/*

 *   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.IOException;

import java.io.InputStream;

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

/**

 * InputStream that can change its decoding charset while reading from the

 * underlying byte based stream.

 * @author Christian Lins

 * @since sonews/0.5.0

 */

public class VarCharsetReader

{

  private final ByteBuffer buf = ByteBuffer.allocate(4096);

  private InputStream in;

  public VarCharsetReader(final InputStream in)

  {

    if(in == null)

    {

      throw new IllegalArgumentException("null InputStream");

    }

    this.in = in;

  }

  /**

   * Reads up to the next newline character and returns the line as String.

   * The String is decoded using the given charset.

   */

  public String readLine(Charset charset)

    throws IOException

  {    

    byte[] byteBuf = new byte[1];

    String bufStr;

    for(;;)

    {

      int read = this.in.read(byteBuf);

      if(read == 0)

      {

        continue;

      }

      else if(read == -1)

      {

        this.in = null;

        bufStr  = new String(this.buf.array(), 0, this.buf.position(), charset);

        break;

      }

      else if(byteBuf[0] == 10) // Is this safe? \n

      {

        bufStr  = new String(this.buf.array(), 0, this.buf.position(), charset);

        break;

      }

      else if(byteBuf[0] == 13) // \r

      { // Skip

        continue;

      }

      else

      {

        this.buf.put(byteBuf[0]);

      }

    }

    this.buf.clear();

    return bufStr;

  }

}