/*

 *   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;

	}

}