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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: head.c,v 1.11 2009/10/27 23:59:40 deraadt Exp $	*/
/*	$NetBSD: head.c,v 1.6 1996/12/28 07:11:03 tls Exp $	*/

/*
 * Copyright (c) 1980, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "rcv.h"
#include "extern.h"

/*
 * Mail -- a mail program
 *
 * Routines for processing and detecting headlines.
 */

/*
 * See if the passed line buffer is a mail header.
 * Return true if yes.  Note the extreme pains to
 * accommodate all funny formats.
 */
int
ishead(char *linebuf)
{
	char *cp;
	struct headline hl;
	char parbuf[BUFSIZ];

	cp = linebuf;
	if (*cp++ != 'F' || *cp++ != 'r' || *cp++ != 'o' || *cp++ != 'm' ||
	    *cp++ != ' ')
		return(0);
	parse(linebuf, &hl, parbuf);
	if (hl.l_from == NULL || hl.l_date == NULL) {
		fail(linebuf, "No from or date field");
		return(0);
	}
	if (!isdate(hl.l_date)) {
		fail(linebuf, "Date field not legal date");
		return(0);
	}
	/*
	 * I guess we got it!
	 */
	return(1);
}

/*ARGSUSED*/
void
fail(char *linebuf, char *reason)
{

	/*
	if (value("debug") == NULL)
		return;
	fprintf(stderr, "\"%s\"\nnot a header because %s\n", linebuf, reason);
	*/
}

/*
 * Split a headline into its useful components.
 * Copy the line into dynamic string space, then set
 * pointers into the copied line in the passed headline
 * structure.  Actually, it scans.
 */
void
parse(char *line, struct headline *hl, char *pbuf)
{
	char *cp, *sp;
	char word[LINESIZE];

	hl->l_from = NULL;
	hl->l_tty = NULL;
	hl->l_date = NULL;
	cp = line;
	sp = pbuf;
	/*
	 * Skip over "From" first.
	 */
	cp = nextword(cp, word);
	cp = nextword(cp, word);
	if (*word)
		hl->l_from = copyin(word, &sp);
	if (cp != NULL && strncmp(cp, "tty", 3) == 0) {
		cp = nextword(cp, word);
		hl->l_tty = copyin(word, &sp);
	}
	if (cp != NULL)
		hl->l_date = copyin(cp, &sp);
}

/*
 * Copy the string on the left into the string on the right
 * and bump the right (reference) string pointer by the length.
 * Thus, dynamically allocate space in the right string, copying
 * the left string into it.
 */
char *
copyin(char *src, char **space)
{
	char *cp, *top;

	top = cp = *space;
	while ((*cp++ = *src++) != '\0')
		;
	*space = cp;
	return(top);
}

/*
 * Test to see if the passed string is a ctime(3) generated
 * date string as documented in the manual.  The template
 * below is used as the criterion of correctness.
 * Also, we check for a possible trailing time zone using
 * the tmztype template.
 */

/*
 * 'A'	An upper case char
 * 'a'	A lower case char
 * ' '	A space
 * '0'	A digit
 * 'O'	A digit or space
 * 'p'	A punctuation char
 * 'P'	A punctuation char or space
 * ':'	A colon
 * 'N'	A new line
 */

/*
 * Yuck.  If the mail file is created by Sys V (Solaris),
 * there are no seconds in the time...
 */

/*
 * If the mail is created by another program such as imapd, it might
 * have timezone as <-|+>nnnn (-0800 for instance) at the end.
 */

static char *date_formats[] = {
	"Aaa Aaa O0 00:00:00 0000",	   /* Mon Jan 01 23:59:59 2001 */
	"Aaa Aaa O0 00:00:00 AAA 0000",	   /* Mon Jan 01 23:59:59 PST 2001 */
	"Aaa Aaa O0 00:00:00 0000 p0000",  /* Mon Jan 01 23:59:59 2001 -0800 */
	"Aaa Aaa O0 00:00 0000",	   /* Mon Jan 01 23:59 2001 */
	"Aaa Aaa O0 00:00 AAA 0000",	   /* Mon Jan 01 23:59 PST 2001 */
	"Aaa Aaa O0 00:00 0000 p0000",	   /* Mon Jan 01 23:59 2001 -0800 */
	""
};

int
isdate(char *date)
{
	int i;

	for(i = 0; *date_formats[i]; i++) {
		if (cmatch(date, date_formats[i]))
			return 1;
	}
	return 0;
}

/*
 * Match the given string (cp) against the given template (tp).
 * Return 1 if they match, 0 if they don't
 */
int
cmatch(char *cp, char *tp)
{

	while (*cp && *tp)
		switch (*tp++) {
		case 'a':
			if (!islower(*cp++))
				return(0);
			break;
		case 'A':
			if (!isupper(*cp++))
				return(0);
			break;
		case ' ':
			if (*cp++ != ' ')
				return(0);
			break;
		case '0':
			if (!isdigit(*cp++))
				return(0);
			break;
		case 'O':
			if (*cp != ' ' && !isdigit(*cp))
				return(0);
			cp++;
			break;
		case 'p':
			if (!ispunct(*cp++))
				return(0);
			break;
		case 'P':
			if (*cp != ' ' && !ispunct(*cp))
				return(0);
			cp++;
			break;
		case ':':
			if (*cp++ != ':')
				return(0);
			break;
		case 'N':
			if (*cp++ != '\n')
				return(0);
			break;
		}
	if (*cp || *tp)
		return(0);
	return(1);
}

/*
 * Collect a liberal (space, tab delimited) word into the word buffer
 * passed.  Also, return a pointer to the next word following that,
 * or NULL if none follow.
 */
char *
nextword(char *wp, char *wbuf)
{
	int c;

	if (wp == NULL) {
		*wbuf = 0;
		return(NULL);
	}
	while ((c = *wp++) && c != ' ' && c != '\t') {
		*wbuf++ = c;
		if (c == '"') {
 			while ((c = *wp++) && c != '"')
 				*wbuf++ = c;
 			if (c == '"')
 				*wbuf++ = c;
			else
				wp--;
 		}
	}
	*wbuf = '\0';
	for (; c == ' ' || c == '\t'; c = *wp++)
		;
	if (c == 0)
		return(NULL);
	return(wp - 1);
}