/* Copyright (C) 2014 The glibmm 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/>.
 */

#include <glibmm/binding.h>
#include <glib.h>

namespace
{
struct BindingTransformSlots
{
  BindingTransformSlots(const Glib::Binding::SlotTransform& transform_to,
    const Glib::Binding::SlotTransform& transform_from)
  : from_source_to_target(transform_to), from_target_to_source(transform_from)
  {
  }

  Glib::Binding::SlotTransform from_source_to_target;
  Glib::Binding::SlotTransform from_target_to_source;
};

gboolean
Binding_transform_callback_common(
  const GValue* from_value, GValue* to_value, Glib::Binding::SlotTransform& the_slot)
{
  bool result = false;
  try
  {
    result = the_slot(from_value, to_value);
  }
  catch (...)
  {
    Glib::exception_handlers_invoke();
  }
  return result;
}

gboolean
Binding_transform_to_callback(
  GBinding*, const GValue* from_value, GValue* to_value, gpointer user_data)
{
  Glib::Binding::SlotTransform& the_slot =
    static_cast<BindingTransformSlots*>(user_data)->from_source_to_target;

  return Binding_transform_callback_common(from_value, to_value, the_slot);
}

gboolean
Binding_transform_from_callback(
  GBinding*, const GValue* from_value, GValue* to_value, gpointer user_data)
{
  Glib::Binding::SlotTransform& the_slot =
    static_cast<BindingTransformSlots*>(user_data)->from_target_to_source;

  return Binding_transform_callback_common(from_value, to_value, the_slot);
}

void
Binding_transform_callback_destroy(gpointer user_data)
{
  delete static_cast<BindingTransformSlots*>(user_data);
}

} // anonymous namespace

namespace Glib
{
// static
Glib::RefPtr<Binding>
Binding::bind_property_value(const PropertyProxy_Base& source_property,
  const PropertyProxy_Base& target_property, BindingFlags flags, const SlotTransform& transform_to,
  const SlotTransform& transform_from)
{
  GBinding* binding = nullptr;
  if (transform_to.empty() && transform_from.empty())
  {
    // No user-supplied transformations.
    binding =
      g_object_bind_property(source_property.get_object()->gobj(), source_property.get_name(),
        target_property.get_object()->gobj(), target_property.get_name(), (GBindingFlags)flags);
  }
  else
  {
    // Create copies of the slots. A pointer to this will be passed
    // through the callback's data parameter. It will be deleted
    // when Binding_transform_callback_destroy() is called.
    BindingTransformSlots* slots_copy = new BindingTransformSlots(transform_to, transform_from);

    binding = g_object_bind_property_full(source_property.get_object()->gobj(),
      source_property.get_name(), target_property.get_object()->gobj(), target_property.get_name(),
      (GBindingFlags)flags, transform_to.empty() ? nullptr : &Binding_transform_to_callback,
      transform_from.empty() ? nullptr : &Binding_transform_from_callback, slots_copy,
      &Binding_transform_callback_destroy);
  }

  if (!binding)
    return Glib::RefPtr<Binding>();

  // Take an extra ref. GBinding uses one ref itself, and drops it if
  // either the source object or the target object is finalized.
  // The GBinding object must not be destroyed while there are RefPtrs around.
  g_object_ref(binding);
  return Glib::RefPtr<Binding>(new Binding(binding));
}

void
Binding::unbind()
{
  // Call g_binding_unbind() only once. It always calls g_object_unref().
  if (g_binding_get_source(gobj()))
    g_binding_unbind(gobj());
}

// Override unreference() from ObjectBase.
//
// Why is this necessary? Because GBinding is an unusual kind of GObject.
// It calls g_object_unref() itself, if either the source object or the
// target object is finalized, almost like g_binding_unbind().
// But the GBinding object shall be destroyed when and only when the last
// reference from a Glib::RefPtr is dropped.
void
Binding::unreference() const
{
  GBinding* const binding = const_cast<GBinding*>(gobj());

  // If the last Glib::RefPtr is being deleted, and the binding has not been unbound,
  // then drop the extra reference that was added by bind_property_value().
  if (gobject_->ref_count == 2 && g_binding_get_source(binding))
    g_object_unref(binding);

  Object::unreference();
}

} // namespace Glib