src/main/java/org/apache/commons/cli/PatternOptionBuilder.java

/**
 * 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.cli;

import java.io.File;
import java.io.FileInputStream;
import java.net.URL;
import java.util.Date;

/**
 * <p>Allows Options to be created from a single String.
 * The pattern contains various single character flags and via
 * an optional punctuation character, their expected type.
 * </p>
 * 
 * <table border="1">
 *   <caption>Overview of PatternOptionBuilder patterns</caption>
 *   <tr><td>a</td><td>-a flag</td></tr>
 *   <tr><td>b@</td><td>-b [classname]</td></tr>
 *   <tr><td>c&gt;</td><td>-c [filename]</td></tr>
 *   <tr><td>d+</td><td>-d [classname] (creates object via empty constructor)</td></tr>
 *   <tr><td>e%</td><td>-e [number] (creates Double/Long instance depending on existing of a '.')</td></tr>
 *   <tr><td>f/</td><td>-f [url]</td></tr>
 *   <tr><td>g:</td><td>-g [string]</td></tr>
 * </table>
 * 
 * <p>
 * For example, the following allows command line flags of '-v -p string-value -f /dir/file'.
 * The exclamation mark precede a mandatory option.
 * </p>
 *
 * <pre>
 *     Options options = PatternOptionBuilder.parsePattern("vp:!f/");
 * </pre>
 *
 * <p>
 * TODO: These need to break out to OptionType and also to be pluggable.
 * </p>
 *
 * @version $Id$
 */
public class PatternOptionBuilder
{
    /** String class */
    public static final Class<String> STRING_VALUE = String.class;

    /** Object class */
    public static final Class<Object> OBJECT_VALUE = Object.class;

    /** Number class */
    public static final Class<Number> NUMBER_VALUE = Number.class;

    /** Date class */
    public static final Class<Date> DATE_VALUE = Date.class;

    /** Class class */
    public static final Class<?> CLASS_VALUE = Class.class;

    /// can we do this one??
    // is meant to check that the file exists, else it errors.
    // ie) it's for reading not writing.

    /** FileInputStream class */
    public static final Class<FileInputStream> EXISTING_FILE_VALUE = FileInputStream.class;

    /** File class */
    public static final Class<File> FILE_VALUE = File.class;

    /** File array class */
    public static final Class<File[]> FILES_VALUE = File[].class;

    /** URL class */
    public static final Class<URL> URL_VALUE = URL.class;

    /**
     * Retrieve the class that <code>ch</code> represents.
     *
     * @param ch the specified character
     * @return The class that <code>ch</code> represents
     */
    public static Object getValueClass(char ch)
    {
        switch (ch)
        {
            case '@':
                return PatternOptionBuilder.OBJECT_VALUE;
            case ':':
                return PatternOptionBuilder.STRING_VALUE;
            case '%':
                return PatternOptionBuilder.NUMBER_VALUE;
            case '+':
                return PatternOptionBuilder.CLASS_VALUE;
            case '#':
                return PatternOptionBuilder.DATE_VALUE;
            case '<':
                return PatternOptionBuilder.EXISTING_FILE_VALUE;
            case '>':
                return PatternOptionBuilder.FILE_VALUE;
            case '*':
                return PatternOptionBuilder.FILES_VALUE;
            case '/':
                return PatternOptionBuilder.URL_VALUE;
        }

        return null;
    }

    /**
     * Returns whether <code>ch</code> is a value code, i.e.
     * whether it represents a class in a pattern.
     *
     * @param ch the specified character
     * @return true if <code>ch</code> is a value code, otherwise false.
     */
    public static boolean isValueCode(char ch)
    {
        return ch == '@'
                || ch == ':'
                || ch == '%'
                || ch == '+'
                || ch == '#'
                || ch == '<'
                || ch == '>'
                || ch == '*'
                || ch == '/'
                || ch == '!';
    }

    /**
     * Returns the {@link Options} instance represented by <code>pattern</code>.
     *
     * @param pattern the pattern string
     * @return The {@link Options} instance
     */
    public static Options parsePattern(String pattern)
    {
        char opt = ' ';
        boolean required = false;
        Class<?> type = null;

        Options options = new Options();

        for (int i = 0; i < pattern.length(); i++)
        {
            char ch = pattern.charAt(i);

            // a value code comes after an option and specifies
            // details about it
            if (!isValueCode(ch))
            {
                if (opt != ' ')
                {
                    final Option option = Option.builder(String.valueOf(opt))
                        .hasArg(type != null)
                        .required(required)
                        .type(type)
                        .build();
                    
                    // we have a previous one to deal with
                    options.addOption(option);
                    required = false;
                    type = null;
                    opt = ' ';
                }

                opt = ch;
            }
            else if (ch == '!')
            {
                required = true;
            }
            else
            {
                type = (Class<?>) getValueClass(ch);
            }
        }

        if (opt != ' ')
        {
            final Option option = Option.builder(String.valueOf(opt))
                .hasArg(type != null)
                .required(required)
                .type(type)
                .build();
            
            // we have a final one to deal with
            options.addOption(option);
        }

        return options;
    }
}