/*
XOWA: the XOWA Offline Wiki Application
Copyright (C) 2012 gnosygnu@gmail.com

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
package gplx.texts; import gplx.*;
public class Base32Converter {
	public static String EncodeString(String orig) {return Encode(Bry_.new_utf8_(orig));}
	public static String Encode(byte[] raw) {
		int i = 0, index = 0, digit = 0; int currByte, nextByte;
		int rawLen = Array_.Len(raw);
		char[] ary = new char[(rawLen + 7) * 8 / 5]; int aryPos = 0;
		while (i < rawLen) {
			currByte = (raw[i] >= 0) ? raw[i] : raw[i] + 256; // unsign; java converts char 128+ -> byte -128
			if (index > 3) {		/* Is the curPath digit going to span a byte boundary? */
				if ((i+1) < rawLen) 
					nextByte = (raw[i+1] >= 0) ? raw[i+1] : (raw[i+1] + 256);
				else
					nextByte = 0;
			
				digit = currByte & (0xFF >> index);
				index = (index + 5) % 8;
				digit <<= index;
				digit |= nextByte >> (8 - index);
				i++;
			}
			else {
				digit = (currByte >> (8 - (index + 5))) & 0x1F;
				index = (index + 5) % 8;
				if (index == 0) i++;
			}
			ary[aryPos++] = String_.CharAt(chars, digit);
		}
		return new String(ary, 0, aryPos);
	}
	public static String DecodeString(String orig) {return String_.new_utf8_(Decode(orig));}
	public static byte[] Decode(String raw) {
		int i, index, lookup, offset; byte digit;
		int rawLen = String_.Len(raw);
		int rvLen = rawLen * 5 / 8;
		byte[] rv = new byte[rvLen];
		for (i = 0, index = 0, offset = 0; i < rawLen; i++) {
			lookup = String_.CharAt(raw, i) - '0';
			if (lookup < 0 || lookup >= valsLen) continue; /* Skip any char outside the lookup table */			
			digit = vals[lookup];
			if (digit == 0x7F) continue;		/* If this digit is not in the table, ignore it */

			if (index <= 3) {
				index = (index + 5) % 8;
				if (index == 0) {
					rv[offset] |= digit;
					offset++;
					if(offset >= rvLen) break;
				}
				else
					rv[offset] |= (byte)(digit << (8 - index));
			}
			else {
				index = (index + 5) % 8;
				rv[offset] |= (byte)(digit >> index);
				offset++;
			
				if(offset >= rvLen) break;
				rv[offset] |= (byte)(digit << (8 - index));
			}
		}
		return rv;
	}
	static String chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";	
	static int valsLen = 80;
	static byte[] vals = {
							 0x7F,0x7F,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F, // '0', '1', '2', '3', '4', '5', '6', '7'
							 0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F, // '8', '9', ':', ';', '<', '=', '>', '?'
							 0x7F,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G'
							 0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O'
							 0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W'
							 0x17,0x18,0x19,0x7F,0x7F,0x7F,0x7F,0x7F, // 'X', 'Y', 'Z', '[', '\', ']', '^', '_'
							 0x7F,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g'
							 0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o'
							 0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'p', 'q', 'r', 's', 't', 'u', 'v', 'w'
							 0x17,0x18,0x19,0x7F,0x7F,0x7F,0x7F,0x7F  // 'x', 'y', 'z', '{', '|', '}', '~', 'DEL'
						 };
}
/*
source:	Azraeus excerpt in java
		http://www.koders.com/java/fidA4D6F0DF43E6E9A6B518762366AB7232C14E9DB7.aspx
*/
