#include <unistd.h>
#include <stdlib.h>
#include <ctype.h>
#include <time.h>
#include "extern.h"
#include "byte.h"
#include "str.h"
#include "stralloc.h"
#include "fmt.h"
#include "open.h"

/*
 * varsub
 *
 * Substitute backslash and variable strings in the source string,
 * returning the string with substitutions.  If a variable
 * substitution fails, the variable name is added to the text.
 */

/*
 * Escaping and unescaping of text.  Supported sequences are
 * 	\r	carriage return
 * 	\a	bell
 * 	\n	new line
 * 	\t	tab
 * 	\xHH	hexidecimal sequence
 * 	\d
 * 	\dd	Octal digits
 * 	\ddd
 */

static int
unescape(char *p, int max, char *result)
{
    char ch;
    int n;

    if (max <= 0)
	return 0;
    ch = *p++;
    if ((n = byte_chr("rant", 4, ch)) < 4) {
	*result = "\r\a\n\t"[n];
	return 1;
    }
    if (ch == 'x' && max > 2 && isxdigit(p[0]) && isxdigit(p[1])) {
	char hex = 0;
	ch = *p++;
	hex =	((ch <= '9' ? (ch - '0') :
		 (ch <= 'F') ? (ch - 'A' + 10) :
		 (ch - 'a' + 10)) << 4);
	ch = *p++;
	hex +=	((ch <= '9') ? (ch - '0') :
		 (ch <= 'F') ? (ch - 'A' + 10) :
		 (ch - 'a' + 10));
	*result = hex;
	return 3;
    }
    if (ch >= '0' && ch <= '7') {
	char octal = (ch - '0');
	for (n = 1; n < 3 && n < max; ++n) {
	    ch = *p++;
	    if (ch < '0' || ch > '7') break;
	    octal <<= 3;
	    octal += (ch - '0');
	}
	*result = octal;
	return n;
    }
    *result = ch;
    return 1;
}

static stralloc new, varname;

void
varsub(stralloc *sa, char **argv)
{
    char	*p, *r, **s, delim;
    int		n, cnt;
    char 	buf[512], ch;
    static int	seeded;


    if (!seeded) {
	srandom(getpid());
	seeded = 1;
    }
    p = sa->s;
    cnt = 0;
    if (!stralloc_copys(&new, "")) nomem();
    while (cnt < sa->len) {
	ch = p[cnt];
	++cnt;
	if (ch == '$') {
	    delim = 0;
	    n = cnt - 1;
	    if (p[cnt] == '{') {
		delim = '}';
		++cnt;
	    }
	    if (!stralloc_copys(&varname, "")) nomem();
	    while (cnt != sa->len) {
		ch = p[cnt];
		if (ch == delim) ++cnt;
		if (!isalnum(ch)) break;
		++cnt;
		if (!stralloc_append(&varname, &ch)) nomem();
	    }
	    if (!stralloc_0(&varname)) nomem();
	    r = NULL;
	    for (s = argv; s && *s; s += 2)
		if (byte_diff(varname.s, varname.len, *s) == 0) {
		    r = s[1];
		    break;
		}
	    if (!r && (!delim || ch == delim) && (r = getenv(varname.s)) == NULL) {
		*buf = 0;
		if (byte_diff(varname.s, 3, "ME") == 0) {
		    int fd;
		    char *me = "/var/qmail/control/me";

		    if (((fd = open_read(me + 11)) >= 0) || ((fd = open_read(me)) >= 0)) {
			if ((n = read(fd, buf, sizeof(buf) - 1)) > 0) {
			    buf[n] = 0;
			    buf[str_chr(buf, '\n')] = 0;
			    buf[str_chr(buf, '\r')] = 0;
			} else buf[0] = 0;
			close(fd);
		    }
		} else if (byte_diff(varname.s, 4, "PID") == 0) {
		    buf[fmt_uint(buf, getpid())] = 0;
		} else if (byte_diff(varname.s, 8, "SECONDS") == 0) {
		    buf[fmt_ulong(buf, time(0))] = 0;
		} else if (byte_diff(varname.s, 7, "RANDOM") == 0) {
		    buf[fmt_ulong(buf, random())] = 0;
		} else if (byte_diff(varname.s, 5, "DATE") == 0) {
		    struct tm *tm;
		    time_t now;
		    time(&now);
		    if ((r = getenv("DATEFMT")) == NULL)
			r = "%a, %d %b %Y %H:%M:%S %z";
		    if ((tm = localtime(&now)) != NULL)
			if ((n = strftime(buf, sizeof(buf), r, tm)) <= 0)
			    *buf = 0;
		}
		r = *buf ? buf : NULL;
	    }
	    if (r) {
		if (!stralloc_cats(&new, r)) nomem();
	    } else
		if (!stralloc_catb(&new, p + n, cnt - n)) nomem();
	    continue;
	}
	if (ch == '\\')
	    cnt += unescape(p + cnt, sa->len - cnt, &ch);
	if (!stralloc_append(&new, &ch)) nomem();
    }
    if (!stralloc_copyb(sa, new.s, new.len)) nomem();
}