pbx_lua.c

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2007, Digium, Inc.
 *
 * Matthew Nicholson <mnicholson@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*!
 * \file
 *
 * \author Matthew Nicholson <mnicholson@digium.com>
 * \brief Lua PBX Switch
 *
 */

/*** MODULEINFO
	<depend>lua</depend>
	<support_level>extended</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/logger.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/module.h"
#include "asterisk/cli.h"
#include "asterisk/utils.h"
#include "asterisk/term.h"
#include "asterisk/paths.h"
#include "asterisk/hashtab.h"

#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

static char *config = "extensions.lua";
static char *registrar = "pbx_lua";

#ifdef LOW_MEMORY
#define LUA_EXT_DATA_SIZE 256
#else
#define LUA_EXT_DATA_SIZE 8192
#endif
#define LUA_BUF_SIZE 4096

/* This value is used by the lua engine to signal that a Goto or dialplan jump
 * was detected. Ensure this value does not conflict with any values dialplan
 * applications might return */
#define LUA_GOTO_DETECTED 5

static char *lua_read_extensions_file(lua_State *L, long *size, int *file_not_openable);
static int lua_load_extensions(lua_State *L, struct ast_channel *chan);
static int lua_reload_extensions(lua_State *L);
static void lua_free_extensions(void);
static int lua_sort_extensions(lua_State *L);
static int lua_register_switches(lua_State *L);
static int lua_register_hints(lua_State *L);
static int lua_extension_cmp(lua_State *L);
static int lua_find_extension(lua_State *L, const char *context, const char *exten, int priority, ast_switch_f *func, int push_func);
static int lua_pbx_findapp(lua_State *L);
static int lua_pbx_exec(lua_State *L);

static int lua_get_variable_value(lua_State *L);
static int lua_set_variable_value(lua_State *L);
static int lua_get_variable(lua_State *L);
static int lua_set_variable(lua_State *L);
static int lua_func_read(lua_State *L);

static int lua_autoservice_start(lua_State *L);
static int lua_autoservice_stop(lua_State *L);
static int lua_autoservice_status(lua_State *L);
static int lua_check_hangup(lua_State *L);
static int lua_error_function(lua_State *L);

static void lua_update_registry(lua_State *L, const char *context, const char *exten, int priority);
static void lua_push_variable_table(lua_State *L);
static void lua_create_app_table(lua_State *L);
static void lua_create_channel_table(lua_State *L);
static void lua_create_variable_metatable(lua_State *L);
static void lua_create_application_metatable(lua_State *L);
static void lua_create_autoservice_functions(lua_State *L);
static void lua_create_hangup_function(lua_State *L);
static void lua_concat_args(lua_State *L, int start, int nargs);

static void lua_state_destroy(void *data);
static void lua_datastore_fixup(void *data, struct ast_channel *old_chan, struct ast_channel *new_chan);
static lua_State *lua_get_state(struct ast_channel *chan);

static int exists(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data);
static int canmatch(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data);
static int matchmore(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data);
static int exec(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data);

AST_MUTEX_DEFINE_STATIC(config_file_lock);
static char *config_file_data = NULL;
static long config_file_size = 0;

static struct ast_context *local_contexts = NULL;
static struct ast_hashtab *local_table = NULL;

static const struct ast_datastore_info lua_datastore = {
	.type = "lua",
	.destroy = lua_state_destroy,
	.chan_fixup = lua_datastore_fixup,
};


/*!
 * \brief The destructor for lua_datastore
 */
static void lua_state_destroy(void *data)
{
	if (data)
		lua_close(data);
}

/*!
 * \brief The fixup function for the lua_datastore.
 * \param data the datastore data, in this case it will be a lua_State
 * \param old_chan the channel we are moving from
 * \param new_chan the channel we are moving to
 *
 * This function updates our internal channel pointer.
 */
static void lua_datastore_fixup(void *data, struct ast_channel *old_chan, struct ast_channel *new_chan)
{
	lua_State *L = data;
	lua_pushlightuserdata(L, new_chan);
	lua_setfield(L, LUA_REGISTRYINDEX, "channel");
}

/*!
 * \brief [lua_CFunction] Find an app and return it in a lua table (for access from lua, don't
 * call directly)
 *
 * This function would be called in the following example as it would be found
 * in extensions.lua.
 *
 * \code
 * app.dial
 * \endcode
 */
static int lua_pbx_findapp(lua_State *L)
{
	const char *app_name = luaL_checkstring(L, 2);

	lua_newtable(L);

	lua_pushstring(L, "name");
	lua_pushstring(L, app_name);
	lua_settable(L, -3);

	luaL_getmetatable(L, "application");
	lua_setmetatable(L, -2);

	return 1;
}

/*!
 * \brief [lua_CFunction] This function is part of the 'application' metatable
 * and is used to execute applications similar to pbx_exec() (for access from
 * lua, don't call directly)
 *
 * \param L the lua_State to use
 *
 * This funciton is executed as the '()' operator for apps accessed through the
 * 'app' table.
 *
 * \return LUA error
 *
 * \code
 * app.playback('demo-congrats')
 * \endcode
 */
static int lua_pbx_exec(lua_State *L)
{
	int res, nargs = lua_gettop(L);
	const char *data = "";
	char *app_name, *context, *exten;
	char tmp[80], tmp2[80], tmp3[LUA_EXT_DATA_SIZE];
	int priority, autoservice;
	struct ast_app *app;
	struct ast_channel *chan;

	lua_getfield(L, 1, "name");
	app_name = ast_strdupa(lua_tostring(L, -1));
	lua_pop(L, 1);

	if (!(app = pbx_findapp(app_name))) {
		lua_pushstring(L, "application '");
		lua_pushstring(L, app_name);
		lua_pushstring(L, "' not found");
		lua_concat(L, 3);
		return lua_error(L);
	}


	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	context = ast_strdupa(ast_channel_context(chan));
	exten = ast_strdupa(ast_channel_exten(chan));
	priority = ast_channel_priority(chan);

	lua_concat_args(L, 2, nargs);
	data = lua_tostring(L, -1);

	ast_verb(3, "Executing [%s@%s:%d] %s(\"%s\", \"%s\")\n",
			exten, context, priority,
			term_color(tmp, app_name, COLOR_BRCYAN, 0, sizeof(tmp)),
			term_color(tmp2, ast_channel_name(chan), COLOR_BRMAGENTA, 0, sizeof(tmp2)),
			term_color(tmp3, data, COLOR_BRMAGENTA, 0, sizeof(tmp3)));

	lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
	autoservice = lua_toboolean(L, -1);
	lua_pop(L, 1);

	if (autoservice)
		ast_autoservice_stop(chan);

	res = pbx_exec(chan, app, data);

	lua_pop(L, 1); /* pop data */
	data = "";

	if (autoservice)
		ast_autoservice_start(chan);

	/* error executing an application, report it */
	if (res) {
		lua_pushinteger(L, res);
		return lua_error(L);
	}

	if (strcmp(context, ast_channel_context(chan))) {
		lua_pushstring(L, context);
		lua_pushstring(L, ast_channel_context(chan));
		lua_pushliteral(L, "context");
	} else if (strcmp(exten, ast_channel_exten(chan))) {
		lua_pushstring(L, exten);
		lua_pushstring(L, ast_channel_exten(chan));
		lua_pushliteral(L, "exten");
	} else if (priority != ast_channel_priority(chan)) {
		lua_pushinteger(L, priority);
		lua_pushinteger(L, ast_channel_priority(chan));
		lua_pushliteral(L, "priority");
	} else {
		/* no goto - restore the original position back
		 * to lua state, in case this was a recursive dialplan
		 * call (a dialplan application re-entering dialplan) */
		lua_update_registry(L, context, exten, priority);
		return 0;
	}

	/* goto detected - construct error message */
	lua_insert(L, -3);

	lua_pushliteral(L, " changed from ");
	lua_insert(L, -3);

	lua_pushliteral(L, " to ");
	lua_insert(L, -2);

	lua_concat(L, 5);

	ast_debug(2, "Goto detected: %s\n", lua_tostring(L, -1));
	lua_pop(L, 1);

	/* let the lua engine know it needs to return control to the pbx */
	lua_pushinteger(L, LUA_GOTO_DETECTED);
	lua_error(L);

	return 0;
}

/*!
 * \brief [lua_CFunction] Used to get the value of a variable or dialplan
 * function (for access from lua, don't call directly)
 *
 * The value of the variable or function is returned.  This function is the
 * 'get()' function in the following example as would be seen in
 * extensions.lua.
 *
 * \return LUA error
 *
 * \code
 * channel.variable:get()
 * \endcode
 */
static int lua_get_variable_value(lua_State *L)
{
	struct ast_channel *chan;
	char *value = NULL, *name;
	char *workspace = ast_alloca(LUA_BUF_SIZE);
	int autoservice;

	workspace[0] = '\0';

	if (!lua_istable(L, 1)) {
		lua_pushstring(L, "User probably used '.' instead of ':' for retrieving a channel variable value");
		return lua_error(L);
	}

	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	lua_getfield(L, 1, "name");
	name = ast_strdupa(lua_tostring(L, -1));
	lua_pop(L, 1);

	lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
	autoservice = lua_toboolean(L, -1);
	lua_pop(L, 1);

	if (autoservice)
		ast_autoservice_stop(chan);

	/* if this is a dialplan function then use ast_func_read(), otherwise
	 * use pbx_retrieve_variable() */
	if (!ast_strlen_zero(name) && name[strlen(name) - 1] == ')') {
		value = ast_func_read(chan, name, workspace, LUA_BUF_SIZE) ? NULL : workspace;
	} else {
		pbx_retrieve_variable(chan, name, &value, workspace, LUA_BUF_SIZE, ast_channel_varshead(chan));
	}

	if (autoservice)
		ast_autoservice_start(chan);

	if (value) {
		lua_pushstring(L, value);
	} else {
		lua_pushnil(L);
	}

	return 1;
}

/*!
 * \brief [lua_CFunction] Used to set the value of a variable or dialplan
 * function (for access from lua, don't call directly)
 *
 * This function is the 'set()' function in the following example as would be
 * seen in extensions.lua.
 *
 * \return LUA error
 *
 * \code
 * channel.variable:set("value")
 * \endcode
 */
static int lua_set_variable_value(lua_State *L)
{
	const char *name, *value;
	struct ast_channel *chan;
	int autoservice;

	if (!lua_istable(L, 1)) {
		lua_pushstring(L, "User probably used '.' instead of ':' for setting a channel variable");
		return lua_error(L);
	}

	lua_getfield(L, 1, "name");
	name = ast_strdupa(lua_tostring(L, -1));
	lua_pop(L, 1);

	value = luaL_checkstring(L, 2);

	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
	autoservice = lua_toboolean(L, -1);
	lua_pop(L, 1);

	if (autoservice)
		ast_autoservice_stop(chan);

	pbx_builtin_setvar_helper(chan, name, value);

	if (autoservice)
		ast_autoservice_start(chan);

	return 0;
}

/*!
 * \brief Update the lua registry with the given context, exten, and priority.
 *
 * \param L the lua_State to use
 * \param context the new context
 * \param exten the new exten
 * \param priority the new priority
 */
static void lua_update_registry(lua_State *L, const char *context, const char *exten, int priority)
{
	lua_pushstring(L, context);
	lua_setfield(L, LUA_REGISTRYINDEX, "context");

	lua_pushstring(L, exten);
	lua_setfield(L, LUA_REGISTRYINDEX, "exten");

	lua_pushinteger(L, priority);
	lua_setfield(L, LUA_REGISTRYINDEX, "priority");
}

/*!
 * \brief Push a 'variable' table on the stack for access the channel variable
 * with the given name.
 *
 * The value on the top of the stack is popped and used as the name.
 *
 * \param L the lua_State to use
 */
static void lua_push_variable_table(lua_State *L)
{
	lua_newtable(L);
	luaL_getmetatable(L, "variable");
	lua_setmetatable(L, -2);

	lua_insert(L, -2); /* move the table after the name */
	lua_setfield(L, -2, "name");

	lua_pushcfunction(L, &lua_get_variable_value);
	lua_setfield(L, -2, "get");

	lua_pushcfunction(L, &lua_set_variable_value);
	lua_setfield(L, -2, "set");
}

/*!
 * \brief Create the global 'app' table for executing applications
 *
 * \param L the lua_State to use
 */
static void lua_create_app_table(lua_State *L)
{
	lua_newtable(L);
	luaL_newmetatable(L, "app");

	lua_pushstring(L, "__index");
	lua_pushcfunction(L, &lua_pbx_findapp);
	lua_settable(L, -3);

	lua_setmetatable(L, -2);
	lua_setglobal(L, "app");
}

/*!
 * \brief Create the global 'channel' table for accessing channel variables
 *
 * \param L the lua_State to use
 */
static void lua_create_channel_table(lua_State *L)
{
	lua_newtable(L);
	luaL_newmetatable(L, "channel_data");

	lua_pushstring(L, "__index");
	lua_pushcfunction(L, &lua_get_variable);
	lua_settable(L, -3);

	lua_pushstring(L, "__newindex");
	lua_pushcfunction(L, &lua_set_variable);
	lua_settable(L, -3);

	lua_setmetatable(L, -2);
	lua_setglobal(L, "channel");
}

/*!
 * \brief Create the 'variable' metatable, used to retrieve channel variables
 *
 * \param L the lua_State to use
 */
static void lua_create_variable_metatable(lua_State *L)
{
	luaL_newmetatable(L, "variable");

	lua_pushstring(L, "__call");
	lua_pushcfunction(L, &lua_func_read);
	lua_settable(L, -3);

	lua_pop(L, 1);
}

/*!
 * \brief Create the 'application' metatable, used to execute asterisk
 * applications from lua
 *
 * \param L the lua_State to use
 */
static void lua_create_application_metatable(lua_State *L)
{
	luaL_newmetatable(L, "application");

	lua_pushstring(L, "__call");
	lua_pushcfunction(L, &lua_pbx_exec);
	lua_settable(L, -3);

	lua_pop(L, 1);
}

/*!
 * \brief Create the autoservice functions
 *
 * \param L the lua_State to use
 */
static void lua_create_autoservice_functions(lua_State *L)
{
	lua_pushcfunction(L, &lua_autoservice_start);
	lua_setglobal(L, "autoservice_start");

	lua_pushcfunction(L, &lua_autoservice_stop);
	lua_setglobal(L, "autoservice_stop");

	lua_pushcfunction(L, &lua_autoservice_status);
	lua_setglobal(L, "autoservice_status");

	lua_pushboolean(L, 1);
	lua_setfield(L, LUA_REGISTRYINDEX, "autoservice");
}

/*!
 * \brief Create the hangup check function
 *
 * \param L the lua_State to use
 */
static void lua_create_hangup_function(lua_State *L)
{
	lua_pushcfunction(L, &lua_check_hangup);
	lua_setglobal(L, "check_hangup");
}

/*!
 * \brief [lua_CFunction] Return a lua 'variable' object (for access from lua, don't call
 * directly)
 *
 * This function is called to lookup a variable construct a 'variable' object.
 * It would be called in the following example as would be seen in
 * extensions.lua.
 *
 * \code
 * channel.variable
 * \endcode
 */
static int lua_get_variable(lua_State *L)
{
	struct ast_channel *chan;
	const char *name = luaL_checkstring(L, 2);
	char *value = NULL;
	char *workspace = ast_alloca(LUA_BUF_SIZE);
	workspace[0] = '\0';

	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	lua_pushvalue(L, 2);
	lua_push_variable_table(L);

	/* if this is not a request for a dialplan funciton attempt to retrieve
	 * the value of the variable */
	if (!ast_strlen_zero(name) && name[strlen(name) - 1] != ')') {
		pbx_retrieve_variable(chan, name, &value, workspace, LUA_BUF_SIZE, ast_channel_varshead(chan));
	}

	if (value) {
		lua_pushstring(L, value);
		lua_setfield(L, -2, "value");
	}

	return 1;
}

/*!
 * \brief [lua_CFunction] Set the value of a channel variable or dialplan
 * function (for access from lua, don't call directly)
 *
 * This function is called to set a variable or dialplan function.  It would be
 * called in the following example as would be seen in extensions.lua.
 *
 * \code
 * channel.variable = "value"
 * \endcode
 */
static int lua_set_variable(lua_State *L)
{
	struct ast_channel *chan;
	int autoservice;
	const char *name = luaL_checkstring(L, 2);
	const char *value = luaL_checkstring(L, 3);

	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
	autoservice = lua_toboolean(L, -1);
	lua_pop(L, 1);

	if (autoservice)
		ast_autoservice_stop(chan);

	pbx_builtin_setvar_helper(chan, name, value);

	if (autoservice)
		ast_autoservice_start(chan);

	return 0;
}

/*!
 * \brief Concatenate a list of lua function arguments into a comma separated
 * string.
 * \param L the lua_State to use
 * \param start the index of the first argument
 * \param nargs the number of args
 *
 * The resulting string will be left on the top of the stack.
 */
static void lua_concat_args(lua_State *L, int start, int nargs) {
	int concat = 0;
	int i = start + 1;

	if (start <= nargs && !lua_isnil(L, start)) {
		lua_pushvalue(L, start);
		concat += 1;
	}

	for (; i <= nargs; i++) {
		if (lua_isnil(L, i)) {
			lua_pushliteral(L, ",");
			concat += 1;
		} else {
			lua_pushliteral(L, ",");
			lua_pushvalue(L, i);
			concat += 2;
		}
	}

	lua_concat(L, concat);
}

/*!
 * \brief [lua_CFunction] Create a 'variable' object for accessing a dialplan
 * function (for access from lua, don't call directly)
 *
 * This function is called to create a 'variable' object to access a dialplan
 * function.  It would be called in the following example as would be seen in
 * extensions.lua.
 *
 * \code
 * channel.func("arg1", "arg2", "arg3")
 * \endcode
 *
 * To actually do anything with the resulting value you must use the 'get()'
 * and 'set()' methods (the reason is the resulting value is not a value, but
 * an object in the form of a lua table).
 */
static int lua_func_read(lua_State *L)
{
	int nargs = lua_gettop(L);

	/* build a string in the form of "func_name(arg1,arg2,arg3)" */
	lua_getfield(L, 1, "name");
	lua_pushliteral(L, "(");
	lua_concat_args(L, 2, nargs);
	lua_pushliteral(L, ")");
	lua_concat(L, 4);

	lua_push_variable_table(L);
	return 1;
}

/*!
 * \brief [lua_CFunction] Tell pbx_lua to maintain an autoservice on this
 * channel (for access from lua, don't call directly)
 *
 * \param L the lua_State to use
 *
 * This function will set a flag that will cause pbx_lua to maintain an
 * autoservice on this channel.  The autoservice will automatically be stopped
 * and restarted before calling applications and functions.
 */
static int lua_autoservice_start(lua_State *L)
{
	struct ast_channel *chan;

	lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
	if (lua_toboolean(L, -1)) {
		/* autservice already running */
		lua_pop(L, 1);
		return 0;
	}
	lua_pop(L, 1);

	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	ast_autoservice_start(chan);

	lua_pushboolean(L, 1);
	lua_setfield(L, LUA_REGISTRYINDEX, "autoservice");
	return 0;
}

/*!
 * \brief [lua_CFunction] Tell pbx_lua to stop maintaining an autoservice on
 * this channel (for access from lua, don't call directly)
 *
 * \param L the lua_State to use
 *
 * This function will stop any autoservice running and turn off the autoservice
 * flag.  If this function returns false, it's probably because no autoservice
 * was running to begin with.
 */
static int lua_autoservice_stop(lua_State *L)
{
	struct ast_channel *chan;

	lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
	if (!lua_toboolean(L, -1)) {
		/* no autservice running */
		lua_pop(L, 1);
		return 0;
	}
	lua_pop(L, 1);

	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	ast_autoservice_stop(chan);

	lua_pushboolean(L, 0);
	lua_setfield(L, LUA_REGISTRYINDEX, "autoservice");
	return 0;
}

/*!
 * \brief [lua_CFunction] Get the status of the autoservice flag (for access
 * from lua, don't call directly)
 *
 * \param L the lua_State to use
 *
 * \return This function returns the status of the autoservice flag as a
 * boolean to its lua caller.
 */
static int lua_autoservice_status(lua_State *L)
{
	lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
	return 1;
}

/*!
 * \brief [lua_CFunction] Check if this channel has been hungup or not (for
 * access from lua, don't call directly)
 *
 * \param L the lua_State to use
 *
 * \return This function returns true if the channel was hungup
 */
static int lua_check_hangup(lua_State *L)
{
	struct ast_channel *chan;
	lua_getfield(L, LUA_REGISTRYINDEX, "channel");
	chan = lua_touserdata(L, -1);
	lua_pop(L, 1);

	lua_pushboolean(L, ast_check_hangup(chan));
	return 1;
}

/*!
 * \brief [lua_CFunction] Handle lua errors (for access from lua, don't call
 * directly)
 *
 * \param L the lua_State to use
 */
static int lua_error_function(lua_State *L)
{
	int message_index;

	/* pass number arguments right through back to asterisk*/
	if (lua_isnumber(L, -1)) {
		return 1;
	}

	/* if we are here then we have a string error message, let's attach a
	 * backtrace to it */
	message_index = lua_gettop(L);

	/* prepare to prepend a new line to the traceback */
	lua_pushliteral(L, "\n");

	lua_getglobal(L, "debug");
	if (!lua_istable(L, -1)) {
		/* Have no 'debug' table for whatever reason */
		lua_pop(L, 2);
		/*  Original err message is on stack top now */
		return 1;
	}
	lua_getfield(L, -1, "traceback");
	if (!lua_isfunction(L, -1)) {
		/* Same here for traceback function */
		lua_pop(L, 3);
		/*  Original err message is on stack top now */
		return 1;
	}
	lua_remove(L, -2); /* remove the 'debug' table */

	lua_pushvalue(L, message_index);
	lua_remove(L, message_index);

	lua_pushnumber(L, 2);

	lua_call(L, 2, 1);

	/* prepend the new line we prepared above */
	lua_concat(L, 2);

	return 1;
}

/*!
 * \brief Store the sort order of each context

 * In the event of an error, an error string will be pushed onto the lua stack.
 *
 * \retval 0 success
 * \retval 1 failure
 */
static int lua_sort_extensions(lua_State *L)
{
	int extensions, extensions_order;

	/* create the extensions_order table */
	lua_newtable(L);
	lua_setfield(L, LUA_REGISTRYINDEX, "extensions_order");
	lua_getfield(L, LUA_REGISTRYINDEX, "extensions_order");
	extensions_order = lua_gettop(L);

	/* sort each context in the extensions table */
	/* load the 'extensions' table */
	lua_getglobal(L, "extensions");
	extensions = lua_gettop(L);
	if (lua_isnil(L, -1)) {
		lua_pop(L, 1);
		lua_pushstring(L, "Unable to find 'extensions' table in extensions.lua\n");
		return 1;
	}

	/* iterate through the extensions table and create a
	 * matching table (holding the sort order) in the
	 * extensions_order table for each context that is found
	 */
	for (lua_pushnil(L); lua_next(L, extensions); lua_pop(L, 1)) {
		int context = lua_gettop(L);
		int context_name = context - 1;
		int context_order;

		/* copy the context_name to be used as the key for the
		 * context_order table in the extensions_order table later */
		lua_pushvalue(L, context_name);

		/* create the context_order table */
		lua_newtable(L);
		context_order = lua_gettop(L);

		/* iterate through this context an populate the corrisponding
		 * table in the extensions_order table */
		for (lua_pushnil(L); lua_next(L, context); lua_pop(L, 1)) {
			int exten = lua_gettop(L) - 1;
#if LUA_VERSION_NUM < 502
			lua_pushinteger(L, lua_objlen(L, context_order) + 1);
#else
			lua_pushinteger(L, lua_rawlen(L, context_order) + 1);
#endif
			lua_pushvalue(L, exten);
			lua_settable(L, context_order);
		}
		lua_settable(L, extensions_order); /* put the context_order table in the extensions_order table */

		/* now sort the new table */

		/* push the table.sort function */
		lua_getglobal(L, "table");
		lua_getfield(L, -1, "sort");
		lua_remove(L, -2); /* remove the 'table' table */

		/* push the context_order table */
		lua_pushvalue(L, context_name);
		lua_gettable(L, extensions_order);

		/* push the comp function */
		lua_pushcfunction(L, &lua_extension_cmp);

		if (lua_pcall(L, 2, 0, 0)) {
			lua_insert(L, -5);
			lua_pop(L, 4);
			return 1;
		}
	}

	/* remove the extensions table and the extensions_order table */
	lua_pop(L, 2);
	return 0;
}

/*!
 * \brief Register dialplan switches for our pbx_lua contexts.
 *
 * In the event of an error, an error string will be pushed onto the lua stack.
 *
 * \retval 0 success
 * \retval 1 failure
 */
static int lua_register_switches(lua_State *L)
{
	int extensions;
	struct ast_context *con = NULL;

	/* create the hash table for our contexts */
	/* XXX do we ever need to destroy this? pbx_config does not */
	if (!local_table)
		local_table = ast_hashtab_create(17, ast_hashtab_compare_contexts, ast_hashtab_resize_java, ast_hashtab_newsize_java, ast_hashtab_hash_contexts, 0);

	/* load the 'extensions' table */
	lua_getglobal(L, "extensions");
	extensions = lua_gettop(L);
	if (lua_isnil(L, -1)) {
		lua_pop(L, 1);
		lua_pushstring(L, "Unable to find 'extensions' table in extensions.lua\n");
		return 1;
	}

	/* iterate through the extensions table and register a context and
	 * dialplan switch for each lua context
	 */
	for (lua_pushnil(L); lua_next(L, extensions); lua_pop(L, 1)) {
		int context = lua_gettop(L);
		int context_name = context - 1;
		const char *context_str = lua_tostring(L, context_name);

		/* find or create this context */
		con = ast_context_find_or_create(&local_contexts, local_table, context_str, registrar);
		if (!con) {
			/* remove extensions table and context key and value */
			lua_pop(L, 3);
			lua_pushstring(L, "Failed to find or create context\n");
			return 1;
		}

		/* register the switch */
		if (ast_context_add_switch2(con, "Lua", "", 0, registrar)) {
			/* remove extensions table and context key and value */
			lua_pop(L, 3);
			lua_pushstring(L, "Unable to create switch for context\n");
			return 1;
		}
	}

	/* remove the extensions table */
	lua_pop(L, 1);
	return 0;
}

/*!
 * \brief Register dialplan hints for our pbx_lua contexts.
 *
 * In the event of an error, an error string will be pushed onto the lua stack.
 *
 * \retval 0 success
 * \retval 1 failure
 */
static int lua_register_hints(lua_State *L)
{
	int hints;
	struct ast_context *con = NULL;

	/* create the hash table for our contexts */
	/* XXX do we ever need to destroy this? pbx_config does not */
	if (!local_table)
		local_table = ast_hashtab_create(17, ast_hashtab_compare_contexts, ast_hashtab_resize_java, ast_hashtab_newsize_java, ast_hashtab_hash_contexts, 0);