/**
   * Sends the <tt>message</tt> to the destination indicated by the <tt>to</tt> contact.
   *
   * @param to the <tt>Contact</tt> to send <tt>message</tt> to
   * @param message the <tt>Message</tt> to send.
   * @throws java.lang.IllegalStateException if the underlying stack is not registered and
   *     initialized.
   * @throws java.lang.IllegalArgumentException if <tt>to</tt> is not an instance of ContactImpl.
   */
  public void sendInstantMessage(Contact to, Message message)
      throws IllegalStateException, IllegalArgumentException {
    if (!(to instanceof ContactSipImpl))
      throw new IllegalArgumentException("The specified contact is not a Sip contact." + to);

    assertConnected();

    // offline message
    if (to.getPresenceStatus().equals(sipStatusEnum.getStatus(SipStatusEnum.OFFLINE))
        && !offlineMessageSupported) {
      if (logger.isDebugEnabled()) logger.debug("trying to send a message to an offline contact");
      fireMessageDeliveryFailed(
          message, to, MessageDeliveryFailedEvent.OFFLINE_MESSAGES_NOT_SUPPORTED);
      return;
    }

    // create the message
    Request mes;
    try {
      mes = createMessageRequest(to, message);
    } catch (OperationFailedException ex) {
      logger.error("Failed to create the message.", ex);

      fireMessageDeliveryFailed(message, to, MessageDeliveryFailedEvent.INTERNAL_ERROR);
      return;
    }

    try {
      sendMessageRequest(mes, to, message);
    } catch (TransactionUnavailableException ex) {
      logger.error(
          "Failed to create messageTransaction.\n"
              + "This is most probably a network connection error.",
          ex);

      fireMessageDeliveryFailed(message, to, MessageDeliveryFailedEvent.NETWORK_FAILURE);
      return;
    } catch (SipException ex) {
      logger.error("Failed to send the message.", ex);

      fireMessageDeliveryFailed(message, to, MessageDeliveryFailedEvent.INTERNAL_ERROR);
      return;
    }
  }
  /**
   * Construct a <tt>Request</tt> represent a new message.
   *
   * @param to the <tt>Contact</tt> to send <tt>message</tt> to
   * @param message the <tt>Message</tt> to send.
   * @return a Message Request destined to the contact
   * @throws OperationFailedException if an error occurred during the creation of the request
   */
  Request createMessageRequest(Contact to, Message message) throws OperationFailedException {
    Address toAddress = null;
    try {
      toAddress = sipProvider.parseAddressString(to.getAddress());
    } catch (ParseException exc) {
      // Shouldn't happen
      logger.error("An unexpected error occurred while" + "constructing the address", exc);
      throw new OperationFailedException(
          "An unexpected error occurred while" + "constructing the address",
          OperationFailedException.INTERNAL_ERROR,
          exc);
    }

    // Call ID
    CallIdHeader callIdHeader = this.sipProvider.getDefaultJainSipProvider().getNewCallId();

    // CSeq
    CSeqHeader cSeqHeader = null;

    try {
      // protect seqN
      synchronized (this) {
        cSeqHeader = this.sipProvider.getHeaderFactory().createCSeqHeader(seqN++, Request.MESSAGE);
      }
    } catch (InvalidArgumentException ex) {
      // Shouldn't happen
      logger.error("An unexpected error occurred while" + "constructing the CSeqHeadder", ex);
      throw new OperationFailedException(
          "An unexpected error occurred while" + "constructing the CSeqHeadder",
          OperationFailedException.INTERNAL_ERROR,
          ex);
    } catch (ParseException exc) {
      // shouldn't happen
      logger.error("An unexpected error occurred while" + "constructing the CSeqHeadder", exc);
      throw new OperationFailedException(
          "An unexpected error occurred while" + "constructing the CSeqHeadder",
          OperationFailedException.INTERNAL_ERROR,
          exc);
    }

    // FromHeader and ToHeader
    String localTag = SipMessageFactory.generateLocalTag();
    FromHeader fromHeader = null;
    ToHeader toHeader = null;
    try {
      // FromHeader
      fromHeader =
          this.sipProvider
              .getHeaderFactory()
              .createFromHeader(sipProvider.getOurSipAddress(toAddress), localTag);

      // ToHeader
      toHeader = this.sipProvider.getHeaderFactory().createToHeader(toAddress, null);
    } catch (ParseException ex) {
      // these two should never happen.
      logger.error(
          "An unexpected error occurred while" + "constructing the FromHeader or ToHeader", ex);
      throw new OperationFailedException(
          "An unexpected error occurred while" + "constructing the FromHeader or ToHeader",
          OperationFailedException.INTERNAL_ERROR,
          ex);
    }

    // ViaHeaders
    ArrayList<ViaHeader> viaHeaders = this.sipProvider.getLocalViaHeaders(toAddress);

    // MaxForwards
    MaxForwardsHeader maxForwards = this.sipProvider.getMaxForwardsHeader();

    // Content params
    ContentTypeHeader contTypeHeader;
    ContentLengthHeader contLengthHeader;
    try {
      contTypeHeader =
          this.sipProvider
              .getHeaderFactory()
              .createContentTypeHeader(getType(message), getSubType(message));

      if (!DEFAULT_MIME_ENCODING.equalsIgnoreCase(message.getEncoding()))
        contTypeHeader.setParameter("charset", message.getEncoding());

      contLengthHeader =
          this.sipProvider.getHeaderFactory().createContentLengthHeader(message.getSize());
    } catch (ParseException ex) {
      // these two should never happen.
      logger.error("An unexpected error occurred while" + "constructing the content headers", ex);
      throw new OperationFailedException(
          "An unexpected error occurred while" + "constructing the content headers",
          OperationFailedException.INTERNAL_ERROR,
          ex);
    } catch (InvalidArgumentException exc) {
      // these two should never happen.
      logger.error(
          "An unexpected error occurred while" + "constructing the content length header", exc);
      throw new OperationFailedException(
          "An unexpected error occurred while" + "constructing the content length header",
          OperationFailedException.INTERNAL_ERROR,
          exc);
    }

    Request req;
    try {
      req =
          this.sipProvider
              .getMessageFactory()
              .createRequest(
                  toHeader.getAddress().getURI(),
                  Request.MESSAGE,
                  callIdHeader,
                  cSeqHeader,
                  fromHeader,
                  toHeader,
                  viaHeaders,
                  maxForwards,
                  contTypeHeader,
                  message.getRawData());
    } catch (ParseException ex) {
      // shouldn't happen
      logger.error("Failed to create message Request!", ex);
      throw new OperationFailedException(
          "Failed to create message Request!", OperationFailedException.INTERNAL_ERROR, ex);
    }

    req.addHeader(contLengthHeader);

    return req;
  }