/*
    * DavMail POP/IMAP/SMTP/CalDav/LDAP Exchange Gateway
    * Copyright (C) 2009  Mickael Guessant
    *
    * 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 2
    * 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, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
   */
  package davmail;
  
  import davmail.exception.DavMailException;
  import davmail.exchange.ExchangeSession;
  import davmail.ui.tray.DavGatewayTray;
  import org.apache.log4j.Logger;
  
  import java.io.*;
  import java.net.Socket;
  import java.nio.charset.StandardCharsets;
  
  
  /**
   * Generic connection common to pop3 and smtp implementations
   */
  public abstract class AbstractConnection extends Thread implements Closeable {
  
      protected enum State {
          INITIAL, LOGIN, USER, PASSWORD, AUTHENTICATED, STARTMAIL, RECIPIENT, MAILDATA
      }
  
      protected static class LineReaderInputStream extends PushbackInputStream {
          final String encoding;
  
          protected LineReaderInputStream(InputStream in, String encoding) {
              super(in);
              if (encoding == null) {
                  this.encoding = "ASCII";
              } else {
                  this.encoding = encoding;
              }
          }
  
          public String readLine() throws IOException {
              ByteArrayOutputStream byteArrayOutputStream = null;
              int b;
              while ((b = read()) > -1) {
                  // Handles line ending variations
                  if (b == '\r') {
                      int next = read();
                      if (next != '\n') {
                          unread(next);
                      }
                      break;
                  } else if (b == '\n') {
                      break;
                  }
                  if (byteArrayOutputStream == null) {
                      byteArrayOutputStream = new ByteArrayOutputStream();
                  }
                  byteArrayOutputStream.write(b);
              }
              if (byteArrayOutputStream != null) {
                  return byteArrayOutputStream.toString(encoding);
              } else {
                  return null;
              }
          }
  
          /**
           * Read byteSize bytes from inputStream, return content as String.
           *
           * @param byteSize content size
           * @return content
           * @throws IOException on error
           */
          public String readContentAsString(int byteSize) throws IOException {
              return new String(readContent(byteSize), encoding);
          }
  
          /**
           * Read byteSize bytes from inputStream, return content as a byte array.
           *
           * @param byteSize content size
           * @return content
           * @throws IOException on error
           */
          public byte[] readContent(int byteSize) throws IOException {
              byte[] buffer = new byte[byteSize];
              int startIndex = 0;
              int count = 0;
             while (count >= 0 && startIndex < byteSize) {
                 count = read(buffer, startIndex, byteSize - startIndex);
                 startIndex += count;
             }
             if (startIndex < byteSize) {
                 throw new DavMailException("EXCEPTION_END_OF_STREAM");
             }
 
             return buffer;
         }
     }
 
     protected final Socket client;
 
     protected LineReaderInputStream in;
     protected OutputStream os;
     // username and password initialized through connection
     protected String userName;
     protected String password;
     // connection state
     protected State state = State.INITIAL;
     // Exchange session proxy
     protected ExchangeSession session;
 
     /**
      * Only set the thread name and socket
      *
      * @param name         thread type name
      * @param clientSocket client socket
      */
     public AbstractConnection(String name, Socket clientSocket) {
         super(name + '-' + clientSocket.getPort());
         this.client = clientSocket;
         setDaemon(true);
     }
 
     /**
      * Initialize the streams and set a thread name.
      *
      * @param name         thread type name
      * @param clientSocket client socket
      * @param encoding     socket stream encoding
      */
     public AbstractConnection(String name, Socket clientSocket, String encoding) {
         super(name + '-' + clientSocket.getPort());
         this.client = clientSocket;
         logConnection("CONNECT", "");
         try {
             in = new LineReaderInputStream(client.getInputStream(), encoding);
             os = new BufferedOutputStream(client.getOutputStream());
         } catch (IOException e) {
             close();
             DavGatewayTray.error(new BundleMessage("LOG_EXCEPTION_GETTING_SOCKET_STREAMS"), e);
         }
     }
 
     public void logConnection(String action, String userName) {
         Logger.getLogger("davmail.connection").info(action+" - "+client.getInetAddress().getHostAddress()+":"+client.getPort()+" " + userName);
     }
 
     /**
      * Send the provided message to the client followed by CRLF.
      *
      * @param message message
      * @throws IOException on error
      */
     public void sendClient(String message) throws IOException {
         sendClient(null, message);
     }
 
     /**
      * Send prefix and message to the client followed by CRLF.
      *
      * @param prefix  prefix
      * @param message message
      * @throws IOException on error
      */
     public void sendClient(String prefix, String message) throws IOException {
         if (prefix != null) {
             os.write(prefix.getBytes(StandardCharsets.UTF_8));
             DavGatewayTray.debug(new BundleMessage("LOG_SEND_CLIENT_PREFIX_MESSAGE", prefix, message));
         } else {
             DavGatewayTray.debug(new BundleMessage("LOG_SEND_CLIENT_MESSAGE", message));
         }
         os.write(message.getBytes(StandardCharsets.UTF_8));
         os.write((char) 13);
         os.write((char) 10);
         os.flush();
     }
 
     /**
      * Send all bytes to the client.
      *
      * @param messageBytes content
      * @throws IOException on error
      */
     public void sendClient(byte[] messageBytes) throws IOException {
         sendClient(messageBytes, 0, messageBytes.length);
     }
 
     /**
      * Send only bytes to the client.
      *
      * @param messageBytes content
      * @param offset       the start offset in the data.
      * @param length       the number of bytes to write.
      * @throws IOException on error
      */
     public void sendClient(byte[] messageBytes, int offset, int length) throws IOException {
         os.write(messageBytes, offset, length);
         os.flush();
     }
 
     /**
      * Read a line from the client connection.
      * Log message to logger
      *
      * @return command line or null
      * @throws IOException when unable to read the next line
      */
     public String readClient() throws IOException {
         String line = in.readLine();
         if (line != null) {
             if (line.startsWith("PASS")) {
                 DavGatewayTray.debug(new BundleMessage("LOG_READ_CLIENT_PASS"));
                 // SMTP LOGIN
             } else if (line.startsWith("AUTH LOGIN ")) {
                 DavGatewayTray.debug(new BundleMessage("LOG_READ_CLIENT_AUTH_LOGIN"));
                 // IMAP LOGIN
             } else if (state == State.INITIAL && line.indexOf(' ') >= 0 &&
                     line.substring(line.indexOf(' ') + 1).toUpperCase().startsWith("LOGIN")) {
                 DavGatewayTray.debug(new BundleMessage("LOG_READ_CLIENT_LOGIN"));
             } else if (state == State.PASSWORD) {
                 DavGatewayTray.debug(new BundleMessage("LOG_READ_CLIENT_PASSWORD"));
                 // HTTP Basic Authentication
             } else if (line.startsWith("Authorization:")) {
                 DavGatewayTray.debug(new BundleMessage("LOG_READ_CLIENT_AUTHORIZATION"));
             } else if (line.startsWith("AUTH PLAIN")) {
                 DavGatewayTray.debug(new BundleMessage("LOG_READ_CLIENT_AUTH_PLAIN"));
             } else {
                 DavGatewayTray.debug(new BundleMessage("LOG_READ_CLIENT_LINE", line));
             }
         }
         DavGatewayTray.switchIcon();
         return line;
     }
 
     /**
      * Close client connection, streams, and Exchange session.
      */
     public void close() {
         logConnection("DISCONNECT", "");
         if (in != null) {
             try {
                 in.close();
             } catch (IOException e2) {
                 // ignore
             }
         }
         if (os != null) {
             try {
                 os.close();
             } catch (IOException e2) {
                 // ignore
             }
         }
         try {
             client.close();
         } catch (IOException e2) {
             DavGatewayTray.debug(new BundleMessage("LOG_EXCEPTION_CLOSING_CLIENT_SOCKET"), e2);
         }
     }
 }