/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 java.util.regex.MatchResult;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import org.apache.commons.net.ftp.FTPFileEntryParserImpl;

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 class for all regular expression based FTPFileEntryParser classes
/**
 * 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 class for all regular expression based FTPFileEntryParser classes
 */
public abstract class RegexFTPFileEntryParserImpl extends
        FTPFileEntryParserImpl {
    
internal pattern the matcher tries to match, representing a file
entry
/**
     * internal pattern the matcher tries to match, representing a file
     * entry
     */
    private Pattern pattern = null;

    
internal match result used by the parser
/**
     * 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.
/**
     * 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 Matcher _matcher_ = null;

    
The constructor for a RegexFTPFileEntryParserImpl object.
The expression is compiled with flags = 0.
Params:
regex –  The regular expression with which this object is
initialized.
Throws:
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./**
     * The constructor for a RegexFTPFileEntryParserImpl object.
     * The expression is compiled with flags = 0.
     *
     * @param regex  The regular expression with which this object is
     * initialized.
     *
     * @throws 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();
        compileRegex(regex, 0);
    }

    
The constructor for a RegexFTPFileEntryParserImpl object.
Params:
regex –  The regular expression with which this object is
initialized.
flags – the flags to apply, see Pattern.compile(String, int). Use 0 for none.
Throws:
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.
Since:
3.4/**
     * The constructor for a RegexFTPFileEntryParserImpl object.
     *
     * @param regex  The regular expression with which this object is
     * initialized.
     * @param flags the flags to apply, see {@link Pattern#compile(String, int)}. Use 0 for none.
     *
     * @throws 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.
     * @since 3.4
     */
    public RegexFTPFileEntryParserImpl(String regex, final int flags) {
        super();
        compileRegex(regex, flags);
    }

    
Convenience method delegates to the internal MatchResult's matches()
method.
Params:
s – the String to be matched
Returns:
true if s matches this object's regular expression./**
     * 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;
        _matcher_ = pattern.matcher(s);
        if (_matcher_.matches()) {
            this.result = _matcher_.toMatchResult();
        }
        return null != this.result;
    }

    
Convenience method
Returns:
the number of groups() in the internal MatchResult./**
     * Convenience method
     *
     * @return the number of groups() in the internal MatchResult.
     */

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

    
Convenience method delegates to the internal MatchResult's group()
method.
Params:
matchnum – match group number to be retrieved
Returns:
the content of the matchnum'th group of the internal
        match or null if this method is called without a match having
        been made./**
     * 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.
Returns:
a string shows each match group by number./**
     * For debugging purposes - returns a string shows each match group by
     * number.
     *
     * @return a string shows each match group by number.
     */

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

    
Alter the current regular expression being utilised for entry parsing and create a new Pattern instance. 
Params:
regex – The new regular expression
Throws:
IllegalArgumentException – if the regex cannot be compiled
Returns:
 true
Since:
2.0/**
     * Alter the current regular expression being utilised for entry parsing
     * and create a new {@link Pattern} instance.
     * @param regex The new regular expression
     * @return  true
     * @since 2.0
     * @throws IllegalArgumentException if the regex cannot be compiled
     */
    public boolean setRegex(final String regex) {
        compileRegex(regex, 0);
        return true;
    }


    
Alter the current regular expression being utilised for entry parsing and create a new Pattern instance. 
Params:
regex – The new regular expression
flags – the flags to apply, see Pattern.compile(String, int). Use 0 for none.
Throws:
IllegalArgumentException – if the regex cannot be compiled
Returns:
 true
Since:
3.4/**
     * Alter the current regular expression being utilised for entry parsing
     * and create a new {@link Pattern} instance.
     * @param regex The new regular expression
     * @param flags the flags to apply, see {@link Pattern#compile(String, int)}. Use 0 for none.
     * @return  true
     * @since 3.4
     * @throws IllegalArgumentException if the regex cannot be compiled
     */
    public boolean setRegex(final String regex, final int flags) {
        compileRegex(regex, flags);
        return true;
    }

    
Compile the regex and store the Pattern. This is an internal method to do the work so the constructor does not have to call an overrideable method. 
Params:
regex – the expression to compile
flags – the flags to apply, see Pattern.compile(String, int). Use 0 for none.
Throws:
IllegalArgumentException – if the regex cannot be compiled/**
     * Compile the regex and store the {@link Pattern}.
     *
     * This is an internal method to do the work so the constructor does not
     * have to call an overrideable method.
     *
     * @param regex the expression to compile
     * @param flags the flags to apply, see {@link Pattern#compile(String, int)}. Use 0 for none.
     * @throws IllegalArgumentException if the regex cannot be compiled
     */
    private void compileRegex(final String regex, final int flags) {
        try {
            pattern = Pattern.compile(regex, flags);
        } catch (PatternSyntaxException pse) {
            throw new IllegalArgumentException("Unparseable regex supplied: " + regex);
        }
    }
}