app_if.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright 2021, Naveen Albert <[email protected]>
 *
 * Naveen Albert <[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
 *
 * \brief If Branch Implementation
 *
 * \author Naveen Albert <[email protected]>
 *
 * \ingroup applications
 */

/*** MODULEINFO
   <support_level>extended</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/pbx.h"
#include "asterisk/module.h"
#include "asterisk/channel.h"

/*** DOCUMENTATION
   <application name="If" language="en_US">
      <synopsis>
         Start an if branch.
      </synopsis>
      <syntax>
         <parameter name="expr" required="true" />
      </syntax>
      <description>
         <para>Start an If branch.  Execution will continue inside the branch
         if expr is true.</para>
      </description>
      <see-also>
         <ref type="application">EndIf</ref>
         <ref type="application">ExitIf</ref>
      </see-also>
   </application>
   <application name="EndIf" language="en_US">
      <synopsis>
         End an if branch.
      </synopsis>
      <syntax />
      <description>
         <para>Ends the branch begun by the preceding <literal>If()</literal> application.</para>
      </description>
      <see-also>
         <ref type="application">If</ref>
         <ref type="application">ExitIf</ref>
      </see-also>
   </application>
   <application name="ExitIf" language="en_US">
      <synopsis>
         End an If branch.
      </synopsis>
      <syntax />
      <description>
         <para>Exits an <literal>If()</literal> branch, whether or not it has completed.</para>
      </description>
      <see-also>
         <ref type="application">If</ref>
         <ref type="application">EndIf</ref>
      </see-also>
   </application>
 ***/

static char *start_app = "If";
static char *stop_app = "EndIf";
static char *exit_app = "ExitIf";

#define VAR_SIZE 64


static const char *get_index(struct ast_channel *chan, const char *prefix, int idx) {
   char varname[VAR_SIZE];

   snprintf(varname, VAR_SIZE, "%s_%d", prefix, idx);
   return pbx_builtin_getvar_helper(chan, varname);
}

static struct ast_exten *find_matching_priority(struct ast_context *c, const char *exten, int priority, const char *callerid)
{
   struct ast_exten *e;
   struct ast_context *c2;
   int idx;

   for (e=ast_walk_context_extensions(c, NULL); e; e=ast_walk_context_extensions(c, e)) {
      if (ast_extension_match(ast_get_extension_name(e), exten)) {
         int needmatch = ast_get_extension_matchcid(e);
         if ((needmatch && ast_extension_match(ast_get_extension_cidmatch(e), callerid)) ||
            (!needmatch)) {
            /* This is the matching extension we want */
            struct ast_exten *p;
            for (p=ast_walk_extension_priorities(e, NULL); p; p=ast_walk_extension_priorities(e, p)) {
               if (priority != ast_get_extension_priority(p))
                  continue;
               return p;
            }
         }
      }
   }

   /* No match; run through includes */
   for (idx = 0; idx < ast_context_includes_count(c); idx++) {
      const struct ast_include *i = ast_context_includes_get(c, idx);

      for (c2=ast_walk_contexts(NULL); c2; c2=ast_walk_contexts(c2)) {
         if (!strcmp(ast_get_context_name(c2), ast_get_include_name(i))) {
            e = find_matching_priority(c2, exten, priority, callerid);
            if (e)
               return e;
         }
      }
   }
   return NULL;
}

static int find_matching_endif(struct ast_channel *chan)
{
   struct ast_context *c;
   int res = -1;

   if (ast_rdlock_contexts()) {
      ast_log(LOG_ERROR, "Failed to lock contexts list\n");
      return -1;
   }

   for (c=ast_walk_contexts(NULL); c; c=ast_walk_contexts(c)) {
      struct ast_exten *e;

      if (!ast_rdlock_context(c)) {
         if (!strcmp(ast_get_context_name(c), ast_channel_context(chan))) {
            /* This is the matching context we want */
            int cur_priority = ast_channel_priority(chan) + 1, level=1;

            for (e = find_matching_priority(c, ast_channel_exten(chan), cur_priority,
               S_COR(ast_channel_caller(chan)->id.number.valid, ast_channel_caller(chan)->id.number.str, NULL));
               e;
               e = find_matching_priority(c, ast_channel_exten(chan), ++cur_priority,
                  S_COR(ast_channel_caller(chan)->id.number.valid, ast_channel_caller(chan)->id.number.str, NULL))) {
               if (!strcasecmp(ast_get_extension_app(e), "IF")) {
                  level++;
               } else if (!strcasecmp(ast_get_extension_app(e), "ENDIF")) {
                  level--;
               }

               if (level == 0) {
                  res = cur_priority;
                  break;
               }
            }
         }
         ast_unlock_context(c);
         if (res > 0) {
            break;
         }
      }
   }
   ast_unlock_contexts();
   return res;
}

static int _if_exec(struct ast_channel *chan, const char *data, int end)
{
   int res=0;
   const char *if_pri = NULL;
   char *my_name = NULL;
   const char *condition = NULL, *label = NULL;
   char varname[VAR_SIZE], end_varname[VAR_SIZE];
   const char *prefix = "IF";
   size_t size=0;
   int used_index_i = -1, x=0;
   char used_index[VAR_SIZE] = "0", new_index[VAR_SIZE] = "0";

   if (!chan) {
      return -1;
   }

   for (x=0;;x++) {
      if (get_index(chan, prefix, x)) {
         used_index_i = x;
      } else
         break;
   }

   snprintf(used_index, VAR_SIZE, "%d", used_index_i);
   snprintf(new_index, VAR_SIZE, "%d", used_index_i + 1);

   if (!end)
      condition = ast_strdupa(data);

   size = strlen(ast_channel_context(chan)) + strlen(ast_channel_exten(chan)) + 32;
   my_name = ast_alloca(size);
   memset(my_name, 0, size);
   snprintf(my_name, size, "%s_%s_%d", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan));

   ast_channel_lock(chan);
   if (end) {
      label = used_index;
   } else if (!(label = pbx_builtin_getvar_helper(chan, my_name))) {
      label = new_index;
      pbx_builtin_setvar_helper(chan, my_name, label);
   }
   snprintf(varname, VAR_SIZE, "%s_%s", prefix, label);
   if ((if_pri = pbx_builtin_getvar_helper(chan, varname)) && !end) {
      if_pri = ast_strdupa(if_pri);
      snprintf(end_varname,VAR_SIZE,"END_%s",varname);
   }
   ast_channel_unlock(chan);

   if ((!end && !pbx_checkcondition(condition)) || (end > 0)) {
      /* Condition Met (clean up helper vars) */
      const char *goto_str;
      pbx_builtin_setvar_helper(chan, varname, NULL);
      pbx_builtin_setvar_helper(chan, my_name, NULL);
      snprintf(end_varname,VAR_SIZE,"END_%s",varname);
      ast_channel_lock(chan);
      if ((goto_str = pbx_builtin_getvar_helper(chan, end_varname))) {
         ast_parseable_goto(chan, goto_str);
         pbx_builtin_setvar_helper(chan, end_varname, NULL);
      } else {
         int pri = find_matching_endif(chan);
         if (pri > 0) {
            ast_verb(3, "Jumping to priority %d\n", pri);
            ast_channel_priority_set(chan, pri);
         } else if (end == 2) { /* Condition added because of end > 0 instead of end == 2 */
            ast_log(LOG_WARNING, "Couldn't find matching EndIf? (If at %s@%s priority %d)\n", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan));
         }
      }
      ast_channel_unlock(chan);
      return res;
   }

   if (!end && !if_pri) {
      char *goto_str;
      size = strlen(ast_channel_context(chan)) + strlen(ast_channel_exten(chan)) + 32;
      goto_str = ast_alloca(size);
      memset(goto_str, 0, size);
      snprintf(goto_str, size, "%s,%s,%d", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan));
      pbx_builtin_setvar_helper(chan, varname, goto_str);
   } else if (end && if_pri) {
      /* END of branch */
      snprintf(end_varname, VAR_SIZE, "END_%s", varname);
      if (! pbx_builtin_getvar_helper(chan, end_varname)) {
         char *goto_str;
         size = strlen(ast_channel_context(chan)) + strlen(ast_channel_exten(chan)) + 32;
         goto_str = ast_alloca(size);
         memset(goto_str, 0, size);
         snprintf(goto_str, size, "%s,%s,%d", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan)+1);
         pbx_builtin_setvar_helper(chan, end_varname, goto_str);
      }
      ast_parseable_goto(chan, if_pri);
   }

   return res;
}

static int if_start_exec(struct ast_channel *chan, const char *data) {
   return _if_exec(chan, data, 0);
}

static int if_end_exec(struct ast_channel *chan, const char *data) {
   return _if_exec(chan, data, 1);
}

static int if_exit_exec(struct ast_channel *chan, const char *data) {
   return _if_exec(chan, data, 2);
}

static int unload_module(void)
{
   int res;

   res = ast_unregister_application(start_app);
   res |= ast_unregister_application(stop_app);
   res |= ast_unregister_application(exit_app);

   return res;
}

static int load_module(void)
{
   int res;

   res = ast_register_application_xml(start_app, if_start_exec);
   res |= ast_register_application_xml(stop_app, if_end_exec);
   res |= ast_register_application_xml(exit_app, if_exit_exec);

   return res;
}

AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "If Branch and Conditional Execution");