#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>

#define BUFSIZE		8192

int main(int ac, char *av[])
{
	int	fd;
	char	*iaddr, cmd[100];
	char	*filename;

iaddr = getenv("REMOTE_ADDR");
	if (convert_html(av[1]) == 0) {
	    fprintf(stdout, "Your empty message from '%s' "
				"has not been delivered.", iaddr);
	    exit(1);
	}
	if (has_email(av[1]) == 0) {
	    fprintf(stdout, "Your message from '%s', "
		"without an email address, has not been delivered.", iaddr);
	    exit(1);
	}
	filename = tempnam("/tmp", "MAILW");
	fd = open(filename, O_RDWR|O_CREAT|O_TRUNC, 0644);
	write(fd, av[1], strlen(av[1]));
	close (fd);
	sprintf(cmd, "Mail johna -s 'web form' <%s\n", filename);
	system(cmd);
	unlink(filename);
	fprintf(stdout, "Your message has been delivered.");
}
uint tobin(char c)
{
	if ((c >= '0') && (c <= '9'))
	    return c - '0';
	c = toupper(c);
	return c - 'A' + 10;
}
int convert_html(char *str)
{
	int	chars=0;
	char	*p, *q;
	uint	x;
	
	p = &str[5];					// skip over 'body='
	q = str;
	while (*p) {
	    chars++;
	    switch (*p) {
		case '%':
		    x = (tobin(p[1]) << 4) |  tobin(p[2]);
		    *q++ = x;
		    p += 3;
		    break;
		case '+':
		    *q++ = ' ';
		    p++;
		    break;
		default:
		    *q++ = *p++;
		    break;
	    }
	}
	*q = 0;
	return chars;
}
int has_email(char *str)
{
	char *p, *q;

	p = strchr(str, '@');
	if ((p == NULL) || (p == str))
	    return 0;
	q = strchr(p++, '.'); 
	if ((q == NULL) || (q == p))
	    return 0;
	return 1;			// valid email?  (x@y.z)
}