/*
 * The function implemented in this module extracts the tag
 * from the To header of a SIP destination server's response.
 */

#include <ctype.h>
#include <string.h>
#include <strings.h>
#include <stdio.h>
#include <stdlib.h>
#include "parse.h"

extern char *get_single_header();

char *
extract_to_tag(msg, expect_uri)
	struct sip_pkt_rx *msg;
	char *expect_uri;
{
	char *cp, *tag;
	int bracketed, c;
	unsigned expect_uri_len;

	cp = get_single_header(msg, "To", "t", (int *) 0);
	if (!cp)
		return 0;
	if (*cp == '<') {
		cp++;
		bracketed = 1;
	} else
		bracketed = 0;
	expect_uri_len = strlen(expect_uri);
	if (strncasecmp(cp, expect_uri, expect_uri_len))
		return 0;
	cp += expect_uri_len;
	if (bracketed) {
		if (*cp++ != '>')
			return 0;
	}
	while (isspace(*cp))
		cp++;
	if (*cp++ != ';')
		return 0;
	while (isspace(*cp))
		cp++;
	if (strncasecmp(cp, "tag", 3))
		return 0;
	cp += 3;
	while (isspace(*cp))
		cp++;
	if (*cp++ != '=')
		return 0;
	while (isspace(*cp))
		cp++;
	tag = cp;
	for (; c = *cp; cp++) {
		switch (c) {
		case '-':
		case '.':
		case '!':
		case '%':
		case '*':
		case '_':
		case '+':
		case '`':
		case '\'':
		case '~':
			continue;
		default:
			if (isalnum(c))
				continue;
			return 0;
		}
	}
	return tag;
}