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/* ====================================================================
 * 
 * The ObjectStyle Group Software License, version 1.1
 * ObjectStyle Group - http://objectstyle.org/
 * 
 * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
 * of the software. 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 independent contributors
 *    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 * 
 * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
 *    or promote products derived from this software without prior written
 *    permission. For written permission, email
 *    "andrus at objectstyle dot org".
 * 
 * 5. Products derived from this software may not be called "ObjectStyle"
 *    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
 *    names without prior written permission.
 * 
 * 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 OBJECTSTYLE GROUP 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 and hosted on ObjectStyle Group web site.  For more
 * information on the ObjectStyle Group, please see
 * .
 */
package org.objectstyle.cayenne.util;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A collection of utility methods related to regular expressions processing.
 * 
 * @since 1.2
 * @author Andrus Adamchik
 */
class RegexUtil {

    static final Pattern BACKSLASH = Pattern.compile("\\\\");
    static final Pattern DOT = Pattern.compile("\\.");

    /**
     * Replaces all backslashes "\" with forward slashes "/". Convenience method to
     * convert path Strings to URI format.
     */
    static String substBackslashes(String string) {
        if (string == null) {
            return null;
        }

        Matcher matcher = BACKSLASH.matcher(string);
        return matcher.find() ? matcher.replaceAll("\\/") : string;
    }

    /**
     * Returns package name for the Java class as a path separated with forward slash
     * ("/"). Method is used to lookup resources that are located in package
     * subdirectories. For example, a String "a/b/c" will be returned for class name
     * "a.b.c.ClassName".
     */
    static String getPackagePath(String className) {
        if (className == null) {
            return "";
        }

        Matcher matcher = DOT.matcher(className);
        if (matcher.find()) {
            String path = matcher.replaceAll("\\/");
            return path.substring(0, path.lastIndexOf("/"));
        }
        else {
            return "";
        }
    }

    /**
     * Converts a SQL-style pattern to a valid Perl regular expression. E.g.:
     * 
     * "billing_%" will become ^billing_.*$
     * 
     * "user?" will become ^user.?$
     */
    static String sqlPatternToRegex(String pattern) {
        if (pattern == null) {
            throw new NullPointerException("Null pattern.");
        }

        if (pattern.length() == 0) {
            throw new IllegalArgumentException("Empty pattern.");
        }

        StringBuffer buffer = new StringBuffer();

        // convert * into regex syntax
        // e.g. abc*x becomes ^abc.*x$
        // or abc?x becomes ^abc.?x$
        buffer.append("^");
        for (int j = 0; j < pattern.length(); j++) {
            char nextChar = pattern.charAt(j);
            if (nextChar == '%') {
                nextChar = '*';
            }

            if (nextChar == '*' || nextChar == '?') {
                buffer.append('.');
            }
            // escape special chars
            else if (nextChar == '.'
                    || nextChar == '/'
                    || nextChar == '$'
                    || nextChar == '^') {
                buffer.append('\\');
            }

            buffer.append(nextChar);
        }

        buffer.append("$");
        return buffer.toString();
    }

    private RegexUtil() {
        super();
    }
}