/*
 * Copyright 2004-2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.ftp.parser;
import org.apache.commons.net.ftp.FTPFileEntryParserImpl;
import org.apache.oro.text.regex.MalformedPatternException;
import org.apache.oro.text.regex.MatchResult;
import org.apache.oro.text.regex.Pattern;
import org.apache.oro.text.regex.PatternMatcher;
import org.apache.oro.text.regex.Perl5Compiler;
import org.apache.oro.text.regex.Perl5Matcher;



/**
 * This abstract class implements both the older FTPFileListParser and
 * newer FTPFileEntryParser interfaces with default functionality.
 * All the classes in the parser subpackage inherit from this.
 *
 * This is the base for all regular based FTPFileEntryParser
 *
 * @author Steve Cohen <scohen@apache.org>
 */
public abstract class RegexFTPFileEntryParserImpl extends FTPFileEntryParserImpl
{
    /**
     * internal pattern the matcher tries to match, representing a file
     * entry
     */
    private Pattern pattern = null;

    /**
     * internal match result used by the parser
     */
    private MatchResult result = null;

    /**
     * Internal PatternMatcher object used by the parser.  It has protected
     * scope in case subclasses want to make use of it for their own purposes.
     */
    protected PatternMatcher _matcher_ = null;

    /**
     * The constructor for a RegexFTPFileEntryParserImpl object.
     *
     * @param regex  The regular expression with which this object is
     * initialized.
     *
     * @exception IllegalArgumentException
     * Thrown if the regular expression is unparseable.  Should not be seen in
     * normal conditions.  It it is seen, this is a sign that a subclass has
     * been created with a bad regular expression.   Since the parser must be
     * created before use, this means that any bad parser subclasses created
     * from this will bomb very quickly,  leading to easy detection.
     */

    public RegexFTPFileEntryParserImpl(String regex)
    {
        super();
        try
        {
            _matcher_ = new Perl5Matcher();
            pattern   = new Perl5Compiler().compile(regex);
        }
        catch (MalformedPatternException e)
        {
            throw new IllegalArgumentException (
               "Unparseable regex supplied:  " + regex);
        }
    }

    /**
     * Convenience method delegates to the internal MatchResult's matches()
     * method.
     *
     * @param s the String to be matched
     * @return true if s matches this object's regular expression.
     */

    public boolean matches(String s)
    {
        this.result = null;
        if (_matcher_.matches(s.trim(), this.pattern))
        {
            this.result = _matcher_.getMatch();
        }
        return null != this.result;
    }



    /**
     * Convenience method delegates to the internal MatchResult's groups()
     * method.
     *
     * @return the number of groups() in the internal MatchResult.
     */

    public int getGroupCnt()
    {
        if (this.result == null)
        {
            return 0;
        }
        return this.result.groups();
    }



    /**
     * Convenience method delegates to the internal MatchResult's group()
     * method.
     *
     * @param matchnum match group number to be retrieved
     *
     * @return the content of the <code>matchnum'th<code> group of the internal
     *         match or null if this method is called without a match having
     *         been made.
     */
    public String group(int matchnum)
    {
        if (this.result == null)
        {
            return null;
        }
        return this.result.group(matchnum);
    }

    /**
     * For debugging purposes - returns a string shows each match group by
     * number.
     *
     * @return a string shows each match group by number.
     */

    public String getGroupsAsString()
    {
        StringBuffer b = new StringBuffer();
        for (int i = 1; i <= this.result.groups(); i++)
        {
            b.append(i).append(") ").append(this.result.group(i))
                .append(System.getProperty("line.separator"));
        }
        return b.toString();
    }
    
}