degesch: stubplement plugins

common.c

@@ -38,7 +38,7 @@
 #define FAIL(...)                                                              \
 	BLOCK_START                                                                \
 		error_set (e, __VA_ARGS__);                                            \
-		return false;                                                          \
+		return 0;                                                              \
 	BLOCK_END
 
 // --- To be moved to liberty --------------------------------------------------

degesch.c

@@ -1352,6 +1352,30 @@ REF_COUNTABLE_METHODS (server)
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
+struct plugin
+{
+	LIST_HEADER (struct plugin)
+
+	char *name;                         ///< Name of the plugin
+	struct plugin_vtable *vtable;       ///< Methods
+};
+
+struct plugin_vtable
+{
+	/// Unregister and free the plugin including all relevant resources
+	void (*free) (struct plugin *self);
+};
+
+static void
+plugin_destroy (struct plugin *self)
+{
+	self->vtable->free (self);
+	free (self->name);
+	free (self);
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
 struct app_context
 {
 	bool no_colors;                     ///< Disable attribute printing
@@ -1411,6 +1435,8 @@ struct app_context
 
 	bool running_backlog_helper;        ///< Running a backlog helper
 	int terminal_suspended;             ///< Terminal suspension level
+
+	struct plugin *plugins;             ///< Loaded plugins
 }
 *g_ctx;
 
@@ -1482,6 +1508,10 @@ app_context_init (struct app_context *self)
 static void
 app_context_free (struct app_context *self)
 {
+	// Plugins can try to use of the other fields when destroyed
+	LIST_FOR_EACH (struct plugin, iter, self->plugins)
+		plugin_destroy (iter);
+
 	config_free (&self->config);
 	for (size_t i = 0; i < ATTR_COUNT; i++)
 	{
@@ -1749,6 +1779,11 @@ static struct config_schema g_config_behaviour[] =
 	  .type      = CONFIG_ITEM_INTEGER,
 	  .validate  = config_validate_nonnegative,
 	  .default_  = "600" },
+
+	{ .name      = "plugin_autoload",
+	  .comment   = "Plugins to automatically load on start",
+	  .type      = CONFIG_ITEM_STRING_ARRAY,
+	  .validate  = config_validate_nonjunk_string },
 	{}
 };
 
@@ -7094,6 +7129,125 @@ server_rename (struct app_context *ctx, struct server *s, const char *new_name)
 	}
 }
 
+// --- Plugins -----------------------------------------------------------------
+
+typedef struct plugin *(*plugin_load_fn)
+	(struct app_context *ctx, const char *filename, struct error **e);
+
+// We can potentially add support for other scripting languages if so desired,
+// however this possibility is just a byproduct of abstraction
+static plugin_load_fn g_plugin_loaders[] =
+{
+};
+
+static struct plugin *
+plugin_load_from_filename (struct app_context *ctx, const char *filename,
+	struct error **e)
+{
+	struct plugin *plugin = NULL;
+	struct error *error = NULL;
+	for (size_t i = 0; i < N_ELEMENTS (g_plugin_loaders); i++)
+		if ((plugin = g_plugin_loaders[i](ctx, filename, &error)) || error)
+			break;
+
+	if (error)
+		error_propagate (e, error);
+	else if (!plugin)
+		FAIL ("no plugin handler for \"%s\"", filename);
+	return plugin;
+}
+
+static struct plugin *
+plugin_find (struct app_context *ctx, const char *name)
+{
+	LIST_FOR_EACH (struct plugin, iter, ctx->plugins)
+		if (!strcmp (name, iter->name))
+			return iter;
+	return NULL;
+}
+
+static char *
+plugin_resolve_relative_filename (const char *filename)
+{
+	struct str_vector paths;
+	str_vector_init (&paths);
+	get_xdg_data_dirs (&paths);
+	char *result = resolve_relative_filename_generic
+		(&paths, PROGRAM_NAME "/plugins/", filename);
+	str_vector_free (&paths);
+	return result;
+}
+
+static struct plugin *
+plugin_load_by_name (struct app_context *ctx, const char *name,
+	struct error **e)
+{
+	struct plugin *plugin = plugin_find (ctx, name);
+	if (plugin)
+		FAIL ("plugin already loaded");
+
+	// As a side effect, a plugin can be loaded multiple times by giving
+	// various relative or non-relative paths to the function; this is not
+	// supposed to be fool-proof though, that requires other mechanisms
+	char *filename = resolve_filename (name, plugin_resolve_relative_filename);
+	if (!filename)
+		FAIL ("file not found");
+
+	plugin = plugin_load_from_filename (ctx, filename, e);
+	free (filename);
+	return plugin;
+}
+
+static void
+plugin_load (struct app_context *ctx, const char *name)
+{
+	struct error *e = NULL;
+	struct plugin *plugin = plugin_load_by_name (ctx, name, &e);
+	if (plugin)
+	{
+		log_global_status (ctx, "Plugin \"#s\" loaded", name);
+		LIST_PREPEND (ctx->plugins, plugin);
+		plugin->name = xstrdup (name);
+	}
+	else
+	{
+		log_global_error (ctx, "Can't load plugin \"#s\": #s",
+			name, e->message);
+		error_free (e);
+	}
+}
+
+static void
+plugin_unload (struct app_context *ctx, const char *name)
+{
+	struct plugin *plugin = plugin_find (ctx, name);
+	if (!plugin)
+		log_global_error (ctx, "Can't unload plugin \"#s\": #s",
+			name, "plugin not loaded");
+	else
+	{
+		log_global_status (ctx, "Plugin \"#s\" unloaded", name);
+		LIST_UNLINK (ctx->plugins, plugin);
+		plugin_destroy (plugin);
+	}
+}
+
+static void
+load_plugins (struct app_context *ctx)
+{
+	const char *plugins = get_config_string
+		(ctx->config.root, "behaviour.plugin_autoload");
+	if (plugins)
+	{
+		struct str_vector v;
+		str_vector_init (&v);
+		cstr_split_ignore_empty (plugins, ',', &v);
+		for (size_t i = 0; i < v.len; i++)
+			plugin_load (ctx, v.vector[i]);
+		str_vector_free (&v);
+	}
+}
+
 // --- User input handling -----------------------------------------------------
 
 // HANDLER_NEEDS_REG is primarily for message sending commands,
@@ -7502,6 +7656,40 @@ handle_command_save (struct handler_args *a)
 	return true;
 }
 
+static void
+show_plugin_list (struct app_context *ctx)
+{
+	log_global_indent (ctx, "");
+	log_global_indent (ctx, "Plugins:");
+	LIST_FOR_EACH (struct plugin, iter, ctx->plugins)
+		log_global_indent (ctx, "  #s", iter->name);
+}
+
+static bool
+handle_command_plugin (struct handler_args *a)
+{
+	char *action = cut_word (&a->arguments);
+	if (!*action || !strcasecmp_ascii (action, "list"))
+		show_plugin_list (a->ctx);
+	else if (!strcasecmp_ascii (action, "load"))
+	{
+		if (!*a->arguments)
+			return false;
+
+		plugin_load (a->ctx, cut_word (&a->arguments));
+	}
+	else if (!strcasecmp_ascii (action, "unload"))
+	{
+		if (!*a->arguments)
+			return false;
+
+		plugin_unload (a->ctx, cut_word (&a->arguments));
+	}
+	else
+		return false;
+	return true;
+}
+
 static bool
 show_aliases_list (struct app_context *ctx)
 {
@@ -8219,6 +8407,9 @@ g_command_handlers[] =
 	{ "save",       "Save configuration",
 	  NULL,
 	  handle_command_save,       0 },
+	{ "plugin",     "Manage plugins",
+	  "list | load <name> | unload <name>",
+	  handle_command_plugin,     0 },
 
 	{ "alias",      "List or set aliases",
 	  "[<name> <definition>]",
@@ -10189,6 +10380,7 @@ main (int argc, char *argv[])
 	toggle_bracketed_paste (true);
 
 	// Finally, we juice the configuration for some servers to create
+	load_plugins (&ctx);
 	load_servers (&ctx);
 
 	ctx.polling = true;