/*      $NetBSD: interp_parse.c,v 1.6 2018/09/04 15:08:30 riastradh Exp $       */

/*-
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* Jordan K. Hubbard
* 29 August 1998
*
* The meat of the simple parser.
*/

#include <sys/cdefs.h>
/* __FBSDID("$FreeBSD: src/sys/boot/common/interp_parse.c,v 1.10 2003/08/25 23:30:41 obrien Exp $"); */

#include <lib/libsa/stand.h>
#include <lib/libsa/loadfile.h>
#include <lib/libkern/libkern.h>

#include "bootstrap.h"

static void      clean(void);
static int       insert(int *argcp, char *buf);
static char     *variable_lookup(char *name);

#define PARSE_BUFSIZE   1024    /* maximum size of one element */
#define MAXARGS         20      /* maximum number of elements */
static char             *args[MAXARGS];

/*
* parse: accept a string of input and "parse" it for backslash
* substitutions and environment variable expansions (${var}),
* returning an argc/argv style vector of whitespace separated
* arguments.  Returns 0 on success, 1 on failure (ok, ok, so I
* wimped-out on the error codes! :).
*
* Note that the argv array returned must be freed by the caller, but
* we own the space allocated for arguments and will free that on next
* invocation.  This allows argv consumers to modify the array if
* required.
*
* NB: environment variables that expand to more than one whitespace
* separated token will be returned as a single argv[] element, not
* split in turn.  Expanded text is also immune to further backslash
* elimination or expansion since this is a one-pass, non-recursive
* parser.  You didn't specify more than this so if you want more, ask
* me. - jkh
*/

#define PARSE_FAIL(expr) \
if (expr) { \
   printf("fail at line %d\n", __LINE__); \
   clean(); \
   free(copy); \
   free(buf); \
   return 1; \
}

/* Accept the usual delimiters for a variable, returning counterpart */
static char
isdelim(int ch)
{
   if (ch == '{')
       return '}';
   else if (ch == '(')
       return ')';
   return '\0';
}

static int
isquote(int ch)
{
   return (ch == '\'' || ch == '"');
}

int
parse(int *argc, char ***argv, char *str)
{
   int ac;
   char *val, *p, *q, *copy = NULL;
   size_t i = 0;
   char token, tmp, quote, *buf;
   enum { STR, VAR, WHITE } state;

   ac = *argc = 0;
   quote = 0;
   if (!str || (p = copy = backslash(str)) == NULL)
       return 1;

   /* Initialize vector and state */
   clean();
   state = STR;
   buf = (char *)alloc(PARSE_BUFSIZE);
   token = 0;

   /* And awaaaaaaaaay we go! */
   while (*p) {
       switch (state) {
       case STR:
           if ((*p == '\\') && p[1]) {
               p++;
               PARSE_FAIL(i == (PARSE_BUFSIZE - 1));
               buf[i++] = *p++;
           } else if (isquote(*p)) {
               quote = quote ? 0 : *p;
               ++p;
           }
           else if (isspace(*p) && !quote) {
               state = WHITE;
               if (i) {
                   buf[i] = '\0';
                   PARSE_FAIL(insert(&ac, buf));
                   i = 0;
               }
               ++p;
           } else if (*p == '$') {
               token = isdelim(*(p + 1));
               if (token)
                   p += 2;
               else
                   ++p;
               state = VAR;
           } else {
               PARSE_FAIL(i == (PARSE_BUFSIZE - 1));
               buf[i++] = *p++;
           }
           break;

       case WHITE:
           if (isspace(*p))
               ++p;
           else
               state = STR;
           break;

       case VAR:
           if (token) {
               PARSE_FAIL((q = strchr(p, token)) == NULL);
           } else {
               q = p;
               while (*q && !isspace(*q))
                   ++q;
           }
           tmp = *q;
           *q = '\0';
           if ((val = variable_lookup(p)) != NULL) {
               size_t len = strlen(val);

               strncpy(buf + i, val, PARSE_BUFSIZE - (i + 1));
               i += uimin(len, PARSE_BUFSIZE - 1);
           }
           *q = tmp;   /* restore value */
           p = q + (token ? 1 : 0);
           state = STR;
           break;
       }
   }
   /* If at end of token, add it */
   if (i && state == STR) {
       buf[i] = '\0';
       PARSE_FAIL(insert(&ac, buf));
   }
   args[ac] = NULL;
   *argc = ac;
   *argv = (char **)alloc((sizeof(char *) * ac + 1));
   memcpy(*argv, args, sizeof(char *) * ac + 1);
   free(buf);
   free(copy);
   return 0;
}

#define MAXARGS 20

/* Clean vector space */
static void
clean(void)
{
   int         i;

   for (i = 0; i < MAXARGS; i++) {
       if (args[i] != NULL) {
           free(args[i]);
           args[i] = NULL;
       }
   }
}

static int
insert(int *argcp, char *buf)
{
   if (*argcp >= MAXARGS)
       return 1;
   args[(*argcp)++] = strdup(buf);
   return 0;
}

static char *
variable_lookup(char *name)
{
   /* XXX search "special variable" space first? */
   return (char *)getenv(name);
}