package com.efounder.chat.utils;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;

public class Base64Encoder extends FilterOutputStream {

	private static final char[] chars = {
	 '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', '0', '1', '2', '3', '4', '5', '6', '7',
	 '8', '9', '+', '/'
	};
	
	private int charCount;
	private int carryOver;
	
	/***
	* Constructs a new Base64 encoder that writes output to the given
	* OutputStream.
	*
	* @param out the output stream
	*/
	public Base64Encoder(OutputStream out) {
	 super(out);
	}
	
	/***
	* Writes the given byte to the output stream in an encoded form.
	*
	* @exception IOException if an I/O error occurs
	*/
	public void write(int b) throws IOException {
	 // Take 24-bits from three octets, translate into four encoded chars
	 // Break lines at 76 chars
	 // If necessary, pad with 0 bits on the right at the end
	 // Use = signs as padding at the end to ensure encodedLength % 4 == 0
	
	 // Remove the sign bit,
	 // thanks to Christian Schweingruber <chrigu@lorraine.ch>
	 if (b < 0) {
	   b += 256;
	 }
	
	 // First byte use first six bits, save last two bits
	 if (charCount % 3 == 0) {
	   int lookup = b >> 2;
	   carryOver = b & 3;        // last two bits
	   out.write(chars[lookup]);
	 }
	 // Second byte use previous two bits and first four new bits,
	 // save last four bits
	 else if (charCount % 3 == 1) {
	   int lookup = ((carryOver << 4) + (b >> 4)) & 63;
	   carryOver = b & 15;       // last four bits
	   out.write(chars[lookup]);
	 }
	 // Third byte use previous four bits and first two new bits,
	 // then use last six new bits
	 else if (charCount % 3 == 2) {
	   int lookup = ((carryOver << 2) + (b >> 6)) & 63;
	   out.write(chars[lookup]);
	   lookup = b & 63;          // last six bits
	   out.write(chars[lookup]);
	   carryOver = 0;
	 }
	 	charCount++;
	
	 // Add newline every 76 output chars (that's 57 input chars)
		if (charCount % 57 == 0) {
		  out.write('\n');
		}
	}
	
	/***
	* Writes the given byte array to the output stream in an 
	* encoded form.
	*
	* @param buf the data to be written
	* @param off the start offset of the data
	* @param len the length of the data
	* @exception IOException if an I/O error occurs
	*/
	public void write(byte[] buf, int off, int len) throws IOException {
	 // This could of course be optimized
	 for (int i = 0; i < len; i++) {
	   write(buf[off + i]);
	 }
	}
	
	/***
	* Closes the stream, this MUST be called to ensure proper padding is
	* written to the end of the output stream.
	*
	* @exception IOException if an I/O error occurs
	*/
	public void close() throws IOException {
	 // Handle leftover bytes
	 if (charCount % 3 == 1) {  // one leftover
	   int lookup = (carryOver << 4) & 63;
	   out.write(chars[lookup]);
	   out.write('=');
	   out.write('=');
	 }
	 else if (charCount % 3 == 2) {  // two leftovers
	   int lookup = (carryOver << 2) & 63;
	   out.write(chars[lookup]);
	   out.write('=');
	 }
	 super.close();
	}
	
	/***
	* Returns the encoded form of the given unencoded string.  The encoder
	* uses the ISO-8859-1 (Latin-1) encoding to convert the string to bytes.
	* For greater control over the encoding, encode the string to bytes
	* yourself and use encode(byte[]).
	*
	* @param unencoded the string to encode
	* @return the encoded form of the unencoded string
	*/
	public static String encode(String unencoded) {
	 byte[] bytes = null;
	 try {
	   bytes = unencoded.getBytes("UTF-8");
	 }
	 catch (UnsupportedEncodingException ignored) { }
	 return encode(bytes);
	}
	
	/***
	* Returns the encoded form of the given unencoded string.
	*
	* @param bytes the bytes to encode
	* @return the encoded form of the unencoded string
	*/
	public static String encode(byte[] bytes) {
	 ByteArrayOutputStream out = 
	   new ByteArrayOutputStream((int) (bytes.length * 1.37));
	 Base64Encoder encodedOut = new Base64Encoder(out);
	 
	 try {
	   encodedOut.write(bytes);
	   encodedOut.close();
	
	   return out.toString("UTF-8");
	 }
	 catch (IOException ignored) { return null; }
	}
	
	public static void main(String[] args) throws Exception {
	 if (args.length != 1) {
	   System.err.println(
	     "Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");
	   return;
	 }
	
	 Base64Encoder encoder = null;
	 BufferedInputStream in = null;
	 try {
	   encoder = new Base64Encoder(System.out);
	   in = new BufferedInputStream(new FileInputStream(args[0]));
	
	   byte[] buf = new byte[4 * 1024];  // 4K buffer
	   int bytesRead;
	   while ((bytesRead = in.read(buf)) != -1) {
	     encoder.write(buf, 0, bytesRead);
	   }
	 }
	 finally {
	   if (in != null) in.close();
	   if (encoder != null) encoder.close();
	 }
	}
}
