recorded.
     *
     * @param msg The error message any BuildException should throw.
     */
    public void setError(String msg) {
        if (errmsg == null) {
            errmsg = msg;
        }
    }

    /**
     * Returns any error messages that have been set.
     *
     * @return the error condition
     */
    public String getError() {
        return errmsg;
    }


    /**
     * <p>Subclasses can override this method to provide checking of their
     * state. So long as they call validate() from isSelected(), this will
     * be called automatically (unless they override validate()).</p>
     * <p>Implementations should check for incorrect settings and call
     * setError() as necessary.</p>
     */
    public void verifySettings() {
    }


    /**
     * Subclasses can use this to throw the requisite exception
     * in isSelected() in the case of an error condition.
     */
    public void validate() {
        verifySettings();
        if (getError() != null) {
            throw new BuildException(errmsg);
        }
    }

    /**
     * Method that each selector will implement to create their
     * selection behaviour. If there is a problem with the setup
     * of a selector, it can throw a BuildException to indicate
     * the problem.
     *
     * @param basedir A java.io.File object for the base directory
     * @param filename The name of the file to check
     * @param file A File object for this filename
     * @return whether the file should be selected or not
     */
    public abstract boolean isSelected(File basedir, String filename,
            File file);

}