package org.openslx.imagemaster.util;

import java.security.SecureRandom;

/**
 * Generate secure random strings
 * 
 */
public class RandomString
{
	private static final String lettersSpecial = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890+-$%&/()=?@";
	private static final String letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
	private static final SecureRandom random = new SecureRandom();

	/**
	 * Generate a random string.
	 * 
	 * @param length the length of the string
	 * @param specialChars whether to use special charachters or not
	 * @return the generated string
	 */
	public static String generate( int length, boolean specialChars )
	{
		String used = ( specialChars ) ? lettersSpecial : letters;
		String result = "";
		for ( int i = 0; i < length; i++ ) {
			int index = (int) ( random.nextDouble() * used.length() );
			result += used.substring( index, index + 1 );
		}
		return result;
	}

	/**
	 * Generate random binary data.
	 * 
	 * @param length number of bytes to generate
	 * @return the generated binary data, as byte array
	 */
	public static byte[] generateBinary( int length )
	{
		byte[] result = new byte[ length ];
		random.nextBytes( result );
		return result;
	}

}