/*
 * Copyright © 2010 Codethink Limited
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * 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/>.
 *
 * Author: Ryan Lortie <desrt@desrt.ca>
 */

#include "config.h"

#include "gsimplepermission.h"
#include "gsettingsbackendinternal.h"
#include "giomodule-priv.h"


#define G_TYPE_MEMORY_SETTINGS_BACKEND  (g_memory_settings_backend_get_type())
#define G_MEMORY_SETTINGS_BACKEND(inst) (G_TYPE_CHECK_INSTANCE_CAST ((inst), \
                                         G_TYPE_MEMORY_SETTINGS_BACKEND,     \
                                         GMemorySettingsBackend))

typedef GSettingsBackendClass GMemorySettingsBackendClass;
typedef struct
{
  GSettingsBackend parent_instance;
  GHashTable *table;
} GMemorySettingsBackend;

G_DEFINE_TYPE_WITH_CODE (GMemorySettingsBackend,
                         g_memory_settings_backend,
                         G_TYPE_SETTINGS_BACKEND,
                         _g_io_modules_ensure_extension_points_registered ();
                         g_io_extension_point_implement (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME,
                                                         g_define_type_id, "memory", 10))

static GVariant *
g_memory_settings_backend_read (GSettingsBackend   *backend,
                                const gchar        *key,
                                const GVariantType *expected_type,
                                gboolean            default_value)
{
  GMemorySettingsBackend *memory = G_MEMORY_SETTINGS_BACKEND (backend);
  GVariant *value;

  if (default_value)
    return NULL;

  value = g_hash_table_lookup (memory->table, key);

  if (value != NULL)
    g_variant_ref (value);

  return value;
}

static gboolean
g_memory_settings_backend_write (GSettingsBackend *backend,
                                 const gchar      *key,
                                 GVariant         *value,
                                 gpointer          origin_tag)
{
  GMemorySettingsBackend *memory = G_MEMORY_SETTINGS_BACKEND (backend);
  GVariant *old_value;

  old_value = g_hash_table_lookup (memory->table, key);
  g_variant_ref_sink (value);

  if (old_value == NULL || !g_variant_equal (value, old_value))
    {
      g_hash_table_insert (memory->table, g_strdup (key), value);
      g_settings_backend_changed (backend, key, origin_tag);
    }
  else
    g_variant_unref (value);

  return TRUE;
}

static gboolean
g_memory_settings_backend_write_one (gpointer key,
                                     gpointer value,
                                     gpointer data)
{
  GMemorySettingsBackend *memory = data;

  if (value != NULL)
    g_hash_table_insert (memory->table, g_strdup (key), g_variant_ref (value));
  else
    g_hash_table_remove (memory->table, key);

  return FALSE;
}

static gboolean
g_memory_settings_backend_write_tree (GSettingsBackend *backend,
                                      GTree            *tree,
                                      gpointer          origin_tag)
{
  g_tree_foreach (tree, g_memory_settings_backend_write_one, backend);
  g_settings_backend_changed_tree (backend, tree, origin_tag);

  return TRUE;
}

static void
g_memory_settings_backend_reset (GSettingsBackend *backend,
                                 const gchar      *key,
                                 gpointer          origin_tag)
{
  GMemorySettingsBackend *memory = G_MEMORY_SETTINGS_BACKEND (backend);

  if (g_hash_table_lookup (memory->table, key))
    {
      g_hash_table_remove (memory->table, key);
      g_settings_backend_changed (backend, key, origin_tag);
    }
}

static gboolean
g_memory_settings_backend_get_writable (GSettingsBackend *backend,
                                        const gchar      *name)
{
  return TRUE;
}

static GPermission *
g_memory_settings_backend_get_permission (GSettingsBackend *backend,
                                          const gchar      *path)
{
  return g_simple_permission_new (TRUE);
}

static void
g_memory_settings_backend_finalize (GObject *object)
{
  GMemorySettingsBackend *memory = G_MEMORY_SETTINGS_BACKEND (object);

  g_hash_table_unref (memory->table);

  G_OBJECT_CLASS (g_memory_settings_backend_parent_class)
    ->finalize (object);
}

static void
g_memory_settings_backend_init (GMemorySettingsBackend *memory)
{
  memory->table = g_hash_table_new_full (g_str_hash, g_str_equal, g_free,
                                         (GDestroyNotify) g_variant_unref);
}

static void
g_memory_settings_backend_class_init (GMemorySettingsBackendClass *class)
{
  GSettingsBackendClass *backend_class = G_SETTINGS_BACKEND_CLASS (class);
  GObjectClass *object_class = G_OBJECT_CLASS (class);

  backend_class->read = g_memory_settings_backend_read;
  backend_class->write = g_memory_settings_backend_write;
  backend_class->write_tree = g_memory_settings_backend_write_tree;
  backend_class->reset = g_memory_settings_backend_reset;
  backend_class->get_writable = g_memory_settings_backend_get_writable;
  backend_class->get_permission = g_memory_settings_backend_get_permission;
  object_class->finalize = g_memory_settings_backend_finalize;
}

/**
 * g_memory_settings_backend_new:
 *
 * Creates a memory-backed #GSettingsBackend.
 *
 * This backend allows changes to settings, but does not write them
 * to any backing storage, so the next time you run your application,
 * the memory backend will start out with the default values again.
 *
 * Returns: (transfer full): a newly created #GSettingsBackend
 *
 * Since: 2.28
 */
GSettingsBackend *
g_memory_settings_backend_new (void)
{
  return g_object_new (G_TYPE_MEMORY_SETTINGS_BACKEND, NULL);
}