/*-
 * 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 <stand.h>
#include <string.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 == '\'');
}

static int
isdquote(int ch)
{

        return (ch == '"');
}

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

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

        /* Initialize vector and state */
        clean();
        state = STR;
        buf = (char *)malloc(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;
                                if (dquote) { /* keep quote */
                                        PARSE_FAIL(i == (PARSE_BUFSIZE - 1));
                                        buf[i++] = *p++;
                                } else
                                        ++p;
                        } else if (isdquote(*p)) {
                                dquote = dquote ? 0 : *p;
                                if (quote) { /* keep dquote */
                                        PARSE_FAIL(i == (PARSE_BUFSIZE - 1));
                                        buf[i++] = *p++;
                                } else
                                        ++p;
                        } else if (isspace(*p) && !quote && !dquote) {
                                state = WHITE;
                                if (i) {
                                        buf[i] = '\0';
                                        PARSE_FAIL(insert(&ac, buf));
                                        i = 0;
                                }
                                ++p;
                        } else if (*p == '$' && !quote) {
                                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 += min(len, PARSE_BUFSIZE - 1);
                        }
                        *q = tmp;       /* restore value */
                        p = q + (token ? 1 : 0);
                        state = STR;
                        break;
                }
        }
        /* missing terminating ' or " */
        PARSE_FAIL(quote || dquote);
        /* 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 **)malloc((sizeof(char *) * ac + 1));
        bcopy(args, *argv, 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);
}