/*************************************************************************
 *                                                                       *
 *  SignServer: The OpenSource Automated Signing Server                  *
 *                                                                       *
 *  This software is free software; you can redistribute it and/or       *
 *  modify it under the terms of the GNU Lesser General Public           *
 *  License as published by the Free Software Foundation; either         *
 *  version 2.1 of the License, or any later version.                    *
 *                                                                       *
 *  See terms of license at gnu.org.                                     *
 *                                                                       *
 *************************************************************************/
package org.signserver.common.util;

import java.security.SecureRandom;
import java.util.Random;

/**
 * Ouputs a list of randomly generated passwords.
 *
 * @author Markus Kilas
 * @version $Id: RandomPasswordGenerator.java 1829 2011-08-10 11:50:45Z netmackan $
 */
public final class RandomPasswordGenerator {

    /** Alphanumeric characters. */
    public static final String ALPHANUMERIC
            = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

    /** Default number for passwords to generate. */
    private static final int DEFAULT_NUM_WORDS = 1;

    /** Default number of charcters in each password. */
    private static final int DEFAULT_NUM_CHARACTERS = 8;

    private static RandomPasswordGenerator instance;

    // Secure random
    final Random random = new SecureRandom();

    /** Singleton. */
    private RandomPasswordGenerator() {
    }

    public static RandomPasswordGenerator getInstance() {
        if (instance == null) {
            instance = new RandomPasswordGenerator();
        }
        return instance;
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        // Default values
        String alphabet = ALPHANUMERIC;
        int words = DEFAULT_NUM_WORDS;
        int characters = DEFAULT_NUM_CHARACTERS;

        // Check number of arguments
        if (args.length < 1 || args.length > 4 || !"generate".equals(args[0])) {
            System.err.println("USAGE: java RandPassGen generate"
                    + " [LENGTH] [WORDS] [ALPHABETH]");
            System.err.println("Example:");
            System.err.println("randompasswordgenerator generate 9 1 "
                    + ALPHANUMERIC);
            return;
        }

        // Read arguments
        if (args.length > 1) {
            characters = Integer.parseInt(args[1]);
        }
        if (args.length > 2) {
            words = Integer.parseInt(args[2]);
        }
        if (args.length > 3) {
            alphabet = args[3];
        }

        // Generate all passwords
        for (int word = 0; word < words; word++) {
            System.out.println(RandomPasswordGenerator.getInstance().generate(characters,
                    alphabet));
        }
    }

    public char[] generate(final int length) {
        return fill(new char[length]);
    }

    public char[] generate(final int length, final String alphabeth) {
        return fill(new char[length], alphabeth);
    }

    public char[] fill(final char[] buff) {
        return fill(buff, ALPHANUMERIC);
    }

    public char[] fill(final char[] buff, final String alphabeth) {
        for (int i = 0; i < buff.length; i++) {
            buff[i] = alphabeth.charAt(random.nextInt(alphabeth.length()));
        }
        return buff;
    }
}