/*******************************************************************************
 * Copyright (c) 2011, 2012, 2013, 2014 Red Hat, Inc.
 *  All rights reserved.
 * This program is made available under the terms of the
 * Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * Red Hat, Inc. - initial API and implementation
 *
 ******************************************************************************/

package org.kie.eclipse.server;

import java.io.UnsupportedEncodingException;

/**
 * <p>
 * Encodes and decodes to and from Base64 notation.
 * </p>
 * <p>
 * I am placing this code in the Public Domain. Do with it as you will. This
 * software comes with no guarantees or warranties but with plenty of
 * well-wishing instead! Please visit <a
 * href="http://iharder.net/base64">http://iharder.net/base64</a> periodically
 * to check for updates or to contribute improvements.
 * </p>
 *
 * @author Robert Harder
 * @author rob@iharder.net
 * @version 2.3.7
 */
public class Base64Util {

	/** The equals sign (=) as a byte. */
	private final static byte EQUALS_SIGN = (byte) '=';

	/** Preferred encoding. */
	private final static String PREFERRED_ENCODING = "US-ASCII";

	/** The 64 valid Base64 values. */
	private final static byte[] _STANDARD_ALPHABET = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E',
			(byte) 'F', (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
			(byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W',
			(byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f',
			(byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o',
			(byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x',
			(byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6',
			(byte) '7', (byte) '8', (byte) '9', (byte) '+', (byte) '/' };

	/** Defeats instantiation. */
	private Base64Util() {
	}

	/**
	 * <p>
	 * Encodes up to three bytes of the array <var>source</var> and writes the
	 * resulting four Base64 bytes to <var>destination</var>. The source and
	 * destination arrays can be manipulated anywhere along their length by
	 * specifying <var>srcOffset</var> and <var>destOffset</var>. This method
	 * does not check to make sure your arrays are large enough to accomodate
	 * <var>srcOffset</var> + 3 for the <var>source</var> array or
	 * <var>destOffset</var> + 4 for the <var>destination</var> array. The
	 * actual number of significant bytes in your array is given by
	 * <var>numSigBytes</var>.
	 * </p>
	 * <p>
	 * This is the lowest level of the encoding methods with all possible
	 * parameters.
	 * </p>
	 *
	 * @param source the array to convert
	 * @param srcOffset the index where conversion begins
	 * @param numSigBytes the number of significant bytes in your array
	 * @param destination the array to hold the conversion
	 * @param destOffset the index where output will be put
	 * @return the <var>destination</var> array
	 * @since 1.3
	 */
	private static byte[] encode3to4(byte[] source, int srcOffset, int numSigBytes, byte[] destination, int destOffset) {

		byte[] ALPHABET = _STANDARD_ALPHABET;

		int inBuff = (numSigBytes > 0 ? ((source[srcOffset] << 24) >>> 8) : 0)
				| (numSigBytes > 1 ? ((source[srcOffset + 1] << 24) >>> 16) : 0)
				| (numSigBytes > 2 ? ((source[srcOffset + 2] << 24) >>> 24) : 0);

		switch (numSigBytes) {
		case 3:
			destination[destOffset] = ALPHABET[(inBuff >>> 18)];
			destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
			destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
			destination[destOffset + 3] = ALPHABET[(inBuff) & 0x3f];
			return destination;

		case 2:
			destination[destOffset] = ALPHABET[(inBuff >>> 18)];
			destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
			destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
			destination[destOffset + 3] = EQUALS_SIGN;
			return destination;

		case 1:
			destination[destOffset] = ALPHABET[(inBuff >>> 18)];
			destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
			destination[destOffset + 2] = EQUALS_SIGN;
			destination[destOffset + 3] = EQUALS_SIGN;
			return destination;

		default:
			return destination;
		}
	}

	/**
	 * Encode string as a byte array in Base64 annotation.
	 *
	 * @param string
	 * @return The Base64-encoded data as a string
	 */
	public static String encode(String string) {
		byte[] bytes;
		try {
			bytes = string.getBytes(PREFERRED_ENCODING);
		} catch (UnsupportedEncodingException uee) {
			bytes = string.getBytes();
		}
		return encodeBytes(bytes);
	}

	/**
	 * Encodes a byte array into Base64 notation.
	 *
	 * @param source The data to convert
	 * @return The Base64-encoded data as a String
	 * @throws NullPointerException if source array is null
	 * @throws IllegalArgumentException if source array, offset, or length are
	 *             invalid
	 * @since 2.0
	 */
	public static String encodeBytes(byte[] source) {
		return encodeBytes(source, 0, source.length);
	}

	/**
	 * Encodes a byte array into Base64 notation.
	 *
	 * @param source The data to convert
	 * @param off Offset in array where conversion should begin
	 * @param len Length of data to convert
	 * @return The Base64-encoded data as a String
	 * @throws NullPointerException if source array is null
	 * @throws IllegalArgumentException if source array, offset, or length are
	 *             invalid
	 * @since 2.0
	 */
	public static String encodeBytes(byte[] source, int off, int len) {
		byte[] encoded = encodeBytesToBytes(source, off, len);
		try {
			return new String(encoded, PREFERRED_ENCODING);
		} catch (UnsupportedEncodingException uee) {
			return new String(encoded);
		}
	}

	/**
	 * Similar to {@link #encodeBytes(byte[], int, int)} but returns a byte
	 * array instead of instantiating a String. This is more efficient if you're
	 * working with I/O streams and have large data sets to encode.
	 *
	 *
	 * @param source The data to convert
	 * @param off Offset in array where conversion should begin
	 * @param len Length of data to convert
	 * @return The Base64-encoded data as a String if there is an error
	 * @throws NullPointerException if source array is null
	 * @throws IllegalArgumentException if source array, offset, or length are
	 *             invalid
	 * @since 2.3.1
	 */
	public static byte[] encodeBytesToBytes(byte[] source, int off, int len) {

		if (source == null)
			throw new NullPointerException("Cannot serialize a null array.");

		if (off < 0)
			throw new IllegalArgumentException("Cannot have negative offset: " + off);

		if (len < 0)
			throw new IllegalArgumentException("Cannot have length offset: " + len);

		if (off + len > source.length)
			throw new IllegalArgumentException(String.format(
					"Cannot have offset of %d and length of %d with array of length %d", off, len, source.length));

		// Bytes needed for actual encoding
		int encLen = (len / 3) * 4 + (len % 3 > 0 ? 4 : 0);

		byte[] outBuff = new byte[encLen];

		int d = 0;
		int e = 0;
		int len2 = len - 2;
		for (; d < len2; d += 3, e += 4)
			encode3to4(source, d + off, 3, outBuff, e);

		if (d < len) {
			encode3to4(source, d + off, len - d, outBuff, e);
			e += 4;
		}

		if (e <= outBuff.length - 1) {
			byte[] finalOut = new byte[e];
			System.arraycopy(outBuff, 0, finalOut, 0, e);
			return finalOut;
		} else
			return outBuff;
	}
}
