/*
 * Copyright (C) 2011 Canonical Ltd
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 * Authored by: Rodrigo Moya <rodrigo.moya@canonical.com>
 */

#include <gconf/gconf-client.h>
#include <gio/gio.h>

#include "panel-a11y.h"
#include "panel-util-accessible.h"

static gboolean a11y_initialized = FALSE;

#define INIT_METHOD "gnome_accessibility_module_init"
#define A11Y_GCONF_KEY "/desktop/gnome/interface/accessibility"
#define AT_SPI_SCHEMA "org.a11y.atspi"
#define ATK_BRIDGE_LOCATION_KEY "atk-bridge-location"

static gboolean
has_gsettings_schema (const gchar *schema)
{
  const char * const *list_schemas = NULL;
  gboolean found = FALSE;
  int i = 0;

  /* we need to check if AT_SPI_SCHEMA is present as g_settings_new
     could abort if the schema is not here*/
  list_schemas = g_settings_list_schemas ();
  for (i = 0; list_schemas [i]; i++)
    {
      if (!g_strcmp0 (list_schemas[i], schema))
        {
          found = TRUE;
          break;
        }
    }

  return found;
}

static gboolean
should_enable_a11y (void)
{
  GConfClient *client = NULL;
  gboolean value = FALSE;
  GError *error = NULL;

  client = gconf_client_get_default ();
  value = gconf_client_get_bool (client, A11Y_GCONF_KEY, &error);
  if (error != NULL)
    {
      g_warning ("Error getting gconf variable %s, a11y disabled by default",
                 A11Y_GCONF_KEY);
      g_error_free (error);
    }
  g_object_unref (client);

  return value;
}

static gchar*
get_atk_bridge_path (void)
{
  GSettings *atspi_settings = NULL;
  char *value = NULL;

  if (!has_gsettings_schema (AT_SPI_SCHEMA))
    return NULL;

  atspi_settings = g_settings_new (AT_SPI_SCHEMA);
  value = g_settings_get_string (atspi_settings, ATK_BRIDGE_LOCATION_KEY);

  g_object_unref (atspi_settings);

  return value;
}

static gboolean
a11y_invoke_module (const char *module_path)
{
  GModule    *handle;
  void      (*invoke_fn) (void);

  if (!module_path)
    {
      g_warning ("Accessibility: invalid module path (NULL)");

      return FALSE;
    }

  if (!(handle = g_module_open (module_path, (GModuleFlags)0)))
    {
      g_warning ("Accessibility: failed to load module '%s': '%s'",
                 module_path, g_module_error ());

      return FALSE;
    }

  if (!g_module_symbol (handle, INIT_METHOD, (gpointer *)&invoke_fn))
    {
      g_warning ("Accessibility: error library '%s' does not include "
                 "method '%s' required for accessibility support",
                 module_path, INIT_METHOD);
      g_module_close (handle);

      return FALSE;
    }

  invoke_fn ();

  return TRUE;
}

void
panel_a11y_init (void)
{
  AtkObject *root;
  gchar *bridge_path = NULL;

  if (a11y_initialized)
    return;

  /* Restore environment to load AT bridge */
  g_unsetenv ("NO_AT_BRIDGE");
  g_unsetenv ("NO_GAIL");

  if (!should_enable_a11y ())
    return;

  /* Load PanelUtilAccessible class */
  g_type_class_unref (g_type_class_ref (PANEL_TYPE_UTIL_ACCESSIBLE));

  bridge_path = get_atk_bridge_path ();
  if (a11y_invoke_module (bridge_path))
    {
      g_debug ("Unity accessibility started, using bridge on %s", bridge_path);
    }

  g_free (bridge_path);

  /* There might be cases when we start signalling about change of geometries but the
     accessible objects are not yet created, so to avoid that, instantiate here the
     A11Y root object, which will create them all */
  root = atk_get_root ();

  a11y_initialized = TRUE;
}