pbx_lua.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2007, Digium, Inc.
 *
 * Matthew Nicholson <[email protected]>
 *
 * 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 <[email protected]>
 * \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
 * \return nothing
 *
 * This funciton is executed as the '()' operator for apps accessed through the
 * 'app' table.
 *
 * \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.
 *
 * \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.
 *
 * \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 accesing 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 maintaning 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 popluate 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 contexs.
 *
 * 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 contexs.
 *
 * 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);

   /* load the 'hints' table */
   lua_getglobal(L, "hints");
   hints = lua_gettop(L);
   if (lua_isnil(L, -1)) {
      /* hints table not found, move along */
      lua_pop(L, 1);
      return 0;
   }

   /* iterate through the hints table and register each context and
    * the hints that go along with it
    */
   for (lua_pushnil(L); lua_next(L, hints); 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 hints table and context key and value */
         lua_pop(L, 3);
         lua_pushstring(L, "Failed to find or create context\n");
         return 1;
      }

      /* register each hint */
      for (lua_pushnil(L); lua_next(L, context); lua_pop(L, 1)) {
         const char *hint_value = lua_tostring(L, -1);
         const char *hint_name;

         /* the hint value is not a string, ignore it */
         if (!hint_value) {
            continue;
         }

         /* copy the name then convert it to a string */
         lua_pushvalue(L, -2);
         if (!(hint_name = lua_tostring(L, -1))) {
            /* ignore non-string value */
            lua_pop(L, 1);
            continue;
         }

         if (ast_add_extension2(con, 0, hint_name, PRIORITY_HINT, NULL, NULL, hint_value, NULL, NULL, registrar, NULL, 0)) {
            /* remove hints table, hint name, hint value,
             * key copy, context name, and contex table */
            lua_pop(L, 6);
            lua_pushstring(L, "Error creating hint\n");
            return 1;
         }

         /* pop the name copy */
         lua_pop(L, 1);
      }
   }

   /* remove the hints table */
   lua_pop(L, 1);

   return 0;
}

/*!
 * \brief [lua_CFunction] Compare two extensions (for access from lua, don't
 * call directly)
 *
 * This function returns true if the first extension passed should match after
 * the second.  It behaves like the '<' operator.
 */
static int lua_extension_cmp(lua_State *L)
{
   const char *a = luaL_checkstring(L, -2);
   const char *b = luaL_checkstring(L, -1);

   if (ast_extension_cmp(a, b) == -1)
      lua_pushboolean(L, 1);
   else
      lua_pushboolean(L, 0);

   return 1;
}

/*!
 * \brief Load the extensions.lua file in to a buffer and execute the file
 *
 * \param L the lua_State to use
 * \param size a pointer to store the size of the buffer
 * \param file_not_openable a pointer to store if config file could be opened
 *
 * \note The caller is expected to free the buffer at some point.
 *
 * \return a pointer to the buffer
 */
static char *lua_read_extensions_file(lua_State *L, long *size, int *file_not_openable)
{
   FILE *f;
   int error_func;
   char *data;
   char *path = ast_alloca(strlen(config) + strlen(ast_config_AST_CONFIG_DIR) + 2);
   sprintf(path, "%s/%s", ast_config_AST_CONFIG_DIR, config);

   if (!(f = fopen(path, "r"))) {
      lua_pushstring(L, "cannot open '");
      lua_pushstring(L, path);
      lua_pushstring(L, "' for reading: ");
      lua_pushstring(L, strerror(errno));
      lua_concat(L, 4);

      *file_not_openable = 1;

      return NULL;
   }

   if (fseek(f, 0l, SEEK_END)) {
      fclose(f);
      lua_pushliteral(L, "error determining the size of the config file");
      return NULL;
   }

   *size = ftell(f);

   if (fseek(f, 0l, SEEK_SET)) {
      *size = 0;
      fclose(f);
      lua_pushliteral(L, "error reading config file");
      return NULL;
   }

   if (!(data = ast_malloc(*size))) {
      *size = 0;
      fclose(f);
      lua_pushstring(L, "not enough memory");
      return NULL;
   }

   if (fread(data, sizeof(char), *size, f) != *size) {
      *size = 0;
      fclose(f);
      lua_pushliteral(L, "problem reading configuration file");
      return NULL;
   }
   fclose(f);

   lua_pushcfunction(L, &lua_error_function);
   error_func = lua_gettop(L);

   if (luaL_loadbuffer(L, data, *size, "extensions.lua")
         || lua_pcall(L, 0, LUA_MULTRET, error_func)
         || lua_sort_extensions(L)
         || lua_register_switches(L)
         || lua_register_hints(L)) {
      ast_free(data);
      data = NULL;
      *size = 0;
   }

   lua_remove(L, error_func);
   return data;
}

/*!
 * \brief Load the extensions.lua file from the internal buffer
 *
 * \param L the lua_State to use
 * \param chan channel to work on
 *
 * This function also sets up some constructs used by the extensions.lua file.
 * 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_load_extensions(lua_State *L, struct ast_channel *chan)
{

   /* store a pointer to this channel */
   lua_pushlightuserdata(L, chan);
   lua_setfield(L, LUA_REGISTRYINDEX, "channel");

   luaL_openlibs(L);

   /* load and sort extensions */
   ast_mutex_lock(&config_file_lock);
   if (luaL_loadbuffer(L, config_file_data, config_file_size, "extensions.lua")
         || lua_pcall(L, 0, LUA_MULTRET, 0)
         || lua_sort_extensions(L)) {
      ast_mutex_unlock(&config_file_lock);
      return 1;
   }
   ast_mutex_unlock(&config_file_lock);

   /* now we setup special tables and functions */

   lua_create_app_table(L);
   lua_create_channel_table(L);

   lua_create_variable_metatable(L);
   lua_create_application_metatable(L);

   lua_create_autoservice_functions(L);
   lua_create_hangup_function(L);

   return 0;
}

/*!
 * \brief Reload the extensions file and update the internal buffers if it
 * loads correctly.
 *
 * \warning This function should not be called on a lua_State returned from
 * lua_get_state().
 *
 * \param L the lua_State to use (must be freshly allocated with
 * luaL_newstate(), don't use lua_get_state())
 */
static int lua_reload_extensions(lua_State *L)
{
   long size = 0;
   char *data = NULL;
   int file_not_openable = 0;

   luaL_openlibs(L);

   if (!(data = lua_read_extensions_file(L, &size, &file_not_openable))) {
      if (file_not_openable) {
         return -1;
      }
      return 1;
   }

   ast_mutex_lock(&config_file_lock);

   if (config_file_data)
      ast_free(config_file_data);

   config_file_data = data;
   config_file_size = size;

   /* merge our new contexts */
   ast_merge_contexts_and_delete(&local_contexts, local_table, registrar);
   /* merge_contexts_and_delete will actually, at the correct moment,
      set the global dialplan pointers to your local_contexts and local_table.
      It then will free up the old tables itself. Just be sure not to
      hang onto the pointers. */
   local_table = NULL;
   local_contexts = NULL;

   ast_mutex_unlock(&config_file_lock);
   return 0;
}

/*!
 * \brief Free the internal extensions buffer.
 */
static void lua_free_extensions()
{
   ast_mutex_lock(&config_file_lock);
   config_file_size = 0;
   ast_free(config_file_data);
   ast_mutex_unlock(&config_file_lock);
}

/*!
 * \brief Get the lua_State for this channel
 *
 * If no channel is passed then a new state is allocated.  States with no
 * channel assocatied with them should only be used for matching extensions.
 * If the channel does not yet have a lua state associated with it, one will be
 * created.
 *
 * \note If no channel was passed then the caller is expected to free the state
 * using lua_close().
 *
 * \return a lua_State
 */
static lua_State *lua_get_state(struct ast_channel *chan)
{
   struct ast_datastore *datastore = NULL;
   lua_State *L;

   if (!chan) {
      L = luaL_newstate();
      if (!L) {
         ast_log(LOG_ERROR, "Error allocating lua_State, no memory\n");
         return NULL;
      }

      if (lua_load_extensions(L, NULL)) {
         const char *error = lua_tostring(L, -1);
         ast_log(LOG_ERROR, "Error loading extensions.lua: %s\n", error);
         lua_close(L);
         return NULL;
      }
      return L;
   } else {
      ast_channel_lock(chan);
      datastore = ast_channel_datastore_find(chan, &lua_datastore, NULL);
      ast_channel_unlock(chan);

      if (!datastore) {
         /* nothing found, allocate a new lua state */
         datastore = ast_datastore_alloc(&lua_datastore, NULL);
         if (!datastore) {
            ast_log(LOG_ERROR, "Error allocation channel datastore for lua_State\n");
            return NULL;
         }

         datastore->data = luaL_newstate();
         if (!datastore->data) {
            ast_datastore_free(datastore);
            ast_log(LOG_ERROR, "Error allocating lua_State, no memory\n");
            return NULL;
         }

         ast_channel_lock(chan);
         ast_channel_datastore_add(chan, datastore);
         ast_channel_unlock(chan);

         L = datastore->data;

         if (lua_load_extensions(L, chan)) {
            const char *error = lua_tostring(L, -1);
            ast_log(LOG_ERROR, "Error loading extensions.lua for %s: %s\n", ast_channel_name(chan), error);

            ast_channel_lock(chan);
            ast_channel_datastore_remove(chan, datastore);
            ast_channel_unlock(chan);

            ast_datastore_free(datastore);
            return NULL;
         }
      }

      return datastore->data;
   }
}

static int exists(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data)
{
   int res;
   lua_State *L;
   struct ast_module_user *u = ast_module_user_add(chan);
   if (!u) {
      ast_log(LOG_ERROR, "Error adjusting use count, probably could not allocate memory\n");
      return 0;
   }

   L = lua_get_state(chan);
   if (!L) {
      ast_module_user_remove(u);
      return 0;
   }

   res = lua_find_extension(L, context, exten, priority, &exists, 0);

   if (!chan) lua_close(L);
   ast_module_user_remove(u);
   return res;
}

static int canmatch(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data)
{
   int res;
   lua_State *L;
   struct ast_module_user *u = ast_module_user_add(chan);
   if (!u) {
      ast_log(LOG_ERROR, "Error adjusting use count, probably could not allocate memory\n");
      return 0;
   }

   L = lua_get_state(chan);
   if (!L) {
      ast_module_user_remove(u);
      return 0;
   }

   res = lua_find_extension(L, context, exten, priority, &canmatch, 0);

   if (!chan) lua_close(L);
   ast_module_user_remove(u);
   return res;
}

static int matchmore(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data)
{
   int res;
   lua_State *L;
   struct ast_module_user *u = ast_module_user_add(chan);
   if (!u) {
      ast_log(LOG_ERROR, "Error adjusting use count, probably could not allocate memory\n");
      return 0;
   }

   L = lua_get_state(chan);
   if (!L) {
      ast_module_user_remove(u);
      return 0;
   }

   res = lua_find_extension(L, context, exten, priority, &matchmore, 0);

   if (!chan) lua_close(L);
   ast_module_user_remove(u);
   return res;
}


static int exec(struct ast_channel *chan, const char *context, const char *exten, int priority, const char *callerid, const char *data)
{
   int res, error_func;
   lua_State *L;
   struct ast_module_user *u = ast_module_user_add(chan);
   if (!u) {
      ast_log(LOG_ERROR, "Error adjusting use count, probably could not allocate memory\n");
      return -1;
   }

   L = lua_get_state(chan);
   if (!L) {
      ast_module_user_remove(u);
      return -1;
   }

   lua_pushcfunction(L, &lua_error_function);
   error_func = lua_gettop(L);

   /* push the extension function onto the stack */
   if (!lua_find_extension(L, context, exten, priority, &exists, 1)) {
      lua_pop(L, 1); /* pop the debug function */
      ast_log(LOG_ERROR, "Could not find extension %s in context %s\n", exten, context);
      if (!chan) lua_close(L);
      ast_module_user_remove(u);
      return -1;
   }

   lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
   if (lua_toboolean(L, -1)) {
      ast_autoservice_start(chan);
   }
   lua_pop(L, 1);

   lua_update_registry(L, context, exten, priority);

   lua_pushstring(L, context);
   lua_pushstring(L, exten);

   res = lua_pcall(L, 2, 0, error_func);
   if (res) {
      if (res == LUA_ERRRUN) {
         res = -1;
         if (lua_isnumber(L, -1)) {
            res = lua_tointeger(L, -1);

            if (res == LUA_GOTO_DETECTED) {
               res = 0;
            }
         } else if (lua_isstring(L, -1)) {
            const char *error = lua_tostring(L, -1);
            ast_log(LOG_ERROR, "Error executing lua extension: %s\n", error);
         }
      } else if (res == LUA_ERRERR) {
         res = -1;
         ast_log(LOG_ERROR, "Error in the lua error handler (this is probably a bug in pbx_lua)\n");
      } else if (res == LUA_ERRMEM) {
         res = -1;
         ast_log(LOG_ERROR, "Memory allocation error\n");
      }
      lua_pop(L, 1);
   }
   lua_remove(L, error_func);

   lua_getfield(L, LUA_REGISTRYINDEX, "autoservice");
   if (lua_toboolean(L, -1)) {
      ast_autoservice_stop(chan);
   }
   lua_pop(L, 1);

   if (!chan) lua_close(L);
   ast_module_user_remove(u);
   return res;
}

/*!
 * \brief Locate an extensions and optionally push the matching function on the
 * stack
 *
 * \param L the lua_State to use
 * \param context the context to look in
 * \param exten the extension to look up
 * \param priority the priority to check, '1' is the only valid priority
 * \param func the calling func, used to adjust matching behavior between,
 * match, canmatch, and matchmore
 * \param push_func whether or not to push the lua function for the given
 * extension onto the stack
 */
static int lua_find_extension(lua_State *L, const char *context, const char *exten, int priority, ast_switch_f *func, int push_func)
{
   int context_table, context_order_table, i;

   ast_debug(2, "Looking up %s@%s:%i\n", exten, context, priority);
   if (priority != 1)
      return 0;

   /* load the 'extensions' table */
   lua_getglobal(L, "extensions");
   if (lua_isnil(L, -1)) {
      ast_log(LOG_ERROR, "Unable to find 'extensions' table in extensions.lua\n");
      lua_pop(L, 1);
      return 0;
   }

   /* load the given context */
   lua_getfield(L, -1, context);
   if (lua_isnil(L, -1)) {
      lua_pop(L, 2);
      return 0;
   }

   /* remove the extensions table */
   lua_remove(L, -2);

   context_table = lua_gettop(L);

   /* load the extensions order table for this context */
   lua_getfield(L, LUA_REGISTRYINDEX, "extensions_order");
   lua_getfield(L, -1, context);

   lua_remove(L, -2);  /* remove the extensions order table */

   context_order_table = lua_gettop(L);

   /* step through the extensions looking for a match */
#if LUA_VERSION_NUM < 502
   for (i = 1; i < lua_objlen(L, context_order_table) + 1; i++) {
#else
   for (i = 1; i < lua_rawlen(L, context_order_table) + 1; i++) {
#endif
      int e_index_copy, match = 0;
      const char *e;

      lua_pushinteger(L, i);
      lua_gettable(L, context_order_table);
      lua_gettop(L);

      /* copy the key at the top of the stack for use later */
      lua_pushvalue(L, -1);
      e_index_copy = lua_gettop(L);

      if (!(e = lua_tostring(L, e_index_copy))) {
         lua_pop(L, 2);
         continue;
      }

      /* make sure this is not the 'include' extension */
      if (!strcasecmp(e, "include")) {
         lua_pop(L, 2);
         continue;
      }

      if (func == &matchmore)
         match = ast_extension_close(e, exten, E_MATCHMORE);
      else if (func == &canmatch)
         match = ast_extension_close(e, exten, E_CANMATCH);
      else
         match = ast_extension_match(e, exten);

      /* the extension matching functions return 0 on fail, 1 on
       * match, 2 on earlymatch */

      if (!match) {
         /* pop the copy and the extension */
         lua_pop(L, 2);
         continue;   /* keep trying */
      }

      if (func == &matchmore && match == 2) {
         /* We match an extension ending in '!'. The decision in
          * this case is final and counts as no match. */
         lua_pop(L, 4);
         return 0;
      }

      /* remove the context table, the context order table, the
       * extension, and the extension copy (or replace the extension
       * with the corresponding function) */
      if (push_func) {
         lua_pop(L, 1);  /* pop the copy */
         lua_gettable(L, context_table);
         lua_insert(L, -3);
         lua_pop(L, 2);
      } else {
         lua_pop(L, 4);
      }

      return 1;
   }

   /* load the includes for this context */
   lua_getfield(L, context_table, "include");
   if (lua_isnil(L, -1)) {
      lua_pop(L, 3);
      return 0;
   }

   /* remove the context and the order table*/
   lua_remove(L, context_order_table);
   lua_remove(L, context_table);

   /* Now try any includes we have in this context */
   for (lua_pushnil(L); lua_next(L, -2); lua_pop(L, 1)) {
      const char *c = lua_tostring(L, -1);
      if (!c)
         continue;

      if (lua_find_extension(L, c, exten, priority, func, push_func)) {
         /* remove the value, the key, and the includes table
          * from the stack.  Leave the function behind if
          * necessary */

         if (push_func)
            lua_insert(L, -4);

         lua_pop(L, 3);
         return 1;
      }
   }

   /* pop the includes table */
   lua_pop(L, 1);
   return 0;
}

static struct ast_switch lua_switch = {
        .name     = "Lua",
        .description = "Lua PBX Switch",
        .exists      = exists,
        .canmatch = canmatch,
        .exec     = exec,
        .matchmore   = matchmore,
};


static int load_or_reload_lua_stuff(void)
{
   int res = AST_MODULE_LOAD_SUCCESS;
   int loaded = 0;

   lua_State *L = luaL_newstate();
   if (!L) {
      ast_log(LOG_ERROR, "Error allocating lua_State, no memory\n");
      return AST_MODULE_LOAD_FAILURE;
   }

   loaded = lua_reload_extensions(L);
   if (loaded) {
      const char *error = lua_tostring(L, -1);
      ast_log(LOG_ERROR, "Error loading extensions.lua: %s\n", error);

      if (loaded < 0) {
         res = AST_MODULE_LOAD_DECLINE;
      } else {
         res = AST_MODULE_LOAD_FAILURE;
      }
   }

   lua_close(L);
   return res;
}

static int unload_module(void)
{
   ast_context_destroy(NULL, registrar);
   ast_unregister_switch(&lua_switch);
   lua_free_extensions();
   return 0;
}

static int reload(void)
{
   return load_or_reload_lua_stuff();
}

static int load_module(void)
{
   int res;

   if ((res = load_or_reload_lua_stuff()))
      return res;

   if (ast_register_switch(&lua_switch)) {
      ast_log(LOG_ERROR, "Unable to register LUA PBX switch\n");
      return AST_MODULE_LOAD_FAILURE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS, "Lua PBX Switch",
   .support_level = AST_MODULE_SUPPORT_EXTENDED,
   .load = load_module,
   .unload = unload_module,
   .reload = reload,
);