/* Copyright (C) 2007 The giomm Development Team
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

_CONFIGINCLUDE(giommconfig.h)

#include <glibmm/interface.h>
#include <glibmm/object.h>

_DEFS(giomm,gio)
_PINCLUDE(glibmm/private/interface_p.h)

#ifndef DOXYGEN_SHOULD_SKIP_THIS
typedef struct _GAsyncResultIface GAsyncResultIface;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

namespace Gio
{

class GIOMM_API AsyncResult;

/** A function that will be called when an asynchronous operation within GIO has been completed.
 * @param result The asynchronous function's results.
 *
 * For instance,
 * @code
 * void on_async_ready(Glib::RefPtr<Gio::AsyncResult>& result);
 * @endcode
 *
 * @newin{2,16}
 * @relates Gio::AsyncResult
 */
using SlotAsyncReady = sigc::slot<void(Glib::RefPtr<AsyncResult>&)>;

/** Provides a base class for implementing asynchronous function results.
 *
 * Asynchronous operations are broken up into two separate operations which are chained together by a SlotAsyncReady.
 * To begin an asynchronous operation, provide a SlotAsyncReady to the asynchronous function. This callback will be triggered
 * when the operation has completed, and will be passed an %AsyncResult instance
 * (an instance of a class that implements the %AsyncResult interface)
 * filled with the details of the operation's success or failure,
 * the object the asynchronous function was started for and any error codes returned. The asynchronous callback function is then
 * expected to call the corresponding "_finish()" function of the object the async function was called for, with the %AsyncResult instance.
 *
 * The purpose of the "_finish()" function is to take the generic result of type %AsyncResult and return the specific result that the operation
 * in question yields (e.g. a FileEnumerator for an "enumerate children" operation). If the result or error status of the operation is not needed,
 * there is no need to call the "_finish()" function and GIO will take care of cleaning up the result and error information after the
 * SlotAsyncReady returns. You may also store the %AsyncResult and call "_finish()" later.
 * However, the "_finish()" function may be called at most once.
 *
 * Example of a typical asynchronous operation flow:
 * @code
 * class Theoretical : public Glib::Object
 * {
 * public:
 *   Glib::RefPtr<Theoretical> create();
 *
 *   void frobnitz_async(const Gio::SlotAsyncReady& slot);
 *   Glib::ustring frobnitz_finish(const Glib::RefPtr<Gio::AsyncResult>& result);
 * // ...
 * };
 *
 * // ...
 *
 * namespace
 * {
 * Glib::RefPtr<Theoretical> theoretical;
 *
 * void on_frobnitz_ready(Glib::RefPtr<Gio::AsyncResult>& result)
 * {
 *   try
 *   {
 *     Glib::ustring s = theoretical->frobnitz_finish(result);
 *     std::cout << s << std::endl;
 *   }
 *   catch (const Glib::Error& err)
 *   {
 *     std::cerr << err.what() << std::endl;
 *   }
 *   // ...
 * }
 * } // anonymous namespace
 *
 * int main(int argc, void* argv[])
 * {
 *   // ...
 *   theoretical = Theoretical::create();
 *   theoretical->frobnitz_async(sigc::ptr_fun(&on_frobnitz_ready));
 *   // ...
 * }
 * @endcode
 *
 * The async function could also take an optional Gio::Cancellable object, allowing the calling function to cancel the asynchronous operation.
 *
 * The callback for an asynchronous operation is called only once, and is always called, even in the case of a cancelled operation.
 * On cancellation the "_finish()" function will throw a Gio::Error exception with a <tt>Gio::Error::CANCELLED</tt> error code.
 *
 * @newin{2,16}
 */
class GIOMM_API AsyncResult : public Glib::Interface
{
  _CLASS_INTERFACE(AsyncResult, GAsyncResult, G_ASYNC_RESULT, GAsyncResultIface, , , GIOMM_API)

public:
  _IGNORE(g_async_result_get_user_data)
  _IGNORE(g_async_result_get_source_object)

  //Note that this returns a reference, unlike most GTK+ get_*() functions,
  //so we don't need to use refreturn.
  Glib::RefPtr<Glib::ObjectBase> get_source_object_base();
  Glib::RefPtr<const Glib::ObjectBase> get_source_object_base() const;

  _IGNORE(g_async_result_legacy_propagate_error)dnl// Shall not be used in new code

  _WRAP_METHOD(bool is_tagged(gpointer source_tag) const, g_async_result_is_tagged)

protected:
  // The compiler cannot find an unwrap() for ObjectBase, because
  // ObjectBase::BaseObjectType is not declared.
  //#m4 _CONVERSION(`Glib::RefPtr<Glib::ObjectBase>',`GObject*',__CONVERT_REFPTR_TO_P)
#m4 _CONVERSION(`Glib::RefPtr<Glib::ObjectBase>',`GObject*',`unwrap_objectbase_custom($3)')
  _WRAP_VFUNC(Glib::RefPtr<Glib::ObjectBase> get_source_object(), "get_source_object")
  _WRAP_VFUNC(bool is_tagged(gpointer source_tag), "is_tagged")
};

} // namespace Gio