/*
 * Example low-level D-Bus code.
 * Written by Matthew Johnson <address@hidden>
 *
 * This code has been released into the Public Domain.
 * You may do whatever you like with it.
 */
#include <dbus/dbus.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

class dbus_server
{
public:
  // Constructor/destructor
  dbus_server ();
  ~dbus_server ();
  
  // Interaction functions
  void handle_requests (std::string &retval, bool &has_command);

private:
  // Data
  DBusMessage *msg;
  DBusMessageIter args;
  DBusConnection *conn;
  DBusError err;
  bool is_connected;
};

dbus_server::dbus_server ()
  : is_connected (false)
{
  // initialise the errors
  dbus_error_init (&err);
   
  // connect to the bus and check for errors
  conn = dbus_bus_get (DBUS_BUS_SESSION, &err);
  if (dbus_error_is_set (&err) || conn == NULL)
    return;

  // request our name on the bus and check for errors
  const int ret = dbus_bus_request_name (conn, "org.octave.some_instance", 
                                         DBUS_NAME_FLAG_REPLACE_EXISTING , &err);
  if (dbus_error_is_set (&err) || ret != DBUS_REQUEST_NAME_REPLY_PRIMARY_OWNER)
    return;

  // add a rule for which messages we want to see
  dbus_bus_add_match (conn, "type='signal',interface='org.octave.interface'", &err);
  dbus_connection_flush (conn);
  if (dbus_error_is_set (&err))
    return;
  
  // We've connected successfully to the bus
  is_connected = true;
}

dbus_server::~dbus_server ()
{
  dbus_error_free (&err);
}

void dbus_server::handle_requests (std::string &retval, bool &has_command)
{
  char *code;
  has_command = false;
  if (!is_connected)
    return;

  // non blocking read of the next available message
  dbus_connection_read_write (conn, 0);
  msg = dbus_connection_pop_message (conn);

  // loop again if we haven't read a message
  if (msg == NULL)
    return;

  // check if the message is a signal from the correct interface and with the correct name
  if (dbus_message_is_signal (msg, "org.octave.interface", "evaluate")
  &&  dbus_message_iter_init (msg, &args)
  &&  dbus_message_iter_get_arg_type (&args) == DBUS_TYPE_STRING)
    {
      // read the parameters
      dbus_message_iter_get_basic (&args, &code);
      retval = code;
      has_command = true;
    }

  // free the message
  dbus_message_unref (msg);
}