/**
 * Copyright © 2010 Canonical Limited
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the licence, or (at
 * your option) any later version.
 *
 * 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/>.
 *
 * Author: Ryan Lortie <desrt@desrt.ca>
 **/

#include "dconf-dbus-1.h"

#include <dconf-engine.h>

#include <string.h>

typedef struct _Outstanding Outstanding;

struct _DConfDBusClient
{
  DBusConnection *session_bus;
  DBusConnection *system_bus;
  GSList *watches;
  gint ref_count;

  Outstanding *outstanding;
  gchar *anti_expose_tag;

  DConfEngine *engine;
};

static void
dconf_dbus_client_add_value_to_iter (DBusMessageIter *iter,
                                     GVariant        *value)
{
  GVariantClass class;

  class = g_variant_classify (value);

  switch (class)
    {
    case G_VARIANT_CLASS_BOOLEAN:
      {
        dbus_bool_t boolean;

        boolean = g_variant_get_boolean (value);
        dbus_message_iter_append_basic (iter, 'b', &boolean);
      }
      break;

    case G_VARIANT_CLASS_BYTE:
    case G_VARIANT_CLASS_INT16:
    case G_VARIANT_CLASS_UINT16:
    case G_VARIANT_CLASS_INT32:
    case G_VARIANT_CLASS_UINT32:
    case G_VARIANT_CLASS_INT64:
    case G_VARIANT_CLASS_UINT64:
    case G_VARIANT_CLASS_DOUBLE:
      dbus_message_iter_append_basic (iter, class,
                                      g_variant_get_data (value));
      break;

    case G_VARIANT_CLASS_STRING:
    case G_VARIANT_CLASS_OBJECT_PATH:
    case G_VARIANT_CLASS_SIGNATURE:
      {
        const gchar *str;

        str = g_variant_get_string (value, NULL);
        dbus_message_iter_append_basic (iter, class, &str);
      }
      break;

    case G_VARIANT_CLASS_ARRAY:
      {
        const gchar *contained;
        DBusMessageIter sub;
        gint i, n;

        contained = g_variant_get_type_string (value) + 1;
        n = g_variant_n_children (value);
        dbus_message_iter_open_container (iter, 'a', contained, &sub);
        for (i = 0; i < n; i++)
          {
            GVariant *child;

            child = g_variant_get_child_value (value, i);
            dconf_dbus_client_add_value_to_iter (&sub, child);
            g_variant_unref (child);
          }
          
        dbus_message_iter_close_container (iter, &sub);
      }
      break;

    case G_VARIANT_CLASS_TUPLE:
      {
        DBusMessageIter sub;
        gint i, n;

        n = g_variant_n_children (value);
        dbus_message_iter_open_container (iter, 'r', NULL, &sub);
        for (i = 0; i < n; i++)
          {
            GVariant *child;

            child = g_variant_get_child_value (value, i);
            dconf_dbus_client_add_value_to_iter (&sub, child);
            g_variant_unref (child);
          }
          
        dbus_message_iter_close_container (iter, &sub);
      }
      break;

    case G_VARIANT_CLASS_DICT_ENTRY:
      {
        DBusMessageIter sub;
        gint i;

        dbus_message_iter_open_container (iter, 'e', NULL, &sub);
        for (i = 0; i < 2; i++)
          {
            GVariant *child;

            child = g_variant_get_child_value (value, i);
            dconf_dbus_client_add_value_to_iter (&sub, child);
            g_variant_unref (child);
          }
          
        dbus_message_iter_close_container (iter, &sub);
      }
      break;

    case G_VARIANT_CLASS_VARIANT:
      {
        DBusMessageIter sub;
        GVariant *child;

        child = g_variant_get_variant (value);
        dbus_message_iter_open_container (iter, 'v',
                                          g_variant_get_type_string (child),
                                          &sub);
        dconf_dbus_client_add_value_to_iter (&sub, child);
        dbus_message_iter_close_container (iter, &sub);
        g_variant_unref (child);
      }
      break;

    default:
      g_assert_not_reached ();
    }
}

static void
dconf_dbus_client_send (DConfDBusClient               *dcdbc,
                        DConfEngineMessage            *dcem,
                        DBusPendingCallNotifyFunction  callback,
                        gpointer                       user_data)
{
  DBusConnection *connection;
  gint i;

  for (i = 0; i < dcem->n_messages; i++)
    {
      switch (dcem->bus_types[i])
        {
        case 'e':
          connection = dcdbc->session_bus;
          break;

        case 'y':
          connection = dcdbc->system_bus;
          break;

        default:
          g_assert_not_reached ();
        }

      if (connection == NULL && callback != NULL)
        callback (NULL, user_data);

      if (connection != NULL)
        {
          DBusPendingCall *pending;
          DBusMessageIter diter;
          DBusMessage *message;
          GVariantIter giter;
          GVariant *child;

          message = dbus_message_new_method_call (dcem->bus_name,
                                                  dcem->object_path,
                                                  dcem->interface_name,
                                                  dcem->method_name);

          dbus_message_iter_init_append (message, &diter);
          g_variant_iter_init (&giter, dcem->parameters[i]);

          while ((child = g_variant_iter_next_value (&giter)))
            {
              dconf_dbus_client_add_value_to_iter (&diter, child);
              g_variant_unref (child);
            }

          dbus_connection_send_with_reply (connection, message,
                                           &pending, 120000);
          dbus_pending_call_set_notify (pending, callback, user_data, NULL);
          dbus_message_unref (message);
        }
    }
}

static GVariant *
dconf_dbus_client_send_finish (DBusPendingCall *pending)
{
  DBusMessage *message;
  GVariant *result;

  if (pending == NULL)
    return NULL;

  message = dbus_pending_call_steal_reply (pending);
  dbus_pending_call_unref (pending);

  /* We only have to deal with two types of replies: () and (s) */
  if (dbus_message_has_signature (message, "s"))
    {
      dbus_message_get_args (message, NULL,
                             DBUS_TYPE_STRING, &result,
                             DBUS_TYPE_INVALID);
      result = g_variant_new ("(s)", result);
    }
  else
    result = g_variant_new ("()");

  dbus_message_unref (message);

  return result;
}

struct _Outstanding
{
  Outstanding *next;

  DConfDBusClient *dcdbc;
  DConfEngineMessage    dcem;

  gchar    *set_key;
  GVariant *set_value;
  GTree    *tree;
};

static void
dconf_dbus_client_outstanding_returned (DBusPendingCall *pending,
                                        gpointer         user_data)
{
  Outstanding *outstanding = user_data;
  DConfDBusClient *dcdbc;
  GVariant *reply;

  dcdbc = outstanding->dcdbc;

  /* One way or another we no longer need this hooked into the list.
   */
  {
    Outstanding **tmp;

    for (tmp = &dcdbc->outstanding; tmp; tmp = &(*tmp)->next)
      if (*tmp == outstanding)
        {
          *tmp = outstanding->next;
          break;
        }
  }

  reply = dconf_dbus_client_send_finish (pending);

  if (reply)
    {
      /* Success.
       *
       * We want to ensure that we don't emit an extra change
       * notification signal when we see the signal that the service is
       * about to send, so store the tag so we know to ignore it when
       * the signal comes.
       *
       * No thread safety issue here since this variable is only
       * accessed from the worker thread.
       */
      g_free (dcdbc->anti_expose_tag);

      if (g_variant_is_of_type (reply, G_VARIANT_TYPE ("(s)")))
        g_variant_get_child (reply, 0, "s", dcdbc->anti_expose_tag);

      g_variant_unref (reply);
    }
  else
    {
      /* An error of some kind.
       *
       * We already removed the outstanding entry from the list, so the
       * unmodified database is now visible to the client.  Change
       * notify so that they see it.
       */
      if (outstanding->set_key)
          /* XXX emit */;
      else
          /* XXX emit */;
    }

  dconf_engine_message_destroy (&outstanding->dcem);
  dconf_dbus_client_unref (outstanding->dcdbc);
  g_free (outstanding->set_key);

  if (outstanding->set_value)
    g_variant_unref (outstanding->set_value);

  if (outstanding->tree)
    g_tree_unref (outstanding->tree);

  g_slice_free (Outstanding, outstanding);
}

static void
dconf_dbus_client_queue (DConfDBusClient *dcdbc,
                         DConfEngineMessage   *dcem,
                         const gchar          *set_key,
                         GVariant             *set_value,
                         GTree                *tree)
{
  Outstanding *outstanding;

  outstanding = g_slice_new (Outstanding);
  outstanding->dcdbc = dconf_dbus_client_ref (dcdbc);
  outstanding->dcem = *dcem;

  outstanding->set_key = g_strdup (set_key);
  outstanding->set_value = set_value ? g_variant_ref_sink (set_value) : NULL;
  outstanding->tree = tree ? g_tree_ref (tree) : NULL;

  outstanding->next = dcdbc->outstanding;
  dcdbc->outstanding = outstanding;

  dconf_dbus_client_send (outstanding->dcdbc,
                               &outstanding->dcem,
                               dconf_dbus_client_outstanding_returned,
                               outstanding);
}

static gboolean
dconf_dbus_client_scan_outstanding_tree (GTree       *tree,
                                         const gchar *key,
                                         gsize        key_length,
                                         gpointer    *value)
{
  gchar *mykey;

  mykey = g_alloca (key_length + 1);
  memcpy (mykey, key, key_length + 1);

  while (!g_tree_lookup_extended (tree, mykey, NULL, value) &&
         --key_length)
    {
      while (mykey[key_length - 1] != '/')
        key_length--;

      mykey[key_length] = '\0';
    }

  return key_length != 0;
}

static gboolean
dconf_dbus_client_scan_outstanding (DConfDBusClient  *dcdbc,
                                    const gchar      *key,
                                    GVariant        **value)
{
  gboolean found = FALSE;
  Outstanding *node;
  gsize length;

  length = strlen (key);

  if G_LIKELY (dcdbc->outstanding == NULL)
    return FALSE;

  for (node = dcdbc->outstanding; node; node = node->next)
    {
      if (node->set_key)
        {
          if (strcmp (key, node->set_key) == 0)
            {
              if (node->set_value != NULL)
                *value = g_variant_ref (node->set_value);
              else
                *value = NULL;

              found = TRUE;
              break;
            }
        }

      else
        {
          gpointer result;

          if (dconf_dbus_client_scan_outstanding_tree (node->tree, key,
                                                            length, &result))
            {
              if (result)
                *value = g_variant_ref (result);
              else
                *value = NULL;

              found = TRUE;
              break;
            }
        }
    }

  return found;
}

/* Watches are reference counted because they can be held both by the
 * list of watches and by the pending watch registration.  In the normal
 * case, the registration completes before the watch is unsubscribed
 * from but it might be the case that the watch is unsubscribed from
 * before the AddMatch completes.  For that reason, either thing could
 * be responsible for freeing the watch structure; we solve that
 * ambiguity using a reference count.
 *
 * We just initially set it to 2, since these are the only two users.
 * That way we can skip having the ref() function.
 */
typedef struct
{
  DConfDBusClient *dcdbc;
  gchar           *name;
  DConfDBusNotify  notify;
  gpointer         user_data;
  guint64          initial_state;
  gint             ref_count;
} Watch;



static void
dconf_dbus_emit_change (DConfDBusClient *dcdbc,
                        const gchar     *key)
{
  GSList *iter;

  for (iter = dcdbc->watches; iter; iter = iter->next)
    {
      Watch *watch = iter->data;

      if (g_str_has_prefix (key, watch->name))
        watch->notify (dcdbc, key, watch->user_data);
    }
}

GVariant *
dconf_dbus_client_read (DConfDBusClient *dcdbc,
                        const gchar     *key)
{
  GVariant *value;

  if (dconf_dbus_client_scan_outstanding (dcdbc, key, &value))
    return value;

  return dconf_engine_read (dcdbc->engine, key);
}

gboolean
dconf_dbus_client_write (DConfDBusClient *dcdbc,
                         const gchar     *key,
                         GVariant        *value)
{
  DConfEngineMessage dcem;

  if (!dconf_engine_write (dcdbc->engine, key, value, &dcem, NULL))
    return FALSE;

  dconf_dbus_client_queue (dcdbc, &dcem, key, value, NULL);
  dconf_dbus_emit_change (dcdbc, key);

  return TRUE;
}

static Watch *
watch_new (DConfDBusClient *dcdbc,
           const gchar     *name,
           DConfDBusNotify  notify,
           gpointer         user_data)
{
  Watch *watch;

  watch = g_slice_new (Watch);
  watch->dcdbc = dconf_dbus_client_ref (dcdbc);
  watch->user_data = user_data;
  watch->name = g_strdup (name);
  watch->notify = notify;

  watch->initial_state = dconf_engine_get_state (dcdbc->engine);
  watch->ref_count = 2;

  dcdbc->watches = g_slist_prepend (dcdbc->watches, watch);

  return watch;
}

static void
watch_unref (Watch *watch)
{
  if (--watch->ref_count == 0)
    {
      dconf_dbus_client_unref (watch->dcdbc);
      g_free (watch->name);
      g_slice_free (Watch, watch);
    }
}

static void
add_match_done (DBusPendingCall *pending,
                gpointer         user_data)
{
  Watch *watch = user_data;
  GError *error = NULL;
  GVariant *reply;

  reply = dconf_dbus_client_send_finish (pending);

  if (reply == NULL)
    {
      /* This is extremely unlikely to happen and it happens
       * asynchronous to the user's call.  Since the user doesn't know
       * that it happened, we pretend that it didn't (ie: we leave the
       * watch structure in the list).
       */

      g_critical ("DBus AddMatch for dconf path '%s': %s",
                  watch->name, error->message);
      g_error_free (error);
      watch_unref (watch);

      return;
    }

  else
    g_variant_unref (reply); /* it is just an empty tuple */

  /* In the normal case we're done.
   *
   * There is a fleeting chance, however, that the database has changed
   * in the meantime.  In that case we can only assume that the subject
   * of this watch changed in that time period and emit a signal to that
   * effect.
   */
  if (dconf_engine_get_state (watch->dcdbc->engine) != watch->initial_state)
    watch->notify (watch->dcdbc, watch->name, watch->user_data);

  watch_unref (watch);
}

void
dconf_dbus_client_subscribe (DConfDBusClient *dcdbc,
                             const gchar     *name,
                             DConfDBusNotify  notify,
                             gpointer         user_data)
{
  DConfEngineMessage dcem;
  Watch *watch;
 
  watch = watch_new (dcdbc, name, notify, user_data);
  dconf_engine_watch (dcdbc->engine, name, &dcem);
  dconf_dbus_client_send (dcdbc, &dcem, add_match_done, watch);
  dconf_engine_message_destroy (&dcem);
}

void
dconf_dbus_client_unsubscribe (DConfDBusClient *dcdbc,
                               DConfDBusNotify  notify,
                               gpointer         user_data)
{
  DConfEngineMessage dcem;
  GSList **ptr;

  for (ptr = &dcdbc->watches; *ptr; ptr = &(*ptr)->next)
    {
      Watch *watch = (*ptr)->data;

      if (watch->notify == notify && watch->user_data == user_data)
        {
          *ptr = g_slist_remove (*ptr, *ptr);

          dconf_engine_unwatch (dcdbc->engine, watch->name, &dcem);
          dconf_dbus_client_send (dcdbc, &dcem, NULL, NULL);
          dconf_engine_message_destroy (&dcem);
          watch_unref (watch);

          return;
        }
    }

  g_warning ("No matching watch found to unsubscribe");
}

gboolean
dconf_dbus_client_has_pending (DConfDBusClient *dcdbc)
{
  return dcdbc->outstanding != NULL;
}

static GVariant *
dconf_dbus_client_service_func (DConfEngineMessage *dcem)
{
  g_assert_not_reached ();
}

static DBusHandlerResult
dconf_dbus_client_filter (DBusConnection *connection,
                          DBusMessage    *message,
                          void           *user_data)
{
  DConfDBusClient *dcdbc = user_data;

  if (dbus_message_is_signal (message, "ca.desrt.dconf.Writer", "Notify") &&
      dbus_message_has_signature (message, "sass"))
    {
      DBusMessageIter iter, sub;
      const gchar *path, *tag;

      dbus_message_iter_init (message, &iter);
      dbus_message_iter_get_basic (&iter, &path);
      dbus_message_iter_next (&iter);
      dbus_message_iter_recurse (&iter, &sub);
      dbus_message_iter_next (&iter);
      dbus_message_iter_get_basic (&iter, &tag);
      dbus_message_iter_next (&iter);

      /* Only emit the event if it hasn't been anti-exposed */
      if (dcdbc->anti_expose_tag == NULL ||
          strcmp (tag, dcdbc->anti_expose_tag) != 0)
        {
          /* Empty list means that only one key changed */
          if (!dbus_message_iter_get_arg_type (&sub))
            dconf_dbus_emit_change (dcdbc, path);

          while (dbus_message_iter_get_arg_type (&sub) == 's')
            {
              const gchar *item;
              gchar *full;

              dbus_message_iter_get_basic (&iter, &item);
              full = g_strconcat (path, item, NULL);
              dconf_dbus_emit_change (dcdbc, full);
              g_free (full);

              dbus_message_iter_next (&sub);
            }
        }
    }

  return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
}

DConfDBusClient *
dconf_dbus_client_new (const gchar    *profile,
                       DBusConnection *session,
                       DBusConnection *system)
{
  DConfDBusClient *dcdbc;

  if (session == NULL)
    session = dbus_bus_get (DBUS_BUS_SESSION, NULL);

  if (system == NULL)
    system = dbus_bus_get (DBUS_BUS_SYSTEM, NULL);

  dconf_engine_set_service_func (dconf_dbus_client_service_func);

  dcdbc = g_slice_new (DConfDBusClient);
  dcdbc->engine = dconf_engine_new (profile);
  dcdbc->system_bus = dbus_connection_ref (system);
  dcdbc->session_bus = dbus_connection_ref (session);
  dcdbc->anti_expose_tag = NULL;
  dcdbc->outstanding = NULL;
  dcdbc->watches = NULL;
  dcdbc->ref_count = 1;

  dbus_connection_add_filter (system, dconf_dbus_client_filter, dcdbc, NULL);
  dbus_connection_add_filter (session, dconf_dbus_client_filter, dcdbc, NULL);

  return dcdbc;
}

void
dconf_dbus_client_unref (DConfDBusClient *dcdbc)
{
  if (--dcdbc->ref_count == 0)
    {
      dbus_connection_remove_filter (dcdbc->session_bus,
                                     dconf_dbus_client_filter, dcdbc);
      dbus_connection_remove_filter (dcdbc->system_bus,
                                     dconf_dbus_client_filter, dcdbc);
      dbus_connection_unref (dcdbc->session_bus);
      dbus_connection_unref (dcdbc->system_bus);

      g_slice_free (DConfDBusClient, dcdbc);
    }
}

DConfDBusClient *
dconf_dbus_client_ref (DConfDBusClient *dcdbc)
{
  dcdbc->ref_count++;

  return dcdbc;
}