/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.io;

import java.io.IOException;
import java.io.Writer;

DotTerminatedMessageWriter is a class used to write messages to a
server that are terminated by a single dot followed by a
<CR><LF>
sequence and with double dots appearing at the begining of lines which
do not signal end of message yet start with a dot.  Various Internet
protocols such as NNTP and POP3 produce messages of this type.

This class handles the doubling of line-starting periods,
converts single linefeeds to NETASCII newlines, and on closing
will send the final message terminator dot and NETASCII newline
sequence.
/***
 * DotTerminatedMessageWriter is a class used to write messages to a
 * server that are terminated by a single dot followed by a
 * &lt;CR&gt;&lt;LF&gt;
 * sequence and with double dots appearing at the begining of lines which
 * do not signal end of message yet start with a dot.  Various Internet
 * protocols such as NNTP and POP3 produce messages of this type.
 * <p>
 * This class handles the doubling of line-starting periods,
 * converts single linefeeds to NETASCII newlines, and on closing
 * will send the final message terminator dot and NETASCII newline
 * sequence.
 *
 *
 ***/

public final class DotTerminatedMessageWriter extends Writer
{
    private static final int __NOTHING_SPECIAL_STATE = 0;
    private static final int __LAST_WAS_CR_STATE = 1;
    private static final int __LAST_WAS_NL_STATE = 2;

    private int __state;
    private Writer __output;


    
Creates a DotTerminatedMessageWriter that wraps an existing Writer
output destination.
Params:
output –  The Writer output destination to write the message./***
     * Creates a DotTerminatedMessageWriter that wraps an existing Writer
     * output destination.
     *
     * @param output  The Writer output destination to write the message.
     ***/
    public DotTerminatedMessageWriter(Writer output)
    {
        super(output);
        __output = output;
        __state = __NOTHING_SPECIAL_STATE;
    }


    
Writes a character to the output.  Note that a call to this method
may result in multiple writes to the underling Writer in order to
convert naked linefeeds to NETASCII line separators and to double
line-leading periods.  This is transparent to the programmer and
is only mentioned for completeness.
Params:
ch –  The character to write.
Throws:
IOException –  If an error occurs while writing to the
           underlying output./***
     * Writes a character to the output.  Note that a call to this method
     * may result in multiple writes to the underling Writer in order to
     * convert naked linefeeds to NETASCII line separators and to double
     * line-leading periods.  This is transparent to the programmer and
     * is only mentioned for completeness.
     *
     * @param ch  The character to write.
     * @throws IOException  If an error occurs while writing to the
     *            underlying output.
     ***/
    @Override
    public void write(int ch) throws IOException
    {
        synchronized (lock)
        {
            switch (ch)
            {
            case '\r':
                __state = __LAST_WAS_CR_STATE;
                __output.write('\r');
                return ;
            case '\n':
                if (__state != __LAST_WAS_CR_STATE) {
                    __output.write('\r');
                }
                __output.write('\n');
                __state = __LAST_WAS_NL_STATE;
                return ;
            case '.':
                // Double the dot at the beginning of a line
                if (__state == __LAST_WAS_NL_STATE) {
                    __output.write('.');
                }
                //$FALL-THROUGH$
            default:
                __state = __NOTHING_SPECIAL_STATE;
                __output.write(ch);
                return ;
            }
        }
    }


    
Writes a number of characters from a character array to the output
starting from a given offset.
Params:
buffer –  The character array to write.
offset –  The offset into the array at which to start copying data.
length –  The number of characters to write.
Throws:
IOException – If an error occurs while writing to the underlying
           output./***
     * Writes a number of characters from a character array to the output
     * starting from a given offset.
     *
     * @param buffer  The character array to write.
     * @param offset  The offset into the array at which to start copying data.
     * @param length  The number of characters to write.
     * @throws IOException If an error occurs while writing to the underlying
     *            output.
     ***/
    @Override
    public void write(char[] buffer, int offset, int length) throws IOException
    {
        synchronized (lock)
        {
            while (length-- > 0) {
                write(buffer[offset++]);
            }
        }
    }


    
Writes a character array to the output.
Params:
buffer –  The character array to write.
Throws:
IOException – If an error occurs while writing to the underlying
           output./***
     * Writes a character array to the output.
     *
     * @param buffer  The character array to write.
     * @throws IOException If an error occurs while writing to the underlying
     *            output.
     ***/
    @Override
    public void write(char[] buffer) throws IOException
    {
        write(buffer, 0, buffer.length);
    }


    
Writes a String to the output.
Params:
string –  The String to write.
Throws:
IOException – If an error occurs while writing to the underlying
           output./***
     * Writes a String to the output.
     *
     * @param string  The String to write.
     * @throws IOException If an error occurs while writing to the underlying
     *            output.
     ***/
    @Override
    public void write(String string) throws IOException
    {
        write(string.toCharArray());
    }


    
Writes part of a String to the output starting from a given offset.
Params:
string –  The String to write.
offset –  The offset into the String at which to start copying data.
length –  The number of characters to write.
Throws:
IOException – If an error occurs while writing to the underlying
           output./***
     * Writes part of a String to the output starting from a given offset.
     *
     * @param string  The String to write.
     * @param offset  The offset into the String at which to start copying data.
     * @param length  The number of characters to write.
     * @throws IOException If an error occurs while writing to the underlying
     *            output.
     ***/
    @Override
    public void write(String string, int offset, int length) throws IOException
    {
        write(string.toCharArray(), offset, length);
    }


    
Flushes the underlying output, writing all buffered output.
Throws:
IOException – If an error occurs while writing to the underlying
           output./***
     * Flushes the underlying output, writing all buffered output.
     *
     * @throws IOException If an error occurs while writing to the underlying
     *            output.
     ***/
    @Override
    public void flush() throws IOException
    {
        synchronized (lock)
        {
            __output.flush();
        }
    }


    
Flushes the underlying output, writing all buffered output, but doesn't
actually close the underlying stream.  The underlying stream may still
be used for communicating with the server and therefore is not closed.
Throws:
IOException – If an error occurs while writing to the underlying
           output or closing the Writer./***
     * Flushes the underlying output, writing all buffered output, but doesn't
     * actually close the underlying stream.  The underlying stream may still
     * be used for communicating with the server and therefore is not closed.
     *
     * @throws IOException If an error occurs while writing to the underlying
     *            output or closing the Writer.
     ***/
    @Override
    public void close() throws IOException
    {
        synchronized (lock)
        {
            if (__output == null) {
                return ;
            }

            if (__state == __LAST_WAS_CR_STATE) {
                __output.write('\n');
            } else if (__state != __LAST_WAS_NL_STATE) {
                __output.write("\r\n");
            }

            __output.write(".\r\n");

            __output.flush();
            __output = null;
        }
    }

}