implement route-settings metadata and notification volume

Make a module that creates a route-settings metadata and provides
some helper functions to parse the json fields.

Load the route-settings module in the policy.

Move the Notification settings to the metadata. Listen for metadata
updates and update our state table.

Fixes #51

modules/module-route-settings-api.c

@@ -0,0 +1,138 @@
+/* WirePlumber
+ *
+ * Copyright © 2021 Collabora Ltd.
+ *    @author George Kiagiadakis <george.kiagiadakis@collabora.com>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <wp/wp.h>
+#include <pipewire/keys.h>
+#include <spa/utils/json.h>
+
+struct _WpRouteSettingsApi
+{
+  WpPlugin parent;
+
+  WpImplMetadata *metadata;
+};
+
+enum {
+  ACTION_CONVERT,
+  N_SIGNALS
+};
+
+static guint signals[N_SIGNALS] = {0};
+
+G_DECLARE_FINAL_TYPE (WpRouteSettingsApi, wp_route_settings_api,
+                      WP, ROUTE_SETTINGS_API, WpPlugin)
+G_DEFINE_TYPE (WpRouteSettingsApi, wp_route_settings_api, WP_TYPE_PLUGIN)
+
+static void
+wp_route_settings_api_init (WpRouteSettingsApi * self)
+{
+}
+
+static void
+on_metadata_activated (GObject * obj, GAsyncResult * res, gpointer user_data)
+{
+  WpTransition * transition = WP_TRANSITION (user_data);
+  WpRouteSettingsApi * self = wp_transition_get_source_object (transition);
+  g_autoptr (GError) error = NULL;
+
+  if (!wp_object_activate_finish (WP_OBJECT (obj), res, &error)) {
+    g_clear_object (&self->metadata);
+    g_prefix_error (&error, "Failed to activate WpImplMetadata: ");
+    wp_transition_return_error (transition, g_steal_pointer (&error));
+    return;
+  }
+
+  wp_object_update_features (WP_OBJECT (self), WP_PLUGIN_FEATURE_ENABLED, 0);
+}
+
+static void
+wp_route_settings_api_enable (WpPlugin * plugin, WpTransition * transition)
+{
+  WpRouteSettingsApi * self = WP_ROUTE_SETTINGS_API (plugin);
+  g_autoptr (WpCore) core = wp_object_get_core (WP_OBJECT (plugin));
+  g_return_if_fail (core);
+
+  self->metadata = wp_impl_metadata_new_full (core, "route-settings", NULL);
+  wp_object_activate (WP_OBJECT (self->metadata),
+        WP_OBJECT_FEATURES_ALL, NULL, on_metadata_activated, transition);
+}
+
+static void
+wp_route_settings_api_disable (WpPlugin * plugin)
+{
+  WpRouteSettingsApi * self = WP_ROUTE_SETTINGS_API (plugin);
+  g_clear_object (&self->metadata);
+}
+
+static gchar *
+wp_route_settings_api_convert (WpRouteSettingsApi * self,
+    const gchar * json, const gchar *field)
+{
+  struct spa_json it[3];
+  char k[128];
+
+  spa_json_init(&it[0], json, strlen(json));
+  if (spa_json_enter_object(&it[0], &it[1]) <= 0)
+    return NULL;
+
+  while (spa_json_get_string(&it[1], k, sizeof(k)-1) > 0) {
+    int len;
+    const char *value;
+
+    if (strcmp(k, field) != 0)
+      continue;
+
+    if ((len = spa_json_next(&it[1], &value)) <= 0)
+      break;
+
+    if (spa_json_is_null(value, len))
+      return NULL;
+    else if (spa_json_is_array(value, len)) {
+      GString *str;
+      spa_json_enter(&it[1], &it[2]);
+      str = g_string_new("");
+      while ((len = spa_json_next(&it[2], &value)) > 0) {
+        char v[1024];
+	if (len > 1023)
+          continue;
+        spa_json_parse_string(value, len, v);
+        g_string_append_printf(str, "%s;", v);
+      }
+      return g_string_free(str, false);
+    }
+    else
+      return g_strndup(value, len);
+  }
+  return NULL;
+}
+
+static void
+wp_route_settings_api_class_init (WpRouteSettingsApiClass * klass)
+{
+  WpPluginClass *plugin_class = (WpPluginClass *) klass;
+
+  plugin_class->enable = wp_route_settings_api_enable;
+  plugin_class->disable = wp_route_settings_api_disable;
+
+  signals[ACTION_CONVERT] = g_signal_new_class_handler (
+      "convert", G_TYPE_FROM_CLASS (klass),
+      G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
+      (GCallback) wp_route_settings_api_convert,
+      NULL, NULL, NULL,
+      G_TYPE_STRING, 2, G_TYPE_STRING, G_TYPE_STRING);
+}
+
+WP_PLUGIN_EXPORT gboolean
+wireplumber__module_init (WpCore * core, GVariant * args, GError ** error)
+{
+  wp_plugin_register (g_object_new (wp_route_settings_api_get_type (),
+          "name", "route-settings-api",
+          "core", core,
+          NULL));
+  return TRUE;
+}