/* (c) 2014 Open Source Geospatial Foundation - all rights reserved
 * (c) 2001 - 2013 OpenPlans
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geoserver.security.password;

import java.security.SecureRandom;
import java.util.logging.Logger;

import org.geotools.util.logging.Logging;

/**
 * Class for generating random passwords using {@link SecureRandom}.
 * <p>
 * The password alphabet is {@link #PRINTABLE_ALPHABET}. Since the alphabet is not really big, the 
 * length of the password is important.
 * </p>
 *
 * @author christian
 */
public class RandomPasswordProvider {

    /** logger */
    static protected Logger LOGGER = Logging.getLogger("org.geoserver.security");

    /** alphabet */
    public static final char[] PRINTABLE_ALPHABET = {
        '!','\"','#','$','%','&','\'','(',
        ')','*','+',',','-','.','/','0',
        '1','2','3','4','5','6','7','8',
        '9',':',';','<','?','@','A','B',
        'C','D','E','F','G','H','I','J',
        'K','L','M','N','O','P','Q','R',
        'S','T','U','V','W','X','Y','Z',
        '[','\\',']','^','_','`','a','b',
        'c','d','e','f','g','h','i','j',
        'k','l','m','n','o','p','q','r',
        's','t','u','v','w','x','y','z',
        '{','|','}','~',
    };

    
    
    /**
     * The default password length assures a key strength of 2 ^ 261
     * {@link #PRINTABLE_ALPHABET} has 92 characters
     * ln (92 ^ 40 ) / ln (2) = 260.942478242
     */
    public static int DefaultPasswordLength = 40;
    
    /**
     * Creates a random password of the specified length, if length <=0, return <code>null</code>
     */
    public char[] getRandomPassword (int length) {
        if (length <=0) 
            return null; 
        char[] buff = new char[length];
        getRandomPassword(buff);
        return buff;
    }
    
    public char[] getRandomPasswordWithDefaultLength () {
        char[] buff = new char[DefaultPasswordLength];
        getRandomPassword(buff);
        return buff;
    }


    /**
     * Creates a random password filling the specified character array.
     */
    public void getRandomPassword(char[] buff) {
        SecureRandom random = new SecureRandom();
        for (int i = 0;i< buff.length;i++) {
            int index = random.nextInt() % PRINTABLE_ALPHABET.length;
            if (index <0)
                index+=PRINTABLE_ALPHABET.length;
            buff[i]=PRINTABLE_ALPHABET[index];
        }
    }
    /**
     * Creates a random password filling the specified byte array.
     */
    public void getRandomPassword(byte[] buff) {
        SecureRandom random = new SecureRandom();
        for (int i = 0;i< buff.length;i++) {
            int index = random.nextInt() % PRINTABLE_ALPHABET.length;
            if (index <0)
                index+=PRINTABLE_ALPHABET.length;
            buff[i]=(byte) PRINTABLE_ALPHABET[index];
        }
    }
}