/* sic_builtin.c -- basic builtin commands loaded statically
   Copyright (C) 2000 Gary V. Vaughan
  
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
  
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
  
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#if HAVE_CONFIG_H
#  include <sic/config.h>
#endif

#include "sic.h"

/* List of built in functions. */
#define builtin_functions               \
        BUILTIN (cd,             0, 1)   \
        BUILTIN (exit,           0, 1)   \
        BUILTIN (unknown,        0, -1)

/* Prototype Generator. */
#define SIC_BUILTIN(name)       \
        int name (Sic *sic, int argc, char *const argv[])

#define BUILTIN(name, min, max) \
        extern SIC_BUILTIN (CONC (builtin_, name));
builtin_functions
#undef BUILTIN

static char *path_find  (const char *command);
static int path_execute (Sic *sic, const char *path, 
			 char *const argv[]);

/* name to function map */
Builtin builtin_table[] = {

#define BUILTIN(name, min, max) \
        { STR (name), CONC (builtin_, name), (min), (max) },
  builtin_functions
#undef BUILTIN

  { NULL, NULL, -1, -1 }
};

int
builtin_cd (Sic *sic, int argc, char *const argv[])
{
  const char *destination = argv[1];
  int status = SIC_ERROR;

  if (!destination)
    destination = getenv ("HOME");
  
  if  (!destination)
      sic_result_set (sic, "unbound variable \"HOME\"", -1);
  else if (chdir (destination) < 0)
    {
      sic_result_clear  (sic);
      sic_result_append (sic, destination);
      sic_result_append (sic, ": ");
      sic_result_append (sic, xstrerror (errno));
    }
  else
    status = SIC_OKAY;

  return status;
}

int
builtin_exit (Sic *sic, int argc, char *const argv[])
{
  return SIC_EXIT;
}

/** @start 1 */
int
builtin_unknown (Sic *sic, int argc, char *const argv[])
{
  char *path = path_find (argv[0]);
  int status = SIC_ERROR;

  if (!path)
    {
      sic_result_append (sic, "command \"");
      sic_result_append (sic, argv[0]);
      sic_result_append (sic, "\" not found");
    }
  else if (path_execute (sic, path, argv) != SIC_OKAY)
    {
      sic_result_append (sic, "command \"");
      sic_result_append (sic, argv[0]);
      sic_result_append (sic, "\" failed: ");
      sic_result_append (sic, strerror (errno));
    }
  else
    status = SIC_OKAY;

  return status;
}

static char *
path_find (const char *command)
{
  char *path = xstrdup (command);
  
  if (*command == '/')
    {
      if (access (command, X_OK) < 0)
        goto notfound;
    }
  else
    {
      char *PATH = getenv ("PATH");
      char *pbeg, *pend;
      size_t len;

      for (pbeg = PATH; *pbeg != '\0'; pbeg = pend)
        {
          pbeg += strspn (pbeg, ":");
          len = strcspn (pbeg, ":");
          pend = pbeg + len;
          path = XREALLOC (char, path, 2 + len + strlen(command));
          *path = '\0';
          strncat (path, pbeg, len);
          if (path[len -1] != '/') strcat (path, "/");
          strcat (path, command);
          
          if (access (path, X_OK) == 0)
              break;
        }

      if (*pbeg == '\0')
          goto notfound;
    }

  return path;

 notfound:
  XFREE (path);
  return NULL;
}  

/** @end 1 */
static int
path_execute (Sic *sic, const char *path, char *const argv[])
{
  int status = SIC_OKAY;        /* assume successful for now */
  pid_t pid;

  pid = fork ();
  switch (pid)
    {
    case -1:                    /* fork failed */
      status = SIC_ERROR;
      break;

    case 0:
      execv (path, argv);
      _exit (1);                /* execv in child failed */
      break;

    default:                    /* wait for child to exit */
      {
        int stat;
        if (waitpid (pid, &stat, 0) == pid)
          {
            if (WIFSIGNALED (stat)
                || (WIFEXITED (stat) && (WEXITSTATUS (stat) != 0)))
              status = SIC_ERROR;
          }
        else
          status = SIC_ERROR;
      }
      break;
    }
  
  return status;
}