/*

  *   SONEWS News Server

  *   see AUTHORS for the list of contributors

  *

  *   This program is free software: you can redistribute it and/or modify

  *   it under the terms of the GNU 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 General Public License for more details.

  *

  *   You should have received a copy of the GNU General Public License

  *   along with this program.  If not, see <http://www.gnu.org/licenses/>.

  */

 package org.sonews.util.io;

 import java.io.FilterInputStream;

 import java.io.IOException;

 import java.io.InputStream;

 /**

  * Filter input stream for reading from SMTP (or NNTP or similar) socket

  * where lines containing single dot have special meaning – end of message.

  * 

  * @author František Kučera (frantovo.cz)

  */

 public class SMTPInputStream extends FilterInputStream {

 	public static final int CR = 0x0d;

 	public static final int LF = 0x0a;

 	public static final int DOT = 0x2e;

 	protected int last;

 	public SMTPInputStream(InputStream in) {

 		super(in);

 	}

 	/**

 	 * @return one byte as expected 

 	 * or -2 if there was line with single dot (which means end of message)

 	 * @throws IOException 

 	 */

 	@Override

 	public int read() throws IOException {

 		// read current character

 		int ch = super.read();

 		if (ch == DOT) {

 			if (last == LF) {

 				int next = super.read();

 				if (next == CR || next == LF) { // There should be CRLF, but we may accept also just LF or CR with missing LF. Or should we be more strict?

 					// <CRLF>.<CRLF> → end of current message

 					ch = -2;

 				} else {

 					// <CRLF>.… → eat one dot and return next character

 					ch = next;

 				}

 			}

 		}

 		last = ch;

 		return ch;

 	}

 	/**

 	 * @param buffer

 	 * @param offset

 	 * @param length

 	 * @return See {@link FilterInputStream#read(byte[], int, int)} or -2 (then see {@link #read(byte[])})

 	 * @throws IOException 

 	 */

 	@Override

 	public int read(byte[] buffer, int offset, int length) throws IOException {

 		if (buffer == null) {

 			throw new NullPointerException("Byte array should not be null.");

 		} else if ((offset < 0) || (offset > buffer.length) || (length < 0) || ((offset + length) > buffer.length) || ((offset + length) < 0)) {

 			throw new IndexOutOfBoundsException("Invalid offset or length.");

 		} else if (length == 0) {

 			return 0;

 		}

 		int ch = read();

 		if (ch == -1 || ch == -2) {

 			return ch;

 		}

 		buffer[offset] = (byte) ch;

 		int readCounter = 1;

 		for (; readCounter < length; readCounter++) {

 			ch = read();

 			if (ch == -1 || ch == -2) {

 				break;

 			}

 			if (buffer != null) {

 				buffer[offset + readCounter] = (byte) ch;

 			}

 		}

 		return readCounter;

 	}

 }